Study on the Spatial Differentiation and the Evolution in Arid Regions——A Case Study for Oases in Heihe River Basin
ZHANG Bo 1, 2 ,\ ZHANG Kai\+1 (1. School of Geography and Environment Sciences, Northwest Normal University, Lanzhou Gansu 730070, China 2. State Key Laboratory of Frozen Soil Engineering, CAREERI, CAS, Lanzhou Gansu 730000, China)
Studies of the mass and energy spatial differential in the oases in arid regions greatly conduce to better understanding the natural background of the inhomogeneous oases formation and evolution and the characteristics of agricultural resources combination. The studies can offer a theoretical basis of rational agricultural allocation and optimum disposition of natural resources. The spatial differential of physical geography elements obviously appears in the oases of the Heihe River basin. The stability of climate becomes worse and worse from the upper reaches to the lower reaches, the annual precipitation gradually reduces from south to north, and the drought, together with desertification extent, increases gradually. The structure of geomorphology and the level of groundwater influence soil salinization. Under the basis of integrated analysis of the physical geographical elements of climate characteristics, geologic structures, geomorphologic evolution, surface water and groundwater hydrochemistry features, soil properties and water supply, the Heihe oases can be classified into three types, that is, higher position oasis, which is between 1 400 and 2 200 m a. s. l. with annual precipitation of 150～370 mm; the middle position oasis, which is between 1 100 and 1 400 m a. s. l. with annual precipitation of 60～110 mm, and the lower position oasis which is between 900 and 110 m a. s. l. with annual precipitation of 38 mm. Moreover, the climate suitability of main crops changing with slopes in every type of oases in the Heihe River basin is also analyzed. An important theoretical basis for optimum disposition of agricultural resources is provided.