Search

Globally, annual emissions from managed organic soils accounts for up to 5% of all anthropogenic greenhouse gas (GHG) emissions. Climate-wise management and restoration of degraded organic soils could reduce GHG emissions quickly and at relatively low costs. The European Union (EU) Member States that have large areas of organic soils with high GHG emissions are Sweden, Finland, Germany, Ireland, Poland, Netherlands, and the Baltic countries. To meet the climate targets and objectives of the Paris Agreement the land-use sector is indispensable and mitigation policies targeting organic soils will be needed. The international regulatory framework is broad and quite unspecific. In contrast, the European Union has initiated binding regulation for the land-use sector through the EU Climate Law, the EU LULUCF regulation, and the proposed EU Nature Restoration Law. However, even this regulatory approach is not on track to deliver on its binding ambitions, indicating the need for more effective implementation measures also on organic soils in the EU and its member states. Furthermore, we argue that appropriate policy selection should consider current knowledge regarding the climate impacts of management options of organic soils. Lastly, we need more studies on GHG emissions, and standardized methods for GHG inventories, to resolve uncertainties surrounding the impacts of management to GHG emissions. Successful policy implementation requires more efforts but also improved scientific justification through continuous consideration of climate policy integrity and strengthening of the reliability of GHG inventories. [ABSTRACT FROM AUTHOR]

Purpose: Anthropogenic activities are a major driver of soil and land degradation. Due to the spatial heterogeneity of soil properties and the global nature of most value chains, the modelling of the impacts of land use on soil quality for application in life cycle assessment (LCA) requires a regionalised assessment with global coverage. This paper proposes an approach to quantify the impacts of land use on soil quality, using changes in soil organic carbon (SOC) stocks as a proxy, following the latest recommendation of the Life Cycle Initiative. Methods: An operational set of SOC-based characterisation factors for land occupation and land transformation were derived using spatial datasets (1 km resolution) and aggregated at the national and global levels. The developed characterisation factors were tested by means of a case study analysis, investigating the impact on soil quality caused by land use activities necessary to provide three alternative energy supply systems for passenger car transport (biomethane, ethanol, and solar electricity). Results obtained by applying characterisation factors at local, regional, and national levels were compared, to investigate the role of the level of regionalisation on the resulting impacts. Results and discussion: Global maps of characterisation factors are presented for the 56 land use types commonly used in LCA databases, together with national and global values. Urban and industrial land uses present the highest impacts on SOC stocks, followed by severely degraded pastures and intensively managed arable lands. Instead, values obtained for extensive pastures, flooded crops, and urban green areas often report an increase in SOC stocks. Results show that the ranking of impacts of the three energy systems considered in the case study analysis is not affected by the level of regionalisation of the analysis. In the case of biomethane energy supply, impacts assessed using national characterisation factors are more than double those obtained with local characterisation factors, with less significant differences in the other two cases. Conclusions: The integration of soil quality aspects in life cycle impact assessment methods is a crucial challenge due to the key role of soil conservation in ensuring food security and environmental protection. This approach allows the quantification of land use impacts on SOC stocks, taken as a proxy of soil quality. Further research needs to improve the assessment of land use impacts in LCA are identified, such as the ability to reflect the effects of agricultural and forestry management practices. [ABSTRACT FROM AUTHOR]

Grazing lands can be considered a conservation land use providing value to farmers and society. An underappreciated value of these lands may be in C and N storage and cycling. However, soil organic C (SOC) and total soil N (TSN) storage under humid‐temperate zone pastures have not been well characterized. A survey of 31 farms in Virginia USA characterized SOC and TSN depth distributions under a diversity of grassland management scenarios, as well as in comparison with long‐term no‐till cropland and woodland uses on the same farms. Root‐zone enrichment calculations separated management‐controlled SOC and TSN stocks from a baseline condition characterized at 30‐cm depth. Total stock of SOC at 0–30‐cm depth varied from 46 to 88 Mg C ha−1 (5%–95% range from 304 soil profiles) across all land uses. Root‐zone enrichment of SOC was maximized under mature pastures (≥20 years old) at 38.3 ± 1.6 Mg C ha−1, which was not different from that under woodland (39.8 ± 1.2 Mg C ha−1), but was greater than under no‐till cropland (28.3 ± 1.3 Mg C ha−1) and conventional‐till cropland (15.1 ± 5.1 Mg C ha−1). Root‐zone enrichment of TSN was optimized at stocking rate of ~1 Mg live weight ha−1, but was not affected by stocking method, N fertilization history, or low levels of hay feeding. These results suggest that grazed pastures in Virginia are storing significant amounts of SOC and TSN, with at least half due to management‐induced compared with pedogenic‐controlled accumulation. [ABSTRACT FROM AUTHOR]

Soil organic carbon (SOC) is the main component of carbon in terrestrial ecosystems and an indicator of soil quality. The study aimed to investigate the stock and vertical distribution of SOC fractions and the SOC sequestration of different agroforestry systems (AFS) and other land uses in the Colombian Amazon. In each land use (Secondary forest—SF, Natural regeneration—NR, Alley cropping 1—AC1, Alley cropping 2—AC2, Forest plantations 1—FP1, Forest plantations 2—FP2, Crops in forest plantation—CFP, Shade trees for crops—STC, Homegarden—HG, Silvopastoral system—SPS and Pasture—P), four soil pits were made (1 × 1 × 1 m) to collect soil samples to determine SOC concentration by carbon lability fractions (CVL: very labile, CL: labile, CLL: less labile, CNL: non-labile) and bulk density at four depths (0—10, 10–20, 20–40 and 40–100 cm). The mean SOC concentration was 15.3 ± 1.2 g kg−1, with a higher concentration in 0–10 cm (26.1 ± 2.4 g kg−1). The concentration of the different fractions presented the following order CVL > CNL > CL > CLL (7.4 ± 0.3, 4.8 ± 0.2, 2.7 ± 0.1 and 2.1 ± 0.1 g kg−1, respectively). SOC stock was 13.3 to 220.0 Mg C ha−1 in the 0–100 cm layers, where FP1, FP2, AC1 and AC2 showed the highest values (174.0 to 199.0 Mg ha−1). In contrast, HG, P and STC showed the lowest values with 134.0, 116.0 and 96.2 Mg ha−1, respectively. Therefore, and due to the contribution of the most stable carbon fractions in the soil (CLL and CNL), land uses such as AC1 and AC2 presented the highest levels of carbon stability measured by the carbon management index. Therefore, the different land uses with agroforestry systems increased the amount and stability of carbon accumulated in the soil compared to pasture. [ABSTRACT FROM AUTHOR]

The land use effect on soil chemical attributes and the soil organic carbon (SOC) sequestration in soil aggregates of tropical forest patches from the Brazilian semiarid have been neglected. This study aimed to investigate the effects of land use on the soil fertility and dynamics of aggregates and associated cementing agents (SOC and iron oxides). Bulk soil samples under three land uses (forest, agroforestry system, and pasture) in different layers (0.0–0.2 and 0.2–0.4 m) were collected in humid highlands from Northeastern Brazil, named 'Brejos de Altitude'. Soil acidity, exchangeable cations, availability P, and SOC were determined. The stability and size distribution of soil aggregates was measured as mean weight diameter (MWD). The samples were separated into six aggregate size fractions (< 2, 2–1, 1–0.5, 0.5–0.25, 0.25–0.106, and 0.106–0.053 mm) and evaluated for SOC and iron oxides (Fed). Our study indicated that agroforestry practices had an important effect on soil fertility, significantly increasing the content and cycling of Ca and P in the soils. The land use explained 75% variation of soil aggregates, in which SOC and Fed interactions contributed 55%. Conversion from forest to pasture significantly (p < 0.05) decreased the SOC in each aggregate size, while the agroforestry did not change. The agroforestry increased the potential of soils as SOC sink in microaggregates, suggesting higher storage and stabilization of SOC in the long term. SOC and Fed had significant effects (p < 0.05) on the stability of macroaggregates and microaggregates of soils under agroforestry, respectively. Agroforestry systems represent a sustainable practice for soil fertility improvement and SOC sink in the highlands of Brazilian Northeast. [ABSTRACT FROM AUTHOR]

Soil erosion is one of the major environmental concerns, causing a reduction in soil carbon stock and soil fertility. It is generally difficult to estimate soil erosion in hilly terrains. To overcome this, different types of erodibility indices are developed and used to describe the intensity of soil erosion. The present study was conducted in Nagaland state of northeast India, where clay ratio (CR), modified clay ratio (MCR), critical level of organic matter (CLOM) and erodibility factor (K) were used to assess the severity of soil erosion under different land uses. To study these, soil samples from forest, jhum, fallow jhum and tea gardens were collected from 0 to 30 cm soil depth. The results showed that sand and clay content were significantly different under different land uses, while soil organic carbon (SOC) and stocks followed the same trend, with maximum and minimum values under tea (60.55 t C ha–1 ) and jhum lands (40.74 t C ha–1 ) respectively. Among the different erodibility indices, only CR and MCR values were found to be significantly different from each other. Higher values of CR and MCR under jhum and fallow jhum lands indicate that these land uses are more prone to erosion. The present study provides a picture of severity of soil erosion under different land uses in Nagaland and recommends that CR and MCR can be used to evaluate soil erosion in hilly terrain areas. [ABSTRACT FROM AUTHOR]

Organic carbon performs essential functions in soils, which act as sources or sinks of atmospheric organic carbon. Agricultural management affects the carbon cycle in the soil, with effects on climate change. One of the crops most vulnerable to climate change is coffee. Brazil is the world’s largest coffee producer, with a predominance of management under a conventional system, with sloping terrain and the absence of conservationist practices. The absence of conservationist practices increases in soil loss rates due to water management and carbon emissions, as well as a reduction in coffee production. This paper intended to estimate soil and organic carbon losses by RUSLE in coffee farms in southern Minas Gerais, south-eastern Brazil. Data were obtained from fieldwork, laboratory analysis, and cartographic products. The results indicated, exclusively for coffee crops, soil and carbon losses between 7 and 32 Mg ha−1 year−1 and 87 and 460kg ha−1 year−1, respectively. However, the highest soil losses occurred on sloping terrains with eucalyptus plantations located downhill, and the lowest losses occurred on flat land with native forests. Organic carbon losses were linked directly to soil losses, as a result from the land practices, slope and agricultural management adopted. These results can be used for the planning and priority definition of areas needing conservationist practices, such as green manuring, planting in contour and maintaining of vegetation between coffee rows, which are already used in some sites of the study area. [ABSTRACT FROM AUTHOR]

Climate and land use changes are causing trees line to shift up into mountain meadows. The effect of this vegetation change on the partitioning of soil carbon (C) between the labile particulate organic matter (POM–C) and stable mineral-associated organic matter (MAOM–C) pools is poorly understood. Therefore, we assessed these C pools in a 10 cm topsoil layer along forest–meadow ecotones with different land uses (reserve and pasture) in the Northwest Caucasus of Russia using the size fractionation technique (POM 0.053–2.00 mm, MAOM < 0.053 mm). Potential drivers included the amount of C input from aboveground grass biomass (AGB) and forest litter (litter quantity) and their C/N ratios, aromatic compound content (litter quality), and soil texture. For both land uses, the POM–C pool showed no clear patterns of change along forest–meadow ecotones, while the MAOM–C pool increased steadily from meadow to forest. Regardless of land use, the POM–C/MAOM–C ratio decreased threefold from meadow to forest in line with decreasing grass AGB (R2 = 0.75 and 0.29 for reserve and pasture) and increasing clay content (R2 = 0.63 and 0.36 for reserve and pasture). In pastures, an additional negative relationship was found with respect to plant litter aromaticity (R2 = 0.48). Therefore, shifting the mountain tree line in temperate climates could have a positive effect on conserving soil C stocks by increasing the proportion of stable C pools. [ABSTRACT FROM AUTHOR]

Land use change (LUC) alters the global carbon (C) stock, but our estimation of the alteration remains uncertain and is a major impediment to predicting the global C cycle. The uncertainty is partly due to the limited number and geographical bias of observations, and limited exploration of its predictors. Here we generated a comprehensive global database of 5,980 observations from 790 articles. The number of sites evaluated is at least seven times larger than in previous meta‐analyses. Our constrained estimates of different LUC's effects on soil organic C (SOC) and their variations across global climates reveal underestimation/overestimation in previous estimates. Converting forests and grasslands to croplands reduced SOC by 24.5% ± 1.53% (−11.03 ± 1.06 Mg ha−1) and 22.7% ± 1.22% (−8.09 ± 0.67 Mg ha−1), while 28.0% ± 1.56% (4.46 ± 0.42 Mg ha−1) and 33.5% ± 1.68% (5.8 ± 0.38 Mg ha−1) increases, respectively, were obtained in the reverse processes. Converting forests to grasslands decreased SOC by 2.1% ± 1.22% (−1.13 ± 0.44 Mg ha−1), while the reverse process increased SOC by 18.6% ± 1.73% (3.31 ± 0.51 Mg ha−1). Modeled relative importance of 10 drivers of LUC's impact on SOC revealed that higher initial SOC (iSOC) does not solely determine SOC loss in SOC‐negative LUC scenarios as previously proposed. Across four decades, reconverting croplands to forests and grasslands recovered only 49.5% (6.1 ± 0.51 Mg ha−1) and 75.3% (7.0 ± 0.38 Mg ha−1) of the iSOC, respectively, indicating the need for protecting C‐rich ecosystems. Our global data set advances information on LUC's effect on SOC and can be valuable to constrain Earth system models to reliably estimate global SOC stocks and plan climate change mitigation strategies. Plain Language Summary: Land use change (LUC) could increase or decrease the global soil organic carbon (SOC) stock and affect carbon cycling and climate change, but estimating its effect size is the most uncertain aspect of the global carbon cycle. Available estimates vary among studies, most of which often use few observations that do not cover most global regions. To provide more accurate estimates of different LUC types' effects on SOC, we compiled a comprehensive database that contains 5,980 observations across all global regions; and revealed that previous studies have underestimated/overestimated these effects. We modeled the predictors of SOC change and found that previous conclusions that higher initial SOC is the main reason for higher organic carbon loss under negative LUC scenarios were inexact. We show that land use practices aimed at restoring SOC could only recover part of the amount lost during similar time frames; hence, it is important to protect carbon‐rich ecosystems. Our study provides robust estimates of LUC's effect on SOC and provides data sets that can reliably assess and model the global carbon cycle and plan strategies for controlling global climate change. Key Points: Comprehensive global database advances robust estimates of land use change's (LUCs) effect on soil organic carbon (SOC) vital for Earth system modelingHigher initial SOC does not solely control rapid SOC loss in carbon‐negative LUC as often proposedDespite SOC buildup in the past four decades, the amount lost cannot be regained by restoration during similar time frames [ABSTRACT FROM AUTHOR]

Antioxidants (AOX) in soils originate mainly from secondary plant metabolites and are pivotal in many redox processes in environment, maintaining soil quality. Still, little is known about the influence of land uses on their accumulation in soil. The aim of the paper was to determine the content of these redox-active compounds in the extracts of A horizons of abandoned fallows, arable and woodland soils. Total antioxidant capacity (TAC) of soils under various uses and vegetation was evaluated in different soil extracts using Folin-Ciocâlteu method. The contribution of humic acids to TAC was determined and antioxidant profiles estimated using the chromatographic GC–MS method. Forest soils exhibited the highest TAC (15.5 mg g−1) and AOX contents (4.34 mg g−1), which were positively correlated with soil organic carbon content. It was estimated that humic acids contribute to over 50% of TAC in soils. The main phenolics in woodland A horizons were isovanillic and p-hydroxybenzoic acid (p-HA), while esculetin and p-HA predominated in the abandoned fallows due to the prevalence of herbaceous vegetation. Cultivated soils were the most abundant in p-HA (56.42%). In the studied topsoils, there were considerable amounts of aliphatic organic matter, which role in redox processes should be further evaluated. [ABSTRACT FROM AUTHOR]

Soil organic carbon stock (SOCS) changes caused by land use changes are still unclear, and understanding this response is essential for many environmental policies and land management practices. In this study, we investigated the temporal–spatial and vertical distribution characteristics of the SOCS in the Western Sichuan Plateau (WSP) using the sparrow search algorithm–random forest regression (SSA-RFR) models with excellent model applicability and accuracy. The temporal–spatial variations in the SOCS were modeled using 1080 soil samples and a set of nine environmental covariates. We analyzed the effect of land use changes on the SOCS in the WSP. The total SOCS increased by 18.03 Tg C from 1990 to 2020. The results of this study confirmed a significant increase in the SOCS in the study area since 2010. There was a 27.88 Tg C increase in the SOCS in 2020 compared to the total SOCS in 2010. We found that the spatial distribution of the SOCS increased from southeast to northwest, and the vertical distribution of the SOCS in the study area decreased with increasing soil depth. Forests and grasslands are the main sources of SOCS the total SOCS in the forest and grassland accounted for 37.53 and 59.39% of the total soil organic carbon (SOC) pool in 2020, respectively. The expansion of the wetlands, forest, and grassland areas could increase the SOCS in the study area. A timely and accurate understanding of the dynamics of SOC is crucial for developing effective land management strategies to enhance carbon sequestration and mitigate land degradation. [ABSTRACT FROM AUTHOR]

Soil organic matter (SOM) fractions and functional groups can be used to study the short-term as well as the long-term effects of land use change on soil organic carbon (SOC) dynamics. In this study, soil samples of grassland (native vegetation), planted forest and cropland (both converted from grassland) were collected from three soil pedogenetic horizons of A-horizon, AB-horizon and Bk-horizon in a semiarid area of Northeast China. The amounts of SOC, particulate organic carbon (POC), and mineral-associated organic carbon (MOC) were evaluated. After grassland conversion into planted forest and cropland, the amount of SOC decreased by 5.71 and 13.59%, POC decreased by 17.39 and 34.72%, and MOC decreased by 2.84 and 8.36%. Based on the analysis of MOC composition, the average content of humic extract-C decreased by 2.19% and humin-C decreased by 3.08% for planted forest, meanwhile humic extract-C decreased by 14.14% and humin-C decreased by 6.24% for cropland, compared to grassland. This result suggested that labile SOC fractions were more affected by land use change. Solid-state 13C nuclear magnetic resonance (NMR) spectra of bulk soil showed that native grassland SOC had a higher proportion of alkoxy C but a lower proportion of aromatic C, and the aromaticity was less than that of planted forest and cropland. Our results suggested that although the chemical structure of SOM tend to be stable, SOM fraction levels were not enough to recover. Reasonable grassland management measures should be formulated to prevent the continued conversion of native grassland. [ABSTRACT FROM AUTHOR]

Land-use change (LUC) impacts biospheric carbon, encompassing biomass carbon and soil organic carbon (SOC). Despite the use of dynamic global vegetation models (DGVMs) in estimating the anthropogenic perturbation of biospheric carbon stocks, critical evaluations of model performance concerning LUC impacts are scarce. Here, we present a systematic evaluation of the performance of the DGVM ORCHIDEE to reproduce observed LUC impacts on biospheric carbon stocks over Europe. First, we compare model predictions with observation-based gridded estimates of net and gross primary productivity (NPP and GPP), biomass growth patterns, and SOC stocks. Second, we evaluate the predicted response of carbon stocks to LUC based on data from forest inventories, paired plots, chronosequences and repeated sampling designs. Third, we use interpretable machine learning to identify factors contributing to discrepancies between simulations and observations, including drivers and processes not resolved in ORCHIDEE (e.g. erosion, soil fertility). Results indicate agreement between the model and observed spatial patterns and temporal trends, such as the increase in biomass with age, when simulating biosphere carbon stocks. The direction of the SOC responses to LUC generally aligns between simulated and observed data. However, the model underestimates carbon gains for cropland-to-grassland and carbon losses for grassland-to-cropland and forest-to-cropland conversions. These discrepancies are attributed to bias arising from soil erosion rate, which is not fully captured in ORCHIDEE. Our study provides an oriented benchmark for assessing the DGVMs against observations and explores its potential in studying the impact of LUCs on SOC stocks. [ABSTRACT FROM AUTHOR]

Typical successions in land use affect the dynamics of carbon (C) and nitrogen (N) in the soil. This study aimed to determine the effects of land use change on soil organic carbon and N content and stocks in pastures, crops, and forests in the Amazon. Soil C and N stocks were assessed at depths of 30 and 100 cm to determine 13C isotopic abundance. The concentrations of C and N in crops were lower (p < 0.05) than those in other land use types. Soil organic C and soil N stocks for pasture (67.6, 144.8, 5.7, and 13.3) and forest (77.1, 137.5, 6.3, and 13.8) systems were similar, but greater than those of the crop area (36.4, 63.9, 3.0, and 6.0), regardless of depth (30 and 100 cm for C and N). Land use change for pastures in the Arc of Deforestation region of the Amazon maintains SOC and N stocks in the soil and is more sustainable than the agricultural system with black pepper, as long as the conditions of soil, climate, and cultivation are similar. Part of the C3-derived carbon from the forest was replaced by C4-derived C from grasses at soil depths up to 100 cm. [ABSTRACT FROM AUTHOR]

In this study biology-eco microplate culture technology was used to study the differences in carbon source utilization of soil microorganisms in land use patterns along the Yellow River in China. At the same time, physical and chemical indices of soil such as soil organic carbon and alkali-hydrolyzable nitrogen contents, three soil enzyme activities and two secondary metabolites contents were measured to explore the relationship between soil microbial carbon source utilization and soil characteristics. The results showed that farmland was the best carbon source utilization land use pattern, followed by poplar forest land, Ligustrum lucidum land and grassland. The consumption of carbon sources by the soil microorganisms in the four land use patterns were mainly carbohydrates and amino acids. The farmland showed the highest diversity of microorganisms. Furthermore, redundancy analysis (RDA) analysis showed that the metabolic functions and activities of four land use patterns microbial were mostly affected by the contents of organic carbon, alkali-hydrolyzed nitrogen and sucrase activity. Significant differences were observed among the physicochemical properties and microbial carbon source utilization of the four land use patterns along the Yellow River. Organic carbon, phosphatase and sucrase activities were the main factors affecting microbial diversity. This study provided a theoretical basis for future research on planning land use and helping soil ecological restoration along the Yellow River. [ABSTRACT FROM AUTHOR]

Monitoring soil organic carbon (SOC) typically assumes conducting a labor-intensive soil sampling campaign, followed by laboratory testing, which is both expensive and impractical for generating useful, spatially continuous data products. The present study leverages the power of machine learning (ML) and, in particular, deep neural networks (DNNs) for segmentation, as well as satellite imagery, to estimate the SOC remotely. We propose a new two-stage pipeline for remote SOC estimation, which relies on using a DNN trained to classify land cover to perform feature extraction, while the SOC estimation is performed by a different ML model. The first stage is an image segmentation DNN with the U-Net architecture, which is trained to estimate the land cover for an observed geographical region, based on multi-spectral images taken by the Sentinel-2 satellite constellation. This estimator is subsequently used to extract the latent feature vector for each of the output pixels, by rolling back from the output (dense) layer of the U-Net and accessing the last available convolutional layer of the same dimension as our desired output. The second stage is trained on a set of feature vectors extracted at the coordinates for which manual SOC measurements exist. We tested a variety of ML models and report on their performance. Using the best extremely randomized trees model, we generated a spatially continuous map of SOC estimations for the region of Tuscany, in Italy, with a resolution of 10 m, to share with the researchers as a means of validating the results and to demonstrate the efficiency of the proposed approach, which can can easily be scaled to create a global continuous SOC map. [ABSTRACT FROM AUTHOR]

More than 75% of the global land has already suffered degradation, leading to the recognition of land degradation as one of the foremost challenges society faces. This recognition stems from its profound adverse impacts on natural ecosystem functioning, biodiversity, soil productivity, and food availability. Consequently, understanding the spatial distribution of land degradation across all scales becomes imperative. This study employed land cover change and soil organic carbon (SOC) stock assessments to analyse land degradation within the eThekwini Municipality beyond the baseline period (2000–2015). Utilizing remote sensing and machine learning techniques, this research examined land degradation within the eThekwini Municipality over the period spanning 2000 to 2022. Landsat 7 (Enhanced Thematic Mapper Plus – ETM+), Landsat 8 (Operational Land Imager 1 - OLI1), and Landsat 9 (Operational Land Imager 2 - OLI2) images were employed to extract variables for both land cover change and SOC stock prediction through XGBoost, LightGBM, Random Forest (RF), and Support Vector Machine (SVM) models. Among these models, LightGBM demonstrates superior performance, achieving an overall accuracy of 80.646 in land cover predictions and 77.869 in SOC stock predictions. Analysis of land cover change within the eThekwini Municipality unveiled a shift from forests and shrubland landscapes to cropland and built-up areas. This shift results in the municipality encountering losses in SOC stock between 2015 and 2022. The model predicted that most SOC stock losses occur at the 20–50 cm depth (9.27%), in comparison to the 7.21% loss at the 0–20 cm depth. These findings underscore the pivotal role of remote sensing and machine learning in aiding policymakers to assess land degradation and implement pertinent measures to enhance the landscape. [ABSTRACT FROM AUTHOR]

Background: In most regions and ecosystems, soils are the largest terrestrial carbon pool. Their potential vulnerability to climate and land use change, management, and other drivers, along with soils' ability to mitigate climate change through carbon sequestration, makes them important to carbon balance and management. To date, most studies of soil carbon management have been based at either large or site-specific scales, resulting in either broad generalizations or narrow conclusions, respectively. Advancing the science and practice of soil carbon management requires scientific progress at intermediate scales. Here, we conducted the fifth in a series of ecoregional assessments of the effects of land use change and forest management on soil carbon stocks, this time addressing the Northeast U.S. We used synthesis approaches including (1) meta-analysis of published literature, (2) soil survey and (3) national forest inventory databases to examine overall effects and underlying drivers of deforestation, reforestation, and forest harvesting on soil carbon stocks. The three complementary data sources allowed us to quantify direction, magnitude, and uncertainty in trends. Results: Our meta-analysis findings revealed regionally consistent declines in soil carbon stocks due to deforestation, whether for agriculture or urban development. Conversely, reforestation led to significant increases in soil C stocks, with variation based on specific geographic factors. Forest harvesting showed no significant effect on soil carbon stocks, regardless of place-based or practice-specific factors. Observational soil survey and national forest inventory data generally supported meta-analytic harvest trends, and provided broader context by revealing the factors that act as baseline controls on soil carbon stocks in this ecoregion of carbon-dense soils. These factors include a range of soil physical, parent material, and topographic controls, with land use and climate factors also playing a role. Conclusions: Forest harvesting has limited potential to alter forest soil C stocks in either direction, in contrast to the significant changes driven by land use shifts. These findings underscore the importance of understanding soil C changes at intermediate scales, and the need for an all-lands approach to managing soil carbon for climate change mitigation in the Northeast U.S. [ABSTRACT FROM AUTHOR]

Correctly identifying and handling the relationship between land use carbon emission efficiency (LUCEE) and land ecological security (LES) are important to promote carbon neutrality in the overall layout of ecological civilization construction. This study takes 30 provinces in China as the research unit and measures the level of LUCEE and LES in each province in the period from 2011 to 2020 via a super-efficient slack-based measure model considering undesirable output. The coupling coordination degree (CCD) of LUCEE and LES is calculated, and its spatiotemporal evolution pattern is explored by kernel density estimation and standard deviational ellipse (SDE). The Dagum Gini coefficient is used to study spatial regional differences and the sources of differences. Results show that (1) China's LUCEE exhibited a downward and then an upward trend, as well as a spatial pattern of "high in the west and low in the east" with obvious regional differences. The LES experienced a positive transformation of "less secure → basically secure → more secure" nationwide, with no apparent regional differences. (2) The kernel density curves showed a continuous increase in CCD in general, while interprovincial differences increased, then decreased, and shifted from multipolar to bipolar differentiation. (3) The migration of SDE centers in CCD demonstrated a path of "southeast → southwest → northeast," and the ellipticity increased from 0.167 to 0.173, showing a trend of concentrated distribution. (4) The overall Gini coefficient of the national CCD indicated a decreasing trend, but imbalances remained, with the largest annual average value in the western region (0.120) and the smallest in the northeast (0.044). The main source of regional disparity was the intensity of transvariation. Accordingly, this study proposes targeted regional development strategies to promote low-carbon sustainable land use and improve the ability of land ecosystems to prevent security risks. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effect of conversion from natural forest to cinnamon plantation on the top 1 m soil carbon stocks and soil characteristics. The project was conducted on Andosols of Kerinci Regency, Sumatera, Indonesia, sampling the soil profile under natural forests and a chronosequence of cinnamon plantations of different ages (1, 5 and 10 years). SOC stocks were quantified alongside physical properties (bulk density) and chemical properties (carbon, nitrogen, C/N ratio) to investigate the impact of land conversion. SOC stocks increased 1 year after conversion to cinnamon plantations, but then tended to decrease as the plantations got older. The initial increase was observed alongside decreasing bulk density 1 year after forest conversion to cinnamon plantation, likely as a result of the fresh input of (less dense) pyrogenic soil organic matter as a result of slash and burn practices and transport down the soil profile owing to leaching. In older plantations SOC stocks were lower, probably because organic matter had been decomposed or leached out of the profile. The free particulate organic matter (fPOM) was isolated from selected topsoil and subsoil layers and analysed for carbon, nitrogen, and FTIR analysis. FTIR analysis revealed that topsoil fPOM contained more aromatic functional groups than subsoils and had a higher degree of decomposition. Aromatic and carbohydrate functional groups were initially lower in recently converted cinnamon plantation, but the trend was reversed 10 years after conversion. The initial flush of fresh organic matter into soils after slash and burn provides fPOM with a lower degree of decomposition but is short-lived and fPOM becomes more microbially processed as the cinnamon plantation ages. We conclude that, after a short term increase brought about by slash and burn, forest conversion to cinnamon plantation in Kerinci Regency depletes SOC stocks both in topsoils and subsoils. [ABSTRACT FROM AUTHOR]

The sustainable aviation fuel (SAF) raw material planting process will inevitably cause carbon emissions from induced land use change (ILUC). However, limited by the regional specificity of energy plants, the ILUC emissions value of SAF is less considerable in the case of soil carbon sequestration during the raw material planting process. Therefore, this study used the CENTURY model to predict the carbon sequestration of soil in Jatropha plantations and compared it with the preparation of aviation fuel from soybean oil. The results showed that, when considering ILUC combined with the carbon sequestration effect of the raw material planting land, life-cycle greenhouse gas emissions of the two methods for producing Jatropha oil–based aviation kerosene (pathway 1: oil residue used for fertilizer or power generation; pathway 2: oil residue detoxified and used for animal feed) were −36.1 g CO2e/MJ and −59.4 g CO2e/MJ, respectively. The life-cycle greenhouse gas emissions of soybean oil–based aviation kerosene under the condition of straw returning and without straw returning are 2.9 g CO2e/MJ and 66.1 g CO2e/MJ, respectively. Compared with petroleum aviation fuel, the emission reduction potential of Jatropha oil-based aviation kerosene increased from 84.38% and 110.56% to 140.6% and 166.7%, respectively, based on the original core life cycle assessment (cLCA)+ILUC, considering soil carbon sequestration. The emission reduction potential of soybean-based aviation kerosene increased from 42.81 to 96.7% (with straw returned to the field) and 25.7% (without straw returned to the field). The results show that Jatropha oil–based aviation kerosene has great potential in terms of negative carbon emissions when considering the carbon sequestration effect of soil in the energy plant planting area. In the future, large-scale planting on marginal land with a climate suitable for Jatropha growth will help the civil aviation industry reduce carbon emissions and achieve carbon neutrality. [ABSTRACT FROM AUTHOR]

Land use changes affect soil and biomass carbon sequestration potential of the agroecosystems of most Sub-Sahara Africa facing rising temperatures due to global climate change. One such ecosystem is the Owabi reservoir catchment in Ghana, which has undergone extensive changes in land use through urbanization. Our study aimed to determine the impact of the spatial and temporal variability of the different land uses on soil and biomass carbon storage in the Owabi catchment. Land use/cover maps were elaborated using SPOT satellite images of 30 × 30-m resolution and Erdas Imagine and ArcGIS Pro softwares. Soil and vegetation were sampled along three transects in the Y plane in early 2014. Nested plot design and temporary sample plots of 50 × 50 m were demarcated within a 1 ha plot in each of the land uses. Trees, herbs and litter were sampled to assess aboveground carbon, and soil samples were taken at 0–15 cm and 15–30 cm depth. Belowground (root) biomass was calculated using the root:shoot ratio. Seven (7) land use types – dense forest, sparse forest, grassland, cropland, wetland, settlement, and excavated land – were identified and differences in carbon stocks were assessed. Soil carbon stock (0–30 cm) ranged from 51.80 Mg/ha in dense forest to 7.00 Mg/ha in excavated land. Our study showed that the conversion of forest lands to other land uses through excavation resulted in about 30-folds loss in carbon and also a major loss of carbon in the catchment from c. 1.4 × 106 Mg C in 1990 to 0.55 × 106 Mg C in 2014. Enhancing forests or growing trees to sequester carbon seems to be the optimum choice among the seven land uses if the introduction of payment for environmental services options is considered. [ABSTRACT FROM AUTHOR]

In order to investigate the characteristics of soil structural stability and the factors influencing it under typical land use types in the karst region of western Hubei, soil samples were collected from five land use types (natural mixed forest [NF], cypress forest [CF], stone dike terrace [ST], stone dike forest [SF], and abandoned land [AL]) in Xialaoxi to analyze the particle size distribution of aggregates, structural stability, and the distribution characteristics of carbon, nitrogen, and extracellular enzyme contents. The results showed that the aggregates of NF, CF, SF, and AL were dominated by >2‐mm aggregates, while ST showed mostly 2–0.25‐mm aggregates. The mean weight diameter (EMWD) and the geometric mean diameter (EGMD) of mechanical aggregates showed a trend of CF > NF > SF > AL > ST, whereas the erodibility factor K showed an opposite trend. The total organic carbon (TOC), labile organic carbon (LOC), and total nitrogen (TN) contents of aggregates of each particle size were significantly higher in NF and CF than in ST and AL under the five land types. The content of available nitrogen (AN) was highest in NF and ST. The content of carbon and nitrogen and extracellular hydrolases (β‐glucosidase [BG], cellulose disaccharide hydrolase [CBH], β‐N‐acetyl‐aminoglucosidase [NAG], and leucine aminopeptidase [LAP]) in soil aggregates were mainly concentrated in <0.25–0.053‐mm aggregates. The variation in carbon and nitrogen abundance of each particle size agglomerate mainly originated from the LAP content of that particle size agglomerate and showed significant correlation. The partial least squares path models (PLS‐PM) showed that the main influences on the stability of soil aggregates in small watersheds were land use types, soil physical properties, carbon and nitrogen abundance, and extracellular enzyme activity. In conclusion, the structural stability of soil aggregates in Xialaoxi watershed is the result of the interaction between human disturbance and soil nutrient self‐cycling. In general, NF and CF have better soil aggregate stability and are conducive to soil carbon and nitrogen accumulation, whereas for later development and management of SF, ST, and AL sample plots, scientific cultivation means should be adopted, and attention should be paid to long‐term carbon and nitrogen accumulation and conservation. [ABSTRACT FROM AUTHOR]

The azonal organo-accumulative soils (Umbrisols) on shungite rocks and the effect of land use on their properties and ecosystem carbon stock have been studied. The changes in soil profile morphology, main agrochemical and microbiological characteristics of the upper horizons, Corg and Cmic stocks in the 100-cm soil layer, and the structure of carbon pools are analyzed. Pine forest (control), arable land, hayfield, young alder stand, and middle-aged mixed forest are examined. In contrast to zonal soils, a change in land use does not considerably transform the properties of shungite soils. The removal of stones has the greatest effect, leading to the formation of developed arable horizons. The soils are characterized by highly skeletal shallow weakly differentiated profile, low bulk density, and pH close to neutral. A wide range of the Corg content (1.6 to 11.7%) results from a heterogeneous composition of the parent rock. Agricultural development contributes to the accumulation of exchangeable bases and available potassium and phosphorus, the contents of which are initially elevated in shungite soils. Characteristic of all examined sites is a high rate of organic matter mineralization (C/N ratio ≤17). A low Cmic content (84–245 mg C/kg) is recorded in the soils, which is explainable with a low availability of the substrate determined by a lithogenic nature of carbon and increased concentrations of heavy metals and lanthanides in shungite rocks. Soil Corg stock varies in the range of 17–251 t C/ha and Cmic stock, of 6–43 g C/m2. The total ecosystem carbon stock is the highest in hayfield (259 t C/ha) and lowest in young forest (74 t C/ha). The total carbon stock in the arable sites, middle-aged forest stand, and control forest is within 169–211 t C/ha. [ABSTRACT FROM AUTHOR]

The role of carbon sequestration in terrestrial ecosystems is crucial for achieving carbon neutrality. This study primarily focuses on examining the carbon storage in Shaanxi Province under different land-use scenarios. This study employed the LP-PLUS-InVEST model to explore the characteristics and spatial and temporal changes in carbon storage across four scenarios (business-as-usual (BUS), ecological protection (EPS), water–energy–food (WEF), and rural revitalization (RRS)) in Shaanxi Province. The results show that from 2000 to 2020, the carbon storage in Shaanxi Province is on a decreasing trend mainly due to the large occupation of ecological land by economic development. EPS has the largest increase in carbon storage under the four scenarios in 2030 and 2060. On the contrary, BUS has a rapid expansion of construction land, which leads to a gradual decreasing trend in carbon storage. WEF has a gradual increasing trend in carbon storage, while RRS has a trend of increasing and then slowly decreasing carbon storage. The spatial distribution trends of carbon storage in all scenarios were similar; high-carbon-reserve areas were mainly distributed in southern and central Shaanxi, which has a better ecological environment and less construction land, while low-value areas were distributed in the Central Shaanxi Plain, which has high land-use intensity. In terms of the stability of carbon reserves, the stable areas are predominantly concentrated in the Qinling Mountains, while the unstable areas are concentrated in the plain urban areas. Specifically, returning cultivated land to forest and grassland is an important initiative to promote the increase in carbon storage in Shaanxi Province. The decrease in carbon storage is mainly affected by strong urban expansion. Our study optimizes the land-use pattern according to the development needs of Shaanxi Province, and promotes the integrated development of ecological protection, food security, and economic development. Guidance is provided to promote regional carbon neutrality. [ABSTRACT FROM AUTHOR]

Background and aims: Grasslands hold one of the most important soil carbon stocks in the world, which is vulnerable to climate change (i.e. precipitation) and human disturbance (i.e. land-use). This study aimed to investigate responses and mechanisms of soil organic carbon (SOC) decomposition and accumulation to precipitation and land-use in an Inner Mongolian grassland. Methods: Using a randomized complete block design with a split plot, an experiment with land-use regimes (fencing, grazing, and mowing, since 2011) and altered precipitation amount (wet, + 50% precipitation; CT, ambient precipitation; dry, −50% precipitation; since 2016) was conducted to explore their impacts on SOC decomposition (represented by soil heterotrophic respiration and extracellular enzyme activities) and accumulation (represented by SOC and its physical fractions) from samples collected in 2019. Results: SOC decomposition significantly increased under wet treatment, but decreased under dry treatment. Wet treatment increased SOC accumulation via the increment of mineral-associated organic carbon (MAOC), and vice versa for dry treatment. Precipitation amount may affect soil microbial biomass and activities via alterations of water supply, plant-derived carbon input, and other soil properties, leading to changes of SOC dynamics. Nevertheless, land-use regimes had little influences on SOC dynamics. Conclusions: Compared to land-use regimes, precipitation treatments can significantly change SOC dynamics. Overall, SOC increased under higher precipitation amount, but decreased with less precipitation. We emphasize that the SOC stock in Inner Mongolia temperate grassland may have an unexpectable fast response to precipitation alteration, but more investigation is still needed in longer terms. [ABSTRACT FROM AUTHOR]

Land-use systems (LUSs) and soil types (STs) are strongly related to factors that influence soil degradation and carbon (C) loss. However, the way in which land use and soil type affects the soil organic C (SOC) pools, and soil aggregation in the Sanjiang Plain, has not been thoroughly investigated. Therefore, this study aimed to investigate soil physic–ochemical properties, soil aggregates, and C management index (CMI) in three different LUSs (grassland, dryland, and paddy field) under two STs (meadow soil and albic soil) of the Sanjiang Plain in northeast China. A total of 60 composite soil samples were collected for laboratory analyses. The results were as follows: soil properties were affected by LUS and ST, especially soil chemical properties; ST had no significant effect on soil aggregates but significantly affected its SOC content, while LUS had a significant effect on soil aggregates (p < 0.01), except for small macro-aggregates (2–0.25 mm); the mean weight diameter (MWD) and SOC in meadow soil was significantly different under different land uses, with grassland being the highest and dryland the lowest. However, there was no significant difference in albic soil. The heterogeneity of grassland, dryland, and paddy field showed that different LUSs had particular effects on SOC and its active components because LUS had significant effects on C pool index (CPI) and CMI, but ST and its interaction had no significant effects on CPI and CMI. Overall, the results showed that LUS was an important factor affecting CMI in the Sanjiang Plain, rather than ST, and the paddy field CMI was optimal in the Sanjiang Plain. [ABSTRACT FROM AUTHOR]

Copyright of Agro-Knowledge Journal / Agroznanje is the property of University of Banja Luka, Faculty of Agriculture and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Background: The restoration of conventional tea plantations and the adoption of organic farming practices could impact soil organic carbon (SOC) and nitrogen (N) stocks. This study investigated the soil properties, SOC and N contents and stocks, and their vertical distributions of a secondary forest restored from an abandoned conventional tea plantation and a converted organic tea plantation. An adjacent conventional tea plantation employing similar intermediate farming served as a comparison. Results: Within a 50-cm depth, the secondary forest exhibited a higher SOC stock of 115.53 ± 7.23 Mg C ha− 1 compared to 92.1 ± 8.54 Mg C ha− 1 for the conventional tea plantation. No significant differences in N stocks were seen between the two land uses. Significantly high SOC and N contents and stocks were found in the 0–10 cm layer of the secondary forest compared to the conventional tea plantation. No significant disparities in SOC and N stocks were found between the conventional and organic tea plantations within the 50 cm depth (92.1 ± 8.54 Mg C ha− 1 and 10.06 ± 1.01 Mg N ha− 1 vs. 97.47 ± 1.53 Mg C ha− 1 and 9.70 ± 0.10 Mg N ha− 1). However, higher levels of SOC and N contents and stocks were observed at a depth of 10 cm in the conventional tea plantation and below 10 cm in the organic tea plantation. Conclusions: The C and N inputs derived from high litter production at the top soil strongly contributed to higher SOC and N contents and stocks in the secondary forest. The application of soybean amendments in the conventional tea plantation and the longer tea plantation age of the organic tea plantation influenced their distribution of SOC and N contents and stocks, respectively. Reverting a conventional tea plantation into a secondary forest contributed to C recovery and reaccumulation. The conventional tea plantation, employing similar intermediate farming practices, increased SOC and N contents and stocks in the surface soil compared to the organic tea plantation. However, adopting organic farming did not significantly increase SOC stocks compared to the conventional tea plantation. [ABSTRACT FROM AUTHOR]

Land use change is one of the major sources of extra CO2 emission, which increasing in CO2 in the atmosphere leads to a global negative effect. Therefore, it is necessary to study the effect of land use change from forest to orchard and agricultural land on carbon stock, especially in developing countries, where its rate might be high, while reliable data are scarce. In this study, soil respiration and carbon stock of dense forests, open forests, as well as an orchard and arable land were considered as the common forms of land use in the Hyrcanian region, north of Iran. After field trip in the dense and open forests, circular plots (1000 m2) were employed systematically. The diameter at the breast height (D.B.H) of all the trees (D.B.H ≥ 12.5 cm) and total height (Ht) was recorded in each plot of dense and open forests, as well as in orchards. Soil physical–chemical properties were studied by taking samples (0–10 cm depth) from each land use. Soil CO2 efflux was measured with closed chambers and the root respiration measured using the root exclusion bag (2 mm size) method. The above-ground biomass of the trees (AGB) was calculated by allometric models of the Hyrcanian forest. The greatest above-ground biomass was observed in the dense forest (330 ± 13.16 t ha−1), followed by open forest (86 ± 6.49 t ha−1) and orchard (7 ± 2.11 t ha−1). The highest and lowest soil carbon stock was observed in dense forests and arable land. The highest and lowest soil microbial respiration was measured in the dense forest (51.40 ± 0.90 mol C h−1 m−2) and arable land (38.28 ± 1.40 mol C h−1 m−2). The root respiration was the highest in the orchard (16.69 ± 2.26 mol C h−1 m−2). The total carbon stock of the orchard (50.77 ± 3.57 t ha−1) was not significantly different (p > 0.05) from that of the open forest and agricultural field. According to obtained results it can be stated that, due to the importance of reducing greenhouse gases along with the need for food, it seems that the introduction of multipurpose trees into the agricultural land or agroforestry systems would be a good practice for mitigating both important concerns. [ABSTRACT FROM AUTHOR]

Agriculture soils play a crucial role in carbon storage and food security. However, uncertainty remains about soil carbon stocks due to spatial variability. This study estimated soil carbon stocks in agricultural land and examined the impact of land use and soil properties on soil organic carbon in Ratchaburi Province, Thailand. Soil samples were collected at three depths (0-10, 10-20, and 20-30 cm) within five different land use types: cassava, coconut, paddy fields, pineapple, and sugarcane. The results revealed that soil organic carbon decreased with increasing depth. Significant differences in soil carbon and soil properties were observed among land uses. The carbon stocks at 0-30 cm depth were as follows: coconut (35.87 mg C/ha), paddy fields (31.17 mg C/ha), sugarcane (28.02 mg C/ha), pineapple (21.79 mg C/ha), and cassava (16.12 mg C/ha). The carbon stocks were significantly correlated with sand, density, clay, silt, and pH. This study highlights the impact of land use types on carbon stocks in agricultural soils and emphasizes the role of soil properties, particularly soil texture, in influencing carbon storage variability. Furthermore, the study highlights the carbon storage potential in agricultural areas, which could guide the formulation of policies to utilize agricultural land to offset CO2 emissions from other sectors. [ABSTRACT FROM AUTHOR]

Land-use change from forest to arable lands may have a major significance on soil processes, properties, and functioning. This research investigated the influence of long-term land-use change from untouched forests to arable lands under northern and southern slope aspects on soil physical and chemical properties. Six regions of the Zagros area in the west of Iran, where the increasing trend of forest to agricultural land conversion has occurred during the last decades, were selected for this study. Composite soil samples were collected from the 0-20 cm depth in both the northern and southern slopes of native forests and their related cultivated areas. The highest dispersible clay and soil bulk density and the lowest aggregate stability were observed in cultivated areas. Soil organic carbon and total N declined in response to the land-use change from forest to cultivated areas in all study areas. The highest amounts of soil organic carbon, total N, C/N ratio, and available P were observed in northern slopes compared with southern slopes in some studied regions. In general, the conversion of natural forests to agricultural cropping systems resulted in soil quality declining. However, the deterioration intensity in the northern and southern slope aspects was similar approximately. [ABSTRACT FROM AUTHOR]

Background: Anthropogenic land use changes (LUCs) impart intensifying impacts on soil organic carbon (SOC) turnover, leading to uncertainty concerning SOC mineralization patterns and determining whether soils act as "source" or "sink" in the global carbon budget. Therefore, understanding the SOC mineralization characteristics of different LUC patterns and their potential influencing factors is crucial. An indoor incubation experiment was conducted to study the SOC mineralization patterns and their relevance to soil physicochemical properties, soil enzyme activity, SOC fractions, and bacterial alpha diversity. The soils were collected from two layers of five typical LUC patterns in Yellow Sea Forest Park, including four that were converted from wheat–corn rotation systems [a gingko plantation (G), a metasequoia plantation (M), a gingko–wheat–corn agroforestry system (GW), and a gingko–metasequoia system (GM)] and a traditional wheat–corn system (W). Results: LUCs had significant and diverse impacts on the SOC content and SOC fraction contents and on soil enzyme activity. The cumulative SOC mineralization was significantly higher in the M systen than in the W and GW systems at 0–20 cm depth and higher in the G system than in the GW system at 20–40 cm depth after 60-day incubation. The mineralization ratio was highest in the W system and lowest in the GW system. The soil pH and bulk density had a significant negative correlation with the cumulative SOC mineralization, while the soil bacterial Shannon index had a significant positive correlation with cumulative SOC mineralization. Multiple stepwise linear regression analysis showed that the SOC mineralization potential was dominantly explained by the bacterial Shannon index and operational taxonomic units (OTUs). The GW system had lower potentially mineralizable SOC and higher SOC stability. Additionally, the incubation time and cumulative SOC mineralization were well fitted by the first-order kinetic equation. Conclusions: LUCs significantly changed SOC mineralization characteristics and the results highlighted the important roles of the bacterial community in soil carbon cycling, which contributes to the fundamental understanding of SOC turnover regulation. [ABSTRACT FROM AUTHOR]

Greenhouse gas stabilisation in the atmosphere is one of the most pressing challenges of this century. Sequestering carbon in the soil by changing land use and management is increasingly proposed as part of climate mitigation strategies, but our understanding of this is limited in quantitative terms. Here we collate a substantial national and regional data set (15790 soil cores), and analyse it in an advanced statistical modelling framework. This produced new estimates of the effects of land use on soil carbon stocks in the UK, different in magnitude and ranking order from the previous best estimates. Soil carbon stocks were highest in woodlands, followed by rough grazing and semi-natural grasslands, then improved grasslands, and lowest in croplands. Estimates were smaller than the previous estimates, partly because of new data, but mainly because the effect is more reliably characterised using a logarithmic transformation of the data. With the very large data set analysed here, the uncertainty in the differences among land uses was small enough to identify consistent mean effects. However, the variability in these effects was large, and this was similar across all surveys. This has important implications for agri-environment schemes, seeking to sequester carbon in the soil by altering land use, because the effect of a given intervention is very hard to verify. We examined the validity of the "space-for-time" substitution, and although the results were not unequivocal, we estimated that the effects are likely to be over-estimated by 5-33%, depending upon land use. [ABSTRACT FROM AUTHOR]

Today's agri-food systems face the triple challenge of addressing food security, adapting to climate change, and reducing the climate footprint by reducing the emission of greenhouse gases (GHG). In agri-food systems, changes in land use and land cover (LULC) could affect soil physicochemical properties, particularly soil organic carbon (SOC) stock. However, the impact varies depending on the physical, social, and economic conditions of a given region or watershed. Given this, a study was conducted to quantify the impact of LULC and slope gradient on SOC stock and C sequestration rate in the Anjeni watershed, which is a highly populated and intensively cultivated area in Northwest Ethiopia. Seventy-two soil samples were collected from 0–15 and 15–30 cm soil depths representing four land use types and three slope gradients. Soil samples were selected systematically to match the historical records (30 years) for SOC stock comparison. Four land use types were quantified using Landsat imagery analysis. As expected, plantation forest had a significantly (p < 0.05) higher SOC (1.94 Mg ha−1) than cultivated land (1.38 Mg ha−1), and gentle slopes (1–15%) had the highest SOC (1.77 Mg ha−1) than steeper slopes (> 30%). However, higher SOC stock (72.03 Mg ha−1) and SOC sequestration rate (3.00 Mg ha−1 year−1) were recorded when cultivated land was converted to grassland, while lower SOC stock (8.87 Mg ha−1) and sequestration rate (0.77 Mg ha−1 year−1) were recorded when land use changed from cultivation to a plantation forest. The results indicated that LULC changes and slope gradient had a major impact on SOC stock and C sequestration rate over 30 years in a highly populated watershed. It is concluded that in intensively used watersheds, a carefully planned land use that involves the conversion of cultivated land to grassland could lead to an increase in soil C sequestration and contributes to reducing the carbon footprint of agri-food systems. [ABSTRACT FROM AUTHOR]

Land use change is one of the main factors driving changes in terrestrial carbon storage, which comprises the storage of vegetation carbon and soil carbon. Selecting the Chengdu–Chongqing urban agglomeration (CCUA) as the study area, land use and carbon storage from 2010 to 2030 were analyzed by combining the Future Land Use Simulation (FLUS) model and the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model. The main types of land use in CCUA are farmland and forest. The conversion of farmland to built-up land was the most important form of land use transfer between 2010 and 2020. Each type of land use shows the smallest change under the ecological protection scenario, and the degree of the comprehensive land use dynamic is only 0.19%. Under the natural development scenario, the areas of built-up land, wetland, and forest land will increase in 2030. Under the urban development scenario, the built-up land area will increase by 751.24 km2, an increase in more than 10.08%, but farmland, forest, and grassland will decrease. The spatial pattern of carbon storage is "high in the east and west, low in the middle"; farmland accounts for the largest proportion of carbon storage at over 60% of the total. Carbon storage decreased by 29.45 × 106 Mg from 2010 to 2020. Grassland showed the most significant decrease in carbon storage, with the proportion decreasing from 7.49% in 2010 to 6.09% in 2020. In 2030, the total carbon storage will reach 1844.68 × 106 Mg under the ecological protection scenario, slightly higher than that in 2020, while it will show a downward trend under the natural development and urban development scenarios. [ABSTRACT FROM AUTHOR]

Soil organic carbon (SOC) plays a major role in maintaining long‐term ecological stability. This paper focuses on how land use conversion affects the stability of SOC (e.g., carbon [C] molecular structure) and how soil C cycle‐related enzyme activities are involved in the process. Four land use types around the southern margin of Qinghai Lake were researched: lakeside wetland, natural grassland, cropland, and restored grassland. Soil C was dominated by O‐alkyl carbon (O‐alkyl C, 40.6%–49.3% of total intensity) and alkyl carbon (alkyl C 25.9%–36.7%) in all land use types. Alkyl C and aliphaticity were more abundant in lakeside wetlands than in the other land use types; these values decreased by 29.5% and 36.0%, respectively, after lakeside wetland reclamation. Compared with cropland, restored grassland had higher dissolved organic carbon and β‐glucosidase activity, mainly attributed to the higher plant residues left in the topsoil that provided the polysaccharides required for the higher β‐glucosidase activity. The SOC, labile carbon, alkyl C, and aliphaticity together explained more than 50% of the total variability of soil enzyme activities (p < 0.05) by redundancy analysis, and β‐glucosidase played a regulatory role in soil carbon conversion by path analysis. The lakeside wetland had a more stable SOC than the other land use types around Qinghai Lake at the molecular level due to its higher aliphaticity and aromaticity, which are mainly related to oxygen limitations in lakeside wetlands. To some extent, the accumulation of recalcitrant molecules is limited in restored grassland soils. [ABSTRACT FROM AUTHOR]

Soil and vegetation carbon densities play a critical role in global and regional human-Earth system models. These densities affect variables such as land use change emissions and also influence land use change pathways under climate forcing scenarios where terrestrial carbon is assigned a carbon price. Recently, more spatially explicit, fine resolution data have become available for both soil and vegetation carbon. However, for models to effectively use these data the fine resolution data need to be reharmonized to the initial land use and land cover conditions represented by these models. Without such reharmonization the carbon values may be inaccurate for particular land types and places where the source data and the model disagree on the land use/cover type. Here we present reharmonized soil and vegetation carbon densities both at the 5-arcmin resolution grid cell level and also aggregated to 235 water sheds for 4 land use types and 15 land cover types. These data are particularly useful as initial land carbon conditions for global Multisectoral Dynamic Models (MSD). Moreover, these data include six different statistical states calculated using distinct resampling methods for each of the land use and land cover types. These statistical states are used to define a range of possible carbon values for each land classification, and any state can be used for defining initial conditions of soil and vegetation carbon in MSD models. Users can also estimate any percentile of the carbon distribution defined by these six summary states. We make use of these statistical states to calculate spatially distinct uncertainties in the carbon densities by land type. We have implemented these data in a state-of-the-art multi sector dynamics model, namely the Global Change Analysis Model (GCAM), and show that these new data improve several land use responses in the model, especially when terrestrial carbon is assigned a carbon price. The statistical states in our data are validated against similar estimates in the literature both at a grid cell level and at a regional level. [ABSTRACT FROM AUTHOR]

The importance of carbon (C)–nutrient interactions to the prediction of future C uptake has long been recognized. The Energy Exascale Earth System Model (E3SM) land model (ELM) version 1 is one of the few land surface models that include both N and P cycling and limitation (ELMv1-CNP). Here we provide a global-scale evaluation of ELMv1-CNP using the International Land Model Benchmarking (ILAMB) system. We show that ELMv1-CNP produces realistic estimates of present-day carbon pools and fluxes. Compared to simulations with optimal P availability, simulations with ELMv1-CNP produce better performance, particularly for simulated biomass, leaf area index (LAI), and global net C balance. We also show ELMv1-CNP-simulated N and P cycling is in good agreement with data-driven estimates. We compared the ELMv1-CNP-simulated response to CO 2 enrichment with meta-analysis of observations from similar manipulation experiments. We show that ELMv1-CNP is able to capture the field-observed responses for photosynthesis, growth, and LAI. We investigated the role of P limitation in the historical balance and show that global C sources and sinks are significantly affected by P limitation, as the historical CO 2 fertilization effect was reduced by 20 % and C emission due to land use and land cover change was 11 % lower when P limitation was considered. Our simulations suggest that the introduction of P cycle dynamics and C–N–P coupling will likely have substantial consequences for projections of future C uptake. [ABSTRACT FROM AUTHOR]

Due to the soil formation factors and different geographic areas of Dukagjini Plain, particularly in Rahovec municipality, the variation of soil organic carbon is high. Soil organic carbon (SOC) has a crucial role in the determination of the physical, chemical and biological behaviour of the soil. The most common land use types of this area are vineyards, table grapes, horticulture such as peppers and cabbage, and arable lands such as maize, winter wheat, alfalfa, and meadows. Considering the lack of soil information data in Kosovo, it is necessary to have soil information about this territory. The main objectives of the present study are, therefore: i) to investigate and determine the concentration of the soil organic matter (SOM), SOC, nitrogen (N) and soil pH-H2O, using laboratory analysis, and ii) to show the spatial distribution of SOC, SOM, N and pH using the Kriging and inverse weighting interpolation methods. Spatial variability of soil chemical parameters such as SOM, SOC, N, and pH are important to be interpolated to view the changeable soil properties by kriging and inverse distance weighting method and to generate the continuous sample for site-specific management. Disturbed soil samples were collected from the top soil 0-30 cm and 30- 60 cm depth, to determine selected soil chemical parameters, during June-July 2019. A large number of soil samples were collected, 2087 in the first horizon and 2065 in the second. The average of SOC of the first horizon was 0.91%, which variates from 0.07 to 4.06%, while in the second horizon was 0.0 to 2.84%, the average content of N in the first horizon was 0.09%, which variate from 0.01 to 0.60%, while in the second horizon was 0.0 to 0.39%, meanwhile, the average of soil pH-H2O in the first horizon was 7.67, which variates from 4.25 to 9.35, while in the second horizon was 7.79, which variate from 3.25 to 9.30. [ABSTRACT FROM AUTHOR]

Changes in microbial biomass carbon (MBC) and microbial respiration in soils under five different land‐use systems were evaluated at a regional scale in Santa Catarina State, Southern Brazil, to assess the effects of land‐use change and geographical distribution on the microbial and environmental patterns related to soil carbon (C) dynamics. Results showed that, in the West mesoregion, changes in MBC were correlated to the sampling season in forest and pasture systems. In the Plateau mesoregion, however, a land‐use effect was observed, with MBC decreasing in no‐till and crop‐livestock integration systems. Forest and grassland sites presented the highest values of MBC and microbial activity, while grassland sites showed lower values of the metabolic quotient (qCO2) and higher values of the microbial quotient. The qCO2 was also lower in winter for all land‐use systems. The highest total and particulate organic carbon values were found in forest sites. Chemical–physical characteristics were also observed to be significantly correlated with microbiological variables related to soil microbial C dynamics. In conclusion, land‐use intensity, season, and location were found to be the main drivers of changes in microbial C dynamics. Core Ideas: Land‐use change has affected soil microbial C dynamics.Grassland soils have presented lower metabolic quotient and higher microbial quotient values.Forest and grassland soils have presented the highest values of microbial biomass carbon and microbial activity.Forest sites have shown the highest total and particulate organic carbon values.Land‐use intensity, season, and geographic location were the main drivers of microbial C dynamics. [ABSTRACT FROM AUTHOR]

In this context of climate change, agroforestry systems are acknowledged to have a good potential to increase carbon storage in agricultural areas. However, the carbon storage potential of agroforestry systems still needs to be quantified accurately, especially for hedges. The objectives of this study were to (1) add references to the existing literature on the potential for soil organic carbon (SOC) storage near hedges and (2) identify the main factors that influence the variability in this potential. To this end, we sampled soil in the adjacent fields of 25 hedges in France with mixed crop‐livestock agriculture, with sampling on both sides for 20 hedges and sampling on only one side for five hedges, giving a total of 45 study sites. We measured SOC stocks to a depth of 90 cm at distances of 1, 2, 3 and 10 m from the hedge. The results showed that hedges have a strong potential to store carbon in soils, with a mean increase of 15% in SOC stock within 3 m of the hedge. This increase in SOC stock had high variability because of site characteristics. Additional SOC stocks were the largest in rotations of annual crops and grasslands with a permanent grass strip 1 m wide near the hedge, followed by rotations of annual crops, permanent grasslands and rotations of annual crops and grasslands. Large additional SOC stocks because of the hedge were also associated with soils that had a high C:N ratio. The contribution of this type of land management to soil carbon storage thus depends on the local context in which it is implemented. [ABSTRACT FROM AUTHOR]

Building up stocks of agricultural soil organic carbon (SOC) can improve soil conditions as well as contribute to climate change mitigation. As a metric, the ratio of SOC to clay offers a better predictor of soil condition than SOC alone, potentially providing a benchmark for ecosystem service payments. We determined SOC:clay ratios for 50 fields in the North Devon UNESCO World Biosphere Reserve using 30 cm soil cores (divided into 0–10 cm and 10–30 cm depth samples), with soil bulk density, soil moisture and land‐use history recorded for each field. All the arable soils exceeded the minimum desirable SOC:clay ratio threshold, and the ley grassland soils generally exceeded it but were inconsistent at 10–30 cm. Land use was the primary factor driving SOC:clay ratios at 0–10 cm, with permanent pasture fields having the highest ratios followed by ley grass and then arable fields. Approximately half of the fields sampled had potential for building up SOC stock at 10–30 cm. However, at this depth, the effect of land use is significantly reduced. Within‐field variability in SOC and clay was low (coefficient of variation was ~10%) at both 0–10 cm and 10–30 cm, suggesting that SOC:clay ratios precisely characterized the fields. Due to the high SOC:clay ratios found, we conclude that there is limited opportunity to market additional carbon sequestration as an asset class in the North Devon Biosphere or similar areas. Instead, preserving existing SOC stocks would be a more suitable ecosystem service payment basis. [ABSTRACT FROM AUTHOR]

Soil carbon sequestration is vital to reduce the atmospheric carbon concentration, which is expected to increase within future climatic scenarios. The present study aims to investigate the effects of land use changes to different plantation systems on SOC stocks, and simulate these changes using the RothC model in Mizoram, India. With this aim, four land uses, viz., secondary forest, oil palm, orange, and arecanut plantations, established on degraded shifting cultivation lands, and a control natural forest were selected for this study. The soils were sampled 0–30 cm in the secondary forest, plantations, and the natural forest, at an interval of five years. Measured SOC stocks were the highest in the secondary forest (67.0 Mg C ha−1) and the lowest under the oil palm plantation (37.4 Mg C ha−1), 10 years after land use conversion. The climate change projections for 2021–2035 and 2036–2050 indicated that temperature and rainfall changes, projected to increase by 0.8 and 2.0 °C, and 5.9 and 5.4%, respectively, will affect SOC stocks in the future differently, depending on the land use and carbon input from vegetation. Baseline climate simulations under land use change showed the highest increase in the SOC stock under the secondary forest (116%), and the lowest in the oil palm plantation (27%). Overall, the model predicted that SOC stocks would increase, but the rate of change (0.23–1.86 Mg C ha−1 yr−1) varied with different land uses, plant species, and land management practices. The model results indicated that restoring secondary forest following the abandonment of a shifting cultivation and orange plantations are the best options to improve SOC stocks within future climate change scenarios. Conversely, arecanut and oil palm need to be reduced because the SOC storage is lower. [ABSTRACT FROM AUTHOR]

Climate change vigorously threats human livelihoods, places and biodiversity. To lock atmospheric CO2 up through biological, chemical and physical processes is one of the pathways to mitigate climate change. Agricultural soils have a significant carbon sink capacity. Soil carbon sequestration (SCS) can be accelerated through appropriate changes in land use and agricultural practices. There have been various meta-analyses performed by combining data sets to interpret the influences of some methods on SCS rates or stocks. The objectives of this study were: (1) to update SCS capacity with different land-based techniques based on the latest publications, and (2) to discuss complexity to assess the impacts of the techniques on soil carbon accumulation. This review shows that afforestation and reforestation are slow processes but have great potential for improving SCS. Among agricultural practices, adding organic matter is an efficient way to sequester carbon in soils. Any practice that helps plant increase C fixation can increase soil carbon stock by increasing residues, dead root material and root exudates. Among the improved livestock grazing management practices, reseeding grasses seems to have the highest SCS rate. [ABSTRACT FROM AUTHOR]

Soil process models such as RothC typically assume soil organic carbon (SOC) is in equilibrium at the beginning of each simulation run. This is not likely to be true in the real world, since recalcitrant SOC pools (notably, humified material) take many decades to re-stabilize after a land use change. The equilibrium assumption stems from a spinup method in which the model is run under a single land use until all SOC pools stabilize. To overcome this, we demonstrate an alternative spinup procedure that accounts for historical land use changes. The "steady-state" and "historical" spinup methods both impute unknown C inputs such that the modeled SOC matches empirical measurements at the beginning of the simulation and set initial SOC fractions. Holding all other parameters equal, we evaluated how each spinup affects SOC projections in simulations of agricultural land use change in the U.S. state of Vermont. We found that projected SOC trajectories for all land use scenarios are sensitive to the spinup procedure. These differences are due to disparities in imputed below-ground plant-derived carbon between the two procedures. Compared to the steady-state, imputed C in the historical spinup is higher for land uses that increase SOC (e.g., adoption of regenerative practices) and lower for land uses that decrease SOC (e.g., a transition from pasture to crops), due to the time window within which land use changes are assumed to have occurred. The novel historical spinup procedure captures important dynamics commonly missing in previous studies, representing an advancement in soil process modeling. [ABSTRACT FROM AUTHOR]

In this study, the amount of organic carbon in the soil of sacred grove lands was examined to determine the Zagros oak forests' capacity in carbon sequestration. For this purpose, the amount of soil organic carbon (SOC) storage in the Zagros forest and some of their most important characteristics (soil bulk density (BD), %C, SOC, %N, C/N, pH, electrical conductivity (EC)) in four land uses (sacred groves, silvopastoral lands, destroyed forest areas and agricultural lands) were examined and compared. In all four land uses, a total of 200 soil samples at two depths were prepared and analyzed. The results showed that different land uses have a significant effect on the amount of each of the mentioned variables ( α = % 1 ). Furthermore, at the two studied depths, there was a significant difference in the amount of each of the variables studied except in soil bulk density (BD). SOC rate in sacred groves and agricultural lands had the highest and lowest values, respectively (84.37 and 23.3 t/ha). At the first depth of sacred groves alone, the SOC rate was approximately 1.8 times that of the total of silvopastoral areas, twice the rate of that in destroyed forest areas and more than three times the SOC rate in agricultural lands. At both examined depths, sacred groves soil samples had the highest values of %C, %N, N/C and EC and the lowest bulk density. According to the results, forest ecosystems which are protected against human interference play an important role in the long-term storage of carbon in the soil. [ABSTRACT FROM AUTHOR]

Alteration in land use and land cover is the key factor affecting the soil carbon fractions and its distribution. A study was carried out to estimate the carbon fractions in soils of agricultural, forest and pasture lands in two different areas separated on the basis of industrial activities (spoiled and unspoiled) to get an insight on the long-term soil carbon storage potential. The results showed that the mean values of the total organic carbon (TOC) and various fractions are significantly different between the land use types (p < 0.05). Irrespective of the land uses, the forest land showed significantly higher TOC (7.97) than agricultural land (6.98) and pasture lands (6.68). Further, evaluation of carbon management index (CMI) indicated that forest lands had highest CMI value compared to the other land uses. The spoiled area had significantly higher TOC and carbon fractions than their respective counterparts in the unspoiled area (p < 0.05) due to the negative industrial impact on soil biological processes. The PCA separates the sources of different carbon fractions and revealed an association of N (nitrogen) and K (potassium) with VL (very labile) and L (labile) fractions and the association of P (phosphorous) with stable R (recalcitrant) form. Therefore, it can be inferred from the present study that alterations in land use not only result in soil quality degradation but also trigger a reduction in potential for long term soil C sequestration. [ABSTRACT FROM AUTHOR]

Rainfed lower Himalayas are being faced by soil degradation due to change in land use practices which in turn influence the carbon (C) inputs into the soil and microbial activities. A study was carried out to evaluate the labile organic C pools, soil enzymes and microbial indices in the dominating land use practices of the region. There were six land uses practices viz. forestry, agroforestry, silvipastoral, horticulture, agro-horticulture and agriculture. Soil samples were collected from three depths 0–5, 5–10, 10–15 cm for the labile C pools and the microbial activities were studied for 0–15 cm soil layer. The labile organic C pools viz. permanganate-oxidizable carbon (POXC), microbial biomass C (MBC), cold water extractable organic carbon (CWEOC) and carbohydrate carbon (CHO-C) content were significantly higher in soils under forestry (1.46 g kg−1, 0.227 g kg−1, 80 µg g−1, 389 µg g−1, respectively) and silvipastoral (1.15 g kg−1, 0.193 g kg−1, 70.7 µg g−1, 379 µg g−1, respectively) land uses and was lowest in soils under agriculture (0.88 g kg−1, 0.115 g kg−1, 56 µg g−1, 310 µg g−1, respectively). The labile C pools decreased with the increase in soil depth and the decrease being higher in soils under forestry. The microbial quotient (qmic) decreased on moving from forestry to other land uses and the decrease was highest in soils under agriculture by 38.6%. However, the metabolic quotient was highest in soils under agriculture (0.175 μg CO2-C day−1 μg biomass C−1) and lowest in soils under forestry (0.128 μg CO2-C day−1 μg biomass C−1). The metabolic potential was highest in soils under agroforestry (0.046 μg TPF h−1 μg C−1). Principal component analysis identified qmic and MBC as the most dominant and reliable indicators for the assessment of soil quality under different land uses. The results indicate that under rainfed conditions, silvipastoral land use seems to be comparable to forestry in influencing the microbial indices, labile C pools and C stock. [ABSTRACT FROM AUTHOR]

Current study was conducted to evaluate the effect of important land uses and soil depth on soil organic carbon pools viz. total organic carbon, Walkley and black carbon, labile organic carbon, particulate organic carbon, microbial biomass carbon and carbon management index (CMI) in the north Western Himalayas, India. Soil samples from five different land uses viz. forest, pasture, apple, saffron and paddy-oilseed were collected up to a depth of 1 m (0-30,30-60,60-90 cm). The results revealed that regardless of soil depth, all the carbon pools differed significantly (p < 0.05) among studied land use systems with maximum values observed under forest soils and lowest under paddy-oilseed soils. Further, upon evaluating the impact of soil depth, a significant (p < 0.05) decline and variation in all the carbon pools was observed with maximum values recorded in surface (0-30 cm) soils and least in sub-surface (60-90 cm) layers. CMI was higher in forest soils and lowest in paddy-oilseed. From regression analysis, a positive significant association (high R-squared values) between CMI and soil organic carbon pools was also observed at all three depths. Therefore, land use changes and soil depth had a significant impact on soil organic carbon pools and eventually on CMI, which is used as deterioration indicator or soil carbon rehabilitation that influences the universal goal of sustainability in the long run. [ABSTRACT FROM AUTHOR]