To elucidate the multilevel drivers of stocking rate increase on plant community state transition in desert steppe， this study was performed in a long-term grazing manipulation platform （2004-present） in Stipa breviflora desert steppe of Inner Mongolia. Four grazing intensity treatments were established： no grazing （CK）， light grazing （LG，0.91 sheep units·hm^-2·half-year^-1）， moderate grazing （MG， 1.82 sheep units·hm^-2·half-year^-1）， and heavy grazing （HG， 2.71 sheep units·hm^-2·half-year^-1）. Based on data from 145 monitored quadrats in representative plots， a state transition probability matrix was constructed， integrating species interaction networks， functional group succession， and plant family closure analysis. The results showed that： （1） Plant population network complexity peaked during the stage of LG transition to MG （with only 4 isolated species）， whereas core species （e.g.， the disappearance of Teloxys aristata） reduced and isolated species sharply increased to 15 at the HG stage； （2） As stocking rate increased， the transition probabilities from shrub-subshrub （SS） and perennial forbs （PF） to perennial grasses （PG） rose， while the transition probability from PG to annual-biennial plants （AB） increased by more than 30% under HG； （3） The receiving capacity of the Poaceae （POA） strengthened with increasing stocking rate， whereas the biomass proportion of Asteraceae （AST） declined. In summary， a stocking rate exceeding 1.82 sheep units·hm^-2·half-year^-1 triggered the critical threshold for community degradation. In contrast， moderate grazing （LG-MG） maintained community stability through species redundancy， optimized resource allocation among functional groups， and the formation of closed-loop transitions between plant families. This study provides a multidimensional theoretical foundation for early warning of desert steppe degradation and targeted restoration.

Desert steppe  /  Stocking rates  /  State transition  /  Functional group succession  /  Multistable maintenance