# Trait-mediated linkages and stocking rate thresholds in plant-community-soil feedbacks to long-term grazing in a Stipa breviflora desert steppe

## TL;DR

This study examines how long-term grazing affects desert steppe ecosystems by analyzing plant and soil responses to different stocking rates.

## Contribution

It identifies nonlinear thresholds in ecosystem responses and trait adjustments in S. breviflora under varying grazing intensities.

## Key findings

- Species richness peaked at low grazing and declined sharply at higher rates.
- S. breviflora adjusted traits like root branching to maintain dominance under grazing.
- Soil ammonium nitrogen boosted richness, while nitrate and density inhibited it.

## Abstract

Stipa breviflora desert steppe serves as a critical ecological barrier in arid and semi-arid regions, where grazing represents the dominant land use practice. The regulation of stocking rate directly determines ecosystem structural stability and functional integrity. However, existing research has primarily focused on single components or short-term responses, lacking systematic analysis of multi-component synergistic responses under long-term gradient stocking rates.

This study utilized the Inner Mongolia S. breviflora desert steppe long-term grazing control experimental platform initiated in 2004, establishing four stocking rate treatments. We systematically measured community quantitative characteristics, multi-organ functional traits of S. breviflora, and soil physicochemical indicators. Data were analyzed using one-way ANOVA, Pearson correlation analysis, principal component analysis, and linear/nonlinear regression models.

Results demonstrated that species richness exhibited a unimodal (quadratic) response to stocking rate, with the highest richness under LG, followed by CK, and significant declines under MG and HG. Community aboveground biomass and height decreased consistently with increasing stocking rate. Concurrently, S. breviflora enhanced its relative dominance via coordinated multi-organ trait adjustments, characterized by reduced aboveground stature and leaf biomass, coupled with increased root branching and volume. Analysis of the multi-component system revealed nonlinear relationships among community, plant, and soil variables. Principal component analysis revealed a clear separation between ungrazed and grazed treatments along the primary axis, whereas MG and HG treatments converged, indicating a stocking rate threshold beyond which ecosystem responses became saturated. Soil ammonium nitrogen demonstrated significant positive effects on species richness, whereas soil nitrate nitrogen and bulk density exhibited significant inhibitory effects.

This study advances the theoretical framework of multi-component coupling in arid grassland ecosystems, providing direct scientific support for determining critical stocking rates and implementing precise restoration of degraded grasslands in Inner Mongolia S. breviflora desert steppe.