Study On Vegetation Restoration And Diversity Changes In Xiejiadian Slip Mass

Xiejiadian slip mass was formed after Wenchuan Earthquake in 2008.The revegetation has progressed for 9 years.The surface of the slip mass has grown from the bare state in the beginning to the communities of tree,shrub and grass today.So far,the number of species in the plant communities in Xiejiadian slip mass is growing obviously with significantly increasing vegetation coverage.The importance of revegetation plays a basic role in the natural restoration.Taking the evolution of plant diversity as the start point and basic point of the study,this paper analyzes and compares the α diversity and β diversity of plant communities of different years at the slip mass,followed with thorough analysis of revegetation process and their current status.The major findings are as follows:(1)The survey in 2017 recorded 89 plants with a slight increase compared to the previous survey.The restoration effect of the plant communities has met the expectation and the stratification of plant community’s layers at the bottom of the slip mass is clear enough.The restoration progress at this part of the communities is fast.The mid and upper sample plots of the communities present a little bit lower degree of restoration,still occupied by the shrub and grass communities while the distribution range and plant number of trees are very limited.With the altitudinal gradient difference as the standard,in general,the restoration degree of communities rises as the altitude decreases.The α diversity of plant communities falls down in general,indicating the centralization of plant communities.The concentration of dominant species in the plant communities grows in total.β diversity of different sample plots varies noticeably,suggesting significant change in the species between different sample plots.Especially the rate of the species change is obvious and the restoration stage of different sample plots also varies a lot.Overall,the current structure of the plant communities is the tree,shrub and grass communities with Alder + Cryptomeria fortunel-Rubus tephrodes Hance + Hydrangea davidii Franch-Equisetum hyemale-Dicrano pteris pedata + Microlepia marginata.(2)According to the outdoor survey data in 2009,2012,2014,2015,2016 and 2017,this paper calculates α diversity and β diversity of plant communities of different years to draw a multivariate linear regression equation of α diversity and β diversity.The analysis result indicates that the revegetation progress of Xiejiadian slip mass is not a simple,linear one.It is identified that both α diversity and β diversity show significant fluctuations during the revegetation progress,suggesting that the alternation of species at the sample plots in different years is very frequent and the vegetation rate doesn’t remain unchanged all the time,but shows significant changes.Except for 2009,the overall structure of the plant communities in different years remains similar,but the composition of the communities still varies noticeably.According to the onsite survey data,space-and-space method could basically reflect the general trend of revegetation but couldn’t fully represent the growth trend of communities.(3)According to the principal component analysis based on the 6 years of plant survey data,α diversity could extract five major principal components and β diversity could contribute four major principal components.The principal component accumulated contribution rate of α diversity reaches 86.739% while the rate of β diversity reaches 88.775%.The analysis results of the principal component basically reflect the changing trend of α diversity and β diversity.Then,the clustering analysis of plant principal component reveals that the restoration of plant communities at Xiejiadian slip mass is overall ideal enough.Currently,the number of well-developed plant sample plots has occupied more than 2/3 of the total sample plots.The number of less developed plant sample plot only takes up 2% of the total number.According to the analysis result,the overall revegetation effect is good enough at Xiejiadian slip mass.With the restoration of vegetation,the local ecological environment has been greatly improved,the increase of plant species,the stability of slopes,and the frequency of secondary disasters have decreased,indicating that vegetation restoration has a significant role in promoting ecological restoration.