Land Potential and Carrying Capacity Evaluation after Conversion of Farm Land to Forest in Gezhen'er Watershed

摘要

The land's irrational utilization was the main cause of vicious cycle among population, resource and environment in Gezhen'er watershed. To improve the quality of the environment, the conversion of cultivated land to forest was necessary. Using the example for Gezhen'er watershed, the system of land potential evaluation and indexes was studied. Based on the current status of land utilization, the watershed was divided into 177 plots, and attribute database of these plots was built in GIS. Then by using expert system, the potential of each plot was evaluated. The results showed that the land area of classified as grade Ⅰ was 78.2 ha,accounting for 8.16%of the total area, the area under grade Ⅱ was 107.33 ha or 11.21% of the total area, the area under grade Ⅲ was 179 ha or 18.68% of the total area, the area under grade Ⅳ was 576.8 ha or 60.20% of the total area, and the area under grade Ⅴ was 9.2 ha or 0.96% of the total area. Grades Ⅲ and Ⅴ land was the major, and the quality of this land was low, but the potential to develop forest and stockbreeding was great, and this land should be fully utilized when the structure of land utilization was adjusted. A calculation of the carrying capacity of land showed that the land with a slope ＞ 15° should be converted to forest. The maximum of land carrying capacity was 2 802 person, which exceeded the predicted population. After converting some cultivated land to forest, the food supplies were secure, and the converted land can be stable.