Research On Desertification Grade Evaluation Based On Multi-source Data

The classification of land desertification grades is an important part of desertification monitoring,and it is also the basis for comprehensive management and scientific protection of land desertification.Aiming at the problem that the single vegetation index method in arid or sandy areas occurs abnormally when extracting desertification information.This study uses series of Landsat satellite data,land cover products and statistical yearbook data in the period of 1990-2015 in Horqin area as the data source,through sample statistical analysis method,a desertification extraction model is proposed,which integrates three indicators:vegetation coverage(FVC),modified soil adjustment vegetation index(MSAVI),and enhanced vegetation index(EVI).The algorithm is applied to the dynamic monitoring of land desertification in the Horqin Sandy Land in the past 25years,and the driving force of the land desertification in the Horqin Sandy Land is further explored from the political,economic,demographic and environmental factors using the grey correlation method.The main content and conclusions are as follows:(1)Due to the influence of soil background and vegetation index oversaturation,the classification accuracy of land types with low and high vegetation coverage based on the traditional FVC method is low,while the three index methods of Albedo,BSI,and MSAVI have poor results for the classification of slight and moderate desertification land.Based on the traditional FVC desertification information extraction algorithm,this paper introduces EVI and MSAVI indexes,and proposes a desertification information extraction model that integrates three indexes of FVC,EVI,MSAVI,and compares the classification results with the FVC method and three-index method of Albedo,BSI,MSAVI to do accuracy evaluation.The research results show that:compared with the traditional FVC vegetation information extraction method,the algorithm proposed in this paper has higher classification accuracy,especially for arid/semi-arid regions.The fusion vegetation index method has better applicability and robustness;compared with the three index methods of Albedo,BSI,and MSAVI,and the multi-index fusion algorithm are more ideal for distinguishing lightly and moderately desertified land with higher accuracy.(2)Taking Kezuozhong Banner,Kailu County,Kulun Banner,Naiman Banner,Kezuohou Banner,and Horqin District as the research area,based on the decision tree classification method,using an improved multi-index fusion algorithm,carry out desertification grade evaluation,obtain thematic map of the current situation of desertification in Horqin District from 1990 to 2015,and analyze the change trend of different degrees of desertfication land in the study area.The results show that from 1990to 2015,the area of desertification land decreased by 3815.01 km~2,of which the area of mild desertification decreased by 1127.8 km~2;the area of moderate desertification decreased by 1603.86 km~2;the area of severe desertification decreased by 1083.35 km~2,indicating that the area of desertification land in the study area was roughly present a development pattern of"development-rapid reversal-stability".(3)With reference to previous studies,the driving factors affecting desertification area changes are divided into human factors,economic factors,environmental factors,and political factors.The influencing factors are qualitatively analyzed based on statistical yearbook data and meteorological data,and the method of gray correlation analysis is used to analyze and study the proportion and order of the impact of driving factors on the land desertification of various degrees in Horqin,so as to find out the dominant factors affecting the desertification of Horqin sandy land.The results of the study show that policy factors(forest area,grassland area)have a greater impact on the change of desertification land area,which explains China’s"Three North Shelter Forest"policy implemented in the1990s and the"returning farmland to forest"and"returning farmland to grassland"policies implemented in the early 21st century are conducive to slowing down the desertification process.At the same time,climatic factors(annual sunshine hours)and economic factors(livestock inventory)also play an important role in the degradation of the ecological environment.