Study On Change Law Of Species Richness Under Different Scales In Subtropical Evergreen Broad-leaved Forest

Plant community biodiversity means the diversity of compsition,structure, function and dynamics of communities.Understanding species composition is important to uderstanding community diversity.Using enlarging-scales field samapling and survey,the work reported in this thesis focused on community diversity and its change law under different scales through studying the biodiversity and variation characteristics of biodiversity in Nanjing South Subtropical Rain Forest and Yashu Mountain Evergreen Broad-leaved Forest in Fujian Province.There is not only a high diversity on vegetation and species,but also high varation of diversity patten under different sample areas in these two study areas.It is perfec transect for the research of biodiversity and change law under different scales. The spatial variation of species diversity in south subtropical rain forest and mid-subtropical evergreen broad-leaved forest were studiedcomprehensively in terms of flora characteristics,quantitative characteristics,species diversity and spatial pattern.The results are follow:In Nanjing South Subtropical Sain Sorest,there are vascular plants 65 families, 109 genera,180 species.There are vascular plants 73 families,117 genera,161 species.The compositions are quite similar in these two areas.The atural conditions are relatively stable.They offer superior natural conditions for plant.Hence,the species are rich,the tropical and subtropical compositions are high,floras are complicated,floristic origin are ancient.In the two forest,as the sample areas decrease,the number of species at A level frequency increases,otherwise,number at E level reduces.Mainly speaking,number of low frequency species are much higher,and the distributions of species are uneven. And frequency of species belong to tropical and subtropical zone is high.In the tow plots,number of species increases along the enlarging of sample area., and the scale of 64 m~2 can be thought as critical point in the relation of species-area. Under different scales(1×1m~2,2×2m~2,4×4m~2,8×8m~2,16×16m~2,32×32m~2,100×100m~2),the number species in Nanjing South Subtropical Rain Forest is respectively 7.67,15.47,31.29,60.46,84.99,88.60,138.8,and 7.58,13.88,24.04, 56.44,75.74,95.38,125.25 in Ninghua Yashu Mountain Evergreen Broad-leaved Forest. The slope variation of log(species)-log(area) in Nanjing plot is 0.51→0.49→0.14→0.21,that means along the increase of the sample area,number of species leaps at first,and then becomes gentle,and leaps again.The slope variation of log(species)-log(area) in Ninghua plot is 0.41→0.51→0.19→0.16,that means along the increase of the sample area,number of species leaps at first,and then becomes gentle.Judging from fractal dimension in Nanjing,1.75→1.76→1.93→1.89,when sample areas are less than 4×4m~2 and 8×8m~2,there exist similarity in community structures,and heterogeneity degree becomes significant along the enlargement of scale.When sample areas are less than 16×16m~2,heterogeneity degree becomes unsignificant along the enlargement of scale.When sample areas are 100×100m~2, variation degree of species composition and community structure is increasing,but not very significant.Judging from fractal dimension in Ninghua,1.79→1.75→1.90→1.93,when sample areas are less than 4×4m~2,heterogeneity degree becomes significant along the enlargement of scale.When sample areas are less than 8×8m~2,heterogeneity degree becomes significant along the enlargement of scale.When sample areas are less than 32×32m~2,heterogeneity degree becomes unsignificant along the enlargement of scale.When sample areas are 100×100m~2,variation degree of species composition and community structure is continueing decreasing.