关键词: 土地利用结构, 水土流失, 层次分析法, 快速评估, 安塞纸坊沟

Abstract: The variation of land use structures is of significance to soil loss as well as ecological protection. Therefore, dynamic assessment of soil erosion and identification of the effect of human activities could be carried out by monitoring the land use change. Based on the analysis of characteristics of land use change and soil loss, this paper presents an approach for soil loss assessment in terms of land use structure change. The analytic hierarchy process is introduced to identify the impacts of land use on soil loss in terms of the hierarchical structure of regional landuse associated with different scales or resolutions, and weights at different levels could be determined with the pairwise comparison matrix. As a result, a characteristic index for land use structure is proposed to reflect the comprehensive impacts of various types of land use, which is defined as the sum of products between the weight assigned to each type of land use and its corresponding area percentage over the total for the concerned region. Moreover, a new dynamic assessment method for regional soil erosion is proposed based on the analogy of the rapid biological assessment method advanced for water quality in recent years. With a series of processes of selection of reference sites, classification of reference groups, determination of environmental indexes, identification of the matching groups for the concerned sites, and the comparison of the observed and expected results through an O/E ratio, the trend of the soil loss in an assessment area could be predicted very rapidly. A case study of the Zhifanggou Watershed in Ansai, Shaanxi Province was preformed and the systematic comparison of landuse characteristics from 1938 to 1999 was revealed. The characteristics from the assessment method are conformed to the major historical development processes in the study area and thus show flexibility for evaluation of regional soil erosion and ecological status. At the same time, the method retains most advantages in rapid ecological assessment method and pays more attention to dynamic variations rather than absolute status for regional soil erosion. It could also mitigate the limitations to regions and scales as encountered in other traditional methods, and is helpful to enhancing the assessment process for regional soil erosion and ecological quality in a dynamic manner. For large scale assessment, the presented method could be more flexible in data re use, and could save much time and expenses.

Key words: land-use structure, soil erosion, analytic hierarchy process, rapid assessment, Zhifanggou watershed