黄土丘陵区小流域土地利用变化对生态环境的影响——以延安市羊圈沟流域为例

THE EFFECT OF LAND USE CHANG ON THE REGIONAL ENVIRONMENT IN THE YANGJUANGOU CATCHMENT IN THE LOESS PLATEAU OF CHINA

选择黄土丘陵沟壑区的羊圈沟流域，应用地理信息系统和野外采样分析，从小流域、坡面和单一土地利用类型三个尺度层次研究土地利用变化对流域土壤侵蚀、土壤养分和土壤水分的影响。结果发现：１９９６年比１９８４年该流域坡耕地减少了４３％，林地增加了４２％，草地增加了５％，土壤侵蚀量减少了２４％。坡耕地—草地—林地土地利用结构具有较好的土壤养分保持能力，且前期土壤含水量低，是黄土丘陵区梁峁坡地上较好的土地利用结构类型。该流域土壤养分含量林地＞草地＞坡耕地。

Land use changes may influence a variety of natural phenomena and ecological processes, including soil conditions, water runoff, soil erosion and biodiversity. Irrational land use is one of the main reasons for the soil erosion and nutrient lose in the loess hilly area. The Yangjuangou catchment in the Loess Plateau of China, with typical loess hill and gully topography, was selected as the study area. The study focus on the affects of land use changes on soil erosion, the distribution of soil nutrient and soil moisture from catchment, and land use type at three spatial scales. Aerial photography interpretation and field survey mapping were used to produce land use maps in 1984 and 1996. GIS was used for data storage, analysis and display from a comparison of land use areal changes in 1984 and 1996. It was determined that the area of forest and grassland increased 42% and 5% respectively and slope farmland decreased 43%. Land use changes result in a decrease of soil erosion by 24%. Three types of typical land use structure during 15 years in the loess hill slope were selected in order to study the effect of land use structure on the distribution of soil nutrients and soil moisture. From the bottom to top of hills, the patterns of land use types are: grassland slope farmland forest, slope farmland grassland forest and slope farmland forest grassland. By measuring the contents of the total N, total P, available N, available P, organic matter of soil and soil moisture in 0 cm￣70 cm depth, the results show that the land use structure type of slope farmland grassland forest has high contents of soil nutrients and low antecedent soil moisture. This indicates that this land use structure has a better capacity for retaining soil nutrient and a high efficiency for soil conservation. The analysis of soil nutrient and soil moisture in different land use types showed that the content of soil nutrient are: forest>grassland>slope farmland, while the content of soil water are: forest<grassland<slope farmland.