The Study Of Seed Rain Of Alpine Meadow On The Eastern Qinghai-Tibet Plateau

As a potential community, seed rain plays important roles in maintenance of biodiversity. Although study of seed rain has been received more attentions and become an indispensable part of plant ecology now, compared with soil seed bank, it is still not enough in-depth and in-breadth, especially in alpine meadow on the Qinghai-Tibet Plateau. In this region, seed rain was comprehensively investigated, including effects of enclosuer on seed rain, differences of seed rain between typical-and swamp-meadow, the spatial variations of seed rain; furthermore trade-off between seedmass and dispersal ability was examined. The results showed that,1) There rich seed resources exist in the alpine meadow of eastern Qinghai-Tibet Plateau. The mean seed rain density per year in typical-, shrub-, swamp-meadow was 9825 seed·m-2·yr-1,2818 seed·m-2·yr-1,3471seed·m-2·yr-1, respectively.2) Through calculating Sorensen's similarity coefficient, the similarity between species composition of seed rain and standing vegetation was high, which was confirmed by the results of NMDS (nonmetric multidimensional scaling).3) In this region, the spatial variation of seed rain is prevalent, which reflecting in the spatial variation of seed rain density, within-and between-year variation of seed rain depending on location, the relationship between seed rain and standing vegetation changing with position.4) The seed rain density depends on seeds number of dominant species, which reflecting in peaks of seed rain density synchronizing with dominant species seed dispersal, the spatial variation of seed rain and between-year variation of seed rain density due to changes of seeds number for dominant species.5) The effects of enclosure on seed rain varied along years, but there are more Gramineae and Ranunculaceae seeds, fewer Gentianaceae and Rosaceae seeds in fenced plot than that of grazed one.6) Between swamp-and typical-meadow, the separation of species composition of standing vegetation was clearly, but that of seed rain was not obviously; which was confirmed by the results of NMDS.7) Most species abundance in seed rain depends on species relative abundance in standing vegetation.8) Trade-off between seedmass and dispersal ability was not supported by this study.To quantify seed rain, not only can help us evaluating the amount of seed resources in this region, but also can provide theoretical supports for the resowing measures for recovery of degraded alpine meadow in similar regions. To quantify the relationship between seed rain and standing vegetation can help us predicting the succession direction of degraded meadow following long-term enclosure or shift from swamp-to typical-meadow. Trade-off between seedmass and dispersal ability, as an evolutionary ecology topic, most studies were focused on population-level or model test, this relation examined in seed rain can provide community-level evidences.