Effects of spring grazing on vegetation community characteristics of alpine steppe-meadow in the Qilian mountains

The characteristics of plant communities are one of the core aspects of grassland ecology and reflect the developmental direction of grassland communities. This study examined the alpine steppe-meadow of the Qilian mountains and analyzed the changes in characteristics (plant height, coverage, biomass, and diversity) of plant communities under different spring feeding rates 0 (CK), 30%, 50%, 70%, and 90% in the grazing year to determine the appropriate spring feeding rate of grassland meadow in the study area, which may provide a scientific basis for the rational utilization of grassland meadows of the Qilian mountains. The results showed that with an increase in feeding rate, there was a decreasing trend in the coverage and aboveground biomass of the community and Gramineae, importance value of Gramineae, and plant height of dominant plants in each functional group (Festuca kansuensis, Kobresia humilis, leontopoium nanum and Oxytropis ochrocephala). Additionally, there was no significant difference between the importance value and coverage of Gramineae at 30% feeding rate and the control (P > 0.05). Furthermore, the importance value and coverage of Cyperaceae increased, its aboveground biomass first increased and then decreased, and the maximum biomass was 45.6 g·m⁻² at 30% feeding rate. With the increase in feeding rate, no significant change was observed in the importance values of broad-leaved plants and poisonous weeds. The coverage and aboveground biomass of broad-leaved plants first increased and then decreased, and the maximum values of these two indicators were at 50% feeding rate. The coverage and aboveground biomass of poisonous weeds increased, and the values of these two indicators were similar to that of the control at 30% feeding rate. With the increase in feeding rate, the Shannon-Wiener index and Pielou evenness index of grassland plant communities were the smallest under 30% feeding rate and the largest under 90% feeding rate. There was no significant change in the Simpson index and species richness. The preliminary study showed that the suitable spring feeding rate of alpine steppe-meadow in the study area was 30% in the grazing year.