Ecological Indicators 119 (2020) 106831

Contents lists available at ScienceDirect

Ecological Indicators
journal homepage: www.elsevier.com/locate/ecolind

Land use change effects on soil organic carbon store. An opportunity to soils T
regeneration in Mediterranean areas: Implications in the 4p1000 notion
Beatriz Lozano-Garcíaa, Rosa Francavigliab, Gianluca Renzib, Luca Doroc,d, Luigi Leddac,
⁎
Concepción Beníteza, Manuel González-Rosadoa, Luis Parras-Alcántaraa,
a
SUMAS Research Group, Department of Agricultural Chemistry, Soil Science and Microbiology, Faculty of Science, Agrifood Campus of International Excellence - ceiA3,
University of Cordoba, 14071 Cordoba, Spain
b
Consiglio per la ricerca in agricoltura e l’analisi dell’economia agraria, Centro di ricerca Agricoltura e Ambiente, 00184 Rome, Italy
c
Università di Sassari, Dipartimento di Agraria, Sezione di Agronomia, Coltivazioni erbacee e Genetica, 07100 Sassari, Italy
d
Blackland Research and Extension Center, Texas A&M Agrilife Research, 720 East Blackland Road, Temple, TX 76502, USA

A R T I C LE I N FO A B S T R A C T

Keywords: The knowledge about land management effects on soil capacity to store carbon is necessary to planning effective
Land use change strategies by managers and decision-makers. In this study we analyzed the land use change (LUC) effects on soil
Revegetation organic carbon stocks (SOC-S) for long term in the Sardinia region - Italy (Mediterranean area).
Vineyard Throughout the 20th century, the studied area has undergone different LUC. The first LUC was in 1938, from
Carbonization
forest to agricultural land under three different uses: vineyards, hay crop and pasture, later (1966) some of this
Decarbonization
Recarbonization
agricultural land were abandoned to seminatural ecosystem (second LUC). The different LUC affected to SOC-S
Mediterranean areas causing decarbonization, carbonization and recarbonization processes along the soil profile.
The different land uses studied chronologically were: i) natural forest - cork oak forest (Cof), ii) tilled vineyard
(Tv), iii) no tilled grassed vineyard (Ntgv), iv) hay crop (Hc), v) pasture - silvopastoral and silvoarable practices
(P), and vi) former vineyard - vineyards abandoned and naturally revegetated (Fv). The first LUC (Cof to Tv,
Ntgv, Hc and P) caused 5.1% and 37.5% reduction on SOC-S for Tv and Ntgv (soil decarbonization), however,
the SOC-S increased 47.1% and 51.3% for Hc and P respectively (soil carbonization). The second LUC (Tv and
Ntgv to Fv) increased the SOC-S on average 66.3% (soil recarbonization). In general, these effects were observed
principally in depth.
This study shows the importance of land use and LUC with respect to SOC-S, and that the human action can
degrade and/or regenerate the soil, affecting to soil functions. Consequently, is necessity to promote good en-
vironmental practices to improve the soil functions and to reduce the greenhouse gases (ecosystem services). On
the presumption that the SOC sequestration through of agricultural management can reduced the atmospheric
CO2 concentration (4p1000 target in the XXI Conference of the Parties – Paris, 2015). Therefore, the soils
regeneration via carbonization and/or recarbonization is an opportunity to prevent the climate change.

1. Introduction services (ES). During the last century, this ecosystems alteration by LUC
have been accelerated particularly in Mediterranean areas (Steffen
The soil is a dynamic system over time (Hartemink, 2016), that is et al., 2011). This alteration usually has been based in the forest to
related to spatial and temporal aspects involving variation over space agricultural land conversion followed by an agriculture intensification
and alteration over time (Brevik and Arnold, 2015). Therefore, there is and the land abandon derived from the lack of economic benefits
a strong link between “time” and “soil formation processes” (Stevens (Fedele et al., 2018). LUC is considered the major driving forces of
and Walker, 1970), highlighting the relationship between time, land change in ecosystem functions in landscape pattern in Europe
management and land use change (LUC) by anthropogenic factors (Cernusca et al., 1996). In this line, LUC from forest to agricultural land
(Montanarella et al., 2016) in relation to soil evolution. is the origin of serious threats to soil stability and health, being the
The human actions over time has modified the landscape in Europe prime concerns the soil loss and degradation processes. Soil degradation
according to their necessities and benefits, affecting to ecosystem by LUC is a serious global problem (Pereira and Martinez-Murillo,

⁎
Corresponding author.
E-mail addresses: luis.parras@uco.es, qe1paall@uco.es (L. Parras-Alcántara).

https://doi.org/10.1016/j.ecolind.2020.106831
Received 18 November 2019; Received in revised form 12 May 2020; Accepted 7 August 2020
Available online 19 August 2020
1470-160X/ © 2020 Elsevier Ltd. All rights reserved.
B. Lozano-García, et al. Ecological Indicators 119 (2020) 106831

2018), all of this without forgetting that the LUC impact is conditioned proposal was an international programme to increase the global soil
by land use type and by others abiotic factors (Schrumpf et al., 2011). OM stocks by 0.4% per year to compensate the global emissions of
The Mediterranean forests were extensively transformed to agro- greenhouse gases by anthropogenic sources. This proposal would in-
forestry systems, and in many Mediterranean areas the agriculture volve a SOC-S increase of 0.6 tons of C per hectare per year on average
abandonment determined the agroforestry systems formation again. globally in the first 40 cm soil depth (Chabbi et al., 2017; Minasny
Due to low yields and the high cost of modern tillage equipment, the et al., 2017) initially for 20 years (Poulton et al., 2017). With this
agricultural lands were abandoned, suffering a second LUC, from the proposal, it would be possible to eliminate from the atmosphere the
agricultural land to a new vegetation cover due to land abandonment. annual CO2-C emissions from fossil fuels (8.9 Gt C). Really it is a good
This land abandonment implies an soil risks derived from LUC such as initiative, but we must be careful, as it has certain limitations (Chabbi
soil erosion and soil degradation, but in some cases, offers to soil the et al., 2017; Lal, 2016; Minasny et al., 2017; Poulton et al., 2017;
opportunity to restore its quality and functions by revegetation (natu- Baveye et al., 2018). But, as Lal (2016) says, “the 4p1000 proposal
rally in some cases, and induced in others). By reforestation-revegeta- should be more about the concept than any specific numbers”.
tion these soils can increase their capacity to store soil organic carbon To determine exactly the LUC effects on soil C amount we must
(SOC) (Guo and Gifford, 2002; Metz et al., 2007). consider the SOC and the SOC-S quantification in the surface layer
The most extensive agroforestry systems in Europe is the (topsoil) and in the subsurface horizons (subsoil). In this line, many
Mediterranean evergreen oak woodlands (MEOW) with more than 3.1 researchers like Lozano-García et al. (2017) and Francaviglia et al.
Mha (million ha) (Moreno and Pulido, 2009). These ecosystems were (2017a) …among others, in agroforestry systems and in forest soils
created by clearing the natural Mediterranean forest. The MEOW has respectively, demonstrate the importance of the C amount store in
been considered habitats to be preserved, therefore they are an example subsoils and its significance in the soil role as C sink in Mediterranean
of sustainable land use (these systems have multiple uses and ex- areas. Therefore, it is necessary to study entire soil profile and not ex-
ploitations - e.g., livestock rearing, cereal cropping, cork and firewood clusively the soil surface horizon (topsoil), in addition, it is crucial the
harvesting, and hunting), although their conservation has been threa- sampling method (by horizons or by soil control sections - fixed depths)
tened in the last few decades (Moreno and Pulido, 2009). In these so that can affect to SOC-S quantification (Parras-Alcántara, et al.,
ecosystems, the trees act as “ecosystem engineers”, facilitating the grass 2015b; Francaviglia et al., 2017a). This simple consideration can affect
production maintenance in poor soils under semiarid climate (Parras- to SOC-S quantification so that the SOC-S may be overestimated or
Alcántara et al., 2015a). In addition, the MEOW (dehesa or sa- underestimated when the sampling is by soil control sections. Hence,
vanna ~ oak woodlands) offers ES (MEA, 2005; Marañón et al., 2012), sampling by horizon in entire soil profiles is recommended if the target
and one of the most important ES offered by this forests land is the soil is to evaluate and certify the SOC-S at regional scales, as sampling
carbon (C) storage (TEEB, 2010), therefore, the forest soils playing an should be based on soil natural properties (genetic horizons). Con-
important role in the C balance at global scale (Bayer et al., 2017). But sidering these matters, three key factors must be considered in relation
we must not forget that at worldwide scale the soil C storage is de- to SOC pools: (i) related to measurement scale, (ii) related to the
creasing (Jandl et al., 2007) and that Mediterranean forests are vul- methodology for SOC-S quantification and (iii) related to the sampling
nerable to C storage loss (Badalamenti et al., 2017). The amount of C methodology (entire soil profile by genetic horizon or soil control sec-
stored in forests soils is a substantial part of the total C storage in the tion at a specific depth). Subjects that should be obvious but show
world. Six et al. (2002) estimated that SOC stored in forest soils was uncertainty, in this line, Lal (2005) already indicated these considera-
70–73% of the global SOC amount. But more recently, Pan et al. (2011) tions with respect to complexity in the forest soils (sampling protocol
quantified the global forest C sinks and estimated the total SOC stock and scale of measurement). But more recently, Lal (2018) re-
(SOC-S) in 861 Pg (383 Pg: 45% in soil (1 m depth); 363 Pg: 42% in commended at least 50-cm depth, and preferably to 1 m depth to as-
above and belowground biomass; 73 Pg: 8% in deadwood and 43 Pg: sessing the SOC-S changes at different depths (0.3, 0.4, 0.5 and 1.0 m
5% in litter). depth) over 5 year period in relation to land use and management.
In forest soils, the trees modify the microclimatic conditions (prin- The main goal of this research was to quantify over time the effects
cipally moisture and temperature regimes) and increase the organic in the SOC-S, evaluating two LUC’s to assess the LUC effects in the SOC-
matter (OM) inputs and thus improving the soil quality (Bouwman and S within the entire soil profile, and its involvement in the 4p1000
Leemans, 1995). In addition, the tillage absence in these systems im- concept. And the specific objectives of this study were: i) determine the
proves the soil microbial and fauna communities and the formation of conversion effects from Mediterranean forest (natural forest - cork oak
stable aggregates (Jégou et al., 2000), providing protection against to forest) to different agricultural uses (tilled vineyard, no tilled grassed
OM decomposition (Del Galdo et al., 2003). Therefore, Mediterranean vineyard, hay crop, pasture - silvopastoral and silvoarable practices) on
forest soils have a great capacity to C store and C sequestration - C sink SOC-S and ii) determine the effect of natural revegetation to a semi-
(Roig and Rubio, 2009). natural condition on SOC-S after the abandonment agricultural land
Different meta-analysis have shown that the main factors that con- (vineyards).
tributing to SOC-S restoration after revegetation include: the prior land
use, the tree types planted, the soil clay content and the climate (Li 2. Materials and methods
et al., 2012; Olaya-Abril et al., 2017, 2018). Accordingly, by refor-
estation and/or revegetation of these soils can increase their SOC store 2.1. Site characterization
capacity (carbonization and/or recarbonization) (Guo and Gifford,
2002; Metz et al., 2007). However, the LUC from forest to agricultural The study was carried out in the Berchidda Municipality (Olbia-
land implies an important soil C loss (decarbonization) and its in- Tempio, Sardinia, Italy), and comprises an area of 1,470 ha, located
corporation (via emission) to the atmosphere, contributing to global between 40o46′ N; 9o10′ E (Fig. 1). This area is a hilly basin, with an
warming (Lal, 2005; Schulp et al., 2008). Despite this, the soils with average altitude of 302 m.a.s.l. (meters above sea level), ranging be-
permanent crops such vineyards, olive groves, nuts, and almonds in tween 275 and 340 m.a.s.l. The relief is smooth with slopes ranging
Mediterranean areas (with greater than 3 Mha) contribute to 3% of the from 3% to 8% and may reach values of 30%. The materials are in-
total SOC-S (Gómez, 2017). trusive natural granite accompanied by quartz and porphyry (Bevivino
In this sense, the 4p1000 initiative is a brilliant idea proposed by the et al., 2014). This region has pluvi-seasonal oceanic (low) meso-Medi-
French minister of agriculture Stéphane Le Foll during COP 21 in 2015 terranean and (low) sub-humid climate. The long-term mean annual air
(Soils for Food Security and Climate in Paris climate conference of the temperature is 15.0 °C ranging from 13.8 °C to 16.4 °C, and the annual
United Nations Framework Convention on Climate Change). This mean rainfall is 623 mm, varying between 367 and 811 mm in the

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B. Lozano-García, et al. Ecological Indicators 119 (2020) 106831

Fig. 1. Study area. Berchidda Municipality (Olbia-Tempio, Sardinia, Italy). UTM:32 T 513860.59 m – E 4515004.17 m.

period 1985–2006 (Servizio Agrometeorologico Regionale of Sardinia since a previous geo-statistical analysis allowed to assess the SOC spa-
Region). In general, the climate is warm temperate with dry and hot tial variability as a land use function (Francaviglia et al., 2014). Con-
summers (Csa) according to the Köppen-Geiger updated classification sequently, a higher number of samples were collected in the more
(Kottek et al., 2006). The most representative soils in the studied area heterogeneous land uses (Tv, Ntgv, P and Hc) in which samples were
are dystric and eutric Cambisols (IUSS Working Group WRB, 2015) collected in open areas (under the plants and in the inter-rows).
derived from granitic rocks. The soils are characterized by acid pH Nevertheless, a lower number of samples in Cof where collected, since
(5.1–6.2) and moderate base saturation, low fertility, poor physical vegetation was homogeneous. In the case of Fv land use was sampled
conditions (loamy sand, sand, and sandy loam textures) and a marginal under different conditions of natural revegetation (scrublands, Medi-
capacity for agricultural use (Lagomarsino et al., 2011; Francaviglia terranean maquis, and meadows).
et al., 2014).
The natural vegetation it is mainly formed by cork oak forest
(Quercus suber), a type of MEOW under extensive agroforestry system, 2.3. Soil sampling, analytical methods, and statistical analyses
considered an example of sustainable land use (Bagella and Caria,
2011). This cork oak forest (Cof) was partially converted to other land Soil samples were collected along the different soil horizons for each
uses in the last century: vineyard under two different managements - profile, thus avoiding the mixing of the pedogenic horizons and al-
tilled vineyards (Tv) and no-tilled grassed vineyards (Ntgv); hay crop lowing for a proper determination of physical and chemical soil prop-
(Hc) and pasture (P) under silvopastoral and silvoarable practices (first erties (Lal, 2005; Parras-Alcántara et al., 2015b; Francaviglia et al.,
half of the 20th century). Then, in the middle of the 20th century, some 2017a). A random sampling scheme was adopted, pits were digged with
vineyards were abandoned and were naturally revegetated to semi- a mini excavator, and samples for a general characterization of entire
natural systems (Fv) composed of scrublands, Mediterranean maquis, soil profiles were collected along the different soil horizons using a
and Helichrysum meadows. These six land uses were described in detail hand trowel. The maximum sampling distance was 1.6 km (between Tv
in Francaviglia et al. (2014). and Fv).
Samples were dried at a constant room temperature (25 °C) and
sieved (2 mm). The remaining gravel was weighed. Three laboratory
2.2. Experimental design. replications were performed for each soil sample. The analytical
methods used in this study to determine different soil properties are
The different land uses studied chronologically were: Cof, Tv, Ntgv, reported in Table 1.
Hc, P and Fv. The first LUC was from Cof to Tv, Ntgv, Hc and P (first The effect of land use and soil depth on SOC-S was analyzed using
half of the 20th century ≈ 1938) and the second LUC was from Tv and ANOVA (SPSS 13.0 for Windows). Data were tested for normality to
Ntgv to Fv (in the middle of the 20th century ≈ 1966) (Fig. 2). Samples verify the model assumptions, and differences of p < 0.05 were con-
from 26 soil profiles were collected under the six different land uses: 4 sidered statistically significant.
sampling points in Tv, 4 in Ntgv, 5 in Hc, 4 in P, 2 in Cof and 7 in Fv.
Soils were dystric Cambisols in Cof, Tv and P; and both dystric and
eutric Cambisols in Ntgv, Hc and Fv according to (IUSS Working Group
WRB, 2015). The sampling points number has not been done at random,

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B. Lozano-García, et al. Ecological Indicators 119 (2020) 106831

Fig. 2. Land uses studied chron-

ologically (chronosequence). Cof: Cork
oak forest, Tv: tilled vineyards, Ntgv:
no-tilled grassed vineyards, Hc: hay
crop, P: pasture under silvopastoral and
silvoarable practices, Fv: vineyards
abandoned and naturally revegetated to
semi-natural systems (scrublands,
Mediterranean maquis, and
Helichrysum meadows).

Table 1 respectively (Table 2). In general, the trend was to increase in depth
Analytical methods used in this study. except for Cof and P that decreased. This behavior may be due to the
Parameters Method
stone line presence as postulated Symith and Montgomery (1962) and
by the tillage used that removes large amount of stones and boulders
Bulk density (Mg m−3) Core method (Blake and Hartge, 1986) (Fernández-Romero et al., 2014). It is important to point out that soil
Particle size distribution Robinson pipette method (USDA, 2004) gravel content is a very important factor so that it affects to SOC-S
Soil Organic C (g kg−1) Walkley and Black method (Nelson and Sommers,
1982)
estimation. In this line, IPCC (2003) and Stolbovoy et al. (2005,2007) in
SOC-S(Mg ha−1) SOCS = SOC concentration × BD × d × (1 – soil sampling protocol indicated that the gravel content should be
δ2mm%) × 10−1 (IPCC, 2003) considered in the SOC-S estimations.
T-SOC-S(Mg ha−1) TSOCS = Σ soil section 1….n SOCS soil section (IPCC, 2003) Due to lithology (medium-grained granite), the studied soils were
characterized by high sand content in all studied cases. This behavior
was like the gravel content (increasing in depth), except for Cof that
3. Results and discussion
decreased (Table 2). The minimum sand content was found in Cof (Bw-
horizon, 62.5%) and the highest value in Tv (C-horizon, 93.9%). With
3.1. Basic soil properties
respect to the clay content, it is important to note the low values found
in the studied soils, ranging from 7.2% (Ntgv: Bw) to 20.2% (Cof: Bw).
The studied soils were dystric and eutric Cambisols according to
For all land uses, bulk density (BD) increased in depth (Table 2). One
IUSS Working Group WRB (2015), exhibiting differences in their phy- crucial point which needs to be highlighted is the soil texture, so that, it
sical and chemical properties with respect to land use and depth
does not affect to the SOC-S quantification directly, however, it can
(Lagomarsino et al., 2011; Seddaiu et al., 2013; Francaviglia et al., affect to SOC-S indirectly, producing changes in BD, SOC content, and
2014). Overall, the soils were deep, with sandy texture (loamy sand,
other soil properties (e.g., liquid and gaseous components distribution
sand, sandy loam, and sandy clay loam), with high gravel content in within soil). Similar results were found by Parras-Alcántara et al.
some cases (Table 2). Similar outcomes were obtained by Álvarez et al.
(2014) in Los Pedroches Valley (Southern Spain) in Cambisols (land
(2007) and Lozano-García and Parras-Alcántara (2013) in Cambisols in use: Cof; lithology: granite), who using Pearson's correlation matrix
Sierra Morena (Southern Spain) for Cof and Cof with olive trees re-
identified significant linear correlations between: sand and silt content,
spectively, indicating that the physical soil properties in these soils are sand and clay content, SOC and BD, silt and clay content, BD and sand
affected by the lithology (granite), while their development is condi-
content, and thickness and BD… among others.
tioned by their formation age (Porta et al., 2003). The SOC analysis in top soil (A-horizon) showed the highest SOC
Soil depth was variable in the different land uses examined, with
concentration in Cof (59.2 and 13.5 g kg−1 in A1 and A2 horizons re-
maximum values in the range 101–130 cm for all land uses, except for
spectively, with a weighted average of 36.4 g kg−1) and the lowest
Cof where depth was limited by rock fragments at 60 cm depth
concentrations in Ntgv with 10.3 g kg−1 (Table 3). This low con-
(Table 2). The surface horizon thickness (A-horizon) was not sig-
centrations in Ntgv according to Francaviglia et al. (2014) is due to
nificantly different (p < 0.05) in Tv (18.3 cm), Ntgv (20.2 cm) and Cof
Ntgv only the pruning residues being left on the soil, without another
(A1 + A2 = 20 cm), however, significantly differences were founding
organic amendment. However, in Tv, an organic fertilization was ap-
in comparison with Fv (25.4 cm), P (26.6 cm) and Hc (28.1 cm). These
plied (12.5% organic nitrogen, 40% organic carbon and 70% organic
small variations can be justified by slope steepness, length, topographic
matter) at the end of January at the rate of 500 kg ha−1 being in-
curvature, and relative topographic position regarding to different soil
corporated in the first 20 cm of soil with a rototiller; it provides
positions in the study (Parras-Alcántara et al., 2013). Other authors
200 kg ha−1 of organic carbon and 62.5 kg ha−1 of N. Also, the pruning
such as Bakker et al. (2005) in Greece for different LUC justified these
residues are removed from the field. Regardless of land use, the SOC
soil thickness variations by management news associated to LUC with
concentrations decreased in depth. It is important to noted that the
heavy machinery.
studied soils under Cof had higher SOC concentrations than other
The gravel content was very heterogeneous, ranging on average
Cambisols with the same land use in other locations (Mediterranean
between 9.4% and 60.7% for Cof (Bw-horizon) and Ntgv (C-horizon)
areas). Thus, in Southern Spain, Corral-Fernández et al. (2013) found

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B. Lozano-García, et al. Ecological Indicators 119 (2020) 106831

Table 2
Physical soil properties evaluated (average ± SD*) in the entire soil profile by horizons in the study area.
Land Use Hor. Depth (cm) TH (cm) Gravel (%) Texture Sand (%) Silt (%) Clay (%) BD (Mg m−3)

Cof CM-dy n = 2 A1 0–3.5 3.50 ± 0.71c 14.5 ± 3.18c SL 73.6 ± 4.01b 13.4 ± 2.70b 12.9 ± 1.31a 1.14 ± 0.00c
A2 3.5–20.0 16.5 ± 6.36c 30.8 ± 8.27c SL 76.7 ± 25.5b 12.0 ± 2.54a 11.3 ± 0.01a 1.49 ± 0.01b
Bw 20.0–60.0 40.0 ± 10.2b 9.40 ± 2.42d SCL 62.5 ± 1.91c 17.3 ± 1.84a 20.2 ± 1.16a 1.60 ± 0.03a
Tv CM-dy n = 4 Ap 0–18.3 18.3 ± 2.63b 54.6 ± 6.75a LS 82.9 ± 3.75a 4.85 ± 4.65d 12.2 ± 1.53a 1.51 ± 0.07a
Bw 18.3–50.6 32.3 ± 13.8b 55.2 ± 10.7a LS 82.7 ± 3.78a 5.33 ± 3.35b 12.0 ± 0.83a 1.53 ± 0.04a
BC 50.6–103.6 53.0 ± 9.85a 55.0 ± 8.26a S 88.3 ± 2.27a 3.36 ± 2.58c 8.31 ± 0.85b 1.54 ± 0.04a
C 103.6–130.3 26.7 ± 5.77a 59.7 ± 14.1a S 93.9 ± 0.77a 1.25 ± 0.43a 4.84 ± 0.82a 1.51 ± 0.05a
Ntgv CM-dy n = 4 Ap 0–20.2 20.2 ± 4.92b 33.9 ± 5.20b LS 79.9 ± 0.91a 8.60 ± 1.30c 11.5 ± 1.18a 1.51 ± 0.06a
Bw 20.2–64.7 44.5 ± 10.5a 51.2 ± 13.6a LS 87.0 ± 5.62a 5.82 ± 2.74b 7.21 ± 3.06b 1.53 ± 0.03a
C 64.7–101.4 36.7 ± 15.3b 60.7 ± 15.6a S 87.7 ± 6.64a 3.92 ± 2.92c 8.42 ± 4.69b 1.58 ± 0.04a
Hc CM-dy n = 5 Ap 0–28.1 28.1 ± 13.9a 32.2 ± 5.45b SL 70.5 ± 9.31b 17.1 ± 10.0a 12.4 ± 13.7a 1.40 ± 0.09b
Bw 28.1–60.0 31.9 ± 19.6b 32.4 ± 11.2c SL 74.6 ± 2.62b 13.7 ± 1.50a 11.6 ± 1.38a 1.56 ± 0.03a
C 60.0–120.0 60.0 ± 42.4a 54.3 ± 14.9a LS 85.6 ± 28.6a 3.66 ± 2.68c 10.7 ± 0.18b 1.57 ± 0.01a
P CM-dy n = 4 A 0–26.6 26.6 ± 8.79a 26.9 ± 4.45b SL 73.1 ± 1.06b 13.5 ± 0.96b 13.4 ± 0.89a 1.45 ± 0.04b
Bw 26.6–64.3 37.7 ± 19.1b 36.2 ± 21.4c SL 79.0 ± 4.23a 10.3 ± 3.02a 10.7 ± 16.1a 1.56 ± 0.03a
BC 64.3–122.8 58.5 ± 33.2a 24.0 ± 2.93c SL 74.2 ± 2.11b 9.43 ± 5.88b 16.3 ± 5.67a 1.60 ± 0.01a
Fv CM-dy n = 7 A 0–25.4 25.4 ± 8.08a 33.9 ± 13.6b SL 78.9 ± 3.60a 10.7 ± 3.73c 10.4 ± 3.26a 1.44 ± 0.03b
Bw 25.4–55.7 30.3 ± 5.54b 41.5 ± 13.4b LS 82.6 ± 3.41a 7.36 ± 0.27b 10.0 ± 3.13a 1.48 ± 0.06b
C 55.7–105.5 49.8 ± 10.6a 42.1 ± 21.4b LS 84.0 ± 6.39a 5.92 ± 2.53b 10.0 ± 4.31b 1.60 ± 0.03a

SD*: Standard deviation; Hor.: Horizon; TH: Thickness; BD: Bulk density; Texture (USDA, 2004), LS: Loamy sand, S: Sand, SL: Sandy loam, SCL: Sandy clay loam.
Cof: Cork oak forest; Tv: Tilled vineyard; Ntgv: No tilled grassed vineyard; Hc: Hay crop; P: Pasture; Fv: Former vineyard.
CM-dy: Dystric Cambisols (IUSS Working Group WRB, 2015); n = Sample size.
Numbers followed by different lower-case letters are significantly different (p < 0.05) for the same horizon among different land uses considering the same
property.

11.4 g kg−1 (A-horizon: 20 cm) under Cof, Peregrina et al. (2014) found 3.2. Land use change 1: From agroforestry system to agricultural land.
SOC concentrations in the top 20 cm under vineyards ranging from 6.2 Effects on SOC-S (Decarbonization and Carbonization)
to 10.1 g kg−1, in Sardinia (Italy), Salis et al. (2015) reported SOC
concentrations of 21.1 g kg−1 in the topsoil (30 cm) under natural The starting point was the MEOW - Cof system in the year 1938. The
pastures, and 15.6 g kg−1 after a LUC to forage crop, Novara et al. SOC-S concentrations in Cof were 44.2 Mg ha−1 and 63.0 Mg ha−1
(2013) after vineyards abandonment in Sicily (Italy), found SOC con- respectively for topsoil (0–20 cm: A1 + A2 horizon) and for in the
centrations ranging from 14.7 to 26.3 g kg−1 as a function of aban- whole soil profile (0–60 cm) (Fig. 3, Table 3). These values are in agree
donment age with different vegetation covers in the top-soil (30 cm). with Chiti et al. (2012) in agroforestry systems in Italy, who found SOC-
This variability in the SOC concentration (A-horizon) could be due to S concentrations between 40 and 70 Mg ha−1 and with Rodríguez-
soil thickness, tree density, or even MEOW-Cof management (Corral- Murillo (2001) who determined 71.4 Mg ha−1 for Cambisols and
Fernández et al., 2013). 50.8 Mg ha−1 for Cof in Spain. The differences in the SOC-S between
agroforestry systems in Italy, soil groups in Peninsular Spain and the
studied soils may be caused by soil thickness, since we used entire soil
profiles (60 cm depth), Chiti et al. (2012) used top soil (30 cm) and

Table 3
Physical soil properties evaluated (average ± SD*) in the entire soil profile by horizons in the study area.
Land Use Hor. SOC (g kg−1) SOC-S (Mg ha−1) SOC-S SH/SSH (Mg ha−1) T-SOC-S (Mg ha−1)

Cof CM-dy n = 2 A1 59.2 ± 13.1 20.5 ± 7.78 44.2 ± 10.0a 63.0 ± 8.50a
A2 13.5 ± 0.48 23.7 ± 12.3 18.8 ± 5.42a
Bw 3.25 ± 1.81 18.8 ± 5.42
Tv CM-dy n = 4 Ap 14.4 ± 5.51 17.6 ± 6.82 17.6 ± 6.82b 59.8 ± 12.8a
Bw 10.1 ± 4.41 22.7 ± 26.3 42.2 ± 14.8b
BC 4.75 ± 4.58 17.4 ± 17.4
C 1.36 ± 0.45 2.11 ± 0.80
Ntgv CM-dy n = 4 Ap 10.3 ± 6.26 18.5 ± 9.90 18.5 ± 9.90b 40.5 ± 10.4b
Bw 5.59 ± 5.48 16.7 ± 14.6 21.9 ± 10.7a
C 2.90 ± 4.26 5.25 ± 6.82
Hc CM-dy n = 5 Ap 21.8 ± 8.65 54.6 ± 25.3 54.6 ± 25.3c 92.7 ± 13.7c
Bw 6.08 ± 2.56 17.5 ± 7.22 38.1 ± 7.99c
C 5.43 ± 0.01 20.6 ± 8.76
P CM-dy n = 4 A 18.3 ± 4.21 49.8 ± 16.0 49.8 ± 16.0c 95.3 ± 14.7c
Bw 6.18 ± 2.27 23.7 ± 19.3 45.5 ± 14.1b
BC 3.24 ± 0.74 21.8 ± 8.90
Fv CM-dy n = 7 A 17.3 ± 3.72 41.8 ± 14.6 41.8 ± 14.6a 83.4 ± 12.3d
Bw 13.2 ± 4.50 36.5 ± 22.2 41.6 ± 11.2b
C 1.11 ± 0.01 5.12 ± 0.14

Tv: Tilled vineyard; Ntgv: No tilled grassed vineyard; Hc: Hay crop; P: Pasture; Cof: Cork oak forest; Fv: Former vineyard
CM-dy: Dystric Cambisols (IUSS Working Group WRB, 2015)
SD*: Standard deviation. Hor: Horizon; TH: Thickness; BD: Bulk density; SOC: Soil organic carbon; LS: Loamy sand, S: Sand, SL: Sandy loam, SCL: Sandy clay loam.
Land uses as in Table 1.
Numbers followed by different lower case letters are significantly different (p < 0.05) for the same horizon among different land uses considering the same property.

5
B. Lozano-García, et al. Ecological Indicators 119 (2020) 106831

120
Cof

Tv 100
Land uses

T-SOC-S (Mg ha-1)

Ntgv
80
Hc

P 60

Fv
40
0 20 40 60 80 100
SOC-S (Mg ha-1) SH SSH 20
−1
Fig. 3. SOC-S (Mg ha ) (average ± SD). A comparison between the surface
and the subsurface horizons. SD: standard deviation. Land uses are Tv: Tilled 0
vineyard; Ntgv: No tilled grassed vineyard; Hc: Hay crop; P: Pasture; Cof: Cork Cof Tv Ntgv Hc P Fv
oak forest; Fv: Former vineyard. SH: superficial horizon. SSH: subsurface hor-
Land uses
izons.
Fig. 4. Total SOC-S (Mg ha−1) (average ± SD) in the different land uses. SD:
Rodríguez-Murillo (2001) used soil profiles descriptions deeper than standard deviation. Land uses are Tv: Tilled vineyard; Ntgv: No tilled grassed
vineyard; Hc: Hay crop; P: Pasture; Cof: Cork oak forest; Fv: Former vineyard.
1 m.
Cof is a unique ecosystem, and it is the most widespread agrofor-
estry system in Mediterranean Europe integrating forestry, agricultural difficult to achieve accurate comparisons (Table 2). Other researches
and livestock practices (Romanya et al., 2007). In general, the vegeta- have shown that the LUC from native forest to agricultural land reduces
tion cover and the SOC-S are lower than in others natural forests in the surface SOC concentration, mainly by reducing biomass inputs to
Europe. Nowadays, many researches have determined the Cof con- the soil and increasing soil erosion (Yu and Jia, 2014; Bruun et al.,
tribution to C sequestration and the preliminary results indicate a large 2015). These same effects have been reported after LUC from agrofor-
capacity of these areas for SOC accumulation - C sink (Roig and Rubio, estry systems (Cof) to perennial crops (olive groves) in Spain by Lozano-
2009) especially in Mediterranean areas. In addition, different tree García et al. (2016).
species store SOC in different ways and quantities (Jandl et al., 2007), However, for the soil recarbonization processes (Cof to Hc and P),
being the Quercus sp. one of the highest forest type in terms of SOC the LUC did not cause a negative impact on SOC-S (Table 3 and Figs. 3
storage (140, 111, 87 and 116 Mg ha−1 of SOC-S in Mediterranean and 4). Conversely, the SOC-S increased, in this sense, our results are in
pines, Mixed conifers, Standard Oak and Oak evergreen respectively) agree with several studies that showed increase or no change in SOC-S
(de Vries et al., 2003). after the LUC from forests to pastures or grasslands. Murty et al. (2002)
The first LUC was from Cof to Tv, Ntgv, Hc and P (first half of the found that the LUC from forest to pasture (as in the studied soils), did
20th century ≈ 1938). The principal consequence of this LUC was a soil not imply changes in the SOC-S concentrations, in fact, in more than
decarbonization (Tv and Ntgv) and a soil carbonization (Hc and Ap) half of the pastures SOC did not significantly increase. Fujisaki et al.
with respect to the original land use (Cof). In the decarbonization case (2015) also observed a slight increase on SOC-S concentrations in
(Cof to Tv and Ntgv) the SOC-S was reduced a 5.1% and 37.5% for Tv pastures compared to forests (+6.8%) after the LUC from forest. The
and Ntgv respectively, however in the carbonization case (Cof to Hc and main reason for explaining this SOC-S increases in pastures due to LUC
P) the SOC-S was increased a 47.1% and 51.3% for Hc and P with re- is that pastures is favored by the high root biomass and grasses activity
spect to Cof (Table 3). (Schnabel et al., 2001), which provides enough C to offset the miner-
In the case of soil decarbonization processes, two things happened; alization of native forest C (Fisher et al., 1994). In addition, this sig-
firstly, there was a strong SOC-S loss in the surface horizon (A-horizon) nificant increase in Hc and P (Cof: 63.0 Mg ha−1 to Hc: 92.7 Mg ha−1
in both cases (Tv and Ntgv) after the LUC. SOC-S losses were higher and P: 95.3 Mg ha−1) (Table 3), it could be caused by top soil accu-
than 60% (Cof: 44.2 Mg ha−1 to Tv: 17.6 Mg ha−1 and Ntgv: mulation of harvest residues and by the different climatic conditions
18.5 Mg ha−1); secondly, there was a SOC-S increase in depth espe- under the trees (temperature, the shade effect and the differences in the
cially important in Tv (124.5%) (Table 3), but despite these changes incidence of rainfalls) which produce more slow mineralization and
only were found significant differences (p < 0.05) between Cof more intense humification (Don et al., 2007).
(63.0 Mg ha−1) and Ntgv (40.5 Mg ha−1) with respect to total SOC-S An important issue to consider in both cases (decarbonization and
along to soil entire profile. The SOC-S values in both types of vineyards carbonization) is that in all cases there was a SOC-S increase in depth
were lower than the average values calculated in Italy and France. In due to the LUC (Cof: 18.8 Mg ha−1 to Tv: 42.2 Mg ha−1, Ntgv:
this line, Chiti et al. (2012) found 41.9 Mg ha−1 in the first 30 cm for 21.9 Mg ha−1, Hc: 38.1 Mg ha−1, and P: 45.5 Mg ha−1). And this SOC-S
vineyards in Italy, Arrouays et al. (2001) found, also in the first 30 cm, increase in depth could be due to the mixing of the soil layers during
values ranging between 15 and 39 Mg ha−1, depending on the soil type, soil tillage (Novara et al., 2012), by stabilization mechanisms of the
however, the SOC-S in soil entire profile (Fig. 2) was in line with those clays (Bw-horizon) (Leifeld et al., 2015) or by C translocation in the
obtained by Rodríguez-Murillo (2001) in Spanish vineyards considering form of dissolved organic C, soil fauna activity, and/or the effects of
1 m in depth. These differences in depth with respect to SOC-S could be deep-rooting crops (Shrestha et al., 2004). All this shows the soil po-
conditioned by the soil thickness (Cof: 40 cm, Tv: 112 cm and Ntgv: tential for C sequestration, so that the roots transfer large amounts of C
81.2 cm) (Table 2). Without forgetting that low SOC concentrations into the soil slowly and contribute to the increase of C content in depth,
could also be explained by the soils texture, so that, the aggregates which accumulates over time.
formation between soil OM and mineral fraction is reduced, favoring However, there is an inherent but not quantifiable source of varia-
high levels of transformed OM in sandy soils (González and Candás, tion in the data, due the different time periods after the conversion from
2004). Also, it must be taken into consideration that there were dif- Cof to P and Hc that were established in the 70 s, and Tv and Ntgv in the
ferences among soil profile in depth and the land uses, making it 90 s (Francaviglia et al., 2017b). After all, our results showed that all

6
B. Lozano-García, et al. Ecological Indicators 119 (2020) 106831

LUC’s from forest to agricultural land had not a negative impact in the 3.4. Soil recarbonization. 4 per mile initiative
soil capacity to storage SOC, except for Ntgv. Therefore, it is important
to study the different alternatives before transforming a natural area The soil can act as both C sink and source depending on manage-
into agricultural land. ment, biomass input levels, micro-climatic conditions, and bioclimatic
change (Zomer et al., 2017). Therefore, it is necessary to know the
uptake capacity of land-based sinks (soil, forest, and wetlands) (Lal,
3.3. Land use change 2: From agricultural land abandonment and naturally 2016). Precisely this was one of the targets of the “4p1000 initiative:
revegetated to seminatural systems. Effects on SOC-S (Recarbonization) Soils for Food Security and Climate” in the United Nations Framework
Convention for Climate Change: Conference of the Parties (UNFCCC-
The second LUC was from Tv and Ntgv to Fv (in the middle of the COP 21) in Paris. The objective of this proposal was to increase 0.6 tons
20th century ≈ 1966), due to the vineyard’s abandonment because of of C per ha yr−1 on average globally in the first 40 cm soil depth to
low yields and high agricultural costs. These areas were naturally re- compensate the annual CO2-C emissions from fossil fuels.
converted through secondary succession into an ecosystem very similar In the studied area, different processes have occurred (dec-
to Cof. This second LUC caused a SOC-S increase (recarbonization) in arbonization, carbonization and recarbonization) due to LUC. Let us
comparison with the previous state in vineyards (Tv and Ntgv to Fv), focus on the second LUC (from agricultural land abandonment and
increasing the total SOC-S a 39.5% and 106% from Tv to Fv and from naturally revegetated to seminatural systems – Tv and Ntgv to Fv). This
Ntgv to Fv, respectively. Increasing even the total SOC-S with the ori- LUC started in 1966 and ended in 2007, therefore this LUC has lasted
ginal situation (Cof) a 32.4% (Cof: 63 Mg ha−1; Tv: 59.8 Mg ha−1; 41 years. Many uncertainties arise when interpreting these data to
Ntgv: 40.5 Mg ha−1 and Tv: 83.4 Mg ha−1). Therefore, it is important check the 4‰ strategy, uncertainties such as the soil thickness to
to emphasize that not only a soil carbonization process was produced consider or the number of years to study…among others. In this sense,
(from Tv and Ntgv to Fv), but also a recarbonization process took place, other authors such Chabbi et al. (2017) or Poulton et al. (2017) also
so that the SOC-S increased with respect to the initial situation (Cof) raise these questions.
(Table 3), assuming that soil recarbonization (SOC sequestration) im- The LUC studied (Tv and Ntgv to Fv) in entire soil profiles
plying an additional net transfer of C from the atmosphere to the soil (Tv:130.3 cm; Ntgv: 101.4 cm; Fv: 105.5 cm) for 41 years resulted on
via biomass (Lorenz et al., 2011). average a SOC-S increase of 33.25 Mg ha−1 (Tv: 59.8 Mg ha−1; Ntgv:
In topsoil, this LUC (Tv and Ntgv to Fv) caused a SOC-S increase (Tv: 40.5 Mg ha−1; Tv/Ntgv average: 50.2 Mg ha−1; Fv: 83.4 Mg ha−1)
17.6 Mg ha−1; Ntgv: 18.5 Mg ha−1; Fv: 41.8 Mg ha−1), however, in (Tables 2 and 3), therefore, the average increase has been of 0.81 tons
depth these changes were lower (Tv: 42.2 Mg ha−1; Ntgv: per ha yr−1 which would be a 5.4‰, slightly better results than those
21.9 Mg ha−1; Fv: 41.6 Mg ha−1) (Table 3). In this line, it is known that set out in the 4‰ initiative.
after a disturbance, the SOC-S accumulation following a favorable LUC If the thickness is reduced and only the first and the second soil
is more rapid at the beginning, and it stops when a new equilibrium is horizons is consider so that this depth is more similar to 40 cm that 4‰
reached (Muñoz-Rojas et al., 2015), and that the period required to initiative proposes (Tv: 50.6 cm; Ntgv: 64.7 cm: Fv: 55.7 cm), the in-
reach this new equilibrium depends on the climatic conditions and crease was 40.6 Mg ha−1 (Tv: 40.3 Mg ha−1; Ntgv: 35 Mg ha−1; Tv/
vegetation type…, among others. In temperate areas of Europe a few Ntgv average: 37.7 Mg ha−1; Fv: 78.3 Mg ha−1) therefore, the average
decades are necessary to achieve this balance (Arrouays et al., 2001), increase has been 0.99 tons per ha yr−1 (6.6‰). But if we limit it to the
while hundred years are needed in other locations, e.g. boreal regions top soil (A-horizon) (Tv: 20.0 cm; Ntgv: 18.3 cm; Fv: 25.4 cm), the
(Smith, 2004). In our case, the LUC after the land abandonment was increase was 23.7 Mg ha−1 (Tv: 17.6 Mg ha−1; Ntgv: 18.5 Mg ha−1;
41 years (1966–2007). Post and Kwon (2000) identified different fac- Tv/Ntgv average: 18.1 Mg ha−1; Fv: 41.8 Mg ha−1), the average in-
tors that determine the SOC-S increases: i) increase in the OM inputs, ii) crease has been 0.58 tons per ha yr−1 (3.9‰). Chabbi et al. (2017)
changes in the soil OM decomposition which increase the organic C pointed out that the SOC storage implementation under the 4‰ in-
light fraction, iii) deeper OM location either directly by increasing itiative is feasible assuming total soil (0–1 m) for removal 6 Gt C yr−1
below-ground inputs, or indirectly by improving surface mixing by soil from the atmosphere (2/3 of the annual anthropogenic CO2 emissions)
organisms and iv) increase in the physical protection by intra-ag- by applying economically viable agronomic practices and good en-
gregates and/or organo-mineral complexes. vironmental practices. This is in line with our results, since if we assume
Our findings are in agree with the results obtained by different an average thickness of 112.4 cm the LUC (Tv and Ntgv to Fv) causes an
authors at worldwide who find an opportunity for C sequestration after SOC-S increase in accordance with 4‰ initiative (112.4 cm average
the LUC from marginal arable land to permanent and perennial vege- thickness, 0.81 tons per ha yr−1, 5.4‰). However, our best results are
tation (Paustian et al., 1997; Post and Kwon, 2000; Guo and Gifford, obtained by Tv: 50.6 cm, Ntgv: 64.7 cm and Fv: 55.7 cm, with an
2002; Muñoz-Rojas et al., 2015). Paustian et al. (1997) stated that in average increase of 0.99 tons per ha yr−1 (6.6‰), due to Bw-Horizon
North America and Europe, the LUC from marginal arable land to with a SOC-S increase (Novara et al., 2012; Leifeld et al., 2015; Shrestha
permanent perennial vegetation allows the fragile soils protection, the et al., 2004; Parras-Alcántara et al., 2013).
agricultural surpluses reduction, and provides an environmental benefit
via SOC sequestration. In addition, in different meta-analyses, Post and 3.5. The need to increase the SOC stocks as European policy.
Kwon (2000) and Guo and Gifford (2002) found SOC-S increases at
different rates, when cropland is converted to forest. More recently, The SOC reduction is one of the eight soil threats identified in the
Muñoz-Rojas et al. (2015) studying the LUC impact on SOC-S in the European Union (EU) Thematic Strategy for Soil Protection (EC, 2006
south of Spain between 1956 and 2007 found changes from arable land and 2012), and therefore one of the most important aims is to maintain
to forest leading a SOC-S increase, and these results occurred in dif- and improve the SOC-S throughout the EU countries. In this line, it is
ferent soil types and this changes were more marked in the surface layer important to highlight that SOC-S in the agricultural soils within the EU
(top soil). is 17.63 Gt, therefore, the EU agricultural policy should use the SOC as
All of this indicates that the removal of natural vegetation (Cof) to the main soil quality indicator and as a strategy for offsetting CO2
plant vineyards (Tv and Ntgv) was the cause of SOC-S decreasing and emissions by C sequestration in the soil (ESDAC, 2018).
that the vineyard abandonment and subsequently natural restoration The Roadmap to a Resource Efficient Europe (EC, 2011), established
provoked an increased in SOC-S values. the goal of enhancing current SOC levels in the EU by 2020 (Lugato
et al., 2014). In addition, under Common Agricultural Policy (CAP),
farmers are called up to maintain the agro-ecosystem by rural

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B. Lozano-García, et al. Ecological Indicators 119 (2020) 106831

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Climate change and agro-forestry systems: impacts on soil carbon sink 1994. Carbon storage by introduced deep-rooted grasses in the South American sa-
and microbial diversity, funded by the Integrated Special Fund for vannas. Nature 371, 236–238.
Francaviglia, R., Benedetti, A., Doro, L., Madrau, S., Ledda, L., 2014. Influence of land use
Research (FISR) of the Italian Ministry of University and Research (D.D.
on soil quality and stratification ratios under agro-silvo-pastoral Mediterranean
286, February 20, 2006). We greatly appreciate the soil profile de- management systems. Agric. Ecosyst. Environ. 183, 86–92.
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