Study on the conversion between farmland and pastoral land and its affecting factors in the western of the Songnen plain

In recent years, agriculture and animal husbandry alternate each other frequently in Western of Songnen plain. To understand the alternation between agriculture land and grass land and the factors which cause those changes could provide scientific basis for the protection of regional environment. Based on the technology of RS and GIS and meteorological data during 1959~2008 and land use data from 1956 to 2008. This paper analyzed the changes from the number of agricultural and pastoral land, spatial variation, gravity center and density during 1956 - 2008. And analysis the factors which cause those changes deeply. The results showed that from 1956 to 2008, the arable land in this area increased by 4.61 × 105 hm2, while pastoral land decreased by 7.65 × 10⁵ hm2. The frequency of alteration between arable and pastoral lands increased, their gravity center inclined to the west and opposite in latitudinal direction. Density of about 10% of grassland is widely distributed, and arable land of 20% - 30% is mainly in the eastern. Interaction between agricultural and pastoral land is caused by both climatic and human factors. Climatic factors are the main driving force, but human activity also played a negligible role.