| Vegetation is the sensitive index of ecological environment,and its interannual change is obvious,which partly reflects the characteristics of land cover change in the region.Regional ecological environmental quality can be reflected by the discretion of the vegetation coverage.Study vegetation coverage,understand its development and changes of time and space,can effectively assess the regional ecological service function,to provide scientific decision-making for regional environmental protection and animal husbandry development,and it is of great significance to maintain regional ecological balance.The geographical location of the ruoergai alpine plateau is special,and it is an important area in northwest sichuan to control desertification,prevent and control soil erosion and conserve water.From 2001 to 2016,this paper take five years as the time interval,selected four periods of data(2001,2006,2011 and 2016)as the time series,and studied the spatial and temporal variation of vegetation in the region.Selection of a series of Landsat remote sensing image as data sources,select the normalized difference vegetation index NDVI,set up a binary model,combined with mean method,differential method and standard method,analysis of the regional vegetation status.Moreover,from two aspects of natural factors and human factors further research for nearly 15 years zoige alpine plateau vegetation coverage of space and time change,to provide theoretical support and scientific basis for the sustainable development of the region.The main conclusions of this paper are as follows:(1)Study area in 2001,2006,2011,2016,four point,zoige alpine plateau area of vegetation is given priority to with high vegetation coverage.In 2006,the vegetation coverage was the best,and the area of extremely high vegetation coverage reached the maximum in four periods,accounting for 43.78% of the total area of the study area.In2011,the most serious degradation occurred,and the area of extremely low vegetation coverage and low vegetation coverage reached the maximum in four periods,accounting for 10.73 percent of the total area of the study area.(2)The stability of vegetation in the study area was mainly stable and strong in the overall perspective.Among them,the high stability vegetation occupies 49.98% of the regional area,indicating that the vegetation changes are not volatile and tend to be stable during the 15 years from 2001 to 2016.(3)In the analysis of the transfer area of vegetation coverage at different levels,the vegetation coverage in the higher grade is inclined to the lower one grade of vegetation cover transfer.From 2001 to 2016,a low level of transfer the vegetation coverage of vegetation coverage to the higher level with a total area of 1289761.20 hm2,higher levels of vegetation coverage to a low level of vegetation coverage with a total area of 1209088.17 hm2.(4)On analysis of the temporal variation of the vegetation in the study area,from2011 to 2016 years,the area of vegetation improvement was significantly increased,accounting for 32.93% of the study area,indicating that the study area vegetation was recovered and the ecological environment of the region was improving.(5)The change of vegetation coverage in the study area was analyzed from both natural and cultural aspects.In the analysis of natural factors,topographic factor analysis is the main factor,and the influence of topographic factors on vegetation coverage tends to be stable during the study period.The number of people in the study period and the region's GDP are growing rapidly.The vegetation coverage is negatively correlated with the population,which is negatively correlated with the first industry value of the region,and is positively correlated with the value of the tertiary industry,but the overall correlation is low.In addition,government policy also has a positive influence on the improvement of regional vegetation coverage. |
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