Community Characteristics And Conservation Strategies Of The Thuja Sutchuenensis Franch.

Thuja sutchuenensis Franch.,the genus Thuja of the Cupressaceae,is rare and endangered gymnosperm plant in China.It is the first place to save and protect the wild plants in Chongqing and was listed in the first batch of key protected wild plant in Chongqing.At present,its wild population mainly concentrated in Chengkou Dabashan National Nature Reserve.Its mainly distributed in the altitude of 900 m~2 200 m,the danger area such as cliffs and ridges is mainly distribution,a few scattered distribution in the dense forest in.The population and the number of individuals of the remaining T.sutchuenensis are few,the distribution area is narrow,the environment condition is poor,and the severe living conditions.In recent years,affected by many factors,the population size and distribution has a tendency to shrink.In this paper,the methods of community interview and field investigation were used,combined with the research methods of community ecology developing studied for T.sutchuenensis habitat,flora,community structure,species diversity and niche,population and individual number,population age structure and community collocation model etc.,and draw the following conclusions:(1)The population of T.sutchuenensis was isolated into several smaller populations because of the habitat fragmentation,and “island” pattern.Based on the advantaged species CCA sequences that the slope,pH and soil water content of 9 environmental factors had a great influence on the survival of T.Sutchuenensis.In addition,light intensity is also an important factor.(2)The community had high level of biodiversity and species richness(182 species belonging to 156 genera and 75 families were found,most of which belonged to Rosaceae,Liliaceae,Compositae,Lauraceae,and Cornaceae families).The community had high level of associated species richness and life form of associated species is dominant of NanoPh,Hemicryptophyte,MicroPh.Areal types are complex and temperate elements are more in the community.The result of cluster analysis in the different sample plots showed that the altitude and spatial location were the important factors for influence the composition of the flora in the community.(3)There are 4 layers in the vertical structure of the forest layer,the T.sutchuenensis was mainly distributed in the vertical structure of shrub,lower and middle layers except upper tree layer.Gleason,Simpson,Shannon-Wiener diversity and Pielou index were high in the tree layer and shrub layer.(4)The T.sutchuenensisis dominant species in the tree layer of the community which is on top of important value(0.2251)and width niche breadth(6.7042),and has larger niche overlap than other species(Oij>0.1237).It indicates that the T.sutchuenensis has stronger ability to adopt the environment,to compete and utilize resources in the tree layer.The T.sutchuenensis living conditions is far from optimistic in the shrub layer.Although owning the biggest important value(0.1701),its niche breadth only ranks19th(1.8530).Also,The T.sutchuenensis has smaller niche overlap degree(Oij<0.4823)than other species which means the later is bigger than the former,Consequently,the T.sutchuenensis has a weaker competition ability in the shrub layer.(5)There were serious obstacles to population regeneration of T.sutchuenensis because of the discontinuous distribution of the diameter of individuals.Meanwhile,the remaining T.sutchuenensis population development was in an unstable environment,and the succession of broadleaf trees led negative influences on the regeneration of T.sutchuenensis.(6)When the community is dominated by shrub layer and lower tree layer,the number of individuals of T.sutchuenensis was more.We think that the average height of the community is shorter for expansion and regeneration of T.sutchuenensis populations the better.So that it is particularly important to build a suitable model for the expansion and regeneration of the T.sutchuenensis populations by combined with the vertical structure of the community and the period cutting,selective cutting,expanding forest window.(7)The protection of T.sutchuenensis population should give priority to the local protection,supplemented by ex-situ conservation.In situ protection at the same time,combined with the ecology principle to the existing of T.sutchuenensis communities for appropriate human intervention and were selected cutting or thinning for rapid growth of broad-leaved forest,appropriately enlarging the area of forest window to reduce the canopy density,strengthen the ventilation conditions of the community,promote the spread of pollen.In addition,actively carry out the artificial propagation technology and population regression study,through the seed collection,artificial seedling and tissue culture protection measures to expand the number of T.sutchuenensis population.