Grazing occurs over a third of the earth's land surface and may potentially influence the storage of 10(9) Mg year(-1) of greenhouse gases as soil C. Displacement of native herbivores by high densities of livestock has often led to overgrazing and soil C loss. However, it remains unknown whether matching livestock densities to those of native herbivores can yield equivalent soil C sequestration. In the Trans-Himalayas we found that, despite comparable grazing intensities, watersheds converted to pastoralism had 49% lower soil C than watersheds which retain native herbivores. Experimental grazer-exclusion within each watershed type, show that this difference appears to be driven by indirect effects of livestock diet selection, leading to vegetation shifts that lower plant production and reduce likely soil C inputs from vegetation by c. 25 gC m(-2) year(-1). Our results suggest that while accounting for direct impacts (stocking density) is a major step, managing indirect impacts on vegetation composition are equally important in influencing soil C sequestration in grazing ecosystems.

生态系统服务功能的形成和维持机制是近年来生态学研究的热点领域。该文从生态系统服务功能的概念与内涵入手, 分析了生态系统服务功能研究的科学前沿和热点领域, 重点介绍了草地和荒漠生态系统服务功能形成与调控机制联网研究的思路、关键科学问题、研究目标、实验设计、观测指标体系, 以及联网研究取得的重要进展。在此基础上, 对未来草地和荒漠生态系统服务功能研究的重点进行了展望。

The global importance of grasslands is indicated by their extent; they comprise some 26% of total land area and 80% of agriculturally productive land. The majority of grasslands are located in tropical developing countries where they are particularly important to the livelihoods of some one billion poor peoples. Grasslands clearly provide the feed base for grazing livestock and thus numerous high-quality foods, but such livestock also provide products such as fertilizer, transport, traction, fibre and leather. In addition, grasslands provide important services and roles including as water catchments, biodiversity reserves, for cultural and recreational needs, and potentially a carbon sink to alleviate greenhouse gas emissions. Inevitably, such functions may conflict with management for production of livestock products. Much of the increasing global demand for meat and milk, particularly from developing countries, will have to be supplied from grassland ecosystems, and this will provide difficult challenges. Increased production of meat and milk generally requires increased intake of metabolizable energy, and thus increased voluntary intake and/or digestibility of diets selected by grazing animals. These will require more widespread and effective application of improved management. Strategies to improve productivity include fertilizer application, grazing management, greater use of crop by-products, legumes and supplements and manipulation of stocking rate and herbage allowance. However, it is often difficult to predict the efficiency and cost-effectiveness of such strategies, particularly in tropical developing country production systems. Evaluation and on-going adjustment of grazing systems require appropriate and reliable assessment criteria, but these are often lacking. A number of emerging technologies may contribute to timely low-cost acquisition of quantitative information to better understand the soil-pasture-animal interactions and animal management in grassland systems. Development of remote imaging of vegetation, global positioning technology, improved diet markers, near IR spectroscopy and modelling provide improved tools for knowledge-based decisions on the productivity constraints of grazing animals. Individual electronic identification of animals offers opportunities for precision management on an individual animal basis for improved productivity. Improved outcomes in the form of livestock products, services and/or other outcomes from grasslands should be possible, but clearly a diversity of solutions are needed for the vast range of environments and social circumstances of global grasslands.

Semi-nomadic pastoralism was replaced by sedentary pastoralism in Inner Mongolia during the 1960's in response to changes in land use policy and increasing human population. Large increases in numbers of livestock and pastoralist households (11- and 9-fold, respectively) during the past 60 yrs have variously degraded the majority of grasslands in Inner Mongolia (78 M ha) and jeopardize the livelihoods of 24 M human inhabitants. A prevailing strategy for alleviating poverty and grassland degradation emphasizes intensification of livestock production systems to maintain both pastoral livelihoods and large livestock numbers. We consider this strategy unsustainable because maximization of livestock revenue incurs high supplemental feed costs, marginalizes net household income, and promotes larger flock sizes to create a positive feedback loop driving grassland degradation. We offer an alternative strategy that increases both livestock production efficiency and net pastoral income by marketing high quality animal products to an increasing affluent Chinese economy while simultaneously reducing livestock impacts on grasslands. We further caution that this strategy be designed and assessed within a social-ecological framework capable of coordinating market expansion for livestock products, sustainable livestock carrying capacities, modified pastoral perceptions of success, and incentives for ecosystem services to interrupt the positive feedback loop that exists between subsistence pastoralism and grassland degradation in Inner Mongolia. Copyright © 2015. Published by Elsevier Ltd.

为进一步了解氮添加条件下群落功能多样性如何驱动生物量变化, 该研究在位于天山山脉的巴音布鲁克高寒草地开展氮添加实验, 通过连续两年调查群落物种组成并测量常见物种的功能性状, 分析物种多样性、功能多样性及群落水平功能性状的响应模式及其在驱动生物量变化中的相对贡献。结果表明, 短期氮添加同时增加群落地上和地下生物量, 且地上生物量的增加比例高于地下生物量, 氮添加导致功能多样性降低但是物种多样性未发生显著变化; 氮添加增加群落水平上的植株高度和叶片碳含量, 但导致比叶面积、种子质量及叶片磷含量下降; 物种多样性对生物量变化解释非常有限, 而功能多样性与群落水平功能性状可以很好地解释生物量变化, 以上研究结果支持质量比假说。综上, 该研究表明功能多样性与群落水平功能性状比物种多样性对短期氮添加的响应更加迅速, 且两者在解释高寒草地群落生物量对氮添加的响应中起到关键作用。

The continuous increase of livestock production in Inner Mongolia has caused severe degradation of the grassland ecosystems in recent years. Previous grazing experiments have shown a wide range of vegetation responses between the biome types on a global scale, but there is still a lack of sufficient studies to discern the relative responses of a given biome type. We conducted a meta-analysis of vegetation coverage (VC), plant density (PD), total biomass (TB), above-ground biomass (AGB), under-ground biomass (UGB) and Shannon-Weaver Index (SI) in different grassland types in Inner Mongolia obtained under conditions of different grazing intensities and durations. The results showed that grazing decreased VC, TB, AGB, UGB, and PD significantly. Compared to the global and national average values, the negative effects of grazing to steppe biomass in Inner Mongolia were higher than that on the global scale, while less pronounced than that in China. TB of the meadow steppe in Inner Mongolia increased by 40% under moderate grazing intensity and duration because of compensatory growth. SI of the desert and meadow steppe showed negative linear relationships with the grazing intensity in Inner Mongolia. The percentage changes in AGB, PD, and SI to grazing showed quadratic relationships with the mean annual temperature of the experimental year. With increasing mean annual precipitation, the negative effects of grazing on UGB and SI first decreased and then increased, with that of VC and grazing showing a cubic relationship.

Grazing exclusion (GE) is considered to be an effective approach to restore degraded grasslands and to improve their carbon (C) sequestration. However, the C dynamics and related controlling factors in grasslands with GE have not been well characterized. This synthesis examines the dynamics of soil C content and vegetation biomass with the recovery age through synthesizing results of 51 sites in grasslands in China. The results illustrate increases in soil C content and vegetation biomass with GE at most sites. Generally, both soil C content and vegetation biomass arrive at steady state after 15 years of GE. In comparison, the rates of increase in above- and belowground biomass declined exponentially with the age of GE, whereas soil C content declined in a milder (linear) way, implying a lagged response of soil C to the inputs from plant biomass. Mean annual precipitation (MAP) and the rate of soil nitrogen (N) change were the main factors affecting the rate of soil C content change. MAP played a major role at the early stage, whereas the rate of soil N change was the major contributor at the middle and late stages. Our results imply that the national grassland restoration projects in China may be more beneficial for C sequestration in humid regions with high MAP. In addition, increased soil N supply to grasslands with GE at the latter recovery stage may enhance ecosystem C sequestration capacity. © 2015 John Wiley & Sons Ltd.

通过设置不同放牧处理(羊单牧、牛单牧、牛羊混合放牧和不放牧)，研究土壤氮素和优势种克氏针茅根系构型对不同放牧方式的响应。结果表明：放牧14个月后（约2个生长季），牛单牧和牛羊混合放牧显著提高了10～20 cm土层土壤全氮含量，其中牛单牧提高了硝态氮含量，而牛羊混合放牧则以提高有机氮为主；不放牧区的克氏针茅地上生物量显著高于羊单牧、牛单牧和混合放牧区，而地下生物量差异不显著；在放牧处理14个月后，克氏针茅6项根系构型参数5项没有差异，但根系径级分级显示，不放牧区根系直径为2.5～3.5及4.0～4.5 mm的根系长度、体积和表面积显著高于其他放牧区。整体上看，放牧处理14个月，土壤和优势种植物的根系构型参数变化尚不明显，有待于继续观测。

Grasslands are the dominant landscape in China, accounting for 40% of the national land area. Research concerning China's grassland ecosystems can be chronologically summarized into four periods: (i) pre-1950s, preliminary research and survey of grassland vegetation and plant species by Russians, Japanese and Western Europeans, (ii) 1950–1975, exploration and survey of vegetation, soils and topography as part of natural resource inventory programmes by regional and national institutions mainly led by the Chinese Academy of Sciences, (iii) 1976–1995, establishment of field stations for long-term ecological monitoring and studies of ecosystem processes, (iv) 1996–present, comprehensive studies of community dynamics and ecosystem function integrating multi-scale and multidisciplinary approaches and experimental manipulations.

为了更好地理解放牧对草原生态系统物种多度分布格局的影响, 以及常见种和稀有种对维持群落多样性的作用, 以内蒙古典型草原为研究对象, 基于长期放牧控制实验平台(包括7个载畜率水平(0、1.5、3.0、4.5、6.0、7.5、9.0 sheep·hm^-2)和两种地形系统(平地和坡地)), 研究了群落内全部物种、常见种和稀有种的丰富度和多度对放牧强度的响应规律, 并选取对数正态模型、对数级数模型和幂分割模型, 对物种多度数据进行拟合。结果表明: 1)平地系统中, 物种丰富度和多度在低放牧强度下(1.5、3.0 sheep·hm^-2)增加, 而在中、高度放牧强度下(4.5-9.0 sheep·hm^-2)降低, 全部物种的多度分布在大多数放牧强度下符合幂分割模型, 在高放牧强度下也符合对数正态模型; 坡地系统中, 物种丰富度和多度随着放牧强度增加而显著降低, 全部物种的多度分布在各个放牧强度下, 均符合幂分割模型和对数正态模型。2)随着放牧强度增加, 常见种的多度响应趋势与全部物种的响应趋势一致, 其多度分布均符合幂分割模型和对数正态模型; 稀有种的丰富度响应趋势与全部物种的响应趋势一致, 其多度分布符合幂分割模型, 同时也部分符合对数正态和对数级数模型。总之, 适宜的载畜率有利于生物多样性和初级生产力的提高, 平地系统中物种多度的响应在一定程度上支持放牧优化假说; 而坡地系统中不同物种多度的响应差异说明: 确定最佳载畜率时, 还需要考虑地形因素的影响。此外, 模型的拟合结果表明: 生态位分化机制对内蒙古典型草原物种多度分布起着主要作用, 常见种和稀有种通过不同的响应方式共同维持着草原生态系统的物种多样性。

Grazing is one of the main human disturbance factors in alpine grassland on the Qinghai-Tibet Plateau (QTP), which can directly or indirectly influence the community structures and ecological functions of grassland ecosystems. However, despite extensive field grazing experiments, there is currently no consensus on how different grazing management approaches affect alpine grassland diversity, soil carbon (C), and nitrogen (N). Here, we conducted a meta-analysis of 70 peer-reviewed publications to evaluate the general response of 11 variables related to alpine grassland ecosystems plant diversity and ecological functions to grazing. Overall, the results showed that grazing significantly increased the species richness, Shannon–Wiener index, and Pielou evenness index values by 9.89% (95% CI: 2.75–17.09%), 7.28% (95% CI: 1.68–13.62%), and 3.74% (95% CI: 1.40–6.52%), respectively. Aboveground biomass (AGB) and belowground biomass (BGB) decreased, respectively, by 41.91% (95% CI: −50.91 to −32.88%) and 17.68% (95% CI: −26.94 to −8.52%). Soil organic carbon (SOC), soil total nitrogen (TN), soil C:N ratio, and soil moisture decreased by 13.06% (95% CI: −15.88 to −10.15%), 12.62% (95% CI: −13.35 to −8.61%), 3.27% (95% CI: −4.25 to −2.09%), and 20.75% (95% CI: −27.89 to −13.61%), respectively, whereas, soil bulk density and soil pH increased by 17.46% (95% CI: 11.88–24.53%) and 2.24% (95% CI: 1.01–3.64%), respectively. Specifically, moderate grazing, long-durations (>5 years), and winter grazing contributed to increases in the species richness, Shannon–Wiener index, and Pielou evenness index. However, AGB, BGB, SOC, TN, and soil C:N ratios showed a decrease with enhanced grazing intensity. The response ratio of SOC was positively associated with AGB and BGB but was negatively related to the Shannon–Wiener index and Pielou evenness index. Furthermore, the effects of grazing on plant diversity, AGB, BGB, SOC, and TN in alpine grassland varied with grazing duration, grazing season, livestock type, and grassland type. The findings suggest that grazing should synthesize other appropriate grazing patterns, such as seasonal and rotation grazing, and, furthermore, additional research on grazing management of alpine grassland on the QTP is needed in the future.

植物对不同功能性状进行权衡, 通过表型可塑性达到对异质生境的适应是植物的一种生态对策。羊草(Leymus chinensis)是欧亚温带草原东缘的主要优势植物, 研究其对放牧的表型反应对揭示草原生态系统的放牧响应机制具有代表意义。该文以内蒙古呼伦贝尔草甸草原为例, 通过设置不同放牧压力与围封的长期试验, 研究了羊草茎叶功能性状对放牧的可塑性响应模式。结果表明: 1)与长期围封相比, 长期放牧导致羊草茎叶性状显著小型化, 其中, 株高和个体地上生物量分别降低76.82%和89.88%, 但3年短期围封对茎性状影响不显著, 说明羊草表型矮小化现象具有一定的保守性; 2)通过排序构建羊草性状可塑性变化谱, 发现茎质量、总质量、茎高、株高、叶面积等为对放牧响应的敏感性状, 而叶片数、茎粗、叶宽等较为稳定, 为惰性性状; 3)放牧干扰下, 羊草性状可塑性程度与其变异性之间符合y = y₀ + ae^bx拟合关系, 随着植物性状的响应强度增大, 其变异性增强; 4)偏最小二乘法分析发现茎长、株高、叶面积、叶长等性状的投影重要性指标大于1, 对地上生物量变化的解释率为68.6%, 是导致长期放牧下羊草个体生物量降低的主要因子。研究认为, 矮化型变是羊草的避牧适应对策, 在亚稳态下, 通过不同性状的权衡, 充分利用环境资源完成其生活史。

Anthropogenic nitrogen (N) deposition has accelerated terrestrial N cycling at regional and global scales, causing nutrient imbalance in many natural and seminatural ecosystems. How added N affects ecosystems where N is already abundant, and how plants acclimate to chronic N deposition in such circumstances, remains poorly understood. Here, we conducted an experiment employing a decade of N additions to examine ecosystem responses and plant acclimation to added N in an N-rich tropical forest. We found that N additions accelerated soil acidification and reduced biologically available cations (especially Ca and Mg) in soils, but plants maintained foliar nutrient supply at least in part by increasing transpiration while decreasing soil water leaching below the rooting zone. We suggest a hypothesis that cation-deficient plants can adjust to elevated N deposition by increasing transpiration and thereby maintaining nutrient balance. This result suggests that long-term elevated N deposition can alter hydrological cycling in N-rich forest ecosystems.

Dense concentrations of migratory wildebeest leaving the Serengeti Plains in late May 1974 reduced green plant biomass by almost 400 grams per square meter, 85 percent of the initial standing crop. However, this grazing prevented senescence and stimulated net primary productivity of the grasslands. Thomson's gazelles leaving the plains a month later were significantly associated with areas previously grazed by wildebeest, and this association was still evident at the end of the dry season, 6 months later.

Multiple regression analyses were performed on a worldwide 236—site data set compiled from studies that compared species composition, aboveground net primary production (ANPP), root biomass, and soil nutrients of grazed vs. protected, ungrazed sites. The objective was to quantitatively assess factors relating to differential sensitivities of ecosystems to grazing by large herbivores. A key question in this assessment was: Do empirically based, broad—scale relationships correspond to ecological theories of plant—animal interactions and conceptual frameworks for management of the world's grazing lands? Changes in species composition with grazing were primarily a function of ANPP and the evolutionary history of grazing of the site, with level of consumption third in importance. Changes in species composition increased with increasing productivity and with longer, more intense evolutionary histories of grazing. These three variables explained >50% of the variance in the species response of grasslands or grasslands—plus—shrublands to grazing, even though methods of measurement and grazing systems varied among studies. Years of protection from grazing was a significant variable only in the model for shrublands. Similar variables entered models of change in the dominant species with grazing. As with species composition, sensitivities of change in dominant species were greater to varying ecosystem—environmental variables than to varying grazing variables, from low to high values. Increase of the dominant species under grazing were predicted under some conditions, and decreases were more likely among bunch grasses than other life—forms and more likely among perennials than annuals. The response of shrublands was different from that of grasslands, both in terms of species composition and the dominant species. Our analyses support the perception of grazing as a factor in the conversion of grasslands to less desirable shrublands, but also suggest that we may be inadvertently grazing shrublands more intensively than grasslands. Percentage differences in ANPP between grazed and ungrazed sites decreased with increasingly long evolutionary histories of grazing and increased with increasing ANPP, levels of consumption, or years of treatment. Although most effects of grazing on ANPP were negative, some were not, and the statistical models predicted increases in ANPP with grazing under conditions of long evolutionary history, low consumption, few years of treatment, and low ANPP for grasslands—plus—shrublands. The data and the models support the controversial hypothesis that grazing can increase ANPP in some situations. Similar to species variables, percentage differences in ANPP between grazed and ungrazed treatments were more sensitive to varying ecosystem—environmental variables than to varying grazing variables. Within levels not considered to be abusive \"overgrazing,\" the geographical location where grazing occurs may be more important than how many animals are grazed or how intensively an area is grazed. Counter to the commonly held view that grazing negatively impacts root systems, there was no relationship between difference in ANPP with grazing and difference in root mass; as many positive as negative differences occurred, even though most ANPP differences were negative. Further, there was a weak relationship between change in species composition and change in ANPP, and no relationship with root mass, soil organic matter, or soil nitrogen. All three belowground variables displayed both positive and negative values in response to grazing. Current management of much of the world's grazing lands based on species composition criteria may lead to erroneous conclusions concerning the long—term ability of a system to sustain productivity.

As one of the important management practices of grassland ecosystems, grazing has fundamental effects on soil properties, vegetation, and soil microbes. Grazing can thus alter soil respiration (Rs) and the soil carbon cycle, yet its impacts and mechanisms remain unclear.

Global warming and a changing precipitation regime could have a profound impact on ecosystem carbon fluxes, especially in arid and semiarid grasslands where water is limited. A field experiment manipulating temperature and precipitation has been conducted in a temperate steppe in northern China since 2005. A paired, nested experimental design was used, with increased precipitation as the primary factor and warming simulated by infrared radiators as the secondary factor. The results for the first 2 yr showed that gross ecosystem productivity (GEP) was higher than ecosystem respiration, leading to net C sink (measured by net ecosystem CO(2) exchange, NEE) over the growing season in the study site. The interannual variation of NEE resulted from the difference in mean annual precipitation. Experimental warming reduced GEP and NEE, whereas increased precipitation stimulated ecosystem C and water fluxes in both years. Increased precipitation also alleviated the negative effect of experimental warming on NEE. The results demonstrate that water availability plays a dominant role in regulating ecosystem C and water fluxes and their responses to climatic change in the temperate steppe of northern China.

以内蒙古锡林河流域沿水分梯度分布的灰脉苔草(Carex appendiculata)、贝加尔针茅(Stipa baicalensis)、羊草(Leymus chinensis)、大针茅(Stipa grandis)、小叶锦鸡儿(Caragana microphylla)和冷蒿(Artemisia frigida) 6个草地群落为对象, 研究了围封禁牧与放牧样地中144个共有植物种的高度、丛幅面积、茎、叶和株(丛)生物量、茎叶比等性状。结果表明: 1)在个体水平上, 放牧样地中植物的生殖枝高度、营养枝高度、丛幅面积、单株(丛)生物量、茎、叶生物量和茎叶比均显著低于围封禁牧样地, 植物在放牧干扰下表现出明显的小型化现象; 2)在群落水平上, 放牧亦显著降低了群落总生物量和茎、叶生物量; 3)过度放牧显著改变了物种的资源分配策略, 使生物量向叶的分配比例增加, 向茎的分配比例减少。资源优先向同化器官分配可能是植物对长期放牧干扰的一种重要适应对策; 4)轻度放牧对物种的资源分配没有显著影响, 单株(丛)生物量和群落茎、叶及总生物量均表现出增加趋势, 这与过度放牧的影响正好相反。过度放牧引起的植物个体小型化改变了生态系统中物种的资源分配策略, 进而对生态系统功能产生重要的影响。

The challenge to identify the biospheric sinks for about half the total carbon emissions from fossil fuels must include a consideration of below‐ground ecosystem processes as well as those more easily measured above‐ground. Recent studies suggest that tropical grasslands and savannas may contribute more to the ‘missing sink’ than was previously appreciated, perhaps as much as 0.5 Pg (= 0.5 Gt) carbon per annum. The rapid increase in availability of productivity data facilitated by the Internet will be important for future scaling‐up of global change responses, to establish independent lines of evidence about the location and size of carbon sinks.

Grasslands worldwide are suffering from overgrazing, which greatly alters plant community structure and ecosystem functioning. However, the general effects of grazing on community structure and ecosystem function at spatial and temporal scales has rarely been examined synchronously in the same grassland. Here, during 2011-2013, we investigated community structure (cover, height, and species richness) and aboveground biomass (AGB) using 250 paired field sites (grazed vs. fenced) across three vegetation types (meadow, typical, and desert steppes) on the Inner Mongolian Plateau. Grazing, vegetation type, and year all had significant effects on cover, height, species richness, and AGB, although the primary factor influencing variations in these variables was vegetation type. Spatially, grazing significantly reduced the measured variables in meadow and typical steppes, whereas no changes were observed in desert steppe. Temporally, both linear and quadratic relationships were detected between growing season precipitation and cover, height, richness, or AGB, although specific relationships varied among observation years and grazing treatments. In each vegetation type, the observed community properties were significantly correlated with each other, and the shape of the relationship was unaffected by grazing treatment. These findings indicate that vegetation type is the most important factor to be considered in grazing management for this semi-arid grassland.

内蒙古草原是我国北方的重要生态屏障和绿色畜牧业基地, 放牧是草原生态系统的主要利用和管理方式, 在放牧管理中充分发挥生态系统某一项或几项服务和功能最大利用价值时, 往往会与其他服务(功能)发生冲突, 需要权衡多项生态系统服务和功能, 制定合理的放牧管理制度。该研究以内蒙古锡林郭勒典型草原为例, 通过设置不放牧、轻度放牧、中度放牧以及重度放牧的放牧梯度, 从多项生态系统服务和功能权衡的角度比较了最适放牧管理强度。结果显示, 在放牧管理的草地生态系统服务和功能的权衡中, 权衡、协同、不相关关系同时存在, 如土壤呼吸速率与植物群落净生长量、生物多样性与植物群落净光合速率表现为权衡关系, 植物群落净生长量分别与土壤含水量、植物群落净光合速率及草地蒸散速率存在协同关系, 土壤有机碳含量与其他服务或功能间呈不相关关系; 放牧能不同程度地削弱多项生态系统服务及功能间的权衡关系(冲突对立关系); 中度放牧条件下的多项生态系统服务及功能的协同性最佳。

Nitrogen (N) deposition is a component of global change that has considerable impact on belowground carbon (C) dynamics. Plant growth stimulation and alterations of fungal community composition and functions are the main mechanisms driving soil C gains following N deposition in N-limited temperate forests. In N-rich tropical forests, however, N deposition generally has minor effects on plant growth; consequently, C storage in soil may strongly depend on the microbial processes that drive litter and soil organic matter decomposition. Here, we investigated how microbial functions in old-growth tropical forest soil responded to 13 years of N addition at four rates: 0 (Control), 50 (Low-N), 100 (Medium-N), and 150 (High-N) kg N ha  year. Soil organic carbon (SOC) content increased under High-N, corresponding to a 33% decrease in CO efflux, and reductions in relative abundances of bacteria as well as genes responsible for cellulose and chitin degradation. A 113% increase in N O emission was positively correlated with soil acidification and an increase in the relative abundances of denitrification genes (narG and norB). Soil acidification induced by N addition decreased available P concentrations, and was associated with reductions in the relative abundance of phytase. The decreased relative abundance of bacteria and key functional gene groups for C degradation were related to slower SOC decomposition, indicating the key mechanisms driving SOC accumulation in the tropical forest soil subjected to High-N addition. However, changes in microbial functional groups associated with N and P cycling led to coincidentally large increases in N O emissions, and exacerbated soil P deficiency. These two factors partially offset the perceived beneficial effects of N addition on SOC storage in tropical forest soils. These findings suggest a potential to incorporate microbial community and functions into Earth system models considering their effects on greenhouse gas emission, biogeochemical processes, and biodiversity of tropical ecosystems.© 2019 John Wiley & Sons Ltd.

\n\nGrassland ecosystems, an important component of the terrestrial environment, play an essential role in the global carbon cycle and balance. We considered four different grazing intensities on a Stipa breviflora desert steppe: heavy grazing (HG), moderate grazing (MG), light grazing (LG), and an area fenced to exclude livestock grazing as the Control (CK). The analyses of the aboveground biomass, litter, belowground biomass, soil organic carbon and soil light fraction organic carbon were utilised to study the organic carbon stock characteristics in the S. breviflora desert steppe under different grazing intensities. This is important to reveal the mechanisms of grazing impact on carbon processes in the desert steppe, and can provide a theoretical basis for conservation and utilisation of grassland resources. Results showed that the carbon stock was 11.98–44.51 g m–2 in aboveground biomass, 10.43–36.12 g m–2 in plant litters, and 502.30–804.31 g m–2 in belowground biomass (0–40 cm). It was significantly higher in CK than in MG and HG. The carbon stock at 0–40-cm soil depth was 7817.43–9694.16 g m–2, and it was significantly higher in LG than in CK and HG. The total carbon stock in the vegetation-soil system was 8342.14–10494.80 g m–2 under different grazing intensities, with the largest value in LG, followed by MG, CK, and HG. About 90.54–93.71% of the total carbon in grassland ecosystem was reserved in soil. The LG and MG intensities were beneficial to the accumulation of soil organic carbon stock. The soil light fraction organic carbon stock was 484.20–654.62 g m–2 and was the highest under LG intensity. The LG and MG intensities were beneficial for soil nutrient accumulation in the desert steppe.\n

Litter (dead leaves or stems) affects production by conserving soil moisture. However, that role is not clear for grasslands where most precipitation falls during the growing season when the demand for water is high. Our question was: Does litter affect forage production in such an environment? Typical steppe, Inner Mongolia. We examined the role of plant litter in two experiments where litter was either removed or added in a protected or heavily grazed site, respectively, in autumn and in spring in a split plot design. The treatments (control, moderate and heavy litter application) were applied once in five replications but repeated at new locations in each of 3 years. This was done to examine only the direct effect of litter on annual net primary production and selected plant characteristics and not potential secondary effects. We also measured soil moisture and soil temperature. Removing litter caused a reduction in the amount of grass () that was produced, but litter addition caused an inconsistent effect among years, with moderate applications producing the most positive effects. Litter removal resulted in shorter and less dense plants of and, while heavy litter addition in autumn reduced plant height of both and. Litter was effective for enhancing soil moisture status and reducing soil heat units in the typical steppe of Inner Mongolia. Therefore, litter mass may serve as an index of grassland health in such environments.© 2011 International Association for Vegetation Science.

Grasslands provide habitats for living organisms and livelihoods for ~800 million people globally. Many grasslands in developing countries are severely degraded. Some measures have been taken to curb the trend of degradation for decades. It is important to determine how decade-long rejuvenation efforts affected grassland ecosystems. We identified 65 data-rich studies based on six criteria, from >2500 relevant publications, and generated a dataset with 997 rows and 12 variables. The dataset covers different grazing intensities (grazing exclusion, light, moderate, and heavy grazing) and their impacts on plant traits (vegetation coverage, aboveground and root biomass, and plant diversity) and soil physiochemical properties (bulk density, moisture content, organic C, total and available N, total and available P, C:N ratio, and pH). The dataset could be used to (i) quantify the effectiveness of rejuvenation processes by determining the impact on plant community and soil properties, (ii) perform comprehensive analyses to elucidate large-picture effects of grazing management and rejuvenation, and (iii) analyze the impact of grass-climate-soil-human interactions on grassland ecosystem sustainability.

A series of comparative sampling plots were selected to study the effects of different grazing intensities on the biodiversity and productivity of <em>a&nbsp; Leymus chinensis</em> meadow steppe in Inner Mongolia. It was shown that with the increase of grazing intensity, <em>&alpha; </em>diversity index decreased after an initial increase, and had the highest value in light grazing areas, which supported the &lsquo;medium disturbance theory&rsquo;, while <em>&beta;</em> diversity index had an increasing trend. Lesser similarity of plant species was observed under different grazing intensities. There was a significant linear relationship between aboveground net primary productivity (ANPP) and Alatalo evenness index (<em>P</em>&lt;0.05). Grazing and climate had larger effects on the ANPP, but their interactive effect was not significant. No grazing could not maintain grassland health, but healthy grassland could effectively buffer the disturbances of grazing and climate, and maintain its higher productivity and biodiversity.

Grazing is one of the predominant human activities taking place today inside protected areas, with both direct and indirect effects on the vegetation community. We analyzed the effects of grazing intensity on grass composition during four grazing seasons containing 78 plant species belonging to eight plant functional groups, which include perennial tall grass (6 species), perennial short grass (6 species), shrubs (3 species), legumes (9 species), Liliaceae herb (8 species), annual/biennial plants (11 species), perennial short forbs (16 species) and perennial tall forbs (18 species). We estimated grazing intensity at four levels, control, light, moderate and heavy grazing intensity corresponding to 0.00, 0.23, 0.46 and 0.92 animal units ha−1, respectively. We found that each plant functional group showed a different response to grazing intensity. Perennial tall grasses that were dominated by high palatable mesophyte and mesoxerophyte grass showed a significant decrease with grazing intensity, while the medium palatable xerophyte and widespread grasses that were the predominant short perennial increases with grazing intensity. The perennial tall forbs that were dominated by the mesophyte grass also decreased, but the decrease was statistically insignificant. The influence of grazing density on species is also related to soil factors (soil nutrient, soil moisture and soil temperature and soil bulk density). Some functional groups such as tall fescue and Liliaceae herbs, remained stable—which may be related to the changes in the soil environment caused by grazing activities. The findings of this study could provide a standpoint for assessing the current grazing management scenarios and conducting timely adaptive practices to maintain the long-term ability of grassland systems to perform their ecological functions.