Against the backdrop of global climate change, altered precipitation patterns profoundly affect grassland ecosystems in arid and semi-arid regions. To clarify the spatiotemporal heterogeneity in the relationship between long-term precipitation variation and vegetation response, this study focuses on East Ujimqin Banner, Inner Mongolia. Utilizing 35 years of precipitation monitoring data (1983-2017) and field vegetation survey data from four key years (1983, 2009, 2013, 2017), nine Sums (townships) were categorized into three regions: northeast, central, and southwest. Methods including linear regression and ANOVA were employed to systematically analyze the long-term trends in precipitation and their relationships with the productivity and dominance of Stipa species, as well as community species richness. The results indicate that: (1) The long-term precipitation trend exhibited spatial heterogeneity, with more pronounced interannual fluctuations and a higher rate of change in the northeastern and southwestern regions compared to the central region; (2) Vegetation sensitivity to precipitation change displayed a pattern of higher responsiveness in the periphery and lower in the central region, as the response slopes of Stipa fresh weight, importance value index, and total community fresh weight per unit precipitation change were significantly greater in the northeastern and southwestern areas than in the central area. (3) Stipa populations showed a tendency to shift from the northeastern and southwestern regions toward the central area. Concurrently, species richness increased in the peripheral regions as Stipa declined, while it temporarily decreased in the central region. This study reveals the specific process of spatial range shifts in dominant grassland species and the reshaping of community structure driven by climate change, elucidating the regional differentiation in ecological sensitivity. It provides an important scientific basis for adaptive grassland management and biodiversity conservation in the region.

Abstract: To elucidate the driving mechanisms behind plant community state transitions in desert steppe under grazing disturbance, this study established a long-term monitoring platform (initiated in 2004) in Stipa breviflora desert steppe in Inner Mongolia. Four stocking rate gradients were implemented: no grazing (CK), light grazing (LG), moderate grazing (MG), and heavy grazing (HG), ranging from 0 to 2.71 sheep units·hm⁻²·half-year⁻¹. Plant population characteristics were surveyed across 145 quadrats. Using mean occurrence probability combined with transition probability models, this research quantifies the patterns and characteristics of mutual transitions at three levels—species, functional groups, and plant families—during state shifts induced by varying stocking rates. Results demonstrated that: As stocking rate increased, the species network shifted from a single-core hierarchy (dominated by Stipa breviflora) to a multi-core complex network, eventually simplifying into a sparse network governed by grazing-tolerant species under heavy grazing. Perennial grasses (PG) exhibited the highest grazing tolerance, receiving up to 43% of transition probability from other functional groups. Shrubs and semi-shrubs (SS) maintained system functionality through self-sacrifice (27% transition probability to PG during the MG stage), while annual-biennial plants (AB) acted as ecological bridges during state transitions. Poaceae (POA) consistently received resources (probability of OTH→POA increased to 52%), reinforcing its dominance, whereas resource transfer from Fabaceae (FAB) to POA (24%) intensified nitrogen limitation and triggered system state transition. In summary, a stocking rate≤1.82 sheep units·hm⁻²·half-year⁻¹ maintains multistability in S. breviflora desert steppe. Species, functional groups, and plant families revealed distinct response strategies during state transitions, whose salient manifestations and synergistic interactions provide a theoretical basis for adaptive management in desert steppes.

Overgrazing is a key driver of degradation in Inner Mongolia’s desert steppe, where high stocking rates exacerbate wind erosion, thereby compromising ecosystem stability. This study examined Stipa breviflora desert steppe under four stocking rate gradients (0, 0.91, 1.82, and 2.71 sheep·hm -2·year -1), analyzing total nitrogen (TN), total phosphorus (TP), and N:P ratios in soil (0–30 cm depth), aeolian sediment (0–30 cm above ground), and plant communities to assess their homeostatic responses. The conclusions as follows: (1) Grazing significantly reduced plant TN and TP ( P < 0.05) while increasing plant N:P, whereas soil exhibited the opposite trend—TP decreased and TN accumulated, elevating soil N:P; (2) Homeostatic regulation varied with grazing intensity—under light grazing (LG), plant TP homeostasis stabilized (H = 4.84), while moderate grazing (MG) prioritized TN homeostasis (H = 20.37); heavy grazing (HG) only partially maintained homeostasis via N:P adjustment; (3) Aeolian sediment nutrient dynamics significantly influenced plant homeostasis ( P<0.01), enhancing it under LG and MG but not HG. Mechanistically, HG disrupted N-P homeostasis, depleting plant TN and TP while reducing soil TP and accumulating TN (due to excreta input-uptake imbalance), shifting the system from N- to P-limitation. At ≥2.71 sheep·hm -2·year -1, vegetation loss impaired windbreak function, and grazing-wind erosion synergy pushed the system into a ”non-homeostatic” state. This study validates the ”grazing-wind erosion synergy” theory, highlighting the need for state-dependent management (homeostatic vs. non-homeostatic): LG and MG allows wind-driven nutrient redistribution, whereas HG requires strict control to prevent irreversible degradation.

A high stocking rate can intensify wind erosion in grasslands, and strong wind can carry away soil surface particles and their nutrients, which leads to soil barrenness. In this research, the dust flux, total carbon (TC) and total nitrogen (TN) contents and fluxes of aeolian sediment were computed in the non-growing season (mid-October to mid-April of the following year) and growing season (mid-April to mid-October) from 2018 to 2020 at a long-term grazing gradient experiment platform and wind-erosion monitoring experiment in a desert steppe in Inner Mongolia, China. The results were as follows, 1) with the increasing of stocking rate, the fluxes of aeolian sediment at 10 cm (H10), 30 cm (H30), and 100 cm (H100) were greatly increased ( P<0.05). Aeolian sediment fluxes followed the order control (CK) < light stocking rate (LG) < moderate stocking rate (MG) < heavy stocking rate (HG). 2) TC and TN contents of aeolian sediment reflected stocking rates and followed the order CK>LG>MG>HG, and also reflected aeolian sediment collection height, as H10P>0.05). TC and TN contents in HG at different heights reduced by 31.1% and 25.9% on average in comparison to the CK in the non-growing season, and by 30.1% and 25.0% in the growing season. TC loss was higher than TN loss. Overall, as stocking rate increased, wind erosion increased, leading to the loss of soil nutrients and significant loss of the carbon pool in this desert steppe.