Abstract
Land degradation is a great threat in the Heihe River Basin, located in the aridinland of northwestern China and land desertification is one of the main aspects ofenvironmental changes in this basin. Previous studies have focused on water resourceutilization and soil erosion, but the status of degraded land in the Heihe River Basin, suchas its distribution, extent and precise characteristics is often inadequately known. Based onfield observations and TM images from the year 2003, this study provides classificationand evaluation information concerning the degraded land in the basin of the Heihe River.There are five types of degraded land types in the Heihe River Basin: water eroded in thesouthern mountains, sandified and vegetation degraded near the oases, aridized in the lowreaches, and salinized in the lowlands. The total degraded area covers 29,355.5 km²,22.58% of the land in the study area. Finally, degraded land in the Heihe River Basin wasevaluated according to changes in the physical structure and chemical components of soils,land productivity, secondary soil salt, and water conditions.
Highlights
Land degradation is a great threat to the world, not merely as an environmental issue, and a social and economic problem
The types and classification system used for degraded land was defined based on the physical and social conditions of the basin
The degraded land was classified into five types in terms of land-use, aeolian landforms, vegetation cover, land productivity, landscapes, and soil: water erosion in the southern mountains, sandification and vegetation degradation near the oases, and aridization in the low reaches and salinization in the bottomlands with the help of a set of interpretation indicators from satellite imagery and with recommendations made by relevant researchers in China [26, 27], Visual interpretation was used to identify the types and extent of degraded land according to a certain image texture, e.g. dense stands of Sophora alopecuroides L., vegetation types and formation
Summary
Land degradation is a great threat to the world, not merely as an environmental issue, and a social and economic problem. Land degradation can be defined as a decrease in either or both the biological productivity and usefulness of a particular place, due to human interference [1]. It is a result of the complex relationships between nature and society on the local, regional, national, and global scales. According to Zhu and Wang [5], desertified sandy land increased by some 25,200 km during 1975-1987, about 40.5% of which distributed in the semi-arid agropastoral regions of northern China. It is essential to study land degradation processes in China [8]
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