Cold-season grazing better sustains ecosystem multifunctionality than warm-season grazing in Tibetan alpine steppe

Grazing season profoundly shapes vegetation and soil properties in alpine grasslands, yet its effects on ecosystem multifunctionality (EMF) remain poorly understood. Here, we compared grazing exclusion (GE), moderate-intensity warm-season grazing (WG), and herder-managed cold-season grazing (CG) in a cold-season pasture of the alpine steppe on the Tibetan Plateau to evaluate how seasonal grazing influences species diversity, community biomass, soil physicochemical properties, and EMF. Relative to GE, WG reduced grass dominance but increased sedge and forb proportion, while also decreasing plant height and aboveground biomass (AGB), and lowered EMF. By contrast, CG was associated with higher plant diversity and significantly elevated soil total carbon (TC) while maintaining AGB at levels comparable to GE. Effect-size analysis showed that WG significantly reduced EMF relative to GE whereas the reduction under CG did not reach significance. Correlation and path analyses further indicated that, under WG, multifunctionality was chiefly associated with the biomass pathway, which was positive but insufficient to counterbalance the direct negative effect of grazing, whereas no significant plant diversity or soil nutrient pathway was detected. Under CG, EMF was jointly associated with plant biomass, plant diversity and soil nutrients. These findings highlight the critical role of grazing season in maintaining ecosystem multifunctionality in alpine steppe, suggesting that, in cold-season pastures of the central Tibetan Plateau, cold-season grazing represents a more sustainable strategy than warm-season grazing for balancing forage production and ecological conservation.