Soil Carbon Emissions Research Articles

Factors of soil CO2 emission in boreal forests: evidence from Central Siberia

Soils of boreal forests are crucial carbon reserves. The response of soil carbon emission to climate change significantly affects the concentration of carbon dioxide in the atmosphere. Soil carbon emission models frequently show a nonlinear response to temperature, but soil moisture is an important limiting factor, often overlooked in energy limited ecosystems. We suggest a statistical model of soil CO2 emission constrained by soil moisture and temperature for different ecosystems in the boreal zone. We tested this modelling strategy using direct measurements of seasonal soil CO2 emission near the research observatory ZOTTO near the Bor settlement, Central Siberia, Russia, in 2012-2017. Soil moisture explained a significant amount of variability of soil emission: the adjusted R2 was twice higher than in the baseline model. Although the temperature-only model describes the annual variability of carbon dioxide emissions quite well, the addition of moisture measurement significantly refines the quality of prediction of the seasonal component dynamics. Models including both temperature and soil moisture could serve as a promising tool to analyze the carbon cycle in boreal forest ecosystems.

Impacts of Saline Water Irrigation on Soil Respiration from Cotton Fields in the North China Plain

Saline water irrigation has been widely used for crop production where agriculture is short of freshwater. However, information about the response of soil respiration to saline water irrigation is limited. To identify the effect of saline water irrigation on soil respiration, the experiment based on long-term saline water irrigation cotton fields (since 2006) was conducted in the Heilonggang area in 2021. Five salinity levels in irrigation water were tested (3.4 [S1], 7.1 [S2], 10.6 [S3], 14.1 [S4], and 17.7 dS m−1 [S5]), and deep ground water (1.3 dS m−1) was used as the control (CK). After 15 years of saline water irrigation, we monitored soil physicochemical properties and soil respiration. In addition, we developed a structural equation model of the relationship between them. The results demonstrated that saline water irrigation significantly reduced soil water-stable aggregate content and porosity by 4.42–45.33% and 6.52–14.10%, respectively, and attenuated soil cellulase, α-glucosidase, and alkaline phosphatase activity. Soil respiration under saline water irrigation was significantly reduced by 5.28–33.08%. Moreover, saline water irrigation with salinity below 10.6 dS m−1 had no significant effect on cotton yield. Moreover, soil salinity (62%), water-stable aggregate content (46%), and soil porosity (25%) had significant effects on soil respiration, and soil porosity had a significant positive effect on soil alkaline phosphatase activity according to the structural equation model. Overall, saline irrigation with salinity below 10.6 dS m−1 can alleviate water shortages and reduce soil carbon emissions without affecting cotton yield in the study area.

Trade-off between soil carbon emission and sequestration for winter wheat under reduced irrigation: The role of soil amendments

Underground water source in North China Plain (NCP) is limited and extensively explored for wheat irrigation, which has caused high carbon emission. Reduced irrigation strategies and soil amendments have been advocated for sustainable agricultural production. However, the interactive effects of irrigation schedule and soil amendment on direct and indirect greenhouse gas (GHG) emissions, soil organic carbon (SOC) sequestration and carbon footprint (CF) have rarely been systematically quantified. A two-year field study was conducted in wheat season under three irrigation schedules (W0: pre-sowing irrigation only, W1: pre-sowing + jointing irrigation, and W2: pre-sowing + jointing + anthesis irrigation) and three fertilization types (Fc: chemical fertilizer only, Fm: chemical fertilizer + manure, and Fb: chemical fertilizer + biochar). In the Fc treatments, direct emissions from soil N2O and CH4 significantly decreased from W2 or W1 to W0, but SOC also decreased from W2 to W1 or W0. Net GHG emissions (GHGnet) was 14.6% higher in W1 +Fc but 6.0% lower in W0 +Fc compared with W2 +Fc because of the difference in electricity use for irrigation. Notably, the CF in W1 +Fc and W0 +Fc was 40.9% and 63.8% higher than in W2 +Fc mainly due to yield loss. Compared with Fc, direct emissions averaged 63.1% higher under Fm coupled with increased soil nitrate content, microbial biomass carbon (MBC) and nitrogen (MBN). The SOC significantly decreased from W0, W1 to W2 under Fm. Under the identical irrigation level, SOC stocks were 40.0% and 53.9% higher in Fm than in Fc under W1 and W0, while no significant difference under W2. Relative to Fc treatments, under Fm, CF was 28.5% lower in W0 but 6.2% and 45.7% higher in W1 and W2. Compared with Fc, direct emissions averaged 7.7% lower under Fb due to smaller MBN and higher soil porosity under Fb. The CF was lower in Fb than in Fc resulting from SOC increase. Thus, manure and biochar amendment could decrease CF following reduced irrigation, although manure application increased the risk of C loss.

Restoration of agroecosystems with conservation agriculture for food security to achievesustainabledevelopment goals

AbstractCurrently, agroecosystems sustainability is mainly challenged by unsustainable agricultural practices that lead to land degradation and amplified climate change. About 25% of the World's total land area has deteriorated due to improper agricultural land management, resulting in ~24 billion tonnes of annual soil loss. Globally, soil erosion, mainly caused by high‐frequency tilling, crop residue removal or burning, poor pasture management, and inefficient crop rotations, is responsible for >40% of total land deterioration problems. Conservation agriculture (CA) seeks minimum soil disturbance, permanent soil cover, and crop rotation, which are indispensable for soil fertility restoration, carbon stabilization, increased soil biodiversity, and sustainable food production. In the last decades, the global annual adoption rate of CA was 7 M ha yr−1. CA‐based soil and crop management practices enhanced water productivity, soil organic carbon, crop productivity, and energy use efficiency by 18%–66%, 12%–93%, 3.8%–76.2%, and 8.9%–40.2%, respectively, over conventional practices under diverse agroecosystems in India. Hence, adopting CA can avert/minimize the problem of land degradation and food insecurity by improving crop productivity and decreasing soil erosion, energy use, and carbon emission, besides maintaining soil physicochemical and biological health. Moreover, CA can be a sustainable way to ensure global food demand, achieve sustainable development goals (SDGs), and restore soil health, and multiple agroecosystem services. This study aims to provide in‐depth insights into the role of CA in restoring agroecosystem services, attaining SDGs, and ensuring global food security.

Effects of Short-Term Nitrogen and Phosphorus Addition on Soil Respiration Components in a Subalpine Grassland of Qilian Mountains

In order to investigate the effects of short-term nitrogen and phosphorus addition on soil respiration and its components in a subalpine grassland located on the Qilian Mountains, a random block design of nitrogen[10 g·(m2·a)-1, N], phosphorus[5 g·(m2·a)-1, P], nitrogen and phosphorus addition[10 g·(m2·a)-1N and 5 g·(m2·a)-1P, NP], the control (CK), and complete control (CK') was conducted from June to August 2019, and total soil respiration and its component respiration rates were measured. The results showed that nitrogen addition reduced soil total respiration and heterotrophic respiration rates at a lower rate than P addition[-16.71% vs. -19.20%; -4.41% vs. -13.05%], but the rate of decrease in autotrophic respiration was higher than that of P addition (-25.03% vs. -23.36%); N and P mixed application had no significant effect on soil total respiration rate. The total soil respiration rate and its components were significantly exponentially correlated with soil temperature, and the temperature sensitivity of soil respiration rate was decreased by nitrogen addition (Q10:-5.64%-0.00%). P increased Q10 (3.38%-6.98%), and N and P reduced autotrophic respiration rate but increased heterotrophic respiration rate Q10 (16.86%) and decreased total soil respiration rate Q10 (-2.63%- -2.02%). Soil pH, soil total nitrogen, and root phosphorus content were significantly correlated with autotrophic respiration rate (P<0.05) but not with heterotrophic respiration rate, and root nitrogen content was significantly negatively correlated with heterotrophic respiration rate (P<0.05). In general, autotrophic respiration rate was more sensitive to N addition, whereas heterotrophic respiration rate was more sensitive to P addition. Both N and P addition significantly reduced soil total respiration rate, whereas N and P mixture did not significantly affect soil total respiration rate. These results can provide a scientific basis for the accurate assessment of soil carbon emission in subalpine grassland.

Flooding lowers the emissions of CO2 and CH4 during the freeze-thaw process in a lacustrine wetland

The frequency and strength of soil freeze–thaw alternation have been increasing with the aggravation of climate change, which will affect soil physicochemical properties and biological characteristics and in turn alter soil carbon (C) emissions. The emissions of carbon dioxide (CO2) and methane (CH4) are often influenced by the water level in wetland ecosystems. However, the effects of soil freeze–thaw alternation under different water levels on soil C emissions in wetland ecosystems are still not clear. We examined the impacts of soil freeze–thaw alternation under different water levels on the emission of CO2 and CH4 in a wetland dominated by Phragmites australis, and the soil microbial community structure and enzymatic activities were studied. The results showed that freeze–thaw treatments promoted soil carbon emissions, and flooding significantly lowered soil CO2 and CH4 emissions under freeze–thaw treatments. The soil water content (SWC), dissolved organic carbon (DOC), and the activities of β-N-acetyl-glucosaminidase (NAG), polyphenol oxidase (PPO), and peroxidase (PER) were the main predictors of soil carbon emissions under freeze–thaw treatments. Flooding played a direct role in carbon emissions during the freeze–thaw processes, and the interpretation rates of soil CO2 and CH4 emissions were 65% and 37%, respectively. The high-water level indicated fewer carbon emissions during the freeze–thaw period. Therefore, appropriately raising the water level is conducive to reducing carbon emissions from wetlands in areas of seasonal frost.

Effect of Biochar on the Stability of Soil Organic Carbon in the Context of Global Warming

Since the industrial revolution, the mean global temperature has increased by more than 0.6°C, and this has led to serious ecoenvironmental problems, such as melting ice sheets, retreating glaciers, species extinction and extreme weather-climate events, which have substantially affected human social life. The issue of how to reduce global warming has become a worldwide concern. Soil is one of the primary carbon emission sources, and maintaining the stability of soil organic carbon (SOC) plays a crucial part in reducing soil carbon emission. Soil-biochar has great potential as a natural carbon sequestration solution. Biochar produces positive/negative stimulation effects on soil organic carbon when applied to soil. In this review, the direct and indirect effects of biochar on the soil environment are described, with a focus on priming effects and influencing factors of biochar. In terms of direct effects, biochar and its surface dissolved organic carbon can directly replenish the organic carbon source required by the soil carbon cycle. In terms of indirect effects, biochar can influence SOC mineralization by affecting the species, number, and activity of microorganisms in soil. Soil properties, vegetation type, biochar raw material, and pyrolysis temperature as well as their aging effects are the key factors affecting soil-biochar carbon sequestration. This review will contribute to the understanding of the contribution of biochar to the reduction of soil emissions.

Soil microbial communities regulate the threshold effect of salinity stress on SOM decomposition in coastal salt marshes

Salinity stress is one of the critical environmental drivers of soil organic matter (SOM) decomposition in coastal ecosystems. Although the temperature sensitivity (Q10) of SOM decomposition has been widely applied in Earth system models to forecast carbon processes, the impact of salinity on SOM decomposition by restructuring microbial communities remains uncovered. Here, we conducted a microcosm experiment with soils collected from the coastal salt marsh in the Yellow River Estuary, which is subjected to strong dynamics of salinity due to both tidal flooding and drainage. By setting a gradient of salt solutions, soil salinity was adjusted to simulate salinity stress and soil carbon emission (CO2) rate was measured over the period. Results showed that as salinity increased, the estimated decomposition constants based on first-order kinetics gradually decreased at different temperatures. Below the 20‰ salinity treatments, which doubled the soil salinity, Q10 increased with increasing salinity; but higher salinity constrained the temperature-related response of SOM decomposition by inhibiting microbial growth and carbon metabolisms. Soil bacteria were more sensitive to salinity stress than fungi, which can be inferred from the response of microbial beta-diversity to changing salinity. Among them, the phylotypes assigned to Gammaproteobacteria and Bacilli showed higher salt tolerance, whereas taxa affiliated with Alphaproteobacteria and Bacteroidota were more easily inhibited by the salinity stress. Several fungal taxa belonging to Ascomycota had higher adaptability to the stress. As the substrate was consumed with the incubation, bacterial competition intensified, but the fungal co-occurrence pattern changed weakly during decomposition. Collectively, these findings revealed the threshold effect of salinity on SOM decomposition in coastal salt marshes and emphasized that salt stress plays a key role in carbon sequestration by regulating microbial keystone taxa, metabolisms, and interactions.

The Quantified and Major Influencing Factors on Spatial Distribution of Soil Organic Matter in Provincial-Scale Farmland—A Case Study of Shandong Province in Eastern China

Soil organic matter (SOM) is an important component of soil and plays an important role in improving the soil’s physical and chemical properties. Ascertaining the spatial distribution of soil organic matter and its main controlling factors in the context of provincial scale farming is of important guiding significance for soil carbon sequestration, emission reduction and sustainable utilization. Using 257 soil profiles from the second soil survey in Shandong Province, GIS, we applied geostatistical methods to study the spatial distribution characteristics of SOM in topsoil. In addition, correlation and regression analyses were used to explore the main controlling factors over the spatial variation of SOM. The results showed that the mean amount of SOM in Shandong province ranged from 1.20–74.90 g·kg−1, with a coefficient of variation of 73.52%, which is a medium level of variation. The distribution of SOM in the study area was patchy, with higher levels of organic matter in the central, eastern, and northern parts, and lower levels of organic matter in the south-west. The comprehensive explanatory ability of all factors reached 52.30%. Soil type and parent material were the main controlling factors for the spatial variability of SOM in the Shandong Province, followed by soil texture and land use type, with topography and climatic factors having relatively little influence.

Effects of Agricultural Waste Application on Soil Carbon Emission in Newly Cultivated Land

Cultivated land is an important resource to ensure food production and food security. However, the low degree of soil ripening, poor soil and lack of organic matter are common problems in newly cultivated land. Fertilization can effectively improve the physical properties of soil, improve soil nutrients and fertility, but long-term application of inorganic fertilizer will cause soil compaction or even degradation. Returning agricultural waste to the field can not only increase soil fertility and effectively improve soil structure, but also change soil carbon emissions. In this paper, the benefits of straw returning and livestock manure composting and their potential effects on soil carbon emissions were summarized to provide ideas for improving the fertility of new cultivated land.

Nitrogen fertilization rates mediate rhizosphere soil carbon emissions of continuous peanut monoculture by altering cellulose-specific microbess.

Crops influence both soil microbial communities and soil organic carbon (SOC) cycling through rhizosphere processes, yet their responses to nitrogen (N) fertilization have not been well investigated under continuous monoculture. In this study, rhizosphere soil microbial communities from a 5-year continuous mono-cropped peanut land were examined using Illumina HighSeq sequencing, with an N fertilization gradient that included 0 (N0), 60 (N60), 120 (N120) and 180 (N180) kg hm-2. Soil respiration rate (R s) and its temperature sensitivity (Q 10) were determined, with soil carbon-acquiring enzyme activities assayed. The obtained results showed that with N fertilization, soil mineral N (Nmin) was highly increased and the soil C/N ratio was decreased; yields were unchanged, but root biomass was stimulated only at N120. The activities of β-1,4-glucosidase and polyphenol oxidase were reduced across application rates, but that of β-1,4-cellobiohydrolase was increased only at N120. Bacterial alpha diversity was unchanged, but fungal richness and diversity were increased at N60 and N120. For bacterial groups, the relative abundance of Acidobacteria was reduced, while those of Alphaproteobacteria and Gammaproteobacteria were increased at N60 and N120. For fungal members, the pathogenic Sordariomycetes was inhibited, but the saprotrophic Agaricomycetes was promoted, regardless of N fertilization rates. RDA identified different factors driving the variations in bacterial (root biomass) and fungal (Nmin) community composition. N fertilization increased R s slightly at N60 and significantly at N120, mainly through the promotion of cellulose-related microbes, and decreased R s slightly at N180, likely due to carbon limitation. N fertilization reduced microbial biomass carbon (MBC) at N60, N120 and N180, decreased SOC at N120 and N180, and suppressed dissolved organic carbon (DOC) at N180. In addition, the unchanged Q 10 may be a joint result of several mechanisms that counteracted each other. These results are of critical importance for assessing the sustainability of continuously monocultured ecosystems, especially when confronting global climate change.

Green manure and maize intercropping with reduced chemical N enhances productivity and carbon mitigation of farmland in arid areas

Keeping high productivity and low soil carbon emission (CE) while reducing chemical fertilizer is a significant challenge for crop production in developing modern agriculture. A field experiment was conducted to evaluate the effect of intercropping green manure with reduced N on maize productivity and carbon mitigation in northwestern China. The field experiment used a split-plot design with three replicates. Three cropping patterns were maize-common vetch intercropping (M/V), maize-rape intercropping (M/R), and sole maize (M). Two N fertilizer rates formed the subplots: the conventional N rate was reduced by 25% (N1: 270 kg ha−1) and the conventional N rate (N2: 360 kg ha−1). The compensation effect (TCE, %) was used to quantify the degree of recovery of intercropping green manure on maize grain yield (GY) under N reduction. It was shown by the results that the negative effect of N reduction on maize GY was compensated by intercropping green manure. Maize-common vetch intercropping integrated with N reduction (M/VN1) had a more substantial compensation effect (TCE) with the planting years lengthening, and TCE was 1.0%, 0.9%, 4.1%, and 4.9% in 2018, 2019, 2020, and 2021, respectively. The CE of the cropping system was decreased by intercropping green manure compared to sole maize. The CE in the intercropping system was further decreased by N reduction, and the CE of M/RN1 and M/VN1 was decreased by 27.7% and 32.1%, respectively, compared to MN2 (i.e., the control). Finally, the CE of the intercropping system was decreased by M/VN1 by 6.5% compared to M/RN1 in 2019–2021. We used the ratio of net primary productivity to carbon emission (NPP/CE) to determine soil C sequestration (CS) potential. Intercropping green manure with N reduction in enhancing soil CS mainly occurred in the late growth period of maize. Over the four years of study, the ratios of NPP/CE for M/RN1 and M/VN1 were 23.3% and 32.9%, respectively, greater than that of MN2; also, it of M/VN1 was increased by 8.9% compared to M/RN1 in 2019–2021. M/VN1 had great potential for enhancing soil CS. Thus, adding green manure as an intercropping component in the maize cropping system while reducing chemical N fertilizer is a promising system to enhance maize productivity and carbon mitigation in the farmlands of arid areas.

What is the pathway that determines the diurnal lag time between soil respiration and soil temperature?

Soil respiration (Rs) is a critical component of the global carbon cycle in terrestrial ecosystems and is considered a function of soil temperature (Ts); however, Rs often shows a hysteresis effect with Ts. The mechanism causing this hysteresis pattern remains controversial, hindering our ability to accurately simulate and predict Rs in response to climate change. Here, a two-year field experiment was conducted to investigate the factors and pathways influencing the diurnal lag time between Rs and Ts (LTTs−Rs); we used an automatic chamber continuous measurement of Rs combined with 3 levels of precipitation manipulation: −30 % (P − 30), +0% (CK), +30 % (P + 30) of ambient precipitation in rain-fed winter wheat (Triticum aestivum L.) and alfalfa (Medicago sativa L.) agroecosystems on the Loess Plateau, China. The results indicated that the monthly average diurnal dynamic peak time of Rs always occurred prior to that of Ts. The LTTs−Rs ranged from 1 h to 8 h in winter wheat under the three precipitation treatments over two years. The range was similar in alfalfa under the CK and P + 30 treatments; however, in alfalfa, the value ranged from 1 h to 10 h under the P − 30 treatment. The LTTs−Rs value is determined by the direct pathway of photosynthetic product transport (the lag time between Rs and photosynthetically active radiation (PAR), LTRs−PAR) and the indirect pathway of heat transfer (the lag time between Ts and PAR, LTTs−PAR); that is, the LTTs−Rs is equal to the sum of the LTRs−PAR and LTTs−PAR. Moreover, the LTTs−PAR is equal to the sum of the lag time between air temperature (Ta) and PAR (LTTa−PAR) and the lag time between Ta and Ts (LTTs−Ta) in both winter wheat and alfalfa under the three precipitation treatments. Soil volume water content (VWC) affects LTTs−Rs by influencing the process (i.e., the transport process of heat and photosynthate) that comprises the LTTs−Rs. This is the first attempt to quantify the pathway processes that determine the LTTs−Rs and clarify the mechanism of the LTTs−Rs response to VWC. The results have important implications for our understanding of the LTTs−Rs production mechanisms and the accurate prediction of soil carbon emissions by future models.

Soil CO2 and N2O emissions and microbial abundances altered by temperature rise and nitrogen addition in active-layer soils of permafrost peatland.

Changes in soil CO2 and N2O emissions due to climate change and nitrogen input will result in increased levels of atmospheric CO2 and N2O, thereby feeding back into Earth's climate. Understanding the responses of soil carbon and nitrogen emissions mediated by microbe from permafrost peatland to temperature rising is important for modeling the regional carbon and nitrogen balance. This study conducted a laboratory incubation experiment at 15 and 20°C to observe the impact of increasing temperature on soil CO2 and N2O emissions and soil microbial abundances in permafrost peatland. An NH4NO3 solution was added to soil at a concentration of 50 mg N kg-1 to investigate the effect of nitrogen addition. The results indicated that elevated temperature, available nitrogen, and their combined effects significantly increased CO2 and N2O emissions in permafrost peatland. However, the temperature sensitivities of soil CO2 and N2O emissions were not affected by nitrogen addition. Warming significantly increased the abundances of methanogens, methanotrophs, and nirK-type denitrifiers, and the contents of soil dissolved organic carbon (DOC) and ammonia nitrogen, whereas nirS-type denitrifiers, β-1,4-glucosidase (βG), cellobiohydrolase (CBH), and acid phosphatase (AP) activities significantly decreased. Nitrogen addition significantly increased soil nirS-type denitrifiers abundances, β-1,4-N- acetylglucosaminidase (NAG) activities, and ammonia nitrogen and nitrate nitrogen contents, but significantly reduced bacterial, methanogen abundances, CBH, and AP activities. A rising temperature and nitrogen addition had synergistic effects on soil fungal and methanotroph abundances, NAG activities, and DOC and DON contents. Soil CO2 emissions showed a significantly positive correlation with soil fungal abundances, NAG activities, and ammonia nitrogen and nitrate nitrogen contents. Soil N2O emissions showed positive correlations with soil fungal, methanotroph, and nirK-type denitrifiers abundances, and DOC, ammonia nitrogen, and nitrate contents. These results demonstrate the importance of soil microbes, labile carbon, and nitrogen for regulating soil carbon and nitrogen emissions. The results of this study can assist simulating the effects of global climate change on carbon and nitrogen cycling in permafrost peatlands.

Soil Carbon Emission Sources Differ Under Litter and Nutrient Addition During Secondary Succession: Evidence from a Mesocosm Study Using a Three-Transfer-Pool Model

Soil Carbon Emission Sources Differ Under Litter and Nutrient Addition During Secondary Succession: Evidence from a Mesocosm Study Using a Three-Transfer-Pool Model

Temporal patterns of soil carbon emission in tropical forests under long-term nitrogen deposition

Temporal patterns of soil carbon emission in tropical forests under long-term nitrogen deposition

Recent cover crop adoption is associated with small maize and soybean yield losses in the United States.

Cover crops are gaining traction in many agricultural regions, partly driven by increased public subsidies and by private markets for ecosystem services. These payments are motivated by environmental benefits, including improved soil health, reduced erosion, and increased soil organic carbon. However, previous work based on experimental plots or crop modeling indicates cover crops may reduce crop yields. It remains unclear, though, how recent cover crop adoption has affected productivity in commercial agricultural systems. Here we perform the first large-scale, field-level analysis of observed yield impacts from cover cropping as implemented across the US Corn Belt. We use validated satellite data products at sub-field scales to analyze maize and soybean yield outcomes for over 90,000 fields in 2019-2020. Because we lack data on cover crop species or timing, we seek to quantify the yield impacts of cover cropping as currently practiced in aggregate. Using causal forests analysis, we estimate an average maize yield loss of 5.5% on fields where cover crops were used for 3 or more years, compared with fields that did not adopt cover cropping. Maize yield losses were larger on fields with better soil ratings, cooler mid-season temperatures, and lower spring rainfall. For soybeans, average yield losses were 3.5%, with larger impacts on fields with warmer June temperatures, lower spring and late-season rainfall, and, to a lesser extent, better soils. Estimated impacts are consistent with multiple mechanisms indicated by experimental and simulation-based studies, including the effects of cover crops on nitrogen dynamics, water consumption, and soil oxygen depletion. Our results suggest a need to improve cover crop management to reduce yield penalties, and a potential need to target subsidies based on likely yield impacts. Ultimately, avoiding substantial yield penalties is important for realizing widespread adoption and associated benefits for water quality, erosion, soil carbon, and greenhouse gas emissions.

Deformation and Volumetric Change in a Typical Retrogressive Thaw Slump in Permafrost Regions of the Central Tibetan Plateau, China

Ice-rich permafrost in the Qinghai–Tibet Plateau (QTP), China, is becoming susceptible to thermokarst landforms, and the most dramatic among these terrain-altering landforms is retrogressive thaw slump (RTS). Concurrently, RTS development can in turn affect the eco-environment, and especially soil erosion and carbon emission, during their evolution. However, there are still a lack of quantitative methods and comprehensive studies on the deformation and volumetric change in RTS. The purpose of this study is to quantitatively assess the RTS evolution through a novel and feasible simulation framework of the GPU-based discrete element method (DEM) coupled with the finite difference method (FDM). Additionally, the simulation results were calibrated using the time series observation results from September 2021 to August 2022, using the combined methods of terrestrial laser scanning (TLS) and unmanned aerial vehicle (UAV). The results reveal that, over this time, thaw slump mobilized a total volume of 1335 m3 and approximately 1050 m3 moved to a displaced area. Additionally, the estimated soil erosion was about 211 m3. Meanwhile, the corresponding maximum ground subsidence and headwall retrogression were 1.9 m and 3.2 m, respectively. We also found that the amount of mass wasting in RTS development is highly related to the ground ice content. When the volumetric ice content exceeds 10%, there will be obvious mass wasting in the thaw slump development area. Furthermore, this work proposed that the coupled DEM-FDM method and field survey method of TLS-UAV can provide an effective pathway to simulate thaw-induced slope failure problems and complement the research limitations of small-scale RTSs using remote sensing methods. The results are meaningful for assessing the eco-environmental impacts on the QTP.

Effects of Rhus typhina Invasion on Soil Physicochemical Properties and Carbon Emissions in Urban Green Spaces

Alien plants invasion have become a hot issue in the field of ecology. The invasion of alien plants is usually accompanied by changes in the physical and chemical properties of the soil, the ensuing negative feedback creates a favorable environment for its own growth and expansion. Invasive plans have a strong ability to sequester carbon, which can greatly affect the original local ecological environment. In this study, we selected Rhus typhina, an invasive plant widely used for greening, as the experimental subject and natural growing grassland as the control. The aims were to investigate the effects of different degrees of invasion of R. typhina on soil physicochemical properties and carbon emissions, and to explore the influential factors on carbon emission. The results showed that R. typhina invasion significantly increased soil pH, total nitrogen content, easy extraction of glomalin-related soil protein (EEG) and cumulative CO2 emissions (CEM). It is worth noting that the CEM increased significantly during the severe invasion by R. typhina. The significant increase in soil NH4+-N content and the decrease in soil NO3−-N content indicate that the soil after the invasion of R. typhina has better uptake of NH4+-N. Temperature and soil moisture content had significant direct effects on CEM, while NH4+-N, NO3−-N, EEG and temperature sensitivity of soil organic carbon mineralization Q10 (30 °C/20 °C) had a direct but non-significant effect on CEM. The above findings suggest that R. typhina can generate positive feedback by influencing the physicochemical properties and CEM of the soil, opening the way for its own expansion, which can be targeted to prevent the destruction of local ecosystems during the introduction of cultivation and subsequent management.

Effects on soil organic carbon accumulation and mineralization of long-term vegetation restoration in Southwest China karst

Vegetation restoration significantly changes soil organic carbon (SOC) accumulation and mineralization, obviously affects soil carbon pool. To clarifying effects of vegetation restoration on SOC accumulation and mineralization is of great significance in reducing carbon emission and increasing carbon sequestration. In the present study, the effects on SOC accumulation and mineralization of four types of vegetation restoration engineering including seven species planting measures, all carried out for 28–31 years, were studied. Results showed the long-term vegetation restorations had significant effects on SOC accumulation and mineralization. Tree and vine forest construction measures significantly increased total SOC content and reserves, recalcitrant organic carbon content and proportion, and also obviously raised SOC mineralization rate and cumulative mineralization amount. Grassland construction measures significantly reduced total SOC content and reserves, obviously increased the proportion of soil active organic carbon, and also remarkably raised SOC cumulative mineralization proportion. In addition, the long-term vegetation restoration measures significantly changed the temperature sensitivity of SOC mineralization. The long-term vegetation restoration has remarkable effects on SOC mineralization and accumulation in Southwest China karst area. In the restoration, tree and vine forest construction measures should be preferred, and grassland construction measures should not be implemented. The present study results provide theoretical bases for scientific vegetation restoration of degraded karst ecosystems in Southwest China Karst and are of great significances in reducing soil carbon emission and increasing soil carbon sequestration.