DOI: 10.2478/frp-2020-0006 Wersja PDF: www.lesne-prace-badawcze.pl Leśne Prace Badawcze / Forest Research Papers Czerwiec / June 2020, Vol. 81 (2): 51–64 original research article e-ISSN 2082-8926 Comparing methods for assessing the health of regeneration in Scots pine culture Zbigniew Sierota1* , Monika Małecka1, Marta Damszel2 1 Forest Research Institute, Department of Forest Protection, Sękocin Stary, ul. Braci Leśnej 3, 05–090 Raszyn, Poland; University of Warmia and Mazury in Olsztyn, Faculty of Biotechnology and Biotechnology, Department of Entomology, Phytopathology and Molecular Diagnostics, ul. Prawocheńskiego 17, 10-721 Olsztyn, Poland 2 Tel. +48 22 7153824, e-mail: z.sierota@ibles.waw.pl Abstract. This study’s aim was to describe the health condition of Scots pine cultures of up to 10 years old using and comparing various field assessment methods. Since forest districts report on the health of stands annually, we assumed that for a proper health analysis it is necessary to develop a simple and yet reliable assessment method that allows for determining the share of fungal pathogen infection in the stand (both foliar and root pathogens) and their differentiation from symptoms of abiotic factors such as drought. Six different methods of health assessment were tested in selected Forest Districts across Poland. We found that the most reliable assessment of the health condition of young stands is obtained with the surface method ‘MF’ (phytopathological monitoring method) and the linear ‘Z’ method, which uses transects of 30 meters in three rows in the shape of the letter Z. Keywords: Phytopathological monitoring, Scots pine cultures, field assessment, health status, pathogens 1. Introduction and rationale for the work The current assessment of health and sanitary condition of the forest is one of the important sections of the annual report on the state of the forest (raport 2018), sent to state, local government and scientific units, as well asto publicly available websites. The assessment is a synthesis of information collected annually in the field and sent by forest districts to Forest Protection teams (Zespoły Ochrony Lasu – Zol), Regional Directorates of State Forests (RDSF), and after verification – to the General Directorate of State Forests (DGLP) and the Forest Research Institute (IBL), produced asthe ‘Shortterm forecasts of the occurrence of harmful forest insects and infectious diseases’ (Krótkoterminowa 2019). Such an assessment contains not only data on factors predisposing or initiating certain phenomena or disturbances in the stands, but also information on the temporal and spatial changes of the extent of the occurrence of selected insects and fungi in Poland. it is also an attempt to infer and predict the consequences of current and predicted threats. For such information to be credible – as it usually is the basis for making important decisions of both an ad hoc and strategic nature – it must be received: 4.02.2020 r., accepted after revision: 5.03.2020 r. © 2020 Z. sierota et al. based on methodological foundations that ensure repeatability, verification and the value of the data for knowledge. These requirements were indicated by the State Forests Research Institute as early as 1935, and their importance resulted from many premises, based on the annual (since 1931) Disease Prevalence Questionnaire together with the Forest Diseases Table overview (Orłoś 1935). The reliability of the data should result from its authors and therefore from the declared responsibility of the contractor for the reliability of the information obtained on the basis of a verified methodology. It is in this context that considerations are presented here on the process of obtaining information about the health condition of the forest, and more closely – about the health condition of crops in renewals and afforestation. the intention of the authors is to indicate the potential and actual conditions shaping the health condition of crops, which are usually not taken into account in their assessment. They occur in places that are difficult or even inaccessible to observe directly, have a non-specific nature, or encourage easy simplification and a certain formulaic approach. An illustration of such information is the data contained in the reports on the occurrence of annosus root rot in tree stands, on 52 Z. Sierota et al. / Leśne Prace Badawcze, 2020, Vol. 81 (2): 51–64 the example of three forest districts, presented by the authors in forestry journals (Sierota, Małecka 2018; Sierota 2019). The official data from various assessment periods indicate the difficulties in assessing changes in the area that is threatened – a decrease from 1,700 ha to 300 ha, an increase of 1,300 ha in the next period, and then a decrease in the reported area to zero (Sierota 2019). Where do such discrepancies come from? The interpretation of the described situation, which after all, affects the overall picture of the threats and economic decisions made in the assessment year, requires the clarification of several facts that may have occurred individually or jointly in a given year. The assessment contractor may have lacked knowledge about the disease cycle, the stand could have entered a different age class and become subject to a different reporting protocol (up to vs. over 20 years of age), the age of the assessed trees could have indicated different phases of the current growth rate, felling or the reconstruction of species composition may have been undertaken in the infected stands – and assessed as ‘no existing threat’, there may have been a change in the assessment contractor who lacked knowledge about the site, a local drought may have occurred causing the foliage to start browning, and finally – the given assessment was performed during the period when the methodology of the most recent editions of the Forest Protection instructions (Instrukcja Ochrony Lasu – iol) changed four times. It follows that there are many reasons for the weaknesses in visually assessing stand health in terms of fungal pathogens, and especially of root pathogens – the perpetrators of annosus root rot and Armillaria root rot. Annosus root rot is a dangerous tree disease caused by pathogenic fungi of the genus Heterobasidion, occurring especially in afforestation on former agricultural land (caused by H. annosum (Fr.) Bref.) and in spruce trees (caused by H. parviporum Niemelä & Korhonen) (Sierota 2001). The method of infection with the above mentioned pathogens is hidden because it is initiated by basidiospores and conidiospores germinating in tree roots, on the surface of vertical wounds (damage to the root collar of trees) or horizontal wounds (stumps after tree felling) and forming mycelium. By releasing the enzymes required for taking up nutrients, mycelium blocks the natural and induced tree defences and causes the breakdown of wood cells. The tree – depending on its species, age, genetically determined defensive abilities, as well as the aggressiveness of the pathogen – dies within a shorter (young trees, especially pine, larch, birch) or longer time (older trees, especially spruce). Dieback is visible in the first phase by the reduced turgor of shoots and leaves/needles, decreasing or disappearing current height and thickness increments, followed by a change in crown colour (decreased density, rusting, browning), premature leaf/needle fall, and finally by dying cambium and phloem and then the whole tree. The pathogen produces fruiting bodies on the root collar or inju- red roots, which are perennial and produce basidiospores over a long period, causing further infections. At the same time, when the roots of the infected (diseased) tree touch or grow together with the roots of healthy, hitherto uninfected trees, secondary infections occur, in which the pathogen’s mycelium grows over the contacting roots and extends the infection. Disease outbreaks arise, spreading from year to year (Żółciak et al. 2006). Knowledge of the developmental cycle of the pathogen is essential for understanding the nature of the threat posed by infected roots remaining in the soil. According to numerous sources (Greig, Pratt 1976; Stenlid 1987; Piri 1996), the mycelium of Heterobasidion pathogens can remain in the soil, in the heartwood of the roots, for decades (even over 60 years) maintaining full biological activity. It is a real source of secondary infections for successive trees in a given stand, as well as for successive generations of the forest in that area – both for natural and artificial regeneration. In this context, the above mentioned reporting data from Forest District A on the absence of a pathogenic threat becomes quite unreliable. The methodology for assessing the health status of trees and stands is found in the official document ‘Forest Protection Instructions” (IOL), which was previously approved by the Minister for Forests and is now annexed to Directive No. 57 of the Director-General of the State Forests of 2011. Several IOLs have been published so far, the first in 1954, the next ones in 1960, 1972, 1988, 1995 (reprint), 1999, 2004 and the most recent one, currently in force, in 2012. One of its chapters consists of instructions for controlling damage caused by pathogenic fungi and other disease-causing factors, as well as damage caused by abiotic factors. Successive editions contained different thresholds of the harmfulness of pathogens, serving as the determinant for required reporting on threats or damage. For example, in the 1999 IOL, root pathogens were reported after having exceeded 5% of the number of infected trees or area of gaps in the stand. In the 2004 and 2012 IOLs, on the other hand, healthy stands were considered to be those in which the proportion of infected trees did not exceed 10% of the total number of affected trees or gap areas and could therefore be, for example, 9.5%. Is this a healthy stand? the Forest Protection instructions of 2004, in the section on ‘Mandatory actions’ II.3 (§67–80) and – unfortunately – ‘Non-mandatory actions’, part III.A.2 (§177–185), contained the methodological basis for site indexing the degree of tree infestation and assessing the threat to the stands. The data obtained allowed a spatial visualization to be obtained of the severity of the disease in the Forest Numerical Map (Leśna Mapa Numeryczna – LMN). However, this capability was not used sufficiently, and the apparent difficulty of making such an assessment, even if only once, probably led to the simplification of the methodology. The current IOL from 2012 (Part III/B/6.1.8.1; Part IIB, p.2, §99, 101) contains simplified assess- Z. Sierota et al. / Leśne Prace Badawcze, 2020, Vol. 81 (2): 51–64 ment formulas, which, according to the authors, do not reflect the essence of the specificity of the development of infectious diseases, focusing primarily on assessing the threat from insects. The risk to stands from pathogens is defined as weak with 5–10% of the trees assessed as diseased and/or dead, medium at 11–30% and catastrophic at over 30%. This assessment is used to develop a recovery program and to select appropriate intervention measures (section 4 §6.1.8.1). Reporting the level of damage and danger to trees in the crop (Part II/B/2, §95- 104) in Form 4 takes place when the number of infested and dead trees exceeds 10%, at least 3 disease outbreaks have been identified or when the total gap area exceeds 10% of the stand (§101). There are no precise explanations for determining the symptoms of the disease (e.g. recognition of etiological signs) and differentiating the threat, for example with the symptoms of drought or frost, end so on. So does Form 1 (the Signal sheet) provide new or additional information about the current state of the forest? The question arises of whether the arbitrarily set boundaries reflect the current state of health? Or maybe they only inform about the area of the specific symptoms observed visually, not the etiological signs of the causative agents? Do they allow the infectious potential and the probable direction of the stand’s development to be determined in a given area? Do they support the decision-making process regarding the intensity and recurrence of intermediate cutting, salvage cutting, or finally, the type of harvesting used and the scope of implementing prophylactic and therapeutic methods? The methodology developed by IBL (Sierota, Lech 1996), called phytopathological monitoring (monitoring fitopatologiczny – MF), adapted from the method originally used in the United States of America (Lech 2000; Woodall et al. 2011), should be mentioned here. It assessed trees in four circular measurement plots of specific dimensions, where the zero plot was located at a randomly selected GPS-marked point in the stand (Sierota, Lech 1996, 1997, 1998; Sierota 1997a,b; Sierota et al. 1999). In addition to assessing the tree, stump condition was also assessed, which was new for monitoring studies (Sierota 1998), and later used in subsequent methodologies for the Large-scale Inventory of the State of the Forest (Wielkoobszarowa Inwentaryzacja Stanu Lasu − WISL) methodology (Michalak et al. 2004, 2010; Jabłoński et al. 2014). The MF method was successfully tested by Forest Protection Teams and implemented in the State Forests in 1996−2004, becoming the basis for several forest health assessments (Sierota, Lech 1999; Lech, Żółciak 2006). The monitoring indicators developed by Sierota and Lech (10 in total) allowed many aspects of the stand assessment to be interpreted – economic (assessment of the intensity of cleaning and thinning, backlog of treatments, stand spacing), phytopathological (presence of pathogens, saprotrophs, share of infected trees and stumps), as well as ecological (exposure of stumps to infections, presence of wood decomposing fungi, 53 threat to the stand). However, the method has not been implemented and is performed only occasionally in health assessments (Lech, Sierota 1999; Małecka, Sierota 2000). According to the authors, it is still an excellent tool for monitoring the health status of stands at the level of the forest district – it ensures the repeatability of the assessment, is reliable and can be performed only once every 10 years, for example. This method and other monitoring assessments (Sierota et al. 2000) were described in detail by Sierota et al. (2017). Phytopathological assessments of the health condition of crops have been performed by many authors – in the 1992 post -fire area studies (Sierota, Małecka 1997; Hawryś et al. 2004), in monitoring the threat of pine twist rust (Małecka 2008), in assessments of pine root diseases (Łakomy 1998; Mańka, Janczyk 2000; Szewczyk, Mańka 2002; Szewczyk 2014), and in analyses of the mycorrhizal status of pines in post-agricultural soil (Małecka, Hilszczańska 2015). This paper is a further methodological development of IBL's assessment of the health status of trees cultivated for several years. Knowledge about the current state of the health of the crop is an essential source of information on the future of the next development phases of the stand. It can determine specific economic activities in silviculture and forest protection, as well as check forest management plans directing the performance of future intermediate cuttings, harvesting volume or type of felling. the data used in this paper are the result of selected assessments and field measurements performed at IBL and by engineering students from the University of Warmia and Mazury in Olsztyn in several forest districts in Poland. They were conducted on pine crops, as this species dominates in the area being regenerated. A hypothesis was posed that the result of the assessment, that is the share of particular stress factors or so-called damage-producing factors shaping the health condition of the crop and assessed on the basis of a visual assessment, is not unequivocal. it depends on the assessment method and is determined by external causative (pathogens, insects) and environmental factors (age of the crop, occupied habitat, presence of stumps in the area). This paper presents selected results of the measurements taken of specific crops, as well as for easier interpretation and visualization – averaged assessment results for all crops in a given forest district. They were referenced to the entries of the current IOL in force to illustrate the degree of agreement between the data obtained using different assessment methods. 2. Materials and methods The measurements were conducted in different years in the selected forest districts (Table 1), where Pinus sylvestris l. is artificially regenerated with seedlings from both open nurseries and container production, and naturally regenerated. Z. Sierota et al. / Leśne Prace Badawcze, 2020, Vol. 81 (2): 51–64 54 Table 1. Characteristics of measurement areas and used assessment variants Site type/No of cultures MF t100 Z 3x33+1 10 po 10 Measurement, year of assessment Rudy Raciborskie Ruda Kozielska, Borowiec BMśw/4 - - - + - M. Małecka, 1997 Myszyniec, Warmiak, Rudne BMśw/6 + - - - - I. Miller, 2016 Potrzebowice Dziewanna, Osina Bśw/3 - + - + - M. Małecka, 1999 BMśw/2; Bśw/2 + + - - - P. Bogumił, 2017 Miłomłyn-1, Bagieńsko BMśw/2 + - - + - r. Fil, 2015 Miłomłyn-2, Kaczory, Borsuki, Sarni Dół LMśw/4 + + + - - M. Krzaczek, 2017 Olsztyn Kośno BMśw/2 - - + + + J. Dębek, M. Damszel, 2019 Forest District, Forest Subdistrict Spychowo Variant of assessment Bśw – coniferous fresh site, BMśw – mixed coniferous fresh site, LMśw – mixed deciduous fresh site Crops of similar age were selected for the assessment, planted after preparing the soil with a forest plough and identically spaced, or from self-seeding, in areas representing one or two forest habitat types (Table 1). this paper presents the results of research on selected groups of diseases reported in accordance with the current IOL, using one, two or three methods, from among the following (Fig. 1a-f): a) The phytopathological monitoring method ‘MF’ (Sierota, Lech 1996), modified, was used in 4 measurement plots and consisted of the random selection of the centre of plot 0, located at least 20 m from the outermost row of trees in the crop, delineating a circle with a 5.65 m radius and the selection of three consecutive plots of the same dimensions 20 m from the centre of plot 0 in the directions of 0°, 120° and 240°; the total measurement area of the 4 plots was 100 m2. b)The linear or strip transect method ‘TL100’ consisted of the random selection of one row of trees in the crop, located about 1/3 of the distance from the edge of the crop’s width and marking out a strip 100 LM long and 1 m wide (Cieślak 2000); the measurement area of the transect was 100 m2. c) The ‘10 by 10’ method, used in Sierota et al. (2000) and Hawrys et al. (2004), consisted of assessing the trees in 10 randomly selected rows, each 10 LM long; the first measurement row was 3–4 rows away from the crop’s edge, and the subsequent ones were also 2–3 rows away from each other, depending on the width of the crop; the total measurement area of the strips was 100 m2. d) The ‘3x33+1’ method consisted of delineating three transects with lengths of 33, 33 and 34 LM respectively and a width of 1 m at a randomly selected location in the crop, 3–4 rows away from its edge. The transects were 5–6 rows of trees away from each other, covering the largest possible cultivated area (modification of method c); the total measurement area of the strips was 100 m2; e) The ‘10×10’ method consisted of delineating 2–3 10×10 m plots in randomly selected locations in the crop, at least 3 rows of trees from its edge; the measurement area of one plot was 100 m2; f)The ‘Z’ method consisted of randomly selecting one crop row, 3–4 rows of trees distant from the edge of the crop and delineating the first strip with a length of 33 LM and width of 1 m, then delineating a second strip with a length of 34 LM and width of 1 m ‘diagonally’ across the rows (modification of method d) and then delineating a third strip with a length of 33 LM and width of 1 m at least 5–6 rows of trees away from the first strip; the total measurement area of the 3 strips was 100 m2. An assessment using each method was performed on each crop in two or three repetitions (depending on the size of the crop) in order to measure as large an area as possible; none of the plots in the crop using the specific methods overlapped spatially. Each measurement was converted to 1 ha and averaged. All the trees were assessed in each of the plots. The number of trees and the number of losses were determined up to the time of the assessment, based on the spacing of the planting. Stumps occurring within the plot assessed with the given method were also recorded. Stumps located partly on the plot (on its border) were included in the assessment. The assessment involved recording the following characteristics of each of the assessed trees: Z. Sierota et al. / Leśne Prace Badawcze, 2020, Vol. 81 (2): 51–64 55 Figure 2. An example of a tree rated on the needle discoloration scale 3 and with symptoms of Armillaria root rot – the picture does not show the rhizomorphs in the root neck (photo M. Krzaczek) Figure 1. Diagram of the location of measurement plots in the plantation – the degree of needle discoloration (and/or crown thinning) on a scale of 0 – no change; 1 – discoloration/thinning to 30%; 2 – discoloration/thinning to 60%; 3 – discoloration/thinning over 60%; 4 – dead, no needles (Fig. 2); – etiological signs of pathogens: 1 – assimilation apparatus and/or shoots; 2 – root systems after uprooting the tree and eventualroot deformation; the assessment used a key to identify the infectious diseases of forest trees (Sierota, Szczepkowski 2014); – signs of feeding and/or damage caused by insects, if any; – signs of foraging by wildlife, unless the area was thoroughly fenced; – etiological signs of fungi (mycelia, fruiting bodies, rhizomorphs) and symptoms of root wood decomposition on stumps. The results obtained for each repetition of the measurement plot were added together, averages were calculated and then converted into 1 ha. For assessing the averages for the methods, habitats or plots (crops, forest districts), the chi -square and NIRanoVa tests were used after first normalizing the distribution with log10. For selected crops, an inoculum density index (GI) was calculated, which is the quotient of the number of trees in the plot to the number of stumps; this index indirectly determines the degree of threat to the root systems of trees located in the vicinity of the roots of one stump (GI=Ndrzew/npniaków). For the purpose of this paper, the results were omitted on assessed tree damage caused by insects and animals, which was also recorded during the measurements in accordance with the proposed methods. 3. Results 3.1. Comparison of the condition of same-age crops assessed with one method 3.1.1. Assessment of the occurrence of assimilation apparatus and shoot diseases in Rudy Raciborskie Forest District The areas were located in four 4- and 5-year-old Scots pine crops in an area that had experienced a fire in 1992. The assessments performed using the ‘3x33+1’ method allowed not only the success of the regenerations to be determined in the conditions of a strongly changed soil environment, but also the pathological changes within the crown to be captured. The performed assessments indicated that the examined crops were in poor health (share of diseased trees – 54.5– 68.0%). The share of trees that had died up to the assessment period was small and was 10.1–17.0% by age (Table 2), but trees lacking any pathological symptoms only amounted to 56 Table 2. Share [%] of trees with etiological signs or other disease symptoms share of trees on the transects studied [%] Age [years] without symptoms lack or died trees needle cast 4 25.0 17.0 41.0 5 37.0 10.1 38.0 25.0–37.0% respectively. The main causes of needle discoloration and drop were the pathogens causing pine needle cast (38.0–41.0%, respectively) and to a small extent, pine twist rust (6.4–10.0%). The occurrence of root pathogens at this age was not expected, not only due to the significant destruction of the inoculum (infected roots of burnt trees), but also due to the lack of secondary infections in the case of contact between the roots of the cultivated trees and the deeper roots of the previous generation. In the light of the IOL (2012), these crops should be qualified as very heavily infected. 3.1.2. Assessment of the occurrence of pine needle cast in the Myszyniec Forest District the visual assessment of the condition of the crop focused on the threat from pine needle cast, assessed on the basis of the appearance of the tree crowns – changes in survival (fallen trees, dead trees), the presence of etiological signs of causative agents, the degree of discoloration (foliage turning pale, rusting) and needle loss. Crown discoloration was associated with the occurrence of needle cast diseases (etiological signs) and their differentiation (no etiological signs) from the changes caused by drought (lack of precipitation and insolation). Such a preliminary assessment is done on the majority of crops in Poland, is often described as a total and frequently presented in IOL form no. 4 – as pine needle cast or abiotic diseases. The assessment was performed in an area of six 4 to 5year-old pine trees, which occupy a fresh mixed coniferous forest habitat in Myszyniec Forest District (divisions 95g, 96g, 83k in the Rudne Forest Unit and divisions 17b, 16d, 23f in the Warmiak Forest Unit). Three plots had artificially regenerated crops and three were naturally regenerated. In order to differentiate the causes of problems resulting from environment factors, the crops were located both in the vicinity of stands of younger or older age classes, as well as in the close vicinity of a national road or urbanized area. The measurements were made in three repetitions on each crop, on 4 plots of phytopathological monitoring ‘MF’, each with a radius of 5.65 m. Healthy trees (75–90%) exhibiting no symptoms of needle cast (no etiological signs typical of the causative pine twist rust several diseases diseases average 10.0 7.0 68.0 6.4 8.5 54.5 agent), or changes resulting from drought (uniform crown thinning or rusting) prevailed in the studied crops. 18– 20% of the cultivated trees assessed at level 1 (changes encompass up to 30% of the needles in the crown) were characterized by some variability resulting from the location of crop in the stand, as well as the type of regeneration (natural – artificial). The proportion of this variability was reversed in the group of trees at level discoloration (representing only 3–11% of the total number of trees) –it was much higher in the artificially regenerated crops and lower in the naturally regenerated ones in the Warmiak Forest Unit(Fig. 3, left). The results of the non-parametric Chi-square test confirmed that the naturally regenerated trees were in a worse health condition in terms of the average number of trees at individual levels of discoloration than those from the artificial regeneration. However, the differences between the averages for all crops were not large, which was confirmed by the coefficient of variation V [%], which did not exceed 7% for levels 0 and 1 (Fig. 3, on the right). Reporting on the health status of the crop in relationship to pine needle cast or abiotic factors based on one averaged assessment (here as ‘crop’), albeit in this case based on an in-depth tree survey of 72 circular plots, each with an area of 100 m2, is information of a more statistical nature than factual. It does not describe the degree of the intensity of the threat (inoculum size resulting from the number of infected trees) or the degree of susceptibility of trees to other infections, resulting from the number of trees at discoloration levels 3 and 4 (e.g. root pathogens). If a routine review of the crops and their assessment according to the proposed ‘MF’ method were conducted, information would be obtained that, on average, about 27% of the 4–5 year-old trees in the crops occupying the described habitat show symptoms of needle cast. According to §96 of the IOL, the area of this crop would be attached to the report on the occurrence of diseases (>10%), but assessed as threatened to an intermediate degree (§6.1.8.1p.3). Are the ‘MF’ or ‘3x33’ transect methods credible and the only ones to propose? This question can be answered by comparing the results of the assessment variants, which is described below. 100 90 80 70 60 50 40 30 20 10 0 57 100 OS Rudne 0 OS Warmiak ON Rudne ON Warmiak 1 2 3 Degree of discoloration of the crowns 4 Udział drzew z symptomami [%] Share of trees with symptoms [%] Udział drzew z symptomami [%] Share of trees with symptoms [%] Z. Sierota et al. / Leśne Prace Badawcze, 2020, Vol. 81 (2): 51–64 90 80 70 4 3 2 1 0 60 50 40 30 20 10 0 Rudne Warmiak OS Rudne Warmiak ON uprawy Figure 3. Share [%] of trees in artificial regeneration (OS) and natural regeneration (ON) cultures in. Rudne and Warmiak Forest Units – according to the degree of crown discoloration (left) and the cumulative share and value of the coefficient of variation V [%] for all crops (right) 3.2. Comparison of the condition of crops assessed with two methods 3.2.1. Assessment of the occurrence of pine twist rust in the Potrzebowice Forest District the assessment was performed on three 5 year-old crops located in fresh coniferous habitat that was affected by a fire in 1992. The analysis used the linear transect method ‘T100’ and three shorter transects ‘3x33+1’ in the same areas. Due to the widespread occurrence in 1996–1997 of pine twist rust caused by the heteroecious rust fungus Melampsora populnea f. sp. pinitorqua Boerema & Verh., the extent of the occurrence of this shoot disease was assessed. In addition, attention was paid to the share of trees with proleptic shoots, deforming the crown shape. Due to very similar results obtained by both linear methods, with a coefficient of variation for individual traits not exceeding 5%, the results were averaged, assuming that in the case of this particular disease, each of the performed methods provides an analogous result. It was shown that, on average, the condition of crops in the post-fire area in the Potrzebowice Forest District was unsatisfactory. Only 41.4% of trees had what would be considered normal crown features, with no deviations (Fig. 4). The presence of the needle castfungi complex together with shoot deformations was recorded on 76.9% of the assessed trees and pine twist rust was found on 30.5% of the trees. The linear methods, with the random location of measurement transects, are easy to perform, usually work well in describing diseases whose infectious material disperses, and to a lesser extent, take into account the specificity of root diseases, whose inoculum spreads through outbreaks (clusters). According to IOL (2012), the assessment of the described disease qualifies the examined crops as very strongly threatened by pine twist rust. No symptoms 25.5 41.4 Needle cast and twisting rust Autumn needle cast Proleptic and double shoots 45.8 5.06 5.0 2.2 Proleptic shoots and pine twisting rust Proleptic shoots and spring needle cast Figure 4. Average share [%] of trees without symptoms and with shoot deforestation and needle diseases in the area of regeneration after a forest fire in Potrzebowice Forest District 3.2.2. Assessment of the occurrence of root pathogens in Spychowo Forest District The measurement plots were located in 4 crops of artificial regeneration after the removal ofa pine stand with an admixture of oak, occupying fresh mixed coniferous (105m, 117d) and fresh coniferous habitats (163h, 93Ag), each 5 years of age (Table 3). Due to the cluster character of the development of root diseases, also related to the presence of stumps in the stand, the areal ‘MF’ method was used in the assessment, while the linear transect method ‘T100’ was used for comparison, in two repetitions for each crop. The number of trees per 1 ha indicates the presence of infected trees and the scale of possible corrections and additions, whereas the percentage of pathogens and the GI indicator indicate the degree of infection of a given crop, allowing for a prognosis to be made for the given stand. Comparing the share of pathogens in the same crops (Table 3) using two different methods gave different results, which is understandable given the way the assessment is performed and the different potential threat to the trees. this is due Z. Sierota et al. / Leśne Prace Badawcze, 2020, Vol. 81 (2): 51–64 58 Table 3. The number of trees and stumps within the assessed areas, the value of the GI index and the total share [%] of pathogens Number per hectare Variant trees stumps gi index Pathogens per hectare Armillaria Heterobasidion Pathogens average [%] Phytopathological monitoring MF MF 1 7021 1630 4.3 251 251 5.8 MF 2 6394 1253 5.1 502 125 8.2 105m Average 6708 1442 4.6 376 188 6.9 MF 1 11158 627 17.8 502 125 5.3 MF 2 13666 501 27.3 251 125 2.7 117d Average 12412 564 22.0 376 125 3.9 9560 1003 9.5 376 157 5.0 MF 1 11158 376 29.7 376 125 3.9 MF 2 10281 250 41.1 376 501 8.3 163h Average 10720 313 34.2 376 313 6.2 MF 1 10281 501 20.5 502 125 5.8 MF 2 10406 626 16.6 627 376 9.1 93Ag Average 10344 564 18.3 564 251 7.5 Average per site 10532 439 24.0 470 282 6.9 MF average 10046 721 13.9 423 220 6.0 Average per site linear transect t100 t1 9600 1000 9.6 200 0 1.9 t2 9000 1200 7.5 400 300 6.8 105m Average 9300 1100 8.5 300 150 4.3 t1 14300 800 17.9 600 300 6.0 t2 12500 1200 10.4 900 100 7.3 117d Average 13400 1000 13.4 750 200 6.6 t1 13400 1000 13.4 900 500 9.7 t2 10300 1000 10.3 400 300 6.2 t100 Average per site 11350 1050 10.8 525 225 5.5 Average 11850 1000 11.9 650 400 8.2 t1 13400 1000 13.4 900 500 9.7 Z. Sierota et al. / Leśne Prace Badawcze, 2020, Vol. 81 (2): 51–64 Number per hectare 59 Pathogens per hectare Armillaria Heterobasidion Pathogens average [%] stumps t2 10300 1000 13.4 400 300 6.2 93Ag Average 11850 1000 11.9 650 400 8.2 Average per site 11850 1000 11.9 650 400 8.2 T100 average 11600 1025 11.3 588 313 6.9 Four cultures average 10823 873 12.6 506 267 6.5 to the different inoculum density (GI index) in the stump roots in the different habitats – and thus possible secondary root infections. The value of this index varied in different sites of the examined crops – from GI=4.3 for MF1 in 105m to 41.1 for MF2 in 163h, and even in the same crop – in 117d, from GI=10.4 for T2 to 17.9 for T1. The presence of root pathogens in the crop was confirmed by assessments of weakened and dead trees showing etiological signs of the causative agents and the fungi Armillaria ostoyae (romagn.) Herink and H. annosum (Table 3). On average, based on the assessments made in 2 repetitions on the 4 studied crops, both confirmed pathogens were recorded in 6.5% of the trees, but their share in the crops using both methods (MF and T100) was higher in the fresh coniferous habitat (6.9 and 8.2% respectively) than in the fresh mixed coniferous habitat (5.0 and 5.5%). The share of pathogens in the assessment of crops based on the individual methods also differed (Fig. 5). The results indicate a large spread in the assessment of the threat to the crops occupying different habitats, up to 4% (MF2 and T100 1) depending on the assessment method adopted. In averaging the result characterizing the condition of the assessed crops at the same age in Spychowo Forest Inspectorate, which simulates the reporting using the IOL (2012), it should be stated that despite the share of infected trees in one of the crops at a level of 9.6%, the average does not exceed the determined boundary of 10%. However, it does provide information about the high potential threat to future stands, especially from Armillaria root rot. 3.2.3. Assessment of the threat of disease for crops of various ages in Miłomłyn Forest District A 100 m long linear transect, even if randomly selected, gives a picture of a small fraction of the crop and does not fully inform about the actual threat of disease, so in addition to the ‘MF’ plot method, the assessment of trees in three shorter rows of 33 m each, 5–6 m apart, was used. A health analysis of trees in the category of ‘up to 20 years’ (IOL Udział patogenów korzeni [%] Share of root pathogens [%] trees gi index Variant 9 8 7 6 5 4 3 2 1 0 BMśw MF1 MF2 Bśw T100 1 T100 2 Cultures - average Figure 5. Share [%] of root pathogens together depending on the type of habitat (BMśw, Bśw) and assessment methods (MF and T100, in duplicate) and averaged rating for four crops in Spychowo Forest District 2012) was performed in the Bagieńsko Forest Unit of the Miłomłyn Forest District, to assess the health status of crops mainly aged 4 and 11 years, naturally regenerated in a fresh mixed coniferous forest habitat. The assessments performed confirm the assumption that the trees are threatened at different levels depending on the type of method used, regardless of the age of the crops being assessed. Method ‘MF’ precisely informs about occurring diseases, both of a focal character (root pathogens) and of a surface character (needle cast fungi). On the other hand, the method of shorter transects located in three nearby rows allows a certain section of the crop to be described, but also importantly – the trees adjacent to the row, enabling the direction of secondary infections and the occurrence of needle and shoot diseases to be tracked, especially at a younger age. In the case in question (Table 4), the ‘MF’ method assessment showed an average of 9.3% of infected trees and 11% (10.1% on average) using the ‘3x33+1’ method in younger crops. On the other hand, in older crops, the share of infected trees was 6.6% and 7.0% (average 6.8%), respectively. 60 3.3.2. Crops of the same age, general assessment of the trees in Olsztyn Forest District Observations of the health condition of the artificial regeneration in 4-year-old pine tree crops in Olsztyn Forest District were performed in divisions 436d and 437h, occupying a fresh mixed coniferous habitat. The trees in each of the assessed areas were analysed twice in three repetitions for each of the three adopted methods (3x33+1, 10×10, Z). The condition of needles, etiological signs on trees, the condition of the root system of damaged trees, as well as other assimilation apparatus damage resulting from biotic factors (e.g. insect feeding) affecting the general condition of trees were taken into account. Age [years] repetition 1 plot no. repetition 2 pathogens [%] transect no. pathogens [%] 0 7.0 1 12.0 1 12.1 2 5.7 2 14.7 3 12.9 3 6.1 average 9.7 0 5.1 1 13.4 2 12.0 3 7.6 average 8.8 average 11.0 9.3 0 3.7 1 3.5 4 6.1 2 0 5 8.8 3 9.3 6 6.1 average 4.2 average 7.0 repetition 3 Average cultures repetition 4 3.3.1.Crops of various ages in Miłomłyn Forest District (2) The measurement areas were located in 4 crops in the Miłomłyn Forest District (2), occupying a fresh mixed broadleaved habitat, aged 4 and 8 years respectively. Due to the fertile habitat and species composition of the previous stand, in which the share of deciduous species was significant, etiological signs of the fungus A. ostoyae, the cause of Armillaria root rot, were expected. The health assessment of the trees was performed using three methods: ‘MF’, ‘T100’ and ‘Z’. As expected, this pathogen dominated among the weakened and dead trees, reaching the number of 250 trees/ha using the ‘MF’ and ‘Z’ assessment methods, which indicates a significant scale of planned corrections and additions. in the same plots, annosus root rot was also recorded, which occurred with greater intensity using method ‘MF’ than ‘Z’. (Fig. 6). the scale of the threat to the 4 studied crops indicates a varied, despite being averaged, picture of their health condition (Fig. 7). In these age-differentiated crops, a) younger (4 years old) and b) older (8 years old), the averaged share of root pathogens did not exceed 5%, but this was differentiated locally – the highest in the older crop in division 75d, where it was 6.8% (data not presented). All the areas were dominated by Armillaria root rot. Symptoms of this disease were found on 2–4.5% of the number of trees with etiological signs, while annosus root rot was recorded on 0.9–2.3% of trees. According to the IOL methodology (2012), these crops would qualify as ‘healthy’. linear method (3x33+1) MF method 4 years 3.3. Comparison of the condition of crops assessed with three methods Table 4. Share [%] of infected trees in crops from natural regeneration assessed using the ‘MF’ method and the ‘3x33+1’ method in individual repetition of the assessment 11 years By averaging the similar results of both methods for IOL reporting (IOL 2012), a theoretical stand threat score of 8.5% – and therefore ‘no threat’ – is obtained for stands up to 20 years of age. Is this consistent with the actual condition and a good prognosis for these stands? 0 12.1 1 6.9 2 10.2 3 6.8 average Average cultures 9.0 6.6 Depending on the location of the plot and the assessment method adopted, different results of needle and root disease severity were obtained (Table 5). The lowest deviation of assessment error was obtained (coefficient of variation V=8.6%) in the analysis of the degree of infection by needle cast fungi, which indicates a fairly stable level of threat, relating more Z. Sierota et al. / Leśne Prace Badawcze, 2020, Vol. 81 (2): 51–64 the study plot. Each of the methods indicated different, dominant threats tothe particular crops, which indicates that every assessment subject should be treated individually and simplifications should be avoided (Table 5). 4. Summary In terms of the share of symptoms of crown discoloration on younger crops, a high degree of conformity of threat assessments is noted, regardless of the method used. On older crops, on the other hand, some quantitative differences among such trees were noted, depending on the assessment method – the lowest occurred when assessing with method Z and the highest with method MF. Crown discoloration, however, cannot be a reliable symptom of health condition without indicating the most probable cause. Crown rusting Udział drzew z patogenami korzeni [%] Share of trees with root pathogens [%] Liczba drzew z patogenami Number of trees with pathogens to the size of the fungus’s inoculum and the susceptibility of the trees than to the adopted assessment method. Significant differentiation in the assessment depending on the adopted method was obtained in the analysis of the occurrence of root pathogens H. annosum and A. ostoyae. the scope of the assessments on root pathogen infections differed between the plots by 5.3% to even 22.6%. Taking into account the life cycle of root rot fungi and the forms of their occurrence in the environment, such a large spread in the assessment data may result not only in the lack of a proper diagnosis and identification of potential long-term disturbances, but also in the inappropriate planning of silviculture work. All three tested methods of assessing the health of Pinus sylvestris were useful in estimating the degree of crop infection, however, the smallest differences in measurement deviation between the crops were recorded using method Z (V=8.5%), which has transects placed diagonally across 300 A.o. H.a. 250 200 150 100 50 0 MF T100 Z 61 Forest District Figure 6. Average number (pcs/ha) of trees with etiologic signs of the Armillaria ostoyae (A.o.) and Heterobasidion annosum (H.a.) in the studied cultures based on evaluation by three methods (MF, T100, Z), and averaged for Miłomłyn Forest District 5 4,5 A.o. 4 H.a. 3,5 3 2,5 2 1,5 1 0,5 0 180a 181c 75d 101d Forest District Figure 7. The average share [%] of trees with etiological signs of A. ostoyae (A.o.) and root rot (H.a.) on 4 examined areas and the average for cultures in Miłomłyn Forest District Table 5. Assessment of damages (% of trees with symptoms) in the studied Scots pine cultures 436di Plots 437h Average [%] assessment method Symptoms Coefficient of variation V [%] 3x33+1 10×10 Z 3x33+1 10×10 Z No symptoms 45.8 59.1 63.4 67.0 68.2 57.8 60.2 9.9 Non-specific needle discoloration 18.8 23.7 118 12.2 11.1 15.8 15.6 24.8 needle cast 12.8 10.5 11.9 15.5 12.0 12.6 12.6 8.6 root diseases 22.6 15.7 12.9 5.3 8.2 13.8 13.1 32.7 0.0 0.0 0.0 0.0 0.5 0.0 0.0 - roots crown roots needles needles crown other Location of symptom dominance Bold – dominance > 10% 62 is a symptom that can be seen after wildlife browsing, pericambial insect feeding, grubs foraging on roots, as a result of infectious diseases – needle cast or root diseases, and drought (Sierota 1988b). The assessment methodology should therefore take into account the specificity of the formation and development of a given phenomenon and enable the symptoms to be more accurately differentiated. The consequences of the presence of root pathogens in the soil (also in the stumps remaining in the crop) are different, as are those of other diseases such as needle cast, or drought. In the case of root pathogen assessments, assuming that all etiological signs of the causative agents can be identified without genetic analysis, it can certainly be argued that the future (sustainability) of the stand is at stake. The time remaining for the application of appropriate felling or the need for premature felling depends on the level of the threat when the crop is already several years old. Therefore, a proper assessment of its condition, preceded by a good knowledge and understanding of phytopathology and the development of forest diseases, is essential. This paper presents examples of the results of different assessment methods used at different ages of crops, varying in their threat from different pathogens. Such are the realities of the assessments performed in the field. For assessments to be reliable and repeatable, devoid of estimates and randomness, they should be based on an appropriate methodology – fairly universal and simple to perform on the one hand, reliable, adapted to the current and properly identified health condition on the other. The presented results indicate the need to flexibly adapt the assessment to the current local threat. Using one method, it is possible to obtain different results when assessing the occurrence of diseases of the aboveground parts of trees, and other results for root diseases. According to the IOL methodology (2012), many of the crops assessed here would be reported as ‘disease-free’. The obtained results confirm the need to individually analyse the assessed areas, both in terms of the occupied habitat and the threat of infection. In general, based on the results obtained in terms of recommending a uniform assessment of the health status of crops, ensuring the highest possible reliability and indicating the necessary conditions for its implementation (different age, habitats, method of establishment, etc.), the following conclusions can be made: • The health status of crops (based on the example of the studied forest districts) is differentiated mainly by the share of root pathogens, which is facilitated by the traditional method of soil preparation, the presence of stumps, and planting using the slit method with a planting bar; • Crown discoloration and thinning is an additional indicator of changes in the root systems – they should be differen- tiated depending on the presence of the etiological signs ofneedle (needle cast) and shoot diseases (Sphaeropsis sapinea [Fr.] Dyko & B. Sutton, Gremmeniella abietina [Lagerberg] Morelet, Melampsora pinitorqua) and drought-induced changes (in the absence of the etiological signs of pathogens); • the main threat to the studied pine crops in forest districts of the Regional Directorate of State Forests in Olsztyn is Armillaria root rot, whose share in more fertile habitats exceeds 5% of the number of trees, and locally, together with annosus root rot, even 20%; • the presence of Armillaria ostoyae in the studied plots is explained by the relatively large number of stumps remaining from the previous stand (probably not protected using the biological method), ploughing (which stimulates the development of the pathogen’s rhizomorphs in the soil) and the introduction of a high proportion of pine trees in this fertile habitat; • The assessment of the crops using the phytopathological monitoring method ‘MF’ and method ‘Z’ indicates the presence of pathological changes in trees to a greater degree than the other assessment methods, especially the T100 transect method. 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Authors’ contribution Z.S. – concept (100%), field work (20%), manuscript writing (60%), graphics preparation (20%); M.M. – field work (50%), manuscript writing (20%), graphics preparation (80%); M.D. –field work (30%), manuscript writing (20%). DOI: 10.2478/frp-2020-0007 Wersja PDF: www.lesne-prace-badawcze.pl Leśne Prace Badawcze / Forest Research Papers Czerwiec / June 2020, Vol. 81 (2): 65–74 ORIGINAL RESEARCH ARTICLE e-ISSN 2082-8926 Determining the value of standing timber for harvest planning optimization Karol Zaborski1*, Jan Banaś2 1 , Anna Kożuch2 Marcule Forest District; Marcule 1, 27–100 Iłża, Poland; 2University of Agriculture in Krakow, Faculty of Forestry, Department of Forest Management, Al. 29 Listopada 46, 31–425 Kraków, Poland *Tel. +48 695390256, e-mail:karol.zaborski@radom.lasy.gov.pl Abstract. Forest managers conducting sustainable forest management are guided by the principles of sustainable use of natural resources, which involve the need for long and short-term planning in organizational units of the State Forests. Plans often differ from reality by the time individual treatments and cuts are to be performed. For economic reasons, it is important to optimize harvest planning, not only focusing on the volume of timber to be harvested, but also the price differences of individual tree species and sort types of wood. The purpose of this study was to present methods evaluating standing timber and to assess their usefulness in optimizing the harvest volume using linear programming. Stands designated to be cut were evaluated using transaction value methods, i.e. “the stumpage value method” M1, the “consumption value” method M2, as well as the net present value (NPV) method M3. The research material was obtained from the State Forests Information System (SILP) for the Marcule Forest District covering the years 2014–2018. The stand values were determined at the beginning and end of the 10-year planning period. We observed that the stand value (standing timber) differed significantly between method M2 as compared to method M1. The value of stands determined by method M3, on the other hand, decreased as the discount rate increased. In the process of optimizing the selection of stands for felling, economic criteria should also be taken into account and this is a direct measure of obtainable standing timber in terms of the cutting possibility in the given planning period. In stands where one species dominates, a simplified method of determining the value (M1) can be used, whereas in stands with significant species diversity, method M2 provides a significantly more accurate value for the cutting timber. However, if harvest volume optimization using linear programming methods is to take longer time periods into account, e.g. 30 years (three 10-year economic planning periods), the most reasonable method for determining the value of stands is the net present value method M3. Keywords: forest valuation, harvest planning, stumpage value, net present value, consumption value 1. Introduction The forest as a complex ecosystem has many functions, including a productive one by providing supply of wood raw material. Sustainable forest management requires all forest functions to be taken into account, with attention paid to the location of stands, their surrounding areas, species-age structure, health and other characteristics. The system regulating the use of managed forests in accordance with the Forest Management Instruction (IUL 2012) currently in force is based on selecting the optimal cut volume Received: 16.03.2020 r., accepted after revision: 3.04.2020 r. © 2020 K. Zaborski et al. based on maturity of the stand to be cut, which is related to felling age and the size of the cut’s average age, assuming that the average age of the holding after completion of the allowable cut will remain at the same level. The size of an allowable cut directly depends on the share and relation between the number of felling, near-felling and pre-felling stands. The lack of a commonly accepted and universal method of determining stand maturity for felling indicates that this is still an undefined area of research in forest management. It is also a practical problem because for many decades, forest managers have been using more intuitive 66 K. Zaborski et al. / Leśne Prace Badawcze, 2020, Vol. 81 (2): 65–74 methods than the results of empirical data (Bednarski et al. 2016) when establishing the queue of stands for cutting. Taking into account the current reality of the broadly understood context surrounding this issue, an economic criterion should be introduced as an additional one to be considered (Piekutin and Skreta 2012). It seems justified to take into account the value of wood raw material that can be obtained at the time of felling in the process of optimising stand harvesting (Płotkowski et al. 2016). When managing forests in compliance with all legal regulations in force and planning management activities for successive years, forest districts must maintain the revenues and costs of their operations at an appropriate level and in proper correlation. The characteristics of the economic conditions of forest management and a forecast of the expected financial results prepared in the forest management plan include, among others, an estimated prediction of expected financial results (Wysocka-Fijorek 2015). Annual planning is one of the most important tasks of forest management. It is to guarantee the proper implementation of material and financial plans in the forest district, while simultaneously caring for the condition of the stands and the development of wood resources. The aim should be to improve methods and reduce their labour intensity, while increasing the accuracy of annual planning at the level of the forest district (Wójcik 2013). Studies have shown (Borecki et al. 2004; Nowak 2004; Pawlak 2008) that the precisely prepared annual plan in many cases differs from the values obtained at the stage of individual treatments and cuts. These discrepancies occur both in total acquisition and, to a greater extent, the volume from species and specific assortments. It seems important not only to strive to more evenly distribute the volume of harvested wood in successive years, but also, above all, to obtain revenue from the sale of harvested raw material, taking into account the price differentiation of individual tree species and types of assortments. Perceiving the economic criterion in the context of optimising the amount of harvested wood will allow for a flexible approach in the event a response is needed to a changing economic situation in the wood market, limited by the demand for a specific group of assortments. Moreover, taking into account the dynamically changing weather conditions in Poland over the last few years (long-term droughts, lack of snow cover), it should be expected that a number of catastrophic phenomena will occur, which could result in the cessation of stand cutting by forest holdings for particular assortments lacking demand at a given time. The aim of this study is to present selected methods of estimating the value of wood raw material in the stands and to assess their usefulness in optimising the size of the felling operation, taking into account the linear programming method. 2. An overview of selected methods for determining stand values Each day, a number of situations are faced in business practice, whose solutions require determining simultaneously the value of all or specific elements of the forest environment, including stands (Zając and Świętojański 2002; Zydroń et al. 2007; Zając 2013). Historically, empirical methods of estimating stand value were developed in reaction to the criticism of static methods (based on percentage accounting and profit and loss forecast accounting), of which Glaser is considered their principal author (Szramka 2018). Depending on the age of the appraised stand, the methods of incurred cost, sale value or expected value were adopted (Partyka and Trampler 1973; Marszałek and Podgórski 1978; Partyka and Parzuchowska 1993; Zając and Świętojański 2001; Klocek and Płotkowski 2009; Zając 2013; Szramka 2018). The incurred cost method (reproduction cost) is used for young stands that do not yet have a use value. The sale value method is applied to mature stands that have a use value. This method calculates the value of the stand based on the income that can be obtained from the harvesting and sale of the produced assortments. Stumpage sales value is the sum of the products of the value of individual assortments (according to sales prices) and the volume share of these assortments (Hauling 2013). The expected value method is used to estimate intermediate-aged stands using reduction coefficients, taking into account, e.g. the quotient of the square of the stand age to the square of the stand’s felling age. These methods have been used to develop stand value tables for particular types of forest trees according to their age and site index class (Partyka and Parzuchowska 1993; Zając 2013; Zając et al. 2014). Several versions of stand value index tables have been developed, which have improved and reduced the workload of stand valuation. However, by using stand value index tables, the average value for the whole country is obtained (Szramka 2016; Zygmunt et al. 2018). Cymerman and Nowak (2017) emphasise that the valuation of forest stands in free market trading is not regulated by law, and the principles of valuing a stand are defined in the interpretive note V.6 (PFSRM 2003). According to the standard V.6, when determining the market value of stands of near-felling, felling and older age, their total volume and the shares of assortments in the timber volume determined on the basis of a stock survey should be taken into account. When determining the timber volume of near-felling, felling and older stands, the method of measuring total diameter at breast height of the trees in that stand should be used (PFSRM 2003). Currently known methods of estimating stand value are: cost value method (reference to the past), market value method (reference to the present) and income value method (investment K. Zaborski et al. / Leśne Prace Badawcze, 2020, Vol. 81 (2): 65–74 value – reference to the future) (Klocek and Płotkowski 2009). Income value methods can be divided into methods by profit and loss forecast value and expected value. The income value in forestry is synonymous with market value, as it reflects the level of all net income from the stand (Zając 2013). A forest stand is an income-generating property (real estate); therefore, the most commonly used method of the valuation of forest properties, when there is no data on their turnover on the market, is currently the so-called investment method. A characteristic feature of the investment method is the discounting or prolongation of net cash flows (Zając and Świętojański 2001). ‘Discounting’ means reducing a certain nominal amount, and the discount rate is used to convert (import) the assumed future cash flows into the present value (Zydroń et al. 2012). ‘Prolongation’ means determining the future value of money (using a specified interest rate). Determining the updated value, called present value, consists in discounting future values and prolonging the value of past cash flows to a specified age (the age of the stand being valued) (Zając 2013). According to other authors, the valuation methods for standing trees in felling stands can be divided into two categories (European Communities 2002), i.e. transaction value methods that use the price obtained from observed transactions in the whole period to the resource’s asset components, and net present value (NPV) methods that are based on calculating the value (or change in value) of the asset by the present value of future net profits. Under the transaction value method, the price per unit of raw material is derived from observed transactions and is referenced to the value of the entire inventory or change in inventory. The price of wood/m3 used in this method can be the price of stumpage (if available) or the price of felled, bucked and stacked wood on the transport route. Where data on the stumpage value (standing trees) are not available, they can be determined on the basis of available prices for felled timber and prepared for delivery, deducting the costs of harvesting, skidding and possible longer storage. The exact calculation of costs is complex, e.g. for skidding, taking into account, among others, tree species, length of skidding, slope inclination, type of land or the skidding agent used (semi-suspended skidding, forwarders). Therefore, the use of generalisations is allowed, in which the stumpage value (standing timber) is defined by applying the available price of felled wood. The stumpage price determined in this way is used to calculate the value of whole stands or to change their value over time, e.g. when they are being utilised. Two variants are distinguished in the transaction value method used for stand valuation: the ‘stumpage value’ method and the ‘consumption value’ method. 3. Study material and methods The study material consists of the following data from the State Forests Information System (SILP) for the Mar- 67 cule Forest District, in particular: (1) taxation descriptions of selected stands (felling) as of 1 January 2017 (Table 1); (2) reports on the implementation of logging plans including the volume of harvested wood by type and assortment by cutting position and activity groups; (3) sum of volume and value of wood sold by type–assortment group and (4) harvesting and skidding costs. The data for points (2–4) were compiled annually and cover 2014–2018. The average costs of harvesting and skidding wood in the Marcule Forest District for 2014–2018 are presented in Table 2. The costs of harvesting and skidding are weighted by the volume of respectively harvested and skidded timber in the given year in the whole forest district, regardless of the type of harvesting and skidding technology used and other parameters. The following methods were proposed for determining the value of wood raw material in the felling stands: 1) The ‘stumpage value’ method M1 This method calculates the value of raw material per stem as the product of the average volume of a given stand and the average price obtained from the sale of 1 m3 of wood in the entire forest district in 2014–2018, less the average costs of harvesting and skidding in this period. The price of the wood is weighted by the volume of sold raw material (in 2014–2018), regardless of the type and assortment of wood. The value of wood raw material was determined according to the formula: Wn = Vn (C – K) [PLN/ha] (1) where Wn is the value of wood raw material per 1 ha in stand n, Vn is the average stand volume of n (m3/ha), C is the average price obtained from the sales of 1 m3 of wood in the forest district in the last 5 years and K is the average cost of harvesting and skidding 1 m3 of wood in the last 5 years. 2) The ‘consumption value’ method M2 The stumpage value calculated with this method is the product of the average volume of each tree species in the stand, the average price obtained from the sale of 1 m3 of a specified given assortment and species of timber, and the percentage share of the assortment groups of each species minus the average costs of harvesting and skidding. The average price of a given species and assortment (groups of assortments) was calculated as the weighted average of the quantity of the assortment sold. In this paper, the assortments were divided into seven groups using the nomenclature adopted in forest practice, i.e. large-size wood of quality classes A and B as the so-called ‘class’ wood without division into thickness classes; large-size wood of quality classes C K. Zaborski et al. / Leśne Prace Badawcze, 2020, Vol. 81 (2): 65–74 68 Table 1. Taxation features of selected stands with different species compositions in the Marcule Forest District in 2017 Age [years] Tree density index Gross volume** [m3/ha] 9 80 0.7 212 SO 1 80 0.7 27 28 l SO 10 116 1.0 368 72 k BRZ 10 57 0.9 200 122 c OL 10 68 0.7 167 128 c DB 8 90 0.8 257 128 c SO 2 90 0.8 71 128 k DB 10 80 0.8 362 136 f BRZ 6 75 0.7 161 136 f SO 4 75 0.7 120 221 l DB 6 102 0.9 189 221 l BRZ 2 82 0.9 57 221 l SO 2 82 0.9 63 Location Species* 22 i BRZ 22 i Share [%] * SO – pine; BRZ – birch; OL – alder; DB – oak ** conversion from gross to net was adopted at the level of 0.82 Table 2. Unit average costs of cutting and logging in (PLN/m3) in the Marcule Forest District in 2014–2018 Year Cost of cutting Cost of logging Sum 2014 23.25 22.53 45.78 2015 22.01 21.53 43.54 2016 24.44 25.47 49.91 2017 26.86 26.61 53.47 2018 29.25 28.43 57.68 Average 25.16 24.91 50.08 ments except firewood and wood of quality class S4, whose price is decidedly lower. The value of wood raw material was determined according to the formula: Wn = ∑li=1 ∑ms=1 Vni 0,01Usi Csi – VnK [PLN/ha] (2) Source: own elaboration where Vni is the volume of species i in stand n, Usi is the share (%) of assortment group s in the total volume of species i (Table 3), Csi is the price obtained from the sale of 1 m3 of wood of assortment s for type (species) i (Table 4), l is the number of species in stand n and m is the number of assortment groups (seven groups in this study). Other symbols are designated as in formula (1). in the first, second and third thickness classes, respectively; large-size wood of quality classes D without division into thickness classes and medium-size wood covering all assort- 3) NPV method M3 The NPV method calculates the value of forest assets according to the present value of future net economic benefits. Basically, a future income and cost model and a disco- 69 where r is the discount rate (1%, 2.5%, 5%, respectively) and t is the time period. Other symbols are designated as in formulas (1) and (2). The value of the stands was determined at the beginning and end of the 10-year economic planning period. The calculations performed with formula (3) assume that average prices are fixed at the beginning and end of the planning period and do not change. The stand volume at the end of a 10year economic planning period was determined by adding the growth volume increment of the stand to the volume at the beginning of the current period. unt rate (Bettinger et al. 2017) are required to determine this value. Depending on the complexity of the model and how the discount rate is determined, there are several options for determining the present value. In the simplest one, the discount rate is determined externally, e.g. as a result of consulting forestry experts; it is accepted that the allowable level of the discount rate for forest assets in Europe is between 1% and 2.5% (European Communities 2002). In the case of long-term capital, e.g. a tree stand, a discount rate of 1%-3% is usually assumed (Podgórski and Zydroń 2001; Zydroń et al. 2012). According to other authors, the discount rate should be between 2% and 3% (Adamowicz 2018) and should not exceed 7% for stands (Grege-Staltmane et al. 2010). In turn, Bullard and Straka (2011) indicated that the level of the discount rate for wood resources (products) should be lower than the one used in companies to calculate a specific investment. Forestry investments are long term and require taking into account certain risks and uncertainties relating to this (Samuelson 1995; Holopainen et al. 2010). This method calculates the value of wood raw material as the value determined according to the M2 method, which is then discounted at the accepted rate, i.e. 1%, 2.5% and 5%. The value of wood raw material was determined by the formula: 4. Results The dominant type of wood in the Marcule Forest District is pine, which accounted for 89.0% of the total wood harvested by logging in 2014–2018. Oak wood constituted 5.3%, hornbeam wood 1.3% and birch wood 1.0%, while the share of other species did not exceed 1%. WC0 class timber intended for sawmills prevailed in the assortment structure, its share depending on the type ranged (total of WC01, WC02, WC03) from 75.4% for pine to 7.7% for oak (Table 3). Hornbeam wood was produced only in medium-sized assortments, in which the share of firewood dominated (75.2%). The price of wood weighted by the volume of sold raw material (in the period 2014–2018) averaged 219 PLN/m3, regardless of the wood type and assortment (Table 4). De- WNPV = (∑li=1 ∑ms=1 Vni 0,01Usi Csi – VnK) / (1 + 0,01r)t [PLN/ha] (3) Table 3. The share of assortment groups by type (species) of wood in 2014–2018 Type of wood Assortment share [%] S S4 WAB0 WC01 WC02 WC03 WD Sum [100%] BRZ 9.9 51.0 - 2.9 10.0 2.4 23.8 100 DB 32.5 41.7 0.5 0.2 2.2 5.3 17.6 100 GB 24.8 75.2 - - - - - 100 JD 22.0 11.9 0.6 4.0 19.4 38.9 3.2 100 OL 9.8 51.9 0.4 3.3 6.8 2.6 25.2 100 SO 7.1 5.1 6.4 9.9 50.2 15.3 6.0 100 Average 9.3 10.0 5.8 9.0 45.1 14.4 6.4 100 *WAB0 – large-size wood of quality classes A and B; WC01 – large-scale quality wood class C in the first thickness class; WC02 – large-scale quality wood class C in the second thickness class; WC03 – large-size wood of the quality class C in the third thickness class; WD – large-size wood of quality class D of all thickness classes; S – includes all sizes of medium-sized wood. except for S4; S4 – firewood; JD – fir; GB – hornbeam Source: own elaboration K. Zaborski et al. / Leśne Prace Badawcze, 2020, Vol. 81 (2): 65–74 70 Table 4. Average wood prices [PLN/m3] by species type and assortment groups in 2014–2018 Group of assortments* Type of wood S S4 WAB0 WC01 WC02 WC03 WD Average BRZ 140 136 270 202 222 244 178 153 DB 194 133 1772 366 509 691 374 229 GB 157 148 ─ ─ ─ ─ ─ 150 JD 141 101 361 243 279 306 200 231 OL 128 98 293 180 259 332 202 129 SO 151 107 308 232 263 292 193 224 Average 152 119 314 232 263 301 212 219 * Explanations of symbols as in tables 1 and 3 Source: own elaboration pending on the type, the price ranged from 129 PLN/m3 for alder to 231 PLN for fir. Depending on the assortment, the price ranged from 119 PLN for firewood to 301 PLN/m3 for third class sawmill (WC03) and 314 PLN for valuable wood (WA0 and WB0 together). The value of wood raw material determined using the simplified M1 method according to formula (1) depends directly on the stand’s abundance and the adopted average price of wood. For the selected example stands, this value ranges from 21,783.24 PLN/ha for alder stand 122 c with a net abundance of 137 m3/ha to 47,859.32 PLN/ha for pine stand 28l with a net abundance of 302 m3/ha (Fig. 1). The M2 method allows us to determine the timber volume of wood raw material according to the type–assortment structure. In selected example stands, the largest amount of sawmill wood (227.2 m3/ha, total of WC01, WC02, WC03) is found in pine stand 28l, while the largest amount of medium-sized wood, except for class S4 (96.5 m3/ha), is found in oak stand 128 k (Table 5). The value of the stands (wood raw material) determined by the M2 method according to formula (2) depends on the stand species composition and assortment structure and differs from the value of the raw material determined by the M1 method (Fig. 1). In stands with a significant share of birch (22 i, 72 k, 136 f) or alder (122 c), the value of the raw material determined by the M2 method is significantly lower compared to the value of those stands determined by the M1 method. When pine (28l) or oak (128 c, 128 k) dominates in the stand composition, the M2 method indicates higher stand values compared to the M1 method. Stand values determined by the M3 method of discounting future income at the current moment (NPV) according to formula (3) are shown in Table 6. Stand values at the beginning of the period (column 2) and at the end of the period at a zero discount rate (column 3) are equal to those determined by the M2 method. The following columns (4–6) show the NPVs of the wood raw material at the end of the 10-year period at different discount rates (from 1% to 5%). As the discount rate increases, the present value of the raw material that would be obtained at the end of the period decreases. The difference between the value of the stand at the beginning of the period and the present value that the Figure 1. Value of wood raw material determined according to the M1 method and the M2 method in selected stands of the Marcule Forest District in 2017 Source: own elaboration K. Zaborski et al. / Leśne Prace Badawcze, 2020, Vol. 81 (2): 65–74 71 Table 5. Timber volume of assortments in selected stands in the Marcule Forest District in 2017 Assortments [m3] Stand Species S S4 WAB WC1 WC2 WC3 WD Total BRZ 17.2 88.7 0.0 5.0 17.4 4.2 41.4 173.8 SO 1.6 1.1 1.4 2.2 11.1 3.4 1.3 22.1 28 l SO 21.4 15.4 19.3 29.8 151.3 46.1 18.1 301.4 72 k BRZ 16.2 83.6 0.0 4.8 16.4 3.9 39.0 164.0 122 c OL 13.4 71.1 0.5 4.5 9.3 3.6 34.5 136.9 DB 68.5 87.9 1.1 0.4 4.6 11.2 37.1 210.7 SO 4.1 3.0 3.7 5.8 29.2 8.9 3.5 58.2 DB 96.5 123.8 1.5 0.6 6.5 15.7 52.2 296.8 BRZ 13.1 67.3 0.0 3.8 13.2 3.2 31.4 132.0 SO 7.0 5.0 6.3 9.7 49.4 15.1 5.9 98.4 DB 50.4 64.6 0.8 0.3 3.4 8.2 27.3 155.0 BRZ 4.6 23.8 0.0 1.4 4.7 1.1 11.1 46.7 SO 3.7 2.6 3.3 5.1 25.9 7.9 3.1 51.7 BRZ 51.1 263.5 0.0 15.0 51.7 12.4 123.0 516.6 DB 215.3 276.3 3.3 1.3 14.6 35.1 116.6 662.6 OL 13.4 71.1 0.5 4.5 9.3 3.6 34.5 136.9 SO 37.8 27.1 34.0 52.6 267.0 81.4 31.9 531.8 m3 317.7 637.9 37.9 73.5 342.5 132.4 306.0 1847.9 % 17.2 34.5 2.1 4.0 18.5 7.2 16.6 100.0 22 i 128 c 128 k 136 f 221 l Sum Total Explanations of symbols as in tables 1 and 3 Source: own elaboraton stand will reach at the end of the period is important when deciding whether to designate a stand to be felled in a given economic period or leave it for the next one. If the increase in value (%) is greater than the interest that would be obtained after felling the stand, selling the wood and depositing the sales proceeds in a bank, the stand should be left for further cultivation to the next period. If the increase in value would be less than the achievable interest, from an economic point of view, the stand should be designated for felling in the current period. In the analysed harvest at a 1% discount rate, only the stand 72 k shows a positive and greater than the assumed rate (4%) of increase of present value during the first 10-year period. This is a 57-year-old birch stand with relatively dynamic current growth. The remaining stands show a decrease in NPV at the end of the economic period – decreasing even more at higher assumed discount rates. A negative NPV increment is characteristic for older stands with lower growth dynamics. Due to the fact that the stands also perform non-productive functions, a negative NPV increment does K. Zaborski et al. / Leśne Prace Badawcze, 2020, Vol. 81 (2): 65–74 72 Table 6. The value of wood raw material determined according to (NPV) in selected stands of the Marcule Forest District in 2017 and 2027 (at the beginning and end of the planning period at various discount rates) Value of wood raw material [PLN/ha] Stand year 2027 discount rate [%] year 2017 0 1 2,5 5 22 i 23 389.73 24 988.49 22 621.75 19 520.97 15 340.77 28 l 59 339.14 63 084.80 57 109.85 49 281.74 38 728.59 72 k 17 957.67 20 585.62 18 635.90 16 081.46 12 637.79 122 c 13 380.24 14 552.23 13 173.95 11 368.18 8 933.81 128 c 51 892.95 56 138.36 50 821.33 43 855.20 34 464.09 128 k 56 949.16 62 126.35 56 242.18 48 533.01 38 140.19 136 f 33 773.46 36 423.70 32 973.90 28 454.14 22 360.99 221 l 45 118.63 48 235.41 43 666.89 37 681.43 29 612.36 Source: own elaboration not automatically mean that the stand is qualified for felling. Instead, it can be a helpful tool for deciding on the order in which stands are to be designated for felling, up to the level of a specific cut, taking into account other factors, including the multifunctionality of the forest. 5. Summary and conclusions The methods presented in this paper for determining the value of wood raw material in stands can be used in the processes of optimising the selection of stands for felling. The choice of the method should depend on the forestry unit, which is subject to regulations, and especially on the age and species structure of the stands. The M1 method can be applied to simple vertical stands, stands of a single age and species, in managed forest holdings. The disadvantage of this method is that it does not take into account either the tree species or the prices of individual assortment groups, which significantly impact the final stumpage value. On the other hand, the M2 and M3 methods take into account the differences among the assortments for individual species in the stand and the percentage of species in the total volume of the stand. However, they are somewhat generalised due to the structure of already performed harvests and the existing assortment–species system, which may differ with respect to stands that remain to be felled in the future (European Communities 2002). The M3 method, which additionally involves discounting, should be applied in optimisation models that also use an economic criterion, as this takes into account the change in the value of future income from the forest. As a rule, several successive economic planning periods are covered, e.g. 3-, 4-, 5- or 10year periods in the case of methods based on linear programming (Marušák and Kašpar 2015). The following conclusions can be drawn from the research conducted: 1. Both natural and economic criteria should be taken into account when determining the size of a felling operation, the direct measure of which is the value of the wood raw material that can be harvested in the stand analysed for felling potential in a given planning period. 2. In forest districts with one dominant species and low habitat diversity, a simplified M1 method may be used to determine the value of felling stands. Both the type–assortment structure and the price of wood will be similar in individual stands. 3. In forest districts with a significant species diversity of stands, the M2 method, which takes into account the type– assortment structure of individual stands, is better suited to determine the value of felling stands. 4. The M2 method makes it possible to determine the volume of wood raw material in individual stands, which is important and allows the economic situation (downturn) to 73 be taken into account for specific assortments when determining the stands to be felled in annual planning. 5. The M3 method can be used to determine stands for felling, especially in forests with a dominant production function. 6. In optimising stand selection for felling using the linear programming method, which often takes into account a longer time horizon, e.g. 30 years (three 10-year economic planning periods), the M3 method of NPV seems to be the most well-founded method for determining stand values. Conflicts of interest The authors declare no potential conflicts of interest. Source of funding The study was financed by the authors’ own funds. References Adamowicz K. 2018. A review of selected methods to determine the economic value of forest: Polish research, w: New perspectives in forest science. 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Author’s contribution K.Z. – concept, collection of study material, literature review, methodology, calculations, text editing; J.B. – concept, methodology, text editing; A.K. – literature review, text editing DOI: 10.2478/frp-2020-0008 Wersja PDF: www.lesne-prace-badawcze.pl Leśne Prace Badawcze / Forest Research Papers Czerwiec / June 2020, Vol. 81 (2): 75–80 original research article e-ISSN 2082-8926 Assessing the occupation of nest boxes by dormice (Gliridae) in the Carpathian forests Izabela Fedyń1*, Ewa Pierzchała1, Katarzyna Nowak1, Joanna Wąs1, Adela Malak1, Katarzyna Śnigórska2 1 student naturalist society at the Jagiellonian University, ul.gronostajowa 7, 30–387 Kraków, Poland; 2the complex of landscape Parks of the Małopolskie Voivodeship, ul. Adama Vetulaniego 1a, 31–227 Kraków, Poland *tel.+48 665821721; e-mail: izabela.fedyn@gmail.com Abstract. Nest boxes for dormice (Gliridae) can significantly increase the habitat’s carrying capacity for these species in areas under high anthropopressure and facilitate the long-term monitoring of populations. as part of the active protection of dormice in the Carpathian Landscape Parks in Małopolska, in August and September 2019, 575 boxes of two different sizes were checked for the presence of adults, young or nests. additionally, habitat conditions within a 25 m radius were recorded (e.g. forest stand, estimated understory cover, the approximate number of natural shelters, fruiting plant species). The vast majority of all nest boxes – 79% – were used by dormice, but also birds and insects frequently occupied these shelters. out of four species of dormice that occur in Poland, two were recorded in the study area: hazel dormice Muscardinus avellanarius and fat dormice gli sglis. they were found in all surveyed landscape parks and inhabited mainly fir stands. Hazel dormice preferred smaller nest boxes and were generally more common than fat dormice, which preferred large boxes. on the other hand, fat dormice were more common in areas rich in fruiting plant species. Our research thus confirmed the usefulness of artificial shelters for dormouse in active protection. Keywords: dormouse, nest boxes, rodents, conservation, forest mammals, gliridae 1. Introduction currently, all species of small mammals of the dormouse family (gliridae) occurring in Poland – the fat dormouse Glis glis, hazel dormouse Muscardinus avellanarius, forest dormouse Dryomys nitedula and garden dormouse Eliomys quercinus – are legally protected (regulation 2016). according to the international Union for conservation of nature classification, they are in the least concern category, except for the garden dormouse, which is considered a near threatened species. in Poland, the range of dormouse occurrence is dispersed; the hazel and fat dormice are the most common. the forest dormouse is found in the southern and eastern parts of the country, while the garden dormouse is found only in the Babia góra massif (atlas ssaków Polski 2020). the current state and distribution of dormouse populations is the result of large-area deforestation in the past and forest management, changing the structure and continuity of forests (Jurczyszyn, Wołk 1998). Habitat loss and fragmentation have caused a decrease in the number of these mammals (Mortelliti et al. received: 20.03.2020 r., accepted after revision: 20.05.2020 r. © 2020 I. Fedyń et al. 2011, 2014). an important factor affecting dormouse survival and its local density is habitat quality, which mainly determines the amount of available food (Mortelliti et al. 2014). the small mammals of the gliridae family need shelter to establish nests for resting, rearing young and protection from predators. therefore the lack of natural hiding places in forests is a limiting factor (Juškaitis 2005). one of the possible measures for the active protection of this animal group, in addition to preserving habitats with old trees containing cavities, is to hang artificial nest boxes, which significantly increase the potential number of resting places and shelters. in addition, this type of measure allows for the long-term monitoring of the population, providing information on the changes occurring in it and assessing the effectiveness of their protection (Williams et al. 2013). a detailed analysis of the results of active protection measures for the dormouse will allow more effective methods to be developed and, in the long term, the proper status of the population to be maintained. the presented research was aimed at verifying the degree of dormouse colonization of artificial nest boxes. 76 I. Fedyń et al. / Leśne Prace Badawcze, 2020, Vol. 81 (2): 75–80 2. Study area the study area consisted of 4 of the 11 landscape parks (LPs) in the Małopolska Voivodeship Landscape Park complex, located in south-eastern Poland, in the Pogórze Karpackie region of the Carpathian Mountains (Ciężkowicko-Rożnowski LP, Wiśnicko-Lipnicki LP and the Brzanki range lP) and in the Beskids (Poprad lP). their total area is 1013 km2, of which 54.9% is forested (RDOŚ 2013). 3. Study methods Fieldwork was conducted in August and September 2019. For the research, the “english” type of nest box was inspected (with the hole facing the tree trunk) in two sizes: small (12 cm×12 cm×15 cm) and large (16 cm×16 cm×35 cm), hung approximately 3 m above the ground. the boxes (nest boxes) were located along forest roads at average intervals of 40 m. the individual research plots were located at a minimum distance of 1 km from each other (Fig. 1). in total, 575 boxes were inspected, including 242 large and 333 small ones. During the inspections, the species present in the box was recorded and, in cases where they escaped, the animals were identified by the evidence left behind and/or it was assigned to a higher taxon. in the absence of the animal in the box at the time of the inspection, where possible, nest remains were identified by their characteristic features (shape and material used). if more than one nest was left in the box, their number was determined by the apparent differences in construction, material used and degree of decomposition. If a nest was significantly decomposed, making it difficult to exactly ascribe it to species, it was assigned to a higher taxon. A nest box was defined as inhabited (hereinafter also used) when the presence of a given species or a nest left by that species was found in it at the time of inspection or when its nest was recognized. in addition, selected parameters were estimated of the habitat within a 25 m radius from the tree with the nest box: dominant tree species (stand); degree of undergrowth cover (in a four-stage scale, where 0 meant the complete lack of shrubs and undergrowth, 1 – single shrubs and trees covering up to 25% of the area, 2 – numerous shrubs and trees with cover from 26% to 75%, 3 – numerous shrubs and Figure 1. locations of the surveyed landscape Parks (PK) and study areas I. Fedyń et al. / Leśne Prace Badawcze, 2020, Vol. 81 (2): 75–80 trees covering ≥76% of the area); the presence of species potentially constituting a food base for dormice (among others, beech Fagus sylvatica, Quercus spp., common hazel Corylus avellana, blackberryRubus spp. and blueberryVaccinium spp.) as well as the presence of natural shelters –trees with cavities (0 – none, 1 – presence of trees with cavities). the obtained data were analysed for the potential dependence of occupancy on the size of the boxes with chi-square tests at a significance level of α=0.05, using a sample of positive confirmations of the presence (finding an individual in the box at the time of inspection or recognition of a nest) of fat and hazel dormice and empty boxes (N=276). The analysis of nest boxoccupation by dormice, in relation to the number of nests in the box, was performed using the Kruskal–Wallis test, taking into account all the nest boxes used by these mammals, including the nests not identified to species (N=193, excluding currently occupiedboxes where it was impossible to check the number of nests in the box). the preference of dormouse occupancy depending on selected habitat parameters was calculated using the formula for Ivlev’s index (1961): r–p E = –––––– r+p where r–availability of a given type of habitat in the area under study, p– share of the areas occupied by dormice. This factor takes values from −1 (total avoidance) through 0 (use proportional to availability) to 1 (total positive selection). the research was conducted on the basis of a permit from the Regional Director of Environmental Protection in Kraków (decision no. OP-I.6401.210.2019.GZ). 4. Results Occupation of nest boxes The presence of fat and hazel dormice was confirmed in all the lPs included in the study, whereas the presence of forest and garden dormice was not noted. The vast majority of nest boxes (79%, n=452) contained evidence of their use by dormice. The fat dormice used 10% 77 of the boxes (n=54; a litter was present in 18 of them), while hazel dormice were found in 16% (n=94; a litter was present in 2 of them). Due to the significant state of decomposition of plant material, 300 nests found in the boxes could not be attributed to a particular rodent species. in the remaining 67 boxes, nests of other animals, mainly birds, were found. Only 56 boxes (9.7%) were empty and did not have any evidence of use. Both nest box sizes were characterized by a similar degree of use – 93% of large and 87% of small ones were occupied by dormice, birds, insects or mice. The fat dormouse occupied the large nest boxes significantly more often (X2=56,649; df=1; p<0.00001), whereas the hazel dormouse occupied the small ones (X2=43,369; df=1; p<0.00001). Additionally, occupation was influenced by the presence of old nests in the boxes. the nests of the fat and hazel dormice were found more frequently in nest boxes with a greater number of old bird nests (KW-H(1;193)=9.23; p<0.002; KW-H(1;193)=19.1227; p<0.00001). Comparison of occupation among the parks in all parks, most of the nest boxes were used by animals – dormice, mice, birds or insects (table 1). among dormouse species, the fat dormouse dominated nest box occupation only in Poprad lP, while the hazel dormouse dominated in the remaining parks. Habitat characteristics in the area around the nest boxes the boxes were mainly hung in three types of forests: dominated by fir, beech and beech–fir stands (Table 2). The boxes used by the fat and hazel dormice were located in the stands proportionally to their share (Ivlev’s index E equal or close to zero). the boxes were placed in locations with different understory densities. those characterized by a lack of understory were less frequently inhabited by dormice than would result from their availability (table 2). the vast majority of boxes were located in forest areas lacking natural nest cavities (category 0), which was proportional to the availability of all boxes in the study area. Most of the boxes (93%) were located in an area where one (28%), two (44%) or three (21%) plant species Table 1. nest boxes occupation in carpathian landscape parks in lesser Poland landscape Park PK Ciężkowicko-Rożnowski PK Number of occupied nest boxes (share) [%] fat dormouse hazel dormouse all dormice species all animals 3 (3.3) 30 (33.3) 70 (77.8) 87 (96.7) 11 ( 11.6) 20 (21) 67 (70.5) 86 (90.5) Popradzki PK 33 ( 10) 25 (7.3) 276 (80.5) 305 (88.9) Wiśnicko-Lipnicki PK 7 (14.9) 19 (40) 39 (83) 41 (87.2) Pasma Brzanki PK I. Fedyń et al. / Leśne Prace Badawcze, 2020, Vol. 81 (2): 75–80 78 Table 2. the value of the ivlev index (E) for habitat variables around nest boxes Dormouse [%] ivlev index E habitat variables in community fat hazel fat hazel beech forest 27.5 18.5 30.9 -0.2 0.1 fir forest 43.8 46.3 43.6 0.0 0.0 beech- fir forest 14.1 18.5 11.7 0.1 -0.1 0 7.6 1.9 4.3 -0.6 -0.3 1 40.2 33.3 38.3 -0.1 0.0 2 37.3 48.1 36.2 0.1 0.0 3 14.5 16.7 21.3 0.1 0.2 0 67.0 64.8 73.4 0.0 0.0 1 29.7 35.2 24.5 0.1 -0.1 0 2.2 0.0 3.2 -1.0 0.2 1 27.5 20.4 28.7 -0.1 0.0 2 43.8 44.4 34.0 0.0 -0.1 3 20.7 31.5 27.7 0.2 0.1 4 5.8 3.7 6.4 -0.2 0.0 0 32.6 35.2 34.0 0.0 0.0 1 67.4 64.8 66.0 0.0 0.0 0 19.6 16.7 17.0 -0.1 -0.1 1 80.4 83.3 83.0 0.0 0.0 0 70.7 70.4 68.1 0.0 0.0 1 29.3 29.6 31.9 0.0 0.0 forest type: understorey cover cavities occurrence fruiting plant species number forest floor species occurrence beech occurrence hazel occurrence were present as a potential food base for dormice. Both the fat and hazel dormice occupied mainly nest boxes located in plots with at least two fruiting species (80% and 68% of the boxes used by the species, respectively). the fat dormouse clearly avoided boxes in sites without fruiting species, while a preference was not observed for the hazel dormouse. Both the fat dormouse and hazel dormouse were more abundant in nest boxes located in areas with beeches (83%); however, this reflected the share of this species in the study area (it was found in 80% of the area with nest boxes). Additionally, over half of the boxes occupied by the fat dormouse (65%) and hazel dormouse (66%) were in plots characterized by the presence I. Fedyń et al. / Leśne Prace Badawcze, 2020, Vol. 81 (2): 75–80 of at least one fruiting understory species, mainly blackberry. Common hazel was present in 29% of the area surrounding the inspected boxes, which is reflected in the presence of this species in the vicinity of boxes occupied by the fat dormouse (30%) and the hazel dormouse (32%). 5. Discussion the high percentage of nest boxes used by gliridaemammals shown in this study confirms the validity and effectiveness of hanging artificial shelters for these woodland mammals. The frequent use of nest boxes by dormice probably indicates an insufficient number of natural shelters in the studied habitats. studies have shown that hazel dormice clearly prefer small nest boxes, probably due to the fact that they avoid competition with larger species (such as the fat dormouse) (Vogel, DuPlain 2012). not infrequently,dormice and cavity nesting birds, which are a common food source in the diet of these small mammals, occupy the same boxes (sarà et al. 2005; adamík, Král 2008). additionally, dormice can use material from bird nests to build their own nests (Ściński, Borowski 2006). Differences in nest box use in individual parks by the fat dormouse and hazel dormouse may result from the different habitat preferences of these species (Juškaitis, Šiožinytė 2008) or from the different status of dormouse populations in these areas. The results suggest that in Ciężkowicko-Rożnowski LP and Wiśnicko-Lipnicki LP, the boxes were located in much more convenient sites for the hazel dormice as they inhabited a significant share of the available boxes. On the other hand, only a small number of fat dormicewere observed despite the presence of the large nest boxes they prefer. The dormouse inhabited mainly three types of forests, fir, beech and beech–fir, which are the most common ones in the carpathians, and this is where most of the nest boxes were located. it may seem surprising to see a frequent occurrence of dormice in fir stands. In the case of the hazel dormouse, there are data in the literature confirming the presence of this species in coniferous forests. the frequent use of nest boxeshung in such stands by the hazel dormouse was described by Juškaitis (2007) among others. even fat dormice, which are usually strongly associated with beech stands, may sometimes prefer habitats with an increased proportion of coniferous trees, whose shoots provide a certain source of food, especially in years when beech crops are less abundant (cornils et al. 2017; Jurczyszyn 2018). the presence of coniferous species such as fir, due to their construction, may facilitate the movement of dormice. it is also possible that their frequent occurrence in fir-dominated forests is due to the timing of the observations (a year of a poor beech crop). the presence of a dense understoryin the forest areas where most of the boxes were inhabited by dormice confirms its importance in the selection of habitats by these animals. shrubs and young trees form cor- 79 ridors for their safe movement (Karantanis et al. 2017), and a complex spatial arrangement of the vegetation may be more important in this mammal’s habitat selection than species diversity (Panchetti et al. 2007). hazel dormice in particular are known as a species closely linked to habitats with a dense and species-differentiated understory, which they willingly choose as nesting sites (Juškaitis et al. 2013). thus, the observations made seem quite surprising as one would expect that in such habitats, the percentage of nest boxes occupied by the hazel dormouse will not be high due to the availability of numerous natural nesting sites (Wolton 2009). tree cavities can serve as natural shelters and nesting sites for dormice (sevianu, Philippas 2008), but when they are in short supply, these mammals successfully occupy artificial shelters. the nutritional abundance of a habitat is important in the selection of nesting sites by dormice (Bright, Morris 1990). The vast majority of the boxes used were located in the vicinity of beech, which is an important source of food for these animals. common hazel is also one of the plant species providing high-energy food for the dormouse (Juškaitis 2007, Jurczyszyn 2018). however, the mere presence of fruiting vegetation, such as beech, hazel and those in the understory, is not a good indicator of the attractiveness of habitats for dormouse species as these plants are characterized by a varied abundance of their fruiting over the years and only good crop years (in the case of beech) may influence the more numerous occupancy of nest boxes (Trout et al. 2015). Dormice prefer forests with a large number of fruiting species, which provide a varied diet throughout their active season, especially in years when beech does not have a good crop (cornils et al. 2017). Summary this study, conducted in carpathian lPs, was a preliminary attempt to assess the use of nest boxes by the dormouse in relation to selected habitat parameters. the obtained results confirm the high demand for nest boxes by dormice (fat dormouse and hazel dormouse). nest boxes for dormice perform well in areas where the number of natural shelters is insufficient, and hanging them proves to be a useful tool in the active protection of these endangered mammals. Conflict of interest The authors declare that they have no potential conflicts of interest. Acknowledgements and source of funding The research was financed by the Council of Scientific circles of the Jagiellonian University. the authors would 80 I. Fedyń et al. / Leśne Prace Badawcze, 2020, Vol. 81 (2): 75–80 like to thank the MałopolskaVoivodeship Landscape Parks complex for enabling the research to be conducted and the members of the student naturalists circle of the Jagiellonian University for their involvement in the fieldwork. References adamík P., Král M. 2008. climate and resource-driven long-term changes in dormice populations negatively affect hole-nesting songbirds. Journal of Zoology 275(3): 209–215. DOI 10.1111/j.1469-7998.2008.00415.x. atlas ssaków Polski 2020. ssaki. https://www.iop.krakow.pl/ssaki [10.02.2020]. Bako B., hecker K. 2006. Factors determining the distribution of coexisting dormouse species (gliridae, rodentia). Polish Journal of Ecology 54: 379–386. Bright P.W., Morris P.A. 1990. Habitat requirements of dormice Muscardinus avellanarius in relation to woodland management in southwest england. Biological Conservation 54(4): 307–326. 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Using long-term volunteer records to examine dormouse (Muscardinus avellanarius) nestbox selection. PLoS ONE 8(6): e67986.DOI10.1371/journal.pone.0067986. Wolton R. 2009. Hazel dormouse Muscardinus avellanarius (l.) nest site selection in hedgerows. Mammalia 73(1): 7–12. DOI 10.1515/MAMM.2009.001. Vogel P., Du Plain J. 2012.Testing the use of two types of nest box by the common dormouse Muscardinus avellanarius. Peckiana 8: 157–165. Authors’ contribution i.F. – author of the concept and research project, fundraising, development of the research assumptions and methods, data collection, analysis of results, manuscript preparation; e.P. – data collection, statistical analysis, analysis of results, manuscript preparation; K.n. – data collection, statistical analysis; J.W. – data collection, preparation of figures and tables; A.M. – data collection, literature preparation; K.Ś. – author of the concept and research project, development of the research assumptions and methods. DOI: 10.2478/frp-2020-0009 Wersja PDF: www.lesne-prace-badawcze.pl Leśne Prace Badawcze / Forest Research Papers Czerwiec / June 2020, Vol. 81 (2): 81–90 reVieW article e-ISSN 2082-8926 Geocaching in education – a review of international experiences Part 2. Recipient, location and subject matter of education Ewa Referowska-Chodak Warsaw University of life sciences – sggW, institute of Forest sciences, Department of Forest Protection, ul. nowoursynowska 159, 02–776 Warsaw, Poland tel.: +48 22 5938169, e-mail: ewa_referowska_chodak@sggw.pl Abstract: this article discusses the recipient, locations and subject matter of education using geocaching, based on a literature review. the aim is to aid the implementation of similar methods of education in Poland, including forest education, by providing practical information and guidelines. in the literature, the most frequently mentioned recipients of geocaching education are pupils, especially between 10–18 years of age, and university students. this is due to the fact that the authors of the publications were mostly school and academic teachers, as well as students and doctoral students of teaching and social faculties. For the same reason, the preferred locations of educational geocaching were also school/university areas and their immediate vicinity, as well as urban areas, including parks. Locations modified to a lesser degree by anthropogenic influences such as protected areas, waterfronts and forests were also mentioned. the subject range of geocaching classes is very wide, although geography, mathematics, biology, ecology, history, culture, modern technology/equipment, linguistics and physical education were particularly frequently mentioned. subjects related to geology, local society, economy and art were also reported. regarding recipients of educational geocaching, the literature clearly indicates limitations in its application to the youngest age groups, while at the same time its great usefulness in the education of all other age groups is highlighted. in addition to the currently dominating anthropogenic geocaching locations, Poland offers a large variety of natural places, such as forest areas, which are already used for informal field education. These locations furthermore enable multidisciplinary education, which is in line with the extremely wide range of subject content proposed for educational geocaching. Keywords: Adventure education, educaching, field education, forest education 1. Introduction educational potential of geocaching, which is a game of hiding caches/boxes by some contestants (‘geocachers’), and finding them – on the base of geographical coordinates – by other contestants (Sherman 2004; Samołyk 2013; Majdak, Świder 2016), was noticed in the world very fast, only after a year since it started functioning (Webb 2001 after: ihamäki 2015a). educational geocaching can be based on caches set up earlier by ‘regular’ geocachers or prepared by educators only for classes of specific topics. It may be realized within formal and non-formal education, in both natural and fully anthropogenic landscapes. For its wider implementation into educational received: 16.11.2019 r., accepted after revision: 12.02.2020 r. © 2020 e. referowska-chodak practice in Poland – especially forest education – it speaks of a number of advantages of this form of education, realized successfully outside the country, and in the initial phase in Poland (www.pcen.pl; http://sodmidn.kielce.eu). to the most important advantages included can be: positive evaluation of field classes by the students (Christie 2007; Freiermuth 2017); creating responsibility for the environment (adanali, Alim 2017; Grau Martínez 2017); running classes in dynamic, activating, creative way (Vitale et al. 2012; Zecha 2012); increasing recipients’ involvement in education process (Größ 2010; Mayben 2010); increasing motivation of students (Donadelli, rocca 2014; ring 2014); transferring multidisciplinary knowledge and skills (Zemko et al. 2016; Pombo et al. 2017); E. Referowska-Chodak / Leśne Prace Badawcze, 2020, Vol. 81 (2): 81–90 82 • What about? What is the possible thematic scope of education using geocaching? What subjects/issues were formulated for discussion during classes? Are any fields of study more popular than other ones? in subsection dedicated to recipients of education used was age division for school stages most frequently listed in the cited publications. it is a division dominant in the Usa (where majority of publications originated), but also for instance in canada, india or australia (http://en.wikipedia.org/wiki/K-12). Due to different systems of education in particular countries, it was not always possible to precisely allocate defined in publication recipients into mentioned age groups. therefore, if age group from the publication balanced between groups given in the results, publication was cited in both age groups. in table 1, the adopted age division was related to the Polish education system functioning in the 20th century; therefore, in the period of described experience in educational geocaching. adopted in results, the age division (table 1) is more similar to division in present, recently implemented, Polish education system; however, due to data accessibility, in discussion presented were the chosen statistical references to the previous system in which gymnasium functioned. in the subsection dedicated to the locations of education, compared were anthropogenic, cultural and natural places/ environments in which authors of cited publications proposed the use of already existing or creating new caches and trails of educational geocaching. in the cited publications, the most frequently included were descriptions of specific situations, classes, not general assumptions for this method of education. that is why, the list may seem quite short, and some categories of locations may potentially overlap in space like a hill with forest area. they were however listed separately in order to present the widest possible spectre of locations/environments, which in the cited sources were described as locations of practical experiences. in reference to the content of educational geocaching, it should be noticed that the information given in the publica- developing thinking and problem-solving skills (ihamäki 2007a; Zecha 2012); increasing effectiveness of education in comparison to the indoor education (Ihamäki 2015a; Blažek et al. 2016); teaching cooperation within team (ring 2014; schaal, lude 2015); including physical activity into teaching process (adanali, alim 2017; Pombo et al. 2017). those issues were described in detail in the first part of the cycle (referowska-chodak 2020). the aim of this publication – second one in cycle – is the definition of recipients, locations and scope/subject matter of education using geocaching. Presented information, described on the basis of foreign experience, may have practical meaning while implementing educational geocaching in Poland, also within forest education. 2. Methodology Detailed description of methodology, which is common for the entire cycle of articles, was presented in the first part entitled ‘Geocaching in education – a review of international experiences. Part 1 Introduction: advantages and problems’ (Referowska-chodak 2020). Presented there was an attempt to answer a question – why? Why is it worth to pay attention to this method of education and try to implement it into Polish realities? results of this article were elaborated on the basis of 42 publications sought for in March 2019 in Scopus base of scientific publications (www.scopus.com) and in Google scholar base (http://scholar.google.pl). it was reviewed for answers for the following important questions in education: • For whom? What age groups are mentioned in the cited publications? Which one of them is mentioned most frequently, what may indicate on special utility of this method for running classes? should any of the groups be omitted? • Where? What locations/environments were so far practically used in educational geocaching? are these objects anthropogenic, natural, or maybe places of connection of both in form of cultural landscapes? Table 1. Main age groups of education recipients abroad and in Poland education stage Foreign (e.g. Usa) Poland (before the reform) Poland (after the reform) Pre-school stage 5–6 years* 3–6 years 3–6 years First stage 6–9 years 7–9 years (cl. 1–3) 7–9 years (cl. 1–3) second stage 10–13 years 10–12 years (cl. 4–6) 10–14 years ( cl. 4–8) 13–15 years (gymnasium) third stage 14–17 years 16–18/19 years (high school) 15–18/19 years (high school) 19 years and more 19 years and more adults (including students) 18 years and more *for such age (the earliest) examples of geocaching classes were given E. Referowska-Chodak / Leśne Prace Badawcze, 2020, Vol. 81 (2): 81–90 tions had a radically different level of detail (specific topic or very wide range of content), but it was also extremely different in terms of fields. The following assumptions were adopted for their ordering: 1) information was presented from general to specific (firstly given was information of collective nature, then this which could be assigned to specific fields, then to subject/section, and in the end, the one which within the given field/subject/section was reported as a specific topic), 2) fields of science were divided according to the current Regulation of Minister of Science and Higher Education (Regulation/Rozporządzenie 2018a). 3. Results 3.1. The recipient of education recipients of education with the use of geocaching are: • Younger kids (age: around 5–6 years) (Bragg et al. 2010 after: ihamäki 2015a; ring 2014), • Pupils of the first stage of education (age: around 6–9 years) (christie 2007; ihamäki 2007a, 2014; White–taylor, Donellon 2008; Hamm 2010; Huang et al. 2010 after: Albach 2014; Burri Gram-Hansen et al. 2013; Hall, Bush 2013; Donadelli, Rocca 2014; Ring 2014; Schaal, Lude 2015; Blažek et al. 2016; Adanali, Alim 2017; Donadelli 2017; Grau Martínez 2017; Pombo et al. 2017, 2018), • Pupils of the second stage of education (age: around 10–13 years) (Lary 2004 after: Hamm 2010; Christie 2007; White-taylor, Donellon 2008; Bragg et al. 2010 after: Ihamäki 2015a; Hamm 2010; Huang et al. 2010 after: Albach 2014; Mayben 2010; March 2012; Vitale et al. 2012; Zecha 2012; Burri Gram-Hansen et al. 2013; Hall, Bush 2013; alabau subich 2014; Donadelli, rocca 2014; ring 2014; Heikkinen, Maliniemi 2015; Schaal, Lude 2015; Blažek et al. 2016; Zemko et al. 2016; Adanali, Alim 2017; Grau Martínez 2017; Pombo et al. 2017, 2018), • Pupils of the third stage of education (age: around 14–17 years) (christie 2007; ihamäki 2007a; inman et al. 2008 after: Hamm 2010; White-Taylor, Donellon 2008; Größ 2010; Hamm 2010; March 2012; Vitale et al. 2012; Zecha 2012; Cardwell 2013; Hall, Bush 2013; Alabau Subich 2014; Donadelli,Rocca 2014; Heikkinen, Maliniemi 2015; Ramirez Davies 2015; Schaal, Lude 2015; Blažek et al. 2016; Zemko et al. 2016; adanali, alim 2017; Pombo et al. 2017, 2018), • adults: ◦ students (age: around 18–22 years) (Webb 2001 after: ihamäki 2014; christie 2007; ihamäki 2007a, 2007b, 2015b; lawrence, schleicher 2008 after: ihamäki 2015a; Matherson et al. 2008 after: Ihamäki 2014; White-Taylor, Donellon 2008; Hamm 2010; Dwyer, Mccourt 83 2012; Albach 2014; Donadelli, Rocca 2014; Heikkinen, Maliniemi 2015; Maman, Blumberg 2015; Schaal, Lude 2015; Blažek et al. 2016; Fenech et al. 2017; Freiermuth 2017; Lazar et al. 2018), including candidates for teachers (Vitale et al. 2012; adanali, alim 2017), ◦ other adults (for instance members of communities, clubs, unions) (christie 2007; Blanco, adam 2013; albach 2014; schaal, lude 2015), especially up to 70 years old (schaal, lude 2015), retirees (ihamäki 2007a), teachers – in case of caches set up by students for practice (ihamäki 2007a, 2007b), • cross-sectional groups of society (albach 2014; larsen et al. 2014; ihamäki 2015a), including families with children (schaal, lude 2015). 3.2. Location of education on the basis of literature review, listed below locations were used for education with the use of geocaching: • Museum complex (Blanco, Adam 2013; Burri Gram -Hansen et al. 2013), • School/university complex, including garden, school court (christie 2007; ihamäki 2007b; White-taylor, Donellon 2008; Größ 2010; Lo 2010; Mayben 2010; Cardwell 2013; alabau subich 2014; albach 2014; Donadelli, rocca 2014; Ramirez Davies 2015; Zemko et al. 2016; Adanali, Alim 2017; Donadelli 2017; Freiermuth 2017; Grau Martínez 2017), closest surrounding of school (Größ 2010; Alabau subich 2014), • Historical locations (Dixon 2007 after: Mayben 2010; Dobyns et al. 2008 after: ihamäki 2014), • Urban area (White-Taylor, Donellon 2008; Größ 2010; Vitale et al. 2012; Zecha 2012, 2016; Blanco, adam 2013; Burri Gram-Hansen et al. 2013; Albach 2014; Ihamäki 2014, 2015a; Heikkinen, Maliniemi 2015; Blažek et al. 2016; Freiermuth 2017), • Airport area (Hubackova 2018), • Camping area (Heikkinen, Maliniemi 2015), • Urban park (Shaunessy, Page 2006 after: Mayben 2010; White-Taylor, Donellon 2008; Mayben 2010; Zecha 2016; Donadelli 2017; Pombo et al. 2017, 2018), • Botanical garden (albach 2014), arboretum (larsen et al. 2014), • Zoo (Dixon 2007 after: Mayben 2010), • Cultural landscape (Dwyer, Mccourt 2012), • Protected area: national park (White-taylor, Donellon 2008; albach 2014), an object covered with nature park protection area (Blažek et al. 2016), biosphere reserve (Zecha 2012), nature reserve (albach 2014), • Forest area (Größ 2010; Alabau Subich 2014; Ring 2014; Heikkinen, Maliniemi 2015; Grau Martínez 2017), 84 E. Referowska-Chodak / Leśne Prace Badawcze, 2020, Vol. 81 (2): 81–90 • Valley of a river/canal (Zecha 2012, 2016; Grau Martínez 2017), surroundings of a lake (Größ 2010; Heikkinen, Maliniemi 2015), • A hill (Größ 2010), • Archeological site/park (Etxeberria et al. 2012; Albach 2014), ruins (Größ, 2010), • closed mine (cardwell 2013), geological objects (Lazar et al. 2018). Besides the above listed physical locations, virtual places of geocaching education can be also mentioned. they can be an internet site of a cache – it includes information passed by cache’s creator, but also allow finders to describe their experience, which may also be of a great meaning for increasing the level of knowledge of following finders (Ihamäki 2007a). 3.3. Scope and subject of education the authors of publication are paying attention on usefulness of geocaching in education in the field of: • all program contents (christie 2007), school curriculum (Hamm 2010; Mayben 2010; Lo 2010; Vitale et al. 2012; alabau subich 2014; Donadelli, rocca 2014; ring 2014; ihamäki 2015a; Pombo et al. 2017, 2018); however, with the inclusion of recipients’ relations with every-day life, especially the young ones (Zecha 2012), • getting to know the world in which recipients live (christie 2007; cardwell 2013; Zecha 2016), • science and natural science: ◦ science (Brown et al. 2003 after: Mayben 2010; Christie 2007; Dixon 2007 after: Mayben 2010; Vitale et al. 2012; Donadelli, rocca 2014; larsen et al. 2014; ihamäki 2015b; Zemko et al. 2016; adanali, alim 2017), ◦ natural science (Pérez, Pérez 2012 after: Alabau subich 2014; alabau subich 2014; Zemko et al. 2016; Grau Martínez 2017), ◦ mathematics (Lary 2004 after: Hamm 2010; Sherman 2004; elwood 2005 after: alabau subich 2014; Schlatter, Hurd 2005 after: Mayben 2010; Christie 2007; Buck 2009 after: Mayben 2010; Stephens 2009 after: Hamm 2010; Bragg et al. 2010 after: Ihamäki 2015a; Lo 2010; Pérez, Pérez 2012 after: Alabau Subich 2014; Vitale et al. 2012; cardona 2013 after: alabau subich 2014; alabau subich 2014; Donadelli, rocca 2014; larsen et al. 2014; Ihamäki 2015a, 2015b; Blažek et al. 2016; Zemko et al. 2016; Adanali, Alim 2017; Grau Martínez 2017): distance, angles, coordinates, conversion, measures, problem-solving and so on. ◦ physics (Lo 2010; Alabau Subich 2014; Blažek et al. 2016), ◦ chemistry (lo 2010), ◦ biology (natural history) (Vitale et al. 2012; alabau Subich 2014; Ring 2014; Ihamäki 2015a; Blažek et al. 2016), including observing/recognizing animals (Christie 2007; Anderson 2008 after: Mayben 2010; Zecha 2012), soils (christie 2007), trees/plants (sherman 2004; christie 2007; Anderson 2008 after: Mayben 2010; Huang et al. 2010 after: albach 2014; schäfer 2010 after: Zecha 2012; March 2012; Zecha 2012; Cardona 2013 after: Alabau subich 2014; albach 2014; larsen et al. 2014; Zemko et al. 2016; Pombo et al. 2017, 2018), water habitats (Zecha 2012), ecology (sherman 2004; lo 2010), nature protection (Zecha 2012; Pombo et al. 2017, 2018), ecosystem, habitats, population, food chain (Grau Martínez 2017), ◦ geology (sherman 2004; anderson 2008 after: Mayben 2010; White-Taylor, Donellon 2008; Lo 2010; cardona 2013 after: alabau subich 2014; cardwell 2013; Lazar et al. 2018), ◦ geography (sherman 2004; shaunessy, Page 2006 after: ihamäki 2015a; christie 2007; ihamäki 2007a, 2007b, 2014, 2015b; lawrence, schleicher 2008 after: ihamäki 2015a; White-taylor, Donellon 2008; lo 2010; Mayben 2010; Alabau Subich 2014; Donadelli, Rocca 2014; Ring 2014; Blažek et al. 2016; Adanali, Alim 2017; Donadelli 2017): coordinates and geographical directions, spatial orientation (Schlatter, Hurd 2005 after: Mayben 2010; Kerski 2006 after: ihamäki 2015a; christie 2007; Ihamäki 2007b; Swingle 2007 after: Ihamäki 2015a; Matherson et al. 2008 after: Vitale et al. 2012; White-taylor, Donellon 2008; Mayben 2010; Vitale et al. 2012; Zecha 2012; alabau subich 2014; Donadelli, rocca 2014; ring 2014; Ramirez Davies 2015; Schaal, Lude 2015; Blažek et al. 2016; Zemko et al. 2016; adanali, alim 2017; grau Martínez 2017), local region (Sherman 2004; Vitale et al. 2012; Ring 2014; Heikkinen, Maliniemi 2015; Ihamäki 2015a; Blažek et al. 2016), sudden atmospheric phenomena (adanali, alim 2017), erosion (Zecha 2012, 2016), rivers (Zecha 2012, 2016), meteorological observations (Stephens 2009 after: Hamm 2010; Cardona 2013 after: alabau subich 2014), the universe (stephens 2009 after: Hamm 2010), continents (Ring 2014), landscape (Anderson 2008 after: Mayben 2010; Vitale et al. 2012; Ihamäki 2015a; Zecha 2016) and its interpretation (Zecha 2016), maps (sherman 2004; alabau subich 2014; Donadelli, Rocca 2014; Ring 2014; Grau Martínez 2017), digital cartography (cardona 2013 after: alabau subich 2014; Donadelli, rocca 2014; ring 2014), different coordinates (Alabau Subich 2014, Ramirez Davies 2015), scale (Grau Martínez 2017), orography (Grau Martínez 2017), • Social science (shaunessy, Page 2006 after: ihamäki 2015a; Christie 2007; Matherson et al. 2008 after: Mayben 2010; White-Taylor, Donellon 2008; Mayben 2010; Vitale et al. 2012; cardona 2013 after: alabau subich 2014; alabau subich 2014; Donadelli, rocca 2014; ring 2014; adanali, Alim 2017; Fenech et al. 2017; Grau Martínez 2017): E. Referowska-Chodak / Leśne Prace Badawcze, 2020, Vol. 81 (2): 81–90 ◦ journalism (ihamäki 2007b) – for instance by creating one’s own reportage on geocaching (Ihamäki 2007a; Freiermuth 2017), ◦ policy (Mayben 2010), forming, changes and cooperation of individuals and society (ring 2014), territorial/administrative division (Grau Martínez 2017), ◦ economy (Mayben 2010), local economy (Cardwell 2013), local natural resources (cardona 2013 after: alabau subich 2014), socio-economy, local living conditions (Blažek et al. 2016), local community (Vitale et al. 2012; Ring 2014), realized professions/occupation (Ring 2014), ◦ changes in local landscape (ihamäki 2014), ◦ ecological and environmental education (ihamäki 2007a; Zecha 2012; cardona 2013 after: alabau subich 2014; ihamäki 2014; adanali, alim 2017), among others things, threats for the environment (adanali, alim 2017), rules, perspective and own participation in sustainable development, environment protection (ring 2014; schaal, lude 2015), interaction between man/environment and nature (ring 2014), ◦ physical education (sports education) (schlatter, Hurd 2005 after: Mayben 2010; Ihamäki 2007b, 2015a; Dobyns et al. 2008 after: Hamm 2010; White-Taylor, Donellon 2008; Größ 2010; Lo 2010; Moss 2010 after: Vitale et al. 2012; Vitale et al. 2012; cardona 2013 after: alabau subich 2014; alabau subich 2014; ring 2014; grau Martínez 2017), tourism, including ecotourism (Zecha 2012), healthy lifestyle (Grau Martínez 2017), • Humanities: ◦ cultural landscape (schäfer 2010 after: Zecha 2012; Dwyer, Mccourt 2012; Ring 2014; Ihamäki 2015a; Zecha 2016), ◦ ethnography (Blažek et al. 2016), local customs/culture (Vitale et al. 2012; Zecha 2012; Blanco, adam 2013; Ring 2014; Heikkinen, Maliniemi 2015; Pombo et al. 2017, 2018), cultures of other societies (Lo 2010; Mayben 2010), beliefs/religions (Pérez, Pérez 2012 after: Alabau Subich 2014; Ring 2014; Heikkinen, Maliniemi 2015), ◦ history (elwood 2005 after: alabau subich 2014; Schlatter, Hurd 2005 after: Mayben 2010; Dobyns et al. 2008 and Matherson et al. 2008 after: Ihamäki 2014; Inman et al. 2008 after: Hamm 2010; Lo 2010; Zecha 2012; Alabau Subich 2014; Ring 2014; Blažek et al. 2016; Zemko et al. 2016): local history, including historical objects (ihamäki 2007a, 2014, 2015a, 2015b; Kerski 2007 and swingle 2007 after: ihamäki 2015a; schäfer 2010 after: Zecha 2012; Vitale et al. 2012; cardona 2013 after: alabau subich 2014; cardwell 2013; Donadelli, Rocca 2014; Ring 2014; Heikkinen, Maliniemi 2015; Blažek et al. 2016; Pombo et al. 2017, 2018), historical figures (Burri Gram-Hansen et al. 2013; Cardona 2013 after: Alabau Subich 2014; Blažek et al. 2016), 85 ◦ archeology (Etxeberria et al. 2012), ◦ knowledge of foreign languages (ihamäki 2007a, 2007b; Ramirez Davies 2015; Zemko et al. 2016; Freiermuth 2017; Hubackova 2018), knowledge of one’s own language, speaking and writing skills (Dixon 2007 after: Mayben 2010; Pérez, Pérez 2012 after: Alabau Subich 2014; Donadelli, rocca 2014; ihamäki 2015a; grau Martínez 2017), for instance description of one’s own experience in searching a cache (Dobyns et al. 2008 after: ihamäki 2014; White-taylor, Donellon 2008; lo 2010; Vitale et al. 2012; cardona 2013 after: alabau subich 2014; ihamäki 2015a) or description/history connected with setting up a cache (ihamäki 2015b), toponomy (cardona 2013 after: alabau subich 2014), ◦ knowledge of the literature (Pérez, Pérez 2012 after: Alabau Subich 2014; Burri Gram-Hansen et al. 2013), • Art: ◦ artistic issues (ihamäki 2007a), for instance photography (ihamäki 2007a, 2007b), plasticity (alabau subich 2014), • Engineering and technical science (alabau subich 2014; larsen et al. 2014): ◦ modern technologies, including system and use of gPs (Webb 2001 after: ihamäki 2014; sherman 2004; elwood 2005 after: alabau subich 2014; christie 2007; Ihamäki 2007a, 2007b; Mayben 2010; Vitale et al. 2012; Maman, Blumberg 2015; Ramirez Davies 2015; Blažek et al. 2016), ◦ magnetic fields, radio waves (Sherman 2004), ◦ technical objects in the surroundings (schäfer 2010 after: Zecha 2012), ◦ navigational information and internet communication, information and communication technology (Webb 2001 after: ihamäki 2014; alabau subich 2014), ◦ operation of device like compass, gPs receiver (sherman 2004; lawrence, schleicher 2008 after: Ihamäki 2015a; Mayben 2010; Alabau Subich 2014; Donadelli, rocca 2014; ring 2014; Zemko et al. 2016). 4. Discussion and summary As was emphasized in the introduction, education using geocaching has a lot of advantages, and especially valuable is – in majority of cases – the one increasing the effectiveness of education (Mayben 2010; Tozo 2011 and Ulukök 2012 after: adanali, alim 2017; ring 2014; ihamäki 2015a; Blažek et al. 2016; Kisser 2016). That is why, it is worth taking a look at foreign experience in this matter, by analysing in the beginning such practical aspects as: recipient, location and scope/subject matter of education, referring at the same time to the Polish realities. 86 E. Referowska-Chodak / Leśne Prace Badawcze, 2020, Vol. 81 (2): 81–90 as recipients of education using geocaching the authors of the analysed foreign publications indicated practically all age groups. However, most frequently mentioned were students and pupils, especially from 10–18 years age group (corresponding to our present classes from 4th grade in primary school to 4th grade in high-school). it results from the fact that authors of those publications were in majority teachers from primary and high-schools and also academic teachers describing their experience with learned by them (respectively) pupils or students. Other configurations occurred rarely, for instance, academic teacher organizing classes for pupils of primary school (for instance ihamäki 2014; Zecha 2012). authors of the cited publications were also students and PhD students of teaching and social majors (Mayben 2010). Few were publications also referred to non-formal education organized by employees of botanical gardens, urban parks or youth centres (March 2012; Albach 2014; Heikkinen, Maliniemi 2015; Pombo et al. 2017, 2018). it does not mean, however, that education using geocaching is less suitable for non-formal education. it probably means that non-formal educators are less willing to publish their experience than formal educators. Basically, in order to run such education, one needs to have willingness and conviction to go outdoor with students/recipients of education. in Polish realities – as was mentioned in the first part of the cycle of articles – it quite often meets reluctance from school teachers (referowska-chodak 2013), and very often, is realized by non-formal educators, among others, from the state Forests, national and landscape parks, centres for ecological education and non-governmental organizations. In case of education run by centres for ecological education and non-governmental organizations, there is no collective information on the number and age structure of participants. in case of landscape parks, such collective information is not published. in 2003, researches were conducted in 21 parks, from which resulted that 80,000 persons benefited from the education run by employees of parks (while field classes covered around 20,000 persons). Mainly they were pupils of primary schools, gymnasia, technical high-school and high-schools (sikora-stachurska 2007). if these data were to be interpolated to all current landscape parks (123), it would have been around 469,000 participants of education. it should be remembered, however, that changes in law and organization that occurred in 2008, caused reduction in the number of park employees (Kistowski 2012), therefore, also the possibilities of running educational classes. in case of education run in national parks, the available data are not unified. On one hand, information is published on the number of visitors of museums and educational centres – slightly over 1 million people in 2018 (environment Protection/ochrona Środowiska 2019); on the other hand – information on the number of didactic events – 5,277 in 2018 (environment Pro- tection/Ochrona Środowiska 2019), without providing the number of their participants. the age structure of education recipients is also unknown. among non-formal educators, the state Forests offer the most complete data. in 2017, on 2,337,597 participants of education run by foresters, 18.52% were pre-schoolchildren aged 3–6 years, 31.40% – kids from primary schools (7–12 years old), 11.97% – gymnasium youth (13–15 years old), 6.82% – over-gymnasium youth (16–19 years old) and 31.28% – students and adults (over 19 years old) (Mrowińska 2018). However, in the cited year, on field classes and trips with a guide, the most numerous group was students and adults (42.37%), then children from primary schools (28.06%) and kindergartens (16.47%), and the least numerous – over-gymnasium youth (4.02%) and gymnasium youth (9.07%) (Mrowińska 2018). Due to the fact that the oldest age group is not divided into students and other adult persons, it creates a sort of a problem in reference to the presented results, in which students are important recipients of educational geocaching. Presented statistics of education in the state Forests allow to make two observations. First one is quite a large share of kindergarten groups, which – in case of education using geocaching – were quite rarely mentioned and it referred mainly to 6-year old children, so the oldest ones. it results from the ability to understand the course of classes or to operate the equipment needed for tracking caches. Mentioned were however (in the results) families with children, but in this case, equipment managing can be realized by the adults. It seems, therefore, that in terms of this age group (especially youngest children) current educational model should be realized. Second observation concerns gymnasium and over-gymnasium groups, which relatively rarely use education run by foresters from the state Forests, while in case of educational geocaching (outside Poland) are most frequently indicated as its participants. situation in Poland (in the state Forests) may result from overload of the curriculum on higher levels of education and difficulties with finding time for going out with students and reaching foresters. On the other hand, it is also quite ‘difficult’ group (in comparison to pre-schoolers) usually living in its own virtual world, group that is hard to get connection with (referowska-chodak 2013). that is why especially for those age groups, geocaching seems to be a great solution, for instance during residential school trips. It finds confirmation also in the observations from other countries: way of people’s learning evolved in the last decades very intensively (Hamm 2010). this entails a need for searching new ways of forming level of knowledge, awareness and skills, especially among younger recipients of education. it should be noticed, that modern students are no longer so engaged and motivated by traditional model of learning as previous generations (Prensky 2006 after: Mayben 2010). In their case on motivation for E. Referowska-Chodak / Leśne Prace Badawcze, 2020, Vol. 81 (2): 81–90 learning and its results influences positively the use of modern technologies (Hsieh et al. 2008 after: Mayben 2010). Lessons are considered to be less boring then (Deaney et al. 2003 and Downes, Bishop 2009 after: Mayben 2010). It is also thought that ‘technological gadgets’ like smartphones, used in educational geocaching, become modern connector between young people and the nature (Hartl 2006 after: Zecha 2012). second practical aspect of education using geocaching, discussed in this article is a location. Presented in the results, foreign experience focus foremost on anthropogenic places. these are school/university grounds and urban areas, including parks (that could also be widely used in formal education in Poland). it results from the aforementioned fact that the authors of majority of publications are school or academic teachers, who usually tried to run classes ‘nearby’, and not wasting time for distant trips (shaunessy, Page 2006 after: Mayben 2010). It is particularly frequent with so called instructional geocaching, where the transferred content does not have to be connected with the place of hiding the cache (for instance Christie 2007; Mayben 2010). It can be an idea for similar classes in Poland, for instance, in the surrounding of headquarter of forest inspectorates or national park objects, when time of classes is limited and does not allow for travelling a longer route. However in standard geocaching, caches are localized in special places, which are attractive in terms of history, culture or nature (Schneider, Jadczaková 2016). among the last ones, the authors list areas of protected nature, places by watercourse/reservoirs, geological objects, but also forest areas, although in case of the last ones they are often considered as a place of touristic geocaching rather than educational (ihamäki 2015a). it seems, however, that in Poland, educational geocaching in forests has much bigger chances and possibilities of coming into being. this is due to the fact that the Polish forests are in great measure under management of the State Forests National Forest Holding, whereas some of them are within boundaries of landscape parks. Part of the remaining forests are within boundaries of national parks. noticed should be, however, that within duties of both employees of the State Forests (Ordinance/Zarządzenie 2003), national parks and landscape parks (act/Ustawa 2004 – art. 103.2.2 and 107.2.6) is realization of education of society. Written in the directions of development of forest education in the state Forests assignment of ‘evaluation of educational experiments and their implementation into practice’ (Ordinance/Zarządzenie 2003 – attachment 1) may be a basis for implementing educational geocaching by foresters. Already now the Polish forests are recognized (and used) for their educational value – this purpose serve, among others, developed and realized programs of ecological or forest education in national and landscape parks, in the state Forests, but also in urban forests. For inclusion of the earlier mentioned 87 values, being expanded is field educational infrastructure, for instance didactic trails (Mrowińska 2018; Environment Protection/Ochrona Środowiska 2019). Collected experience and prepared trails may be adapted and used for running education with the use of geocaching. closeness of big, busy road is considered to be a not very attractive place of hiding the caches (Schneider, Jadczaková 2016). That is why, in the Polish forests, it is worth using for this purpose numerous, and at the same time much more intimate, didactic trails, tourist routes or other elements of infrastructure mentioned before. such a solution may limit the problem of loss in animate and inanimate nature, connected with visiting distant caches, which in first article was considered as a problem of education using geocaching (Patubo 2010 after: Zecha 2012; Zecha 2012). additional educational advantage of the Polish forests is the number and variety of forms of nature protection. object (and subject) of education run by foresters in the state Forests are 700 nature reserves (Mrowińska 2018), but also numerous ecological sites, natural monuments or areas of natura 2000 protection. employees of national and landscape parks also run education according to form and regime of nature protection being a subject matter and their place of work. Placing caches within boundaries of protected areas or generally in forests requires, however, obeying applicable restrictions (act/Ustawa 1991, act/Ustawa 2004). in national parks and nature reserves, it is forbidden to step off the trail (act/Ustawa 2004 – art. 15.1.15). it is recommended to clearly mark, that to geocachers apply terms of use protected areas as it does to other tourists (Schneider, Jadczaková 2016). third practical educational aspect of geocaching is the thematic scope of classes. as can be noticed on the basis of review of foreign experience, it is very wide. It provides even an opportunity to realize every content of the curriculum, although especially often mentioned are: geography, mathematics, biology/natural history, history, culture, ecological education, modern technologies/equipment (especially gPs), linguistics and physical education. Presented in the results, the scope of education realized abroad is consistent with the scope of formal education in Poland (among others, Regulation/Rozporządzenie 2017, 2018b). It is an argument for implementing educational geocaching also in our country, within formal education (school education), but also non-formal education, including forest education. theoretically, the content of forest education run in the state Forests include structure and functioning of forest ecosystems, meaning of forest (ecological, economic and social), threats and protection of forests, nature protection and challenges for foresters and forestry (Ordinance/Zarządzenie 2003 – att. 2), that is a narrower range than the potential one. However, it should be emphasized that in the directions of forest education development written was the sentence ‘per- E. Referowska-Chodak / Leśne Prace Badawcze, 2020, Vol. 81 (2): 81–90 88 fecting educational program in cooperation with educational institution for providing consistency of school and educational programs’ (Ordinance/Zarządzenie 2003 – att. 1). It allows for including in the classes run by foresters also those subjects that are not directly mentioned in the basic scope of forest education. additionally, in the same document, a statement was included of a need to ‘create programs developing interdisciplinary approach to forest environment and economy in forests, combining knowledge and skills from many fields of science and practice’. This is a part of the concept of integrated education, described already in 2003 by forester-educator Andrzej Antczak in the context of building educational trails. according to him, classes on the trail, beside raising environmental and forest-economy related issues, may introduce topics from ‘geography, literature, history, chemistry, mathematics or art, e.g., plastics (…) and music’ (Antczak 2003). It should be emphasized that forests in Poland are especially complex and valuable environment for teaching, rich not only in terms of nature but also in terms of history and culture. they allow, therefore, for running interdisciplinary classes, including – prospectively – also classes using geocaching. this situation refers to not only the forests under management of the state Forests (including landscape parks), but also the forests within the borders of national parks and urban forests where society’s education is being run. in case of education run by employees of landscape parks, the need for promoting not only nature content, but also historic and culture value of the park is pointed out (act/Ustawa 2004 – art. 107.2.6). in case of national parks, only education in terms of nature protection is mentioned (act/Ustawa 2004 – art. 103.1.2); however, due to the fact that park is being created due to cultural values of given area (act/Ustawa 2004 – art. 8.1), in practice, those values (also historical) are also promoted (Andrzejewska et al. 2013). To sum up, international experience concerning recipients of educational geocaching indicate on one hand on certain limits in its use in the youngest age groups, but on the other hand – on its high usefulness in education of remaining age groups, especially school and students. among the listed locations of education, dominant were anthropogenic ones. However, in Poland, at widely developed non-formal education, added to them can be numerous natural objects (for instance, forest areas), which are already used as places of field education. They allow for running multidisciplinary education that falls within the wide scope of content proposed by the authors of foreign publications for realizing when using geocaching. Conflict of interest The author declares lack of potential conflicts. Acknowledgements and source of funding own research within statutory activity. Bibliography Adanali R., Alim M. 2017. 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Strony internetowe http://en.wikipedia.org/wiki/K-12 – strona internetowa angielskiej Wikipedii opisująca system edukacji w USA, do którego podobne są systemy m.in. w Kanadzie, Australii, Indiach i Turcji [ 06.03.2019]. http://scholar.google.pl – serwis przeglądarki internetowej Google, gromadzący publikacje naukowe [05.03.2019]. http://sodmidn.kielce.eu/node/1028 – strona internetowa Samorządowego Ośrodka Doradztwa Metodycznego i Doskonalenia Nauczycieli w Kielcach [05.04.2019]. www.pcen.pl/aktualnosci-pcen/aktualnosci-rzeszow/item/402-zapraszamy-na-bezplatne-szkolenie-geocaching-czyli-nauka -poprzez-zabawe.html – strona internetowa Podkarpackiego Centrum Edukacji Nauczycieli w Rzeszowie z ofertą szkolenia o geocachingu [04.04.2019]. www.scopus.com – internetowa baza danych publikacji naukowych, prowadzona przez wydawnictwo Elsevier [04.03.2019]. DOI: 10.2478/frp-2020-0010 Wersja PDF: www.lesne-prace-badawcze.pl Leśne Prace Badawcze / Forest Research Papers Czerwiec / June 2020, Vol. 81 (2): 91–98 reVieW article e-ISSN 2082-8926 Site index research: a literature review Wojciech Kędziora* , Robert Tomusiak , Tomasz Borecki Warsaw University of life sciences – sggW, institute of Forest sciences, Department of Forest Management Planning and Forest economics, ul. nowoursynowska 159; 02–776 Warsaw, Poland *Tel. +48 22 5938204, e-mail: wojciech.kedziora@wl.sggw.pl Abstract. the purpose of this paper was to review literature covering the topic of site index with particular emphasis on scots pine, the most important forest-forming species in Poland. We discuss the history of the site index, research on various tree species, statistical modelling methods, the spatial application of site index and age impact assessment. the history of research on the site index of forest species is long and dates back to the 18th century. Many researchers thought that determining the quality of the habitat is very important from the point of view of rational forest management. the site index, as a measure of the potential of the habitat on which the forest grows, is one of the most important characteristics of forest stands. the site index depends on the selected model, but is most often expressed as the average or top height of trees of a given species at a certain age. In our review, we point out several insufficiencies of studies on the site index, external influences and the connection of the site index with spatial conditions. Furthermore, research conducted so far has not explicitly confirmed that there is a relationship between the site index of pine stands and their geographical location in Poland. More research on the site index, especially in regard with climate change, is needed. Keywords: Forest site index, tree growth, forest site quality, forest site productivity 1. Introduction the dynamic changes taking place in the availability of information enable research to be conducted at an increasingly wider scale. Modern methods of collecting field data from a large number of sample plots has allowed many problems, which until recently were unanswered, to be solved. One of such important scientific problems for forestry is the more complete characterization of the site index and the attempt to spatially characterize forest growth based on this feature. all tree species are equally important in the biocenosis, but from an economic point of view, some are given priority. in Poland, among all forest-forming species, the scots pine Pinus sylvestris l. deserved and deserves special recognition. Due to the existing soils and climate forming the habitat, pine is the most common species in Polish forests. received: 27.02.2020 r., accepted after revision: 2.04.2020 r. © 2020 W. Kędziora et al. its value to Polish forestry is increased by the few problems it poses in its management, its high productivity and economic utility. A better understanding of the factors influencing the growth of pine will contribute to enriching the basic knowledge about this species, and thus, allow for more effective management. The site index of a stand, which characterizes the growth potential of the species, is a good measure of the impact of the surrounding environment on the life of trees. a constant site index value over time expresses the consistency of environmental conditions, while its fluctuations indicate that some features of the surrounding ecosystem are changing. Knowing the variability and dependence of the site index on external factors can help in understanding the preferences of pine. this is particularly relevant and important in the current dynamics of climate change associated with its warming. 92 W. Kędziora et al. / Leśne Prace Badawcze, 2020, Vol. 81 (2): 91–98 the aim of this paper is to review the literature on the site index of important forest species, with particular emphasis on pine, the most important forest-forming species in Poland. the current state of knowledge about the site index of pine in Poland seems to be insufficient, and the current possibilities of continuing this research may significantly broaden this knowledge. 2. The evolution of measures of the production potential of the forest research on the site index was conducted as early as in the 18th century by Oettelt (1764), who defined the height of the trees as an indicator of ‘soil goodness’. the 19th century brought the development of forestry science, which changed the approach to the problem of the site index. Heyer was the first to observe the link between height increment and volume growth (heyer 1841). he believed that determining the quality of a habitat is important in terms of its productivity (Heyer 1845). Franz von Baur described average height as the most accurate and only proper indicator, not only for assessing normal stand growth, but also for appraising its site index (Baur 1881). In this method, the site index was categorized into classes, with each class assigned to an equal interval of average height. these intervals increased proportionally with the age of the stand. the graphical interpretation resembled the increasing height of ranges, hence its name – the range method. it assumed that the height of a stand increases in accordance with the determined height change curve, and that stands at a certain age have similar productivity. since then, despite initial scepticism (e.g., hartig 1892), the height site index started to be identified with productivity. this method, called the ‘phytocentric method’, consists of measuring the vegetation growing in a given area (skovsgaard, Vanclay 2008). Unlike the ‘geocentric method’, which is based on the properties of the soil and climate, it is often easier to apply. the phytocentric method usually involves measuring plant yields. this is often practiced in farming, but given the differences between the types of farming and forestry, it is difficult to apply. Annual crop harvests in agriculture makes it possible to make long-term analyses of productivity changes. such a way of experimenting in stands would require many centuries of research. in forestry, an attempt to solve this problem was to measure yield expressed as volume (assmann 1968) or the average total production increment calculated for the age of 100 years (Philipp 1893). at a time when silviculture practice included light thinning, allowing some of the dominated trees in Kraft’s classes 4–5 (Kraft 1884) to re- main in the stand, this method worked well in reflecting the production capacity of the habitat. however, since the use of moderate and strong thinning, there have been instances where the stock levels were lower in a habitat with potentially higher productivity than in one with a lower potential. it turned out that the abundance does not precisely determine the productive potential of a habitat, because the intensity of the treatment had a significant impact on the growth of wood resources – after strong thinning, the potential was often underestimated, whereas with light thinning, it was overestimated (Magin 1958). as a result of searching for a more convenient measure for the site index, average stand height was chosen as a measure that is less affected by external factors. the measurement of the site index using volume is based on the Eichhorn’s Rule (formulated for fir), which states that a certain average stand height for all habitat classes corresponds to the same stand volume (eichhorn 1902). in later years, gerhardt extended this to spruce and pine (gehrhardt 1909, 1921) and reformulated it into the ‘extended eichhorn’s rule’, stating that there is a relationship between productivity and habitat-dependent stand height, which was proven by assmann (1955, 1959). 3. Height site index site index, understood as the height of a stand at a particular age, is today the most common way to assess the quality of a forest habitat. currently, there are two approaches to measuring it and both use an indicator method – you have to measure the sample trees and check which discount they belong to. The first approach involves measuring the average height and assigning it to a specific grade. However, this has some consequences. During natural tree growth, the weakest trees lose the competition and are separated from the stand. these processes are simulated during the tending process. With severe lower thinning, this can lead to a sudden and significant increase in the average height. For example, strong bottom thinning in a 65-year-old stand changes the average height from 24.5 m to 25.9 m, which increases the discount by ½ class (assmann 1968). the second way is based on the determination of the height of the upper stand, understood as the average height of a certain number of the thickest trees on an area of 1 ha. in this case, as a result of thinning or natural processes of tree secretion, there will be only slight shifts in the results of the discount. in the study from the experimental plots in sachsenried 2, it was found that the difference in height between the upper and the average height, with an appropriate intensity of cultivation, may decrease from 2.1 m to 1.0 m W. Kędziora et al. / Leśne Prace Badawcze, 2020, Vol. 81 (2): 91–98 (assmann 1968). Further studies on the application of average and upper altitude showed that for different thinning treatments, differences of up to 3.2 m can be obtained. in both methods, individual variation in height may be a problem. the growth rate deviating from the accepted ‘fan’ of the discount results in its change, usually a decrease of even 0.7 degree of quality. in addition, deterioration of water conditions during stand growth, for example, may cause a reduction of the discount (assmann 1968). it is not only changes in the level of the water table that can affect the amount of the discount. it turns out that the increase in height varies from one climate to another. two types of abundance tables from different regions were compared: hummel and christie (1953) for conifers in Great Britain and Wiedemann (1936) for spruce in Germany and it turned out that their growth rate is different (Magin 1957). it is also problematic that different tables used different number of discount classes as well as different width of compartments characterizing the classes. Schober (after: assmann 1968) proposed that the distances between the different discount classes should be 4 m at the age of 100 (4.5 m for spruce). another proposal was absolute site index (as opposed to class ones), which determined the height of the stand at the felling age. a problem proved to be the assessment of the site index at a possible change of the felling age. Difficulties were also encountered when comparing the absolute tree stand and stand height between the species. an attempt to unify the various proposals was made by Weck’s postulate that the absolute site index should be measured as the average stand height at the age of 100 years (Weck 1948). however, this created the problems discussed earlier. therefore, the assmann proposal is currently the most common form of determining the stand’s site index. this proposal assumes that the site index is the upper height (the height of the 100 thickest trees per 1 ha) at the age of 100 years (assmann 1959). the absolute site index can be adopted for height discounting (assmann 1959; skovsgaard, Vanclay 2008) and at the same time is unambiguous in designation and easy to measure, it can be compared without additional conversions. it should be noted that in forestry, the desired feature to be determined is the habitat classification, determined by means of the stand classification. the latter is burdened with a certain error, for example, inadequate species composition to the habitat or disturbed growth conditions in previous periods (Gieruszyński 1959). From these studies, it results that the stand site index is not adapted to different species of stands, the afforestation coefficient is not taken into account, the site 93 index is not constant and may change over time, the site index for different species cannot be directly compared. it should be remembered that the problem is the precise determination of the stand age. aside from these limitations, the site index is a useful measure to use a simple numerical value that is easy to measure and understand by the practitioner. it will remain in use until it is replaced by a meter without these limitations, the calculation of which will be equally easy (avery et al. 2019). therefore, the site index is most often expressed as the upper height of trees of a given species at a specific age (Bruchwald, Kliczkowska 1997; Bruchwald et al. 1999; sharma et al. 2012; socha et al. 2017). as mentioned earlier, research on the class and absolute site index has been conducted at least since the 18th century. the main effect of these studies is the construction of models of the coefficient of variation (coefficient curves) for different species, for example, Douglas fir Pseudotsuga menziesii (Mirb.) Franco (Monserud 1984; Means, helm 1985; Milner 1992), yellow pine Pinus ponderosa Dougl. ex c. lawson (Milner 1992), West larch Larix occidentalis nutt. (Milner 1992), dune pine Pinus contorta Douglas (Milner 1992), taeda pine Pinus taeda l. (Popham et al. 1979; cao et al. 1997), the long-needle pine Pinus palustris Mill. (cao 1997), california Pinus radiata D. Don (Burkhart, Tennent 1977), Pinus sylvestris L. (Bruchwald, 1979; elfving, Kiviste 1997; socha, eagle 2013), Fagus sylvatica l. beech (nord-larsen 2006), spruce of common Picea abies L. H. Karst (Kliczkowska, Bruchwald 2000; socha et al. 2015) or black alder Alnus glutinosa l. (Socha, Ochał 2017). In the work by Cieszewski and Zasada (2002), a transformation of the Bruchwald’s (2000a) anamorphous site index model was carried out to a dynamic form, which allows to obtain the value of the discount rate for any measured pair ‘age-height’ in a less labour-intensive way. the tables of Szymkiewicz’s affluence were successfully transformed by Cieszewski and Zasada (2003a) into a voucher model. The work by Cieszewski and Zasada (2003b) proposed the use of a universal method of algebraic differences to derive general dynamic discount equations. research on the variability of characteristics of pine trees and stands in Poland, also taking into account the site index, has been conducted for a relatively long time, which determines the potentially large amount of comparative material (Bruchwald 1977; Keller 1991; Bruchwald, Kliczkowska 2000; Socha, Orzeł 2011). The literature clearly shows the trend of research on the pine voucher models themselves, both locally (Sewerniak 2008; Beker, Andrzejewski 2013) and nationally (e.g., Cieszewski, Zasada 2003a). 94 W. Kędziora et al. / Leśne Prace Badawcze, 2020, Vol. 81 (2): 91–98 From similar studies, only those limited to the selected regions can be found in the literature (sewerniak, Piernik 2012; Socha, Orzeł 2013). The previous research on the variability of pine stand site index on the national scale has indicated the necessity to include additional environmental and stand parameters that may potentially affect the variability of pine stand site index (Bruchwald et al. 2000a). The top stand height was studied by Bruchwald (1979), Socha (2005) and Beker (2007). The latter proposed the upper biological height – of the top and dominating trees according to Kraft (1884) – as the most accurate in the entire life of the stand, but difficult to measure due to the high labour intensity. socha and colleagues (2015) in their research developed discount models for basic forest-forming species in Poland (pines, firs Abies alba Mill., ash Fraxinus excelsior l., aspen Populus tremula l., birches Betula l., black alder, oak Quercus l., beech, larch Larix decidua Mill., spruce, acacia Robinia pseudoacacia l., red oak Quercus rubra L., Douglas fir Pseudotsuga carriere, hornbeam Carpinus betulus l., lime trees Tilia l. and maple Acer l.). they have managed to build a mathematical model of the coefficient of discount based on data from the abundance tables used in Poland. For most species, they used a modified model of Cieszewski (Cieszewski, Zasada 2003b), which gave the best results. They also developed discount models for the main forest-forming species in Poland, based on the latest empirical material (socha et al. 2017). in the research carried out in the stands of the southern part of Poland (Socha, Orzeł 2013), a set of dynamic discount curves for pine was developed. What is more, it was noted that the schwappach’s table model (1943) shows a lower growth rate in youth and a higher growth rate in older stands. the mathematical model of Bruchwald (Bruchwald et al. 2000a,b), built according to different principles, shows significant discrepancies between the predicted and actual growth rate. in the research carried out in the niepolomice Forest (Socha, Orzeł 2011), a local, dynamic system of site index curves was developed. the research was extended in subsequent years to include stands from southern Poland (Socha, Orzeł 2013), as well as to the work on the inclusion of an increase in altitude or discount in the mathematical framework was carried out by Stępień (1979), who, using electronic calculation techniques, determined the coefficients of the equation for calculating discount depending on age for pine, fir, spruce, beech and oak. similar studies were also conducted by socha (1997) and Jarosz and Kłapeć (2002). 4. Statistical modeling of site index the analysis of the site index was also carried out in methodological works, focusing on the evaluation of the usefulness of various statistical methods in modelling the value of this feature. in subedi and Fox’s work (2016) focusing on the influence of soil traits on the site index of P. taeda pine, the use of multiple and partial regression of the smallest squares was compared. Wang and colleagues (2005) investigated the spatial dependence of the site index on environmental factors in canada using various statistical techniques. in their case, the best technique, also dealing with unusual data values, was the technique of generalized additive models (gaM). similar conclusions have been reached by researchers dealing with site index in Turkey's mountains (Aertsen et al. 2010). In the Czech Republic and slovakia, neural networks were used with prediction of the site index based on climatic data for spruce, beech and fir (hlásny et al. 2017). in a study from the Western United states (latta et al. 2009), data from the large-area Forest inventory were used to model the impact of climate variables on potential stand productivity. Wang (2005) compared four modelling methods (non-linear regression, decision tree, generalised additive models and neural networks) of spatial variability of the site index of Pinus contorta Dougl dune pine. ex loud. in canada’s mixed boreal forest. the possibility of using remote sensing to determine the site index for california P. radiata pine in New Zealand (Watt et al. 2015) was also investigated. in addition, a model was developed to determine the productivity of the two variants: with age data and with the variant assuming no such data (Watt et al. 2016). 5. Spatial investigation of site index Despite many studies carried out so far, there is still little knowledge of the relationship between environmental factors and their impact on tree growth in spatial terms. in a study on Populus tremuloides Michx., chen et al. (2002) analysed the impact of the environment on the site index in a wider spatial dimension, yielding 61% of the explained variability. some factors had a different impact on the feature studied in different zones. This shows that the results may vary depending on the spatial scale in which they are analysed. In the study on the Douglas firing rate, P. menziesii compared the use of linear and geographically -Weighted regression in central idaho, Usa (Kimsey et al. 2008). it was shown that the use of the spatial method allowed to explain by 29% more variability in the site index and reduced the error by about 53%. the studies conduc- W. Kędziora et al. / Leśne Prace Badawcze, 2020, Vol. 81 (2): 91–98 ted so far have not confirmed unequivocally that there is a dependence of the pine stands’ site index on their geographical location in Poland. these studies also do not definitively explain whether the dependence observed locally is reflected on a nationwide scale (Bruchwald et al. 2000a). 6. Age impact on site index the problem of larger than expected tree growth was addressed in a paper by elfving and tegnhammar (1996), which showed that management can have a significant impact on tree growth. at the same time, it is known that the growth at height is inhibited by breeding work, that is, cleaning and thinning, which can disturb the discount model (hynynen 1995). research conducted on spruce in germany and Austria showed a statistically significant change in the stand height increment pattern related to the age of the examined object (schadauel 1996; Wenk, Vogel 1996). Similar studies on beech confirm the same relationships (Untheim 1996). at the same time, studies from southern germany show that the abundance tables used today do not reflect well the growth dynamics of trees, most often overestimating the results obtained empirically (Pretzsch 1996). extensive research on the growth dynamics of spruce and beech stands in europe since 1870 shows that they continue to follow the previously determined trends, although the stands are increasing their growth more rapidly (Pretzsch et al. 2014). At the same time, the lengthening of the growing season and temperature increase accelerate physiological processes (Crafts-Brandner, Salvucci 2004), especially in more fertile habitats. studies on the site index of the Baden-Württemberg spruce (Yue et al. 2014) have shown that in the mid-20th century, the growth pattern of the species under investigation changed. similar studies in Finland on pine, spruce and larch showed a difference in the growth pattern of the studied species compared to central europe (Mäkinen et al. 2017). in-depth analyses of nitrogen immissions in the study area proved that the most probable cause of doubling of tree growth during the last century was the forest management. 7. Summary the history of research on the site indexof forest species is long and goes back to the 18th century. Many pioneers of this research rightly believed that determining the quality of a habitat is very important for rational forest management. tree site index, as a measure of the potential of a habitat on which a forest grows, is one of the most important characteristics of economic stands. site index, 95 depending on the chosen model, is usually expressed as the average height of trees of a given species at a certain age (Bruchwald 1997, 1999; Sharma et al. 2002; Socha et al. 2017). however, it is not possible to compare the site index between species due to the ecology of individual species. Determination of the density of the species in the stand allows to unambiguously characterize the growth potential of the habitat (Chen, Klinka 2000; Kliczkowska, Bruchwald 2000; Socha 2005). Modelling of this potential is most often performed for one tree species. Summarizing the literature review concerning this problem, it should be stated that for the basic forest-forming species in Poland, that is, pine, there are no current studies covering the stand site index on the national scale. this concerns both the statistical characteristics, as well as the influence of external factors and the connection of the discount with the conditions prevailing in the spatial system. Conflicts of interest The authors declare no potential conflicts of interest. Source of funding this research were funded by WUls-sggW grants number: 505-10-032600-l00372-99, 505-10-032600-M0031399 oraz 505-10-032600-Q00436-99. References Aertsen W., Kint V., van Orshoven J., Özkan K., Muys B. 2010. comparison and ranking of different modelling techniques for prediction of site index in Mediterranean mountain forests. Ecological Modelling 221(8): 1119–1130. Doi 10.1016/j. ecolmodel.2010.01.007. Assmann E. 1955. 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Author's contributions W.K., R.T., T.B. – conceptualization, W.K., R.T. – literature review, W.K. – manuscript preparation