The Analysis Of Diversity And Niche Of Forest Communities In The Xiaolong Mountain National Nature Reserve

Xiaolong Mountain National Nature Reserve is located in the western Qinling at the junction of the three natural regions in China, where terrain complex, and has less disturbed by human activities, and here vegetation in temperate broadleaf deciduous forest, and plant species is exceptionally rich. On the basis of the field survey, from the point of view of plant ecology, using the method of community ecology to discuss the species diversity and niche characteristics of Platycladus orientalis (Linn.)Franco,Fraxinus platypoda Oliv.,Betula albo-sinensis Burk., Castanea mollissima Blume, expectating to provide a theoretical basis for the establishment of plantations and sustainable development of Xiaolong Mountain National Nature Reserve community resources. For the study of species diversity, the results show:(1)17plots community diversity indicators show that the tree layer diversity index (H’) is0.9209; evenness index (Jsw) is0.7151; richness index (R) is4.0824; dominance index (C)is0.5652. Shrub layer richness index is20.4705; diversity index is1.4236; evenness index is0.4907; dominance index is0.3469; herb layer richness index is18.4705; diversity index is1.3314; evenness index is0.5509; dominance index is0.4778. The relationship between diversity index size is:tree layer<herb layer<shrub layer; The relationship between evenness index size is:shrub layer<herb layer<tree layer; The relationship between dominance index is: shrub layer<herb layer<tree layer; and the relationship between richness index relationship is:tree layer<herb layer<shrub layer.(2)The diversity index of Quercus aliena var. acuteserrataMaxim. in Xiaolong Mountain National Natural Reserve show:in tree layer, diversity index(H’) is2.0994, evenness index(Jsw) is0.819, richness index(R) is14, which are greater than the index average value (diversity index is0.9209, evenness index is0.7151, richness index is4.0824) of four communities; but its dominance index is0.218which is less than the index average value (0.5652) of the four communities.(3) The relationship of17forest species of Platycladus orientalis (Linn.)Franco,Fraxinus platypoda Oliv.,Betula albo-sinensis Burk., Castanea mollissima Blume community on different latitude richness index and the latitude show that:the species richness index of Platycladus orientalis (Linn.)Franco, Fraxinus platypoda Oliv., Betula albo-sinensis Burk. decreases significantly with increasing latitude; Castanea mollissima Blume richness index with increasing latitude showed increasing trend after the first drop; the diversity index, evenness index and dominance index of Platycladus orientalis (Linn.)Franco,Fraxinus platypoda Oliv.,Betula albo-sinensis Burk., Castanea mollissima Blume community is inversely relationship.(4) For different altitude communities, the relationship between species richness index and altitude indicated:richness index, diversity index, evenness index of tree layer shows upward trend with the increase in altitude, yet the dominance index shows downward trend with the increase in altitude. Diversity index of shrub layer and herb layer trend show the opposite tread with the tree layer.Using Levins and Shannon-Wiener niche breadth and niche overlap index to estimate niche of four communities, the results show that:(1) Built communities has the largest niche breadth, and the largest niche breadth index. In community, various groups has the same order of Bsw and B1value.(2) The majority of the population in the community niche overlap is generally low, indicating that the smaller competition between the majority population, and adequate environmental resources available in the community to share. But in Betula albo-sinensis Burk. community, the ecological overlap value of species is larger, this is related to the Betula albo-sinensis Burk., and Betula albo-sinensis Burk. in the forest areas as the associated tree species, therefore its dominant position is not very obvious;(3) Communities in constructive species and niche breadth populations has greater similarity with demand for habitat, which reflects they has the same shared trend with research and they relatively easier to mixed forest and constitute the backbone of the community. Which niche proportional similarity ratio above0.5average account for a large proportion, and shows they have a large degree of utilization of resources and have more intense competition.