锡林郭勒河流域生态环境受损动态与预防决策系统研究

Steppe degradation is a major problem affecting environmental management and animal husbandry in Inner Mongolia, China because it can cause desertification and reduce steppe productivity. To assess the extent and severity of steppe degradation at the regional scale, we compiled the vegetation type maps in 1985 and 1999 for the Xilin River Basin, Inner Mongolia based on Landsat MSS, TM images and field survey. Then, based on the steppe degradation succession model, under the support of GIS, we constructed vegetation degradation maps for the Xilin River Basin. The total area of degraded steppe in this region was 7191.3 km2 in 1985 (67.19% of the entire basin), and increased to 7689.3 km2 (71.86% of the total basin) in 1999. We developed a steppe degradation index (SDI) aggregating the information both area and rank of steppe degradation to quantify the degree of degradation and its changes in space and time. The SDI map revealed that large-scale patterns in terms of different degrees of degradation. We calculated respectively the value of steppe degradation index in the whole basin, the upper, middle and lower reaches and lower mountain, hill, lava tableland and high plain. Using trend surface analysis, the contour map of steppe degradation index in the Xilin River Basin was constructed. In this map, several seriously degraded regions in the Xilin River Basin could be identified, which all were related to overgrazing. Then, the translation probability matrix from 1985 to 1999 of different grade of degraded steppe was calculated, with application of Markov process, the changing trend of steppe degradation in the Xilin River Basin was forecasted.Using Landsat TM CCT, selecting the middle reach of Xilin River Basin as study area, we established the model of steppe aboveground biomass estimation, and estimated the aboveground biomass of steppe in the study area in the middle July 2000. Based on giving the scope of aboveground biomass of two main types steppe vegetation undegraded and degraded, we assessed steppe degradation rank with the unit of pixel, and compiled steppe degradation distribution map of the middle reach of Xilin River Basin. Considering steppe ecosystem sustainability as final goal, determined different forage grass utility rate to the different degradation ranks, divided six grazing intensity ranks, calculated reasonable grazing intensity, area and grazing capacity. The result can provide decision-making support for the restoration of degraded steppe and the sustainable development of animal husbandry at the regional level. Controlling the head number of livestock and restricting people from moving to grassland areas that are ecologically vulnerable are of utmost importance for preventing further steppe degradation in this region. This study demonstrates the effectiveness of combining remote sensing and synoptic ecological indices in assessing and monitoring ecosystem degradation, and provides useful information for developing sustainable grazing/management practices in the Xilin River Basin.

本研究拟利用3S技术与地面调查相结合的方法，编制锡林郭勒河流域生态环境受损图，建立生态环境受损空间动态模型，对该流域近30年来生态环境受损时空动态变化规律进行研究，建立草原生态环境受损预防保护决策支持系统。其研究成果将会深化对于草原生态环境受损动态与机理的认识，为该流域草地资源可持续利用与生态环境保护提供依据与方法。