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sur le développement des zones arides et semi-arides

Titre : Dynamic Change and Sensitivity Analysis of Land Desertification in Tibetan Plateau

Auteur : 刘文民

Grade : Master 2022

Université : Northwest A&F University

Résumé partiel
Known as the"Water tower of Asia",the Tibetan Plateau is the source of many rivers in East and South Asia and an important ecological security barrier in China.It is characterized by complex and special environmental factors such as climate,vegetation,topography,soil,hydrology and human distribution.The Tibetan Plateau is also one of the regions where desertification is widely distributed.Due to the influence of human activities and natural factors,the distribution pattern of desertification has high spatial and temporal heterogeneity.Therefore,the study of spatial and temporal distribution characteristics of land desertification on the Tibetan Plateau and the assessment of land desertification sensitivity can provide a theoretical basis for revealing the spatial and temporal dynamic changes and sensitivity characteristics of land desertification on the Tibetan Plateau,which is of great significance for land desertification prevention and regional ecological protection.In this study,the characteristics of land desertification in 1990,2000 and 2015 were identified by using Landsat remote sensing images to establish different types of desertification interpretation indicators based on field investigation and desertification characteristics in the Tibetan Plateau.Soil and vegetation characteristics of grassland with different degree of desertification in Haiyan county,Guide County and Gonghe County,the source region of Yellow River,were analyzed and analyzed by field samples,and the effects of land desertification on soil and biomass were clarified.Based on the driving factors of land desertification on the Tibetan Plateau,the evaluation index system of land desertification sensitivity was constructed,and the distribution maps of land desertification sensitivity in different periods were drawn,and the temporal and spatial variation of land desertification sensitivity characteristics on the Tibetan Plateau was clarified.The main conclusions are as follows :（1）The area of bare gravel land and semi-bare gravel land is the largest in different periods（1990,2000 and 2015）,and the variation range is 20.74×10 4-21.22×10 4 km 2 and10.32×10 4-10.51×10 4 km 2,respectively.The area of semi-fixed sandy land varied from3.76×10 4-3.95×10 4 km 2.The area of mobile sandy land and fixed sandy land is relatively small,ranging from 1.22×10 4-1.34×10 4 km 2.The area of wind-eroded mounds varied from1.97×10 4-1.99×10 4 km 2.The distribution of desertified land on the Tibetan Plateau gradually changed from sparse and small patches to planes from the southeast to the northwest.They are mainly distributed in river valley,middle river and lake basins of northern Tibetan Plateau,Qaidam Basin,surrounding area of Qinghai Lake,Gonghe Basin,source area of Yangtze river and Yellow River,yarlung Zangbo River and other major river valleys,and transitional zone of arid area in central and tidal flat.From 1990 to 2015,the areas of semi-fixed sandy land to fixed sandy land and exposed sandy gravel land to semi-exposed sandy gravel land were 945.52 km 2 and 2846.78 km 2,respectively.The area of semi-exposed sandy gravel land transferred to exposed sandy gravel land decreased from3410.59 km 2 to 247.97 km 2.

Mots clés : Land desertification ;Index system ;Soil physical and chemical properties ;Sensitivity of land desertification ;Tibetan Plateau ;

Présentation (CNKI)