Researches On Relationship Between Seed Rain And Community Structure In An Alpine Meadow On The Tibetan Plateau

The seed rain is an essential link in the plant life history dynamic process, by which may forecast that the species composition and the size of the soil seed bank as well as vegetation's regeneration and the succession tendency, The understanding of the seed rain dynamic is also great important for the plant population's supplement and regeneration. Therefore, at present, the seed rain and the soil seed bank research has become the quite active domain in the plant population ecology and the community ecology, and becomes more and more popular. However, at present seed rain's research in alpine meadow is relatively few, particularly on the Tibetan Plateau alpine meadow ecosystem.This experiment explained the relation between the seed rain and the dynamic of plant community structure in an alpine meadow on the Tibetan Plateau. By studying the seed rain's tendency in different spacial and temporal scale, as well as the species composition between the seed rain and vegetations in the local, we provide the theoretical basis for the protection of the alpine meadow ecosystem as well as the reasonable use and restoration of the degenerated grassland and the governance of "black beach". The main results were follows:(1) The alpine meadow seed rain has 60 kinds of plant seeds approximately which belong to 17 family. The seed density of the alpine meadow is approximately 2528/m2-15599/m2,which mainly include Gramineae, Cyperaceae, Ranunculaceae,Compositae,Scrophulariaceae,Gentianaceae,Leguminosae and so on.(2) The alpine meadow seed rain's dispersion may divide into three times which are the initial period, the peak period and the retrogression period. Seed rain start from the end of July to the mid-October in every year.lt is a ascending phase form the end of July to the end of September, but it is a degressive phase from the end of September to mid-October.Their descent concentrates mainly from the mid-September to early October, accounting for 78%-85% of the total quantity.At the end of September,the seed rain's descent achieve the peak point,occunting 42%-54%. Generally, seed rain's descent show the "single peak" mode,the abundance of the seed rain in different period is remarkable different.Annual dynamic Variation influenced besides by the illumination time,accumulated temperature and rainfall,the phenomenon of foison-poor harvest in seed production is an another important factors.(3) Seed rain's dispersion situation of the alpine meadow (seed rain abundance, species richness, species diversity) has the remarkable difference in the small sacle(between collector), the species composition of the seed rain has the heterogeneity in the small scale spatial distribution. In the large scale(between two test points), there is the same situation as in the small sacle.(4) Species composition of vegetation and the seed rain of the alpine meadow have the certain positive correlation.However,there are significant differences between the relative abundance of various species and the relative abundance of each specie of vegetation in seed rain.Gramineae sp.,Ranunculaceae sp.and Scrophulariaceae sp.and so on,their seed rain's relative abundance is higher than its vegetation's obviously. But, there quantity proportion in the seed rain are little actually. At the same time, seed rain's species abundance and the multiple indices of the alpine meadow are lower than its vegetation's obviously.(5) The main construction group of the alpine meadow, such as Kobresia capillifolia, Kobresia humilis, Kobresia setchwanensis and other Kobresia do not get the advantage in the seed rain. the superiority status in the ground vegetation of Kobresia and Elymus are mainly rely on the nutrition reproduction to maintain and consolidate.Their population's extension, although seed plays certain role, but the function of the nutrition reproduces is greater.