黄土丘陵区景观格局对水土流失过程的影响——景观水平与多尺度比较

以黄土丘陵沟壑区河口-龙门区间内42个水文站控制流域土地利用和径流泥沙数据为基础,借助GIS和RUSLE,运用景观格局指数分析法,从景观水平和多尺度上探讨景观格局对流域水土流失过程的影响。结果表明:河龙区间流域景观格局和水土流失过程特征存在明显空间分异和相对差异。在斑块类型水平上草地的连结度(COHESION3)和分维数变异度(FRAC_CV3)、耕地和居民建设用地的丛生度(CLUMPY1、CLUMPY5)、居民建设用地边缘密度(ED5)是影响流域水土流失过程的重要指标,其中草地连结度对流域水土流失过程变异的解释度最高。在景观水平上景观连结度(COHESION)、平均斑块面积(AREA_MN)、景观聚集度(AI)、景观丰富度(PR)是影响水土流失过程的主要因子,其中景观聚集度(AI)对流域水土流失过程变异的解释程度最高。斑块类型水平景观格局对水土流失过程空间变异的解释能力要高于景观水平。景观格局具有明显的嵌套特性并强烈影响着流域水土流失过程,在嵌套水平上草地连结度(COHESION3)和耕地丛生度(CLUMPY1)是控制流域侵蚀产沙的主要格局因子,草地分维数变异程度(FRAC_CV3)可以抑制流域泥沙输移过程。景观格局对水土流失过程的影响机制和景观指数与反应变量间的统计学关系随尺度不同而异。

Effects of landscape patterns on soil and water loss in the hilly area of loess plateau in China: landscape-level and comparison at multiscale

Soil erosion in Hekou-Longmen section of the middle reaches of Yellow river in the loess hilly and gully region of the Loess Plateau in China is serious. In this study, the watersheds from Hekou to Longmen (Helong section) in awhere 42 hydrological stations located were selceted to investigate the relationship between landscape pattern and soil and water loss by using Geographic Information System (GIS) and Revised Universal Soil Loss Equation (RUSLE). Specially, the landscape pattern index analysis, canonical correspondence analysis and path analysis were used to analyze the effects of landscape pattern on soil and water loss in different scales. The results showed that the spatial variation and relative differences of landscape pattern versus soil erosion/sediment delivery processes in the watersheds changed significantly with scales. At patch-class level, the cohesion (CONHESION3) and the coefficient of variation of fractal dimension index (FRAC_CV3) of grassland, the chumpy of cropland (CLUMPY1), the chumpy of residential construction land (CLUMPY5) and the edge density of residential land (ED5) were the main landscape pattern indices t controlling the variation of soil and water loss processes. Furthermore, the cohesion of grassland was closely related to soil and water loss processes. At landscape level, the cohesion (COHESION), mean patch area (AREA_MN), aggregation index (AI) and patch richness of landscape (PR) were the main pattern indices effectively affecting the variation of soil and water loss processes of a watershed. Landscpe metrics on patch-class level had more indicative ability than that on landscape-level. With comprehensive analysis of the impacts of land use patterns on the soil and water loss processes at the class-level and landscape-level, we found that land-use patterns show signifcant "landscape nesting" characteristics, in influencing the soil and water loss. At the "nested landscape" level, the cohesion of grassland (the path coefficient is -0.867) and the chumpy of cropland (the path coefficient is -0.367) were the main landscape pattern factors dominating watershed sediment yield, and the coefficient of variation of fractal dimension index (FRAC_CV3) (the path coefficient -0.49)could contribute positively to suppression of sediment delivery. Resluts of this study indicated that the landscape pattern has significantly influences on watershed soil erosion and sediment delivery, however, the statistical relationship between landscape indices and response variables of soil and water loss varies with landscape scale. Landscape is a mixture of natural and human-managed patches of different sizes and shapes, and the multiple-level mosaic structure of landscape is one of the important factors affecting the relationship between landscape pattern and ecological process. Selecting suitable spatial and temporal scales and analytical perspectives may improve our understanding of the interactions between pattern and process in the landscape.