Detecting changes in forest soil carbon stocks is critical for compiling national carbon budgets, yet remains challenging due to high spatial variability and relatively small temporal changes. Here, we use data from Canada's National Forest Inventory (NFI), which includes repeated measurements of organic and mineral soil horizons across 532 plots. We quantified within- and between-plot variability in soil carbon properties, assessed minimum detectable differences (MDD), and explored design improvements through simulations. Spatial variation in soil carbon stocks was substantial: coefficients of variation were ~40% for mineral and ~70% for organic horizons, with within-plot comparable to between-plot variability. Consequently, MDDs were also high, at ~4.1 and 4.6 Mg ha-1 10 year-1 for the surface mineral and organic horizons, respectively. This implies that only large, widespread changes would be detectable with the current data. Simulations showed that increasing the number of remeasurement plots to ~700 with four subsamples per plot could reduce MDD to be on par with the current estimate of soil carbon change. Grouping plots by ecozone provided inconsistent benefits at the national level because of ecozones with high spatial heterogeneity. The data also had patterns consistent with the statistical phenomenon of regression to the mean, which implies that any change in carbon stock may be a statistical artifact. Indeed, soil carbon stocks appeared to grow by 2.3 Mg C ha-1 10 year-1 during the first remeasurement interval, while a small number of second remeasurement interval data showed a completely unrelated pattern supporting the inference that this first interval change was a statistical artifact. Overall, our analysis of the NFI data suggests that its design characteristics of sampling multiple microplots per main plot and collecting longitudinal data per microplot are critical to providing robust estimates of soil carbon stock changes that can be used in national greenhouse gas inventories.

Understanding the coordinated changes in soil carbon and nitrogen is essential for evaluating ecosystem responses to environmental change, particularly in ecologically fragile alpine regions such as the Qilian Mountains. In this study, the denitrification-decomposition (DNDC) model was used to assess the spatiotemporal dynamics of soil organic carbon density (SOCD) and total nitrogen density (STND) in the 0-30 cm soil layer from 1975 to 2024. The results revealed that SOCD and STND were higher in the northern and east-central grasslands and lower in the southwestern regions. Both stocks exhibited fluctuating but overall increasing trends, with notable increases aligned with major ecological protection policies in China. To better understand the coupling of soil carbon and nitrogen, we constructed a composite indicator called soil carbon and nitrogen density (SCND) using principal component analysis. This indicator captures the synergistic accumulation of organic carbon and total nitrogen driven by shared ecological processes and was further used to explore its associations with environmental factors, enabling an integrated assessment of soil carbon-nitrogen dynamics. The results revealed that elevation and soil bulk density were the main direct drivers of carbon and nitrogen accumulation, both of which exerted negative effects, whereas the other factors acted through indirect pathways. These findings underscore the importance of topography and soil structure in regulating carbon and nitrogen dynamics. It is recommended to plant deep-rooted grass species, limit heavy machinery, and maintain long-term ecological protection to prevent declines after initial gains from interventions. In addition, the carbon-to-nitrogen (C/N) ratio showed increasing spatial heterogeneity over time, with high values in the western and central regions, where nitrogen input can be enhanced by introducing legumes or applying organic fertilizers. In the northern and southeastern areas, grazing exclusion or low-intensity grazing is recommended to promote organic matter accumulation. Vertically, the C/N ratio decreased with soil depth, indicating strong carbon and nitrogen coupling within the soil profile. Overall, this study highlights the coordinated dynamics of soil carbon and nitrogen in the Qilian Mountain grasslands, providing valuable insights for the sustainable management and resilience improvement of grasslands in this region under changing environmental conditions.

Maintaining appropriate levels of carbon and nitrogen in soils is critical to the maintenance of productivity in agricultural systems. However, results vary from studies on the influence of land management, such as livestock grazing, on soil carbon and soil nitrogen. A large-scale study was implemented to quantify relationships between soil carbon, nitrogen, carbon:nitrogen ratio (C:N ratio), grazing regimes, and vegetation cover at sites on farms in south-eastern Australia, sampled in 2011 and 2022. Three grazing regimes were examined: total livestock exclusion, rotational grazing (limited duration grazing up to 45 days annually), and (continuous) set stocking rate grazing. Statistically modelled mean values for soil carbon (2011: 3%, 2022: 3.73%), nitrogen (2011: 0.21%, 2022: 0.34%), and C:N ratio (2011: 13.9, 2022: 14.3) were greater in 2022 than 2011. Soil carbon and nitrogen were greater in 2022 than 2011 in continuous grazing sites, with less pronounced time period differences in grazing exclusion and rotational sites. The C:N ratio was significantly greater in 2022 than 2011 in grazing exclusion sites (2011: 13.73, 2022: 14.58) and rotational grazing sites (2011: 13.87, 2022: 14.49), but less in 2022 (13.59) relative to 2011 in continuous grazing sites (14.31). There were inconsistent (sometimes positive, sometimes negative) empirical relationships between grazing regimes and vegetation measures as well as relationships between vegetation measures and soil carbon, soil nitrogen, and C:N ratio. Structural equation modelling (SEM) revealed limited evidence for soil carbon changes in response to vegetation attributes impacted by grazing regimes. Lower values of soil nitrogen and higher values for the C:N ratio at grazing exclusion sites were mediated by an increase in sapling abundance. SEM also identified an influence of rainfall on vegetation attributes, some of which were associated with soil properties.

Enhanced rock weathering is regarded as a promising carbon dioxide removal method because of its potential to sequester soil inorganic carbon (SIC). However, the influence of enhanced rock weathering on changes in soil organic carbon (SOC) content, fractions and stability remains poorly understood. A randomized block experiment design employing five basalt addition rates (0 (CK), 2.5, 5, 10 and 20 kg·m−2) and four replicates was designed to investigate the influences of basalt addition on SOC and SIC content and stocks, SOC fractions and SOC stability in subtropical cropland, where Zea mays L. and Brassica juncea (L.) Czern were annually rotated. Soil samples were collected from depths of 0–15 cm and 15–30 cm one year after the addition of basalt. The results showed that enhanced rock weathering increased the total carbon content and stock by increasing both the SOC and SIC in a one-year field experiment. Compared with CK, basalt addition rates of 2.5, 5, 10 and 20 kg·m−2 increased the SOC stock by 16%, 23%, 21% and 19%, respectively, and the SIC stock by 37%, 30%, 35% and 32%, respectively. The labile carbon fraction was the primary organic carbon fraction, which accounted for more than 40% of the total SOC content. Enhanced rock weathering altered the content of the very labile carbon fraction due to its high sensitivity to basalt addition, but had little effect on the stable carbon fraction content in a one-year field experiment. Compared with CK, basalt addition increased the very labile carbon fraction content by 12% and 46%, respectively, according to samples from depths of 0–15 cm and 15–30 cm. Under basalt addition rates of 2.5, 5, 10 and 20 kg·m−2, the SOC stability index was 26%, 21%, 17% and 20%, respectively, lower than that under the 0-addition rate in a one-year field experiment, which was 1.63, indicating that enhanced rock weathering reduced the SOC stability. Our findings indicated that enhanced rock weathering increased soil carbon (both of SOC and SIC) sequestration, but reduced the SOC stability in a one-year field experiment in subtropical croplands. These observed trends in changes in soil carbon will be further tested and evaluated as the experiment continues in the future.

Root exudation, the export of soluble carbon compounds from living plant roots into soil, is an important pathway for soil carbon formation, but high rates of exudation can also induce rapid soil organic matter decomposition – a phenomenon known as the priming effect. Long-term soil warming associated with climate change could alter exudation rates and impact soil microbes by changing soil carbon chemistry. We hypothesized that warming-induced changes to exudation rate combined with direct effects of long-term warming on soil microbial communities would regulate the microbial priming effect. We tested this hypothesis with an artificial root exudate experiment using intact soil cores from a long-term soil warming experiment in a temperate forest. We found that chronic soil warming did not alter soil carbon formation from exudates, but did reduce the exudate-induced priming effect; exudation caused greater soil carbon loss in unwarmed than warmed soils. We used DNA stable isotope probing with 16S ribosomal RNA gene and shotgun metagenomic sequencing to determine whether long-term warming affected which microbes consume 13carbon-labeled artificial exudates. We found significant differences in bacterial community composition and relative gene abundances of 13carbon-enriched compared to natural abundance DNA. Both soil bacterial community composition and specific enzyme-coding gene families were strongly correlated with soil carbon priming in unwarmed treatments, but these effects were absent in warmed treatments. Our results suggest that the root exudate-induced priming effect is mediated by microbial biomass, community structure, and gene abundance, and that chronic warming reduces the priming effect by altering these microbial variables.

Changes in soil carbon， nitrogen， and phosphorus contents and their stoichiometric ratios play a crucial regulatory role in biogeochemical cycles and ecosystem functions. However， the response of soil carbon， nitrogen， and phosphorus stoichiometry to long-term nitrogen deposition， particularly the contrasting patterns between rhizosphere and bulk soils， remains insufficiently understood. Based on this， a ten-year field experiment was conducted in Metasequoia glyptostroboides plantations at Dongtai Forest Farm in Yancheng， Jiangsu Province， with five nitrogen addition gradients： N0 [0 kg·（hm2·a）-1]， N56 [56 kg·（hm2·a）-1]， N168 [168 kg·（hm2·a）-1]， N280 [280 kg·（hm2·a）-1]， and N336 [336 kg·（hm2·a）-1]. The basic physical and chemical properties， nutrient stoichiometric characteristics， enzyme activity， and microbial biomass of both rhizosphere and bulk soils were measured. The results indicated： ① Compared to that in N0， the overall carbon to nitrogen ratio in rhizosphere and bulk soils under all nitrogen addition treatments decreased significantly by 29.0% and 13.1%， respectively. In the N336 treatment， total nitrogen content and nitrogen to phosphorus ratio in rhizosphere soil significantly increased by 25.4% and 28.4%， respectively. The responses of soil organic carbon and total phosphorus contents and the carbon to phosphorus ratio to nitrogen addition were not significant across all treatments and in each individual treatment. ② The response directions of carbon， nitrogen， and phosphorus stoichiometric characteristics in rhizosphere and bulk soils to nitrogen addition were relatively consistent， but the response intensity in rhizosphere soil was greater. ③ Significant positive correlations were found among the organic carbon， total nitrogen， and total phosphorus contents in bulk soil， whereas only organic carbon and total nitrogen contents showed significant positive correlation in rhizosphere soil. Organic carbon content showed a significant positive correlation with stoichiometric ratios in both rhizosphere and bulk soils. ④ Microbial biomass and enzyme activity predominantly influenced the carbon， nitrogen， and phosphorus stoichiometric characteristics in bulk soil， whereas chemical properties such as pH， nitrate nitrogen， and available phosphorus contents were the primary regulators of these characteristics in rhizosphere soil. Overall， the responses of carbon， nitrogen， and phosphorus stoichiometric characteristics in rhizosphere and bulk soils to long-term nitrogen addition were relatively consistent but were regulated to varying degrees by soil chemical and microbial properties. This study deepens our understanding of the mechanisms and response patterns of rhizosphere and bulk soil carbon and nutrients to environmental changes， offering valuable scientific insights for advancing biogeochemical cycling models.

ABSTRACT Miscanthus is a particularly promising lignocellulosic biomass as it can also grow under marginal conditions and can be used for a wide range of products including energy and material applications. The latter, including applications in the construction, textile, chemical, or agricultural sector, is becoming increasingly relevant today. In general, it is hypothesised that biobased products are advantageous in terms of their greenhouse gas (GHG) performance when compared to conventional—in particular fossil—alternatives. To investigate this, the life cycle assessment methodology is typically applied. However, assessments are subject to uncertainty and variability due to assumptions and methodological choices. Given the increasing interest in miscanthus‐derived material applications, this study aims to draw more general conclusions about their GHG performance and relative mitigation potential. This should support a better understanding of their contribution to climate change mitigation objectives and guide the selection of promising products or product groups. A systematic review of peer‐reviewed literature was conducted. In total, 20 studies reporting on 188 comparisons of the GHG performance of miscanthus‐derived and alternative products were assessed. Most comparisons indicated potential GHG mitigation through miscanthus‐derived products, with the majority ranging between 20% and 100% savings. Key parameters defining the relative performance include the selection of the reference product, consideration of soil carbon changes, changes in product and process design, as well as the incorporation of indirect Land Use Change (iLUC) impacts. Overall, we conclude that miscanthus‐derived material applications have the potential to contribute to GHG emission mitigation if iLUC effects are minimised. Given the limited availability of agricultural land, miscanthus‐derived products with high absolute GHG mitigation potential per unit of biomass used and long product lifetime are preferable. For future development, potential environmental trade‐offs need to be monitored.

The restoration of ecosystems is increasingly critical in the context of global environmental and ecological challenges. As the world faces the growing impacts of climate change and land degradation, restoring ecosystems to enhance their services-such as water regulation, carbon sequestration, and biodiversity-is paramount. This research topic explores the interrelations between geological attributes, soil properties, and vegetation in ecosystem restoration, focusing on how these interactions influence ecosystem services and contribute to sustainable development goals (SDGs). Specifically, SDG 6 (Clean Water and Sanitation), SDG 13 (Climate Action), and SDG 15 (Life on Land) are particularly relevant as they align with the goals of enhancing water management, mitigating climate change, and restoring terrestrial ecosystems. Through examining empirical research and integrating findings from diverse geomorphological conditions, the articles in this collection offer novel insights into enhancing ecosystem resilience and advancing ecosystem-based solutions for water and land management.Ecosystem restoration offers a pathway to address multiple environmental issues simultaneously, particularly in regions affected by overexploitation, desertification, and deforestation. By understanding how soil, geology, and vegetation interact, researchers can design more effective restoration strategies that improve ecosystem functions and contribute to climate adaptation and the achievement of SDGs. The studies included in this collection emphasize the need for interdisciplinary approaches that combine ecological, hydrological, and geological knowledge. They provide critical insights into how restoration practices can enhance ecosystem services, improve land and water management, and ultimately support the achievement of sustainable development goals in the face of global environmental stressors.Soil-plant interactions are fundamental to ecosystem restoration, as they influence nutrient cycling, water retention, and plant growth. Soil properties such as texture, organic matter content, and moisture availability directly impact vegetation health, which in turn affects ecosystem functions. These studies underscore the importance of soil-plant interactions in ecosystem restoration and their broader implications for land and water management.Advances in monitoring technology have revolutionized our ability to assess and manage ecosystems. Remote sensing, GIS, and hydrological modeling tools enable more precise tracking of vegetation dynamics, soil moisture, and overall ecosystem health. Yue et al. used advanced spatial analysis to measure the impact of photovoltaic panels on soil properties in desert ecosystems, providing critical data for ecological restoration efforts. Cheng et al. also utilized remote sensing technology to study the influence of vegetation characteristics and soil properties on ecosystem dynamics in tropical forests. These innovations not only improve our understanding of ecosystem processes but also enhance the effectiveness of restoration strategies.Biogeochemical processes are essential for understanding how ecosystems recover and enhance their ability to sequester carbon. This is particularly important in the context of climate change, as restored ecosystems can contribute to mitigating carbon emissions. Zhang et al. found that soil carbon and nitrogen changes due to soil particle redistribution in photovoltaic arrays influenced soil fertility and carbon sequestration potential. In a similar study, Zhang et al. investigated the role of vegetation restoration in improving soil organic carbon storage in degraded landscapes. These studies highlight the significant role of biogeochemical processes in carbon cycling and their potential for enhancing ecosystem services related to climate change mitigation.Effective water management is a critical aspect of ecosystem restoration, particularly in regions affected by droughts and water scarcity. Restoration practices that enhance water regulation, such as reforestation and wetland restoration, can help restore the hydrological cycle and mitigate the impacts of climate change. Ma et al. (2024) demonstrated that moderate grazing promotes plant diversity and increases grassland water retention in the Qinghai-Tibet Plateau, which is crucial for sustainable water management. Similarly, Ma et al. assessed the role of vegetation restoration in improving water yield in China's arid regions. Collectively, these studies underscore the importance of integrating ecosystem-based water management strategies in restoration efforts.The research presented in this special issue collection highlights the critical connections between soil, geology, and vegetation in the restoration of ecosystems and the enhancement of their services. From improving water retention and carbon sequestration to advancing ecosystem monitoring and management strategies, these research findings offer valuable insights into how ecological restoration can contribute to sustainable development goals. Restoration is a complex and multifaceted process, and a one-size-fits-all approach is unlikely to be effective. Ecosystem restoration requires a holistic approach that incorporates local geological, soil, and vegetation conditions, as well as socio-economic factors, to ensure long-term success. These studies reinforce the need for interdisciplinary strategies to tackle the diverse challenges of ecosystem restoration and to achieve lasting improvements in ecosystem services.

Does 46 years of conservation tillage and crop rotations change soil carbon and nitrogen distribution and storage?

Soil carbon changes are difficult to measure globally, and global models are poorly constrained. Here, we propose a framework to map annual changes in soil carbon and litter (SOCL) as the difference between the net land CO2 flux from atmospheric inversions and satellite-based maps of biomass changes. We show that SOCL accumulated globally at a rate of about 0.34 ± 0.30 ( ± 1 sigma) billion tonnes of carbon per year (PgC yr−1) during 2011-2020. The largest SOCL sink is found in boreal regions (0.93 ± 0.45 PgC yr−1 in total) particularly in undisturbed peatlands and managed forests. The largest losses occur in the dry tropics (−0.50 ± 0.47 PgC yr−1) and correspond with agricultural expansion from land use change, cropland management and grazing. By contrast, forests in the wet tropics act as a net soil carbon sink (0.32 ± 0.35 PgC yr−1). Our findings highlight the large mitigation opportunities in the dry tropics to restore agricultural soil carbon.

Conservation agriculture (CA) based zero-tillage system has gained prominence for its potential to improve soil health, enhance nutrient cycling, and increase carbon sequestration in soil. Knowledge about the changes in soil carbon and nitrogen dynamics under no-tillage and different cropping systems is necessary to assess the feasibility of adopting conservation agriculture to sustain soil health and productivity. This study compared conventional tillage (CT) and zero-tillage (ZT) systems, and three cropping systems (soybean-wheat, maize-wheat and maize-chickpea) on soil carbon and nitrogen dynamics. The experiment was established in 2010 on a Vertisol in Bhopal, India. After the completion of the 14th cycle of the experiment (2023-24), soil samples were collected from each plot and analysis processes were executed. The soil under ZT had found significantly higher concentrations of soil organic carbon (0.93%), total organic carbon (1.23%), very labile pool (0.55%), labile pool (0.19%), non-labile (0.36%) and total carbon (1.39%) than CT at 0-10 cm depth. Available nitrogen (229.83 kg ha1) and total nitrogen (0.133%) also had significantly higher in ZT than CT at surface soil. Tillage and cropping systems had no significant impact on soil inorganic carbon and mineral nitrogen (ammonium and nitrate nitrogen). Therefore, under Vertisols, 14 years of ZT practices are likely to improve organic carbon concentration and increase the availability of nitrogen in soil, allowing a positive trend for soil preservation and carbon sequestration in soil.

ABSTRACTThe release of fixed ammonium (NH4+) is likely related to the concentration of exchangeable NH4+ and is regulated by various microbial processes, which are affected by the changes in soil carbon (C) and nitrogen (N) sources that are caused by straw addition. This increases the need to clarify the dose effects of straw on the release of fixed NH4+ and the fate of fixed NH4+‐derived N. In this study, the fixed NH4+ pool of an Alfisol was labelled with 15N under chloroform fumigation, and then the labelled soil (fumigated) was mixed with untreated soil (unfumigated) and incubated for 288 days with four rates of straw addition: S0 (no straw), S4 (4 t ha−1), S8 (8 t ha−1), and S12 (12 t ha−1). The addition of a low amount of straw (4 t ha−1) promoted the release of labelled fixed NH4+, whereas greater amounts of straw (8 and 12 t ha−1) resulted in inhibition. By the end of incubation, 63% of the fixed NH4+‐derived N had been transformed into nitrate‐N in S0, whereas this percentage significantly decreased in straw treatments. The percentage of the fixed NH4+‐derived N that transformed into organic N increased from 23% to 61% with increasing straw addition. The soil total C content was the primary factor influencing the release of fixed NH4+ in S0, and nitrification was responsible for this in S4. For S8 and S12, microbial immobilisation, succeeding nitrification, became the dominant driving factor for fixed NH4+ release. These results indicated that there is a relay effect between soil C source, nitrification, and microbial immobilisation on fixed NH4+ release with increasing straw addition. These results are helpful for improving the understanding of the relay effect of factors that drive fixed NH4+ release in Alfisols with increasing straw addition and provide a basis for optimising the straw management.

ABSTRACTThe rapid expansion of rubber monocultures over the past two decades has degraded extensive areas of tropical rainforest, raising concerns about their restoration. A key factor influencing the recovery of these forests remains their microbially mediated biogeochemical cycling processes. Here, we investigated changes in soil carbon and nutrient concentration, the carbon (C), nitrogen (N), and phosphorus (P)‐acquiring soil extracellular enzyme activities and their stoichiometric ratios (reflecting microbial nutrient limitations) following forest restoration in rubber monocultures. Furthermore, we evaluated the effects of restoration strategies (natural regeneration and restoration plantings) and soil abiotic properties on enzyme activities and examined correlations between soil nutrient concentration and enzyme activities stoichiometric ratios. Our findings revealed that the enzyme activities in restored forests differed significantly from those in rubber monocultures, with higher or lower activities depending on the enzyme types and the restoration strategies. As restoration advanced, the enzyme C:N:P became relatively balanced, indicating an alleviation of microbial C‐ and N‐limitation. Both restoration strategies alleviated microbial C‐limitation to a similar extent, but restoration plantings showed a higher alleviation of microbial N‐limitation than natural regeneration. Soil pH emerged as the main factor influencing enzyme activities. The increase in soil total P concentration significantly decreased microbial C‐limitation but increased N‐limitation. Furthermore, the increase in soil C:P and N:P ratios significantly alleviated the microbial N‐limitation. Our findings highlight that converting monoculture rubber plantations back into tropical forests through natural regeneration and restoration plantings promotes positive changes in soil microbial activity, alleviates microbial nutrient limitations, and fosters a more balanced nutrient acquisition strategy. These results provide critical scientific support for ecological restoration efforts in tropical regions.

The thermal adaptation of the microbial community can potentially mitigate the positive feedback between soil carbon loss and climate change. However, the mechanistic basis of this process remains unclear, particularly the link between functional genes and microbial metabolic physiology in regulating the thermal response of soil carbon decomposition. While most experimental warming studies have examined elevated mean temperatures, the magnitude of temperature fluctuations is also increasing under climate change and may impose distinct ecological effects on microbial processes. This knowledge gap likely underlies current uncertainties in predicting microbial contributions to soil carbon-climate feedbacks. Here, we conducted a 200-day incubation with soil samples from six subtropical forests spanning a 2000 km transect in China under two climate change scenarios: elevated mean temperature and increased temperature fluctuation. We found that the stronger functional gene resistance governed the thermal adaptation of the maximum potential reaction rate (Vmax, an indicator of microbial decomposition of soil carbon) of three carbon-degrading enzymes under increased temperature fluctuation, while the enhancing response of Vmax under elevated mean temperature was driven by the attenuated microbial community resistance. These findings provide a mechanistic basis for predicting microbially mediated feedbacks between soil carbon and temperature change via microbial physiology, offering empirical evidence for integrating microbial processes into Earth system models under climate warming.

Forestation (afforestation and reforestation) could mitigate climate change by sequestering carbon within biomass and soils. However, global mitigation from forestation remains uncertain owing to varying estimates of carbon sequestration rates (notably in soil) and land availability. In this study, we developed global maps of soil carbon change that reveal carbon gains and losses with forestation, primarily in the topsoil. Constraining land availability to avoid unintended albedo-induced warming and safeguard water and biodiversity (389 million hectares available for forestation globally) would sequester 39.9 petagrams of carbon by 2050, substantially below previous estimates. This estimate drops to 12.5 petagrams of carbon with land further limited to existing policy commitments (120 million hectares). Achieving greater mitigation requires expanding dedicated forestation areas and strengthening commitments from nations with considerable but untapped potential.

Understanding the detailed spatiotemporal variations in soil organic carbon (SOC) stocks is essential for assessing soil carbon sequestration potential. However, most existing studies predominantly focus on topsoil SOC stocks, leaving significant knowledge gaps regarding critical zones, depth-dependent variations, and key influencing factors associated with deeper SOC stock dynamics. This study adopted a comprehensive methodology that integrates random forest modeling, equal-area soil profile analysis, and space-for-time substitution to predict depth-specific SOC stock dynamics under climate warming in Northeast China’s forest ecosystems. By combining these techniques, the approach effectively addresses existing research limitations and provides robust projections of soil carbon changes across various depth intervals. The analysis utilized 63 comprehensive soil profiles and 12 environmental predictors encompassing climatic, topographic, biological, and soil property variables. The model’s predictive accuracy was assessed using 10-fold cross-validation with four evaluation metrics: MAE, RMSE, R2, and LCCC, ensuring comprehensive performance evaluation. Validation results demonstrated the model’s robust predictive capability across all soil layers, achieving high accuracy with minimized MAE and RMSE values while maintaining elevated R2 and LCCC scores. Three-dimensional spatial projections revealed distinct SOC distribution patterns, with higher stocks concentrated in central regions and lower stocks prevalent in northern areas. Under simulated warming conditions (1.5 °C, 2 °C, and 4 °C increases), both topsoil (0–30 cm) and deep-layer (100 cm) SOC stocks exhibited consistent declining trends, with the most pronounced reductions observed under the 4 °C warming scenario. Additionally, the study identified mean annual temperature (MAT) and normalized difference vegetation index (NDVI) as dominant environmental drivers controlling three-dimensional SOC spatial variability. These findings underscore the importance of depth-resolved SOC stock assessments and suggest that precise three-dimensional mapping of SOC distribution under various climate change projections can inform more effective land management strategies, ultimately enhancing regional soil carbon storage capacity in forest ecosystems.

There is an inevitable relationship between the size of soil particles and the distribution of organic matter. The soil texture in desert photovoltaic areas is poor, with variations in soil particle size and organic matter. This study explores the heterogeneity of soil particle size and organic matter distribution at different zonal scales, aiming to clarify the impact of photovoltaic array construction on microtopography and, consequently, on these indicators. This will facilitate precise vegetation restoration based on the distribution of nutrients within the region. Baced on the Kubuqi Desert photovoltaic area as the research area, the soil particle size in the 0–30 cm soil layer and the distribution of soil organic matter in the main particle size range (<250 μm, <500 μm) in this area were analyzed. Fine sand (particle size 100–250 μm) was the main component of the soil; the carbon and nitrogen stocks in the upper 0–30 cm of soil diminished linearly with escalating wind speed gradient, from 70.76 Mg C ha−1 to 53.82 Mg C ha−1 and from 13.96 Mg N ha−1 to 8.12 Mg N ha−1. The total carbon and nitrogen levels in the two soil particle sizes, together with their contribution to total soil organic carbon, diminished as the wind speed gradient intensified, with the reduction in organic carbon content becoming stronger. The organic carbon content of soil particles <250 μm accounted for 63.7%–98.6% of the total soil organic carbon, while that of particles 250μm–500 μm only accounted for 3.32%–33.34%. SOC was significantly higher in the 0–5 cm layer than in the 5–30 cm layer in all areas of the photovoltaic array. Wind causes changes in sand particle transport in PV arrays, and may also alter the microclimate environment leading to differences in soil decomposition cycling processes, which can exhibit uneven organic carbon and nitrogen distribution between particles. Our research demonstrates the internal distribution of soil carbon and nitrogen reserves in each region of the photovoltaic array, establishing a robust foundation for subsequent vegetation restoration and plant species selection in each region, thereby implementing the “photovoltaic + ecological” governance model.

In recent years， the rapid socio-economic development and the improvement of people's diets have driven the conversion of paddy soil to upland crop cultivation， leading to changes in soil water content， carbon and nitrogen availability， and the intensity of greenhouse gas emission. Therefore， it is crucial to study the effects of changes in soil water content and carbon and nitrogen availability on greenhouse gas CH4 and CO2 emissions and identify the key controlling factors upon rice paddy conversion into upland field， especially during the initial stage of conversion. Soil samples used in the present study were collected from a long-term rice paddy field and an adjacent upland field previously converted from rice paddy. The paddy soil was set into submerged （water to soil ratio of 2∶1） and from submerged to a slowly draining treatment （water to soil ratio of 2∶1 slowly decreased to 70% field water capacity and then remained stable） and compared with the upland soil （soil water content remained at 70% field water capacity）. Under each water gradient， the soil was supplied with labile C and N to change substrate availability： ① control （no substrate addition）， ② C addition （glucose）， ③ N addition （NH4Cl）， and ④ C and N additions （glucose+NH4Cl）. CH4 and CO2 emissions and soil biochemical properties were measured regularly during the incubation period so as to investigate the effects of soil water content， carbon and nitrogen availability， and their interaction on CH4 and CO2 emissions in paddy soil. The changes in contents of soil microbial biomass carbon （ΔMBC）， dissolved organic carbon （ΔDOC）， and soil mineral N （ΔMineral-N， containing ΔNH4+-N and ΔNO3--N） over the incubation period were calculated by subtracting the initial values from the final values at the end of the incubation period. The results showed that as compared to the submerged condition， the drainage of submerged paddy soil significantly reduced CH4 emission by 95% on average and increased CO2 emission by 46% on average. The cumulative emissions of CH4 and CO2 were significantly higher in drained paddy soil （1.36 mg·kg-1 and 584.13 mg·kg-1 for CH4 and CO2， respectively） relative to those in upland soil （0.01 mg·kg-1 and 407.70 mg·kg-1）. CH4 emissions from the submerged paddy soil significantly increased by 40% after carbon addition and decreased by 63% after nitrogen addition. The simultaneous additions of carbon and nitrogen had little effect on the CH4 emissions from submerged paddy soil. CH4 emissions from the drained paddy soil increased significantly by 48% after carbon addition， but there was no significant difference among other substrate addition treatments. In upland soil， the additions of carbon and nitrogen had no significant effect on CH4 emissions but significantly increased CO2 emissions by 45%-109%. The additions of carbon and nitrogen had little effect on CO2 emissions in submerged paddy soil. The concurrent addition of carbon and nitrogen significantly increased CO2 emissions by 36% in drained paddy soil. The interactions between soil water change and N addition had no significant effect on CH4 emissions， while the interactions between soil water change and C and CN additions significantly affected CH4 emissions. No significant interactions between soil water change and C and N availability were observed for CO2 emissions. The conversion of submerged paddy to upland soil decreased soil pH， DOC， MBC， and NH4+-N contents but increased NO3--N content. The additions of carbon and nitrogen significantly affected soil biochemical properties. The results of correlation analysis showed that CH4 emissions were significantly positively correlated with soil pH， ΔMBC， and ΔNH4+-N and negatively correlated with ΔNO3--N among treatments. Conversely， CO2 emissions were significantly positively correlated with ΔNO3--N but negatively correlated with pH， ΔDOC， ΔMBC， and ΔNH4+-N. The changes of soil chemical and biological properties induced by soil water change and carbon and nitrogen availability were the main factors influencing CH4 and CO2 emissions from paddy soil. In summary， changes in soil water content and carbon and nitrogen availability affect CH4 and CO2 emissions by altering soil biochemical properties. Drainage of paddy soil is an effective measure to reduce CH4 emissions， but the risk of increased CO2 emissions during the short-term period upon drainage should be considered. Therefore， when developing strategies for rice paddy management， it is crucial to consider the combined effects of water and C and N management so as to achieve effective greenhouse gas mitigation and green and sustainable agricultural production.

ABSTRACT Soil organic matter (SOM) is a key soil property used to predict the impacts of land-use changes as well as to indicate soil health status. The vegetative indices (VI) derived from remote-sensing data, such as soil adjusted vegetation index (SAVI), normalized difference vegetation index (NDVI) and normalized difference moisture index (NDMI) are important indices reflecting crop growth and biomass. They can be related to soil organic carbon changes in large-scale environments. However, there is little information in the literature about the relationship between VI and soil carbon changes over the transition of different farming practices from degraded grassland to an agroforestry system. This study aimed to determine the relationship between soil C stocks and VI over the transition of degraded grassland (DGL) to agroforestry (AgrfS) in the Brazilian Cerrado. Soil organic stocks, NDVI, SAVI and NDMI were measured from 2011 to 2015, when the area passed from a low-productivity grassland, followed by a crop-pasture intercropping system and an agroforestry system. The transitional phases from degraded grassland to agroforestry system promoted surprisingly large gains in soil carbon stocks, ranging from 41.7 Mg C ha−1 in DGL to 68.4 Mg C ha−1 in AgrfS. Similar to soil carbon stocks, the mean VI values increased over the years from DGL to AgrfS, indicating the importance of vegetation indices to predict soil carbon stocks changes over the restoration of degraded grasslands.

The US Dairy Industry has pledged to achieve net zero greenhouse gas emissions (GHG) by 2050, but reliance on corn (Zea mays L.) silage as a primary forage source undermines progress toward this goal. Soils managed for corn silage production are a significant source of carbon (C) emissions to the atmosphere, with the soil C losses ranging from 3.7 to 7.0 Mg C ha-1 yr-1 (13.5 to 25.6 Mg CO2 ha-1 yr-1) reported in the literature. However, biogenic emissions from soil C loss are not typically represented within C-footprints or life cycle inventories. Using an example dairy farm, we demonstrate that including emissions associated with soil C losses under dairy forage production can increase the C-footprint of milk nearly 2-fold. We suggest that this approach represents a more accurate estimate of the emissions impact of milk production, and that gains in the GHG efficiency of milk have come, in part, at the expense of soil C where forage rotations are predominated by silage corn. The C balance of forage production systems can likely be improved with advanced manure management technologies and application strategies that return more manurial C to the soil while minimizing N and P loading. However, we argue that more extensive changes to forage cropping systems will also be required. Expanding the role of perennials and winter annual crops in forage rotations; breeding forages with greater yield, persistence, and deeper more extensive root systems; and additional creative solutions to retain more plant-derived C in soils are necessary to balance soil C budgets and achieve net-zero emissions targets.