Cyclic formation of zokor mounds promotes plant diversity and renews plant communities in alpine meadows on the Tibetan Plateau

Abstract

Disturbance regimes are changing rapidly, along with the generation of patchy habitats, and the consequences of such changes for ecosystems will be profound. Plateau zokor mounds are a common natural disturbance on the Tibetan Plateau, and this disturbance leads to bare patches, and catalyse new paradigms of plant community dynamics in alpine ecosystems. We investigated, over 6 consecutive years, the dynamic changes of new zokor mounds, the effects of different zokor mound densities on plant diversity in alpine meadows at the spatial scale, and successional shifts in plant community on the bare mound patches at the temporal scale. The results showed that as the mound density increased, the species diversity and biomass of the plant communities (within mound-free regions between the mounds) significantly increased. Zokor mounds representing different successional stages comprise a mosaic and together constitute the alpine meadow. The cycle of plant succession on the bare mounds is about 6 years in length. The pioneer species were mainly rhizomatous grasses and broadleaf forbs. As succession progressed, the dominant species differed among the different mound patches. However, at the end of succession, the dominant species were grasses, and the species compositions were similar in the communities. The plant succession on the bare mound patches of the alpine meadow is a developmental process from founder-controlled to dominance-controlled communities. The coupling between patch-to-patch mosaic on different phases and year-to-year succession on bare mound patches is very important for species coexistence and promotes alpine meadow renewal.