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Background: Community species in different grassland types exhibit unique ecological traits and adaptation strategies, influencing the impact of grazing on species diversity at various scales. This study aimed to elucidate the response characteristics and rules of species diversity in different grassland types to grazing intensity by analyzing plant groups and species diversity. Results: Grazing intensity, grassland type, and their interaction significantly affected α, β, and γ diversity. In meadow steppes, α and γ diversity conformed to the intermediate disturbance hypothesis, exhibiting a unimodal trend with increasing grazing intensity—initially increasing and then decreasing. In typical steppes, α, β and γ diversity showed no clear pattern in response to changes in grazing intensity. In desert steppes, α, β and γ diversity consistently declined with increasing grazing intensity. In meadow steppes, dominant and common species were crucial for sustaining community (α diversity) and landscape (γ diversity) diversity, whereas rare species primarily contributed to increased gradient differences (β diversity). In typical steppes, rare species were pivotal for community (α diversity) and landscape (γ diversity) diversity, while dominant and common species were important in reducing gradient differences (β diversity). In desert steppes, rare species were vital for maintaining community diversity (α diversity), dominant species played a key role in reducing gradient differences (β diversity), and common species were important for maintaining landscape-level diversity (γ diversity). Conclusions: The characteristics and patterns of grazing intensity on species diversity at different scales, as well as the dominant plant group influencing plant species diversity at different scales, are controlled by grassland types. These findings highlight the need for tailored management strategies to conserve species diversity in various grassland ecosystems under different grazing pressures. [ABSTRACT FROM AUTHOR]

Abstract Dominant species occupy a pivotal role in plant community, influencing the structure and function of the ecosystem. The spatial distributions of dominant species can react to the effect of different grazing intensities, thereby reflecting their tolerance and adaptive strategies toward grazing. In this study, geostatistical methods were mainly used to study the spatial distribution characteristics of Stipa krylovii Roshev. and Leymus chinensis (Trin.) Tzvel. species at two interval scales (quadrat size 5 m × 5 m, 10 m × 10 m) and two treatments (free grazing, FG, 1.66 sheep·ha− 1·a− 1; control, CK, 0 sheep·ha− 1·a− 1) in typical steppe of Inner Mongolia. A systematic sampling method was used in each 100 m × 100 m representative sample plots to obtain the height, coverage, and density of all species in the community. The results showed that grazing altered the concentrated distribution of S. krylovii and the spatial mosaic distribution pattern of S. krylovii and L. chinensis while having no effect on the spatial clumped distribution of L. chinensis. It also found that the spatial distributions of dominant species are primarily affected by structural factors, and random factors such as long-term grazing led to a transition of S. krylovii from a concentrated distribution to a small patchy random pattern should not be overlooked. Our findings suggest that long-term grazing alters the spatial distribution pattern of dominant species and that adaptive strategies may be the key for maintaining the dominant role of structural factors.

The response of vegetation to climate change on a large scale should be studied at the community level rather than the species level. This necessitates a focused exploration of emerging spatial patterns. Here, we surveyed 264 sites in the Inner Mongolia typical steppe, using the "needling" method to investigate 39,600 clumps formed through the coexistence relationships of dominant species. We found that the effects of slow climate change on grassland communities can be categorized into two general trends: (1) a monotone relationship, characterized by changes in the number of dominant species, compositional diversity, and optimal patch area, and (2) a unimodal relationship, reflected in variations in the number of patches and interspecific associations. The two distinct trends, connected by optimal patch area, concurrently support both the habitat amount hypothesis and the intermediate disturbance hypothesis. These findings suggest that climate change indirectly influences the area and amount of vegetation patches by regulating the arrangement of clumps. Moreover, they indicate that it is the distribution, rather than the number, of species that serves as the front line for plant communities adapting to climate change. [ABSTRACT FROM AUTHOR]

Grassland vegetation phenology has undergone great changes under the influence of climate, which affects ecosystem functions and services. However, the mechanism of preseason climatic factors in driving phenological shifts is unclear. In this study, we determined the start (SOS) and peak (POS) of the growing season for Inner Mongolian grasslands using gross primary productivity data (2000-2018). We investigated the spatiotemporal changes of SOS and POS and elucidated the mechanisms behind these changes by analyzing how these phenological events were influenced by the specific preseason climatic requirements (precipitation, air temperature, and solar radiation). Our results revealed that the SOS significantly advanced at a rate of 0.65 days/a, while the POS was stable across the study area. At the pixel scale, areas with initially later SOS and POS exhibited stronger advanced trends. An earlier SOS and POS were associated with lower thermal requirements, including air temperature and solar radiation. Conversely, a delayed SOS and POS necessitated higher climatic requirements. The impact of preseason precipitation on both SOS and POS demonstrated notable spatial variability. Moreover, the effects of different climatic factors on phenology were not in sync due to regional environmental disparities. Our study provides insight into the mechanisms underlying phenological shifts in grassland ecosystems under climate change. [ABSTRACT FROM AUTHOR]

Dominant species occupy a pivotal role in plant community, influencing the structure and function of the ecosystem. The spatial distributions of dominant species can react to the effect of different grazing intensities, thereby reflecting their tolerance and adaptive strategies toward grazing. In this study, geostatistical methods were mainly used to study the spatial distribution characteristics of Stipa krylovii Roshev. and Leymus chinensis (Trin.) Tzvel. species at two interval scales (quadrat size 5 m × 5 m, 10 m × 10 m) and two treatments (free grazing, FG, 1.66 sheep·ha− 1·a− 1; control, CK, 0 sheep·ha− 1·a− 1) in typical steppe of Inner Mongolia. A systematic sampling method was used in each 100 m × 100 m representative sample plots to obtain the height, coverage, and density of all species in the community. The results showed that grazing altered the concentrated distribution of S. krylovii and the spatial mosaic distribution pattern of S. krylovii and L. chinensis while having no effect on the spatial clumped distribution of L. chinensis. It also found that the spatial distributions of dominant species are primarily affected by structural factors, and random factors such as long-term grazing led to a transition of S. krylovii from a concentrated distribution to a small patchy random pattern should not be overlooked. Our findings suggest that long-term grazing alters the spatial distribution pattern of dominant species and that adaptive strategies may be the key for maintaining the dominant role of structural factors. [ABSTRACT FROM AUTHOR]

Simple Summary: In China, Oedaleus decorus asiaticus is a typical pest that poses a serious threat to Inner Mongolian grasslands. However, the large-scale monitoring and control of grasshopper is still a priority that needs to be improved, so it is particularly important to identify environmental factors that influence locust breeding and growth to reveal the role of environmental factors in the occurrence of the dominant species Oedaleus decorus asiaticus in Inner Mongolia, and to study the potential spatial distribution of Oedaleus decorus asiaticus in typical grasslands. We matched the Maxent model with remote sensing, meteorological, and geographical data to identify environmental factors associated with Oedaleus decorus asiaticus occurrence and to identify possible grasshopper habitats. These efforts could effectively reduce the cost and time investment in grasshopper management. Grasshoppers pose a significant threat to both natural grassland vegetation and crops. Therefore, comprehending the relationship between environmental factors and grasshopper occurrence is of paramount importance. This study integrated machine learning models (Maxent) using the kuenm package to screen MaxEnt models for grasshopper species selection, while simultaneously fitting remote sensing data of major grasshopper breeding areas in Inner Mongolia, China. It investigated the spatial distribution and key factors influencing the occurrence of typical grasshopper species in grassland ecosystems. The modelling results indicate that a typical steppe has a larger suitable area. The soil type, above biomass, altitude, and temperature, predominantly determine the grasshopper occurrence in typical steppes. This study explicitly delineates the disparate impacts of key environmental factors (meteorology, vegetation, soil, and topography) on grasshopper occurrence in typical steppes. Furthermore, it provides a methodology to guide early warning and precautions for grasshopper pest prevention. The findings of this study will be instrumental in formulating future management measures to guarantee grass ecological environment security and the sustainable development of grassland. [ABSTRACT FROM AUTHOR]

Grassland vegetation phenology has undergone great changes under the influence of climate, which affects ecosystem functions and services. However, the mechanism of preseason climatic factors in driving phenological shifts is unclear. In this study, we determined the start (SOS) and peak (POS) of the growing season for Inner Mongolian grasslands using gross primary productivity data (2000–2018). We investigated the spatiotemporal changes of SOS and POS and elucidated the mechanisms behind these changes by analyzing how these phenological events were influenced by the specific preseason climatic requirements (precipitation, air temperature, and solar radiation). Our results revealed that the SOS significantly advanced at a rate of 0.65 days/a, while the POS was stable across the study area. At the pixel scale, areas with initially later SOS and POS exhibited stronger advanced trends. An earlier SOS and POS were associated with lower thermal requirements, including air temperature and solar radiation. Conversely, a delayed SOS and POS necessitated higher climatic requirements. The impact of preseason precipitation on both SOS and POS demonstrated notable spatial variability. Moreover, the effects of different climatic factors on phenology were not in sync due to regional environmental disparities. Our study provides insight into the mechanisms underlying phenological shifts in grassland ecosystems under climate change.

Questions: Although the relationships between biodiversity and individual ecosystem functions under resource enrichment have been extensively studied, there is limited understanding of how resource‐induced changes affect ecosystem multifunctionality and its temporal stability, along with the underlying biological mechanisms. Location: Inner Mongolia, China. Methods: We investigated the impact of biodiversity mechanisms on ecosystem multifunctionality and its temporal stability through a 3‐year field experiment. This experiment involved augmenting growing season precipitation and nitrogen deposition, conducted in a typical steppe ecosystem of Inner Mongolia alongside regular mowing. Results: Our findings revealed that the addition of water (W) and nitrogen (N) had varying effects on ecosystem multifunctionality and its temporal stability. The combination of N and W additions enhanced ecosystem multifunctionality, whereas both W and N + W additions promoted the temporal stability of ecosystem multifunctionality. Structural equation modeling demonstrated that the community‐weighted mean height, in response to nitrogen addition, played a key role in enhancing ecosystem multifunctionality. By contrast, increased species asynchrony because of water addition and greater functional diversity in terms of leaf area contributed to heightened temporal stability of ecosystem multifunctionality. Furthermore, the positive effects of community‐weighted mean height on ecosystem multifunctionality exhibited a gradual increase with rising threshold levels. Conclusions: Our study provides the first evidence of the independent effects of selection, exemplified by community‐weighted mean and complementarity, represented by factors such as species richness, functional diversity and species asynchrony on both ecosystem multifunctionality and its temporal stability. This underscores how global change factors can directly influence ecosystem multifunctionality and its temporal stability while also indirectly modulating biodiversity effects in the short term. Overall, our findings underscore the vital role of biodiversity conservation in enhancing grassland management and the delivery of ecosystem services in the context of global change, particularly in regions subject to extensive mowing. [ABSTRACT FROM AUTHOR]

In many parts of the world, former agricultural sites have been abandoned particularly when productivity is marginal or policies are implemented to develop ecosystem recovery. Understanding the recovery trajectory of soil, plants, and microbes is critical for developing restoration plans and the most effective policies. Here, we evaluated the changes in soil properties, plants, and the bacterial community along a chronosequence of agricultural abandonment (5, 15, and 20 years) in two different types of steppes (desert and typical steppes), respectively, in Inner Mongolia, China. Active farmland and natural grassland were selected as reference sites. In both study sites, soil water content and soil organic carbon content increased, while bulk density and nitrogen decreased across the chronosequence, all becoming comparable to that of natural grassland. Plant diversity, above‐ and below‐ground biomass increased, while perennial graminoids and forbs replaced annuals as the dominant functional groups with the elongation of abandonment. Bacterial diversity increased along the chronosequence in the drier desert steppe, but not in the wetter typical steppe. Over the chronosequence, Acidobacteria, a phyla tending to live in lower carbon conditions, were replaced by Proteobacteria and Actinobacteria, which favor abundant carbon environments. Redundancy analysis shows that soil organic carbon, below‐ground plant biomass, and nitrate were the main factors that driving bacterial community composition. Our results demonstrated that spontaneous recovery without any human disturbance was an effective way for the restoration of arid and semi‐arid grassland ecosystems in Inner Mongolia, and emphasized the importance of soil and plant restoration for the recovery of bacterial community. [ABSTRACT FROM AUTHOR]

Clarifying the response of plant phenology to drought duration is helpful for accurately interpreting and predicting carbon sinks in ecosystems. Based on the response of different phenological periods of the dominant species Stipa krylovii to monthly, seasonal, and semiannual time scale drought in the typical steppe of Inner Mongolia from 1983 to 2018, the results revealed that (1) the start of the growing season (SOS) was characterized by an advance–delay–advance pattern, and the heading stage (HOS), flowering stage (FOS), and end of the growing season (EOS) all showed consistent advanced trends, which provided additional insight into the conclusions of previous studies that found the SOS was advanced in arid and semiarid regions. (2) The response mechanism of the SOS to the timing of drought was not consistent. Among the response mechanism, the SOS was delayed because of the January–February drought at different time scales but advanced because of the April drought at different time scales. The HOS/FOS was delayed by the June–July drought at different time scales, and the EOS was advanced by the August–September drought at different time scales. (3) More importantly, the SOS, HOS, FOS, and EOS were affected by predrought and its persistence, and the effects were greater the closer to the phenological periods that drought occurred. (4) At the monthly scale, droughts in January, June, and August were the critical drought periods affecting the SOS, HOS/FOS, and EOS, while seasonal and semiannual scale droughts in February, June–July, and September were the critical periods affecting the SOS, HOS/FOS, and EOS. The results of this study enrich our understanding of how drought at different time scales affects different phenological periods, providing a basis for improving plant phenological models. [ABSTRACT FROM AUTHOR]

Hyphae of arbuscular mycorrhizal fungi (AMF) in soil often form complex mycorrhizal networks among roots of same or different plant species for transfer of nutrients from one plant to another. However, the effect of soil nitrogen (N) availability on nutrient transfer between different plant species via common mycorrhizal networks (CMNs) has not been experimentally examined. In order to quantify CMN-mediated nutrient transfer between Leymus chinensis (LC) and Cleistogene squarrosa (CS), two systems, i.e. the CS–LC system (CS and LC were donor and recipient, respectively) and the LC–CS system (LC and CS were donor and recipient, respectively) were established. Stable isotopic 15N was applied to track N transfer between heterospecific seedlings connected by CMNs under three levels of soil N additions: no N addition control (N0), N addition with 7 mg/kg (N1) and N addition with 14 mg/kg (N2). In the CS–LC system, the highest rate of AMF colonization and hyphal length density (HLD) were found at N1. In contrast, maximum AMF colonization rate and HLD were recorded at N2 in LC–CS system. Consequently, plant biomass was significantly higher under N1 and N2 levels in CS–LC and LC–CS systems, respectively. Moreover, in CS–LC system, 15N transfer rate ranged from 16% to 61%, with maximum transfer rate at N1. For LC–CS system, 15N transfer rate was much lower, with the maximum occurring at N0. These findings suggest that CMNs could potentially regulate N transfer from a donor to recipient plant depending upon the strength of individual plant carbon sink. [ABSTRACT FROM AUTHOR]

Background and aims: Changes in precipitation profoundly affect ecological processes of steppe ecosystem. To predict the impact of climate changes on plant aboveground net primary productivity (ANPP), it is necessary to understand the direct and indirect effects of precipitation changes on ANPP. Methods: In this study, a precipitation manipulation experiment (i.e., R100: ambient precipitation as a control, R50: 50% of ambient precipitation, R150: 150% of ambient precipitation) was conducted in 2017 in a typical steppe in the western Loess Plateau, China. The ANPP, below-ground biomass, species diversity, vegetation cover, and soil properties of natural grassland were determined in 2020. The structural equation model (SEM) was used to compare the relative contribution of plant and soil properties to ANPP. Results: We found that the vegetation cover, diversity index, community richness, and biomass were positively correlated with precipitation gradients; The soil moisture, soil available potassium (SAK), and soil total phosphorus were significantly affected by changing precipitation. Our findings revealed that changes in precipitation had a significant positive effect on ANPP, which was mainly mediated by community coverage according to SEM. Conclusion: Our results emphasize the importance of vegetation cover in driving the short-term response of ANPP to climate change in the typical steppe. The study is critical to understand the functioning and stability of grassland ecosystems under changing climates. [ABSTRACT FROM AUTHOR]

Although livestock grazing can strongly affect pools and cycles of phosphorus (P) in grassland ecosystems, few studies have examined how grassland management regimes influence the components of the soil P pool. Here, we use a long-term experiment in the Inner Mongolia grassland to examine how grassland management and biotic and abiotic factors affect soil P fractions. The grassland management regimes we studied included a traditional grazing system (continuous grazing, TS), a mixed grazing system (grazing and mowing rotation, MS), and a haymaking system (continuous mowing, HS). Our results showed that traditional grazing accelerated the return of P to ecosystems lost by herbivores and decoupled labile P (i.e., Ca2-P) from soil organic carbon in the topsoil (0–10 cm). Labile P was significantly reduced in the topsoil in HS (− 10%) and MS (− 24%). Mowing promoted the downward movement of soil P and the transformation of O-P to Ca2-P in the topsoil by removing large amounts of biomass and litter. Both grazing and mowing increased Fe-P and Ca10-P concentrations. The amount of labile P in the topsoil was mainly explained by plant properties, whereas the amounts of moderately labile P (Ca8-P, Al-P and Fe-P) and stable P (O-P and Ca10-P) were mainly explained by soil properties. Moreover, shifts in plant community composition resulted in substantial impacts on the soil stable P fractions. Our study demonstrates that long-term continuous grazing is detrimental to the accumulation of available nutrients in soils. Understanding how grazing and mowing affect conversion between P pools could improve adaptive grassland management in the face of global change. [ABSTRACT FROM AUTHOR]

Grazing and mowing are two major land use types in natural grasslands, which have intensive effects on nutrient cycling of grassland ecosystems by deposition of fecaluria nutrient versus removal of hay nutrient. Plant nutrients sensitively respond to the changes in nutrient cycling, while the information on the effects of diverse grazing versus mowing regimes on plant nutrients at different organs or levels are incomplete. A field experiment was conducted to compare the effects of continuous versus rotational grazing, and low versus high mowing frequencies on grassland ecosystems in a semiarid steppe of Inner Mongolia. Plant community characteristics and C, N and P concentrations of dominant species were determined across different managements. We found (i) plant community height and standing biomass significantly decreased with grazing intensity under both continuous and rotational grazing and under annual mowing. (ii) Plant shoot C concentration decreased, whereas N and P concentrations increased with grazing intensity in the two grazing regimes, while these concentrations showed no significant changes in response to the two mowing regimes. (iii) Plant community aboveground C, N and P pools significantly decreased with grazing intensity of both grazing regimes, but did not decrease with mowing frequency in the two mowing regimes. (iv) Plant root C, N and P concentrations showed little significant response to different grazing or mowing regimes, indicating a relatively bigger stability or slower response in plant root nutrients. Our study provides insights into the nutrient cycling in grazing and mowing grassland ecosystems from multiple perspectives. [ABSTRACT FROM AUTHOR]

Soil net nitrogen (N) mineralization is a key biogeochemical process influencing plant available N and net primary productivity in terrestrial ecosystems. However, the spatial variations and controlling factors of soil net N mineralization (RPNM) in arid and semi‐arid grasslands are less studied and unclear.In this study, we investigated the soil RPNM by performing a laboratory incubation experiment. Soil samples were collected from 30 sites in three east–west transects on the Inner Mongolia Plateau (MP), Loess Plateau (LP) and Tibetan Plateau (TP) along a 3200 km arid and semi‐arid grassland gradient, with each transect containing three different grassland types (meadow steppe [MS], typical steppe [TS] and desert steppe [DS], respectively).Results showed that the average RPNM values ranged from −0.37 to 1.29 mg N kg−1 day−1, with a significantly lower RPNM found in the DS (0.08 ± 0.01 mg N kg−1 day−1) compared with those in the MS (0.30 ± 0.03 mg N kg−1 day−1) and in the TS (0.33 ± 0.03 mg N kg−1 day−1) in the MP and LP transects (p < 0.05). This difference could be explained by variations in climatic and soil factors, such as hydrothermal index (HT), the soil pH, soil organic matter (SOM) and precipitation. However, no significant differences in RPNM were found among different grassland types in the TP transect, possibly due to the similarly low microbial activity, as indicated by the microbial biomass carbon values. Across all three grassland transects, HT, SOM and microbial variables were the major factors controlling RPNM, which together explained 20.7% of the variation in RPNM. Further structural equation model analysis indicated HT was an integral predictor of RPNM, directly or indirectly via SOM, under different conditions of precipitation and temperature.Our findings provide field evidence and parameters for biogeochemical cycling to better predict future N transformation processes under changing precipitation and temperature regimes across a wide range of arid and semi‐arid grassland ecosystems. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Simple Summary: Grasshoppers are among the most dangerous agricultural pests of China. However, the monitoring, prediction and control of grasshoppers are complex and difficult. Therefore, it is crucial to detect the key factors affecting the spatial distribution of grasshopper occurrence, understand the role of the environmental factors in grasshopper occurrence, and study whether different laws exist between different grass types. Here we conduct a species–environmental matching model integrated by Maxent model and remote sensing data to identify the spatial distribution of grasshopper occurrence in Inner Mongolia of China, analyze the related environmental variables and detect the most relevant environmental factors for grasshopper occurrence both in typical steppe and meadow steppe. Grasshoppers mainly threaten natural grassland vegetation and crops. Therefore, it is of great significance to understand the relationship between environmental factors and grasshopper occurrence. This paper studies the spatial distribution and key factors of grasshopper occurrence in two grass types by integrating a machine learning model (Maxent) and remote sensing data within the major grasshopper occurrence areas of Inner Mongolia, China. The modelling results demonstrate that the typical steppe has larger suitable area and more proportion for grasshopper living than meadow steppe. The soil type, above biomass, altitude and temperature mainly determine the grasshopper occurrence in typical steppe and meadow steppe. However, the contribution of these factors in the two grass types is significantly different. In addition, related vegetation and meteorological factors affect the different growing stages of grasshoppers between the two grass types. This study clearly defines the different effects of key environmental factors (meteorology, vegetation, soil and topography) for grasshopper occurrence in typical steppe and meadow steppe. It also provides a methodology to guide early warning and precautions for grasshopper pest prevention. The findings of this study will be helpful for future management measures, to ensure grass ecological environment security and the sustainable development of grassland. [ABSTRACT FROM AUTHOR]

The ability of grassland ecosystems to sequester carbon has a great potential to achieve carbon neutralization. Rhizosphere deposition is the most uncertain part of the soil carbon cycle. Since grazing is one of the main ways to utilize grasslands, we conducted experiments to clarify the role of rhizosphere on soil organic carbon (SOC) cycling under grazing in a typical steppe region of Inner Mongolia, China. The experiment was conducted in grasslands under light, moderate, and heavy grazing and in a control (no grazing) in Inner Mongolia, China. Here, we present our analysis of the total soil organic carbon (TOC) and fractions in both the rhizosphere and bulk soil. Light and moderate grazing increased SOC contents in rhizosphere soil, and we found more SOC in rhizosphere soil than in bulk soil. The rhizosphere showed SOC enrichment effect, and this effect increased with an increase in grazing intensity. As grazing intensity increased, microbial biomass carbon content and its percentage of TOC increased in rhizosphere soil and were more stable than those in bulk soil. Dissolved organic carbon content and its percentage of TOC also increased in rhizosphere soil with increasing grazing intensity. These changes were more than those observed in bulk soil. Changes in potentially mineralizable carbon and particulate organic carbon in the rhizosphere and bulk soil were not synchronized in plots under different grazing intensities. Grazing changed the quantity of bacteria, fungi, and actinomycetes, as well as the community structure of soil microbes, in rhizosphere soil and bulk soil. It also influenced the content and structure of SOC. Acidic components (e.g., organic acids) of root exudate reduced the pH in rhizosphere soil to less than that in bulk soil, which may have affected SOC cycling. The results can provide support to improve the ecosystem carbon sink function and help to achieve the goal of carbon peaking/carbon neutral target. [ABSTRACT FROM AUTHOR]

Disturbances, including anthropogenic disturbances, are integral to the maintenance of grassland ecosystems. Most research on anthropogenic disturbances focuses on the effects of intensification, yet cessation of disturbance can have equally important effects on grassland biodiversity and ecosystem functioning. Natural disturbances have largely been replaced by anthropogenic disturbance, which has pronounced effects on community function and structure in grassland ecosystems. It is still unclear how changing disturbance intensity affects community stability and its mechanisms. We examined the temporal stability of above-ground net primary productivity (ANPP) in a seven-year field mowing experiment which included normal disturbance (control, mowing annually at 5 cm stubble height), increasing disturbance (mowing annually at 2 cm stubble height) and ceasing disturbance (no mowing) in a typical steppe in Inner Mongolia. Overall, ceasing disturbance increased ANPP of whole community but increasing disturbance had no significant effect on community ANPP, which was driven by ANPP of dominant species; and species richness and asynchrony were independent of changing disturbance. Despite having no effect on species richness, both intensification and cessation of disturbance destabilized plant community productivity, primarily through effects on the stability of the dominant species. This highlights the importance of dominant species in driving community dynamics. Maintaining disturbance intensity is an appropriate strategy to maintain hay production and community stability in typical steppe in Inner Mongolia, and may be beneficial to the development of sustainable utilization of grassland and may ensure the income of resident population.

The impending rise in drought events in grasslands of northern China over the next few decades, coupled with escalating nitrogen (N) deposition, will have an important impact on nutrient resorption. Previous research has mostly focused on examining the individual effect of specific drought scenario or N enrichment on nutrient resorption. Nonetheless, the impacts of different drought regimes on the resorption of nutrients have rarely been distinguished, especially under the scenario of N enrichment in temperate typical steppe in Inner Mongolia, we studied how intense drought (excluding 100 % rainfall in June), chronic drought (excluding 50 % rainfall during June-August), reduced rainfall frequency (reducing half rainfall events without changing rainfall amount in June-August), and N deposition (0 and 10 g N m−2 yr−1) affected the efficiency of plants in reabsorbing N and phosphorus (P). Both intense and chronic drought significantly reduced N (by 9.41 % and 9.53 %, respectively) and P resorption efficiency (by 6.71 % and 6.62 %, respectively) in plant communities (defined as the proportion of N and P nutrient resorption from senescing leaves), however reducing rainfall frequency had less effects on plant community N and P resorption efficiency. Nitrogen deposition had no effects on N and P resorption efficiency. Drought and N addition interacted to affect plant community P resorption efficiency. Structural equation modeling (SEM) showed that drought reduced N and P resorption efficiencies in plant communities by directly decreasing soil moisture, suppressing nutrient concentrations in green leaves, and enhancing soil nutrient content. Nitrogen deposition reduced P resorption efficiency by reducing P concentration in green leaves, but this effect was offset by the reduction of soil P availability. These results imply that rainfall amount is more important than rainfall frequency in determining the nutrient resorption efficiency of plant communities in the typical steppe. This study highlights the importance of soil water and N availabilities as well as nutrient concentrations in green leaves in modulating the responses of plant nutrient resorption to global change in the typical steppe. • Intense and chronic drought reduced N and P resorption efficiency. • Reduced rainfall frequency did not change N and P resorption efficiency. • Drought and N addition interacted to affect P resorption efficiency. • Nitrogen deposition did not affect nutrient resorption efficiency. [ABSTRACT FROM AUTHOR]

Drought has been approved to affect the process of terrestrial ecosystems from different organizational levels, including individual, community, and ecosystem levels; however, which traits play the dominant role in the resistance of plant to drought is still unclear. The experiment was conducted in semi-arid temperate grassland and included six paired control and drought experimental plots. The drought treatment was completely removed from precipitation treatments from 20 June to 30 August 2013. At the end of the growing season in 2013, we removed the rain cover for ecosystem recovery in 2014. The results demonstrated that drought treatment increased the coverage of and abundance Heteropappus altaicus, Potentilla bifurca, and Artemisia scoparia by 126.2–170.0% and 63.4–98.9%, but decreased that of Artemisia frigida, Dontostemon dentatus, and Melissilus ruthenicu by 46.2–60.2% and 49.6–60.1%. No differences in coverage and abundance of Agropyron cristatum, Stipa kiylovii, and Cleistogenes squarrosa were found between control and drought treatment. The coverage and abundance of Stipa kiylovii have exceeded the original level before the drought stress, but Heteropappus altaicus still had not recovered in the first year after the disturbance. Our findings indicate that plant functional traits are important for the understanding of the resistance and resilience of plants to drought stress, which can provide data support for grassland management. [ABSTRACT FROM AUTHOR]

The typical steppe in Inner Mongolia is an important component of the Eurasian steppes. It plays a dominant role in preventing desertification and against sandstorms, but highly sensitive and vulnerable to climate change. Based on long-term observed precipitation data and remotely sensed Normalized Difference Vegetation Index (NDVI) images, the non-stationary behavior of summer precipitation and its linkage with vegetation change were investigated, by means of incorporating time-varying and physical based explanatory covariates in non-stationary modeling. Results indicated that time-dependent models exhibited good performance to reproduce the temporal variations of eco-hydrological variables. The non-stationarity of summer precipitation was prominently visible for the majority of sites during the period from 1957 to 2017, with the mean behavior described as a linear or nonlinear time-varying pattern. In general, the steppe has experienced a decreasing trend in summer precipitation, but whether the decline tends to maintain or weaken or strengthen depends on the spatial location of the site studied. Differences appeared in the changes of vegetation in summer from 1998 to 2017 in different sub-regions. Evidences for the presence of stationary evolution was found in most sub-regions in the middle part, together with a linear increase in the westernmost sub-regions while a non-linear decrease in the easternmost sub-regions. Covariate analyses further highlighted the role of precipitation variabilities in the modeling of the NDVI-related vegetation dynamics over the steppe. The potential relations of summer precipitation to vegetation growth were characterized as both linear and non-linear positive forms. In particular, precipitation extremes could be responsible for the occurrences of exceptional cases in vegetation condition. The fluctuations in summer precipitation have crucial significance for future predictions of vegetation succession. Findings from this study would lead to additional insights to understanding the effect of climate change on grassland ecosystem processes. [ABSTRACT FROM AUTHOR]

Abstract Phytolith‐occluded carbon (PhytOC) is an important long‐term stable carbon fraction in grassland ecosystems and plays a promising role in global carbon sequestration. Determination of the PhytOC traits of different plants in major grassland types is crucial for precisely assessing their phytolith carbon sequestration potential. Precipitation is the predominant factor in controlling net primary productivity (NPP) and species composition of the semiarid steppe grasslands. We selected three representative steppe communities of the desert steppe, the dry typical steppe, and the wet typical steppe in Northern Grasslands of China along a precipitation gradient, to investigate their species composition, biomass production, and PhytOC content for quantifying its long‐term carbon sequestration potential. Our results showed that (a) the phytolith and PhytOC contents in plants differed significantly among species, with dominant grass and sedge species having relatively high contents, and the contents are significantly higher in the below‐ than the aboveground parts. (b) The phytolith contents of plant communities were 16.68, 17.94, and 15.85 g/kg in the above‐ and 86.44, 58.73, and 76.94 g/kg in the belowground biomass of the desert steppe, the dry typical steppe, and the wet typical steppe, respectively; and the PhytOC contents were 0.68, 0.48, and 0.59 g/kg in the above‐ and 1.11, 0.72, and 1.02 g/kg in the belowground biomass of the three steppe types. (c) Climatic factors affected phytolith and PhytOC production fluxes of steppe communities mainly through altering plant production, whereas their effects on phytolith and PhytOC contents were relatively small. Our study provides more evidence on the importance of incorporating belowground PhytOC production for estimating phytolith carbon sequestration potential and suggests it crucial to quantify belowground PhytOC production taking into account of plant perenniality and PhytOC deposition over multiple years.

Purpose: Soil fungi have been proven to influence the plant productivity and community composition of grasslands, but regulation of soil fungi on the responses of plant production-community composition relationship to grazing and mowing remains unclear. Methods: Here, we assessed the functional characteristics of three fungal groups using the Ribosomal Database Project (RDP) classifier and data available in FUNGuild, and we characterized the community of saprotrophic, mycorrhizal, and potential plant pathogenic fungi from surface (0–10 cm) and subsurface soils (10–20 cm) of temperate grasslands, which experienced three management practices, grazing, mowing, and grazing + mowing, respectively. Results: We found that all three disturbances decreased plant aboveground production and changed plant community composition in grasslands. Compared with the control, grazing significantly reduced the richness of both saprophytic fungi and potential plant pathogens from surface soil, where the richness of saprophytic fungi under grazing + mowing was also significantly reduced. No changes in the richness of mycorrhizal fungi among three disturbances were observed compared to the control in the surface soil, where antagonistic interaction between potential plant pathogens and saprotrophic fungi drove the plant production-community composition relationship. On the contrary, three disturbances did not change the richness of all fungal functional guilds in the subsurface soil, where the plant production-community composition relationship was driven by antagonistic interaction between mycorrhizal fungi and potential plant pathogens. Conclusion: The findings reveal that antagonistic interaction between fungal guilds played important roles in regulating response of plant production-community composition to grazing and mowing in grasslands. Our finding highlights that potential plant pathogens also have a crucial effect on plant production-community composition relationship. This knowledge is important for predicting the shifts in ecosystem functions as consequence of changes in soil fungal groups during grassland management. [ABSTRACT FROM AUTHOR]

The frequency of extreme climate events has increased resulting in major changes to vegetation in arid and semi-arid areas. We selected 12 extreme climate indices and used trend analysis and multiple linear regression models to analyze extreme climate trends in steppe areas of Inner Mongolia and their impact on the normalized difference vegetation index (NDVI). From 1998 to 2017, the NDVI of the Inner Mongolia steppe increased overall; however, there was a small area of decrease. Extreme climate indices related to warming exhibited increasing trends, particularly in the desert steppe. Although the extreme precipitation index did not change significantly overall, it increased in the northeastern and southwestern regions of the study area and decreased in the central region. The established model showed that the extreme climate explained the highest NDVI variation in desert steppe (R2 = 0.413), followed by typical steppe (R2 = 0.229), and meadow steppe (R2 = 0.109). In desert steppe, TX90P (warm days index) had the greatest impact; in typical steppe, R10 (number of heavy precipitation days index) had the greatest impact; in meadow steppe, R95P (very wet days index) had the greatest impact. This study offered new insights into dynamic vegetation changes in steppe areas of Inner Mongolia and provided a scientific basis for implementing environmental protection strategies. [ABSTRACT FROM AUTHOR]

In the context of global change, the effects of livestock grazing and nitrogen (N) deposition on ecosystem structure and function of grasslands are not isolated, but simultaneous or even interactive. However, most studies on variations in plant functional traits and linkages to ecosystem function have focused on grazing or N enrichment alone. Few studies have combined these two factors to explore the role of intraspecific trait variability in community assembly and primary productivity, and their pathways on ANPP remain unclear.Here, we examined the effects of N addition and grazing on intra‐ and interspecific variations in plant functional traits in Inner Mongolia steppe based on two manipulative experiments with six N addition rates or grazing intensities over 6 years. The direct and indirect effects of N addition and grazing on ANPP were further analysed.Our results showed that N enrichment greatly enhanced intraspecific trait variability compared to grazing, which played an important role in maintaining species diversity and primary productivity. There was a negative linear relationship between species richness and intraspecific trait variance within community (TIP/IC), indicating that N enrichment promoted intraspecific trait variability and increased interspecific niche width, leading to a decrease in species richness. ANPP was positively correlated with TIP/IC values under N addition or grazing, suggesting that higher intraspecific trait variability was beneficial to maintaining grassland productivity. We also found that N addition had a direct positive effect on ANPP, and intraspecific trait variation was the secondary cause of ANPP variation; in contrast, grazing had an indirect negative effect on ANPP, mainly through species richness and interspecific trait variation.Synthesis and applications. Our findings have important implications for the restoration and management of semi‐arid grasslands. Considering the offsetting effects of N addition and grazing on primary productivity, fertilization measures can be integrated into pasture management to quickly restore productivity. In the restoration of degraded grassland by artificial reseeding, the optimal seedling density related to intraspecific variation should be determined, and the forge species should be selected according to plant functional traits, taking into account the strategies of both conservative resource‐use and grazing tolerance. [ABSTRACT FROM AUTHOR]

Alpine meadow, typical steppe and desert are globally important rangeland ecosystems. However, the seasonal variations in concentrations of trace elements, which are important nutrients for grazing livestock, are unclear in these types of rangeland and it is difficult to prevent disorders in grazing livestock caused by trace element excesses and deficiencies. In order to identify which forage species might serve as indicators of the trace element status of livestock forage, we investigated the seasonal trends in Fe, Mn, Cu, and Zn concentrations in the plant communities and dominant species from diverse rangeland types in northwest China in relation to livestock sufficiency levels. The trace element concentrations in the plant communities changed significantly with the season, with the highest Cu, Mn and Zn concentrations and the lowest Fe and Mn concentrations detected in spring and summer, respectively. The seasonal mean temperature, seasonal precipitation, and above-ground biomass significantly negatively correlated with the seasonal variation of Fe and Mn concentrations in the plant community. However, there was almost no significant correlation between these factors and the seasonal Cu and Zn concentrations. The plant concentrations of Fe and Mn were much higher than the recommended levels for livestock in all rangeland types, but the concentrations of Cu in the alpine meadow and the Zn concentrations in all the rangelands barely met the nutritional requirements for animal growth. Based on these deficiencies, we suggest that some forage species could be used as biological indicators to predict changes in the concentrations of trace elements. A decrease in the relative biomass of Kobresia capillifolia and Kobresia humilis in alpine meadows implies a decrease in the levels of Cu in the plant community. A decrease in the relative biomass of K. humilis in alpine meadows, an increase in Stipa bungeana in typical steppes and an increase in Nitraria tangutorum and Salsola passertine in desert rangelands lead to decreased concentrations of Zn in the plant community.

Accurate knowledge of the relationship between modern vegetation and the corresponding surface pollen assemblages is the key to the quantitative reconstruction of paleovegetation and paleoclimate. The pollen assemblages of steppe regions are affected by many factors and distinguishing the pollen assemblages of different plant community types, especially Artemisia and Poaceae communities is a major difficulty in modern pollen studies in these regions. In this study we used RDA analysis to analyze modern vegetation and pollen percentage data from 119 sampling sites in different plant communities in the Bashang region of North China, which has a typical steppe vegetation. We used the results to quantitatively determine the distinguishing features of various plant community types and the relationship between the percentages of the dominant pollen types and the corresponding vegetation cover. The major results are as follows: 1) there is a clear distinction between Artemisia and Poaceae communities; in the Artemisia community, Artemisia pollen percentages are typically > 50%, and Poaceae pollen percentages are typically 3%, and Artemisia pollen percentages are typically 10%.

Nematode communities are meaningful biological indicators of soil health and soil processes across different grassland types and management practices and analyses of nematode communities provide insight into structure, function, and sensitivity or resilience across multiple ecosystems. In three model grasslands: meadow steppe (MS), typical steppe (TS), and alpine meadow (AM), this current research examined responses of soil nematode communities and related edaphic characteristics to grazing, mowing, and crop cultivation at two soil depths. The research fills a critical knowledge gap by resolving multidirectional influences between local conditions, grassland management practices, and nematode communities. Across grassland types, nematode abundance in AM was greater than MS and TS grasslands, and nematodes were more abundant near the soil surface. Cultivation resulted in greater nematode abundance compared to all other management practices, and generally, bacterivores were the most dominant nematode trophic group. The TS and MS grasslands had relatively more bacterivores, exhibiting substantial influences on soil mineralization and organic matter decomposition pathways. The AM grassland showed relatively more plant feeding nematodes, driving soil mineralization pathways. Among the three management practices, crop cultivation had the greatest impact on nematode community structure and the soil environment, especially in relatively sensitive AM grasslands. In fact, AM soil environments responded most dramatically to cultivation, with nematode abundance, soil quality, and food web complexity increasing. However, soil ecosystem stability, food web reliance, and food web response to resources decreased in cultivated AM soils. Results indicate that unique environmental characteristics in the Qinghai-Tibet plateau drive substantially different AM grassland nematode community structure and soil conditions compared to TS or MS grasslands. As anthropogenic pressures on these ecosystems mount, it is critical to understand how different management practices influence grassland nematode communities, with cascading effects through soil environments.

Grassland ecosystem services (GES) are closely related to human well-being, and an accurate understanding of the driving mechanisms and relative contributions of climate change and human activities on GES is beneficial for grassland sustainable management. Current studies have focused on analyzing the impacts of climate factors on GES, but few studies have included grazing pressure to comprehensively assess the complex impacts of climate change and human activities. This study systematically analyzed the spatiotemporal patterns of climate factors, grazing pressure, and ecosystem services in Xilingol typical steppe from 2000–2019, and thoroughly explored the driving mechanisms and relative contributions of climate change and grazing pressure on GES over the past 20 years. The study points out that although the overall ecosystem services in the study area have improved over the past 20 years, driven by climate change and favorable human activities, grazing pressure management should be further strengthened to improve the resilience of ecosystem services to unfavorable climate conditions due to the high uncertainty of future climate conditions. The research results can help to improve the understanding of the complex relationship between climate change, land use and GES, and provide recommendations for future grassland use planning.

Background 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. Methods We used three precipitation treatments to understand the effect of precipitation on soil respiration of a typical arid steppe in the Loess Plateau in north-western China. Precipitation was captured and relocated to simulate precipitation rates of 50%, 100%, and 150% of ambient precipitation. Results and Discussion Soil moisture was influenced by all precipitation treatments. Shoot biomass was greater, though non-significantly, as precipitation increased. However, both increase and decrease of precipitation significantly reduced root biomass. There was a positive linear relationship between soil moisture and soil respiration in the study area during the summer (July and August), when most precipitation fell. Soil moisture, soil root biomass, pH, and fungal diversity were predictors of soil respiration based on partial least squares regression, and soil moisture was the best of these. Conclusion Our study highlights the importance of increased precipitation on soil respiration in drylands. Precipitation changes can cause significant alterations in soil properties, microbial fungi, and root biomass, and any surplus or transpired moisture is fed back into the climate, thereby affecting the rate of soil respiration in the future.

Drought has been approved to affect the process of terrestrial ecosystems from different organizational levels, including individual, community, and ecosystem levels; however, which traits play the dominant role in the resistance of plant to drought is still unclear. The experiment was conducted in semi-arid temperate grassland and included six paired control and drought experimental plots. The drought treatment was completely removed from precipitation treatments from 20 June to 30 August 2013. At the end of the growing season in 2013, we removed the rain cover for ecosystem recovery in 2014. The results demonstrated that drought treatment increased the coverage of and abundance Heteropappus altaicus, Potentilla bifurca, and Artemisia scoparia by 126.2–170.0% and 63.4–98.9%, but decreased that of Artemisia frigida, Dontostemon dentatus, and Melissilus ruthenicu by 46.2–60.2% and 49.6–60.1%. No differences in coverage and abundance of Agropyron cristatum, Stipa kiylovii, and Cleistogenes squarrosa were found between control and drought treatment. The coverage and abundance of Stipa kiylovii have exceeded the original level before the drought stress, but Heteropappus altaicus still had not recovered in the first year after the disturbance. Our findings indicate that plant functional traits are important for the understanding of the resistance and resilience of plants to drought stress, which can provide data support for grassland management.

Phytolith‐occluded carbon (PhytOC) is an important long‐term stable carbon fraction in grassland ecosystems and plays a promising role in global carbon sequestration. Determination of the PhytOC traits of different plants in major grassland types is crucial for precisely assessing their phytolith carbon sequestration potential. Precipitation is the predominant factor in controlling net primary productivity (NPP) and species composition of the semiarid steppe grasslands. We selected three representative steppe communities of the desert steppe, the dry typical steppe, and the wet typical steppe in Northern Grasslands of China along a precipitation gradient, to investigate their species composition, biomass production, and PhytOC content for quantifying its long‐term carbon sequestration potential. Our results showed that (a) the phytolith and PhytOC contents in plants differed significantly among species, with dominant grass and sedge species having relatively high contents, and the contents are significantly higher in the below‐ than the aboveground parts. (b) The phytolith contents of plant communities were 16.68, 17.94, and 15.85 g/kg in the above‐ and 86.44, 58.73, and 76.94 g/kg in the belowground biomass of the desert steppe, the dry typical steppe, and the wet typical steppe, respectively; and the PhytOC contents were 0.68, 0.48, and 0.59 g/kg in the above‐ and 1.11, 0.72, and 1.02 g/kg in the belowground biomass of the three steppe types. (c) Climatic factors affected phytolith and PhytOC production fluxes of steppe communities mainly through altering plant production, whereas their effects on phytolith and PhytOC contents were relatively small. Our study provides more evidence on the importance of incorporating belowground PhytOC production for estimating phytolith carbon sequestration potential and suggests it crucial to quantify belowground PhytOC production taking into account of plant perenniality and PhytOC deposition over multiple years. [ABSTRACT FROM AUTHOR]

It is not certain that long-term grazing exclusion influences arbuscular mycorrhizal (AM) fungi and their association with steppe vegetation. In this study, soil and plant samples were collected from two sites of grazing exclusion since 1983 (E83) and 1996 (E96), and one site of free-grazing (FG) in the typical steppe of Xilinguole League, Inner Mongolia, China, and assayed for soil basic physicochemical properties, AM fungal parameters, aboveground biomass and shoot phosphorus (P) uptake as well. The results showed that long-term grazing exclusion of E83 and E96 led to less drastic seasonal changes and significant increases in spore density, hyphal length density and root colonization intensity of AM fungi and even soil alkaline phosphatase activity, by up to 300, 168, 110 and 102%, respectively, compared with those of FG site. In addition, the total aboveground biomass and shoot P uptake of E83 and E96 were 75–992% and 58–645%, respectively, higher than those of FG. Generally, the root colonization intensity, spore density, and hyphal length density of AM fungi were all positively correlated with the aboveground biomass and even shoot P uptake of plant. These results may imply that grazing exclusion play a critical role in increasing the growth of AM fungi, and subsequently, may increase plant P uptake and aboveground biomass production. Moreover, the spore density could sensitively reflect the impacts of long-term grazing exclusion on AM fungi since survival strategy of spores in soil.

The underlying mechanism of grazing exclusion on grassland community structure and dynamics may be determined by offspring recruitment. However, little is known about the role of plant functional groups in community recruitment. A chronosequence of grazing‐excluded grasslands was selected to analyze the aboveground community composition and offspring recruitment based on plant functional groups. Grazing exclusion significantly increased grasses biomass (111.7–480.7%), height (95.6–241.8%), and coverage (84.8–148.5%) and decreased grasses density (10.2–59.7%). Grazing exclusion eroded total species richness (13.2–25.0%) and forbs richness (16.6–39.4%). Grazing exclusion shifted the dominance from forbs to grasses. Grasses functional group (GFG) determined community structure, but forbs functional group (FFG) regulated species diversity in typical steppe. Clonal recruitment played a decisive role in the community regeneration, especially tiller recruit mode by GFG. Grazing exclusion had different effects on offspring recruitment of grasses and FFG. Total asexual, grasses asexual, and tiller offspring density both first significantly increased and then significantly decreased with grazing exclusion time. Forbs asexual offspring density did not significantly decrease in 10‐ and 20‐year grazing exclusion grasslands but significantly reduced after 30 years. Change in community dominance caused by grazing or grazing exclusion did not alter the tiller recruitment dominance in this area. Our results indicate that grazing exclusion presents a negative effect on community regeneration and biodiversity conservation in the studied typical steppe. [ABSTRACT FROM AUTHOR]

Objective In order to improve fermentation quality of natural grasses, their silage preparation and fermentation quality in meadow steppe (MS) and typical steppe (TS) were studied. Methods The small-scale silages and round bale silages of mixed natural grasses in both steppes were prepared using the commercial lactic acid bacteria (LAB) inoculants Chikuso-1 (CH, Lactobacillus plantarum) and cellulase enzyme (AC, Acremonium cellulase) as additives. Results MS and TS contained 33 and 9 species of natural grasses, respectively. Stipa baicalensis in MS and Stipa grandi in TS were the dominant grasses with the highest dry matter (DM) yield. The crude protein (CP), neutral detergent fiber and water-soluble carbohydrate of the mixed natural grasses in both steppes were 8.02% to 9.03%, 66.75% to 69.47%, and 2.02% to 2.20% on a DM basis, respectively. All silages treated with LAB and cellulase were well preserved with lower pH, butyric acid and ammonia-N content, and higher lactic acid and CP content than those of control in four kinds of silages. Compared with CH- or AC-treated silages, the CH+ AC-treated silages had higher lactic acid content. Conclusion The results confirmed that combination with LAB and cellulase may result in beneficial effects by improving the natural grass silage fermentation in both grasslands.

Arbuscular mycorrhizal (AM) fungal diversity was measured in three different natural mid-temperate steppe types: the meadow steppe, typical steppe, and desert steppe. In these steppe soils, 24 AM fungal species from eight genera were identified, in which Glomus had the highest relative abundance. Funneliformis geosporus, Glomus microaggregatum, and Septoglomus constrictum had high relative abundance and were found widely across varying soil depth and steppe type. Meadow steppes had significantly higher AM fungal species richness compared to typical steppes and desert steppes, but there was no significant difference between typical steppes and desert steppes. AM fungal spore density, two Bradford-reactive soil protein (BRSP) fractions, and extraradical hyphal length densities (HLDs) were significantly different among the three steppe types. Alkaline phosphatase and acid phosphatase activity, urease activity, and soil bacterial and actinomycotic quantity were significantly related to the AM fungal spore density and species richness in these arid and semi-arid steppes. Therefore, steppe types could influence the distribution pattern of AM fungal diversity and the content of glomalin-related soil protein (GRSP). [ABSTRACT FROM AUTHOR]

Abstract The process of blowing snow is important for secondary distribution of water resources in seasonal grassland snow areas because it affects the regeneration, growth, and nutrient circulation of vegetation. This study conducted field observations of blowing snow and snow accumulation in a grassland area typical of northern China. The results showed that in the near-surface area (0 to 100 cm), snow drifting intensity increased exponentially with a mean wind speed of 2 m/s, and that the maximum snow drifting intensity, which was found within 30 cm of the surface, accounted for 89.61% of the total amount of snow drifting within the near-surface area. The snow drifting intensity was strong under conditions of an abundant snow source and sparse vegetation, with an average value of 2.203 g/cm/min. The snow drifting intensity was lower under conditions of an insufficient snow source and higher vegetation coverage, with an average value of 0.545 g/cm/min. In typical grassland areas with a bare surface and sparse vegetation, snow cover is generally thin; the mean snow depth in such areas during the observation period of this study was 4.03 cm, and this constituted the source of the drifting snow. Snow cover was thicker in areas with taller grass and greater vegetation coverage; the mean value of snow depth in such areas during the observation period was 16.56 cm, and this constituted the main snow cover area. The observation results provide basic data to support the estimation of snow cover amount in grassland ecosystems, optimization of the utilization of snow water resources, regularization of snow cover, restoration of vegetation, and prevention and control of snowstorms. Highlights • The process of blowing snow and snow cover were observed. • The relationship between vegetation and snow cover were surveyed. • Snow areas with a bare surface and sparse vegetation are the primary source areas of blowing snow. • Greater vegetation coverage and height are areas of snow accumulation. [ABSTRACT FROM AUTHOR]

Understanding the effects of climate change, in particular, climate extremes on plant functional traits can provide a mechanistic basis for predicting how plant communities may be altered in the future. Here, we focused on a dominant species in Inner-Mongolia typical temperate steppe, Leymus chinensis (Trin.) Tzvei, to examine the responses of plant functional traits to experimentally imposed extreme drought at three sites along an aridity gradient. When comparing the driest (high aridity) to the wettest sites (low aridity), plant height, leaf dry matter content and δ13C (water use efficiency) were increased at the intermediate and low aridity sites, whereas specific leaf area and leaf nitrogen content were reduced at the high-aridity site. When extreme drought (~ 66% reduction in the growing season precipitation) was experimentally imposed at all sites, plant height decreased and δ13C of L. chinensis increased at the intermediate and low aridity sites. The extreme drought of 66% precipitation reduction also increased leaf dry matter content in high- and low-aridity sites. Compared to the control (ambient precipitation), extreme drought increased the strength of the positive association between plant height and δ13C, as well as the negative associations of specific leaf area with plant height and leaf dry matter content. Thus, extreme drought altered key functional traits of the dominant grass of Inner Mongolia steppe, particularly at the low-aridity site where the drought decreased plant size and increased water use efficiency and affected relationships between these traits. [ABSTRACT FROM AUTHOR]

Plant–plant interactions play a key role in the function and structure of communities. The combined effect of drought stress and grazing disturbance on shaping plant–plant interactions is still poorly understood, while this combination is common in semiarid ecosystems. Four species including Stipa grandis, which is dominant in the typical steppe, and Stipa krylovii, Artemisia frigida, and Cleistogenes squarrosa, which are dominant species in the S. grandis degraded communities, were selected as study targets. We conducted a competition experiment (uniformly dense monoculture or mixture, respectively) under controlled conditions, including both drought stress and mowing disturbance, and calculated the relative interaction index (RII) of tiller number and RII of biomass for each species under each condition. (a) Under the same condition, the RII of tiller number and that of biomass for the same species usually showed reverse trends. (b) Mowing disturbance rather than drought stress played a negative role in influencing S. grandis' or S. krylovii's RII of tiller number and played a positive role in influencing A. frigida's RII of biomass. (c) Drought stress rather than mowing disturbance played a positive role in influencing C. squarrosa's RII of tiller number. (d) Neighbor species significantly influenced S. grandis' RII of tiller number, S. krylovii's RII of tiller number, A. frigida's RII of tiller number and biomass, and C. squarrosa's RII of biomass. These results could provide an explanation for why S. krylovii, A. frigida, and C. squarrosa can replace S. grandis and become the dominant species when S. grandis communities undergo a process of degradation due to overgrazing or climatic drought in natural communities. The present study provided powerful evidences for species replacement in the typical steppe of Inner Mongolia and elucidated the driving mechanisms of S. grandis communities' retrogressive succession. The combined effect of drought stress and grazing disturbance on shaping plant–plant interactions is the key process of retrogressive succession in Inner Mongolia steppe, China. We conducted a competition experiment to explore how Stipa grandis is replaced by the other three species during the retrogressive succession. (a) Neighbor species could help Stipa krylovii to increase its tiller number but inhibit S. grandis's tiller number under mowing treatment. (b) Mowing disturbance played a positive role in Artemisia frigida expanding in medium–heavy‐degraded region. (c) The higher tolerance to drought stress and lower competitive capacity enabled Cleistogenes squarrosa to be dominant species in heavy‐degraded region but not in stable or light‐degraded region. The present study provided evidences for species replacement in retrogressive succession of S. grandis communities. [ABSTRACT FROM AUTHOR]

Abstract: Overgrazing substantially contributes to global grassland degradation by decreasing plant community productivity and diversity through trampling, defoliation, and removal of nutrients. Arbuscular mycorrhizal (AM) fungi also play a critical role in plant community diversity, composition, and primary productivity, maintaining ecosystem functions. However, interactions between grazing disturbances, such as trampling and defoliation, and AM fungi in grassland communities are not well known. We examined influences of trampling, defoliation, and AM fungi on semiarid grassland plant community composition for 3 yr, by comparing all combinations of these factors. Benomyl fungicide was applied to reduce AM fungal abundance. Overgrazing typically resulted in reduced dominance of Stipa Krylovii, contributing to degradation of typical steppe grasslands. Our results indicated trampling generally had little effect on plant community composition, unless combined with defoliation or AM fungal suppression. Defoliation was the main component of grazing that promoted dominance of Potentilla acaulis over Stipa krylovii and Artemisia frigida, presumably by alleviating light limitation. In non‐defoliated plots, AM fungi promoted A. frigida, with a concomitant reduction in S. krylovii growth compared to corresponding AM suppressed plots. Our results indicate AM fungi and defoliation jointly suppress S. krylovii biomass; however, prolonged defoliation weakens mycorrhizal influence on plant community composition. These findings give new insight into dominant plant species shifts in degraded semiarid grasslands. [ABSTRACT FROM AUTHOR]

Abstract: Silicon (Si) not only plays an important role in plant growth but also contributes significantly to the long‐term terrestrial carbon sink in the form of phytoliths. This study investigated Si content of 184 plant species in meadow steppe and typical steppe of northern China to examine the influential factors of Si distribution and evaluate the potential phytolith carbon sequestration of these grasslands. Our results indicated that the average Si content generally decreased in the following order of Equisetopsida > Monocotyledoneae > Dicotyledoneae. Within angiosperms, although most Si accumulator plants were commelinid monocots, many eudicots also accumulated abundant Si in their above‐ground tissues. The Si content of plant above‐ground parts in typical steppe (6.53 ± 2.88 g/kg) was significantly higher than that in meadow steppe (2.15 ± 0.92 g/kg). The estimated phytolith‐occluded carbon (PhytOC) production flux in typical steppe (0.81 ± 0.36 kg CO2 ha−1 year−1) was higher than that in meadow steppe (0.54 ± 0.23 kg CO2 ha−1 year−1). This study demonstrates that plant phylogeny influences the Si content of individual species, whereas grassland type with different mean annual precipitation and mean annual temperature may significantly affect the abundance of high Si species. We conclude that increasing the abundance of grass species with high Si content in meadow steppe and appropriate grazing and fertilizer application in typical steppe will enhance the phytolith carbon sequestration in grasslands of northern China. [ABSTRACT FROM AUTHOR]

The East Eurasian Steppe Transect (EEST) is the first international transect across regions of middle and high latitudes in the eastern Eurasian steppe. The EEST is an ideal platform for researching the response of Eurasian temperate steppe to global change, because of its integrated gradients of temperature and human activities on a large-scale. In this study, basic characteristics of plant communities along the EEST across a latitudinal gradient was analyzed. According to the survey of 58 sampling sites, there are 140 species belonging to 34 families and 94 genera. Of particular note was the finding of Astragalus dalaiensis which has disappeared in the grasslands of China. On the whole, Gramineae plants are dominant with Liliaceae plants in the communities significantly decreasing along the latitudinal gradient from south to north. The Shannon-Wiener index and biomass of communities all decreased along the latitudinal gradient with significant negative linear regressions. The SDR2 (summed dominance ratio based on two factors) of dominant plants in the upper layers of communities, such as Stipa and Leymus chinensis, decreased along the latitudinal gradient from south to north. Especially, the SDR2 of L. chinensis decreased significantly. The SDR2 of Cleistogenes squarrosa, Agropyron cristatum in the lower layers of communities and the indicator species for degradation were not affected. Potentilla acaulis was found mainly in the southern and northern areas. Stellera chamaejasme was found just in a few sites in the southern area of the EEST. In communities of Stipa grandis and Stipa krylovii, annual and biennial species are dominant. The ratio of annual and biennial species in the community is significantly related to the latitudinal gradient. Perennial herbaceous plants and shrubs were not affected. According to the principal component analysis (PCA), with the data from 58×140 dimensions, the first and second components had the lowest proportion, thus indicating that the species compositions and community structures are homogeneous along the EEST. There is a certain degree of spatial differentiation along the EEST due to degradation's differences resulting from the different land uses.

The response of soil methane (CH 4 ) uptake to increased nitrogen (N) deposition and grazing management was studied in three types of steppe (i.e., meadow steppe, typical steppe, and desert steppe) in Inner Mongolia, China. The experiment was designed with four simulated N deposition rates such as 0, 50, 100, and 200 kg N ha − 1 , respectively, under grazed and fenced management treatments. Results showed that the investigated steppes were significant sinks for CH 4 , with an uptake flux of 1.12–3.36 kg ha − 1 over the grass growing season and that the magnitude of CH 4 uptake significantly ( P < 0.05) decreased with increasing N deposition rates. The soil CH 4 uptake rates were highest in the desert steppe, moderate in the typical steppe, and lowest in the meadow steppe. Compared with grazed plots, fencing increased the CH 4 uptake by 4.7–40.2% with a mean value of 20.2% across the three different steppe types. The responses of soil CH 4 uptake to N deposition in the continental steppe varied depending on the N deposition rate, steppe type, and grazing management. A significantly positive correlation between CH 4 uptake and soil temperature was found in this study, whereas no significant relationship between soil moisture and CH 4 uptake occurred. Our results may contribute to the improvement of model parameterization for simulating biosphere-atmosphere CH 4 exchange processes and for evaluating the climate change feedback on CH 4 soil uptake. [ABSTRACT FROM AUTHOR]

Vegetation phenology in temperate grasslands is highly sensitive to climate change. However, it is still unclear how the timing of vegetation phenology events (especially for autumn phenology) is altered in response to climate change across different grassland types. In this study, we investigated variations of the growing season start (SOS) and end (EOS), derived from Moderate Resolution Imaging Spectroradiometer (MODIS) data (2000-2016), for meadow steppe, typical steppe, and desert steppe in the Inner Mongolian grassland of Northern China. Using gridded climate data (2000-2015), we further analyzed correlations between SOS/EOS and pre-season average air temperature and total precipitation (defined as 90-day period prior to SOS/EOS, i.e., pre-SOS/EOS) in each grid. The results showed that both SOS and EOS occurred later in desert steppe (day of year (doy) 114 and 312) than in meadow steppe (doy 109 and 305) and typical steppe (doy 111 and 307); namely, desert steppe has a relatively late growing season than meadow steppe and typical steppe. For all three grasslands, SOS was mainly controlled by pre-SOS precipitation with the sensitivity being largest in desert steppe. EOS was closely connected with pre-EOS air temperature in meadow steppe and typical steppe, but more closely related to pre-EOS precipitation in desert steppe. During 2000-2015, SOS in typical steppe and desert steppe has significantly advanced by 2.2 days and 10.6 days due to a significant increase of pre-SOS precipitation. In addition, EOS of desert steppe has also significantly advanced by 6.8 days, likely as a result from the combined effects of elevated preseason temperature and precipitation. Our study highlights the diverse responses in the timing of spring and autumn phenology to preceding temperature and precipitation in different grassland types. Results from this study can help to guide grazing systems and to develop policy frameworks for grasslands protection. [ABSTRACT FROM AUTHOR]

To understand the effects of different disturbance regimes on the bud bank demography in perennial grasslands, we conducted a demographic field investigation of the bud bank in a typical steppe on the Loess Plateau. Grazing significantly decreased and fire significantly increased bud bank density compared to fenced grasslands. For different bud bank types, grazing significantly decreased tiller bud bank density, and fire significantly increased the density of root crown buds and rhizomatous buds in relation to fenced grasslands. Tiller buds accounted for the majority of the total bud banks independently of the disturbance regimes. Our study suggests that the grasslands with a large reserve bud bank may be the most resistant to disturbance, and fencing is an effective grassland management measure to keep a large bud bank in typical steppe on the Loess Plateau. [ABSTRACT FROM AUTHOR]

Vegetation reconstructions from palaeoecological records depend on adequate understanding of relationships between modern pollen, vegetation and climate. A key parameter for quantitative vegetation reconstructions is the Relative Pollen Productivity (RPP). Differences in both environmental and methodological factors are known to alter the RPP estimated significantly, making it difficult to determine whether the underlying pollen productivity does actually vary, and if so, why. In this paper, we present the results of a replication study for the Bashang steppe region, a typical steppe area in northern China, carried out in 2013 and 2014. In each year, 30 surface samples were collected for pollen analysis, with accompanying vegetation survey using the “Crackles Bequest Project” methodology. Sampling designs differed slightly between the two years: in 2013, sites were located completely randomly, whilst in 2014 sampling locations were constrained to be within a few km of roads. There is a strong inter-annual variability in both the pollen and the vegetation spectra therefore in RPPs, and annual precipitation may be a key influence on these variations. The pollen assemblages in both years are dominated by herbaceous taxa such as Artemisia , Amaranthaceae, Poaceae, Asteraceae, Cyperaceae, Fabaceae and Allium . Artemisia and Amaranthaceae pollen are significantly over-represented for their vegetation abundance. Poaceae, Cyperaceae and Fabaceae seem to have under-represented pollen for vegetation with correspondingly lower RPPs. Asteraceae seems to be well-represented, with moderate RPPs and less annual variation. Estimated Relevant Source Area of Pollen (RSAP) ranges from 2000 to 3000 m. Different sampling designs have an effect both on RSAP and RPPs and random sample selection may be the best strategy for obtaining robust estimates. Our results have implications for further pollen-vegetation relationship and quantitative vegetation reconstruction research in typical steppe areas and in other open habitats with strong inter-annual variation. [ABSTRACT FROM AUTHOR]