Study On Quantitative Ecology Of Gleditsia Heterophylla Communities In The Southern Tip Of Taihang Mountains, Shanxi

Based on the dataset, including 40 quadrats, from the filed in the southern tip of Taihang Mountains, Shanxi, the quantitative classification and ordination of Gleditsia heterophylla communities were conducted by using TWINSPAN and DCA, respectively. According to the results of TWINSPAN and the principle and methodology of vegetation classification from "Vegetation of China ", the Gleditsia heterophylla communities were classified into 6 associations, including Ass. Gleditsia heterophylla + Vitex negundo var. heterophylla - Carex stenophylloides+ Arthraxon hispidus, Ass. Gleditsia heterophylla + Vitex negundo var. heterophylla + Rhamnus parvifolia-Carex stenophylloides + Arthraxon hispidus, Ass. Gleditsia heterophylla + Vitex negundo var. heterophylla + Cotinus coggygria var. pubescens - Agropyron cristatum+ Carex stenophylloides, Ass. Gleditsia heterophylla + Vitex negundo var. heterophylla + Rhamnus parvifolia-Bothriochloa ischaemum + Agropyron cristatum, Ass. Gleditsia heterophylla +Vitex negundo var. heterophylla + Rhamnus parvifolia-Carex stenophylloides+ Arthraxon hispidus and Ass. Gleditsia heterophylla + Vitex negundo var. heterophylla - Carex stenophylloides. Moreover, the results of ordination by DCA for the quadrats and species shown that the distribution of those communities was dependent upon the slop direction based on the analysis for the 1st axis of DCA for quadrats, that was from sunshine slope to semi-sunshine slope. Moreover, it indicated that the differentiation of life-form of species in those communities, that is from mesophytes to arid-mesophytes. In addition, the 2nd axis of DCA had not significant ecological meaning, it was resulted from the scale was smaller as well as the heterogeneity of those community was not evident.The ecological species group of the 32 dominant species in Gleditsia heterophylla communities were analyzed by usingχ2-test, Spearman's correlation coefficient and Pearson coefficient of correlation, the result showed that the correlation of species-pairs in the shrub layer was obvious more than that in the herb layers, moreover, the ratio of positive association was less than that of negative association among the overall layers and among the communities, it suggested the Gleditsia heterophylla communities were at relatively stable stage. Based the cluster results of group averaging and their ecological characteristics, the 32 dominant species of this communities were divided into four ecological species groups:Gleditsia microphylla ecological species group, Vitex negundo var. heterophylla ecological species group, Rosa xanthina ecological species group and Lespedeza floribunda ecological species group, respectively.The niche breadth and niche overlapping of the 32 dominant species of communities were analyzed by Shannon-Wiener index and Pianka overlapping index, respectively. The results demonstrated that the niche overlapping value of the shrub layer was obvious more than that in the herb layers. The niche overlapping value between the populations was bigger when the niche breadth of both species was wider; and the niche overlapping value between the populations was smaller when the niche breadth of both species was narrower.