Study On Coummnity Ecology In Ecotone Between Daxing'an Mountain And Xiaoxing'an Mountain

In June-July 2006, the vegetation was surveyed in the ecotone between Daxing'an mountain and Xiaoxing'an mountain, the survey was used with the point quadrate method to assess canopy structure and species diversity.This thesis, based on the survey of community plots, analyzed the relations of plant communities at ecotone between Daxing'an mountain and Xiaoxing'an mountain using the two-way indicator species analysis(TWINSPAN) and detrended correspondence analysis(DCA) methods, finally gave 7 community types. The result of DCA ordination shows that different plant communities and their distribution areas vary along the environmental gradient in the ordination graph. The results showed the rule of form of community, meanwhile reflected the route and process of history of the plant community. It can build academic of floras for the origins and distribution of characteristic species.Species diversity was selected with Patrick index, Simpson index, Shannon-Wiener index and Pielou index five factors. Environmental variables were analysed based on the principal component analyses (PCA) and Canonical Correspondence Analysis(CCA) to discuss the influence environmental variables to species diversity of plant community in ecotone between Daxing'an mountain and Xiaoxing'an mountain, the results show: species diversity was not richness in ecotone between Daxing'an mountain and Xiaoxing'an mountain, there were 896 species, 393 genus, 146 family, according to the datum of geography of the vegetation in Northeast China and the taxonomy of our laborary in ecotone between Daxing'an mountain and Xiaoxing'an mountain. But the author surveyed the 150 species, 80 genus, 45 family in ecotone in June-July, 2006. The more complex the species in community were, the higher the species diversity, on the contrary, the more simple the species in community were, the less the species diversity in ecotone. The species diversity was higher in Larix gmelinii+Betula platyphylla forest and lower in Larix gmelinii, Pinus sylvestris forest. The species diversity was higher in shade side than sun side. The relationship between species diversity and elevation were not significant. Three layers were divided tree layer, shrub layer and herb layer, whichhe species richness and Simpson index of three layers were showed: herb layer＞shrub layer＞tree layer, the Shannon-Wiener index was herb layer＞t.ree layer＞shrub layer, the Shannon-Wiener index and the evenness index Were tree layer＞herb layer＞shrub layer.Species and environmental variables were based the CCA analyse ,the total eigenvalue of CCA was 57.2%, 34.9.% of the variance was explained by the first two CCA axes, which were showed that the results were good. The axes were strongly correlated with latitude, CCA showed that major gradients in environmental variables influenced latitude. Correlated with elevation, soil moisture of soil, the total N of soil, the total P of soil and canopy density were presumed to be among the most important in influencing the distribution of plant community in ecotone between Daxing'an mountain and Xiaoxing'an mountain. Elevation, soil moisture, the total N of soil and organism of soil were not weaken.Elevation was significant correlation with species diversity, which was showed that the species diversity was effect by the elevation in tree layer. The species richness of herb layer was correlated with canopy density of community, the shrub layer was not significant.X~2 test with 2×2 contingency table and measure index were used to analyze the inter- specific association of community. Percentage co-occurrence, point correlation coefficient and Ochiai index were also applied to calculate correlations between dominant species. The results indicted that species with positive association had 267 pairs, 50.55%.The biological characteristics and demand similar habitats, and the relationships among species-pairs were of significant difference in different types of community. It was not difficult the positive association and negative association that the community was stable state. There are 22 pairs significant positive association, 18 pairs positive association, 11 pairs significant negative association through the X~2 test. The index of percentage co-occurrence more than 0.5 have 52 pairs, the Ochiai index have 145 pairs, the Dice index have 31 pairs.