基于“源-汇”生态过程的景观格局识别方法——景观空间负荷对比指数

Location-weighted landscape contrast index: a scale independent approach for landscape pattern evaluation based on “Source-Sink” ecological processes

正确理解景观格局与生态过程的关系是进一步深化景观生态学研究的关键 ,但是由于景观格局和生态过程涉及到不同的研究尺度 ,并且随着尺度的变化而变化 ,加上面状生态过程监测数据无法直接获得 ,导致很难定量描述景观格局与生态过程之间的关系。本文以非点源污染作为研究的典型生态过程 ,通过分析不同景观类型及其空间分布格局在非点源污染形成过程中的地位和作用 ,借用洛伦兹曲线的理论 ,从距离、相对高度和坡度三个方面建立了不受尺度限制的景观格局评价模型——景观空间负荷对比指数。该指数可以较好地将具有面状特性的景观格局与点状监测数据有机地结合在一起 ,使定量研究流域景观格局与生态过程的关系成为可能。该评价模型的特点有以下几个 :1不受空间尺度的限制 ,具有跨尺度的功能 ;2适宜于环境背景 (降雨和土壤等 )相似的地区 ;3景观空间负荷对比指数具有相对比较意义 ,其值越大 ,表示该类景观空间格局对流域出口监测点的贡献越大 ,反之越小 ;4景观空间负荷对比指数不能用来预测流域出口监测点非点源污染或水土流失的值 ,但是可以通过比较计算不同流域景观空间负荷对比指数 ,来判断流域发生养分 (水土 )

Understanding the relationship between landscape pattern and ecological processes is critical for any in depth research in landscape ecology. However, it is difficult to quantify this relationship given the fact that landscape pattern and processes are scale dependent, along with the difficulty in acquiring ecological processes monitoring data. In this paper, we analyze the roles and functions of different landscape types and their spatial patterns under a framework of non point source pollution. We further propose a new landscape metric index, namely, location weighted landscape contrast index (LCI). Under a framework of the Lorenz Theory, this index can be used to evaluate the effect of landscape pattern upon ecological processes as related to distance, relative elevation, and slope degree. It can be used to quantify landscape spatial pattern by using point based ecological measurements. It has four major characteristics. First, the index is scale independent. Second, the index is particularly suitable for homogeneous landscape in terms of rainfall and soil. Third, this index can be used to characterize the relative contribution of landscape spatial pattern to a specific monitoring point. The bigger the index is, the larger the contribution will be. Last, it should be noted that the absolute value of LCI cannot be used to predict the amount of non point source pollutants or soil erosion. However, the value of LCI can be used to evaluate the potential risk of nutrient (including water and soil) loss by comparing the LCI indexes for different catchments.