Search

• Wetlands topsoil can sequester more C than farmlands and forestlands. • Soil water content was important factor affecting microbial abundance and enzyme activity. • Higher soil water content can increase soil C storage by stimulating C fixing enzyme activity. • Soil C storage were negatively driven by soil bacterial abundance under different land-use. Soil carbon storage plays a crucial role in mitigating the climate warming and is significantly impacted by the land use pattern. To better understand soil carbon stability and the underlying microbial mechanism, based on qPCR, ELISA, and fluorescence techniques, the effects of land use changes on soil microbial abundance, enzyme activity, and soil carbon storage were investigated in the complex ecosystems of cropland, forestland, and wetland along three typical river (Wolvlan river, Bielahong river, Wusuli river) basin in Sanjiang Plain, China. We hypothesised that croplands soil carbon storage is lower than forestlands and wetlands, which is regulated by soil water content, microbe and enzyme activity. Results showed that topsoil TC in wetlands (85.54 mg·g−1) was higher than those in croplands (33.46 mg·g−1) and forestlands (46.13 mg·g−1). Topsoil water content increased 73.90 % and 71.64 % in wetlands than in farmland and forestlands, respectively. Additionally, reclamation diminished topsoil carbon storage. In croplands, soil dissolved organic carbon, microbial biomass carbon, microbial biomass nitrogen, available nitrogen, bacterial abundance, and soil enzymes (i.e., RubisCO, β-glucosidase, cellobiohydrolase, 1,4-N-acetylglucosaminidase and acid phosphatase) activities were substantially lower than those in wetlands. Structural equation modeling showed that soil carbon storage was positively related to soil water content and RubisCO activity but negatively related to soil bacterial abundance. Soil water content had the largest standardised total positive effect coefficient and indirectly influenced soil carbon storage by affecting RubisCO activity. Soil depth had a greater effect on SMC, hydrolase and site had a greater effect on bacteria and fungi abundance. The results highlight that the alteration of carbon fixing enzyme activity by soil water content is a crucial mechanism for soil carbon sequestration in response to land-use change. Management strategies that conserve natural wetlands, increase soil water content and minimize land disturbance would be effective in maintaining soil carbon stocks. [ABSTRACT FROM AUTHOR]

• Soil water content (SWC) is determined as the outcomes of land use changes. • A significant correlation occurred between δ13C and δ15N values in wetlands, but underwent considerable changes after wetland conversion. • The shifts in organic matter sources over time and distinct mechanisms of degradation and preservation of SOM were underscore in wetlands following land use changes. Land use change in wetlands leads to significant losses of soil organic matter (SOM). Stable carbon (C) and nitrogen (N) isotopes offer insights into changes in C3/C4 vegetation, SOM sources, and decomposition processes. Yet, predicting the spatial–temporal dynamics of SOM contents and isotopes under land use changes remains challenging. This study delves into the effects of land use changes on soil organic carbon (SOC), total nitrogen (TN), δ13C and δ15N values, and soil physico-chemical properties and lignin phenols. Our results highlight the significance of soil water content (SWC) in determining the outcomes of land use changes. The conversion of wetland to cropland, forestland and construction land, led to notable reductions in SOC contents (8.71–56.33 %), and TN contents (7.87–37.12 %). Wetland conversion resulted in an enrichment of 13C and 15N abundance, with wetlands exhibiting the lowest δ13C (−25.57 to –22.89 ‰) and δ15N (2.66 to 6.67 ‰) values. A significant correlation occurred between δ13C and δ15N values in wetlands, but underwent considerable changes after wetland conversion. Key parameters, including bulk density (BD), C:N, the acid-to-aldehyde of vanillyl ((Ad/Al)v), lignin content (Λ 8), and total phosphorus (TP), were identified as influencing factors for both SOC and TN contents. When evaluating δ13C values, the most influential factors included silt, C:N, SOC, sand, and BD. These indicate the importance of soil chemical group (from 41 % to 21 %) in elucidating δ13C values declined, while lignin group's (from 9 % to 28 %) importance increased from topsoil to subsoil. The acid-to-aldehyde of syringyl ((Ad/Al)s), Λ 8 , C:N, BD and the cinnamyl-to-vanillyl ratio (C/V) were identified as the primary factors influencing δ15N values, with chemical group accounting for 36 % and lignin group for 48 % in topsoil, while physical group dominated 42 % in subsoil. Our findings underscore the shifts in SOM sources and distinct mechanisms of degradation/preservation of SOM following land use changes. [ABSTRACT FROM AUTHOR]

• The agri-horticulture (AH) system exhibited the highest Carbon management index (CMI). • CMI increased at higher altitude in dry temperate Himalayas. • Passive carbon pool was higher under AH system than agriculture (A) by 16.2 %. • The highest Lability index was reported in A indicating lower stability than AH. Globally, land use management consistently changes the dynamics of labile and recalcitrant (non-labile) soil organic carbon (SOC) fractions. However, the effects vary depending on altitude, soils and management practices. The dry temperate north-western Himalayan region is characterized by the presence of diverse land use systems, however the comparison of these SOC fractions across various land use regimes is not well-documented in the area. This study reported the differences in labile and non-labile SOC fractions under the major land-use systems viz., Agriculture (A), Horticulture (H), Agri-horticulture (AH) and Grass fallow (OF) land in various soil-depth classes (0–20, 20–40 and 40–60 cm) along three altitudinal ranges i.e., 2200–2500, 2500–2800 and 2800–3100 m above mean sea level (m. a.m.s.l.) across the dry temperate region of north-western Himalayas. The lability index and carbon management index of the soils were determined using these fractions. The analysis affirmed the highest accumulation of active fractions viz., very-labile (2.66 mg g−1), and labile C fraction (2.55 mg g−1) under AH, while the highest recalcitrant fractions i.e., less-labile (3.34 mg g−1) and non-labile C fraction (7.46 mg g−1) was documented under H. Moreover, the Carbon Management Index (CMI) followed the order of AH > A > H > OF. All the SOC fractions, pools and CMI significantly increased with increase in altitude but declined at lower soil depths. The Pearson correlation analysis revealed that the CMI was positively correlated with the active C fractions i.e. C frac 1 (r = 0.96; p < 0.05) and C frac 2 (r = 0.9; p < 0.05). The higher active carbon pool and CMI (6.9–16 % and 4.1–15.7 % higher, respectively) under the AH may be due to the greater organic matter inputs to the soil under the agri-horticulture land use system. The findings of this study suggest that the soil can be managed sustainably by the adoption of stable land use systems such as agri-horticulture (owing to their higher CMI values) in the highly fragile dry temperate ecosystem of the north-western Himalayas. [ABSTRACT FROM AUTHOR]

• Land-use types, seasons, slope position significantly affected SOC and SWC. • Revegetation increased SWS consumption and SOC accumulation. • There was a positive linear relationship between SOC and SWC. • Planting grass and shrubs is recommended in the semi-arid hilly and gully regions. Understanding the response of soil organic carbon (SOC) and moisture to different land-use types, slope positions, seasonal variations, and their interactions has great significance for land use and management. However, the coupling effects of SOC and soil moisture in typical hilly and gully regions are still elusive. Therefore, in this study, five different land-use types, including cropland, abandoned land, grassland, shrubland, and forestland were selected in a typical Chinese loess hilly-gully region, and soil samples were collected from 0 to 200 cm profiles at the upper, middle, and lower slope positions in four seasons. The results demonstrated that the distributions of SOC and soil moisture were jointly significantly affected by land-use types, seasons, and slope positions (P < 0.01). Average SOC content was found to be highest in the shrubland, followed by grassland, abandoned land, forestland, and cropland. SOC storage at the lower slope position was 10.97% higher than that at the upper slope position. SOC storage in winter was 45.47% higher than that in summer. SOC storages of abandoned land, grassland, shrubland, and forestland were 17.38%, 33.08%, 52.52% and 1.26% more than that of cropland, respectively. Soil moisture fluctuated greatly in 0–100 cm layers and was stable beneath the 100 cm layers, which was highest in autumn, and lowest in summer. Whereas, under different land-use types, the soil moisture of cropland was the highest, especially significantly higher than all revegetated treatments in the 60–200 cm soil layers. Compared with cropland, soil water storage at other land-use types was averagely 36.45 % lower in the entire 200 cm soil profile. SOC was positively correlated with soil moisture under different factors. Thus, we recommend planting shrub and grass in watersheds with serious soil erosion in the semi-arid hilly and gully region, because they can sequestrate more SOC and retain more soil water. [ABSTRACT FROM AUTHOR]

• Spatial variations in soil erodibility was quantified by indicators in karst hillslope. • Identify the predominant factors affecting spatial variations in soil erodibility. • Land use and slope position had great effects on near-surface soil characteristics. • CSEI varied with land use and slope position, and affected by soil characteristics. Land use type and slope position have a considerable impact on soil properties and thus likely influence soil erodibility. Soil erosion on karst hillslopes in South China is still serious due to the high intensity of human activities and fragile ecological environment. Nevertheless, the potential effects of land use type and slope position on soil erodibility indicators in karst areas are still unclear. This study was conducted to investigate the spatial variations in soil erodibility indicators, namely, the saturated hydraulic conductivity (K S), mean weight diameter (MWD), soil structural stability (SSI), soil erodibility K factor, soil organic carbon content (SOC), and a comprehensive soil erodibility index (CSEI) for three typical land uses and three slope positions on a karst hillslope. The results showed that K S , MWD , SSI , K factor, SOC and CSEI varied significantly with land use type and slope position. The measured K S , MWD , SSI , K factor and SOC at the nine tested sites displayed a similar trend with soil depth. SOC , MWD and SSI contributed more to the CSEI , with contributions of 27.9%, 25.9% and 25.9%, respectively. K S and K factor contributed less to the CSEI , with contributions of 17.7% and 2.5%, respectively. Woodland is most susceptible to erosion on upper, cropland on middle and grassland on lower slope positions according to the values of CSEI. There were significant positive correlations among sand content, bulk density and CSEI , and there were significant negative correlations among clay content, silt content, root mass density, SOC and CSEI. The changes in soil properties and soil erodibility indicators with land use type and slope position led to the differences in the CSEI. The results provide valuable information for policymakers to select appropriate land use types to mitigate soil erosion and thus improve the healthy development of the ecological environment on karst slopes. Moreover, the results have crucial implications for understanding the mechanism of the spatial variation in soil erosion of karst hillslopes in Southwest China. [ABSTRACT FROM AUTHOR]

• The mean soil organic carbon (SOC) content in agroecosystem of Eastern China was 18.24 g kg−1. • The SOC content of planted forest > cropland > grassland in the total study area. • The SOC value of grassland was higher than cropland in North China due to excessive mechanized operation. • The random forest hybrid model exhibited higher comprehensive performance in SOC prediction. • Our predictions were much more detailed and accurate than the existing SOC content maps. Soil organic carbon (SOC) plays a key role in soil function, ecosystem services, and the global carbon cycle. Large SOC stocks accumulate in agroecosystems, but the estimates of SOC distribution and magnitude in agroecosystems still have large uncertainties in global products. Based on multiple high-resolution environmental variables (terrain derived from digital elevation model, climate and organism from Landsat 8 OLI) and 369 observed soil samples from 2019 to 2021, two machine learning methods, random forest (RF) and support vector machine (SVM) models, were used to estimate the content and spatial distribution of SOC in agroecosystems of Eastern China. We proposed a hybrid model in which the optimal predictors of SOC were selected for different land use types (cropland, planted forest and grassland), and it aimed to improve the performance of machine learning. Our results showed that (1) the hybrid models performed better than the global models, and the Random forest-Hybrid (RF-Hybrid) model led to the highest prediction accuracy, with a validation R2 of 0.65 and RMSE of 5.76 g kg−1. (2) The SOC content in the agroecosystems of Eastern China among different land use types ranked in the following order: planted forest (19.92 g kg−1) > cropland (17.51 g kg−1) > grassland (17.30 g kg−1). However, in North China, the SOC content in cropland (14.04 g kg−1) was much lower than that in planted forest (17.21 g kg−1) and grassland (17.07 g kg−1), which was caused by excessive mechanized operation. (3) The agroecosystem in Northeast China presented the highest mean SOC content (26.55 g kg−1) due to low temperature. (4) Our estimations (R2 = 0.53, RMSE = 6.74 g kg−1, 30-m resolution) were more detailed and precise than the existing global SOC maps (Soil Grids: R2 = 0.26, RMSE = 12.44 g kg−1, 250-m resolution; HWSD: R2 = 0.06, RMSE = 41.07 g kg−1, 1000-m resolution). The results may improve the accuracy of agroecosystem carbon mapping and contribute to SOC assessments in agricultural ecosystems. [ABSTRACT FROM AUTHOR]

• Facility lands were considered to be greater carbon sinks compared to other land uses. • The most stable type of organic carbon is in facility land, and the most unstable is in grasslands. • Changes in land use have a significant impact on organic carbon fractions and carbon mineralization. Soil carbon is an essential component that influences soil health and agronomic productivity, and land-use practices significantly impact soil carbon stocks. In this study, the researchers investigated the impact of various land-use types (farmland, orchards, grasslands, and facility lands) on soil organic carbon (SOC) fractions in the Qaidam Basin of China's Qinghai-Tibet Plateau. The soil samples were taken from the 0–10 and 10–20 cm depths. The particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) fractions of various land uses have been measured. The results revealed that grasslands had the greatest POC/SOC ratio (0.59), with POC accounting for the majority of the SOC fraction. In contrast, all other land-use types (facility land, orchards, and farmland) had greater MAOC/SOC ratios than POC/SOC. The facility land had the highest SOC content (17.75 g kg−1), and orchard had the lowest (8.51 g kg−1). The grassland had the highest POC content (9.82 g kg−1) at a depth of 0–10 cm. The trend for MAOC content among the various land-use types was facility lands > farmlands > grasslands > orchards. The soil pH was also observed to be moderately alkaline, with an average of 8. The orchard has the highest bulk density (BD), measuring 1.38 g cm−3. The grasslands contained the highest amount of total nitrogen (TN) (2.2 g kg−1) while the agricultural fields contained the highest amount of total phosphorus (TP) (1.16 g kg−1). In addition, facility lands showed the highest level of microbial activity compared to other land-use types. According to the findings, SOC, POC, and MAOC fractions had considerably positive associations with TN and microbial biomass carbon (MBC), but were significantly negatively associated with metabolic CO 2. The findings imply that different land-use types can have a considerable impact on the quality and amount of soil organic carbon, which has consequences for soil health and ecosystem processes. The findings also highlight the significance of long-term land management practices that promote the preservation and enhancement of soil organic carbon in various land-use systems. [ABSTRACT FROM AUTHOR]

• Grassland had the highest soil infiltration capacity among the land use types with vegetation. • Soil infiltration capacity of anti-dip slope was significantly higher than that of dip slope. • The bedrock strata dip could be treated as an indicator of infiltration properties. • The common experience model was the most suitable for describing the soil infiltration characteristics. The dip of bedrock has a great influence on the infiltration of water into soil, and can control the spatial distribution of rainwater in fragile karst rocky desertification regions. Thus, it is necessary to scientifically assess the soil infiltration capacity of dip and anti-dip slopes in karst trough valleys. In this study, we comprehensively evaluated the soil infiltration capacity of dip and anti-dip slopes under different land use types using the cutting ring infiltration method. The results showed the following. i) Compared with the anti-dip slope, the dip slope had a higher bulk density, noncapillary porosity and pH and a lower soil water content, capillary porosity and soil organic carbon content (p < 0.05). In addition, the soil infiltration capacity of grassland was the highest among the studied land use types except for abandoned land. ii) Both the bulk density and the total soil porosity could be treated as indicators of the infiltration properties of dip and anti-dip slopes.iii) Based on the coefficient of determination, R2 , the common experience model was the most suitable for describing the characteristics of the soil infiltration rate. iv) Based on the principal component equation, the soil infiltration capacity and organic matter of the grassland on dip slopes and anti-dip slopes were higher than those of other land use types with vegetation, but not higher than those of abandoned land without vegetation. The results of this study provide a reference for the selection of the restoration method and the assessment of the soil infiltration capacity of dip and anti-dip slopes in karst trough valleys and other karst landforms with the same geological background. [ABSTRACT FROM AUTHOR]

• A meta-analysis to test rubber stand age and altitude effects on soil properties. • Forest-to-rubber conversion significantly reduced SOC pools by 24%. • Rubber monoculture-to-intercropping significantly increased SOC pools by 6%. • Improvement of intercropping occurred in 0–20 cm soil and at 500–800 m altitude. The rapid expansion of rubber plantations may have greatly influenced the carbon stocks of the ecosystem, with potential impacts on mitigating climate change and future carbon fluxes. Therefore, soil carbon pools and other properties must be reliably estimated after rubber-based land cover transitions. The aim of this meta-analysis is to understand how various land use changes based on rubber plantations affect soil physicochemical properties, especially soil organic carbon (SOC) pools. This study focuses on three land use changes: (1) forest-to-rubber conversion; (2) rubber monoculture vs. intercropping; and (3) the age and altitude of the rubber stand over a chronosequence in rubber plots. Results showed that the conversion of forest to rubber plantation significantly reduced the SOC, microbial carbon (MBC), total nitrogen (TN) and total magnesium pools by 24%, 35%, 13% and 94% respectively, whereas rubber intercropping with different crops profoundly increased the SOC and MBC pools by 6% and 24% on average, respectively. The improvement of rubber intercropping on SOC and properties mainly occurred in the surface soil at 0–20 cm and at altitudes of 500–800 m, but these effects were diminished in the subsurface soil at 20–60 cm and at altitudes higher than 800 m. Rubber intercropping plantations can significantly alleviate soil acidification. Changes in the response ratio of SOC were closely related to the variations in soil clay, bulk density, and C/N ratio. These results suggest that rubber-based land use management policies should promote intercropping plantations, especially those with woody plants, and the altitude of rubber planting should be manipulated to minimize the loss of soil C, N, and other nutrients. [ABSTRACT FROM AUTHOR]

• Soil organic carbon can be predicted by land use and terrain attributes. • Soil erosion can preserve SOC by burying it at downslope deposition locations. To provide a more accurate assessment of soil organic carbon (SOC) stocks in agroecosystems, sampling strategies should be designed in a way that accounts for topographic variability and soil redistribution via erosion and deposition. While the importance of topography for influencing soil properties is long established, recent advances in digital elevation models (DEMs) permit more rapid assessment of topographic attributes. We determined primary terrain attributes from a 3 m DEM to guide sampling in cultivated fields and nearby grasslands in Southeastern Minnesota, USA. Soil samples were analyzed to quantify SOC stocks and activity of 137Cs, a radioisotope employed to track soil movement over decadal timescales. In addition to soil depth, digital terrain attribute values were important for developing predictive models in both cropland and grassland sites but contributed more to predictions in cropland soils. Profile and planform curvature were significant terms in the regression model for both cropland and grassland soils. Additionally, percent slope was also significant in models for cropland soils. Overall, regression models were able to explain 90% and 73% of variability in SOC stocks observed in grassland and cropland sites, respectively. Soil profile 137Cs inventories were correlated with SOC stocks in both land cover types and show that soil movement can explain SOC variability in upland soils. Soil erosion or deposition rates (based on 137Cs inventories) ranged from 34.8 (erosion) to −70.1 (deposition) t ha−1 yr−1 in cropland sites and from 11.7 to −17.2 t ha−1 yr−1in grassland sites. Results from this study showed that soil redistribution can result in burial of eroded OC-rich surface soil in depositional locations characterized by low slopes and concave curvature in agricultural fields. [ABSTRACT FROM AUTHOR]

[Display omitted] • Thick clay-silty Luvisols in the bottom of dolines have high SOC storage capacity. • Past agricultural land-use presents long-term impact on SOC stock in dolines. • Succession plots in dolines show the highest SOC storage capacity (130 t/ha). • Soil organic carbon stock in dolines was double the amount on the levelled plateau. The soil organic carbon (SOC) was determined in soils of enclosed karst depressions (dolines) (NW Dinaric Mts.) to define their potential for organic carbon sequestration. SOC was measured in the forest, succession (scrubland), and grassland plots at the bottom of dolines at four depths (0–40 cm) and for 40 cm soil layer SOC stock was calculated. We demonstrated that the prevailing fine soil fractions, the C/N ratio and soil thickness play a positive role in the storage capacity of SOC in dolines regardless land use type. Grasslands have the lowest SOC storage capacity (106 t/ha/40 cm), while the highest SOC storage capacity is in succession plots (130 t/ha/40 cm). The last are covered by shrub communities dominated by Prunus spinosa , forming dense communities, and are typical of abandoned croplands or meadows that have been impacted by high levels of nutrients during cultivation phase. At this stage, there is no additional nutrient input in studied plots, which lowers the nutrient content and increases the C/N ratio. C/N ratio is the highest in the forest, where SOC stock capacity is 116 t/ha/40 cm. Given the trend towards the abandonment of agricultural land at Kras Plateau (SW Slovenia), we can expect more overgrowth of dolines, and thus an increase in carbon stocks and stabilization of organic carbon in forest soils. In contrary, we noticed the alarming decrease in grasslands and increase in urban land. The SOC storage in 2020 was for 12,538 t/ha/40 cm lower than in 2002. Although grasslands showed the lowest SOC storage, their contribution to total SOC storage in dolines is very important. Since there is a lack of studies on carbon stocks in doline soils, our research is of great importance and a novelty and gives an important background for further research on SOC stock in karst landscapes worldwide. [ABSTRACT FROM AUTHOR]

• Stability of SOC fractions differed among the forest types. • SOC stock was highest in a temperate forest (132.7 Mg C ha−1). • Active and passive carbon pool was highest in temperate and Quercus forests, respectively. • Conversion of natural forests to bamboo and jhum land reduced SOC stock. • Quercus forest plays a significant role in long-term carbon sequestration. Forests are among the largest terrestrial carbon pools that are most vulnerable to land use and land cover change (LULC). Therefore, it is essential to manage forest ecosystems to enhance soil organic carbon (SOC) pools and soil functionality. The present study was carried out to analyze C stability and change in SOC stock under different forest types in the eastern Himalayan region of India. Topsoil (0–15 and 15–30 cm) samples from six dominant forests i. e. tropical wet evergreen, montane subtropical, temperate, Quercus , bamboo, and shifting cultivation (Jhum) lands were collected and analyzed for selected soil properties and SOC stock. Active (very labile + labile), slow (less labile), and passive (non-labile) C fractions were also analyzed to determine the stability of the SOC pool under the LULC scenario. Results show that the percentage contribution of active C to total organic carbon in topsoil was highest in a temperate forest (74.1%) while lowest in a bamboo forest (48.1%). Unlike, slow C (18.4%) and passive C (26.6%) were highest in Quercus forest. Pearson correlation analysis shows significant positive relation of active and slow C pool with SOC and total nitrogen concentration. The estimates of SOC stock (0–30 cm) were significantly higher in temperate forests (132.7 Mg C ha−1). However, the conversion of natural forests to bamboo forest and jhum land reduced SOC stock by 29% and 68%, respectively. C lability index shows higher labile C in jhum land while recalcitrancy index was highest in a bamboo forest. Our study concluded that LULC change significantly altered the stability and stock of SOC in natural forests. Owing to a higher percentage of slow and passive C pools, Quercus forests play a major role in C sink management. [ABSTRACT FROM AUTHOR]

• Litter and tree roots modify the proportion of soil aggregate fractions. • Extensive agriculture implies similar soil carbon storage than agroforestry. • Agroforestry increases the carbon associated with the small soil aggregate fractions. The land use sector currently represents ∼25% of the global greenhouse gas emissions, thus this human activity is having a huge impact on climate change. Semi-arid climate areas, which are widely distributed, are particularly influenced by such climate change. In these areas, land use changes have transformed the entire landscape and increased the greenhouse gas emissions. However, in semi-arid climate areas, the information on the effect of climate change is scarce and usually centred on one single type of land use. For the land uses (forest, agricultural and agroforestry) traditionally found in the semi-arid area in South Portugal, this study aimed to evaluate (i) the soil chemical (pH) and physical properties (bulk density and percentage of different soil aggregate fractions: 250–2000; 53–250 and <53 μm) and (ii) the carbon (C) storage in whole soil and each soil aggregate fraction in land with over 100 years of the same use. The results show that after >100 years with the same land use, C storage in the whole soil was similar in the plots with extensive agriculture based on the agroecology principles to that in the agroforestry plots. However, the concentration and storage of C in the microaggregates (53–250 μm) and the silt + clay soil fraction (<53 μm) were generally higher for the forest and agroforestry land uses than for the agricultural land use due to the tree effect. This C associated with the smallest soil fractions is very stable and is retained in the soil in the long term. In this context, agroforestry systems improve the soil C storage in the long term at the same time that agricultural production is allowed compared to the traditional forest systems. Therefore, the establishment and maintenance of agroforestry systems in the semi-arid climate areas is a sustainable land use for climate change mitigation. [ABSTRACT FROM AUTHOR]

• Evaluation of different land use on SOC stock under climate change scenarios. • Both decreases and increases of SOC stocks would be possible in the future. • Under high emission scenario SOC stock increases to 6.23 million tons in cashew LUS. • RothC Model indicated cashew plantations as the most prominent sink of SOC storage. • Promotion of agroforestry systems are imperative to improve SOC storage. Soil organic carbon (SOC) is one of the significant soil components influencing soil functions and soil processes. However, little is known about the impact of land-use change on SOC dynamics on coastal agroecosystems. We, therefore, simulated the impact of land use on SOC stock using RothC model under different climate change scenarios. In the present study, natural forest and pasture lands are the native land uses, while cashew, arecanut, and coconut plantations were established about 70–80 years ago from the natural forest. Measured SOC stocks were significantly higher in cashew and forest land uses (109.5 and 88.6 t C/ha) and much lower in coconut, arecanut and pasture lands (64.1–71.0 t C/ha). The study showed that under projected climate change conditions in Goa state and depending on emission scenarios, both decreases and increases of SOC stocks would be possible. By the end of the century, SOC stock in cashew would decrease by 4.3 t C/ha (RCP 4.5) and increase by 2.4 t C/ha (RCP 8.5), in coconut the SOC change was negligible (0.2 t C/ha) in RCP 4.5 while increased by 3.2 t C/ha in RCP 8.5. Arecanut, pasture and forest land uses showed a marked SOC decrease in RCP 4.5 (ranging from 5.2 to 5.4 t C/ha) and negligible positive (0.6–0.7 t C/ha) or negative (0.6 t C/ha) changes in RCP 8.5. Overall, the model indicated cashew plantations as the most prominent sink of SOC storage, while coconut and pasture are not viable sinks of SOC in the study area. We suggest promoting cashew, arecanut, and coconut land use system integrated with tree components and pasture to improve the SOC storage and other ecosystem services in the coastal agroecosystem. [ABSTRACT FROM AUTHOR]

• Driving factors of SOC and total N were explored in 28 lucerne fields. • The SOC and total N were mainly explained by soil resources. • Soil P, moisture, and altitude were the key factors affecting SOC and total N. • Plant species diversity positively affected SOC and total N contents. • A strong interaction effect was observed among topography, vegetation and soil on SOC. Lucerne (Medicago sativa L.) is one of the most successfully introduced species for revegetation on the Loess Plateau of China and provides important ecosystem services. However, the driving mechanism of soil organic carbon (SOC) and total nitrogen (TN) in lucerne grasslands remains unclear. This study explored the controlling factors of SOC and TN in lucerne grasslands in the semiarid Loess Plateau. A total of 112 quadrats were employed in 28 lucerne fields. Vegetation characteristics, topographic factors, and soil properties at a 0–20 cm depth were measured in each quadrat. The SOC and TN contents increased with altitude and showed positive correlations with species richness, aboveground biomass of native plants, soil moisture, soil inorganic nitrogen, total soil phosphorus (P), and C:P and N:P ratios. Variations in SOC and TN contents were mainly attributed to soil resources, followed by the interaction of topography, vegetation and soil. Soil P, soil moisture, altitude, and native plant species were the main factors controlling SOC and TN contents in these lucerne grasslands. Results suggest that specific abiotic (soil P and moisture) and biotic (plant species diversity) factors controlled SOC and TN in semiarid lucerne grasslands. These factors should be included in SOC and TN evaluation models to predict the future terrestrial ecosystem carbon and nitrogen dynamics. [ABSTRACT FROM AUTHOR]

• Landscape-scale spatial variability of SOC in a temperate grassland was analyzed. • SOC presents strong and moderate spatial autocorrelation at two layers respectively. • Topography and land use have independent and combined influences on SOC. • Wind erosion and deposition both can alter SOC and increase its spatial variability. • The influence of wind erosion on SOC should be considered in carbon accounting. Understanding the spatial variability of soil organic carbon (SOC) and its main influencing factors is crucial for sustainable land use management and climate change mitigation. Existing studies mostly focus on the influence of environmental factors on the spatial variability of SOC, while little attention has been paid to the effects of wind erosion which has important influences in arid and semi-arid landscapes. In this study, spatial variability of SOC content at landscape scale and its main influencing factors were analysed at 0–1 cm and 1–6 cm in a typical temperate grassland. Results show that SOC content ranges from 0.45% to 4.11% and is higher at 0–1 cm. SOC presents strong and moderate spatial autocorrelation at 0–1 cm and 1–6 cm, respectively. SOC is high in part of the hilly area, and low in the west plain and southeast undulation. Elevation and vegetation coverage have significantly positive effects on SOC. SOC varies with land uses with the order that arable land (AL) < heavily grazed grassland (HG) < moderately grazed grassland (MG) < lightly grazed grassland (LG) < ungrazed grassland (UG) at 0–1 cm and AL < HG < MG < UG < LG at 1–6 cm. Under the same land use, SOC is generally the highest in the flatland at both layers and lowest in the leeward slope at 0–1 cm and the windward slope at 1–6 cm, respectively. Wind erosion and deposition can both alter SOC content and increase its spatial variability. SOC is high in areas without wind erosion and deposition and decreases with erosion and deposition rates due to the selective erosion and remote region sourced deposition materials which generally have low SOC. Such effects have important influence on land productivity, global carbon cycle and climate change, and it could not be neglected in carbon accounting. [ABSTRACT FROM AUTHOR]

• Land-use conversion was conducted to assess its effect on the changes of soil 13C. • Significant changes in δ13C were observed at the 0–10 cm depth after conversion. • SOC stock was largely increased in the 20–40 cm layer for grassland and forest. • New SOC was formed greater in grassland than in forest above 60 cm soil depth. Soil organic carbon (SOC) content and its 13C natural abundance along soil profile are sensitive to the changes of land use since these changes alter external carbon (C) inputs and belowground C turnover processes. A study was conducted to investigate how the conversion of cropland to forest, grassland or bare land (no vegetation) affect the distribution of SOC and its 13C values in 200-cm soil profiles. After 28 years of land conversion, the cropland that was remained as cropland (treated as control) had a significantly higher δ13C value than the bare land, grassland or forest at the top 10 cm soil depth. Regardless of the land use type, the mean soil 13C values in the subsurface soil layers depleted and δ13C signature decreased by 1%−5% compared with the top 10 cm soil layer, while the corresponded SOC content decreased by 3.5% to 91.2% as soil depth went down deeper. The SOC stock in the 0–200 cm profile was 16% and 12% higher in the grassland and forest, respectively, than in the control. The conservation of cropland to grassland and forest largely increased the SOC stock in the 20–40 cm soil layer compared with the control. The newly formed SOC was higher in the grassland than in the forest, and accounted for 15.4% and 9.7% of the SOC stock in the soil depth of 0–60 cm in the grassland and forest, respectively. Soil δ13C values and SOC contents were negatively correlated with pH and clay content, while they were positively correlated with nitrogen and C/N ratio along the soil profile. We infer that the conversion of cropland to forest or grassland is a beneficial practice for SOC storage, especially in the 0–60 cm depth. Such conversion has little impact on the SOC turnovers in deep soil layers during the study period. [ABSTRACT FROM AUTHOR]