关键词: 沙漠/沙地, 河流, 景观格局指数, 中国北方地区, 和田河, 西辽河

Abstract:

Interaction between aeolian and fluvial systems occurs widely on the surface of the Earth and plays an important role in the development of arid landforms. The most distinctive characteristics of dryland geomorphology by this interaction is that rivers are associated with deserts. Increasingly, more researchers have focused their study on the combination of desert and river landforms in arid zone. But such research are often limited to qualitative description of local areas and there have been fewer detailed examinations at a relatively large scale. Based on the principles of landscape ecology and with the help of GIS techniques as well as using landscape diversity and isolation indices, this article analyzes the characteristics of the spatial patterns of different landscape types of deserts and rivers in 12 deserts (sandy lands) within 10 watersheds in northern China, using the Hotan River as an example for the western regions and the Xiliao River for the eastern regions. The results show that on the whole, at the scale of watershed and sandy land, the landscape structure in the interior regions is much more complicated than that in the exterior regions, while its fragmentation degree is lower. Landscape structure is similar in the exterior regions. In the interior regions, however, landscape indices vary: from the west to the east, landscape diversity decreases, while landscape fragmentation degree increases gradually. At the scale of channel and sand dune, in the buffer zone, the structure of the dune landscape is comparatively more complicated in the Hotan River than the Xiliao River, but the fragmentation degree is lower. Landscape fragmentation is inversely related to the distance from the river course, that is, fragmentation degree decreases with increasing distance from channels, while richness increases with this distance. In terms of dune types, sand dunes in the Xiliao River basin are mainly fixed and semi-fixed, while in the Hotan River Basin, complex mobile dunes dominate. The proportion of the area of the main dune type decreases as their distance from the river increases. The fragmentation degree of different landscape types decreases as their distance from the river increases, but the main type of dune landscape becomes increasingly complicated further from the river course. Aeolian landform is a product of long-term interactions of various agents including water and wind, reflecting landscape heterogeneity at different scales. At the watershed/desert scale, climate, topography, vegetation, and hydrology dominate the formation of landscape patterns, while at the cannel/dune scale, the role of cannel patterns and directions of wind and water are more prominent. In future study, vector index should be introduced to make possible comprehensive analysis of the river corridor effect on desert distribution and to reveal the mechanisms and driving forces of river and desert landscape pattern formation in arid environments.

Key words: deserts/sandy lands, rivers, landscape indices, Northern China, Hotan River, Xiliao River