Precipitation accumulations, integrated over rainfall events, are investigated using hourly data across continental China during the warm season (May–October) from 1980 to 2015. Physically, the probability of precipitation accumulations drops slowly with event size up to an approximately exponential cutoff scale sL where probability drops much faster. Hence sL can be used as an indicator of high accumulation percentiles (i.e., extreme precipitation accumulations). Overall, the climatology of sL over continental China is about 54 mm. In terms of cutoff changes, the current warming stage (1980–2015) is divided into two periods, 1980–97 and 1998–2015. We find that the cutoff in 1998–2015 increases about 5.6% compared with that of 1980–97, with an average station increase of 4.7%. Regionally, sL increases are observed over East China (10.9% ± 1.5%), Northwest China (9.7% ± 2.5%), South China (9.4% ± 1.4%), southern Southwest China (5.6% ± 1.2%), and Central China (5.3% ± 1.0%), with decreases over North China (−10.3% ± 1.3%), Northeast China (−4.9% ± 1.5%), and northern Southwest China (−3.9% ± 1.8%). The conditional risk ratios for five subregions with increased cutoff sL are all greater than 1.0, indicating an increased risk of large precipitation accumulations in the most recent period. For high precipitation accumulations larger than the 99th percentile of accumulation s99, the risk of extreme precipitation over these regions can increase above 20% except for South China. These increases of extreme accumulations can be largely explained by the extended duration of extreme accumulation events, especially for “extremely extreme” precipitation greater than s99.

土壤呼吸作用是土壤碳库向大气释放CO₂的主要途径，其在空间尺度上具有明显差异性，土壤呼吸的空间变化增加了土壤碳排放评估的不确定性，研究土壤呼吸作用空间异质性对于准确评估生态系统碳排放具有重要意义。2020年9月1日—9月6日，本研究沿呼伦贝尔草原东西样带随机选取了30个观测样地，利用土壤呼吸自动观测系统(Li-8100)测定土壤CO₂排放通量，并对其影响因子进行分析。结果表明：沿呼伦贝尔东西样带，随着降水量的减少，土壤呼吸速率显著减小；刈割利用下的土壤呼吸速率(3.36 μmol·m^-2·s^-1)显著大于放牧利用(1.87 μmol·m^-2·s^-1)；土壤有机碳含量和地上生物量是决定土壤呼吸空间异质性的主要因子，二者共同解释土壤呼吸变异的52%；土壤有机碳含量和植被生物量直接影响了土壤呼吸作用，土壤容重和土壤水分间接影响了土壤呼吸作用。降水空间格局变化和人类活动扰动是呼伦贝尔草原土壤呼吸作用空间异质性的主要驱动因素。

为揭示降水对天山北坡荒漠草原土壤呼吸和生态系统呼吸的影响，本实验以天山北坡荒漠草原为研究对象，通过测定3种模拟降水处理（CK，5 mm，18 mm，28 mm）下荒漠草原土壤呼吸速率和生态系统呼吸速率的变化特征。结果表明：不同降水处理下土壤呼吸速率和生态系统呼吸速率有明显的日变化趋势；3种降水处理下（28 mm，18 mm，5 mm）土壤呼吸速率较CK显著增加了22.93%，23.20%，12.07%，生态系统呼吸速率较CK显著增加了216.81%，153.27%，39.35%；不同降水处理下土壤呼吸速率和生态系统呼吸速率与土壤温度均表现为显著正相关关系；荒漠草原土壤呼吸速率与土壤含水量呈二次函数关系，生态系统呼吸速率与土壤含水量呈线性关系。因此，降水是影响天山北坡荒漠草原土壤呼吸速率和生态系统呼吸速率的主要因素。

Based on the method of space-for-time substitution， we investigated the coverage and frequentness of six typical biocrust-forming organisms， Cyanobacteria， Collema coccophorum， Endocarpon pusillum， Bryum argenteum， Didymodon vinealis and Syntrichia caninervis， in four artificial sand-binding vegetation zones established separately in 1956， 1964， 1981 and 1987 （representing four succession stages of 64， 56， 39 and 33 years after sand-binding vegetation establishment， respectively）， and calculated their niche widths and overlap values using different squares as resource states. Then we analyzed the patterns of interspecific relationships among biocrust-forming organisms during the succession of artificially sand-binding vegetation in Shapotou area by employing variance ratio method， chi-square test and interspecific correlation coefficient. The results showed that： （1） Along with the succession of sand-binding vegetation， the niche widths and overlap indices of the biocrust-forming organisms varied greatly， the niche widths of cyanobacteria rapidly narrowed （from 3.865 after 33 years to 0 after 64 years）， and the niche overlap values between cyanobacteria and other biocrust-forming organisms gradually decreased； the niche widths of B. argenteum and C. coccophorum remained almost constant and both were higher than that of other types， as well as their niche overlap values were also higher； the niche widths of D. vinealis， S. caninervis and E. pusillum was relatively small during early succession of the vegetation， but increased significantly with succession processing （from 1.607， 0 and 0.693 in 33 years to 3.699， 3.227 and 3.373 in 64 years， respectively）， and the niche overlap values among them increased simutenousely. （2） The overall interspecific correlations of biocrust-forming organisms changed from negative to positive accompanied with the succession of the sand-binding vegetation， and reached a maximum value （VR =1.15） at the oldest 64 years of the succession. With the succession of sand-binding vegetation， the association between different biocrust-forming organisms was gradually strengthened， and the community structure and species composition of surface cryptogms tended to be stable. This study not only provides a basis for revealing the symbiotic coexistence， interaction and evolution mechanism of biocrust-forming organisms in arid sandy areas， but also serves as an important reference for the theoretic research and application techniques using biocrust-forming organisms as the new sand-fixation materials.

温度和降水是干旱半干旱区土壤呼吸的重要扰动因子，全球气候变化导致的未来干旱半干旱区增温和降水变率增大对土壤呼吸有着重要影响。研究通过人工设置P_16×2.5mm、P_8×5mm、P_4×10mm、P_2×20mm、P_1×40mm的降雨频率梯度和增温2 ℃左右的控制试验，探讨不同降雨频率和增温处理对干旱半干旱区土壤呼吸的影响，以及土壤呼吸与土壤温湿度的关系及其对降雨频率改变的响应。结果表明：降雨频率和增温单独对土壤呼吸具有极显著影响（P<0.001），但是两者之间并无交互作用（P>0.5）；在降雨量一定的情况下，土壤呼吸速率随着降雨频率的减小而减小，即多频率小降雨事件激发的土壤呼吸速率大于小频率大降雨事件；增温促进土壤呼吸，提高了约11%的土壤呼吸。本结果有助于对未来干旱半干旱地区全球变暖背景下降雨格局的改变对土壤呼吸产生的影响进行预测，同时也为进一步估算该区域生态系统的碳收支提供参考数据。

土壤呼吸是陆地生态系统碳循环的关键指标，决定了土壤源二氧化碳(CO₂)进入大气的通量，对预测全球气候变化背景下区域乃至全球碳循环变化具有重要意义.本文通过室内短期培养试验测定了中国北方草地样带土壤样品的呼吸速率，研究了北方草地土壤呼吸的区域尺度格局及其与主要调控因子的关系.结果表明：土壤呼吸速率自西向东随年均降水量(MAP)增加呈逐渐增加的趋势，变化范围为0.35～2.09 μg CO₂C·g^-1·h^-1.其中，MAP<100 mm时，土壤呼吸速率为0.35～0.73 μg CO₂C·g^-1·h^-1；100 mm <MAP<200 mm时，土壤呼吸速率为0.57～0.98 μg CO₂C·g^-1·h^-1；MAP>300 mm时，土壤呼吸速率为0.83～2.10 μg CO₂C·g^-1·h^-1.土壤呼吸速率与年均降水量、地上生物量、土壤有机碳氮含量呈显著正相关，而与年均温和pH值呈显著负相关.增强回归树分析显示，年均降水量、地上生物量、土壤有机碳含量和土壤有机氮含量分别解释了土壤呼吸总变异的25.5%、23.6%、18.3%和12.5%，而土壤pH和年均温仅解释了10.8%和9.2%. 

Contents 41 I. 41 II. 42 III. 43 IV. 44 V. 45 Acknowledgements 46 References 46 SUMMARY: Precipitation (PPT) is a primary climatic determinant of plant growth and aboveground net primary production (ANPP) over much of the globe. Thus, PPT-ANPP relationships are important both ecologically and to land-atmosphere models that couple terrestrial vegetation to the global carbon cycle. Empirical PPT-ANPP relationships derived from long-term site-based data are almost always portrayed as linear, but recent evidence has accumulated that is inconsistent with an underlying linear relationship. We review, and then reconcile, these inconsistencies with a nonlinear model that incorporates observed asymmetries in PPT-ANPP relationships. Although data are currently lacking for parameterization, this new model highlights research needs that, when met, will improve our understanding of carbon cycle dynamics, as well as forecasts of ecosystem responses to climate change.© 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

土壤呼吸是全球陆地生态系统碳循环重要组成部分，降雨作为扰动因子对土壤呼吸动态的改变将直接影响全球碳平衡。探讨降雨对土壤呼吸的作用机制是陆地生态系统碳循环和碳收支研究的重要内容。本文综述了近年来国内外学者关于降雨引起的干湿交替对土壤呼吸影响机制的研究进展，阐述了土壤水分对土壤呼吸的影响及其机理。土壤水分在适宜范围内促进土壤呼吸，过高或过低均抑制土壤呼吸；降雨引起的干湿交替通过改变土壤水分影响土壤呼吸。一方面，干旱条件下，降雨引起的干湿交替主要通过短时间置换土壤中CO₂、增加土壤微生物呼吸底物、提高微生物活性、增强凋落物分解速率等途径提高土壤呼吸速率。另一方面，湿度较高的土壤经过短时间降雨迅速达到水分饱和或积水状态，降雨引发的干湿交替通过限制O₂进入土壤，形成厌氧环境，抑制微生物和根系呼吸。此外，降雨引发的干湿交替还通过地表积水淹没部分植株，降低植物叶面积，减少光合产物，显著抑制根系呼吸。为更准确估算降雨变化影响土壤呼吸对陆地生态系统碳平衡的干扰，提出了未来降雨对土壤呼吸影响研究需重点关注的3个方面：（1）降雨对土壤呼吸影响的微生物响应机制；（2）区分土壤自养呼吸和异养呼吸对降雨的响应机制；（3）降雨对土壤呼吸影响模型研究。

Soil respiration (Rs) is the second-largest terrestrial carbon (C) flux. Although Rs has been extensively studied across a broad range of biomes, there is surprisingly little consensus on how the spatiotemporal patterns of Rs will be altered in a warming climate with changing precipitation regimes. Here, we present a global synthesis Rs data from studies that have manipulated precipitation in the field by collating studies from 113 increased precipitation treatments, 91 decreased precipitation treatments, and 14 prolonged drought treatments. Our meta-analysis indicated that when the increased precipitation treatments were normalized to 28% above the ambient level, the soil moisture, Rs, and the temperature sensitivity (Q10) values increased by an average of 17%, 16%, and 6%, respectively, and the soil temperature decreased by -1.3%. The greatest increases in Rs and Q10 were observed in arid areas, and the stimulation rates decreased with increases in climate humidity. When the decreased precipitation treatments were normalized to 28% below the ambient level, the soil moisture and Rs values decreased by an average of -14% and -17%, respectively, and the soil temperature and Q10 values were not altered. The reductions in soil moisture tended to be greater in more humid areas. Prolonged drought without alterations in the amount of precipitation reduced the soil moisture and Rs by -12% and -6%, respectively, but did not alter Q10. Overall, our synthesis suggests that soil moisture and Rs tend to be more sensitive to increased precipitation in more arid areas and more responsive to decreased precipitation in more humid areas. The responses of Rs and Q10 were predominantly driven by precipitation-induced changes in the soil moisture, whereas changes in the soil temperature had limited impacts. Finally, our synthesis of prolonged drought experiments also emphasizes the importance of the timing and frequency of precipitation events on ecosystem C cycles. Given these findings, we urge future studies to focus on manipulating the frequency, intensity, and seasonality of precipitation with an aim to improving our ability to predict and model feedback between Rs and climate change.© 2015 John Wiley & Sons Ltd.

. Respiration and leaching are two main processes responsible for soil carbon loss. While the former has received considerable research attention, studies examining leaching processes are limited, especially in semiarid grasslands due to low precipitation. Climate change may increase the extreme precipitation event (EPE) frequency in arid and semiarid regions, potentially enhancing soil carbon loss through leaching and respiration. Here we incubated soil columns of three typical grassland soils from Inner Mongolia and the Qinghai–Tibetan Plateau and examined the effect of simulated EPEs on soil carbon loss through respiration and leaching. EPEs induced a transient increase in CO2 release through soil respiration, equivalent to 32 and 72 % of the net ecosystem productivity (NEP) in the temperate grasslands (Xilinhot and Keqi) and 7 % of NEP in the alpine grasslands (Gangcha). By comparison, leaching loss of soil carbon accounted for 290, 120, and 15 % of NEP at the corresponding sites, respectively, with dissolved inorganic carbon (DIC, biogenic DIC + lithogenic DIC) as the main form of carbon loss in the alkaline soils. Moreover, DIC loss increased with recurring EPEs in the soil with the highest pH due to an elevated contribution of dissolved CO2 from organic carbon degradation (indicated by DIC-δ13C). These results highlight the fact that leaching loss of soil carbon (particularly in the form of DIC) is important in the regional carbon budget of arid and semiarid grasslands and also imply that SOC mineralization in alkaline soils might be underestimated if only measured as CO2 emission from soils into the atmosphere. With a projected increase in EPEs under climate change, soil carbon leaching processes and the influencing factors warrant a better understanding and should be incorporated into soil carbon models when estimating carbon balance in grassland ecosystems.\n

<p><em>Aims </em>Our objective was to examine the effects of global warming inducing environmental and biological changes on soil respiration of desert steppe.</br><em>Methods</em> We used infrared heaters to carry out the interactive simulation of warming and increasing precipitation in a desert steppe of Inner Mongolia from June to September 2011. Our experimental design was set up with two temperature levels (control and warming) and three precipitation treatments (control, 15% and 30% increase of the average precipitation during 1987&ndash;2007), using a complete randomized block arrangement. Soil respiration rate was measured by a LI-8100 carbon flux system in these six different treatments. We analyzed the relationships between soil respiration and environmental factors, aboveground biomass, and belowground biomass at different soil layers (0&ndash;10, 10&ndash;20 and 0&ndash;20 cm).</br><em>Important findings</em> Soil respiration in the desert steppe reached its peak value in the middle of the growing season. The average soil respiration rate of the desert steppe from July to August was 1.35 &mu;mol CO₂&middot;m^&ndash;2&middot;s^&ndash;1. The soil respiration rate was 2.08 and 0.63 &mu;mol CO₂&middot;m^&ndash;2&middot;s^&ndash;1 in July and August, respectively. Increasing soil moisture and temperature significantly influenced daily soil respiration, but their interaction had no significant effect on soil respiration. Soil moisture had greater impact on monthly soil respiration than soil temperature. Soil respiration rate showed a power function relationship with belowground biomass at different soil depths. The belowground biomass at 0&ndash;10 cm soil was the major part of the belowground biomass and could explain more variation of soil respiration rate (79.2%) than that at 10&ndash;20 cm (31.6%). Under the future climatic changes scenarios, soil moisture was a principal environmental factor affecting plant biomass, while belowground biomass was a major biological factor controlling soil respiration in the desert steppe. Soil moisture might control the heterogeneity of soil&nbsp;respiration by influencing the distribution of belowground biomass at different soil depths.</p>

利用红外辐射增温装置模拟短期持续增温和降水增加交互作用对内蒙古荒漠草原土壤呼吸作用的影响, 结果表明: 土壤含水量对月土壤呼吸的影响显著大于土壤温度增加的影响, 生长旺季的月土壤呼吸显著大于生长末季; 土壤温度和水分增加都显著影响日土壤呼吸, 但二者的交互作用对土壤呼吸无显著影响。荒漠草原7?8月平均土壤呼吸速率为1.35 &mu;mol CO₂&middot;m^&ndash;2&middot;s^&ndash;1, 7月份为2.08 &mu;mol CO₂&middot;m^&ndash;2&middot;s^&ndash;1, 8月份为0.63 &mu;mol CO₂&middot;m^&ndash;2&middot;s^&ndash;1。土壤呼吸与地下各层根系生物量呈幂函数关系, 0?10 cm土层的根系生物量对土壤呼吸的解释率(79.2%)明显高于10?20 cm土层的解释率(31.6%)。0&ndash;10 cm土层的根系生物量是根系生物量的主体, 根系生物量对土壤呼吸的影响具有层次性。在未来全球变暖和降水格局变化的情景下, 荒漠草原土壤水分含量是影响生物量的主导环境因子, 而根系生物量的差异是造成土壤呼吸异质性的主要生物因素, 土壤含水量可通过影响根系生物量控制土壤呼吸的异质性。

Anthropogenic-based disturbances may alter peatland soil-plant causal associations and their ability to sequester carbon. Likewise, it is unclear how the vegetation attributes are linked with different soil C decomposition-based pools (i.e., live moss, debris, and poorly- to highly-decomposed peat) under grassing and harvesting conditions. Therefore, we aimed to assess the relationships between aboveground vegetation attributes and belowground C pools in a Northern Patagonian peatland of with disturbed and undisturbed areas. We used ordination to depict the main C pool and floristic gradients and structural equation modeling (SEM) to explore the direct and indirect relationships among these variables. In addition, we evaluated whether attributes derived from plant functional types (PFTs) are better suited to predict soil C pools than attributes derived from species gradients. We found that the floristic composition of the peatland can be classified into three categories that follow the C pool gradient. These categories correspond to (1) woody species, such as, (2) water-logged species like, and (3) grasslands. We depicted that these classes are reliable indicators of soil C decomposition stages. However, the relationships change between management. We found a clear statistical trend showing a decrease of live moss, debris, and poorly-decomposed C pools in the disturbed area. We also depicted that plant diversity, plant height, and PFT composition were reliable indicators of C decomposition only under undisturbed conditions, while the species-based attributes consistently yielded better overall results predicting soil C pools than PFT-based attributes. Our results imply that managed peatlands of Northern Patagonia with active grassing and harvesting activities, even if small-scaled, will significantly alter their future C sequestration capacities by decreasing their live and poorly-decomposed components. Finally, aboveground vegetation attributes cannot be used as proxies of soil C decomposition in disturbed peatlands as they no longer relate to decomposition stages.© 2022 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.

Anthropogenic climate change has emerged as a critical environmental problem, prompting frequent investigations into its consequences for various ecological systems. Few studies, however, have explored the effect of climate change on ecological stability and the underlying mechanisms. We conduct a field experiment to assess the influence of warming and altered precipitation on the temporal stability of plant community biomass in an alpine grassland located on the Tibetan Plateau. We find that whereas precipitation alteration does not influence biomass temporal stability, warming lowers stability through reducing the degree of species asynchrony. Importantly, biomass temporal stability is not influenced by plant species diversity, but is largely determined by the temporal stability of dominant species and asynchronous population dynamics among the coexisting species. Our findings suggest that ongoing and future climate change may alter stability properties of ecological communities, potentially hindering their ability to provide ecosystem services for humanity.

Changing precipitation regimes could have profound influences on carbon (C) cycle in the biosphere. However, how soil C release from terrestrial ecosystems responds to changing seasonal distribution of precipitation remains unclear. A field experiment was conducted for 4 years (2013-2016) to examine the effects of altered precipitation distributions in the growing season on soil respiration in a temperate steppe in the Mongolian Plateau. Over the 4 years, both advanced and delayed precipitation peaks suppressed soil respiration, and the reductions mainly occurred in August. The decreased soil respiration could be primarily attributable to water stress and subsequently limited plant growth (community cover and belowground net primary productivity) and soil microbial activities in the middle growing season, suggesting that precipitation amount in the middle growing season is more important than that in the early, late, or whole growing seasons in regulating soil C release in grasslands. The observations of the additive effects of advanced and delayed precipitation peaks indicate semiarid grasslands will release less C through soil respiratory processes under the projected seasonal redistribution of precipitation in the future. Our findings highlight the potential role of intra-annual redistribution of precipitation in regulating ecosystem C cycling in arid and semiarid regions.© 2017 John Wiley & Sons Ltd.

为比较短花针茅（Stipa breviflora）荒漠草原不同放牧强度下不同水分处理对土壤呼吸、根系现存量和根系净生长量的影响，揭示土壤呼吸与地下生物量之间的关系，本研究在内蒙古荒漠草原不同放牧强度试验区进行对比性试验。放牧强度试验采用完全随机区组设计，将50 hm²试验样地分为不放牧、轻度放牧、中度放牧和重度放牧4个梯度，3次重复。每个放牧强度下设有4个不同水分处理（减水50%、自然降水、增水50%和增水100%）。在不同水分处理小区内，采用开路式土壤碳通量测量系统LI-8100测定土壤呼吸速率，用根钻法测定根系现存量，根袋法测定根系净生长量。结果表明：不同放牧强度对土壤呼吸和群落地下生物量没有产生显著性影响（P>0.05）；土壤呼吸速率随着降水的增多显著增加（PPPP<0.05）。因此，在干旱的荒漠草原，水分是影响土壤呼吸和群落生长发育的主要因素。

Long-term precipitation trend is a good indicator of climate and hydrological change. The data from 635 ground stations are used to quantify the temporal trends of precipitation with different intensity in China from 1961 to 2016. These sites are roughly uniformly distributed in the east or west regions of China, while fewer sites exist in the western region. The result shows that precipitation with a rate of &lt;10 mm/day dominates in China, with a fraction of &gt;70%. With a 95% confidence level, there is no significant temporal change of annually averaged precipitation in the whole of China. Seasonally, there are no significant temporal changes except for a robust decreasing trend in autumn. Spatially, significant differences in the temporal trends of precipitation are found among various regions. The increasing trend is the largest in Northwest China, and the decreasing trend is the largest in North China. The annually averaged number of precipitation days shows a decreasing trend in all regions except for Northwest China. Regarding precipitation type, the number of light precipitation days shows a robust decreasing trend for almost all regions, while other types show no significant change. Considering the high frequency, the temporal trends of light precipitation could highly explain the temporal variation of the total precipitation amount in China.

以青藏高原高寒草甸4种主要草地类型为研究对象,分析了不同植被类型土壤的理化性质、土壤微生物数量、土壤酶活性与生态系统功能间的相互关系。结果表明,不同植被类型群落的土壤特性存在明显差异。藏嵩草沼泽化草甸0～40cm土层土壤容重、土壤含水量、土壤有机质、土壤全氮和土壤速效氮含量明显不同于矮嵩草草甸、小嵩草草甸和金露梅灌丛草甸,土壤物理特性的改变(土壤养分、土壤容重、土壤湿度等)会引起植被组成、物种多样性变化;细菌数量和真菌数量与植物群落地上生物量之间存在显著正相关关系(P＜0.05)、放线菌数量与生物量之间的相关性不显著,不同植被类型的群落生物量影响着土壤微生物数量和组成;不同草地类型植物群落地上生物量与土壤酶活性(磷酸酶、过氧化氢酶、蛋白酶、脲酶等)之间存在显著的正相关关系(P＜0.05),土壤酶活性对土壤有机质、腐殖质等的合成起到了积极作用。土壤酶活性的高低不仅影响了群落生物量,同时也影响群落物种多样性(物种丰富度),土壤酶活性的高低通过影响土壤微生物种类和数量、土壤养分含量,从而间接影响群落物种多样性。

Precipitation influences the vulnerability of grassland ecosystems, especially upland grasslands, and soil respiration is critical for carbon cycling in arid grassland ecosystems which typically experience more droughty conditions.

全球气候变化带来降水格局的改变。土壤呼吸是土壤碳库向大气释放CO₂的重要途径, 其对降水变化的响应对陆地生态系统碳循环和全球气候变化进程有着重要的意义。该研究收集了来自全球各地土壤呼吸对降水变化响应的控制试验结果进行分析, 以揭示降水格局变化对土壤呼吸影响的普遍规律和控制机制。结果显示: 增加降水促进土壤呼吸2%-135%, 减少降水抑制土壤呼吸19%-24%, 当降水改变量标准化到所有处理的平均值(当年当地降水量的41%)时, 增加降水促进的土壤呼吸量(49%)显著大于减少降雨抑制的土壤呼吸量(21%)。土壤湿度是降水变化下驱动土壤呼吸改变的主要因子, 其一方面直接影响土壤呼吸, 另一方面通过影响土壤微生物碳库、地上/地下净初级生产力来影响土壤呼吸, 总解释度高达98%。同时土壤呼吸对降水变化的响应程度随着环境温度和降水量发生变化。土壤呼吸对降水增加的敏感性随环境温度的升高没有显著变化, 但对降水减少的敏感性随着环境温度的升高逐渐增强。随着环境降水量的逐渐增加, 土壤呼吸对降水增加和减少的敏感性均呈现下降趋势。说明在未来全球降水格局的改变下, 土壤呼吸对降水变化的响应有很大的区域差异, 受当地气候条件的影响。

The dynamics of soil respiration are crucial in understanding carbon cycling and its feedback to climate change. However, little information exists regarding the response of soil respiration to precipitation variation. To examine the response of soil respiration to precipitation variation through biogeochemical regulation, a manipulative field experiment was conducted along a precipitation gradient (-60%, -40%, -20%, CK = natural precipitation, + 20%, +40% and +60%) in a native desert grassland ecosystem in Inner Mongolia. Plant biomass, total soil carbon and soil respiration were determined across the precipitation treatments during the growing season (from late May to early October) in 2017. Above-ground biomass tended to increase but total soil carbon varied little with an increase in precipitation. Soil respiration exhibited a unimodal curve diurnally in all precipitation treatments, peaking between 09:00 and 13:00, but showed irregular patterns seasonally. Both the daily and seasonal average soil respirations increased with an increase in precipitation (diurnal Rs ranged from 0.37 mu mol m(-2)S(-1 )to 0.75 mu mol m(-2)S(-1); seasonal Rs ranged from 0.43 mu mol m(-2)S(-1) to 0.66 mu mol m(-2)S(-1)). Soil respiration was correlated positively with precipitation-induced change in above-ground plant biomass, but was correlated negatively with precipitation-induced change in total soil carbon. It was concluded that carbon released from the soil increases with an increase in precipitation.

对干旱区优势固沙灌木柠条群落不同微生境（灌丛外和灌丛下）的土壤温度（0 cm、5 cm、10 cm和20 cm剖面深度）进行了连续测定,对比分析了晴天、降水日与灌丛对其微生境土壤温度时空变异的影响。结果表明:降水和植被灌丛对土壤温度均具有显著影响。在无雨日,受灌丛遮阴影响,灌丛外土壤温度明显高于灌丛下相同深度的土壤温度；在降水日,土壤温度主要受降水影响,降水使土壤温度明显降低,灌丛的影响作用减弱,灌丛下和灌丛外同一剖面深度的土壤温度差异较小。无雨日土壤温度日变化呈单峰型正弦曲线,随剖面深度增加,土壤温度振幅逐渐减小,峰值出现时间滞后,土壤温度垂直分布变化呈现4种典型变化曲线。夜间（日落至日出）柠条灌丛下地表温度（0 cm土壤温度）比灌丛外地表温度略高。降水日土壤温度日变化随降水过程的持续呈逐渐递减趋势,土壤温度垂直分布变化表现为随深度增加而递增的趋势。

Change in precipitation pattern and increase in atmospheric nitrogen (N) deposition are two important consequences of global change. Soil carbon (C)&#x02236;N&#x02236;phosphorus (P) ecological stoichiometry could reflect soil organic C level and N and P supply and thus would be closely related to plant growth. Previous studies have reported that both of the changes in precipitation and N deposition may lead to the decoupling of soil C&#x02236;N&#x02236;P ecological stoichiometry. In order to better understand whether the changes in soil C&#x02236;N&#x02236;P ecological stoichiometry could affect plant community composition under changing precipitation regimes and increasing atmospheric N deposition, we conducted a field experiment in a desert steppe of Ningxia, northwestern China, involving five precipitation treatments (50% reduction in precipitation, 30% reduction in precipitation, natural precipitation, 30% increase in precipitation, and 50% increase in precipitation) and two N addition treatments (0 and 5 g&#x000b7;m^-2&#x000b7;yr^-1) in 2017, and primarily explored the changes in both soil C&#x02236;N&#x02236;P ecological stoichiometry and plant community composition and their relationships in August, 2018. It was found that increased precipitation led to decreases in soil organic C, total N, and N&#x02236;P, whereas N addition and its interaction with precipitation had little influences on soil C&#x02236;N&#x02236;P ecological stoichiometry; a moderate increase in precipitation stimulated the growth of most plants and thus increased community diversity. An excessive increase in precipitation resulted in a sharp increase of <em>Artemisia scoparia</em> biomass, combined with the positive effects of N addition, resulting in a reduction of community diversity. To a certain extent, soil water content, total N, organic C, and N&#x02236;P were closely related to plant population biomass, while soil water content, organic C, C&#x02236;P, and C&#x02236;N had closer relationships with diversity indices. Taken together, the results above indicate that precipitation could change N and P relationships between soil supply and plant demand through regulating soil water availability, thus changing plant growth strategy and community diversity; short-term N addition had little effect on soil nutrient availability, consequently, a long-term in situ experiment is needed to further explore mechanisms influencing soil C&#x02236;N&#x02236;P stoichiometric balance effects on plant community composition under N addition and the interaction between these effects and precipitation change.

为了解降水格局改变和大气氮(N)沉降增加背景下土壤碳(C)&#x02236;N&#x02236;磷(P)平衡关系的改变是否会影响到荒漠草原植被群落组成, 基于2017年在宁夏荒漠草原设立的降水量(降水量减少50%、降水量减少30%、自然降水量、降水量增加30%和降水量增加50%)、N添加(0和5 g&#x000b7;m^-2&#x000b7;yr^-1)及其交互作用的野外试验, 初步分析了土壤C&#x02236;N&#x02236;P生态化学计量特征和植物群落组成的变化趋势以及二者的关系。结果表明, 增加降水量降低了土壤有机C、全N和N&#x02236;P。N添加及其与降水量的交互作用对土壤C&#x02236;N&#x02236;P生态化学计量特征的影响较小; 适量增加降水量刺激了多数植物生长, 提高了群落多样性。过量增加降水量导致猪毛蒿种群生物量急增, 且N添加对降水量效应有促进作用, 从而降低了群落多样性; 土壤含水量、全N、有机C和N&#x02236;P与种群生物量关系较为密切, 土壤含水量、有机C、C&#x02236;P和C&#x02236;N与多样性指数存在较强的相关关系。以上结果意味着降水量会通过调控土壤水分有效性, 改变土壤与植物之间N和P的满足程度, 从而对植物生长策略和群落多样性产生影响; 短期N添加对土壤养分有效性影响较小。因此, 还需通过长期的原位试验, 对N添加及其与降水量交互作用下土壤C&#x02236;N&#x02236;P计量平衡与植物群落组成的关系进行深入探讨。