基于土地利用变化的农牧交错带典型流域生态风险评价——以洋河为例

为揭示土地利用变化对农牧交错带典型流域生态风险的影响,在Arc GIS技术支持下,以洋河流域1990、1995、2000和2008年遥感数据和土地利用数据为基础,定量分析洋河流域1990—2008年的土地利用动态变化特征;根据景观生态学理论,将研究区划分为525个生态风险评价单元,从土地利用变化和景观结构角度构建景观生态风险评价模型,评价洋河流域生态风险的时空变化特征。结果表明:耕地和草地面积占研究区总面积的67%以上;1990—2008年,洋河流域总体景观生态风险值(ERI)由0.197 3上升到0.238 4。低风险区(ERI≤0.17)面积减少3.53%,高风险区(ERI0.68)面积减少0.43%,较低(0.17ERI≤0.26)、中等(0.26ERI≤0.42)和较高(0.42ERI≤0.68)风险区面积均有增加,整体生态风险增加;洋河流域5种风险等级分布较集中,具体表现为洋河支流及其一级支流两侧地区生态风险相对较大(ERI0.26),而离河道越远的区域生态风险值越小(ERI≤0.26)。

Landscape Ecological Risk Assessment of Farming-Pastoral Ecozone Based on Land Use Change -A Case Study of the YangheWatershed,China

To reveal the impact of land use change on ecological risk, dynamic changes of land uses in the Yanghe Watershed which is a typical farming-pastoral ecozone in north China were analyzed with ArcGIS technologies based on remote sensing and land use data during 1990- 2008. The Yanghe Watershed was divided into 525 ecological risk assessment units based on the theory of landscape ecology. A temporal and spatial model of ecological risk assessment in the study area was established based on land use changes and landscape structures. Results showed that the areas of farmland and grassland accounted for more than 67% of total area of the watershed. Generally, landscape ecological risk indicated by ecological assessment index (ERI) for the whole watershed increased from 0.1973 to 0.2384 during 1990 to 2008. The area for the lowest (ERI≤0.17) and the highest (ERI >0.68) ecological risks reduced by 3.53% and 0.43%, respectively, while the areas of the lower (0.17< ERI≤0.26), the medium (0.26< ERI≤0.42)and the higher (0.42< ERI≤0.68) ecological risks increased. Distributions of five ecological risk grades were relatively concentrated. The sites with the relative high risk grade (ERI >0.26) were located along the main streams and sub- streams of the Yanghe Watershed, while those with the lower risk (ERI≤0.26) were further away from these streams.