In drylands, biocrusts function as essential components of the nitrogen cycle and display pronounced sensitivity to external nitrogen inputs. Episodic rainfall events can mobilize dry-deposited nitrogen into shortterm pulse that influences nitrogen retention and transformation. However, the effects of short-term nitrogen pulse, commonly encountered in drylands, on biocrust nitrogen dynamics remain poorly understood. This study simulates rainfall-driven short-term nitrogen pulse to examine how varying pulse concentrations impact biocrusts nitrogen fixation, ammonia oxidation, and overall nitrogen balance under conditions of intensified nitrogen deposition after a 13-year nitrogen addition experiment in Gurbantunggut Desert. The nitrogen pulse sharply disrupted biocrusts’ nitrogen cycling. Both nitrogen fixation and ammonia oxidation rates declined precipitously immediately after the pulse. However, within 14–21 days, these rates rebounded to or even surpassed pre-pulse levels. This pattern reflects the biocrusts’ acute sensitivity to nitrogen perturbations, as well as their ecological resilience. Over 21 days, cumulative nitrogen fixation decreased by 47

Soil multifunctionality (SMF) and the soil quality index (SQI) are essential indicators of soil function, productivity, and health. Additionally, the spatial variability of soil multifunctionality (SVM) signifies soil heterogeneity. Biological soil crusts (Biocrusts) can affect these indicators. However, there is little information about the role of biocrusts in regulating the response of multiple ecosystem functions to climate change. We evaluated the relative importance of climate, soil environment, and biocrusts variables as drivers of SMF, SQI, and SVM at 74 sites in the Gurbantunggut Desert. Soil SMF, and SQI increase with the coverage of lichen and moss crust. Biocrusts index, SMF and SQI increase with an increase in the mean annual temperature. Biocrusts index, SMF and SQI increase first with an increase in mean annual precipitation (MAP)< 163 mm and then decrease. SVM display a significant decreasing trend with the increase of MAP. The structural equation model (SEM) demonstrate that the spatial distribution can significantly influence the biocrusts, soil SQI and SVM. Biocrusts has a significant positive influence on soil SMF (0.47)and SQI (0.31). Soil SMF has a significant negative effect on SVM (-0.50), and SQI (0.59) has a significant positive effect. We provide the first quantitative evidence that biocrust type and a 163 mm precipitation threshold govern SMF through opposing direct vs. indirect temperature pathways, offering a predictive rule-of-thumb for dryland management under climate change. The findings contribute decidedly to our understanding of the patterns and mechanisms driving SMF, SQI, and SVM in drylands, which is important for predicting changes in ecosystem function under climate change.

Grassland ecosystems play a crucial role in the global carbon cycle, yet the spatial patterns and drivers of soil organic carbon density (SOCD) across aridity gradients remain insufficiently understood. Here, we used the Carbon Density Dataset of China's Terrestrial Ecosystems (2010s) and applied random forest models to simulate SOCD at two soil depths (SOCD0-20 cm and SOCD0-100 cm) in arid and humid grasslands. We further quantified the contributions of environmental drivers and projected future SOCD dynamics under Shared Socioeconomic Pathways (SSPs). Results showed that SOCD was lower in arid than in humid regions, but due to their vast extent, arid regions contained larger total soil carbon stocks. The 0-20 cm layer accounted for approximately 50% of the SOCD in the 0-100 cm profile. In arid regions, SOCD0-20 cm was mainly controlled by mean annual temperature and soil moisture, while SOCD0-100 cm depended on clay content and total nitrogen. In humid regions, SOCD0-20 cm was strongly influenced by temperature and NDVI, whereas SOCD0-100 cm was regulated by clay and nitrogen. Under future SSP scenarios, SOCD is projected to decline in arid regions but increase in humid regions, indicating an enhanced carbon sink potential. SOCD0-20 cm showed higher variability and lower stability than SOCD0-100 cm. These findings clarify the spatial heterogeneity and depth-dependent controls of grassland SOCD and provide a scientific basis for region-specific soil carbon management, contributing to China's "dual carbon" goals and sustainable grassland policies.

Against the backdrop of continuously increasing global nitrogen (N) deposition, the changes in photosynthetic carbon (C) allocation patterns of desert plants and their underlying mechanisms affecting soil C sequestration remain poorly understood. This study selected two representative species from desert ecosystems: the non-vascular moss Syntrichia caninervis and the vascular ephemeral plant Erodium oxyrhinchum as research subjects. Three N deposition levels were implemented: 0 (N0), 10.0 (N10), and 30.0 kg N ha−1 a−1 (N30), combined with 13C stable isotope labeling technique, to systematically investigate the effects of N deposition on plant photosynthetic C allocation and soil C sequestration. The experiment demonstrated that: (1) Aboveground 13C content in both species decreased significantly with increasing N input (P < 0.05); (2) N deposition significantly promoted photosynthetic C transfer to soil, with soil 13C allocation increasing from 0.8

Global warming has increased the frequency and severity of extreme climate events, resulting in the mortality of desert moss crusts. However, the pathways by which moss crust mortality affects rainfall partitioning and soil moisture dynamics remain poorly understood. We simulated moss crust mortality by applying heat shocks and established three treatments: bare sand, living moss crust, and dead moss crust. Using high-precision sensors, we continuously monitored soil moisture at depths of 0–3 cm, 3–6 cm, 6–9 cm, 9–12 cm, and 12–15 cm over a four-year period, aiming to quantify soil water content in the vertical soil profile and its dynamic response to rainfall events following moss crust mortality. Compared with living moss crusts, moss crust mortality significantly reduced soil water content in the upper 0–15 cm soil layer. Moreover, relative to bare sand, the dead crust treatment exhibited poorer hydrological performance, and this negative effect persisted for at least four years. Following rainfall events, moss crust mortality shifted soil moisture distribution toward shallower layers, shortened the response lag time, accelerated wetting front advancement, reduced water recharge to deeper soil layers, and increased the rate of water depletion. Rainfall amount and intensity were key factors regulating these soil moisture response characteristics. In particular, under the dead crust treatment, larger rainfall events resulted in greater losses of stored water. The mortality of moss crusts exerted a long-term negative impact on the availability of surface soil moisture in desert ecosystems, posing a significant threat to the establishment of plant communities and overall ecosystem functioning. This underscores the importance of protecting desert biocrusts and restoring their soil water regulation functions to improve water availability and ecosystem stability in degraded desert ecosystems.

The impact of global climate change and human-induced nitrogen (N) deposition on winter weather patterns will have consequences for soil N cycling and greenhouse gas emissions in temperate deserts. Biological soil crusts (referred to as biocrusts) are crucial communities in soil and significant sources of nitrous oxide (N2O) emission in desert ecosystems and are sensitive to environmental changes. The contribution of bacteria and fungi to N2O production in drylands has been acknowledged. However, the effect of changes in snow cover and N deposition on the N2O production of different microbial groups of microorganisms is not yet clear. In this study, we examine the responses of fungi and bacteria mediated pathways involved in soil N2O production from biocrusts to longterm snow cover manipulation and N addition experiments in the Gurbantunggut Desert. These soils were incubated and subjected to biocide treatments (such as cycloheximide and streptomycin, and fungal and bacterial inhibitors), after which rates of potential nitrification and N2O production were measured. Compared with controls, snow removal treatments from bare sand, lichen crust and moss crust reduced background rates of N2O production by 29.41 %, 26.21 % and 20.49 %, respectively; N2O production rates were 1.53-fold higher in bare sand, 1.38-fold higher in lichen crust, and 1.56-fold higher in moss crust after N addition. The addition of streptomycin significantly reduced the potential nitrification rates of bare sand and biocrusts, indicating that bacteria may be important sources of NO3- production in biocrusts rather than fungi. Conversely, fungi were main sources of N2O production in biocrusts. Additionally, fungi also played a major role in N2O production in biocrusts after snow cover manipulation and N addition. Both snow cover manipulation and N addition treatment indirectly affected the N2O production in biocrusts by considerably affecting the content of substrate N and the abundance of microbial groups. Our research suggests that fungi are main contributors for denitrification in biocrusts, and that snow cover changes (removal snow and double snow) and N addition alter the contribution of biotic pathways responsible for N cycling.

Biological soil crusts (biocrusts) are essential for nitrogen (N) cycling in arid ecosystems, but how snow cover modulates these processes remains unclear. This study investigated the effects of variable snow cover on N fixation, ammonia oxidation (AO), and microbial networks across moss-, lichen-, and cyanobacteria-dominated biocrusts in China's Gurbantunggut Desert. Snow manipulations double snow (DS), ambient snow (CK), and removed snow (RS) were applied to biocrust plots in winter. Nitrogen fixation and AO rates, soil properties soil water content (SWC), organic carbon (SOC), inorganic N, and microbial co-occurrence networks were analyzed in spring. DS enhanced nitrogen fixation rates, particularly in cyanobacteria-dominated crusts (up to 0.4 μg N g-1 day-1), while moss crusts showed elevated fixation under RS conditions (rates can up to 0.4 μg N g-1 day-1), which correlated with increased SWC (r = 0.72) and SOC (r = 0.65). Conversely, RS reduced AO rates by 50-67 % across biocrusts, with cyanobacteria experiencing the steepest decline (20 μg N g-1 day-1). Microbial networks under DS exhibited higher modularity in moss crusts (modularity = 0.85), indicating structured, cooperative communities, while RS fragmented networks, especially in cyanobacteria (modularity = 0.41). Soil salinity (EC) and pH were negatively correlated with microbial activity under RS. Moss crusts showed resilience, maintaining stable N fixation and microbial diversity under varying snow cover, whereas cyanobacteria showed increased sensitivity to drought. These results highlight the critical role of snow cover in maintaining N cycling during the spring season via moisture retention and SOC accumulation. Declining snow cover, as predicted under climate change, may disproportionately affect cyanobacteria-dominated crusts and thus destabilize soil fertility. Conservation strategies that prioritize bryophyte biocrusts could enhance ecosystem resilience in arid landscapes. This study highlights the interplay between snow regimes, biocrust type, and microbial functionality, and provides insights for predicting N cycling dynamics in warming drylands.

During periods with no precipitation, desert ecosystem soils periodically absorb air moisture at night to form non-rainfall water inputs (NRWIs), while substantial carbon dioxide (CO2) emissions are typically observed during midday. However, the intrinsic relationship between these periodic NRWIs and the CO2 release phenomenon remains unclear. In this study, we utilized biological soil crusts and employed in situ observation methods during the summer and fall. We also conducted humidity- and temperature-controlled experiments to investigate the effects and potential mechanisms of NRWIs and temperature variations on daily soil CO2 release. We found that soil accumulated NRWIs and soil respiration rates reached their peak values at dawn and midday, respectively, with a lag of 2-4 h between the two. The accumulated NRWIs increased with the development of the crusts across different cover types, however, there was no significant difference in maximum soil respiration rate observed at noon. Notably, the significant release of CO2 at midday was eliminated when the soil NRWIs were suppressed, demonstrating that the NRWIs were the primary determinant of the substantial CO2 release at midday. Furthermore, the soil sucrase activity, dehydrogenase activity, microbial richness, and the Chao1 index of soil microorganisms were significantly higher at noon than at night, indicating that microbial activity was greater during the day compared with at night. Our results confirm that the significant midday CO2 release in desert ecosystems is like a daily "micro-Birch effect" phenomenon induced by NRWIs. This phenomenon may be due to the transition between dormancy and activation of microorganisms mediated by NRWIs. This study demonstrates that NRWIs induce consistent daily pulses of CO2 in desert ecosystems, representing a previously overlooked microbial-driven pathway. Given the extensive coverage of deserts in global terrestrial ecosystems, this mechanism may have implications for carbon cycling and budget estimates in drylands and potentially at broader scales.

Nitrogen-limited drylands are highly sensitive to environmental changes, with biological soil crusts playing a key role in biological nitrogen fixation. Ammonia oxidation, the rate-limiting step in nitrification, is essential for nitrogen retention in soils. Despite sustained high global nitrogen deposition, the impacts of varying nitrogen addition levels on nitrogen fixation, ammonia oxidation by crusts, and nitrogen cycling remain poorly understood. Crusts were sampled in April and October from plots in the Gurbantunggut Desert, where nitrogen had been applied for 13 years, to assess nitrogen fixation, ammonia oxidation rates, and the functional microbial community structure. Results indicated nitrogen addition reduced nitrogen fixation, with the highest nitrogen addition (3.0 g N m2 yr-1) causing a ∼60 % decline, suggesting a microbial shift towards reliance on added nitrogen. In contrast, low nitrogen addition (0.5 g N m-2 yr-1) enhanced ammonia oxidation by 293 %, likely due to the alleviation of substrate limitations. However, higher nitrogen addition (N1.5, N3.0) led to a reduction in ammonia oxidation, with microorganisms such as Scytonema, Nitrososphaera, and Nitrosopumilus playing key roles in both processes. Notably, nitrogen fixation rates were generally lower during the dry season, while ammonia oxidation increased under N0 treatment. Nitrogen addition influenced the nitrogen fixation and ammonia oxidation capacities of the crusts, heightening the risk of nitrogen loss but diminishing the influence of prolonged drought. These findings underscore the need to consider nitrogen levels and seasonal dynamics when managing soil nitrogen processes to maintain the stability of dryland ecosystems and the nitrogen cycle, it is essential to reduce anthropogenic nitrogen deposition and mitigate the growing impacts of drought.

Biological soil crusts (biocrusts) development is a fundamental factor affecting stability by wind prevention, sand fixation, and desert surface soil stability enhancement, and aridity is an important driver for altering soil stability in drylands. The physical properties of biocrusts and binding sand quantity (BSQ) are important indicators for characterizing the stability of desert soil. The relationships between biocrust physical properties and BSQ are not clear, which is not conducive to a comprehensive understanding of the ecological functions of biocrusts. The different successional stages of biocrusts in the arid region of Northwest China were selected to study their physical properties and BSQ. The physical properties and BSQ of the different types of biocrusts were measured. The responses of the physical properties and BSQ of different types of biocrusts to aridity were analyzed. The results showed that the physical properties and BSQ increased significantly with biocrust development. The thickness, roughness, compressive strength, shear strength, and BSQ of the biocrusts show a significant increasing trend with the development and increase of biocrusts and coverage. BSQ and compressive strength increased with increasing thickness and roughness. Physical properties, physical multifunctionality (P-SMF), and BSQ of different biocrust types showed significantly different trends with increasing aridity. The results of structural equation modeling also revealed that the P-SMF and BSQ had different responses with increasing aridity. This study contributes to a comprehensive understanding of biocrust structure and function, particularly for wind prevention and sand fixation, as well as surface stability. This study provides a new methodology and new ideas for determining the distribution and surface stability of biocrusts and is highly important for land management and conservation in drylands.

Biological soil crusts (BSCs) are essential components of drylands, yet the effects of their development on soil multifunctionality (SMF) and the drivers behind these effects remain unclear. We sampled 11 sites in Northwest China's deserts, representing different successional stages of BSC development (i.e. cyanobacterial, lichen and moss crusts) as well as bare sand areas. We assessed the SMF of the crust layer and underlying soil at various depths (0-2, 2-5, 5-10, 10-20 cm) and also explored the influence of climatic factors (mean annual temperature, aridity, and solar radiation), crust characteristics (compressive strength, roughness, and thickness), and soil properties (pH, electrical conductivity, soil water content) on SMF across these layers. The presence of BSCs significantly enhanced soil nutritional status [soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), ammonia (NH4+-N), nitrate (NO3--N), and available phosphorus (AP)] throughout the 0-20 cm soil depth and increased SMF in the top 0-10 cm. These positive effects intensified with as BSCs progressed from cyanobacterial to lichen to moss stages, but decreased with soil depth. In the crust layer, SMF across all BSC types was positively influenced by our climatic factors. However, as BSCs developed, the negative influence of climatic factors (mainly solar radiation) and soil properties (mainly pH) on SMF decreased, while the positive influence of crust characteristics (mainly thickness) increased. The influence of climate, crust, and soil factors on SMF also decreased with increasing soil depth and varied by BSC type. Further, our findings demonstrate that the BSC development can buffer the negative effects of increased soil pH and solar radiation on SMF while enhancing the positive effects of crust properties, particularly thickness. This highlights the importance of preserving and promoting BSC development to enhance surface soil multifunctionality and mitigate the adverse effects of climate change on dryland ecosystem multifunctionality.

Aridity has serious impacts on the pools, fluxes and processes of terrestrial carbon (C) and nitrogen (N) cycles. Drylands, with high aridity, also being particularly sensitive to global shifts, require accurate estimation of soil organic carbon (SOC) and total nitrogen (STN) pools for a comprehensive grasp of dryland C and N dynamics within the global C and N cycle. Hence, SOC and STN of 2895 soil samples combined with 11 selected environmental covariates were collected from 175 sampling sites in the drylands of China, the spatial distributions of SOC density (SOCD) and STN density (STND) were mapped with best-performing random forest model. SOC0- 100cm and STN 0-100cm stocks were 30.84 and 2.02 Pg, respectively. Mean annual precipitation and soil moisture were identified as the primary drivers of SOCD 0-30cm and STND 0-30cm , while mean annual temperature influenced SOCD 30-50cm and STND 30-50cm , and soil clay content affected SOCD 50-100cm and STND 50-100cm . Future warming is projected to reduce both SOCD and STND, whereas increased precipitation is expected to have a positive effect on both variables in drylands. Under future climate scenarios outlined by the Representative Concentration Pathway, declines in both SOCD and STND are anticipated, with STND exhibiting a more pronounced decrease. A 1.5 degrees C increase in temperature had the greatest effect on SOCD, while a 15 % decrease in precipitation had the greatest effect on STND. In conclusion, the spatiotemporal estimations presented in this study serve as a valuable supplement to existing SOC and STN stock measurements, enhancing our understanding of C and N cycling in drylands. Our findings are instrumental for effective C and N sinks management, providing valuable data for informed decision-making. For example, afforestation in drylands can lead to significant increases in soil C and N stocks. However, In the future, further warming may lead to large losses of soil C and N in drylands.

As the most advanced stage of biological soil crusts, moss crusts are crucial for maintaining the stability of the desert soil surface and regulating the hydrological and biochemical processes. Continuous warming and extreme precipitation events have resulted in the death of desert moss-dominated biocrusts to varying degrees. However, there is still a lack of knowledge on how dead moss-dominated biocrusts influence nutrients cycles in desert soils. In this study, we selected moss-dominated biocrusts in the Gurbantunggut desert. Soil chemical properties and six types of extracellular enzyme activities were determined at different soil depths underneath living and dead moss-dominated biocrusts. The results showed that dead moss-dominated biocrusts significantly enhanced the content of carbon, nitrogen, phosphorus and related extracellular enzyme activities, with the most pronounced effect on nitrate content and nitrate reductase activity. Meanwhile, the dead moss-dominated biocrusts alleviated microbial nitrogen limitation to a certain extent, but had limited effect on carbon limitation. Total nutrients (soil organic carbon, total nitrogen, total phosphorus) and pH were the most important factors influencing vector length, while the most important factors influencing vector angle were available nutrients (NO3-, NH4+, available phosphorus) and pH. These findings shed light on the impact of biocrusts on biogeochemical cycles and the nutrients (total or available nutrients) and pH were the vital factors influencing C- and N- limitation of microorganisms. This highlights the need to pay more attention to the impact of biocrusts' death on soil nutrient cycling when formulating desert ecosystem management under global climate change.

The characteristics of soil carbon pools across various ecosystems remain uncertain under different Shared Socioeconomic Pathways (SSPs) in China. Here, we conducted a meta-analysis of existing data and integrated machine-learning models to project spatiotemporal changes in soil organic carbon density (SOCD) by 2050 and 2100 under three Coupled Model Intercomparison Project Phase 6 (CMIP6) climate scenarios. For China's terrestrial ecosystems, national average SOCD was 4.08 kg C m2 in the 0-20 cm soil layer and 9.42 kg C m2 in the 0-100 cm layer, with corresponding carbon stocks of 39.18 Pg C and 90.46 Pg C, respectively. Wetlands exhibited the highest SOCD but contributed minimally to total carbon stock due to their limited area, while forests and grasslands served as the dominant carbon reservoirs, particularly in deeper soils. Spatially, SOCD was highest in northeastern China and the eastern Qinghai-Tibet Plateau, and lowest in northwestern arid regions. Climate was the most critical determinant of SOCD in both soil depth, although its explanatory power was relatively weaker for deep SOCD, where soil factors gained prominence. Human activities significantly reduced surface SOCD in forests and grasslands. Future climate change would exacerbate the decline of surface SOCD, particularly in wetlands, posing substantial challenges to achieving the 4 per mil initiative goals.

The drying-rewetting of soil can increase the release of greenhouse gases over a short time period and is one of the key pathways for greenhouse gas emissions in many terrestrial ecosystems, particularly in drylands. The mechanisms underlying this pulse of greenhouse gas emissions remain nearly unknown. Here, we conducted simulated soil rewetting experiments using typical cover of dryland soils (bareland, cyanobacteria/lichen-covered soil, and moss-covered soil). The 13C, 15N, and 18O labeling techniques allowed to explore the intrinsic mechanisms of rapid carbon (C) and nitrogen (N) release from the soils following rewetting. We found that the hydroxyl radical (˙OH) was produced after soil rewetting via the rapid activation of microorganisms. The carbon dioxide (CO2) and nitrous oxide (N2O) production strongly decreased after ˙OH removal, whereas the methane (CH4) production was not affected. The synergistic action between ˙OH oxidation and microbial enzymatic reactions increased CO2 production. The ˙OH also stimulated the oxidation of NH4 + to NO3 - and dominated the N2O production. Our results confirm the role of ˙OH in the production of greenhouse gases and indicate that microbially mediated ˙OH oxidation mechanisms are an overlooked key pathway for the emission of greenhouse gases during the soil rewetting. In the context of climate change, the extreme weather-induced drying-rewetting cycles in soils are becoming more frequent, making greenhouse gas emissions via the ˙OH oxidation pathway increasingly important.

We are far from understanding the spatial patterns of dryland soil carbon and nitrogen stocks and how they vary among different land cover types. We used data from 12,000 sites from 129 countries in global drylands to estimate soil organic carbon (SOC) and total nitrogen (STN) stocks in different land cover types, explore the factors driving their spatial distribution, and predict the trends under different climate scenarios in global drylands. SOC and STN stocks in the upper 100 cm reached 419.5 and 38.2 Pg, respectively, with the upper 0-30 cm accounting for half of them. The largest SOC stocks were found in forests, shrublands and grasslands, while STN stocks peaked in forests, bare areas and croplands. The factors driving the spatial patterns of SOC and STN varied among soil depths, with mean annual temperature, pH and aridity being the main factors driving the spatial patterns in SOC and STN density for 0-30 cm, and soil texture the strongest factor for 60-100 cm. Under the Representative Concentration Pathways (RCP) 4.5 scenario, SOC and STN stocks were predicted to decrease by 3.6 % and 4.0 %, respectively, from 2020 to 2100, whereas under the RCP 8.5 scenario, the projected decreases were 5.9 % and 6.4 % respectively. Our results indicate that if we want to accurately predict C and N accumulation, and design effective mitigation measures in terrestrial ecosystems under future climatic scenarios, we need to better explore the drivers that operate at the deeper soil depths, which also accumulate a significant amount of SOC and STN.

The drylands of China cover approximately 6.6x106 km2 and are home to approximately 5.8x108 people, providing important ecosystem services for human survival and development. However, dryland ecosystems are extremely fragile and sensitive to external environmental changes. Land use and land cover (LULC) changes significantly impact soil structure and function, thus affecting the soil multifunctionality (SMF). However, the effect of LULC changes on the SMF in the drylands of China has rarely been reported. In this study, we investigated the characteristics of the SMF changes based on soil data in the 1980s from the National Tibetan Plateau Data Center. We explored the drivers of the SMF changes under different LULC types (including forest, grassland, shrubland, and desert) and used structural equation modeling to explore the main driver of the SMF changes. The results showed that the SMF under the four LULC types decreased in the following descending order: forest, grassland, shrubland, and desert. The main driver of the SMF changes under different LULC types was mean annual temperature (MAT). In addition to MAT, pH in forest, soil moisture (SM) and soil biodiversity index in grassland, SM in shrubland, and aridity index in desert are crucial factors for the SMF changes. Therefore, the SMF in the drylands of China is regulated mainly by MAT and pH, and comprehensive assessments of the SMF in drylands need to be performed regarding LULC changes. The results are beneficial for evaluating the SMF among different LULC types and predicting the SMF under global climate change.

Soil elemental stoichiometry can characterize soil nutrient storage, supply capacity, and limitation. C:N:P stoichiometry is considered an important indicator of soil nutrient status during soil development. Drylands are critical terrestrial environments and are considered to be the largest biome on Earth. Our study aimed to investigate the C:N:P stoichiometric characteristics and drivers of surface soil in the drylands of China. Our study was conducted based on soil nutrient data derived from the National Tibetan Plateau Data Center and environmental data. We used structural equation modeling, variation partitioning analysis, redundancy analysis, and other methods to investigate whether there are spatial patterns and interrelationships among soil C, N, P, and C:N:P in the drylands of China and to analyze the drivers influencing the changes in C, N, P, and C:N:P. Similarly, C, N, and P density of the surface soil in the drylands of China were low (3.44, 0.14 and 0.10 kg/m2, respectively). Highly significant non-linear relationships were observed between all the nutrients and their corresponding stoichiometric ratios, except for C and P, which exhibited significant linear relationships. Aridity and plant (vegetation) were the main drivers of soil C and N density in drylands, while the main driver of P density was aridity; the soil environment contributed most to the relative changes in C, N, P, and C:N:P. In conclusion, the soil C, N, and P densities in the drylands of China were low. Plant, climate, and soil together explained 47.5–81.3

Biological soil crusts(BSCs)are the main active groundcover community in arid regions.BSCs can significantly affect the material cycle and energy exchange,improve the physical,chemical,and biological prop-erties of surface soil,and influence the soil multifunctionality(SMF).Moss crust is an important type of BSCs.This study investigates the SMF variability of moss crust-covered and bare sand in the deserts of northwestern ar-id regions,and explored the main drivers of the variability.We analyzed eight crucial ecosystem function indica-tors.SMF was calculated by applying the mean method and factor analysis approach.We used the ordinary least square and structural equation modeling to explore the drivers of SMF changes.The results show that:(1)soil monofunctionality and SMF under moss crust cover were higher than those in bare sand(P<0.05).(2)The drivers of the SMF change in bare sand and under moss crust cover were very different.The main drivers of SMF in bare sand were aridity and soil water content,whereas the driver of SMF under moss crust cover was soil sand content(Sand).(3)The mean annual temperature had the largest indirect effect on changes in SMF for both soil in bare sand and under moss crust cover.Therefore,the development of moss crust significantly increased SMF and,in addition,modulated the relevant drivers of SMF.Our results are important for a deep understanding of the differ-ences and drivers of SMF in desert soil with bare sand and under moss crust cover.

甲烷(CH4)和氧化亚氮(N2O)等温室气体通量具有高度时空变化特点,通过野外站点直接测量耗时且费力.为弥补监测方面不足,解析变化环境下反硝化-分解模型(DNDC)模拟值和样地原位观测值之间的对应关系,探讨模型在温室气体预测方面的潜力具有意义.本文选择古尔班通古特沙漠,对氮沉降影响下荒漠土壤CH4和N2O通量进行了模拟估计,并与实测数据进行了对比分析.结果表明:DNDC模型可较好地模拟荒漠土壤N2O通量的变化,模拟值与实测值显著相关(P＜0.001);而模型对荒漠土壤CH4吸收量的变化模拟效果不显著,但模拟的年累计吸收量与真实值较为符合.DNDC模型敏感性试验分析表明,随着年平均气温、土壤有机碳(SOC)含量和施氮量的增加,土壤N2O排放量和CH4的吸收量显著增加;年降水量对土壤N2O和CH4通量变化影响不显著;土壤容重与土壤N2O排放量和CH4吸收量显著负相关;土壤质地对两种温室气体排放的影响显著,其中砂壤土影响最大.多元回归分析表明温度是荒漠土壤N2O和CH4的通量变化最重要影响因素.因此,在全球变化背景下,尽管模型目前运用于荒漠区还存在一些问题,但在将来荒漠区温室气体通量的变化估算方面仍具有很强的应用价值.