北方农牧交错带土地利用现状对生态环境变化的影响——以内蒙古多伦县为例

The effects of land use change on the eco-environmental evolution of farming-pastoral region in Northern China:With an emphasis on Duolun County in Inner Mongolia

主要研究内蒙古典型地区多伦县土地利用现状对生态环境变化的影响 ,主要包括土地利用方式、程度和效率等。研究表明 :在近一个时期 ,该地区人口在不断增长 ,土地利用结构在不断变化 ,如自 1 983年到1 999年期间 ,其耕地由原来的 1 8.83 %上升到 3 2 .0 9% ,增长了 1 3 .2 6 % ;而草地由原来的 5 1 .79%降到3 6 .1 3 % ,消减了 1 5 .6 6 % ;林业用地由原来的 4.1 6 %降到 2 .87% ,下降了 1 .2 9% ,这种结构性的变化 ,致使植被、林地在减少 ,草原在退化。如 2 0世纪 5 0年代最高产草量 (鲜重 )可达 75 0 0 kg/hm2 ,到 1 983年下降到3 0 0 0 kg/hm2 ,而现在只有 1 5 0 0 kg/hm2 ;而这种草场退化结果又导致农田沙化 ,肥力下降 ,如农田比草地土壤有机质低 5 0 %左右 ,而 N、P、Zn等其他元素在 3 0 %左右 ;草地与沙化草地相比 ,有机质、N、P、Zn的含量普遍低 2 0 %～ 5 0 %。为此 ,在本区必须进行土地分类和土地潜力分类为主的土地利用评价 ,以满足土地得以合理利用和自然保护等现代土地利用规划的需要 。

The north farming-pastoral region is the most sensitive eco-environmental area in China. Land use changes play important roles in eco-environmental evolution in this area. Understanding how land use changes influence the eco-environmental evolution will help China to improve the eco-environmental quality of this area and it's neighboring areas. In this paper we use Duolun County as an example to investigate how land use changed in the past 50 years, and how these changes affected the quality of eco-environmental system in this area. Duolun County is a typical region in the north farming-pastoral region, it locates in the south of the Inner Mongolia, and about 400 km from north of Beijing. Duolun County occupies 3873 km 2 land, the annual average temperature is 1.5°C, and the annual average rainfall is about 385.5mm. Our study suggests that the land use has greatly changed since 1950s, especially after 1980 in Duolun County. From the beginning of 1980s to present, the arable land area increased from 18.8% to 32.1% of the total land area, grassland area decreased from 51.8% to 36.1%, forest area decreased from 4.2% to 2.2%. The land use changes, the long term low input and overuse of arable land and grassland resulted in the degradation of soils and deterioration of eco-environment. Data from 60 soil samples around Duolun county show that most of the arable land and grassland are deficient in N, P, Zn, Mn, B, and Mo, low input and overuse of soil resources resulted in desertification of large area of cropland and grassland, and reduced soil organic matter and available N, P, Zn content by 20%～50%. As a result of soil degradation, the crop and grass yields are very low. For example, the maximum grass yield (fresh weight) was 7500, 3000 and 1500 kg/hm 2 in 1950s, 1983 and present respectively. The low yields require more grassland to be cultivated to meet the growing requirement of food and feedstuff, and further deteriorate the eco-environment. To stop the deterioration of the eco-environment, and improve the quality of the eco-system, land potentials evaluation, and land use classifying are urgently needed.