Analysis On Plant Species Diversity Pattern Of Typical Evergreen Broad-leaved Forest In China

Evergreen Broad-leaved Forest(EBLF),one of the most representative vegetation types of subtropical zone in China,has been analyzed as a whole object here.Based on 186 plots,the diversity of plant species and geographic elements,the comparison between eastern and western part of typical EBLF were carried out.The large scale diversity pattern of species richness,αandβdiversity index along longitudinal and latitudinal patterns were studied.The main results were as follows:(1) There were over all 153 families,with 525 generas and 1654 species in the flora of typical EBLF in China.Composing 28 families,53 generas,165 species of Pteridophytes;8 families,14 generas,21 species of Gymnosperms;and 117 families, 458 generas,1468 species of Angiosperms.It suggested that the flora of typical EBLF in China was complex and diverse.Families which containing 5-20 generas,and more than 20 species were the most important part of the composition of families,while those small and medium-sized generas which containing 6-20 species and 2-5 species as the more important part in generas composition.(2) The floristic geographic elements analysis showed that the pantropic types were dominant in both family and genera levels.At the genera rank,subtropical types were relatively rich,this showed a development tendency from tropical to temperate.(3) The plant species diversity comparison showed that the moist typical EBLF in eastern China,contains more families,generas and species than the semi-moist typical EBLE in western China.As for the floristic geographic elements, tropical types play the dominant role in both eastern and western regions,with the west region being more obvious.(4) With the increased latitude and longitude,the community species richness exhibits a decreasing trend and a curve which increased at first and then decreased. The tree layer species richness has the same trend with the latitude pattern,but with the increased longitude it exhibits a decreasing trend.The latitude and longitude pattern in shrub layer species richness is very particular:with the increased latitude and longitude,the shrub layer species richness increased at first and then decreased in the curve and a increased straight line.The specific reasons need a further research. The herb layer species patterns are the same as the community species richness pattern,αdiversity pattern is similar to the species richness pattern,and almost showed the same tendency.This means that the species richness andαdiversity index trends to be uniform in a large scale.There is a significant negative correlation between shrub layer species richness and the altitude(p＜0.01),and a significant positive correlation between shrub layer species richness and latitude, longitude(p＜0.01),while a significant negative correlation shows between tree layer species richness,herb layer species richness and latitude(p＜0.05).And the same situation occurred in the Shannon-Wiener index.(5)βdiversity index pattern shows that it waves with the increased longitude and latitude.And a high species turnover rate is caused by a higher mountain or the acutely changed in the environmental conditions.βdiversity index has a close relation with the sampling scales.With a larger scale,βdiversity index is lower and the similarity is lower,too.By contrast,the variation range ofβdiversity index with latitude is more obvious than longitude,which shows that the latitude patterns withβdiversity index is more evident than longitude patterns.