Assessment On The Rationality Of Land Use Structure In Gansu Province Based On Improved TOPSIS Method

Based on changing data of land use and charts correlative to land use in Gansu province from 1997 to 2004, the land use structure of total province and fourteen cities in Gansu province were analyzed with imporved TOPSIS method. The results showed as following:1) During 1999 to 2007 the rationalities of land use structure are totally high and are all beyond 80%,the rationality of land use structure experienced a fluctuated tendency and that could be obviously divided into three phases, the land use structure rationality showed an increase in 1997～1999 first, then it had a steady decline in 2000～2002 and was growing rational in 2003～2007 finally.2) The different change of land use types had different effects on the rationality of land use structure; land use types which had a negative correlation with the land use structure rationality were garden plot, woodland, residential and industrial land, traffic land and unused land, of them unused land had the most negative correlation with the land use structure rationality; on the other hand, land use types which had a positive correlation with the land use structure rationality included cultivated land, grassland and water, of them grassland had the most positive correlation with the land use structure rationality.3)The annual change of land-use structure rationality of each city is obviously different from each other. Land-use structure rationality of Jinchang and Zhangye city were showed a progressively increase,and the change of Land-use structure rationality was more significant in Jinchang city. Land-use structure rationality of many cities,such as Tianshui city, Wuwei city, Dingxi city, Longnan city, Pingliang city, Qingyang city, Gannan canton, were showed a positive growth biggest. Among them, the change of Gannan canton was the biggest ,while the change was the smallest in Qingyang City.The rationality of land use structure in four cities experienced a fluctuated tendency,they are Lanzhou city, Jiayuguan city, Baiyin city and Jiuquan city. The land use structure rationality changed obviously in Jiayuguan city.4)The correlation degree between land-use structure rationality and land-use types varied significantly with the city. The land-use structure rationalityof many cities, include Jinchang city, Zhangye city, Tianshui city, Wuwei city, Dingxi city, Pingliang city, Gannan canton,were most related to each land use type, and the vast majority were extremely significant correlation. In Lanzhou city and Baiyin city, unused land had the most significant correlation with the land use structure rationality. The land use structure rationality of Jiayuguan City had the a positive correlation with water. The change of cultivated land have a big effect on land use structure rationality in Linxia canton.Land use structure rationality were less related to the land use types in Jiuquan and Qingyang city.5)The arid and semi-arid eco-environmental background of Gansu province determine that developing unused land and conserving grassland in progressing the rationality of land use structure. Though the correlation degree between land-use structure rationality and land-use types varied significantly with the city. The measures, such as rational exploitation of unused land,controling rapid growth of traffic land, residential and industrial land, Strict protection of cultivated land and water , Adjustment of proportion relation between woodland and grassland,could still be the feasible measures for promoting land use structure rationality.6)It had great advantages to assess land use structure rationality by imporved TOPSIS method, but the choice of evaluation indicators in this article is land-use types,so that it has a problem of uncertainty discrimination when you define the character of indicators (Cost-Type, Benefit-Type).Therefore, we should think about choosing from other aspects of the evaluation factors in the future, to ensure that we can define the positive ideal solution and negative ideal solution directly. It should be amended in terms of comprehensive evaluation factors. on one hand, to improve the the rationality of land use structure assessment system,on the other hand,to ensure accurate results and the method should be perfected so that it can be widely used for land use structure assessment.