Biological Diversity Of Vegetation And Floristic Composition In Urban Green Area Of Yinchuan City

With the accelerated process of urbanization, the natural landscape of the city has been changed, the original ecosystem has been destroyed, the diversity of urban plants has been threatened, and human beings are facing unprecedented challenges. Therefore, with the economy developing, how to reconcile man and nature, the city’s modernization and natural coexistence, sustainable development have became the theme of our era.The plant species composition, plant community characteristics and species diversity of the plant communities were investigated in 300 green area plots in Yinchuan city in this study. Through analyzing Richness index, Simpson index and Shannon-Wiener diversity index and Pielou evenness index of the layers of tree, shrub and grass, the level of the diversity of different types of green plants were found and the problems existing were point out in Yinchuan city. The research conducted in Yinchuan area provide reference for the construction of the plant diversity and green space planning in urban area with similar climate, aiming to guide the construction of urban landscape and improve the level of urban greening. The main results were as follows:(1) There are 246 kinds of plants in the study area, belonging to 72 families and 159 genera, including 12 species of gymnosperm, accounting for only 5%,234 angiosperm species, accounting for about 95%. Dicotyledons have 213 species, accounting for about 86.6%, Monocotyledon have 21 species, accounting for 8.6%.(2) There are 84 kinds of trees in the study area, accounting for 34.15%,54 kinds of shrubs, accounting for 21.95%,105 kinds of herbs, accounting for 42.68%. The ratio of tree, shrub and grass is about 1:0.64:1.25, the comprehensive ratio of evergreen and deciduous species is about 1:6.67. Annuals and biennial herbs have 32 kinds of species, perennial herbs have 73 kinds, the proportion of annuals and biennial herbs and perennial herb is about 1:2.3.(3) The floristic compositions in the study area were 78 kinds of species, mainly including several large families, such as Rosaceae, Leguminosae, Compositae, and the dominant genus,such as Sophora, Populus, Syringa.. In addition, there are 115 single species with the majority of herbs, accounting for 46.75%.(4) In the study area, there are 111 kinds of native plants and 135 kinds of exotic plant species, the ratio of native and exotic species is about 1:1.22. Flora analysis showed that the green plants investigated in the study area covered 13 geographical distribution, including 13.84% of the world distribution,20.13% of tropical distribution,66.05% of temperate distribution..(5) The average values of the richness index, Simpson index, Shannon-Wiener index, Pielou uniformity index of the tree layer were 3.73,0.58,1.07,0.856, the average values of richness index, Simpson index, Shannon-Wiener index, Pielou uniformity index of the shrub layer were 2.42,0.49,0.77, 0.856, and The those of the herb layer were 4.66,0.56,1.06,0.535, which the overall level of diversity is lower than that of other northern cities.(6) By analyzing variance of Shannon-Wiener of the tree layer diversity analysis in different types of green space in the Yinchuan city area, there was no significant difference of the diversity index between the park green space, square green space, unit green space and street green space (P>0.05), and they is lower than residential green space (P<0.05) and higher than road green space (P<0.05). For the shrub layer, there are significant differences between street green space, park green space and square green space (P<0.05), there was no significant difference between other types of green space (P>0.05). And the diversity of residential green space and street green space is higher, while park green space and square green space is lower. For herb layer, except there are no significant difference between part green space and road green space (P>0.05), there are significant difference of the Shannon-Wiener index among other green space (P<0.05). And the diversity index is the highest in unit green space, whereas those of park green space and road green space are lower.