Dynamic Changes In Land Use/Land Cover In Xinjin County

Land is the necessary foundation on which we human beings live and prosper. It provides the basic conditions for the development of human society because the materials used in our daily life and production are all obtained from land resources. No social and economic activities can take place without the support of land. With the social, economic and cultural development, however, we face a growing need for land. In this context, dynamic change in land use/land cover becomes an important research topic in the field of earth surface science and the frontier of global change study.With a combination of supervised and unsupervised classification methods, a land use classification study was conducted based on the remote-sensing images of the whole county of Xinjin in Chengdu obtained in 1992, 2006, and 2013. GIS technique and the social and economic data of the region were also used.In view of the current situation, the land of the study area was classified into five classes according to land use: farmland, building land, forest land, water area, and unused land. In terms of area, the building land area has grown at an extraordinary rate of 619.35%, while other types of land have shrunk to different degrees. The loss of unused land was the largest, followed by the forest land, farmland and water area turn. Moreover, the building land showed the highest rate of dynamic change of 16.49%, while other types of land showed relatively smaller rates of dynamic change. In terms of spatial distribution, the building land has expanded in space; the forest land, mostly in the south and east of the region, showed little change in distribution; the unused land, primarily flood plains, was distributed along rivers; the farmland was mainly distributed in the west and north; and the location of water area nearly remained unchanged. Through analyzing the transfer matrix of each type of land, the area loss of each land type was worked out. A total of 22.31km2 of farmland was lost, which was mainly transformed into forest land. 8.06km2 of unused land was lost, which was turned into water area and forest land. And the lost forest land of 76.78km2 was largely used as farmland. The increased building land of 115.57km2 mostly came from the forest land and farmland. 8.43km2 of lost water area was turned into unused land and forest land.The factor analysis indicated that economic and social factors were the main factors affecting the land-use change in the study area. Natural factors, including topography and climate, also influenced the distribution of different types of land but were the secondary factors. In the study periods, only the building land showed an increase in area among all types of land, possibly due to the growing need for residential and industrial lands with the growth in population and economy. Among different human factors, population and economic factors were the primary factor influencing the land-use change, followed by the factors of policy and transportation development.