Grazing weakens temporal stabilizing effects of diversity in the Eurasian steppe

Many biodiversity experiments have demonstrated that plant diversity can stabilize productivity in experimental grasslands. However, less is known about how diversity–stability relationships are mediated by grazing. Grazing is known for causing species losses, but its effects on plant functional groups (PFGs) composition and species asynchrony, which are closely correlated with ecosystem stability, remain unclear. We conducted a six‐year grazing experiment in a semi‐arid steppe, using seven levels of grazing intensity (0, 1.5, 3.0, 4.5, 6.0, 7.5, and 9.0 sheep per hectare) and two grazing systems (i.e., a traditional, continuous grazing system during the growing period (TGS), and a mixed one rotating grazing and mowing annually (MGS)), to examine the effects of grazing system and grazing intensity on the abundance and composition of PFGs and diversity–stability relationships. Ecosystem stability was similar between mixed and continuous grazing treatments. However, within the two grazing systems, stability was maintained through different pathways, that is, along with grazing intensity, persistence biomass variations in MGS, and compensatory interactions of PFGs in their biomass variations in TGS. Ecosystem temporal stability was not decreased by species loss but rather remain unchanged by the strong compensatory effects between PFGs, or a higher grazing‐induced decrease in species asynchrony at higher diversity, and a higher grazing‐induced increase in the temporal variation of productivity in diverse communities. Ecosystem stability of aboveground net primary production was not related to species richness in both grazing systems. High grazing intensity weakened the temporal stabilizing effects of diversity in this semi‐arid grassland. Our results demonstrate that the productivity of dominant PFGs is more important than species richness for maximizing stability in this system. This study distinguishes grazing intensity and grazing system from diversity effects on the temporal stability, highlighting the need to better understand how grazing regulates ecosystem stability, plant diversity, and their synergic relationships.     

放牧对短花针茅荒漠草原植物多样性的影响

放牧干扰对草原植物多样性影响机制是放牧生态学研究的核心问题。以内蒙古锡林郭勒盟苏尼特右旗的短花针茅荒漠草原的长期放牧控制实验为平台,系统研究了放牧调控下植物多样性随组织尺度转换的影响,为荒漠草原植物多样性尺度推绎提供理论基础。结果显示:1)现存草地物种数未放牧最高,适度放牧次之,重度放牧最低,差异体现在多年生杂类草和一年生草本2个功能群上,且各功能群的权重基本不受放牧强度影响;2)群落尺度,放牧强度没有显著影响丰富度指数,未放牧小区的植物Simpson生态优势度指数、Shannon-Wiener物种多样性指数与Pielou均匀度指数大于适度放牧小区,显著大于重度放牧小区(P0.05);功能群尺度,多年生禾草与一年生草本的多样性指数对放牧无显著响应,多年生杂类草的多样性指数未放牧小区最高,适度放牧小区次之。3)Godron群落稳定性指数显示,适度放牧的小区稳定性高于未放牧小区和重度放牧小区。研究表明,放牧强度的上升使短花针茅荒漠草原不同组织尺度植物多样性降低,但群落稳定性结果显示适度放牧的草地表现出了更高的稳定性,植物多样性与稳定性的权衡将是合理制定区域科学放牧强度的重要途径。     

Moderate grazing promotes the root biomass in Kobresia meadow on the northern Qinghai–Tibet Plateau

Grazing is an important modulator of both plant productivity and biodiversity in grassland community, yet how to determine a suitable grazing intensity in alpine grassland is still controversy. Here, we explore the effects of different grazing intensities on plant biomass and species composition, both at community level and functional group level, and examines the productivity–species richness relationship under four grazing patterns: no grazing (CK), light grazing (LG), moderate grazing, (MG) and heavy grazing (HG), attempt to determine a suitable grazing intensity in alpine grassland. The results were as follows. The total aboveground biomass (AGB) reduced with increasing grazing intensity, and the response of plant functional groups was different. AGB of both sedges and legumes increased from MG to HG, while the AGB of forbs reduced sharply and the grass AGB remained steady. There was a significant positive relationship between productivity and species richness both at community level and functional group level. In contrast, the belowground biomass (BGB) showed a unimodal relationship from CK to HG, peaking in MG (8,297.72 ± 621.29 g/m²). Interestingly, the grassland community tends to allocate more root biomass to the upper soil layer under increasing grazing intensities. Our results suggesting that moderate levels of disturbance may be the optimal grassland management strategy for alpine meadow in terms of root production.     

Does the intensive grazing and aridity change the relations between the dominant shrub Artemisia kopetdaghensis and plants under its canopies?

The interspecific plant interactions along grazing and aridity stress gradients represent a major research issue in plant ecology. However, the combined effects of these two factors on plant–plant interactions have been poorly studied in the northeast of Iran. To fill this knowledge gap, 144 plots were established in 12 study sites with different grazing intensities (high vs. low) and climatic characteristics (arid vs. semiarid) in northeastern Iran. A dominant shrub, Artemisia kopetdaghensis, was selected as the model species. Further, we studied changes in plant life strategies along the combined grazing and aridity stress gradients. In this study, we used relative interaction indices calculated for species richness, Shannon diversity, and species cover to determine plant–plant interactions using linear mixed‐effect models (LMM). The indicator species analysis was used to identify the indicator species for the undercanopy of shrub and for the adjacent open areas. The combined effects of grazing and aridity affected the plant–plant interactions and plant life strategies (CSR) of indicator species. A. kopetdaghensis showed the highest facilitation effect under high stress conditions (high grazing, high aridity), which turned into competition under the low stress conditions (low grazing, low aridity). In the arid region, the canopy of the shrub protected ruderals, annual forbs, and grasses in both high and low grazing intensities. In the semiarid region and high grazing intensity (low aridity/high grazing), the shrubs protected mostly perennial forbs with C‐strategy. Our findings highlight the importance of context‐dependent shrub management to restore the vegetation damaged by the intensive grazing.     

Grazing effects on plant functional group diversity in Mediterranean shrublands

Grazing is one of the prevalent human activities that even today are taking place inside protected areas with direct or indirect effects on ecosystems. In this study we analyzed the effects of grazing on plant species diversity, plant functional group (PFG) diversity and community composition of shrublands. We analyzed plant diversity data from 582 sampling plots located in 66 protected areas of the Greek Natura 2000 network, containing in total 1102 plant species and subspecies. We also classified a priori all plant species in seven PFGs: annual forbs, annual grasses/sedges, legumes, perennial forbs, perennial grasses/sedges, small shrubs and tall shrubs. For each site, grazing intensity was estimated in four classes (no grazing, low, medium and high grazing intensity). We found that, at the spatial and temporal scale of this study, as grazing intensity increased, so did total species richness. However, each PFG displayed a different response to grazing. Short-lived species (annual grasses or forbs and legumes) benefited from grazing and their species richness and proportion in the community increased with grazing. Perennial grasses and forbs species richness increased with grazing intensity, but their dominance decreased, since their proportion in the community declined. Short shrub species richness remained unaffected by grazing, while tall shrub diversity decreased. Finally, in sites without grazing the spatial pattern of species richness of the different PFGs was not congruent with each other, while in grazed sites they were significantly positively correlated (with the exception of tall shrubs). This finding may imply that grazing is a selective pressure organizing the community structure, and imposing a certain contribution of each PFG. So, in Mediterranean shrublands in protected areas with a long historical record of grazing, it seems that grazing promotes species diversity and its continuation on a portion of the landscape may be a necessary part of an effective management plan.     

Plant community responses to increased precipitation and belowground litter addition: Evidence from a 5‐year semiarid grassland experiment

Global climate change is predicted to stimulate primary production and consequently increases litter inputs. Changing precipitation regimes together with enhanced litter inputs may affect plant community composition and structure, with consequent influence on diversity and ecosystem functioning. Responses of plant community to increased precipitation and belowground litter addition were examined lasting 5 years in a semiarid temperate grassland of northeastern China. Increased precipitation enhanced community species richness and abundance of annuals by 16.8% and 44%, but litter addition suppressed them by 25% and 54.5% after 5 years, respectively. During the study period, perennial rhizome grasses and forbs had consistent negative relationship under ambient plots, whereas positive relationship between the two functional groups was found under litter addition plots after 5 years. In addition, increased precipitation and litter addition showed significant interaction on community composition, because litter addition significantly increased biomass and abundance of rhizome grasses under increased precipitation plots but had no effect under ambient precipitation levels. Our findings emphasize the importance of water availability in modulating the responses of plants community to potentially enhanced litter inputs in the semiarid temperate grassland.     

Grassland invaders and their mycorrhizal symbionts: a study across climate and invasion gradients

Controlled experiments show that arbuscular mycorrhizal fungi (AMF) can increase competitiveness of exotic plants, potentially increasing invasion success. We surveyed AMF abundance and community composition in Centaurea stoebe and Potentilla recta invasions in the western USA to assess whether patterns were consistent with mycorrhizal-mediated invasions. We asked whether (1) AMF abundance and community composition differ between native and exotic forbs, (2) associations between native plants and AMF shift with invading exotic plants, and (3) AMF abundance and/or community composition differ in areas where exotic plants are highly invasive and in areas where they are not. We collected soil and roots from invaded and native forb communities along invasion gradients and in regions with different invasion densities. We used AMF root colonization as a measure of AMF abundance and characterized AMF communities in roots using 454-sequencing of the LSU-rDNA region. All plants were highly colonized (>60%), but exotic forbs tended to be more colonized than natives (P < 0.001). We identified 30 AMF operational taxonomic units (OTUs) across sites, and community composition was best predicted by abiotic factors (soil texture, pH). Two OTUs in the genera Glomus and Rhizophagus dominated in most communities, and their dominance increased with invasion density (r = 0.57, P = 0.010), while overall OTU richness decreased with invasion density (r = −0.61, P = 0.006). Samples along P. recta invasion gradients revealed small and reciprocal shifts in AMF communities with >45% fungal OTUs shared between neighboring native and P. recta plants. Overall, we observed significant, but modest, differences in AMF colonization and communities between co-occurring exotic and native forbs and among exotic forbs across regions that differ in invasion pressure. While experimental manipulations are required to assess functional consequences, the observed patterns are not consistent with those expected from strong mycorrhizal-mediated invasions.     

不同载畜率对荒漠草原群落结构和功能群生产力的影响

采用随机区组试验研究了内蒙古高原荒漠草原亚带短花针茅(S tip a brev if lora)草原群落不同载畜率对草原群落结构和功能群生产力的影响。结果表明:随着载畜率的增加,群落的植物种数逐渐减少,在每个载畜率水平下,冷蒿(A rtem isia f rig id a)占有绝对优势地位,优势度为35.66%~41.95%;群落的地上生物量随载畜率的增加而降低,各功能群地上生物量组成中,灌木类处于主体地位,分别占据了群落68%(CK)、77.40%(LG)、73.25%(M G)、76.91%(HG)的生物量;在植物生活型功能组成中,灌木类和杂类草、多年生丛生禾草和杂类草功能群,在生物量上具有生态互补效应(n iche com p lem en tary effect)。     

·荒漠草地植物多样性对草食动物采食的响应机制

草食动物采食对草地植物多样性和生态系统功能的影响机制是放牧生态学研究的核心问题。该研究以内蒙古锡林郭勒盟苏尼特右旗荒漠草原的长期放牧控制实验为平台, 从既有草地植物多样性和动物偏食性两个层面系统地研究了荒漠草地植物多样性对草食动物采食的响应机制。结果显示: 1)荒漠草地植物对草食动物采食呈现4种响应模式: 放牧“隐没种”、放牧“敏感种”、放牧“无感种”、“绝对优势种”; 2)在群落尺度上, 物种多样性指数随放牧强度增加而减少, 与不放牧小区相比, 重度放牧(HG)与适度放牧(MG)小区植物多样性均下降, 且这一规律同样适用于功能群多样性, 灌木半灌木这一功能群内物种多样性对放牧干扰较敏感; 3)在草地既有植物的基础上, 以不放牧小区为参考系, 草食动物对植物功能群偏食性的排序为: 一二年生草本(AB) >多年生杂类草(PF) >灌木半灌木(SS) >多年生禾草(PG), 且偏食性物种主要分布于AB和PF中; 4)植物多样性与动物偏食性基本呈显著负相关关系(p < 0.05)。     

Impacts of grazing intensity and increased precipitation on a grasshopper assemblage (Orthoptera: Acrididae) in a meadow steppe

1. Grasshoppers are dominant herbivores in grassland ecosystems, and many studies have examined how grazing by large herbivores and precipitation patterns individually influence the dynamics of grassland grasshopper assemblages, but their combined effects are largely unknown. 2. In this study, grazing intensities (ungrazed, moderate, and heavy) were manipulated and precipitation (ambient and increased amount of rainfall) altered in a field experiment to test the effects of grazing and altered precipitation on a grasshopper community in a meadow steppe in northeastern China. 3. It was found that grasshopper species richness did not change according to different grazing intensities under ambient precipitation, but was significantly higher (by 38.1%) in moderate grazing intensities under increased precipitation. Grasshopper abundance increased considerably with increasing grazing intensities in ambient precipitation treatments; however, grasshopper abundance in heavy grazing intensities was significantly lower (by 32.9%) than in the other two grazing intensities under increased precipitation. Moreover, the responses of grasshopper abundance to grazing under altered precipitation were species‐specific. 4. Grazing effects on grasshopper species diversity were mediated through the species richness and biomass of grasses (food resources), but the effects on grasshopper abundance were mediated through plant height (vegetation structure) under altered precipitation. 5. These results suggest that appropriate grazing by large herbivores would be considered as beneficial management practices for maintaining grasshopper diversity and abundance under conditions of increased precipitation in grassland ecosystems. Additionally, greater attention should be paid to the population dynamics of different grasshopper species to better understand the responses of grasslands to grazing and altered precipitation.     

Land use and drought interactively affect interspecific competition and species diversity at the local scale in a semiarid steppe ecosystem

Few studies have considered interactive effects of grazing and drought on species composition and the relative contribution of species to total biomass, although it is important to understand the short-term dynamics and community succession in grazed ecosystems. We monitored species diversity and relative biomass contribution at one site protected from grazing since 1979 (UG79), and at winter grazing (WG) and heavily grazed (HG) sites. Continuous heavy grazing resulted in lower plant height and more but small individuals (tillers or stolons). Drought significantly reduced total plant density on all sites. Grazing affected species diversity more than drought. Species richness at site UG79 was significantly higher than at sites WG and HG, while drought only tended to reduce species diversity. Drought stress and grazing disturbance interactively controlled species competition and functional groups. Both perennial grasses and forbs had greater contribution to total biomass at site UG79, and perennial grasses contributed more than 97% of total biomass at site WG. The contribution to total biomass of annual forbs and semi-shrubs significantly increased at site HG after two dry years. The significant decrease in Potentilla acaulis and a substantial increase in annual species at this site indicate that the perennial vegetation of this ecosystem is in great danger of extinction under conditions of prolonged drought.     

降水变化对内蒙古典型草原地上生物量的影响

降水格局的变化是气候变化影响干旱和半干旱区草原植物群落结构和功能的关键过程。作为植物群落结构和功能的基本组成单位——植物功能群——对气候变化的响应差异明显。有关不同植物功能群如何响应降水格局的研究, 有助于揭示气候变化对干旱与半干旱区生态系统关键功能与过程稳定性的变异机制。该文利用1982-2015年的典型草原群落地上生物量长期动态监测数据及其所对应的气候数据, 系统揭示降水变化对干旱与半干旱区生态系统生产力的影响。主要研究结果如下: 1) 1982-2015年内蒙古典型草原区降水变化特征明显, 主要表现在降水集中度呈显著的降低趋势; 小降水事件(≤5 mm)明显增多。2)降水变化导致群落生物量呈下降趋势。其中, 多年生丛生禾草的生物量呈上升趋势; 一二年生植物、多年生杂类草、多年生根茎禾类草的生物量均呈下降趋势。3)群落生物量与生长季降水量、降水集中度呈显著的正相关关系。各功能群中, 多年生杂类草、半灌木和生长季降水量呈显著正相关关系, 灌木与降水集中度呈显著负相关关系。4)群落生物量与各等级降水的频率相关性均不显著, 但与I-II类(0.1-10 mm)降水贡献率显著负相关。各功能群中, 多年生杂类草与I类降水(0.1-5.0 mm)的发生频率和降水贡献率均呈显著的负相关关系, 与VI类降水(20-25 mm)的发生频率和贡献率均呈显著的正相关关系。多年生根茎禾类草和VIII类降水(>35 mm)的发生频率和贡献率均呈显著的正相关关系。说明小降水事件的增加将显著降低群落的地上生物量, 小降水事件对干旱、半干旱区植被生长具有重要的生态学意义。     

Nurse species and indirect facilitation through grazing drive plant community functional traits in tropical alpine peatlands

Facilitation among plants mediated by grazers occurs when an unpalatable plant extends its protection against grazing to another plant. This type of indirect facilitation impacts species coexistence and ecosystem functioning in a large array of ecosystems worldwide. It has nonetheless generally been understudied so far in comparison with the role played by direct facilitation among plants. We aimed at providing original data on indirect facilitation at the community scale to determine the extent to which indirect facilitation mediated by grazers can shape plant communities. Such experimental data are expected to contribute to refining the conceptual framework on plant–plant–herbivore interactions in stressful environments. We set up a 2‐year grazing exclusion experiment in tropical alpine peatlands in Bolivia. Those ecosystems depend entirely on a few, structuring cushion‐forming plants (hereafter referred to as “nurse” species), in which associated plant communities develop. Fences have been set over two nurse species with different strategies to cope with grazing (direct vs. indirect defenses), which are expected to lead to different intensities of indirect facilitation for the associated communities. We collected functional traits which are known to vary according to grazing pressure (LDMC, leaf thickness, and maximum height), on both the nurse and their associated plant communities in grazed (and therefore indirect facilitation as well) and ungrazed conditions. We found that the effect of indirectly facilitated on the associated plant communities depended on the functional trait considered. Indirect facilitation decreased the effects of grazing on species relative abundance, mean LDMC, and the convergence of the maximum height distribution of the associated communities, but did not affect mean height or cover. The identity of the nurse species and grazing jointly affected the structure of the associated plant community through indirect facilitation. Our results together with the existing literature suggest that the “grazer–nurse–beneficiary” interaction module can be more complex than expected when evaluated in the field.     

Community species diversity mediates the trade‐off between aboveground and belowground biomass for grasses and forbs in degraded alpine meadow,Tibetan Plateau

Although many empirical experiments have shown that increasing degradation results in lower aboveground biomass (AGB), our knowledge of the magnitude of belowground biomass (BGB) for individual plants is a prerequisite for accurately revealing the biomass trade‐off in degraded grasslands. Here, by linking the AGB and BGB of individual plants, species in the community, and soil properties, we explored the biomass partitioning patterns in different plant functional groups (grasses of Stipa capillacea and forbs of Anaphalis xylorhiza). Our results indicated that 81% and 60% of the biomass trade‐off variations could be explained by environmental factors affecting grasses and forbs, respectively. The change in community species diversity dominated the biomass trade‐off via either direct or indirect effects on soil properties and biomass. However, the community species diversity imparted divergent effects on the biomass trade‐off for grasses (scored at −0.72) and forbs (scored at 0.59). Our findings suggest that plant communities have evolved two contrasting strategies of biomass allocation patterns in degraded grasslands. These are the “conservative” strategy in grasses, in which plants with larger BGB trade‐off depends on gigantic roots for soil resources, and the “opportunistic” strategy in forbs, in which plants can adapt to degraded lands using high variation and optimal biomass allocation.     

Response of dry grassland vegetation to fluctuations in weather conditions: a 9-year case study in Prague (Czech Republic)

The extreme habitats of dry grasslands are suitable for investigations of the response of vegetation to local climate changes. The impact of weather variability on the dynamics of a plant community in a dry grassland was studied. Correlations were found between different functional groups of species and individual species and weather variability. During a 9-year study in five nature reserves in Prague (Czech Republic), the following responses of dry grassland vegetation to weather conditions were observed: (i) wetter conditions, especially in the winter, affected the dominance and species richness of perennial grass species and the decline of rosette plants; (ii) the year-to-year higher temperatures in the winter produced a decline in the dominance of short graminoids and creeping forbs; (iii) spring drought adversely impacted the overall abundance, especially the abundance of dicotyledonous species, and the species richness. However, these relationships may be manifested in different ways in different locations, and in some cases the vegetation of different locations may respond to weather conditions in opposite manners.     

Effects of additional N on herbaceous species of desertified steppe in arid regions of China: a four-year field study

Human-induced nitrogen (N) enrichment is impacting the structure and function of grassland ecosystems, although few studies have been conducted in arid and semi-arid ecosystems under field conditions. Here, a 4-year multi-level N addition experiment under ambient precipitation in a typical temperate desert steppe in arid regions of China was designed to evaluate the impact of N enrichment on the herbaceous vegetation community in desert ecosystems. The results showed that species richness declined in response to N addition during all 4 years, while aboveground biomass increased in the relatively wet year (2007) and decreased in the relatively dry years (2008–2010) according to N addition level, as compared to the control. Plant community composition differed among plant functional groups (PFGs) based on added N. Perennial grasses (PG) benefited more compared with annuals and perennial forbs (PF) from N enrichment in terms of biomass production under conditions of high precipitation in 2007. In relatively dry years, biomass production of all PFGs was strictly dependent on inter- and intra-annual precipitation, which led PG to dominate in 2008 (with a dry spring) and PF to dominate in 2009 and 2010. Our results demonstrate that the impact of N enrichment on the herbaceous vegetation community in desert steppes may be strongly dependent on natural precipitation patterns characterized by shifts in plant community composition, particularly in terms of biomass production.     

内蒙古锡林河流域草原群落植物功能群组成沿水热梯度变化的样带研究

 用样带法调查了草原群落植物功能群组成沿水热梯度的变化。结果表明,随着海拔高度的降低,降水量的减少,热量和干燥度的增加,群落植物生活型功能群组成中,多年生杂类草的相对多度逐渐减少,而多年生丛生禾草的相对多度逐渐增加,多年生丛生禾草对多年生杂类草具有强烈的生态替代作用。在植物生态类群功能群组成中,中旱生植物的作用逐渐减弱,而旱生植物的作用显著增强。草地的利用方式对群落组成具有重要的影响,永久样地和割草场中不耐牧种的相对生物量显著地高于放牧场,而放牧场中耐牧种的相对生物量则显著地高于永久样地和割草场。受草地利用     

Grassland plant functional groups exhibit distinct time-lags in response to historical landscape change

Recent studies have shown significant impacts of past landscapes on present distributions of species, and discussed the existence of an extinction debt. Understanding of the processes building an extinction debt is fundamentally important for explaining present and future diversity patterns of species in fragmented landscapes. Few empirical studies, however, have examined the responses of different plant functional groups (PFGs) to historical landscape changes. We aimed to reveal PFG-based differences in species’ persistence by focusing on their vegetative, reproductive, and dispersal traits. We examined whether the present distributions of PFGs of grassland species in the edges of remnant woodlands established on former semi-natural grasslands are related to the past surrounding landscapes at different time periods and spatial scales. The effects of past landscapes varied significantly among the PFGs. Richness of short, early flowering forbs and tall, late-flowering, wind-dispersed forbs showed significant positive relationships with the surrounding habitat proportions more than 50 years ago (the 1950s) and at wide spatial scales (more than 1 km²). Richness of tall, late-flowering forbs with unassisted and other types of dispersal mechanisms showed positive relationships with the surrounding habitat proportions in recent times (the 1970s) and at smaller spatial scales (0.25 km²). Our results suggested that plant growth form, flowering season and dispersal ability—with additional information on seed bank persistence—can be good indicators for identifying species’ specific sensitivity to surrounding habitat loss. Trait-based approaches can be useful for understanding present and future distributions of grassland species with different persistence strategies in human-modified landscapes.     

Moderate grazing increased alpine meadow soils bacterial abundance and diversity index on the Tibetan Plateau

The response of grassland soil bacterial community characteristics to different grazing intensities is central ecological topics. However, the underlying mechanisms between bacterial abundance, diversity index, and grazing intensity remain unclear. We measured alpine meadow soil bacterial gene richness and diversity index under four grazing intensities using 16S rDNA sequence analysis on the Tibetan Plateau. The results suggest that extreme grazing significantly decreased alpine meadow both bacterial gene abundance and diversity index (p < .05). The lowest operational taxonomic unit numbers were 3,012 ± 447 copies under heavy grazing in the growing season. It was significantly lower than heavy grazing with approximately 3,958 ± 119 copies (p < .05). The Shannon index for medium and high grazing grassland bacterial diversity was slightly higher than for light grazing in the growing season. Furthermore, the lowest index was approximately 9.20 ± 0.50 for extreme grazing of grassland in the growing season. The average bacterial gene abundance and diversity index in the dormancy period were slightly higher than that in the growing season. Soil bulk density, pH, ammonium, and nitrate nitrogen were the main positive factors driving grazed grassland bacterial communities. Our study provides insight into the response of alpine meadows to grazing intensity, demonstrating that moderate grazing increases bacterial community diversity in grazed grasslands.     

Inner Mongolian steppe arbuscular mycorrhizal fungal communities respond more strongly to water availability than to nitrogen fertilization

Plant community productivity and species composition are primarily constrained by water followed by nitrogen (N) availability in the degraded semi‐arid grasslands of Inner Mongolia. However, there is a lack of knowledge on how long‐term N addition and water availability interact to influence the community structure of arbuscular mycorrhizal (AM) fungi, and whether AM fungi contribute to the recovery of degraded grasslands. Soils and roots of the dominant plant species Stipa grandis and Agropyron cristatum were sampled under two water levels and N) rates after 8 years. The abundance and diversity of AM fungi remained relatively resilient after the long‐term addition of water and N. Variation in the AM fungal communities in soils and roots were affected primarily by watering. AM fungal abundance and operational taxonomic unit (OTU) richness were significantly correlated with average aboveground net primary productivity and biomass of plant functional groups. Hyphal length density was significantly correlated with plant richness, the average biomass of S. grandis and perennial forbs. Both water and plant biomass had a considerable influence on the AM fungal assemblages. The tight linkages between AM fungi with aboveground plant productivity highlight the importance of plant–microbe interactions in the productivity and sustainability of these semi‐arid grassland ecosystems.