Seed Characteristics Determine Species Composition of Degraded Alpine Meadow Communities

Abstract

Abstract Climate change and human activities are increasing the disturbance to alpine meadows in Qinghai-Tibet Plateau, these changes are reducing the abundance of previously-dominant Gramineae and sedges, with forbs establishing dominance through secondary succession. Forbs replaced native Gramineae and sedges as dominant species. To explain the formation mechanism of this succession, this paper studied the seed characteristics of 14 common plants in alpine meadow communities, including seed number, 1000-grain weight, germination rate, pappus characteristics, fall velocity. It is revealed that seed pappus characteristics are the key factors in determining the dominance of species on the secondary bare land of degraded alpine meadows. The results of the comprehensive evaluation method show that Asteraceae have higher diffuse ability than Gramineae, sedges, Apiaceae and Leguminosae due to lower falling speed of Asteraceae, caused by their pappus. The redundancy analysis results further explain the reasons for the emergence of corresponding dominant species in different degradation stages of alpine meadows. These results are helpful for understanding changes in plant communities in alpine meadows under grazing disturbance. They also provide a theoretical basis for the sustainable utilization and management of the alpine meadow ecosystem and restoration of degraded grassland.