干旱区生态环境知识资源中心

Farmland is a significant form of land use; it plays an important part in the food security and the stability of ecosystem environment. Fallow is a part of cultivated land, but it is somewhere no crops planting on for the consideration about the soil fertility protection. This paper had done some experiments to extract fallow land from the cultivated land by means of GIS and RS. The test area in this paper was Akesu area, which is located at the west part of Xinjiang Province. The data used in this paper is MODIS EVI, whose temporal resolution is 16 day and spatial resolution is 250m. The extracting of the fallow is based on the theory of density slicing, and the method can divided into the following steps. Firstly, the land use map of Akesu area was gained by visual interpretation. It's based on the TM images whose spatial resolution is 30m. Secondly, grid with spatial resolution of 250m was drawn In ArcGIS. Then the land use map and the grid were overlaid, and the percentage of each land use type in each grid was calculated. Thirdly, we pick out the pixels in which agriculture land account for more than 90% and then some analysis was made on the relation between the coverage of the agriculture land and the maximum EVI in the crop growing season. As a result, when the threshold of the maximum EVI was set as 0.25, fallow could be discriminated form the cultivated land. And it was validated by the result got from CBERS images which has higher spatial resolution, and it's indicated that the method had a good perform on the extracting. By analyzing the result, we can conclude that fallow land generally distributes far away from the river and in Akesu area, the Wei Gan River-Ku Che River delta oasis has the largest area of fallow land which mostly result from the soil salinization.