Studies On Ecological Protection Evaluation Of Dulan Oasis In Qinghai Province

In the paper, we chosen three closing areas in Dulan County of Qinghai province as study areas, investigation contents included plants number, coverage, density and biomass, using TWINSPAN and DCA, analyzed the relation between plants communities and environment, and depending on NDVI index assess plant recovery effect, the main results include:(1) There were 54 plant species. Using TWINSPAN method, the study area could be divided intosix communities. DCA result was same as TWINSPAN result.(2) Richness indexes, evenness indexes and comprehensive diversity indexes had the similar change trend, the result integrating there indexes showed that richness indexes and comprehensive diversity indexes of community V were greatest, and it it had great evenness indexes, its community structure was more complex and steady. Richness indexes and comprehensive diversity indexes of community II was low, but it had the most great evenness indexes, it had degradation trend. CommunityⅣhas great richness indexes but low evenness indexes, which indicated there wre abundant plants and dominant species occupied most resource space, competition among them was strong, so the community structure is less steady. By analyzingβ-diversity indexes, we could know the greatest similarity coefficient is the value of community I with community II. The similarity coefficient of community III with communityⅣwas the least. Niche overlap indexes of three study areas had similar results. The plants with the least niche breadths appeared in the same sample, and they had the greatest niche overlap index. niche overlap indexes of the plants with great niche breadths were not greatest.(3) Oasis technical system of ecological protection includes technical system of biology control and engineering control, technical system of biology control is consist of vegetation recovery and fencing technique, sand fixing afforestation technique and oasis protection forest technical system of engineering control includes mechanical sand barrier and chemical sand fixation technique. integrated control system is constructed, which combines windbreak and sand fixation system in outside of oasis, fencing system in sub-outside of oasis and farmland shelterbelt inside oasis.(4) Basing on NDVI, the grade map of vegetation coverage of different period in Tsagan Us oasis was extracted, and multi-year variation of vegetation coverage was quantitatively analyzed. The result showed that in the past 16 years, vegetation coverage of Tsagan Us oasis presented fluctuation-increase trend, the vegetation development had a good trend from 1990 to 2001 year, from 2001 to 2006 year, there also was a good trend, but there was degradation existed in some places.