Landscape changes of alpine grasslands in the Zhari Namco basin of the central‐southern Qiangtang plateau, 2001–2021

Abstract

AbstractThe alpine grasslands of the Qiangtang Plateau face significant ecological risks due to extensive human activities, particularly in areas along lakeshores and riverbanks, where overgrazing has caused severe degradation and salinization of the grasslands. Conducting fieldwork in such environments presents significant challenges for long‐term community‐scale landscape ecological research. In this study, the habitat characteristics of dominant plant communities in the alpine basin of Zhari Namco were quantified from three perspectives: topography, hydrology, and fractional vegetation cover. Using Aster GDEM and Landsat imagery, five grassland types were mapped for 2001–2021. Based on the spatial variables of area, shape, and distance, 13 landscape indices were selected to observe spatiotemporal changes. The results revealed several key findings: (1) The patch structure of the zonal vegetation Stipa purpurea steppe has undergone a pattern of dispersion‐aggregation‐dispersion in the past 20 years, yet the core habitat area remains unchanged by more than 52%, indicating fundamental stability in the southern Qiangtang alpine grassland; (2) Using the minimally grazed Kobresia pygmaea meadow as a reference, other communities exhibit stability similar to or approaching it, but with significant differences in aggregation level. The gradual expansion of grazing and economic activities has been a driving factor; and (3) Water conservation projects have diversified the use of water resources in river and lakeside habitats. Stipa purpurea + Carex moorcroftii steppe and Carex swamp meadow exhibit optimal carrying capacity, making them the only areas with relatively high sustainability. The study underscores that the current ecological benefits are a result of effective management. However, without proper management, the region could trend towards landscape fragmentation, becoming the most vulnerable zone in the watershed. Therefore, it is essential to strengthen retrospective analysis of grazing intensity and trend analysis of habitat changes to provide a scientific basis for local economic development and grazing management.