The Study Of Soil Seed Bank In The Alpine Areas On The Eastern Qinghai-tibet Plateau

Seed bank is the major resource of vegetation restoration after disturbance, and plays a significant role in restoration and reconstruction of degraded ecosystem. At present, research on soil seed bank has become a recognized and indispensable part of plant ecology and has been an active research area. The degradation of plant communities, especially in an ecologically fragile area, such as in an alpine meadow community on the Tibetan plateau, has caused great concern of ecologists.Thus, with regard to the alpine grasslands on the Tibetan Plateau, what effect does increased fertilization have on the soil seed bank and consequently on the long-term revegetation potential of the vegetation (The fertilization gradient was established by applying different amounts of (NH4)2HP04. The quantity of fertilizer applied was 0 (control), 30g/ m2, 60g/ m2, 90g/ m2 and 120g/ m2). Then, the study on the mechanisms of plant community degradation will provide a theoretical basis for the recovery of the alpine meadow community.Our main objectives are as follows: (1) to test the response of seed bank species composition to environmental changes and explore the reasons that caused species composition change; (2) to explore the community composition of seed bank in different vegetation types; (3) To explore the potential of the seed bank restoration.Our main results are as follows:Species richness of both soil seed bank and vegetation declined in response to 9 years of fertilization, but rate of decline in the seed bank was slower than that in the vegetation. Seed density did not differ along the fertilization gradient except for Fer30 in spring, which had the highest seed density. Seed density did not differ along the fertilization gradient in summer. Plant density in the vegetation declined along the fertilization gradient.Proportion of annuals increased in both vegetation and soil seed bank along a fertilization gradient. Percentage of different functional groups in the soil seed bank changed but less than that in the vegetation.The similarity between soil seed bank and vegetation increased from FerO to Fer90 and then decreased in Fer120. The similarity between soil seed bank and vegetation was lower in summer compared with that in spring. Fertilization influenced species composition of the soil seed bank, but that effect was smaller than that on the aboveground vegetation.CCA analysis showed that phosphate and nitrogen are major environmental variables influencing the structure of soil seed bank and vegetation. These results also reflected a shift in seed bank and vegetation structure due to environmental eutrophication.There,rich resources of seed bank exist in the alpine meadow of eastern Tibet plateau. The mean viable seed density was 917 seeds m-2 - 3759 seeds m-2.The seed density and species richness of seed bank decreased with elevation increasing.Seeds of dicotyledonous plants are major components of soil seed bank in alpine meadow, and we found the highest proportion of dicotyledonous seeds in alpine shrub meadow and the lowest in saline-alkaline meadow. The highest proportion of monocotyledonous seeds was found in the forest edge meadow and marsh meadow.Among four functional groups, forbs was the one with the highest proportion of seed bank cross seven vegetation types, with the highest proportion of forbs seeds in alpine meadow and forest edge meadow and the lowest proportion in saline-alkaline meadow.Seeds of perennials are major components of seed bank across seven vegetation types. The highest proportion of annual seeds was found in the desertification steppe and forest edge meadow.The seed bank provides high species richness and high seed densities for restoration. Hence, we think the seed bank had a high potential for restoration of alpine areas on the eastern Qinghai-Tibet plateau.