Study On Quantitative Ecology Of Vitex Negundo L. Var. Heterophylla(Franch) Communities In Canyon Destrict Of Taihang Mountains, In The Southern Shanxi, China

Vitex negundo L. var. heterophylla (Franch) is one large shrub and, being an endemic species to China. It is distributed widely in Shanxi, especially in the Cayon district of Taihang Mountains. The community of Vitex negundo L. var .heterophylla (Franch) is one of the typical vegetation types in the cayon district of Taihang Mountains.The ecological relationship of species, community and environment of Vitex negundo L .var .heterophylla (Franch) communities were studied by using TWINSPAN and DCA. The results of TWINSPAN indicated that the communities were classified into 13 associations, and the classification matrix indicated two environmental gradients, light intensity and soil humidity. The first DCA axis showed the light gradient and the second axis reflected humidity gradient. The plant species diversity of 13 associations of Taihang Mountains was studied by using richness index (R₁), Simpson index ( λ ) , Shannon-Weiner index (H') and evenness index (E₃), respectively. The results indicated that the number of species in the obviously uneven, which lead to variation of X index and H' index among different associations. The indices of R₁ and H' increased firstly, and then declined slowly with the increase of elevation, which reach peak value at 760m, while E₃ index was unsteadiness. W Diversity indices decreased with the increase of disturbance of traveling and other human activity. Human disturbance can increase number of species with high tolerance to trampling and other pressure. It has less effect on evenness and species richness.The interspecific association and correlation of 26 dominant species of the Vitex negundo L. var. heterophylla (Franch) vegetation were analyzed by using x² -test, Pearson's coefficient and Spearman'scoefficient. The results showed that those dominant species composed 525 species-pairs;among these species-pairs, the extreme significant association or correlation were 5, 14, 15 respectively;and the significant association or correlation were 10, 6, 13, respectively. Species-pair, showing positive association or correlation, may have similar biological characteristics and similar eco-adaptability and niche overlapping. Species-pairs showing negative association or correlation may have different ecological characters, different adaptation and niche separation.