Effect Of Closed Forest On Plant Diversity In Several Small Watersheds

This dissertation relied on projects of European Union and World Bank Loan "Yangtze and Pearl River Watershed Ecological Rehabilitation", relating to37counties. From project counties Shihe small watershed in Yao’an, Baisheng small watershed in Yongshan in Yunnan province, Bamugou small watershed in Bijie in Guizhou province, Tianxianhe small watershed in Wanzhou and Shengshui small watershed in Yongchuan district in Chongqing, and Futianhe small watershed in Macheng in Hubei province were chosen as research small watersheds and a research had been carried out into changes of species composition of community, community types and plant species biodiversity by means of "spatial for temporal" in both closed forest plots and un-closed forest plots. The main results were showed as following:(1) In closed forest plots, the number of plant family, genera and species had increased in a certain extent, which meant that closed forest implement was good for individual tree invasion, settlement, growth and reproduction.A total of23vascular plant species representing21genera and14families were recorded in Futianhe small watershed closed forest comparison plots, while a total of26vascular plant species representing22genera and16families in closed forest plots. A total of44vascular plant species representing43genera and26families were recorded in Tianxianhe small watershed closed forest comparison plots, while a total of46vascular plant species representing43genera and28families in closed forest plots. A total of11vascular plant species representing11genera and10families were recorded in Shengshui small watershed closed forest comparison plots, while a total of21vascular plant species representing20genera and17families in closed forest plots. A total of46vascular plant species representing42genera and28families were recorded in Bamugou small watershed closed forest comparison plots, while a total of45vascular plant species representing42genera and25families in closed forest plots. A total of38vascular plant species representing36genera and19families were recorded in Baisheng small watershed closed forest comparison plots, while a total of53vascular plant species representing45genera and29families in closed forest plots. A total of27vascular plant species representing26genera and16families were recorded in Shihe small watershed closed forest comparison plots, while a total of35vascular plant species representing32genera and20families in closed forest plots. (2) The vegetation type and the formation had not been changed in research small watershed closed forest plots. According to vegetation’s classification principles of appearance-ecological and dominant species, the vegetation had been classed into1vegetation type,4formations and8associations with classification grade of vegetation-formation-association. The vegetation type in survey regions was subtropical coniferous forest, and four formations were Pinus elliottii forest, Pinus massoniana forest, Cryptomeria fortunei forest and Pinus yunnanensis forest.(3) General speaking, closed forest for5years was beneficial not only to increase of stand canopy in a certain extent, but also to increase plant diversity, such as Simpson index, equitability index and Shannon-Wiener index.However, arbor tree layer biodiversity in closed forest plots in Baisheng small watershed decreased maybe because of intermediate disturbance. Due to the arbor tree canopy increased, dominant species of shrub layer were broad-leaved tree species, which adversely affected the growth of herb in a certain extent, leading to the decrease of herb layer biodiversity of closed forest plots in both Tianxianhe small watershed and Bamugou small watershed.(4) For layers in the vertical structure of closed forest communities in research small watersheds, Simpson index, equitability index and Shannon-Wiener index of closed forest community plots were in the same, being shrub layer> herb layer> tree layer.And for layers in the vertical structure of un-closed forest communities in research small watersheds, Simpson index, equitability index and Shannon-Wiener index of closed forest community plots were in the same, being herb layer> shrub layer> tree layer, while the vertical structure of equitability index was shrub layer>herb layer> tree layer.(5) Dominant tree species populations in closed forest communities and un-closed forest comparison communities in Futianhe small watershed, Shengshui small watershed, Baisheng small watershed and Shihe small watershed belonged to a growth-oriented population, while dominant tree species populations in Tianxianhe small watershed and Bamugou small watershed stable population.(6) Closed forest for a forest had been promoting the progressive succession of the community, and the succession tended to improve the ecological benefits of the community.