Abstract: Aims Plant functional traits influence plant growth and resource allocation strategies. and their plasticity in response to environmental changes makes them robust indicators of plant adaptation to grassland management practices. In the Yili River Valley region, Sophora alopecuroides (a dominant poisonous weed species) poses severe threats to grassland ecosystems and livestock production. Investigating how different grassland management practices affect the functional traits of S. alopecuroides is therefore crucial for understanding its growth-survival strategies and restoring degraded grasslands. Methods This study set up field control experiments, including four grassland management measures: grazing + mowing, grazing, fencing + mowing, and fencing, to explore the changing characteristics of functional traits and resource balance strategies of S. alopecuroides. Important findings The results showed that: (1) Under the grazing management, S. alopecuroides exhibited the lowest specific leaf area and the highest leaf dry matter content. Under grazing + mowing and fencing + mowing treatments, S. alopecuroides exhibited significantly higher leaf nitrogen content and leaf phosphorus content, but significantly lower leaf carbon - phosphorus ratio and leaf nitrogen - phosphorus ratio. Fencing resulted in higher leaf area, specific leaf area, leaf dry matter content, and leaf carbon concentration. (2) Fencing + mowing and fencing significantly increased specific root length and specific root surface area (P < 0.05). Root tissue density was highest under grazing + mowing. Root carbon, nitrogen, and phosphorus concentrations and root stoichiometric ratios did not differ significantly among the four management practices. (3) Under grazing + mowing and grazing treatments, S. alopecuroides lost the leaf-root synergy in its whole plant economics spectrum, resulting in a strategies reallocation of resources between above- and below-ground organs; whereas fencing + mowing treatments promoted resource-acquisitive strategies. This study elucidates the resource trade-off strategies of S. alopecuroides under contrasting grassland management regimes, while providing theoretical foundations for controlling this poisonous weed and restoring degraded steppes in the Yili River Valley.

Key words: Plant functional traits, Sophora alopecuroides, Poisonous weed, Grassland management practices, Degraded steppe.