| The desert-oasis ecotone in the middle reaches of the Heihe River is located in arid areas of northwestern China.Due to the special geographical location and climatic conditions,it is determined that the growth and development of the vegetation in this area is constrained by the moisture conditions,and the coverage of the vegetation is low and the patchy pattern is distributed.Due to climate change and the influence of human activities,vegetation growth in the region has been declining,and the process of desertification has intensified.Therefore,the study on whether the vegetation patch in the desert-oasis ecotone is stable and the factors that affect their stability is an urgent problem to be solved.Studies on the spatial pattern and stability and stability of vegetation patch can provide basis for the identification of dominant factors affecting the stability of vegetation patch pattern,and have important reference value for the protection of sand-fixing vegetation in desert-oasis transitional belts and the restoration and reconstruction of sand-fixing vegetation.Desert-oasis ecotone in the middle reaches of Heihe River as the research area,with high resolution images from 2012 to 2016 as basic information sources and with the support of GIS and RS technology,make full use of various research methods,such as remote sensing technology(RS),geographic information system technology(GIS),quantitative pattern analysis technology(Fragstats)and spatial statistics technology.Access to this area's landscape type vector graph and attribute database.Judge the stability of vegetation patch in the study area from 2012 to 2016 according to the change of vegetation patch and bare patch and the change of vegetation patch area,the change of the landscape index(vegetation patch area,number of vegetation patches,average area of vegetation patch,vegetation patch aggregation,landscape diversity index and landscape evenness index),the change of the stability index of the matrix and the stability index of vegetation patches.For environmental factors affecting the stability of vegetation patch in the study area,meteorological factors and soil factors are selected as environmental influencing factors affecting the stability of vegetation patch.Grey correlation analysis is used to analyze the influence of various factors on the stability of vegetation patch.The specific conclusions are as follows:(1)From 2012 to 2016,the area of vegetation patch in the study area increases,which is conducive to the fixation of soil material in the study area and slow down the process of desertification.;the total amount of vegetation patch area gradually decreases,and vegetation patches gradually tend to be stable.(2)From 2012 to 2016,the total change trend of vegetation patches area,the number of vegetation patch,the average area of vegetation patch and the degree of aggregation of vegetation patch in the study area increase,while the landscape diversity index and the landscape evenness index gradually decrease.According to the ecological significance of the landscape index,the vegetation patch in the study area is in a stable state from 2012 to 2016.(3)From 2012 to 2016,the overall change trend of the matrix stability index in the study area is reduced,and the overall change trend of vegetation patch stability index is increased.The stability index of landscape matrix is bigger than 1,and the stability index of vegetation patch is less than 1,but the trend is tending to 1.It can be seen that the landscape and vegetation patch in the study area are in a stable state from 2012 to 2016.(4)Through the analysis of the correlation between the change rate of landscape index and vegetation patch stability index in the study area from 2012 to 2016.It can be found that there is good correlation between the area of vegetation patch type,landscape diversity index,landscape uniformity index and vegetation patch stability.The stability of vegetation patch in the study area can be reflected by the multi-year changes in the area of vegetation patch type,landscape diversity index,and landscape evenness index.(5)Grey correlation analysis of meteorological factors(air temperature,precipitation,evaporation,wind speed and relative humidity)and vegetation patch area,landscape diversity index and landscape evenness index in the study area from 2012 to 2016.The result shows that the weather meteorological factor with the greatest grey correlation with vegetation patch,the index of landscape diversity and landscape uniformity index area is the temperature and the precipitation.Therefore,the meteorological factors that have a great influence on the stability of the patch are the temperature and the precipitation.(6)Through the gray correlation analysis of the soil factors(organic matter content and soil water content between 0cm and 120 cm soil depth,surface soil particle size distribution)and landscape index in the study area from 2014 to 2016.The result shows that: The grey correlation degree between soil factors and vegetation patch area,landscape diversity index and landscape evenness index are: 20~40 cm soil moisture content,0~10 cm soil organic matter content,10~20 cm soil organic matter content,silt,20~40 cm soil organic matter content.Therefore,the soil factors that have a greater influence on the stability o f patch vegetation in the study area from 2014 to 2016 is soil moisture content at the depth of 20~40 cm soil layer,soil organic matter content at the depth of 0~40 cm soil layer,and surface soil The content of silt,the most affected soil factor is the soil moisture content at the soil depth of 20~40 cm soil layer. |
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