东北地区土地利用转换及其生态效应分析

Conversion of land use types and ecological effect in Northeast China

基于1990、1995、2000年3期Landsat TM影像数据,在遥感与GIS支持下分析了东北地区1990～2000年土地利用转换特征与格局,以及耕地内部水田与旱地转换态势和成因.研究表明:农业土地利用内部及其非农化转换趋势明显.耕地、草地年均减少4.99×104和1.40×104hm2,水域、林地、建设用地年均增加2.39×104、1.93×104和1.44×104 hm2;不同时期的土地利用类型转换差异较大,以1990～1995年间变化为主,耕地、林地和建设用地变化量分别占总变化量的93.5%、85.8%和75.8%.耕地内部水田和旱地的转换频繁,主要是政策调控和市场调节综合作用下实施农田改造工程的结果.退耕还林草与林草地开垦的逆向发展,以及水田与旱地频繁的转换过程,已带来土地退化、水资源浪费和环境恶化等严重负面效应.

The objective of this study is to ascertain the temporal and spatial differentiation of land use conversion in Northeast China, determine their causes, and analyze their environmental impacts. Also elucidated is the role of institutional constraints in these changes during agrarian restructuring in the 1990s when market was hybridized with the planned economy. Six land use types were mapped from TM images recorded in 1990, 1995 and 2000. Overlay of these maps in ArcInfo revealed that farmland and grassland decreased by 4.99×10^4 and 1.40 × 10^4 hm^2, respectively, while water, built-up areas, and woodland increased by 2.39 ×10^4, 1.93 ×10^4 and 1.44 × 10^4 hm^2, respectively. Over three-quarters of these changes occurred from 1990 to 1995. Farmland changed mainly to woodland, water and built-up areas while woodland and grassland were converted chiefly to farmland. Spatially, the change from woodland to farmland adjoined the margin of natural forests while the change in the opposite direction was restricted to the agropastoral west. Paradoxically, reclamation of grassland as farmland also took place here. Besides, fallow land here was changed to grassland and to farmland in the Three River Plain. Driven by market demand and government regulation, rice was cultivated more widely with the creation of 338803 hm^2 paddy out of non-irrigated field. However, lack of water forced 40230 hm^2 paddy field to degenerate into dry land. These chaotic and conflicting changes were caused largely by lack of stability and consistency in land use policy. While climate warming made some of these changes possible, they have caused such environmental problems as land degradation, increased flooding and mini climate change.