Study of species diversity evolvement process during vegetation restoration of abandoned farmland in the hilly loess plateau

This paper is a study about the species diversity evolvement process during vegetation restoration of abandoned farmland in the hilly and gully area of the Loess Plateau. Based on the community investigation and analysis of different abandoned field succession stages from 2, 6, 9, 13, 16, 19 , 25, 30 and 40 years, the results show that the succession series is Artemisia scoparia community→Lespedeza davurica community→Agropyron cristatum community→L.davurica and A. sacrorum community→Bothriochloa ischaemum community→B.ischaemum and L.davurica community→Stipa bungeana and L.davurica community→Sophora viciifolia community. From the analysis of vegetative life style during the succession process, we can conclude that the succession trend changes from the annual herb dominant community to the perennial herb dominant community, the subshrub dominant community and the following shrub dominant community. The vegetation restoration type is mainly Compositae, Gramineae and Legunminosae. In the ninth year of the succession stage, the Shannon-wiener diversity index, Pielou evenness index and Margalef richness index appeared maximum, fluctuant down during the stage 9 to 40 years. The minimal index is 25 years abandoned stage and then a little increase to the 40 years abandoned stage. The similarity coefficient analysis shows that the neighboring succession stages have much higher similarity coefficient, meanwhile the farther succession stages appear lower similarity. In this area, vegetation restoration process is very slow at abandoned fields, and much of the species are homology. The structure of community is simple. Through man-made disturbance (such as seeding) can solve the question mentioned above and accelerate vegetation restoration in the same time.