Vegetation Succession and Species Diversity Dynamics of the Plant Communities in the Loess Hilly and Gully Region

A two year experiment was carried out in Yulin to better understand dynamics of species diversity and vegetation succession of abandoned land in loess hilly region.Based on spatial sequence instead of temporal sequence method,analysis of vegetation succession law and species diversity dynamics with different restoration time and the research of 44 sample plots,the result showed that:(1) Plant community succession after 50 years of farming,a total of 58 kinds of herbs appeared in the survey sample plots,belonging to 20 families and 45 generas.Compositae,Leguminosae,Gramineae accounted for 51.1 percent and 60.3 percent of the total,which showed that these three families occupied a major position in the process of vegetation succession in the loess hills and gully region.(2) Species constitute presented as most species belonging to a small number of families,and a small number of species belonging to most families.the succession started with the dominant species,weeds of Chenopodiaceae,followed by annual herbaceous community,perennial rhizome herb community,herbaceous perennial community,till perennial rosette herb community,in which the succession had a trend of zonal vegetation and shrub stages.(3) In the later period of returning farmland to forests,vegetation succession gradually changed from perennial herb community to barren drought-resistant shrub.In the absence of human destruction,the succession would be moving to the direction that the climate and environment is very suitable for vegetation growth,eventually vegetation adapt to the local climate and get to the stable stage.