A Research On Three Typical Seismic Landslide (Avalanche)Vegetation Natural Restoration Of The Longmen Mountains

This research use three typical sliding masses as research object. Compare vegetation character changes from before earthquake to after earthquake. Then analyse three different states-vegetation state before earthquake, damagement earthquake taken palace, recovery condition after earthquake based on landscape ecology. In the end, reach a conclusion that vegetation recovery character based on natural succession in sliding masses. Main results as follows:(1) Overall and fall slide type landslide almost Cryptomeria fortunei artificial forest before earthquake, vegetation coverage are80%,75%separately. Cryptomeria fortunei destroyed seriously when earthquake occured. Coverage has reduced20%,10%respectively. Debris slide type landslide has poor natural condition before earthquake, vegetation coverage is only50%, even only10%percent contrast to the level of before earthquake. Three years after earthquake, the coverage are50%,45%,8%in the three places respectively. The proportion shows that overall and fall slide type has remarkable recovery results during natural succession, but debris slide type not that good.(2) Overall and fall slide type has abundant species and species composition simplifition,are mostly Cryptomeria fortunei. Debris slide type is bringing the slope, Debregeasia orientalis is the most important species. Before earthquake, Overall slide type has total110species attach to60famlilies,80genera; Fall slide type has114species attach to69families,84genera; Debris slide type has24species attach to18families,21genera. At the year of earthquake, Overall slide type has33species; Fall slide type has36species and debris slide type only has10species. At the thrid year after earthquake, Overall slide type has69species; Fall slide type has62species and debris slide type has20species. After earthquake, Gramineae and Compositae entered the sliding mass first.(3) According to the a-diversity changes of different time in three type sliding masses. Before the earthquake, Overall slide type has the higest Shannon-Wiener index, and the lowest value year is the year earthquake occured. Ranking the Simpson index and Pielou evenness index:before the earthquake> three years after earthquake> the year earthquake occurs. Shannon-Wiener index reduced11.5%from before earthquake to three years after earthquake in fall slide type. And the sequence of fall slide type is as same as overall slide type. As for debris slide type, Shannon-Wiener index incresed43.5%from earthquake ocured to three years after earthquake, reduced34.9%from before earthquake to earthquake occured. The sequence of Simpson index, margalef abundance index and Pielou evenness index is also the same to the other two places. Community dominance C index of three landslides shows that the year earthquake occured appears the highest value. (4) According to the β-diversity changes of different time in three type sliding masses, the research get that plant community of the thrid year after earthquake has low similarity with the year of earthquake occured, but has high similarity with the state before earthquake. Overall slide type mass has the best plant community similarity. Then with times pass, the similarity of plant community will continue reducing between before earthquake and after earthquake.(5) According to the niche width changes at different period in different types of sliding mass. We can get that dominant species always changing during the research span in different types. Grass in overall slide type, massin in Fall slide type and Debregeasia orientalis in debris slide type gradually become the dominant species in different sliding masses. At the base of steady natural condition, competition between all species more and more intensify, an then vegetation state convert to more steady.(6) Use variance and ratio of averages measure main vegetation spatial pattern of different time in different sliding masses. The result shows the d-value of Cryptomeria fortunei in overall slide type much less than1before earthquake, present uniform distribution. Maberry and grass are present obviously aggregated distribution. In fall slide type, Cryptomeria fortunei in presents uniform distribution. Maberry, grass and mugwort are present obviously aggregated distribution before earthquake. As for debris slide type, Mountain hemp liu, Debregeasia orientalis and grass all express the distribution type of aggregation.Base on the analysis of plant community at different time of three typical sliding masses by using landscape ecological methods. Then we can get a conclusion that plant community which on two types of overall and fall slide type can recovery during natural succession. But the debris slide type can’t achieve natural succession without artificial measures.