Variation In Plant Species Composition And Diversity Under Different Proportion Of Impervious Surface

In this paper,we took the proportion of the impervious surface in the underlying surface as an important indicator to reflect the extent of the urbanization and human disturbance to urban vegetation.According to the proportion,we classified the central city region to the lowest,low,moderate,high and the highest proportion region.Based on the research of 251 samples(600m~2/sample) in main urban region,we studied the composition of the underlying surface,and analyzed species composition,Structural characteristics in different proportion region.We also studied the laws that how the species adapted under different habitats.The main results showed:1.The number of plant community's family,genera and species all differed greatly among different proportion region of the impervious surface,but did not differ considerably among the lowest,low and moderate proportion region.There were 15 families,19 genera and 19 species as average value in the lowest proportion region, which was the most in all regions.While there were 15 families,19 genera and 19 species as average value in low proportion region,the number of species concentrated 5-36.The average value in moderate proportion region were same with the low's,and the number of species concentrated 6-30.There were 10 families,12 genera and 12 species as average value in high proportion region,and the number of species concentrated 1-18.There were significant negative correlation between impervious surface proportion and number of family,genera and species,and the correlation coefficient were respectively -0.618,-0.629,-0.628,and the correlation coefficient's test were all significant.2.The changing trend of species proportion of each life-form was consistent in different proportion region of the impervious surfaces.It all showed the phanerophytes occupied the most,followed by therophytes,chamaephytes,cryptophytes,and the hemicryptophytes occupied the least.The proportion of phanerophytes,chamaephytes,cryptophytes and therophytes did not differ significantly in plant community.While the hemicryptophytes differed in the lowest and the highest proportion region of the impervious surface,and the else did not differ significantly.3.The number of the native cultivated species,alien cultivated species and wildlife species all differed greatly among different proportion region of the impervious surface. There were significant negative correlation between impervious surface proportion and number of native cultivated species,alien cultivated species and wildlife species,and the correlation coefficient were respectively -0.409,-0.268,-0.555,and the correlation coefficient's test were all significant.Cultivated species and wildlife species did not differ significantly among the lowest,low and moderate proportion region,but when the proportion of the impervious surface continued to rise,the cultivated species decreased continuously.Wildlife species tended to decrease when the proportion of the impervious surface rose.4.The number of the native species,alien species all differ greatly among different proportion region of the impervious surface.There were significant negative correlation between impervious surface proportion and number of native species and alien species, and the correlation coefficient are respectively -0.593,-0.410,and the correlation coefficient's test were all significant.With the rising of the proportion of the impervious surface,the number of the native species dropped continuously,while the number of the alien species tended to go up at first,and then began to fall.5.In the different proportion of impervious surface areas,the changing trend of Patrick index was consistent in every layer of the plant community,and species richness were similar in the lowest proportion,low proportion and moderate proportion of impervious surface areas.With the proportion of impervious surface continuing to rise, arborous layer,brushwood layer,herbaceous layer and the total species richness of plant community were significantly decreased in each type of regions.6.The results of diversity indices indicated that the changing trend of Shannon-Wiener index and Simpson index was consistent in different proportion of the impervious surfaces.With the proportion rising of impervious surface,the diversity indices of arborescent layer dropped continuously,while diversity indices of brushwood layer and herbaceous layer went up at first,then began to fall,and reached the maximum value at moderate proportion of impervious surface.7.The pielou index of arborous layer and brushwood layer differed greatly in plant community of different area type,however,there was no significant difference in lowest, low and moderate proportion of impervious surface areas,and so was herbaceous layer. With the proportion rising of impervious surface,Pielou index presented a downtrend in arborous layer,nevertheless it went up at first,and then began to fall in brushwood layer and herbaceous layer.