Ecological Study On Endangered Mechanism Of Five Abies Species In China

Abies beshanzuensis, A. fanjingshanensis, A. yuanbaoshanensis, A. bashanzuensis var. ziyuanensis and A. chensiensis are national key protected wild plants with small population and scattered distribution. As endangered species, they need to be saved. Geographic distribution, climatic features, habitat, community and wild population characteristics were investigated to explore endangered mechanism of the five rare and endangered Abies (fir) species and protection measures. The main conclusions are as follows:(1) The five firs are scattered in East China, central south region and Qinba Mountains. Horizontal distribution range is narrow:25.4°-33.9°N,104.3°-119.2°E. Altitude range is1350-2500m. Temperature of entire area is low, which has abundant precipitation and high humidity. Requirements for water and heat are specific and ability to adapt volatility is poor. Heat factor has a greater impact on geographic distribution than moisture factor. The five firs have similar climate condition, and also differences.(2) Habitat characteristics of the five firs are similar. Human disturbance on A. bashanzuensis var. ziyuanensis is relatively intense. Community vertical structure levels of the five firs are clear. Canopy density of tree layer is high. There are bamboo plants in the shrub layer, and it is dense in local areas. Herb layer is sparse. Interlayer plants are different. Competition of the five firs is intense. In the communities of A. fanjingshanensis and A. yuanbaoshanensis, interspecific competition is more intense than intraspecific competition. But it is opposite in community of the other three firs. With the increase of diameter at breast height, competition intensity decreases. In general, communities of A. yuanbaoshanensis and A. chensiensis have more complex species composition and structure, higher species diversity index and greater community stability.(3) Population age structures of four firs (not including A. bashanzuensis) are irregular and populations appear to be a certain degree of instability. Population of A. fanjingshanensis has a serious shortage of seedlings supply, and a high mortality of small trees. Populations of A. yuanbaoshanensis, A. bashanzuensis var. ziyuanensis and A. chensiensis have adequate seedlings supply, but the mortality is high. Populations of four fir present as the growing type and tend to be the stable type. At different sampling scales, population is clumping distribution pattern. As age increases, clump intensity decreases.(4) Endangered reasons of the five firs include external causes and internal causes. External causes include climatic revolution, climatic change, human disturbance and community environment impact. Internal cause is mainly population’s natural reproductive capacity.1) Climatic revolution of geological era caused the five firs to be endangered species directly. And habitat insularization makes affect by amplified external stress.2) Because firs like cold and moist, warming climate creates a trend of moving upwards and northwards, which makes distribution area smaller and smaller until it disappears.3) Human disturbance narrows the range of its distribution, and reduces population.4) Community environment affects natural regeneration.5) Natural reproductive capacity is poor, which speeds up extinction in the wild. Protection measures for the five firs:restore microhabitat to improve habitat security degree, adjust the community structure to enhance population competition ability and natural regeneration capacity, strengthen nature reserve management, and carry out ex-situ conservation to expand wild population and distribution area.