Rest grazing start from the critical period of soil thawing optimizes plant community characteristics and grassland grazing capacity in alpine meadows

The grazing management of alpine meadows is very important for grassland health. In order to explore the optimal rest grazing period in cold season pasture of alpine meadows of the Qinghai-Tibet Plateau (QTP), the critical period of soil thawing–grass withering period (RP1), the later period of soil thawing–grass withering period (RP2), the initial period of grass regreening–grass withering period (RP3), the later period of grass regreening–grass withering period (RP4) and local traditional rest grazing (dominant plant height 5 cm–grass withering period) (RP5) was set in the Tianzhu alpine meadow on the eastern edge of the QTP. RP1 improved Gramineae and Cyperaceae coverage 140% and 37.80%, respectively, Cyperaceae aboveground biomass 58.52%, the total aboveground biomass 22.86%, and poisonous plants aboveground biomass was lower 29.39% than that in RP3. The Richness index and Shannon-Wiener index for the RP1 plant community were 12.12–24.72% and 2.46–19.75% higher than those in other rest grazing periods, respectively. The Simpson diversity index was 1.10% higher in RP1 than that in RP3, and the Pielou evenness index was 3.30% higher in RP1 than that in RP5. The neutral detergent fiber and acid detergent fiber contents of the plant increased with advanced rest grazing periods, being the highest in RP2. Crude protein, crude fat, and crude ash contents were the highest in RP5. The amount and digestible protein grazing capacities in RP1 were higher by 1.67–4.49 and 3.61–8.36 sheep units·ha − 1 , respectively, than those in other rest grazing periods. RP1 rest grazing optimized the plant community structure, improved grassland productivity and plant community diversity, with a more stable plant community structure and higher grazing capacity. Therefore, the cold season pastures should be managed with a rest grazing in RP1 for the sustainable utilization of grassland ecosystem.