ECOLOGICAL CHARACTERISTICS OF SOIL WATER AND ITS RELATIONS TO LANDFORM AND VEGETATION IN A SMALL SEMIARID WATERSHED IN A LOESS HILLY AREA

Abstract There is an urgent need to study soil water resources and eco-hydrological characteristics in depth so as to carry forward ecological environmental construction in the Loess Plateau. Soil moisture was measured to a depth of 5 m on 11 sites with different landforms and landuses in a transect of the Zhonglianchuan watershed during 2002. The watershed is located in the northern Yuzhong County, Gansu Province, and is part of a semiarid and loess hilly area. There were different types of soil moisture variations within the year of 2002 on the 11 sites. Soil moisture contents were low on all sites, and the averages of 2 to 5 m depth were usually lower than 10% by weight, in which the lowest water contents were in soils of the sloping land under the Medicago sativa and Caragana korshinskii vegetations. The dry soil layer is common in this area, not only under the planted vegetation but also under the natural vegetation. The soil moisture in a slope segment or area can be increased by collecting and harvesting surface runoff from upslope areas. One effective way to collect runoff is the level terraces alternated with sloping lands. The proportion of various grasslands, the proper acreage of alfalfa, and the sustainable development of the region should be further studied in order to successfully return cultivated land to grassland. Additional Keywords: ecological environment; dry soil layer; rainwater harvesting technology; Gansu Province Introduction The main factor restricting ecological environment construction of the loess plateau is the shortage of water resources, especially in the semiarid loess hilly areas. The severely dissected landforms on the loess plateau formed thousands of small watersheds. A survey showed that there are more than 8000 small watersheds in China, and a greater portion of them is located in the loess platea