| Species diversity is the core of community ecology and is the basic level of biological diversity. Therefore, the species diversity has highly been paid attention and the maintaining mechanism of species diversity is becoming the hot spots to the biodiversity field. What’s more, the study of species diversity has great theoretical significance in the biodiversity protection, ecological restoration and ecological reconstruction and so on. To maintain species diversity, ecologists have already done many works; however, no general theory had been established, and many hypotheses (such as habitat heterogeneity hypothesis, species pool hypothesis) have subsequently been deduced. Before we start to know the maintaining mechanism of specis diversity, we should at first to measure the spcies diversity.With respect to the measurement of the species diversity,βdiversity is known as a degree or rate of the replacement of the species to explain a certain environmental gradient (longitude and latitude, altitude, etc.).The objects of this research are representing 100 families and 2086 tree species of the 462 genera in Yunnan Province, and studying districts covering 118 counties (districts, or cities) in Yunnan Province. The results are as followed:(1) Through linear fitting from 118 counties (districts, or cities) including trees species differentiation degree and each location at an altitude of heterogeneity degree, the coefficient of correlation R2=0.084 (P=0.001) between the degree and species/families altitude heterogeneity, number differentiation degree; and R2=0.153 (P<0.001) between the elevation with degree of heterogeneity of species and number differentiation degree. So, the degree of heterogeneity with altitude significantly influences on the tree species heterogeneity differentiation showing the trees species differentiation degree rising along with the degree of heterogeneity with altitude increasing. And the influence of number of species/genera of differentiation degree is significantly greater than that of species/families differentiation, and the heterogeneity degree of differentiation of genera level with the elevation is higher than that of family level. The results agreed that plant species and genera level could better shed light on the relationship between environmental heterogeneity and near, modern history and the environment; and family level better revealed the relationship between relatively long geological era and environmental heterogeneity. (2) To clarify the relationship between the size of regional tree library and its diversity from 118 counties (districts, or cities) under the regional conditions, the relationship was revealed by the regression analysis involving the relationship between the size of regional species library and its diversity which the coefficient of correlation is R2=0.36 (P<0.001); the regression coefficient is R2=0.30 (P<0.00]) between the size of regional species library (species most districts, or cities) and center (districts, or cities) species diversity, showing significant correlation and unsaturated relationship hypothesis. The results showed that center (districts, or cities) of species diversity will rise with the increase of species library size. Library explanation was 36% for most (districts, or cities) species of the diversity, higher than that of the surrounding (districts, or cities), which displayed it closely similar to the center (districts, or cities) species diversity. So, the maintenance of tree species diversity hinged on the size of regional species library.There exists significantly positive correlation between species richness and genera richness (R2=0.96, P<0.001) by analyzing the trees species richness and genera richness for per area. Positive correlation was also found between species richness and family richness (R2=0.80, P<0.001). And significant positive correlation was further detected between species richness and genera richness proving that genera level could be prior to display tree species richness (P<0.001). However, family level usually reflects the origin and zonal differentiation of species to limit the size of trees species library.(3) According to the species composition of 118 counties (districts, or cities) using DCA (detrended correspondence analysis) sorting,27 groups were roughly divided, but DC A sorting axis couldn’t meet the tendency of species composition related to the longitude and latitude gradients. The averageβdiversity is 0.9327 by Simpson Phase heterosexual index clustering. When the distance is 1.0, they are divided into 23 groups, and 6th,10th, 11th,12th,14th,15th,16th,17th,18th groups first clustered together abided by the geological distributions excluding 20th groups; 7th group (Jiangchuan county) separated from them deviated from the regional distribution; the rest counties (districts, or cities) are clustered with two or three counties, separately, which are neighboring to other counties (districts, or cities). When the distance is about 0.9, they are divided into 26 different groups, and Kaiyuan city separated alone.15 and 16 when the distance of 1.0 was subdivided into two subgroups,15,16 and 17,18. And when the distance of around 0.7, the 20th group when the distance of 1.0 was subdivided into four subgroups containing Honghe and Wenshan, South Yunnan, Northeast of Yunnan, Northwest of Yunnan, respectively. DCA sorting under different distances revealed the similarity of trees species composition from 118 counties (districts, or cities). The clusterings were in accordance with the neighboring locations or close apart, which showed higher similarity of tree species composition under the same region because the size of regional species library generally limited the real species library, and the regional restrictions influenced on the distribution of trees species.(4) To Yunnan Province 2086 trees species, at<5000 m altitude on families and genera of gradient, kind of three level regression analysis. Species (R2=0.623, P<0.001), are the (R2=0.682, P< 0.001), division (R2=0.828, P<0.001) The abundance of the peak in 1400 m respectively-1500 m or so,1100 m or so, the 1000 m or so, All well reflects the rising elevation with tree species richness show up first and then decline au model. Comply with the "moderate inflation" theory, but families and genera and species in the model and its peak au near the level of the corresponding value range in turn decrease. And families and genera, with the elevations of gradient degree of gentle in turn decreases, and among them, particularly level.(5) To 118 counties (districts or cities) in the gradient of trees, latitude onβspecies diversity of latitude analysed from with increased Sorenson similarity index is the tendency of increase. With the increase of latitude is the similarity of the species increases, namely the diversity is reduced, and "Rapoport" law consistent. S(?)renson similarity index with the increase of the longitude of the sharp rise in first, and when the index of about 1.5, namely longitude for 102°. The increase of the longitude of S(?)renson similarity index almost no effect. It inferred that:in the west species similarity difference and in the eastern region species diversity is more homogeneous. Use GDM (Generalized Dissimilarity Models) for latitude, longitude comprehensive effects of the tree species diversity Bray-Curtis index forecast analysis. That tree species composition of geographical distance, the differences of explicable for 18.3%. |
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