Plants have evolved numerous belowground strategies to capture nutrients. While root functional differentiation between absorption and transportation has been inferred from order-based traits, the role of microbiomes in mediating this differentiation remains unclear. We measured traits (anatomical, chemical, and morphological) of lower order (absorption-dominated) and higher order (transportation-dominated) roots of 37 herbaceous species (13 monocots and 24 dicots) in a temperate grassland. Furthermore, we employed high-throughput quantitative polymerase chain reaction and 16S rRNA gene sequencing to investigate bacterial nitrogen-transformation gene abundance, diversity, and community assembly along the soil-root continuum (rhizosphere, rhizoplane, and endosphere) and analyzed their relationships with root traits. Monocot roots exhibited greater bacterial diversity and nitrogen-transformation gene abundances than dicots. Within dicots, lower order roots showed higher bacterial diversity and nitrogen-transformation gene abundances than higher order roots, a pattern not observed in monocots. Lower order roots, characterized by higher cortex proportion, facilitated the enrichment of diverse bacteria and recruitment of nitrogen-transformation microorganisms. These patterns were associated with a decrease in homogeneous selection from lower order to higher order roots. This study reveals the mechanisms of functional differences among herbaceous root orders from a microbiome perspective, offering further insights into how root-microbe interactions underpin nitrogen-transformation potential in terrestrial ecosystems.

Seasonal timing of extreme drought events drives functional trait shifts and plasticity in dominant Inner Mongolian steppe grasses

Enhanced deposition of nitrogen (N) has great impacts on grassland ecosystems. A decline in N deposition has occurred in many regions across the globe. Changes in N deposition alter the structure and functions of grassland ecosystems and bacterial community of soil and rhizosphere. However, the responses of plant microbiomes to N deposition and cessation of N input in terms of resistance and resilience have not been systematically evaluated. We examined the effects of N addition and cessation of N addition on leaf- and root-associated bacterial communities through a consecutive N addition and cessation of N addition experiment in a temperate grassland. We found that leaf-associated bacterial community exhibited lower resistance to N enrichment than root-associated bacterial community, which was mainly steered by leaf soluble sugars and leaf morphology via regulating functional taxa. In contrast, the root-associated bacterial community showed stronger resilience to cessation of N addition than leaf-associated bacterial community, which may be explained by the high N accumulation in roots and root morphology via regulating functional taxa. The greater resistance and resilience in the root-associated bacterial community may be attributed to the presence of host-related factors. Additionally, N enrichment-induced suppression of beneficial symbiotic microbes associated with the N cycle in the leaf-associated bacterial community was not readily recovered after cessation of N input. Conversely, microbes involved in carbon cycle and ecological restoration in the root-associated bacterial community showed a quick recovery after cessation of N enrichment. Our results offer valuable insights into the mechanisms by which changes in N input influence the plant microbial community.IMPORTANCEAs an integral component of ecosystems, the plant microbiome plays an important role in the response of grassland ecosystems to enhanced N deposition. Changes in N deposition influence bacterial communities of soil and rhizosphere of grassland ecosystems. However, whether and how the N deposition and cessation of N input impact microbiomes of plant species of temperate grasslands remain unexplored. Based on a long-term N-addition experiment in a temperate steppe, we discover that leaf- and root-associated bacterial communities respond differently to N addition and subsequent cessation of N addition. The leaf-associated bacterial community exhibits lower resistance to N enrichment than the root-associated bacterial community due to the unique environment of the phyllosphere, whereas the root-associated bacterial community shows stronger resilience to cessation of N addition than the leaf-associated bacterial community due mainly to the higher root N accumulation and morphology. These findings offer valuable insights into the impact and mechanism of N interference on the plant microbial community.

Taxonomically conservative root phenolic compounds underpin biogeochemical niche separation between grasses and forbs in temperate steppes of northern China.

Legacy of heavy grazing triggers faster natural recovery in degraded temperate steppe

Contrasting responses of carbon fluxes to hydrothermal drivers in dry grassland and wet meadow ecosystems of the temperate steppe

Grasslands, as dominant terrestrial ecosystems, significantly influence soil microbial communities through alterations in soil properties. However, their effects on spatial patterns of soil microbial communities are still under-investigated. To address this, we quantified taxa–area (TAR) and node–area (NAR) relationships for prokaryotic and fungal communities across temperate steppe (TS), alpine steppe (AS), and alpine meadow (AM). Our findings indicated that the spatial turnover of both prokaryotic and fungal communities were higher in alpine steppe and alpine meadow than in temperate steppe, mirroring the gradient of soil environmental heterogeneity. Notably, overall species richness increased logarithmically with sampling area in all grasslands; in striking contrast, co-occurring richness exhibited an increasing and then decreasing trend in AS and AM, but declined monotonically in TS, indicating that microbial interaction networks collapse once a critical spatial threshold is exceeded regulated by ecosystem type and environmental heterogeneity. In growing season, the stochastic dominance in prokaryotic assembly (Normalized stochasticity ratio = 0.71–0.89) and deterministic dominance in fungal assembly (Normalized stochasticity ratio = 0.23–0.37) can be explained by their differences in niche breadth and migration rate. These scale-dependent biogeographic patterns demonstrate that grassland type impacts distinct interactions and spatial patterns of microbial communities. These findings provide novel insights into a comprehensive understanding of how grassland type mediates soil microbial community.

Examining the long-term spatiotemporal distribution of grassland types and their transitions is crucial for better understanding regional and global changes. Most research in this field has examined the spatial distribution, temporal dynamics of grasslands, and their causes as a unified entity. This study predicted the distribution of nine major grassland types in Xinjiang under three climate change scenarios from 2041 to 2100 based on 1980s grassland maps, field data in 2023, and 28 factors. The total area of the nine grassland types showed a decreasing trend from 2041 to 2100. The lowland meadow (LM), temperate meadow steppe (TMS), temperate steppe desert (TSD), temperate desert steppe (TDS), and mountain meadow (MM) expanded, while significant declines occurred in alpine meadow (AM), alpine steppe (AS), temperate desert (TD), and temperate steppe (TS). Among cumulative contribution rate of the 28 factors examined in this study, NDVI, vegetation type, slope, elevation, soil_symbol, soil_ph, Bio1, Bio5, Bio8, Bio9, Bio10, Bio12, Bio13, Bio15, and Bio18 played important roles in most grassland types. LM, TD, and AS grassland were found to be more sensitive to E (environment), while AM, TDS, and TSD were more influenced by T (temperature). The distributions of MM and TMS are significantly influenced by the combined effects of all three categories of factors. For TS, the impacts of both temperature and environmental factors are substantial. These findings provided a robust foundation for conservation planning and the sustainable management of grassland ecosystems in temperate and alpine regions.

Long-term and short-term effects of nitrogen addition on soil acidification in a temperate steppe

Negative impacts of herbivore grazing pressure on soil and water conservation services in montane grasslands exacerbated by atmospheric aridity.

Abstract Background Soil microclimate plays critical roles in influencing terrestrial ecosystem functioning. However, how the impacts of climatic change on microclimate vary with vegetation types remains elusive. Methods Using a 9-year (2014–2022) dataset from a field manipulative experiment conducted on the Mongolian Plateau, this study examined the effects of nighttime warming and changing precipitation on soil microclimate of three temperate steppes (i.e., desert, typical, and meadow steppes) along a precipitation gradient. Results Over the 9 years, nighttime warming increased soil temperature by 0.88, 0.78, and 0.65 °C, decreased precipitation elevated it by 0.63, 0.34, and 0.24 °C, but increased precipitation lowered it by 0.46, 0.84, and 0.90 °C in the desert, typical, and meadow steppes, respectively. Nighttime warming suppressed soil moisture by 0.64% (v/v) in the meadow steppe only. Decreased precipitation reduced soil moisture by 0.84, 0.88, and 1.30%, whereas increased precipitation enhanced it by 0.92, 1.23, and 1.24% in the desert, typical, and meadow steppes, respectively. The response of soil microclimate to the simulated climate change was primarily driven by evaporation, transpiration, and plant cover in the desert and typical steppes, whereas transpiration and plant cover explained those changes in the meadow steppe. Conclusions These findings of the variations of underlying mechanisms of soil microclimate response to climate change with water conditions can improve predictions of ecosystem carbon cycling across diverse grassland ecosystems.

Divergent responses of leaf-associated bacterial communities in grass and forb to long-term nitrogen enrichment in a temperate steppe

Abstract The frequency and intensity of extreme droughts are increasing and are predicted to be more severe in the coming decades. Clarifying the reasons for species-specific resistance to extreme drought is vital for predicting changes in community structure and ecosystem functioning. While the ‘slow-fast’ economics spectrum is widely used to explain inter-specific variations in ecological strategies, community assembly, and ecosystem functioning, its role in driving plant resistance to extreme drought is under debate. We examined the relationship between the resistance of plants to extreme drought (60% reduction in growing season precipitation) and the ‘slow-fast’ economics spectrum across 13 species in a temperate steppe. We found significant interspecific variations in the resistance of plants to extreme drought, with the dominant grass, Leymus chinensis, showing the strongest resistance. Extreme drought resistance was negatively associated with the slow-fast continuum, with higher resistance of slow-growing species than the fast-growing ones. Chemical traits were more important than morphological traits in predicting plant resistance to extreme drought. Our results provide direct evidence for the strong association between the plant economics spectrum and species-level resistance to extreme drought and call for more attention to species with fast strategy due to their higher vulnerability to extreme drought.

Effects of simulated nitrogen deposition on N fate in a temperate steppe: Evidence from multi-year 15N isotope study.

IntroductionAs a pivotal restoration strategy for alleviating grassland degradation, long-term enclosure practices effectively eliminate livestock disturbances while facilitating ecosystem self-recovery. Understanding the dynamics of soil microbial respiration under enclosure management is crucial, as it provides a scientific foundation for optimizing grassland utilization and contributes to global research on the terrestrial carbon cycle.MethodsWe conducted a comparative study across three distinct enclosed grassland ecosystems in Xinjiang, China: temperate desert, temperate steppe, and mountain meadow. Through analyzing microbial community structure, diversity, assembly processes, and respiration rates between 9-year enclosed and grazed areas, we identified key ecological shifts.ResultsThree key advancements emerged: (1) Enclosure implementation led to a marked improvement in soil resource availability, triggering microbial community shifts from oligotrophic to eutrophic states with substantial biodiversity increases (bacterial diversity: 2.2–14%; fungal diversity: 12.4–27.2%); (2) Divergent assembly mechanisms were observed where surface soil bacterial communities (0–5 cm depth) transitioned from 55.6 to 100% deterministic processes, directly contrasting with fungal communities that shifted from 11.1 to 55.6% stochastic dominance; (3) Partial Least Squares Path Modeling (PLS-PM) revealed distinct ecosystem-specific regulatory mechanisms underpinning reduced microbial respiration.DiscussionThe PLS-PM analysis detailed these distinct mechanisms: soil property-induced microbial metabolic trade-offs enhanced carbon use efficiency in temperate desert (R2 = 0.951), plant-mediated microbial assembly processes promoted efficient carbon cycling in temperate steppe (R2 = 0.455), and plant-driven suppression of microbial biomass dominated respiratory reduction in mountain meadow (R2 = 0.883). The research establishes that enclosure achieves carbon sequestration through divergent pathways across ecosystems, providing critical insights for optimizing grassland management strategies and enhancing climate change mitigation efforts.

Abstract The trait‐based root economics space provides a useful framework for understanding the nutrient acquisition strategies across species. However, it remains poorly understood how differences in anatomical features across root branching orders shape the root economics space. We measured order‐based resource economics and anatomical traits of absorptive roots of 32 perennial herbaceous monocots and dicots in a temperate steppe and examined the trait coordination across root orders to gain insights into the nutrient acquisition strategies of herbaceous grassland plants. We found that differences in proportion of cortex in root cross‐section and secondary growth drive variation in the root economics space across root orders of herbaceous species. In monocots, the absence of secondary growth resulted in a comparably consistent trait coordination across root orders. Specifically, the gradient of root collaboration with arbuscular mycorrhizal (AM) fungal constituted the main dimension of root trait variation, mediated by the proportion of cortex in the root cross‐section. In contrast, we found substantial variation in the trait coordination across root orders of dicots due to secondary growth. In lower order roots of dicots, mycorrhizal colonization rates varied independently of specific root length, but were negatively associated with root nitrogen (N) content along a principal component axis. These relations seemed to be due to the alternative root symbiosis with nitrogen‐fixing bacteria weakening the classic collaboration gradient within the root economics space. Importantly, our results demonstrate that the mycorrhizal colonization rates were more strongly correlated with the proportion of cortex than with root diameter in dicots. Consequently, secondary growth in higher order roots of dicots turned the widely recognized trade‐off between specific root length and mycorrhizal colonization rates into a positive correlation. Synthesis . Our study reveals the contrasting resource acquisition strategies of monocots and dicots across root orders, highlighting the fundamental role of root anatomical traits in shaping the root economics space. These findings provide valuable insights into how root anatomical traits predict plant strategies and set the foundation for exploring the potential influence of root anatomy on plant and ecosystem functions.

Under the combined effects of climate change, overexploitation, and intense grazing, temperate steppe in northern China is experiencing increasing deterioration, which is typified by a shift from structural degradation to functional disruption. Accurately tracking steppe degradation using remote sensing technology has emerged as a crucial scientific concern. Prior research failed to integrate ecosystem structure and function and lacked reference baselines, relying only on individual indicators to quantify degradation. To resolve these gaps, this study established a novel degradation evaluation index system integrating ecosystem structure and function, incorporating vegetation community distribution and proportions of degradation-indicator species to define reference states and quantify degradation severity. Analyzed spatiotemporal evolution and drivers across the temperate typical steppe (2013–2022). Key findings reveal (1) non-degraded and slightly degraded areas dominated (75.57% mean coverage), showing an overall fluctuating improvement trend; (2) minimal transitions between degradation levels, with stable conditions prevailing (59.52% unchanged area), indicating progressive degradation reversal; and (3) natural factors predominated as degradation drivers. The integrated structural–functional framework enables more sensitive detection of early degradation signals, thereby informing more effective steppe restoration management.

Simple SummaryThis study presents a large-scale field survey of the temperate steppes of Inner Mongolia, introducing a novel framework to classify vegetation based on root traits. The concept of root importance value was introduced, incorporating the architectural and functional indices of belowground roots, as well as the root life form spectrum. The present research reveals that these steppes can be categorized into three distinct community subtypes (meadow, typical, and desert steppe) and thirteen plant associations. The analysis uncovered a clear spatial gradient in root strategies, defining three ecological adaptation types. Furthermore, the key environmental drivers for each community were identified. Precipitation and soil nutrients are identified as key drivers shaping the spatial distribution of belowground root traits in meadow steppe. Water limitation was central in typical steppe, while desert steppe was influenced by altitude and temperature. This work provides a significant advance in understanding steppe ecosystems from a belowground perspective.The composition, architecture, and plant traits of temperate steppe communities are intricately associated with environmental factors. However, most studies primarily focus on aboveground observations, often overlooking the critical role of belowground root systems. Here we conducted a field survey at a large-regional scale to investigate the composition of temperate steppe communities and plant root traits. Cluster analysis, correspondence analysis and Pearson correlation coefficient matrix method were employed to classify vegetation associations based on plant community composition and root traits. The principal driving and limiting factors shaping plant root communities were systematically investigated. The results showed that the temperate steppe was categorized into three community subtypes: meadow steppe, typical steppe, and desert steppe, comprising five plant groups and thirteen plant associations. The RLFS analysis, based on belowground architectural and functional traits, demonstrated a spatial gradient differentiation with three ecological adaptations: tufted herbs, rhizome herbs, and non-tufted or rhizome herbs. Key environmental driving factors for meadow steppe included precipitation, soil carbon, nitrogen, and phosphorus content, while the average growing-season temperature as a limiting factor. The environmental driving factors for the typical steppe were not apparent, and the limiting factor was water. For the desert steppe, the environmental driving factors were altitude and average growing-season temperature. These findings reveal notable spatial heterogeneity and a distinct distribution pattern in community composition and vegetation classification based on belowground root traits in the Inner Mongolia steppes.

Extreme drought events may become more frequent with climate change. Understanding the impact of extreme drought on grassland ecosystems is therefore crucial for the long-term sustainability of ecosystems. Here, we identified extreme drought events in the Inner Mongolia grasslands of China using long-term standardized precipitation evapotranspiration index (SPEI) data and evaluated drought resistance of the vegetation under extreme drought based on net primary production (NPP). The impact of consecutive extreme drought events and multiple discontinuous one-year extreme drought events on grasslands were further analyzed to investigate the response strategies of different grassland types to different drought conditions. We found that the frequency and area of extreme drought in 2000–2011 were significantly higher than those in 2012–2020, and the Xilingol League region showed the highest frequency of extreme drought events. Under extreme drought, vegetation resistance was positively correlated, where annual precipitation > 300 mm. The mean resistance of different grassland types followed the order: upland meadow (UM) > lowland meadow (LM) > temperate meadow steppe (TMS) > temperate desert (TD) > temperate steppe (TS) > temperate steppe desert (TSD) > temperate desert steppe (TDS). In the analysis of two cases of consecutive two-year extreme drought, all grassland types except TSD and TD showed obvious decreased resistance in the final drought year, with the highest reduction (0.16) in LM during 2010–2011, implying the widespread and significant inhibition of grassland growth by continuous drought. However, under the multiple discontinuous extreme drought events, the resistance of all grassland types showed a fluctuating but an overall increasing trend, suggesting the adaptability of grassland to drought. The results emphasize that management departments should pay more attention to regions with low resistance and enhance the stability of grassland production by increasing the proportion of drought-resistant plants in reaction to future extreme drought scenarios.

Abstract Effects of climate warming on plant phenology have garnered significant attention in recent decades. However, the distinct and interactive effects of warming during growing and non-growing seasons on plant phenology remain unclear. Here, we aimed to study how seasonal climate warming influences plant phenology in a temperate steppe. Seasonal warming experiment was conducted in Inner Mongolian steppe using open top chambers. Flowering and fruiting times of six dominant species were observed from 2019 to 2020. Interactive effects between growing-season and non-growing-season warming on plant phenology were analyzed using linear mixed-effects models. Growing-season warming advanced the flowering and fruiting onset time, thereby extending the duration of both reproductive phases across the six monitored species. In contrast, non-growing-season warming delayed fruiting onset time by 1.83 days, but did not affect flowering time. Growing-season and non-growing-season warming interactively affected the onset time and duration of fruiting. Specifically, growing-season warming advanced the fruiting onset time by 3.89 days and extended the fruiting duration by 5.76 days in the absence of non-growing-season warming. However, growing-season warming only advanced fruiting onset time by 1.40 days and extended fruiting duration by 1.63 days under non-growing-season warming conditions. These phenological shifts were primarily driven by changes in air temperature and plant height. Our experiment provides clear evidence for the distinct and interactive effects of growing-season and non-growing-season warming on plant phenology, offering valuable insights for predicting future changes in terrestrial ecosystem processes under future global warming scenarios.