| The essence of desertification is the decline in land production capacity,which not only hinders the sustainable development of a regional socio-economic.But also a threat to the ecological security of a country.Therefore,it is the main content of desertification research to study the regional land degradation process monitoring,comprehensive evaluation index system of desertification,comprehensive evaluation method and prevention and control measures.In recent years,remote sensing technology has become the first choice of regional desertification evaluation because of its high precision,short return period and large coverage area,and also ensures the objective and accurate evaluation results.Based on remote sensing technology for long-term sequence,large-scale,quantitative desertification comprehensive evaluation has become the hotspot of desertification research.Based on the research results and the present situation of desertification based on remote sensing at home and abroad,the time series MODIS data were used as the main data sources.Four kinds of vegetation indicators(NDVI maxima,NDVI average,NDVI growth season and NPP)were identified by meteorological data and related auxiliary data,and try to find the optimal vegetation index suitable for desertification evaluation in Xilin Gol League based on ground measured biomass data,and adopt Sen + Mann Kendall trend analysis,correlation analysis and R / S Analysis and other methods,from the process-pattern-the next three aspects of the study area for nearly 15 years of desertification situation of remote sensing comprehensive evaluation and analysis,and the use of high-resolution meteorological data sets,quantitative analysis of different climatic factors on regional desertification contribution,So as to provide a scientific basis for the improvement of desertification remote sensing monitoring and evaluation methods and the management of vegetation and desertification in ecologically fragile areas.The main research results are as follows:(1)Using the remote sensing image data,high-resolution meteorological data sets and related auxiliary data in the study area from 2001 to 2015,the maximum value synthesis method and the improved CASA model were used to construct a variety of desertification Time series of vegetation index data sets.(2)The temporal and spatial characteristics of vegetation change in Xilinguole League in 2001 and 2015 show that the spatial variation of vegetation change is obvious,and the zonal changes of the vegetation are gradually increasing from west to east.On the time variation characteristics,the vegetation activity in Xilin Gol League is Enhanced,but did not show significant changes.(3)Based on the data of ground measured biomass,the sensitivity of different vegetation indicators to desertification was analyzed and the optimal index of desertification was given.The results show that NDVI_sum is the correlation between the accumulated NDVI data in the growing season and the measured sample data,which can reflect the real situation of the vegetation growth in the study area as a comprehensive evaluation index of desertification in Xilinguole League.(4)The effects of temperature and precipitation on vegetation growth in the study area were studied from monthly scales and seasonal scales.It was found that the correlation between precipitation and NDVI was higher than that of vegetation,indicating that precipitation was the main climate affecting the vegetation status in this area factor.At the same time,the correlation between different vegetation types,different seasons,temperature and precipitation and vegetation growth was different.Vegetation was negatively correlated with summer temperature and positively correlated with precipitation.The effects of precipitation in autumn and autumn on vegetation growth were higher than that of temperature.Temperature and precipitation have a greater impact on typical steppe and desert steppe.(5)Based on the comprehensive evaluation method of desertification using the optimal vegetation index,the desertification of Xilin Gol League was evaluated synthetically from the development process to the future development trend on the basis of the classification of desertification in the study area by K-means method.The results show that the spatial distribution of desertification degree in Xilinguole League shows the changing characteristics of desertification from west to east.The time and heavy desertification area was significantly reduced from 38.84% to 23.99%,the area without desertification increased from 1312% to 23.72%,the overall desertification level was reduced and the vegetation condition was improved.The future trend of vegetation is based on continuous improvement and degradation to improvement,only in some parts of the western region prone to degradation trend. |
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