Characteristics Of Soil Seed Bank And Diversity Of Plant Community On The Shore Of Dongting Lake Under Different Water Conditions

For revealing how the water regime influenced distribution of vegetation and soil seed bank, we examined the relationship between diversity (alpha and beta indices) of plant communities and soil moisture in Dongting Lake based on investigation of typical lake shore vegetation with transect (water edge, intermediate zone between water edge and grassland, grassland, intermediate zone between grassland and reeds, reeds) and quadrat. We analyzed the characteristics of soil seed bank using data from seed germination. We also compared the variation of vegetation and soil seed bank along wetland hydrological gradient and and the relationship between aboveground vegetation and soil seed bank. The result showed that (i) soil moisture content was diminishing from water edge to the reeds; (ii) species richness of lakeshore vegetation increased with the reducing soil moisture content, but the Shannon-Wiener index and seed bank density had no significant change (p>0.05); (iii) from grassland to reed area, the similarity between communities significantly increase (p<0.05) and species replacement rate (P diversity index) was nearly unchanged (p>0.05); the similarity between communities had significant reduction (p<0.05) and species replacement rate had significant increase (p<0.05); (iv) The number of species of humid group was more than the flooded group and the living form of vegetation was different between the two groups; (v) The similarity of species between the soil seed bank and aboveground vegetation in different bottomland were less than 0.200 and it was very low; aboveground vegetation species richness was generally higher than the seed bank.This study suggested that vegetation types and their diversity of Dongting Lake bottomland along the moisture gradient has significant change. When the water level is too low, the wetland vegetation to biochemical direction in succession will happen. When the water level is too high, the bottomland area will be narrow and the upper part in bottomland of zonal vegetation reverse succession will occur. Water level fluctuation will affect pattern of seed germination. Continuous watered-out state will seriously inhibit the germination of seeds, after that make the ground vegetation cannot update, plant communities decline, and feedback to the seed bank, ultimately make its size reduction. Once the reservoir construction of Dongting Lake is running, the original hydrological cycle will be broken. Due to the flooded disturbance, seed germination pattern will change and further change the original vegetation community. Ideal protection and management measures are to reduce human disturbance, reclaimed farmland and forest to flood-land, reduce the frequency of man-made water level change. In order to restore the original population of wetland, cannot rely on seed bank transfer technique, but also cooperate with targeted artificial measures.