THE EFFECT OF LAND USE CHANG ON THE REGIONAL ENVIRONMENT IN THE YANGJUANGOU CATCHMENT IN THE LOESS PLATEAU OF CHINA
Fu Bojie Chen Liding Ma Keming (Research Center for Eco Environmental Sciences, Chinese Academy of Sciences, Beijing 100085)
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: forestgrasslandslope farmland, while the content of soil water are: forestgrasslandslope farmland.