[Study on ecoregion techniques of lake nutrients in Yunnan-Guizhou plateau Lake regions].

The primary objective of this research is to present an ecoregion model based on the principle components analysis (PCA), the cluster analysis (CA), the discriminant analysis (DA) and the spatial autocorrelation analysis (SAA), which were applied to establish the ecorigion of lake nutrients in Yunnan-Guizhou Plateau Lakes. First, the principle components analysis method was used not only to reduce the dimensionality of the feature space, but also to deal with new indexes. The accumulation contribution ratio of the four new indexes achieved 93.69%, which had the full representation. These complementary indexes which reflect the conditions of lakes were helpful to establish the index system of ecorigion of lake nutrients in Yunnan-Guizhou Plateau Lakes. Second, initial classification of lake drainage area was accomplished by new indicator values and cluster analysis which contained five classes, and then the categories of non-lake drainage area could be identified by the discriminant analysis. Finally, the cluster result was carried on the global statistics, Moran's I was 0.32 which was higher than 0, and the examination value Z was 68.28 which was higher than marginal value (remarkable level 1% correspond 2.58), it was indicated that the cluster result and the space position had the remarkable relativity, afterward spatial distribution pattern of the region was achieved by the quantificational analysis about over score of principle components and application of local spatial autocorrelation method. Then the ecorigion of lake nutrients was accomplished by the association and difference between different districts of the scattered regions' s spatial character. These results indicated that the ecoregion model initiated in the paper was appropriate and feasible to receive objective results and avoid artificial factors. Also it has provided a new method to explore the index system and techniques about the ecoregion of lake nutrients. Scientifically, the model was in favor of the foundation of lake nutrient criteria and eutrophication control standards in China.