Study On Population Ecology Of An Endangered Plant Tetracentron Sinense Oliv

In this paper, the population, community and flora characteristics of Tetracentron sinense, a rare and endangered endemic plant in China, were studied systematically and comprehensively by using quantitative ecology methods through its field inevestigation, including community structure characteristics, species diversity, niche breadth and niche overlapping of dominant population, population structure and dynamics and population distribution pattern etc. Then, the current living situation of natural population of T. sinense was revealed, and its endangered mechanism and protection measure were discussed, which can contribute to provide some theory proof for protecting the germplasm resources of T. sinense and its sustainable utilization. The main results are as follows:(1) There were 80 species of vascular plants in Tetracentron sinense community in Meigu Dafengding natural reserve, belonging to 67 genera, 41 families, including 5 families, 6 genera and 6 species of pteridophyte, 1 family, 1 genus and 1species of gymnosperm, 3 families, 8 genera and 9 species of monocotyledon, and 32 families, 52 genera and 64 species of dicotyledo. The flora of carpophyte genera in T. sinense communities was complicated. The ratio of north temperate including north temperate and south temperate disjuncted and cosmopolitan is respectively 44.26% and 14.75%, indicating the significant characteristic of north temperate distribution. The vertical structure of community is relatively complicated, which could be divided into tree layer, shrub layer and herb layer. The richness index, species diversity index and evenness index in T. sinense community were all lower, indicating that it is in a certain stage of succession.(2) The two quantitative indexes, such as the niche breadth and niche overlap, of the main species’ niche in the tree layer of T. sinense community were quantitatively analyzed. The result showed that there were six populatios in T. sinense forests, and the importance value and horizontal niche breadth of T. sinense were significantly higher than other population, such as Acer franchetii, Padus brunnescens, Cercidiphyllum japonicum, Acer pictum subsp. mono, and Pterocarya stenoptera population. The horizontal niche breadth of Acer pictum subsp. mono and Pterocarya stenoptera were relatively higher than others, while the horizontal niche breadth of Padus brunnescens was lower than other species. There was a positive correlation between the horizontal niche breadth and the importance value. The horizontal niche overlap between the dominant species in T. sinense forests was relatively low. The vertical niche breadth of T. sinense was significantly higher than other populations except for Cercidiphyllum japonicum. The vertical niche overlap between the dominant species in T. sinense forests were all higher, including that the vertical niche overlap between Padus brunnescens and Acer franchetii or Pterocarya stenoptera, Pterocarya stenoptera and Acer pictum subsp. mono all came to 0.9, indicating their well regeneration and uniformly distribution in each height class of the community. The population with high or low niche breadth may had low or high niche overlap, such as T. sinense and Padus brunnescens, indicating no relationship between niche breadth and niche overlap of dominant species.(3) The age structure of T. sinense showed an inverted pyramid structure of recession. A static life table of T. sinense population was developed based on its DBH data. Survival curve, mortality curve, disappearance rate curve and four survival analysis curves were made to analyze population dynamics. The results showed that young individuals were fewer but old individuals were abundant. The survival curve of the population was to Deevey type II. The mortality rate and vanish rate curve of T. sinense population all showed two peaks in the 6th and 12 th age class periods. The population survival rate of T. sinense decreased monotonically, whereas the cumulative mortality rate increased monotonically. Four survival functional curves showed that the T. sinense population decreased very quickly at younger age, but grew stably at middle age and declined in old age.(4) The spatial distribution pattern and dynamics of T. sinense population in different habitats were studied by using seven distribution pattern indicators, such as dispersion index, clumping index, patchiness index, mean crowding index, negative binomial parameter, cassie’s index and morisita index. The results showed that: The distribution pattern of T. sinense population was clumped in different plant communities. Such spatial distribution of the T. sinense populations was closely related to their biological and ecological characteristics and habitat condition, which resulted from its long-term interaction between T. sinense and its natural environment.