Effect of Different Measures for Protection and Restoration on the Plant Diversity in Yanchi County

Yanchi county,located in semiarid region in northwestern China,is taken for representative research example to study the plant community structure and species diversity influenced by different measures of vegetation protection and restoration.Four types of sample-plots were selected,which were old enclosure field,new enclosure field,rehabilitated field,nature grassland.Each index of the old enclosure field is respectively lowest.That is not to say,the longer the field is protected,and the better the vegetation restores and grows.Both integrated diversity indices and evenness indices of rehabilitated field are relatively higher than others.So it means that returning farmland to grassland is really a kind of reasonable measure for vegetation restoration.