Land Use/cover Change And Environmental Responses In Zhifanggou Catchment In The Past Century

Land use/cover change is one of the main driving forces of environmental change. Understanding interactions between land use/cover change and environmental responses have important implications for ecological restoration. This trans-disciplinary study assesses the environmental responses to the land use/cover change in the last century in Zhifanggou Catchment (ZFGC) based on the theories and methods from land resources science, landscape ecology and RS and GIS techniques. The main results are as follows:1. The analysis of long-term land use changes and environmental responses shows that vegetation has faced great changes from natural restoration to complete destruction, from slow rehabilitation to rapid recovery in ZFGC. With this change, the environment began to deteriorate after 1938, and reached to the lowest point in 1958. After that the environment started to recover slowly with re-vegetation on small patches during the 1958 and 1981. From 1981 to 2000, the environment has been greatly improved due to the rapid recovery of vegetation. The analysis of driving forces of land use change showed that the farmland expansion due to population increase was the main reason for the deterioration of environment, yet the investment in technology adoption and improvement in agricultural production reduced the need for farmland thus increased the supply of land for environment purposes.2. During the last hundred years, the land use in ZFGC has changed from the pure agricultural production stage, during which land was regarded as one of production resources to produce the maximum profit, to a new stage that requires the improvement of environment and sustainability of agricultural production. The environmental responses to positive human interventions showed that if the investment in technology adoption and improvement in agricultural production can be intensified and proper land use plan be made, (1) the objective to initially improve the environment in 8 years is possible, and (2) in 18 to 20 years, the environment can be essentially improved and agricultural production be sustainable.3. Based on the established model for land use change, the author proposed the threshold values for land use adjustment with the increase of land productivity: (1) when the index of land use change equals or is bigger than 1, then no farmland can be changed to environmental uses, and more attention should be paid to the protection of current farmland; (2) when it equals or bigger than 0.5 but less than 1, there are driving forces to convert the land for environment purposes to farmland, thus needs close attention to prevent the supply of more farmland for environmental purposes; (3)when it is less than 0.5, the supply of farmland can meet the local need for food, thus it is possible to convert some low-quality farmland to environmental uses.(4) Based on the integration of historical files, social and economic investigations, fieldsurveys and remote sensing and GIS techniques, the author systematically studied the different aspects of land use change, including land use history, scales, social and economic driving forces and environmental responses. During this trans-disciplinary study, the author proposed or established a set of methods and evaluation indexes, including the methods of establishment of spatial database of land use change, the models of land use change and environmental evaluation, and up-scaling method of data, optimization of land use based on farms' participation. Since most of these method are based on GIS technique and land use pattern, they can be used in land/cover change on catchment scale but also on regional scale.