Effects of enclosure on seed rain of alpine meadow in the eastern Tibetan Plateau

Enclosure has been widely used in degraded grassland restoration as a brief and effective treatment, which changed microconditions of growth and production for plants. In the present study, the vegetation and the seed rain were investigated in enclosed and grazed plots after 8year enclosing on alpine meadow in the eastern Tibetan Plateau. The results showed that enclosure has significantly negative effects on species richness, Shannon index and individual density of vegetation, however, enclosure has significantly positive effects on richness and density of seed rain in enclosed plots compared with those in grazed plots. The changes of the numbers of Gramineae seeds played a key role in increasing of seed rain density. RAD (rank abundance distribution) displayed different patterns from enclosed plots to grazed ones. In enclosed and grazed plots, the pattern for seasonal dynamics of seed rain was unimodal. The Srensens similarity coefficient between seed rain and vegetation at fenced plots was higher than that at grazed plots, but the Srensens similarity coefficient between seed rain in enclosed plots and that in grazed plots was very high.