Forests

15 pages, 3979 KiB

Open AccessArticle

Accumulation of Glomalin-Related Soil Protein Regulated by Plantation Types and Vertical Distribution of Soil Characteristics in Southern China

by Miaolan Wu, Shaochun Zhang, Xiaojuan Gu, Zhihang He, Yue Liu and Qifeng Mo

Forests 2024, 15(8), 1479; https://doi.org/10.3390/f15081479 - 22 Aug 2024

Viewed by 761

Abstract

The glomalin-related soil protein (GRSP) is an important component of soil organic carbon (SOC), which plays an important role in maintaining soil structural stability, soil carbon (C), and nitrogen (N) fixation. However, little is known about the GRSP content in soil and its [...] Read more.

The glomalin-related soil protein (GRSP) is an important component of soil organic carbon (SOC), which plays an important role in maintaining soil structural stability, soil carbon (C), and nitrogen (N) fixation. However, little is known about the GRSP content in soil and its contribution to soil nutrients in plantations of different tree species. In this study, we determined the soil physicochemical characteristics and GRSP contents in different soil layers of four kinds of plantations, including Acacia mangium (AM), Pinus caribaea (PC), Eucalyptus urophylla (EU), and Magnoliaceae glanca (MG), to address how the plantation types affected the GRSP in different layers of soil in southern China. The results showed that with an increase in soil depth, the GRSP content decreased linearly, and the contribution rate of GRSP to SOC and total nitrogen (TN) in deep soil was 1.08–1.18 times that in surface soil. The tree species significantly affected the vertical distribution of GRSP in soil. Among the four plantations, the conifer species PC had the highest level of GRSP, while the N-fixing species AM had the lowest level. However, SOC, soil capillary porosity (CP), TN, soil water content (SWC), and total phosphorus (TP) were important factors regulating soil GRSP content. Additionally, the regulation effects of soil properties on GRSP were various in surface and deep soil among different plantations. In order to improve soil quality and C sequestration potential, conifer species can be planted appropriately, or conifer species and N-fixing species can be mixed to increase soil nutrient content and enhance soil structure and function in afforestation of southern China. Full article

(This article belongs to the Special Issue Biogeochemical Cycles in Forests)

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Geographical location information of the study site. The four points are the locations of the four plantations we studied. AM, Acacia mangium; PC, Pinus caribaea; EU, Eucalyptus urophylla; MG, Magnoliaceae glanca. The map was generated by the ArcGIS 10.6 software. Full article ">Figure 2
Vertical distribution of easily extractable glomalin-related soil protein (EE-GRSP), total GRSP (T-GRSP), and EE-GRSP/T-GRSP ratio in soil of different plantations. AM, Acacia mangium; PC, Pinus caribaea; EU, Eucalyptus urophylla; MG, Magnoliaceae glanca. Different capital letters indicate that there are significant differences between different tree species at the same soil depth, and different lowercase letters indicate that there are significant differences between the same tree species at different soil depths (p < 0.05). The graphic (a) is EE-GRSP concentration, (b) is T-GRSP concentration, (c) is the ratio of EE-GRSP to T-GRSP. Full article ">Figure 3
Contributions of easily extracted glomalin-related soil protein (EE-GRSP) and total GRSP (T-GRSP) to SOC and TN in soils of different tree species plantations at different soil depths. AM, Acacia mangium; PC, Pinus caribaea; EU, Eucalyptus urophylla; MG, Magnoliaceae glanca. Different capital letters indicate that there are significant differences between different tree species at the same soil depth, and different lowercase letters indicate that there are significant differences between the same tree species at different soil depths (p < 0.05). The graphic (a) is the contribution of EE-GRSP to SOC, (b) is the contribution of EE-GRSP to SOC, (c) is the contribution of EE-GRSP to TN, (d) is the contribution of T-GRSP to TN. Full article ">Figure 4
Correlation heat map of soil GRSP and soil physical and chemical factors of four tree species. ‘**‘ indicates that the difference is extremely significant (p < 0.01); ‘*‘ means significant difference (p < 0.05). Full article ">

16 pages, 3392 KiB

Open AccessArticle

Timber Tracking of Jacaranda copaia from the Amazon Forest Using DNA Fingerprinting

by Lorena Frigini Moro Capo, Bernd Degen, Celine Blanc-Jolivet, Niklas Tysklind, Stephen Cavers, Malte Mader, Barbara Rocha Venancio Meyer-Sand, Kathelyn Paredes-Villanueva, Eurídice Nora Honorio Conorado, Carmen Rosa García-Dávila, Valérie Troispoux, Adline Delcamp and Alexandre Magno Sebbenn

Forests 2024, 15(8), 1478; https://doi.org/10.3390/f15081478 - 22 Aug 2024

Viewed by 1386

Abstract

We investigated the utility of nuclear and cytoplasmic single nucleotide polymorphism (SNP) markers for timber tracking of the intensively logged and commercialized Amazonian tree Jacaranda copaia. Eight hundred and thirty-two trees were sampled (cambium or leaves) from 38 sampling sites in Bolivia, [...] Read more.

We investigated the utility of nuclear and cytoplasmic single nucleotide polymorphism (SNP) markers for timber tracking of the intensively logged and commercialized Amazonian tree Jacaranda copaia. Eight hundred and thirty-two trees were sampled (cambium or leaves) from 38 sampling sites in Bolivia, Brazil, French Guiana, and Peru. A total of 128 SNP markers (113 nuclear, 11 chloroplastic, and 4 mitochondrial) were used for genotyping the samples. Bayesian cluster analyses were carried out to group individuals into homogeneous genetic groups for tests to self-assign groups of individuals or individuals to their population of origin. Cluster analysis based on all the SNP markers detected seven main genetic groups. Genetic differentiation was high among populations (0.484) and among genetic groups (0.415), and populations showed a strong isolation-by-distance pattern. Self-assignment testing of the groups of individuals for all loci was able to determine the population origin of all the samples (accuracy = 100%). Self-assignment tests of individuals were able to assign the origin of 94.5%–100% of individuals (accuracy: 91.7%–100%). Our results show that the use of the 128 SNP markers is suitable to correctly determine the origin of J. copaia timber, and they should be considered a useful tool for customs and local and international police. Full article

(This article belongs to the Special Issue Development of Nuclear SNP Markers for Tracing Timber)

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20 pages, 5183 KiB

Open AccessArticle

Spatial Pattern of Drought-Induced Mortality Risk and Influencing Factors for Robinia pseudoacacia L. Plantations on the Chinese Loess Plateau

by Zhong-Dian Zhang, Tong-Hui Liu, Ming-Bin Huang, Xiao-Ying Yan, Ming-Hua Liu, Jun-Hui Yan, Fei-Yan Chen, Wei Yan and Ji-Qiang Niu

Forests 2024, 15(8), 1477; https://doi.org/10.3390/f15081477 - 22 Aug 2024

Viewed by 765

Abstract

During the large-scale vegetation restoration on the Loess Plateau, the introduction of exotic species with high water consumption, such as Robinia pseudoacacia L., led to widespread soil desiccation, and resulted in severe drought stress and increasing risk of forest degradation and mortality. Accurate [...] Read more.

During the large-scale vegetation restoration on the Loess Plateau, the introduction of exotic species with high water consumption, such as Robinia pseudoacacia L., led to widespread soil desiccation, and resulted in severe drought stress and increasing risk of forest degradation and mortality. Accurate assessment of drought-induced mortality risk in plantation forests is essential for evaluating and enhancing the sustainability of ecological restoration, yet quantitative research at the regional scale on the Loess Plateau is lacking. With a focus on Robinia pseudoacacia L. plantations, we utilized a coupled model of the Biome BioGeochemical Cycles model and plant supply–demand hydraulic model (BBGC-SPERRY model) to simulate the dynamics of the annual average percentage loss of whole-plant hydraulic conductance (APLK) at 124 meteorological stations over an extended period (1961–2020) to examine changes in plant hydraulic safety in Robinia pseudoacacia L. plantations. Based on the probability distribution of APLK at each site, the drought-induced mortality risk probability (DMRP) in Robinia pseudoacacia L. was determined. The results indicate the BBGC-SPERRY model could effectively simulate the spatiotemporal variations in transpiration and evapotranspiration in Robinia pseudoacacia L. stands on the Loess Plateau. The mean APLK and DMRP exhibited increasing trends from southeast to northwest along a precipitation gradient, with their spatial patterns on the Loess Plateau mainly driven by mean annual precipitation and also significantly influenced by other climatic and soil factors. The low-risk (DMRP < 2%), moderate-risk (2% ≤ DMRP ≤ 5%), and high-risk (DMRP > 5%) zones for drought-induced mortality in Robinia pseudoacacia L. accounted for 60.0%, 30.7%, and 9.3% of the study area, respectively. These quantitative findings can provide an important basis for rational forestation and sustainable vegetation management on the Loess Plateau. Full article

(This article belongs to the Section Forest Hydrology)

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Map depicting the location of the study area on the Loess Plateau and the distributions of mean annual precipitation (MAP, 1961–2020), 124 modeling sites, and 11 model evaluation sites in the region. ETa, annual actual evapotranspiration during the growing season. Full article ">Figure 2
Flowchart depicting the methodology and data sources of the study. Firstly, the performance of the BBGC-SPERRY model was evaluated with data of annual actual evapotranspiration during the growing season (ETa) and daily stem sap flux density collected from previous studies. Then, we simulated the long-term dynamics of plant hydraulic traits with 60-year meteorological data and soil hydraulic parameters at 124 sites by the BBGC-SPERRY model. Finally, based on temporal changes of plant hydraulic traits at each site and plant hydraulic threshold, we evaluated the spatial pattern of drought-induced mortality risk for Robinia pseudoacacia L. plantations using a probabilistic approach. Full article ">Figure 3
Flow chart of the BBGC-SPERRY model. The soil–plant–atmosphere continuum water transport is simulated with a plant supply–demand hydraulic model (Sperry model) for the coupled simulation of plant hydraulic traits with water, carbon, and nitrogen cycles in the Biome BioGeochemical Cycles (Biome-BGC) model. APLK, annual average percentage loss of whole-plant hydraulic conductance. HR, heterotrophic respiration. Full article ">Figure 4
Schematic diagram of the determination of drought-induced mortality risk probability (shaded area) based on the fitted probability distribution of annual average percentage loss of whole-plant hydraulic conductance (APLK). Full article ">Figure 5
Comparison of simulated versus observed annual actual evapotranspiration during the growing season (ETa) in Robinia pseudoacacia L. stands. Full article ">Figure 6
Spatial distribution of minimum (a), maximum (b), and mean (c) annual average percentage loss of whole-plant hydraulic conductance (APLK) for Robinia pseudoacacia L. in the study area. Full article ">Figure 7
Correlations between environmental factors, minimum, maximum, and mean annual average percentage loss of whole-plant hydraulic conductance (APLK), and drought-induced mortality risk probability (DMRP) for Robinia pseudoacacia L. MAP, mean annual precipitation; and MAT, mean annual temperature. Color gradient and size of the symbols indicate the correlation coefficient among different indicators. * means p < 0.05; ** means p < 0.01; and *** means p < 0.001. Full article ">Figure 8
Spatial distribution of drought-induced mortality risk probability (DMRP) of Robinia pseudoacacia L. in the study area. Full article ">

19 pages, 17938 KiB

Open AccessArticle

Land Surface Temperature May Have a Greater Impact than Air Temperature on the Autumn Phenology in the Tibetan Plateau

by Hanya Tang, Xizao Sun, Xuelin Zhou, Cheng Li, Lei Ma, Jinlian Liu, Zhi Ding, Shiwei Liu, Pujia Yu, Luyao Jia and Feng Zhang

Forests 2024, 15(8), 1476; https://doi.org/10.3390/f15081476 - 22 Aug 2024

Viewed by 732

Abstract

The Tibetan Plateau (TP), with its unique geographical and climatic conditions, holds a significant role in global climate change. Therefore, it is particularly urgent to fully understand its vegetation phenology. Herbaceous plants are widely distributed in the TP. However, previous studies have predominantly [...] Read more.

The Tibetan Plateau (TP), with its unique geographical and climatic conditions, holds a significant role in global climate change. Therefore, it is particularly urgent to fully understand its vegetation phenology. Herbaceous plants are widely distributed in the TP. However, previous studies have predominantly examined the impact of air temperature on the end date of the vegetation growing season (EOS), with less emphasis on the influence of land surface temperature (LST). In this study, the dynamic changes in the EOS from 2001 to 2020 were analyzed by utilizing the Normalized Difference Vegetation Index (NDVI) data published by NASA. Furthermore, the impact of climate change on the EOS was examined, and the dominant factor (air temperature, LST, or precipitation) influencing the EOS was identified. The main findings were as follows: the average annual EOS predominantly occurred between day of year (DOY) 240 and 280, with an advance from the edge of the plateau to the center. The EOS across the entire region displayed a marginal tendency towards delay, with an average rate of 0.017 days/year. Among all vegetation, shrubs showed the most pronounced delay at a rate of 0.04 days/year. In terms of precipitation, the impact of climate change increased precipitation in both summer and autumn, which could delay EOS. In terms of temperature, an increase in summer T_min, autumn air temperatures and summer LST delayed the EOS, while an increase in autumn LST advanced the EOS. Compared to air temperature and precipitation, LST had a stronger controlling effect on the EOS (the largest pixel area dominated by LST). These results could offer new insights for enhancing the parameters of vegetation phenology models across the TP. Full article

(This article belongs to the Special Issue Application of Remote Sensing in Vegetation Dynamic and Ecology)

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26 pages, 18602 KiB

Open AccessArticle

Integration of Phenotypes, Phytohormones, and Transcriptomes to Elucidate the Mechanism Governing Early Physiological Abscission in Coconut Fruits (Cocos nucifera L.)

by Lilan Lu, Zhiguo Dong, Xinxing Yin, Siting Chen and Ambreen Mehvish

Forests 2024, 15(8), 1475; https://doi.org/10.3390/f15081475 - 22 Aug 2024

Viewed by 896

Abstract

The abscission of fruits has a significant impact on yield, which in turn has a corresponding effect on economic benefits. In order to better understand the molecular mechanism of early coconut fruit abscission, the morphological and structural characteristics, cell wall hydrolysis and oxidase [...] Read more.

The abscission of fruits has a significant impact on yield, which in turn has a corresponding effect on economic benefits. In order to better understand the molecular mechanism of early coconut fruit abscission, the morphological and structural characteristics, cell wall hydrolysis and oxidase activities, phytohormones, and transcriptomes were analyzed in the abscission zone (AZ) from early-abscised coconut fruits (AFs) and non-abscised coconut fruits (CFs). These results indicated that the weight and water content of AFs are significantly lower than those of CFs, and the color of AFs is a grayish dark red, with an abnormal AZ structure. Cellulase (CEL), polygalacturonase (PG), pectinesterase (PE), and peroxidase (POD) activities were significantly lower than those of CFs. The levels of auxin (IAA), gibberellin (GA), cytokinins (CKs), and brassinosteroid (BR) in AFs were significantly lower than those in CFs. However, the content of abscisic acid (ABA), ethylene (ETH), jasmonic acid (JA), and salicylic acid (SA) in AFs was significantly higher than in CFs. The transcriptome analysis results showed that 3601 DEGs were functionally annotated, with 1813 DEGs upregulated and 1788 DEGs downregulated. Among these DEGs, many genes were enriched in pathways such as plant hormone signal transduction, carbon metabolism, peroxisome, pentose and gluconate interconversion, MAPK signaling pathway—plant, and starch and sucrose metabolism. Regarding cell wall remodeling-related genes (PG, CEL, PE, POD, xyloglucan endoglucosidase/hydrogenase (XTH), expansin (EXP), endoglucanase, chitinase, and beta-galactosidase) and phytohormone-related genes (IAA, GA, CKs, BR, ABA, JA, SA, and ETH) were significantly differentially expressed in the AZ of AFs. Additionally, BHLH, ERF/AP2, WRKY, bZIP, and NAC transcription factors (TFs) were significantly differently expressed, reflecting their crucial role in regulating the abscission process. This study’s results revealed the molecular mechanism of early fruit abscission in coconuts. This provided a new reference point for further research on coconut organ development and abscission. Full article

(This article belongs to the Section Genetics and Molecular Biology)

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21 pages, 11132 KiB

Open AccessArticle

Construction of a Genetic Transformation System for Populus wulianensis

by Yan Wang, Chenxia Song, Yi Han, Ruilong Wang, Lingshan Guan, Yanjuan Mu, Tao Sun, Xiaoman Xie, Yunchao Zhao, Jichen Xu and Yizeng Lu

Forests 2024, 15(8), 1474; https://doi.org/10.3390/f15081474 - 22 Aug 2024

Viewed by 870

Abstract

Transgenic technology is a potent tool for verifying gene functions, and poplar serves as a model system for genetically transforming perennial woody plants. However, the current poplar genetic transformation system is limited to a few genotypes. In this study, we developed an efficient [...] Read more.

Transgenic technology is a potent tool for verifying gene functions, and poplar serves as a model system for genetically transforming perennial woody plants. However, the current poplar genetic transformation system is limited to a few genotypes. In this study, we developed an efficient transformation system based on the Agrobacterium-mediated transformation of Populus wulianensis, a rare and endangered tree species endemic to Shandong Province. Aseptic seedlings of P. wulianensis were used as experimental materials, and the optimal medium for inducing adventitious buds was explored as 1/2(NH₄NO₃) MS + 0.05 mg/L naphthalene acetic acid (NAA) + 0.5 mg/L 6-benzylaminopurine (6-BA), resulting in up to 35 adventitious buds. The selection resistance critical pressure of 300 mg/L for timentin can effectively inhibit the growth of Agrobacterium while promoting the induction of adventitious buds in leaves. The critical screening pressure for kanamycin for producing resistant adventitious buds and inducing resistant rooting seedlings was 100 mg/L. We optimized several independent factors, which significantly enhanced the efficiency of genetic transformation. The leaves were infected with Agrobacterium suspension diluted twice by adding 100 μmol/L acetylsyringone (β-AS) (OD₆₀₀ = 0.6) for 15 min, followed by co-culture in the dark for 3 d. Using this improved transformation system, we obtained transgenic P. wulianensis clones overexpressing the enhanced green fluorescent protein (EGFP) gene through direct organogenesis. Among the 112 resistant buds obtained, 17 developed resistant rooting in seedlings. Eight positive plants were identified through DNA, RNA, and protein level analyses, with a positivity rate of 47.06%. This study provides a foundation for developing and utilizing P. wulianensis germplasm resources and lays the groundwork for resource improvement. Full article

(This article belongs to the Section Genetics and Molecular Biology)

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20 pages, 7365 KiB

Open AccessArticle

Increased Soil Moisture in the Wet Season Alleviates the Negative Effects of Nitrogen Deposition on Soil Microbial Communities in Subtropical Evergreen Broad-Leaved Forest

by Wen Chen, Zheng Hou, Donghui Zhang, Leixi Chen, Keqin Wang and Yali Song

Forests 2024, 15(8), 1473; https://doi.org/10.3390/f15081473 - 21 Aug 2024

Viewed by 794

Abstract

The rapid increase in reactive nitrogen (N) released into the environment by human activities has notably altered the structure and composition of forest soil microbial communities (SMCs), profoundly impacting the N cycle in terrestrial ecosystems. However, the response of soil microorganisms to nitrogen [...] Read more.

The rapid increase in reactive nitrogen (N) released into the environment by human activities has notably altered the structure and composition of forest soil microbial communities (SMCs), profoundly impacting the N cycle in terrestrial ecosystems. However, the response of soil microorganisms to nitrogen addition in different seasons is not clear. This study delved into how SMCs in a subtropical region of central Yunnan, China, specifically in an evergreen broad-leaved forest (EBLF), respond to N deposition during both the dry and wet seasons. Through high-throughput sequencing, we assessed the composition and structure of SMCs under varying N addition treatments across seasons, examining their interplay with soil chemical properties, enzyme activities, and community responses. The findings revealed significant outcomes following four years of N addition in the subtropical EBLF: (1) Significant changes were observed due to the interaction between N addition and seasonal changes. Soil pH significantly decreased, indicating increased soil acidification, particularly in the dry season. Increased moisture in the wet season mitigated soil acidification. (2) In the dry season, N addition led to a decrease in microbial richness and diversity. In the wet season, N addition increased microbial richness and diversity, alleviating the downward trend observed in the dry season. (3) N addition significantly impacted the composition of soil bacterial and fungal communities. Dominant fungal genera in the wet season were particularly sensitive to N addition. (4) Seasonal changes and N addition altered soil microbial community structures. Soil chemical properties and enzyme activities significantly influenced the microbial community structure. However, due to differences in soil moisture, the key environmental factors that regulate microbial communities have changed significantly during the dry and wet seasons. This study serves as a foundation for understanding how N deposition impacts SMCs in EBLF ecosystems in subtropical regions, offering valuable insights for the scientific management of forest ecological resources amidst global change trends. Full article

(This article belongs to the Special Issue Forest Soil Microbiology and Biogeochemistry)

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19 pages, 10880 KiB

Open AccessArticle

Satellite Evidence for Increasing in Terrestrial Evapotranspiration over the Contiguous United States from 2001 to 2022

by Lu Liu, Yunjun Yao, Yufu Li, Zijing Xie, Jing Ning, Ruiyang Yu, Jiahui Fan, Yixi Kan, Luna Zhang and Jia Xu

Forests 2024, 15(8), 1472; https://doi.org/10.3390/f15081472 - 21 Aug 2024

Viewed by 728

Abstract

Evapotranspiration (ET) is a key process in the eco-hydrological cycle of a basin and a reliable indicator of climate change. However, the spatiotemporal alterations of ET in the contiguous United States (CONUS) over the recent two decades remain largely uncertain. In this study, [...] Read more.

Evapotranspiration (ET) is a key process in the eco-hydrological cycle of a basin and a reliable indicator of climate change. However, the spatiotemporal alterations of ET in the contiguous United States (CONUS) over the recent two decades remain largely uncertain. In this study, we used the recently proposed Priestley–Taylor (PT)-SinRH model to estimate the ET of CONUS during 2001–2022 based on satellite and reanalysis data. The results showed that the PT-SinRH model yielded superior performance at eddy covariance (EC) sites, and the root-mean-square error (RMSE) ranged from 6.0 to 33.5 W/m², the Kling–Gupta efficiency (KGE) ranged from 0.22 to 0.66. The annual mean value of ET in CONUS from 2001 to 2022, estimated by the PT-SinRH model, was 42.54 W/m², and the spatial pattern of seasonal and annual ET variations increased from west to east. From 2001 to 2022, seasonal and annual ET of CONUS showed linear trends, with an average increase of 0.76 W/m²/da (p < 0.05). The ET in the east of CONUS exhibited a rate of increase at 1.45 W/m²/da, and the ET in the west of CONUS exhibited a rate of increase at 0.42 W/m²/da (p < 0.05). Importantly, our analysis of ET trends highlights that the change of precipitation (P) and normalized difference vegetation index (NDVI) exerts a significant impact on the change of ET over CONUS. Full article

(This article belongs to the Section Forest Inventory, Modeling and Remote Sensing)

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19 pages, 2351 KiB

Open AccessArticle

Unveiling the Centrality of Knowledge in Stakeholder Involvement Strategies Regarding Public Forest Management

by Carla Ferreira, Maria Eduarda Fernandes and Elisabete Figueiredo

Forests 2024, 15(8), 1471; https://doi.org/10.3390/f15081471 - 21 Aug 2024

Viewed by 1104

Abstract

Stakeholder involvement can foster more socially and environmentally sustainable management of natural resources, including forests. However, few studies have approached the effect of knowledge on stakeholders’ involvement in forest management. This study intends to contribute to filling this gap by exploring the relationship [...] Read more.

Stakeholder involvement can foster more socially and environmentally sustainable management of natural resources, including forests. However, few studies have approached the effect of knowledge on stakeholders’ involvement in forest management. This study intends to contribute to filling this gap by exploring the relationship between access to knowledge, involvement, stakeholders’ profiles, and levels of influence and interest regarding public forest management strategies. To this end, this article examines the data collected through a questionnaire directed to all the stakeholders potentially interested in the management of the Matas do Litoral. Matas do Litoral are part of the 3% of publicly managed forests in Portugal. The results reveal a discrepancy between the high levels of interest regarding Matas do Litoral management, and low levels of influence on those processes. Most of the stakeholders surveyed know forest management strategies, and their involvement in those strategies is limited. The proximity and role of governmental organizations are key factors underlying knowledge levels among the various stakeholders. Furthermore, knowledge acts as a critical factor in encouraging the stakeholders’ influence and involvement in management strategies and policies. This study gives insights regarding the need for knowledge management as a tool for empowering local stakeholders and promoting their involvement in bottom-up forest management strategies. Full article

(This article belongs to the Section Forest Economics, Policy, and Social Science)

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13 pages, 4291 KiB

Open AccessArticle

Effects of Soil Physical Properties on Soil Infiltration in Forest Ecosystems of Southeast China

by Di Wang, Jinhong Chen, Zhiying Tang and Yinghu Zhang

Forests 2024, 15(8), 1470; https://doi.org/10.3390/f15081470 - 21 Aug 2024

Viewed by 859

Abstract

Soil infiltration properties (SIPs) are important components of forest hydrological responses; however, few studies have investigated the mechanisms through which soil physical properties affect SIPs. In this study, two SIPs, the initial infiltration rate (IIR) and saturated hydraulic conductivity (Ks), were [...] Read more.

Soil infiltration properties (SIPs) are important components of forest hydrological responses; however, few studies have investigated the mechanisms through which soil physical properties affect SIPs. In this study, two SIPs, the initial infiltration rate (IIR) and saturated hydraulic conductivity (Ks), were quantified at five soil depths (0–10, 10–20, 20–30, 30–40, and 40–50 cm) in three forest stands (pine (Pinus taeda), oak (Quercus acutissima), and bamboo (Phyllostachys edulis) forests). We constructed a structural equation model (SEM) to analyze the main physical properties affecting the SIPs and their influence pathways, and the results show that the IIR and Ks values for the whole soil profile decreased as follows: pine forest > oak forest > bamboo forest. Soil total porosity (STP), soil field capacity (SFC), capillary water holding capacity (CMC), saturated water capacity (SWC), and initial soil water content (ISWC) were positively correlated with the SIPs, while soil bulk density (SBD) was negatively correlated with the SIPs. The SEM indicated that the main positive driver of soil infiltration was STP, while the sand content and SBD reduced soil infiltration. Soil texture indirectly affected SBD by mediating STP, and SBD indirectly affected the SIPs through SWC. These results provide data that support the simulation of subsurface hydrological responses in forests and have significant implications for forest management. Full article

(This article belongs to the Section Forest Hydrology)

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Graphical abstract

Graphical abstract
Full article ">Figure 1
Location of the study area. Full article ">Figure 2
Schematic diagram of the measurement principle of the device. Full article ">Figure 3
Changes in initial infiltration rate and saturated hydraulic conductivity at 10 °C as a function of soil depth in three stands (pine (Pinus taeda), oak (Quercus acutissima), and bamboo (Phyllostachys edulis)): (a) Initial infiltration rate; (b) Ks (Saturated hydraulic conductivity at 10 °C). Capital letters A and B indicate significant differences in infiltration at different soil depths in the same stand; lowercase letters a and b denote significant differences in infiltration at the same soil depth across stands. Full article ">Figure 4
Correlations between soil physical properties and initial infiltration rate, and saturated hydraulic conductivity at 10 °C in three stands (a), and redundancy analysis of soil physical properties and water infiltration properties (b), IIR: Initial infiltration rate; Ks: Saturated hydraulic conductivity at 10 °C. Full article ">Figure 5
Causal relationships between dominant factors of soil physical properties and soil moisture infiltration properties in three stands were based on structural equation modeling (SEM) and standardized direct and total effects. (*** indicates significance at p < 0.001. SBD, soil bulk density; STP, total capillary porosity; SWC, saturated water capacity. (a) IIR, initial infiltration rate; (b) Ks, saturated hydraulic conductivity at 10 °C in the three stands. The value next to each arrow represents the normalized path coefficient. Unidirectional arrows indicate the direct effect of a unidirectional causal relationship. The width of the arrow indicates the strength of the causal relationship. Full article ">

13 pages, 5155 KiB

Open AccessArticle

Developing Forest Road Recognition Technology Using Deep Learning-Based Image Processing

by Hyeon-Seung Lee, Gyun-Hyung Kim, Hong Sik Ju, Ho-Seong Mun, Jae-Heun Oh and Beom-Soo Shin

Forests 2024, 15(8), 1469; https://doi.org/10.3390/f15081469 - 21 Aug 2024

Viewed by 800

Abstract

This study develops forest road recognition technology using deep learning-based image processing to support the advancement of autonomous driving technology for forestry machinery. Images were collected while driving a tracked forwarder along approximately 1.2 km of forest roads. A total of 633 images [...] Read more.

This study develops forest road recognition technology using deep learning-based image processing to support the advancement of autonomous driving technology for forestry machinery. Images were collected while driving a tracked forwarder along approximately 1.2 km of forest roads. A total of 633 images were acquired, with 533 used for the training and validation sets, and the remaining 100 for the test set. The YOLOv8 segmentation technique was employed as the deep learning model, leveraging transfer learning to reduce training time and improve model performance. The evaluation demonstrates strong model performance with a precision of 0.966, a recall of 0.917, an F1 score of 0.941, and a mean average precision (mAP) of 0.963. Additionally, an image-based algorithm is developed to extract the center from the forest road areas detected by YOLOv8 segmentation. This algorithm detects the coordinates of the road edges through RGB filtering, grayscale conversion, binarization, and histogram analysis, subsequently calculating the center of the road from these coordinates. This study demonstrates the feasibility of autonomous forestry machines and emphasizes the critical need to develop forest road recognition technology that functions in diverse environments. The results can serve as important foundational data for the future development of image processing-based autonomous forestry machines. Full article

(This article belongs to the Special Issue Cutting-Edge Solutions in Advanced Forestry: Integrating Sensors, AI, IoT, Robotics, and Connectivity)

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13 pages, 2566 KiB

Open AccessArticle

Changes in Soil Total and Microbial Biomass Nitrogen in Deforested and Eroded Areas in the Western Black Sea Region of Turkey

by İlyas Bolat and Huseyin Sensoy

Forests 2024, 15(8), 1468; https://doi.org/10.3390/f15081468 - 21 Aug 2024

Viewed by 605

Abstract

The microbial biomass in soil is an active and living constituent of organic matter. It is both a storage pool and a source of plant nutrients that can be used as required. In addition, each microbial indicator evaluates soil quality and health from [...] Read more.

The microbial biomass in soil is an active and living constituent of organic matter. It is both a storage pool and a source of plant nutrients that can be used as required. In addition, each microbial indicator evaluates soil quality and health from different perspectives, which are not necessarily very different. This study was conducted to compare some physical, chemical, and biochemical characteristics of the soils of forest (S_F) and deforested (S_DE) areas located on the slopes of the Kirazlıköprü area, which was previously deforested due to dam construction in Bartın province in northwestern Turkey. Soil samples were taken from the topsoil surface (0–5 cm) to determine the microbial soil characteristics of the S_F and S_DE sites. The soil microbial biomass N (N_mic) was determined by chloroform fumigation extraction, and the C_mic/N_mic ratio and N_mic/N_total percentage were calculated using the original values. Total N, N_mic and C_mic/N_mic values are higher in the forest area. The lowest and highest total N (N_total) contents in the S_F and S_DE soils varied between 1.50 and 3.47 g kg⁻¹ and 0.91 and 1.46 g kg⁻¹, respectively. Similarly, the N_mic contents of the S_F and S_DE soils varied between 75.56 and 143.42 μg g⁻¹ and 10.40 and 75.96 μg g⁻¹, respectively. A statistical analysis revealed that the mean N_total and mean N_mic values differed (p < 0.05) in the S_F and S_DE soils. The mean C_mic/N_mic values in the S_F and S_DE soils were 8.79 (±1.65) and 5.64 (±1.09), respectively, and a statistical difference was found between the fields (p < 0.05). Our findings indicate that the soil microbial community structure varies according to the site. As a result, it can be concluded that deforestation and erosion due to dam construction in the area led to the removal of plant nutrients from the soil; deterioration in the amount and activity of microbial biomass; and, consequently, soil losses and degradation of soil quality. Full article

(This article belongs to the Section Forest Soil)

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18 pages, 6073 KiB

Open AccessArticle

Estimation of NPP in Huangshan District Based on Deep Learning and CASA Model

by Ziyu Wang, Youfeng Zhou, Xinyu Sun and Yannan Xu

Forests 2024, 15(8), 1467; https://doi.org/10.3390/f15081467 - 21 Aug 2024

Viewed by 822

Abstract

Net primary productivity (NPP) is a key indicator of the health of forest ecosystems that offers important information about the net carbon sequestration capacity of these systems. Precise assessment of NPP is crucial for measuring carbon fixation and assessing the general well-being of [...] Read more.

Net primary productivity (NPP) is a key indicator of the health of forest ecosystems that offers important information about the net carbon sequestration capacity of these systems. Precise assessment of NPP is crucial for measuring carbon fixation and assessing the general well-being of forest ecosystems. Due to the distinct ecological characteristics of various forest types, accurately understanding and delineating the distribution of these types is crucial for studying NPP. Therefore, an accurate forest-type classification is necessary prior to NPP calculation to ensure the accuracy and reliability of the research findings. This study introduced deep learning technology and constructed an HRNet-CASA framework that integrates the HRNet deep learning model and the CASA model to achieve accurate estimation of forest NPP in Huangshan District, Huangshan City, Anhui Province. Firstly, based on VHR remote sensing images, we utilized the HRNet to classify the study area into six forest types and obtained the forest type distribution map of the study area. Then, combined with climate data and forest type distribution data, the CASA model was used to estimate the NPP of forest types in the study area, and the comparison with the field data proved that the HRNet-CASA framework simulated the NPP of the study area well. The experimental findings show that the HRNet-CASA framework offers a novel approach to precise forest NPP estimation. Introducing deep learning technology not only enables precise classification of forest types but also allows for accurate estimation of NPP for different types of forests. This provides a more effective tool for forest ecological research and environmental protection. Full article

(This article belongs to the Section Forest Inventory, Modeling and Remote Sensing)

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12 pages, 5931 KiB

Open AccessArticle

Soil-Moisture-Dependent Temperature Sensitivity of Soil Respiration in a Poplar Plantation in Northern China

by Huan He, Tonggang Zha and Jiongrui Tan

Forests 2024, 15(8), 1466; https://doi.org/10.3390/f15081466 - 21 Aug 2024

Viewed by 796

Abstract

The temperature sensitivity (Q₁₀) of soil respiration (Rs) plays a crucial role in evaluating the carbon budget of terrestrial ecosystems under global warming. However, the variability in Q₁₀ along soil moisture gradients remains a subject of debate, and the associated [...] Read more.

The temperature sensitivity (Q₁₀) of soil respiration (Rs) plays a crucial role in evaluating the carbon budget of terrestrial ecosystems under global warming. However, the variability in Q₁₀ along soil moisture gradients remains a subject of debate, and the associated underlying causes are poorly understood. This study aims to investigate the characteristics of Q₁₀ changes along soil moisture gradients throughout the whole growing season and to assess the factors influencing Q₁₀ variability. Changes in soil respiration (measured by the dynamic chamber method) and soil properties were analyzed in a poplar plantation located in the suburban area of Beijing, China. The results were as follows: (1) Q₁₀ increased with the increasing soil water content up to a certain threshold, and then decreased, (2) the threshold was 75% to 80% of the field capacity (i.e., the moisture content at capillary rupture) rather than the field water-holding capacity, and (3) the dominant influence shifted from soil solid-phase properties to microbes with increasing soil moisture. Our results are important for understanding the relationship between the temperature sensitivity of soil respiration and soil moisture in sandy soil, and for the refinement of the modeling of carbon cycling in terrestrial ecosystems. Full article

(This article belongs to the Special Issue Forest Vegetation and Soils: Interaction, Management and Alterations—Second Edition)

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Location of the study area. Full article ">Figure 2
A conceptual diagram showing the factors influencing Q10 in sandy soil of a poplar plantation in northern China. Full article ">Figure 3
Soil water retention curve for the topsoil layer. Full article ">Figure 4
Diurnal variation (a) and temporal variation (mean values ± SD) (b) of soil respiration. Full article ">Figure 5
Relationships between daily Q10 values and soil moisture during the growing season. R2 is the proportion of variance explained. P is the significance level. The black arrows indicate the observed trend in the relationship between daily Q10 values and soil water content. Full article ">Figure 6
Correlation analysis of Q10 and soil properties for soil moisture lower than the WRC (a) and soil moisture higher than the WRC (b). The blue circles indicate positive correlations, and the red circles indicate negative correlations. The coefficients in the figure represent a strong (* p < 0.05), significant (** p < 0.01), or strongly significant (*** p < 0.001) correlation. Full article ">Figure 7
Individual and shared effects of soil moisture, soil solid-phase properties, and microbial factors on Q10, as derived when the soil moisture was lower than the WRC (a) and when the soil moisture was higher than the WRC (b). Dynamics of the relationships among Q10 and soil properties during the growing season (c). Full article ">

15 pages, 4201 KiB

Open AccessArticle

Species and Stand Management Options for Wood Production from Small Grower Plantations in Central Vietnam

by Christopher E. Harwood, Le Xuan Toan, Pham Xuan Dinh and E. K. Sadanandan Nambiar

Forests 2024, 15(8), 1465; https://doi.org/10.3390/f15081465 - 21 Aug 2024

Viewed by 755

Abstract

Acacia hybrid (Acacia mangium Willd. × A. auriculiformis A. Cunn. Ex Benth.) dominates plantation wood production in central Vietnam. Dependence on a single species may increase biological risks. The potential of eucalypt as an alternative was examined by comparing the growth and [...] Read more.

Acacia hybrid (Acacia mangium Willd. × A. auriculiformis A. Cunn. Ex Benth.) dominates plantation wood production in central Vietnam. Dependence on a single species may increase biological risks. The potential of eucalypt as an alternative was examined by comparing the growth and survival of acacia hybrid and eucalypt hybrid (Eucalyptus urophylla S.T. Blake × E. pellita F. Muell.) clones in Quang Tri province at three planting densities (1333, 1667 and 2222 trees ha⁻¹). The experiment was planted on an eroded shallow soil common in the region. At age 5 years, survival of acacia (74%) was higher than that of eucalypt (67%), a consequence of high mortality from wind damage for one eucalypt clone. Eucalypt was taller by about 2 m, but stem diameters of acacia and eucalypt were very similar. For both taxa, diameter decreased significantly as planting density increased. Across planting densities, mean standing volume was 107 and 108 m³ ha⁻¹ for acacia and eucalyptus, respectively. Linear regressions of stocking at 5 years on volume accounted for over half of the variance in acacia and eucalypt plot volumes, demonstrating the strong effect of stocking on yield. There were similarly strong effects of stocking on stem diameter. Acacia hybrid plantations of nearby small growers had stockings at age 5 years that averaged over 2500 stems ha⁻¹. Growers planted at higher densities and allowed their trees to multi-stem. Their standing volumes at age 5 years ranged from 83 to 102 m³ ha⁻¹. Understanding how to reduce tree mortality would assist growers to choose planting densities and stand management that optimise growth, log diameter classes and net returns. Full article

(This article belongs to the Section Genetics and Molecular Biology)

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(a) soil profile, the colour bands show 10 cm intervals, (b) typical understorey below acacia (left of observer) and eucalypt (right), (c), crowns of eucalypt trees and (d) crowns of acacia trees. Photos taken at a stand age of 5.5 years. Full article ">Figure 1 Cont.
(a) soil profile, the colour bands show 10 cm intervals, (b) typical understorey below acacia (left of observer) and eucalypt (right), (c), crowns of eucalypt trees and (d) crowns of acacia trees. Photos taken at a stand age of 5.5 years. Full article ">Figure 2
Relationships between stocking and growth attributes: (a) regression of standing volume on stocking; (b) regression of stem diameter on stocking. Full article ">Figure 2 Cont.
Relationships between stocking and growth attributes: (a) regression of standing volume on stocking; (b) regression of stem diameter on stocking. Full article ">Figure 3
Mortality trends of clones from age 1 to 5 years. Full article ">Figure 4
Typical small grower plantation, showing multi-stemming of many trees. Full article ">

11 pages, 1823 KiB

Open AccessArticle

Determinants of Deadwood Biomass under the Background of Nitrogen and Water Addition in Warm Temperate Forests

by Liang Hong, Shouzheng Tang, Tao Li, Liyong Fu, Xinyu Song, Guangshuang Duan, Jueming Fu and Lei Ma

Forests 2024, 15(8), 1464; https://doi.org/10.3390/f15081464 - 20 Aug 2024

Viewed by 647

Abstract

Climate change is exacerbating the vulnerability of temperate forests to severe disturbances, potentially increasing tree mortality rates. Despite the significance of this issue, there has been a lack of comprehensive research on tree survival across extensive forest areas under the background of global [...] Read more.

Climate change is exacerbating the vulnerability of temperate forests to severe disturbances, potentially increasing tree mortality rates. Despite the significance of this issue, there has been a lack of comprehensive research on tree survival across extensive forest areas under the background of global climate change. To fill this gap, we conducted a detailed analysis of tree survival within a canopy nitrogen and water addition experimental platform in central China, utilizing data from two censuses and evaluating contributing factors. Our findings revealed 283 dead trees within the plots, predominantly of very small diameters (1–10 cm). The distribution of these dead trees varied among subplots, influenced by both biotic and abiotic factors. Notably, three dominant tree species were responsible for 64.8% of the deadwood biomass. The study determined that both the breast diameter and the quantity of dead trees, affected by surrounding trees and environmental conditions, played a critical role in deadwood biomass accumulation. This research offers an in-depth examination of deadwood biomass patterns in a temperate forest, highlighting the need to consider both experiment treatments and abiotic elements like topography in studies of forest ecosystem carbon. The insights gained from this study enhance our understanding of warm temperate forests’ role in the global carbon cycle and offer valuable guidance for forest conservation and management strategies. Full article

(This article belongs to the Special Issue Biomass Estimation and Carbon Stocks in Forest Ecosystems: 2nd Edition)

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23 pages, 11067 KiB

Open AccessArticle

A Down-Scaling Inversion Strategy for Retrieving Canopy Water Content from Satellite Hyperspectral Imagery

by Meihong Fang, Xiangyan Hu, Jing M. Chen, Xueshiyi Zhao, Xuguang Tang, Haijian Liu, Mingzhu Xu and Weimin Ju

Forests 2024, 15(8), 1463; https://doi.org/10.3390/f15081463 - 20 Aug 2024

Viewed by 707

Abstract

Vegetation canopy water content (CWC) crucially affects stomatal conductance and photosynthesis and, consequently, is a key state variable in advanced ecosystem models. Remote sensing has been shown to be an effective tool for retrieving CWCs. However, the retrieval of the CWC from satellite [...] Read more.

Vegetation canopy water content (CWC) crucially affects stomatal conductance and photosynthesis and, consequently, is a key state variable in advanced ecosystem models. Remote sensing has been shown to be an effective tool for retrieving CWCs. However, the retrieval of the CWC from satellite remote sensing data is affected by the vegetation canopy structure and soil background. This study proposes a methodology that combines a modified spectral down-scaling model with a high-universality leaf water content inversion model to retrieve the CWC through constraining the impacts of canopy structure and soil background on CWC retrieval. First, canopy spectra acquired by satellite sensors were down-scaled to leaf reflectance spectra according to the probabilities of viewing the sunlit foliage (PT) and background (PG) and the estimated spectral multiple scattering factor (M). Then, leaf water content, or equivalent water thickness (EWT), was obtained from the down-scaled leaf reflectance spectra via a leaf-scale EWT inversion model calibrated with PROSPECT simulation data. Finally, the CWC was calculated as the product of the estimated leaf EWT and canopy leaf area index. Validation of this coupled model was performed using satellite-ground synchronous observation data across various vegetation types within the study area, affirming the model’s broad applicability. Results indicate that the modified spectral down-scaling model accurately retrieves leaf reflectance spectra, aligning closely with site-level measured spectra. Compared to the direct inversion approach, which performs poorly with Hyperion satellite images, the down-scale strategy notably excels. Specifically, the Similarity Water Index (SWI)-based canopy EWT coupled model achieved the most precise estimation, with a normalized Root Mean Square Error (nRMSE) of 15.28% and an adjusted R² of 0.77, surpassing the performance of the best index Shortwave Angle Normalized Index (SANI)-based model (nRMSE = 15.61%, adjusted R² = 0.52). Given its calibration using simulated data, this coupled model proved to be a potent method for extracting canopy EWT from satellite imagery, suggesting its applicability to retrieve other vegetative biochemical components from satellite data. Full article

(This article belongs to the Section Forest Inventory, Modeling and Remote Sensing)

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18 pages, 14491 KiB

Open AccessFeature PaperArticle

Influence of Main Flight Parameters on the Performance of Stand-Level Growing Stock Volume Inventories Using Budget Unmanned Aerial Vehicles

by Marek Lisańczuk, Grzegorz Krok, Krzysztof Mitelsztedt and Justyna Bohonos

Forests 2024, 15(8), 1462; https://doi.org/10.3390/f15081462 - 20 Aug 2024

Viewed by 848

Abstract

Low-altitude aerial photogrammetry can be an alternative source of forest inventory data and a practical tool for rapid forest attribute updates. The availability of low-cost unmanned aerial systems (UASs) and continuous technological advances in terms of their flight duration and automation capabilities makes [...] Read more.

Low-altitude aerial photogrammetry can be an alternative source of forest inventory data and a practical tool for rapid forest attribute updates. The availability of low-cost unmanned aerial systems (UASs) and continuous technological advances in terms of their flight duration and automation capabilities makes these solutions interesting tools for supporting various forest management needs. However, any practical application requires a priori empirical validation and optimization steps, especially if it is to be used under different forest conditions. This study investigates the influence of the main flight parameters, i.e., ground sampling distance and photo overlap, on the performance of individual tree detection (ITD) stand-level forest inventories, based on photogrammetric data obtained from budget unmanned aerial systems. The investigated sites represented the most common forest conditions in the Polish lowlands. The results showed no direct influence of the investigated factors on growing stock volume predictions within the analyzed range, i.e., overlap from 80 × 80 to 90 × 90% and GSD from 2 to 6 cm. However, we found that the tree detection ratio had an influence on estimation errors, which ranged from 0.6 to 15.3%. The estimates were generally coherent across repeated flights and were not susceptible to the weather conditions encountered. The study demonstrates the suitability of the ITD method for small-area forest inventories using photogrammetric UAV data, as well as its potential optimization for larger-scale surveys. Full article

(This article belongs to the Special Issue Application of Active and Passive Remote Sensors in the Forest Inventory)

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26 pages, 10877 KiB

Open AccessArticle

Phytosociological Analysis of the Boreal Oligotrophic Pine Forests in the Southern Ural Region (Russia)

by Vasiliy Martynenko, Pavel Shirokikh, Elvira Baisheva, Albert Muldashev, Nikolay Fedorov, Svetlana Zhigunova and Leniza Naumova

Forests 2024, 15(8), 1461; https://doi.org/10.3390/f15081461 - 20 Aug 2024

Viewed by 774

Abstract

Floristic composition and syntaxonomy of the boreal oligotrophic pine forests covering vast areas in the boreal, hemiboreal, and temperate zones of continental Eurasia still remain poorly studied in the Southern Ural region. Using the Braun–Blanquet approach and TURBOVEG and JUICE software, the phytocoenotic [...] Read more.

Floristic composition and syntaxonomy of the boreal oligotrophic pine forests covering vast areas in the boreal, hemiboreal, and temperate zones of continental Eurasia still remain poorly studied in the Southern Ural region. Using the Braun–Blanquet approach and TURBOVEG and JUICE software, the phytocoenotic diversity of boreal oligotrophic pine forests of the Southern Ural region was studied, and their position in the system of ecological and floristic classification of Eurasian vegetation was determined. Geobotanical data on boreal oligotrophic pine forests of Europe, including the European part of Russia; the Southern Urals; and Siberia were compared. A new alliance of oligotrophic boreal pine forests Brachypodio pinnati-Pinion sylvestris all. nov. hoc loco is described. The communities of this new alliance (i.e., five associations from the Southern Ural region) are characterized by a special floristic composition, occupying an intermediate position between the typical European oligotrophic pine forests of the alliance Dicrano-Pinion (Libbert 1933) Matuszkiewicz 1962 and oligotrophic (mainly psammophilous) South Siberian pine forests of the alliance Hieracio-Pinion Anenkhonov et Chytrý 1998. The communities of the alliance Brachypodio pinnati-Pinion sylvestris prefer to grow on poor soils with different moisture conditions. Due to intensive forestry activities, the distribution area of these forests has decreased, and these communities have been replaced by secondary birch forests. We have proposed a set of conservation measures to preserve these communities. A new association of oligotrophic pine forests Psephello sumensis-Pinetum sylvestris ass. nov. hoc loco is also described. These communities from the Kurgan region of Western Siberia were ordered into the alliance Dicrano-Pinion. It confirms the idea that the distribution area of this alliance may reach Siberia. Unlike the Southern Ural pine forests of the alliance Brachypodio pinnati-Pinion sylvestris, the recovery of these West Siberian pine forests after felling is quite high, and these communities do not require special measures for their protection. Full article

(This article belongs to the Special Issue Forest Biodiversity Conservation)

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Localities of relevés of boreal oligotrophic pine forests in the SUR and the Kurgan region. Full article ">Figure 2
Distribution of syntaxa of boreal oligotrophic pine forests in the SUR and the Kurgan region. Full article ">Figure 3
Tree diagram (Ward’s method, Bray-Curtis distances) of 61 syntaxa of boreal oligotrophic pine forests from alliances Cladonio stellaris-Pinion sylvestris (A: 1–16), Dicrano-Pinion (B: 17–42), Brachypodio-Pinion (C: 43–51, red color), Hieracio-Pinion (D: 52–61). Numbers in the tree diagram correspond to the numbers of the syntaxa in <a href="#app1-forests-15-01461" class="html-app">Table S1</a>. Full article ">Figure 4
Boreal oligotrophic pine forests in the SUR (authors of photos Shirokikh P.S., Muldashev A.A. ((a) Ass. Zigadeno sibirici-Pinetum sylvestris; (b) Ass. Pleurospermo uralensis-Pinetum sylvestris, subass. digitalietosum grandiflorae; (c) Ass. Pleurospermo uralensis-Pinetum sylvestris, subass. anemonastretosum biarmiensis). Full article ">

13 pages, 9031 KiB

Open AccessArticle

Impacts of Downed Dead Wood Poplar Trees on Forest Regeneration in the Semi-Arid Region of Northern China

by Pengwu Zhao, Lijuan Guan, Huaxia Yao, Yang Shu, Yongjie Yue, Furen Liu, Yaxiong Zheng, Longfei Hao, Changlin Xiang and Liwen Zhou

Forests 2024, 15(8), 1460; https://doi.org/10.3390/f15081460 - 19 Aug 2024

Viewed by 748

Abstract

In the past few decades, due to rising temperatures and changes in precipitation, the degree of drought in semi-arid areas has increased, leading to a large number of tree deaths and threatening the natural forests distributed in the semi-arid areas of North China. [...] Read more.

In the past few decades, due to rising temperatures and changes in precipitation, the degree of drought in semi-arid areas has increased, leading to a large number of tree deaths and threatening the natural forests distributed in the semi-arid areas of North China. This article takes the forest ecosystem of Saihanwula Nature Reserve in the southern section of Greater Khingan Mountains in China’s semi-arid region as a research area and studies the distribution of downed dead wood and its impact on forest renewal in the area. We used the sample plot survey method, investigated the number of downed dead wood, decay class, dumping direction, existence form, and the number of regenerated seedlings in the sample plot, and calculated the density of regenerated seedlings in different plots. The renewal density is 4050 ± 824, 2950 ± 265, plants/ha, and 2625 ± 237 plants/ha, respectively, in the sample plots for Later-death plot, Mid-death plot, and Early-death plot. The average storage of downed dead wood in Saihanwula Nature Reserve is 58.51 ± 16.56 m³/ha. The distribution densities of downed dead wood are 50 ± 21, 806 ± 198, 189 ± 76, and 22 ± 5 plants/ha for decay classes II, III, IV, and V respectively. The main form of downed dead wood in the research area is “trunk base fracture”, accounting for 68.78% of the total number of downed dead wood. A large number of downed dead wood had serious negative effects, such as crushing and injuring the regeneration seedlings and other plants under the forest at the moment of dumping and for a long time after dumping. The crushed and injured rate is 5.3~7.8%, with downed dead wood accumulated in the forest from the early stage of downed dead wood. It had negative effects on the regeneration of seeds, seedlings, and young trees, such as obstructing and hiding the light from the soil surface and inhibiting the regeneration and growth of seedlings. However, after the trees were dumped, large gaps appeared in the forest, increasing the sunlight area on the soil surface. In the later stage of tree death, moderately high decayed downed dead wood changed the soil structure in terms of soil softness, water holding capacity, and nutrient content, thus promoting the growth of seedlings and young trees. Reasonably utilizing the relationship between downed dead wood and forest renewal can effectively promote the healthy development of forests. Full article

(This article belongs to the Special Issue Ecosystem Degradation and Restoration: From Assessment to Practice)

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Location and site characteristics of the study area. Upper left: The location of the study area (green triangle) in northern China, with Inner Mongolia shown in light blue color. Center left: Elevation map of the Saihanwula Nature Reserve. Right and bottom row: Four pictures showing the landscape and downed dead wood. Full article ">Figure 2
The generation process of downed dead wood, regeneration approach of seedlings, and decay class of downed dead wood. Full article ">Figure 3
Downed dead wood reserves in Saihanwula Nature Reserve forest. Full article ">Figure 4
The distribution of downed dead wood in plots. Full article ">Figure 5
Decay class of downed dead wood in Saihanwula Nature Reserve forest. Full article ">Figure 6
Precipitation and temperature changes from 1961 to 2022. Full article ">Figure 7
The regeneration density of Saihanwula Nature Reserve forest. Note: “NS” is no significance (p > 0.05) for the difference between two plots. Full article ">Figure 8
The crushed and injured of downed dead wood in Saihanwula Nature Reserve forest. Full article ">

23 pages, 10102 KiB

Open AccessArticle

Heat Mitigation Benefits of Street Tree Species during Transition Seasons in Hot and Humid Areas: A Case Study in Guangzhou

by Senlin Zheng, Caiwei He, Haodong Xu, Jean-Michel Guldmann and Xiao Liu

Forests 2024, 15(8), 1459; https://doi.org/10.3390/f15081459 - 19 Aug 2024

Viewed by 772

Abstract

The potential microclimatic effects of street trees are influenced by their ecological characteristics, planting patterns, and street orientations, especially in subtropical hot and humid areas. To investigate these effects, four typical street tree species in Guangzhou were selected for study during the transition [...] Read more.

The potential microclimatic effects of street trees are influenced by their ecological characteristics, planting patterns, and street orientations, especially in subtropical hot and humid areas. To investigate these effects, four typical street tree species in Guangzhou were selected for study during the transition seasons: Khaya senegalensis, Terminalia neotaliala, Ficus microcarpa, and Mangifera indica. Air temperature (AT), relative humidity (RH), solar radiation (SR), surface temperature (ST), wind speed (WS), and the leaf area index (LAI) were monitored. The cooling effects of these four species and the resulting improvements in human thermal comfort (HTC) were assessed. The influences of tree planting patterns and street orientations on cooling benefits were systematically analyzed. The results indicate that, during transition seasons, the four street trees, on average, can block 96.68% of SR, reduce AT by 1.45 °C and ST by 10.25 °C, increase RH by 5.26%, and lower the physiologically equivalent temperature (PET) by 8.34 °C. Terminalia neotaliala, reducing AT and PET by 1.76 °C and 12.4 °C, respectively, offers the greatest potential for microclimate improvement. Among the four tree species, the variations in ST (ΔST) and PET (ΔPET) were minimal, at only 0.76 °C and 0.25 °C, respectively. The average differences in AT and PET between inter-tree and under-tree environments were 0.06 °C and 0.98 °C, respectively. The AT reduction rate was 1.7 times higher in the double-row planting pattern compared to the single-row planting pattern. Street trees planted in the northwest–southeast (NW-SE) orientation exhibited a 16.96% lower WS reduction than those in other orientations. The northeast–southwest (NE-SW) orientation showed the least potential to enhance human thermal comfort. Compared to NE-SW, the northwest–southeast (NW-SE) orientation achieved twice the rate of AT reduction, while the north–south (N-S) orientation improved it by 1.3 times. This data analysis aids in assessing the impact of green infrastructure on urban climates and demonstrates the year-round microclimatic benefits of street trees. Full article

(This article belongs to the Topic Biophilic Cities and Communities: Human-Environment Interaction and Sustainable Governance)

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15 pages, 2505 KiB

Open AccessArticle

Is It Possible to Predict a Forest Insect Outbreak? Backtesting Using Remote Sensing Data

by Anton Kovalev, Olga Tarasova, Vladislav Soukhovolsky and Yulia Ivanova

Forests 2024, 15(8), 1458; https://doi.org/10.3390/f15081458 - 19 Aug 2024

Viewed by 1107

Abstract

In this study, methods are proposed for analyzing the susceptibility of forest stands to attacks by forest insects on the basis of Earth remote sensing data. As an indicator of the state of forest stands, we proposed to use a parameter of the [...] Read more.

In this study, methods are proposed for analyzing the susceptibility of forest stands to attacks by forest insects on the basis of Earth remote sensing data. As an indicator of the state of forest stands, we proposed to use a parameter of the sensitivity of a vegetation index (normalized difference vegetation index; NDVI) during a vegetative period to changes in the radiative temperature of the territory (land surface temperature; LST) determined from satellite data of the Terra/Aqua system. The indicator was calculated as a spectrum of a response function in an integral equation linking changes of NDVI to those of LST. Backtesting was carried out using data from two outbreaks of the Siberian silk moth Dendrolimus sibiricus Tschetv. and outbreaks of the white mottled sawyer Monochamus urussovi Fischer and of the four-eyed fir bark beetle Polygraphus proximus Blandford in taiga forests of Krasnoyarsk Territory in Russia. In addition, the state of fir stands in the year 2023 was examined when damage to the forest stands was not yet noticeable, but Siberian silk moth adults were found in pheromone traps. It was shown that the proposed indicator of susceptibility of forest stands changed significantly 2–3 years before the pest outbreak in outbreak foci of the studied areas. Thus, the proposed indicator can be used to predict outbreaks of insect pests. The proposed approach differs from commonly used remote sensing methods in that, rather than using absolute values of remote indicators (such as, for example, NDVI), it focuses on indicators of the susceptibility of these remote indicators to the characteristics of the natural environment. Since any given point on the planet is characterized by a seasonally varying temperature, it is always possible to determine the sensitivity of a remote sensing indicator to changes in the environment that are not directly related to the absolute value of the indicator. Future studies are expected to examine susceptibility indices as a function of forest stand location and species, and to examine the length of spatial correlation of susceptibility indices, which may provide information on the possible extent of future insect outbreaks. Full article

(This article belongs to the Special Issue Risk Assessment and Management of Forest Pest Outbreaks)

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20 pages, 2086 KiB

Open AccessArticle

How Can Ecological Product Value Realization Sustainably Enhance the Well-Being of Farmers? A Case Study of Xingyuan Village in China

by Yanqiang Du, Jiying Wang and Juankun Li

Forests 2024, 15(8), 1457; https://doi.org/10.3390/f15081457 - 19 Aug 2024

Viewed by 932

Abstract

Although recent years have witnessed a considerable increase in studies on the economic value of ecological products, the extant literature has overlooked the multidimensional enhancement of ecological product value from the perspective of farmers’ well-being. This research aims to examine how the Realization [...] Read more.

Although recent years have witnessed a considerable increase in studies on the economic value of ecological products, the extant literature has overlooked the multidimensional enhancement of ecological product value from the perspective of farmers’ well-being. This research aims to examine how the Realization of Ecological Product Value (EPVR) serves as a crucial pathway to promoting the overall well-being of farmers in developing countries. Through a case study of a village in southeastern China, this research reveals that EPVR can enhance farmers’ well-being via various mechanisms as follows: (1) Economic solution to enrich farmers’ livelihood diversity, achieved by leveraging rural resource endowments and comparative advantages; (2) Fair social protection program enabling farmers to enjoy ecological benefits and further achieving urban-rural integration; (3) Environmental protection plan that balances production, living, and ecology; and (4) Grassroots governance tool promoting the governance ability to form collaborative governance model in a community of shared interests. This study offers theoretical support for enhancing human well-being through the realization of ecological product value in rural areas. Full article

(This article belongs to the Special Issue Forest Ecosystem Services and Strategy Development)

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15 pages, 6347 KiB

Open AccessArticle

Distribution Characteristics and Driving Factors of the Bacterial Community Structure in the Soil Profile of a Discontinuous Permafrost Region

by Qilong Liu, Liquan Song, Siyuan Zou, Xiaodong Wu and Shuying Zang

Forests 2024, 15(8), 1456; https://doi.org/10.3390/f15081456 - 18 Aug 2024

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Abstract

Global warming leads to the melting of permafrost, affects changes in soil microbial community structures and related functions, and contributes to the soil carbon cycle in permafrost areas. Located at the southern edge of Eurasia’s permafrost region, the Greater Khingan Mountains are very [...] Read more.

Global warming leads to the melting of permafrost, affects changes in soil microbial community structures and related functions, and contributes to the soil carbon cycle in permafrost areas. Located at the southern edge of Eurasia’s permafrost region, the Greater Khingan Mountains are very sensitive to climate change. Therefore, by analyzing the bacterial community structure, diversity characteristics, and driving factors of soil profiles (active surface layer, active deep layer, transition layer, and permafrost layer) in this discontinuous permafrost region, this research provides support for the study of the carbon cycling process in permafrost regions. The results show that the microbial diversity (Shannon index (4.81)) was the highest at 0–20 cm, and the Shannon index of the surface soil of the active layer was significantly higher than that of the other soil layers. Acidobacteria and Proteobacteria were the dominant bacteria in the active layer soil of the permafrost area, and Chloroflexi, Actinobacteria, and Firmicutes were the dominant bacteria in the permafrost layer. Chloroflexi made the greatest contribution to the bacterial community in the permafrost soil, and Bacteroidota made the greatest contribution to the bacterial community in the active surface soil. The structure, richness, and diversity of the soil bacterial community significantly differed between the active layer and the permafrost layer. The number of bacterial species was the highest in the active layer surface soil and the active layer bottom soil. The difference in the structure of the bacterial community in the permafrost soil was mainly caused by changes in electrical conductivity and soil–water content, while that in the active layer soil was mainly affected by pH and soil nutrient indices. Soil temperature, NO₃⁻-N, and pH had significant effects on the structure of the bacterial community. The active layer and permafrost soils were susceptible to environmental information processing and genetic information processing. Infectious disease: the number of bacterial species was significantly higher in the surface and permafrost layers than in the other layers of the soil. In conclusion, changes in the microbial community structure in soil profiles in discontinuous permafrost areas sensitive to climate change are the key to soil carbon cycle research. Full article

(This article belongs to the Section Forest Soil)

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(a) Study area location map. (b) Soil profile in permafrost area (0–20 cm: upper active layer; 20–60 cm: lower active layer; 60–80 cm: transition layer; 80–120 cm: permafrost layer). Full article ">Figure 2
Venn diagram of the structure of the soil bacterial community at different OTU levels in the permafrost region. Full article ">Figure 3
Principal coordinate analysis (PCoA) of soil bacteria in different soil layers. Full article ">Figure 4
Composition of soil microbial communities in different soil layers: (a) analysis at phylum level; (b) analysis at genus level. Full article ">Figure 5
Difference analysis of dominant soil microbial species in different soil layers: (a) analysis at phylum level; (b) analysis at genus level. * p < 0.05; ** p < 0.01; *** p < 0.001. Full article ">Figure 6
Correlation analysis of soil physicochemical properties and relative abundance of the major bacterial phyla. * p < 0.05; ** p < 0.01. Full article ">Figure 7
Analysis of the prediction function of microbial communities in different soil layers: (a) grade 1 functional group; (b) grade 2 functional group. a, b, c: If there is one identical marking letter, the difference is not significant, and if there is different marking letter, the difference is significant. Full article ">Figure 8
(a) Analysis of the metabolic pathways of soil bacteria regulated by thawing permafrost. The red line represents the positive path, and the blue line represents the negative path. Insignificant effects are indicated by dotted arrows. * p < 0.05, ** p < 0.01, *** p < 0.001. (b) Normalization effects between variables in different permafrost regions (direct and indirect normalization effects). Full article ">

22 pages, 10272 KiB

Open AccessArticle

Monitoring of Flash Drought on the Loess Plateau and Its Impact on Vegetation Ecosystems

by Yanmin Jiang, Haijing Shi, Zhongming Wen, Xihua Yang, Youfu Wu, Li Li, Yuxin Ma, John R. Dymond, Minghang Guo, Junfeng Shui and Hong Hu

Forests 2024, 15(8), 1455; https://doi.org/10.3390/f15081455 - 18 Aug 2024

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Abstract

Flash drought (FD) has attracted much attention due to its severe stress on vegetation ecosystems. Yet to date, the impacts of FD on vegetation ecosystems in different regions have not been fully evaluated and explored, especially for ecologically fragile areas. In this study, [...] Read more.

Flash drought (FD) has attracted much attention due to its severe stress on vegetation ecosystems. Yet to date, the impacts of FD on vegetation ecosystems in different regions have not been fully evaluated and explored, especially for ecologically fragile areas. In this study, we identified the FD events in the Loess Plateau from 2000 to 2023 based on the attenuation rate in soil moisture percentile over time. The evolution process of FD, the driving roles of meteorological conditions and the responses of different vegetation types to FD were explored by vegetation indicators such as solar-induced chlorophyll fluorescence (SIF), SIF_yield, SIF-RCI, etc. The results showed that FD events were predominantly concentrated in wetter areas with dense vegetation, with the highest frequency being 29. Meteorological factors contributed differently to the occurrence and development of FD. The responses of vegetation to FD were not only related to vegetation types (cropland was more sensitive to FD than forest and grassland) but were also significantly influenced by background climate. The SIF_yield anomaly of vegetation was more sensitive than SIF anomaly and SIF-RCI. The results advance our understanding of the formation mechanisms of FD and facilitate the exploration of vegetative photosynthetic responses to FD. Full article

(This article belongs to the Special Issue Application of Remote Sensing in Vegetation Dynamic and Ecology)

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12 pages, 3083 KiB

Open AccessArticle

Needle Biomass Turnover Rate in Scots Pine Stands of Different Ages

by Mieczysław Turski, Ignacy Korczyński, Adrian Łukowski and Andrzej Węgiel

Forests 2024, 15(8), 1454; https://doi.org/10.3390/f15081454 - 18 Aug 2024

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Abstract

Understanding needle biomass turnover rates in Scots pine (Pinus sylvestris L.) stands is crucial for modelling forest ecosystem dynamics and nutrient cycling. This study examined needle litterfall and biomass turnover in Scots pine stands of varying ages in temperate forests (western Poland). [...] Read more.

Understanding needle biomass turnover rates in Scots pine (Pinus sylvestris L.) stands is crucial for modelling forest ecosystem dynamics and nutrient cycling. This study examined needle litterfall and biomass turnover in Scots pine stands of varying ages in temperate forests (western Poland). The research focused on determining how stand age affects needle biomass, litterfall and the associated turnover rates. Data were collected from 20 Scots pine stands aged 26 to 90 years, and needle litterfall was measured and analysed in relation to stand characteristics such as age, density and biomass. The average annual needle litter production of the sampled Scots pine stands was 2008 kg·ha⁻¹·year⁻¹, similar to the values previously reported for this tree species in other temperate forests in Europe. The average needle biomass turnover rate for sampled Scots pine stands was 23.4%. We could not support the hypothesis that this parameter depended on the age of the Scots pine stand. The needle biomass turnover rate showed a positive correlation with crown length and a negative correlation with stand density due to the very weak correlations; however, further research is needed to confirm these relationships. Despite this, the parameter can be used to estimate needle litterfall and can be applicable to conditions corresponding to those of temperate forests in Central and Western Europe. This study also highlights the need for further research on needle biomass turnover in temperate forests to improve the accuracy of carbon and nutrient cycling models. This work contributes to a deeper understanding of the role of needle litterfall in maintaining soil fertility and forest productivity, offering insights into sustainable forest management and conservation strategies. Full article

(This article belongs to the Special Issue Biomass Estimation and Carbon Stocks in Forest Ecosystems: 2nd Edition)

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17 pages, 4059 KiB

Open AccessArticle

Factors Influencing the Change of Phyllosphere Microbial Community of Three Populus spp. in the Same Habitat

by Xin Yin, Weixi Zhang, Dan Li, Ran Wang, Xinyao Cong, Zhongyi Pang, Yanhui Peng, Yang Ge, Wenxu Zhu and Changjun Ding

Forests 2024, 15(8), 1453; https://doi.org/10.3390/f15081453 - 18 Aug 2024

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Abstract

Plant leaves harbor a rich diversity of bacteria and fungi that, through their interactions with host plants, assume an influential role in plant physiological and metabolic processes. The unique phyllosphere environment of different plant species may shape and select distinct phyllosphere microbial communities. [...] Read more.

Plant leaves harbor a rich diversity of bacteria and fungi that, through their interactions with host plants, assume an influential role in plant physiological and metabolic processes. The unique phyllosphere environment of different plant species may shape and select distinct phyllosphere microbial communities. While most academic research has focused on the phyllosphere microorganisms within the same plant variety, there is relatively limited research on the phyllosphere microbial communities between different varieties. Populus L. is a typical tree species in temperate monsoon climates, widely distributed in northern China, and it constitutes a crucial component of China’s forestry resources. For the purpose of this study, we investigated the community structure and diversity of phyllosphere fungi and bacteria in different poplar varieties under identical growth conditions to elucidate the main factors contributing to differences in phyllosphere microbial communities among these varieties. Our findings revealed variations in nitrogen, phosphorus, starch, and soluble sugar contents among the three poplar species studied. Additionally, there were considerable disparities in both abundance and α diversity index of phyllosphere fungal and bacterial communities among these species. At the phylum level, Ascomycota and Basidiomycota have been identified as the dominant fungal communities; while Proteobacteria and Actinomycetes were dominant bacterial communities. The correlation analysis pointed out that chemical traits in the leaves, in particular the total phosphorus and the quantity of soluble sugar, had a significant correlation with the structure and diversity of the microbial community residing in the phyllosphere. Overall, our results demonstrate that even under identical site conditions, each poplar species harbors its own unique phyllosphere microbial community composition as well as distinct leaf characteristics—highlighting host plant diversity as a crucial factor driving differences in phyllosphere microbial composition. Full article

(This article belongs to the Special Issue The Synergistic Response of Ecosystem Vegetation and Soil Microorganisms under the Background of Global Change)

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Venn diagram illustrating unique and shared ASVs of phyllosphere microbial community for three different samples. (a) Unique and shared ASVs of phyllosphere fungal communities in three different samples; (b) Unique and shared ASVs of phyllosphere bacteria communities in three different samples. Full article ">Figure 2
Rarefaction Curve. The observed diversity of samples is influenced by the sequencing depth, which is reflected in the flattening of the curve. The lack of steepness in the curve suggests that the sequencing outcomes successfully reflect the existing diversity within the current samples, encompassing numerous novel ASVs. Conversely, a non-flattened curve suggests that alpha diversity has not reached saturation. (a) Rarefaction Curve of fungi. (b) Rarefaction Curve of bacteria. Full article ">Figure 3
Phyllosphere microbial diversity (* Reveals a notable variance with a confidence level of 95%. The black line represents a direct and significant difference between the two) (a) Alpha diversity analysis of phyllosphere fungal community. (b) Alpha diversity analysis of phyllosphere bacterial community. Full article ">Figure 4
Analysis of taxonomic composition at the phylum level. (a) Analysis of fungal taxonomic composition at the phylum level. (b) Analysis of bacterial taxonomic composition at the phylum level. Full article ">Figure 5
Analysis of taxonomic composition at the genus level. (a) Analysis of fungal taxonomic composition at the genus level. (b) Analysis of bacterial taxonomic composition at the genus level. Full article ">Figure 6
Hierarchical clustering analysis of phyllosphere microbial communities of different Populus spp. (at the genus level). (a) Hierarchical clustering analysis of phyllosphere fungal communities of different Populus spp. (b) Hierarchical clustering analysis of phyllosphere bacterial communities of different Populus spp. Full article ">Figure 7
LEFse analysis of phyllosphere fungal and bacterial community at the genus level. (a) LEFse analysis of phyllosphere fungal community at the genus level. (b) LEFse analysis of phyllosphere bacterial community at the genus level. Full article ">Figure 8
Correlation heatmap of leaf nutrient factors and α diversity of phyllosphere fungal and bacterial community. (a) Correlation heatmap of leaf nutrient factors and α diversity of phyllosphere fungal community. (b) Correlation heatmap of leaf nutrient factors and α diversity of phyllosphere bacterial community. * indicates that there is a significant correlation at the level of p < 0.05; ** indicates a significant correlation at the level of p < 0.01. Full article ">Figure 9
Correlation heatmap of leaf nutrient factors and α diversity of phyllosphere fungal and bacterial community at genus level. (a) Correlation heatmap of leaf nutrient factors and α diversity of phyllosphere fungal community at genus level. (b) Correlation heatmap of leaf nutrient factors and α diversity of phyllosphere bacterial community at genus level. * signifies a statistically significant correlation at p < 0.05, whereas ** denotes an even stronger statistical significance at p < 0.01. Full article ">

21 pages, 6440 KiB

Open AccessArticle

Improving Urban Forest Expansion Detection with LandTrendr and Machine Learning

by Zhe Liu, Yaru Zhang and Xi Zheng

Forests 2024, 15(8), 1452; https://doi.org/10.3390/f15081452 - 17 Aug 2024

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Abstract

Annual urban forest expansion dynamics are crucial for assessing the benefits and potential issues associated with vegetation accumulation over time. LandTrendr (Landsat-Based Detection of Trends in Disturbance and Recovery) can efficiently detect the dynamics of interannual land cover change, but it has difficulty [...] Read more.

Annual urban forest expansion dynamics are crucial for assessing the benefits and potential issues associated with vegetation accumulation over time. LandTrendr (Landsat-Based Detection of Trends in Disturbance and Recovery) can efficiently detect the dynamics of interannual land cover change, but it has difficulty distinguishing urban forest expansion from urban surface rapid conversions, as changes are usually filtered by magnitude-of-change thresholds. To accurately detect annual urban forest expansion dynamics, we developed an improved method using random forest-supervised classification to filter urban forests. We further enhanced the performance of the improved method by incorporating trend features between segments. Additionally, we tested two threshold-based filtering baseline methods. These methods were tested with various spectral and parameter combinations in Beijing’s Central District and the 1st Greenbelt from 1994 to 2022. The improved method with trend features achieved the highest average accuracy of 89.35%, representing a 25% improvement over baseline methods. Post-change trend features aided in accurate identification, while quantitative features rather than extremum features were more important in filtering. The improved method with trend features tested in Beijing’s 2nd Greenbelt also showed an accuracy of 88.27%, confirming its stability. SWIR2 and a higher maximum segment number are efficient for filtering by providing the most detailed dynamics. Accurate annual expansion dynamic mapping offers insights into change rates and precise expansion years, providing a new perspective for urban forest research and management. Full article

(This article belongs to the Section Forest Inventory, Modeling and Remote Sensing)

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14 pages, 4349 KiB

Open AccessArticle

Alien Species Introduction and Demographic Changes Contributed to the Population Genetic Structure of the Nut-Yielding Conifer Torreya grandis (Taxaceae)

by Yuming Tan, Qian Ou, Xin Huang, Yujin Wang and Yixuan Kou

Forests 2024, 15(8), 1451; https://doi.org/10.3390/f15081451 - 17 Aug 2024

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Abstract

Understanding population genetic structure and its possible causal factors is critical for utilizing genetic resources and genetic breeding of economically important plants. Although Torreya grandis is an important conifer producing nuts in China, little is known about its population structure, let alone the [...] Read more.

Understanding population genetic structure and its possible causal factors is critical for utilizing genetic resources and genetic breeding of economically important plants. Although Torreya grandis is an important conifer producing nuts in China, little is known about its population structure, let alone the causal factors that shaped its genetic variation pattern and population structure. In this work, we intended to characterize the genetic variation pattern and population structure of the nut-yielding conifer T. grandis throughout its whole geographical distribution and further explore the potentially causal factors for the population structure using multiple approaches. A moderate level of genetic diversity and a novel population structure were revealed in T. grandis based on eleven robust EST-SSR loci and three chloroplast fragments. Alien genetic composition derived from the closely related species T. nucifera endemic to Japan was detected in the Kuaiji Mountain area, where the seed quality of T. grandis is considered the best in China. Demography history and niche modeling were inferred and performed, and the contribution of geographic isolation to its population structure was compared with that of environmental isolation. Significant demographic changes occurred, including a dramatic population contraction during the Quaternary, and population divergence was significantly correlated with geographic distance. These results suggested that early breeding activities and demographic changes significantly contributed to the population structure of T. grandis. In turn, the population structure was potentially associated with the excellent variants and adaptation of cultivars of T. grandis. The findings provide important information for utilizing genetic resources and genetic breeding of T. grandis in the future. Full article

(This article belongs to the Special Issue Genetic Variation and Adaptation of Forest Trees to Environmental Changes)

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Geographical distribution and network of chloroplast haplotypes (H1-H7) in T. grandis and its two closely related species, T. nucifera and T. jackii. The numbers 1-18 correspond to the population codes in <a href="#forests-15-01451-t001" class="html-table">Table 1</a>. The sizes of circles in the network are proportional to the haplotype frequencies, and the mutation steps among haplotypes of more than one are marked on each branch. The photograph on the right illustrates an ancient tree in population 16 (Zhuji, Zhejiang, China) that is more than 400 years old. Full article ">Figure 2
Population structure of T. grandis, its genetic relationship with T. nucifera and T. jackii, and the correlation of its population divergence with geographic distances. (a) Population structure was inferred using Structure analysis with the number of clusters (K) varying from 2 to 12 with different colors and (b) principal coordinates analysis (PCoA). The numbers 1-18 correspond to the population codes in <a href="#forests-15-01451-t001" class="html-table">Table 1</a>. (c) Correlation among genetic distances (FST) and geographic distances was estimated by the Mantel test. The blue circles and gray background refer to the genetic distances (FST) and confidence interval of the linear correlation, respectively. Full article ">Figure 3
Eight alternative demographic scenarios for T. grandis simulated by approximate Bayesian computation in DIYABC based on EST-SSR loci. N1 and N2 represent current population sizes, and NA represents the ancestral population size. N1a, N1b, N2a, and N2b represent population sizes between the ancestral population and the current population. t1 and t2 represent times of population changes. The optimal scenario is shown with gray background. Full article ">Figure 4
Climate niches of T. grandis predicted using ecological niche modeling in MAXENT. Predicted distributions are shown during present-day (PRESENT), Mid-Holocene (MH), Last Glacial Maximum (LGM), and Last Interglacial (LIG) climatic periods. Paleoclimate data for the MH, LGM, and LIG under MIROC model were employed. Full article ">Figure 5
The effects of heterogeneous environment on population genetic divergence evaluated using principal component analysis (PCA) of 19 bioclimatic variables. The numbers 1–16 correspond to the population codes in <a href="#forests-15-01451-t001" class="html-table">Table 1</a>. Four genetically distinct groups revealed in Structure analysis are shown with different colors. Full article ">

17 pages, 4904 KiB

Open AccessArticle

Reconstructing the Temperature and Precipitation Changes in the Northern Part of the Greater Khingan Mountains over the Past 210 Years Using Tree Ring Width Data

by Zhaopeng Wang, Dongyou Zhang, Tongwen Zhang, Xiangyou Li, Xinrui Wang, Taoran Luo, Shubing Zhong and Kexin Song

Forests 2024, 15(8), 1450; https://doi.org/10.3390/f15081450 - 16 Aug 2024

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Abstract

In northeastern China, simultaneous reconstruction of temperature and precipitation changes in the same region using tree ring data has not yet been reported, limiting our understanding of the historical climate. Using tree ring samples from the Greater Khingan Mountains, it was established that [...] Read more.

In northeastern China, simultaneous reconstruction of temperature and precipitation changes in the same region using tree ring data has not yet been reported, limiting our understanding of the historical climate. Using tree ring samples from the Greater Khingan Mountains, it was established that there are five standardized tree ring width chronologies of Pinus sylvestris var. mongolica at five elevations. Correlation analyses revealed significant relationships between the tree ring chronologies and climate data for multiple months. Specifically, the correlation coefficient between the average minimum temperature from May to July and the composite chronologies of mid–high and mid-elevations was 0.726, whereas that between the total precipitation from August to July and the low-elevation chronology was 0.648 (p < 0.01). Based on these findings, we reconstructed two series: the average minimum temperature from May to July over the past 211 years and the total precipitation from August to July over the past 214 years. The reconstructed sequences revealed changes in the average minimum temperature from 1812 to 2022 and precipitation from 1809 to 2022 in the northern part of the Greater Khingan Mountains. The variances explained by the reconstruction equations were 0.528 and 0.421 (adjusted R-squared: 0.520 and 0.411), with F-test values of 65.896 and 42.850, respectively, exceeding the significance level of 0.01. The reliability of the reconstructed sequences was validated by historical records of meteorological disasters and the reconstruction results in the surrounding area. The reconstructed temperature and precipitation sequences exhibited distinct patterns of temperature fluctuations, dry–wet changes, and periodic oscillations. The region experienced two warm periods (1896–1909 and 2006–2020), two cold periods (1882–1888 and 1961–1987), a wet period (1928–1938), a drought period (1912–1914), and a period prone to severe drought events (1893–1919) during the past 210 years. The temperature series showed periodicities of 2–2.5 years, 3.9 years, 5.2 years, and 68 years, while the precipitation series exhibited periodicities of 2.1 years, 2.5 years, and 2.8 years, possibly related to El Niño–Southern Oscillation (ENSO) events, quasi-biennial oscillation, and Pacific Decadal Oscillation (PDO). Spatial correlation analysis indicated that the reconstructed temperature and precipitation sequences accurately represented the hydrothermal changes in the study area. Full article

(This article belongs to the Section Forest Ecology and Management)

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