Land Use And Cover Change (LUCC) In Horqin Sandy Land Based On The Grain Size Distributions Of Different Land Types

Land use and cover change(LUCC) is an important component that the present global environmental change studies. In sandy land areas, LUCC caused by mankind unreasonable economic activity and fragile ecological environment interaction, it is a series of development that drop of land productivity, reducement of land resource, the land type and land coverage rate changed. Horqin sandy land lies in the eastern of the northern agriculture and animal husbandry interlock zone, climate belong to temperate zone semi-arid and subhumid intermediate zone, the ecological environment is fragile, the desertified degree is being aggravated constantly in recent years, it is one of the comparatively frequent areas that northern desertification activity of our country. Because of the particularity of its geographical position, and the environment impact is the most sensitive too, land use and land cover changed obviously. When the ecology environment was destroyed by human excessive utilization of land resources, such as over grazing, steppe reclamation and collection of fuelwood etc,under the conditions of drought. Too much area of sandy sparse wood grasslands degraded in the past, and the cover rate reduce badly. The deterioration of the environment that the desert land caused, is not merely endangering the Horqin sandy land, and is threatening the areas of west of the whole Northeastern plain. Based on the analysis of the size distributions, the present paper discusses the grain size parameters of four different land types in the Horqin sandy land. Quantitative analysis have been conducted on the possibilities of wind erosion of the different land types, concerning the recent climate records in the studied area. The paper also proves the potentials of wind erosion of the surface sediments of the different land types and morphologies, and the farmland is of the greatest potential providing dust for the regional dust-storms, and then naked land, sand due and grassland lower. The desertification degree of Horqin is higher, the farmland is the greatest, and then naked land, sand due, grassland. As a result, it is believed that there is not much differences in the possibilities of wind erosion among the 7 kinds of farming lands. There is remarkable difference in four land types on the grain size. The sand, fine sand and content of fine sand have changed regularly, when from changing into the cultivated land on the meadow, the content of sand reduces obviously, and fine sand increasing degree is comparatively remarkable very much. When the degrade grassland was protect to plant effectively, the surface cover resume again. The grain size become thinner than before on the surface of the resumed grassland, thus enhanced the resist possibility of wind erosion. Meanwhile, such soil nature as the water content of soil , organic matter ,etc. changed in various degree while the land type changed. Meadow degrade or cultivate for farmland, water content reduce obvious, soil organic matter drops seriously; cultivated land's surface particulate material lost serious in wind erosion, and then form the sandy wasteland during a long period. Through an analysis of climatic change of Horqin sandy land, found that the natural factor that influenced this area land use change mainly to be climatic change. Change , especially reduction of the rainfall and the increasing of strong wind days in near these decades, make the water content in the earth's surface reduce greatly . The drought earth's surface is prone to wind erosion under wind-force function. Farmland which cultivate about three years become sandy andcan't to plant, then abandon, for a long time, form the morphologies and land types which grasslands, sand due alternate with distribution in Horqin sandy land. From the change of temperature and raining, there is period that arid degree reduced in Horqin sandy land. While have periods that arid degree intensified, the former is available to plant and delay the process of desertification, but the latter is opposite. Base on the study, for next 10 years or more, there is increase trend of temperature and no obviously change of the precipitation, which will let to strengthen the drought grade. Some studies suggestion that there are trends of increased temperature and decreased precipitation in the semiarid region. So, just considering the natural driving factor, the climatic variation is propitious to the development of desertification in the North China. In the past 50 years, the population pressure on the Horqin region had been increased , which resulted in unreasonable economic activities to speedup the process of desertification. Although the increased rate of population had been dropping at recent years, the existing population pressure on the land exceed the environmental capacity, so that it would be in the developing tread of desertification in the Horqin Region for next decade if the human negative activity is going to persist impact the process of desertification will develop during next decades. But it is very encouragement that the desert land had been reversing during last decade in Horqin region, which proved that the desertification could be prevented and controlled if the human practice land use reasonably and make effort to combat desertification. It's the positive aspect of human driving factor to the process of desertification. Synthesized above analyze of the natural and human driving factors impact on the occur and development of sandy desertification, we believe that between those...