汉江流域景观格局变化对土壤侵蚀的影响

Influence of landscape pattern change on soil erosion in Han River Basin

在流域尺度上,景观格局变化是决定土壤侵蚀程度的重要因素。以汉江流域为研究区域,基于2000—2015年四期土地利用类型数据及环境气象数据,运用中国土壤流失方程和逐步回归法,探究景观格局变化对土壤侵蚀的影响。结果表明:(1)在2000—2015年间,汉江流域土壤侵蚀量下降,高值区分布在流域中部草地区,低值区分布在流域东西两侧的林地和耕地区。不同坡度下各等级土壤侵蚀量不同,侵蚀量最大值出现在10—30°的坡度范围内。(2)研究期间,汉江流域的景观破碎化程度加强,斑块形状趋于简单,各斑块自身连通性增强,景观类型空间分布均匀。(3)汉江流域土壤侵蚀量与斑块密度和平均邻接度指数呈正相关,与蔓延度指数和香农均匀度指数呈负相关,即景观破碎度越高、连通性越差,土壤越容易遭受侵蚀,反之则不易受到侵蚀;研究表明景观格局变化对土壤侵蚀有显著影响,结果可为流域尺度景观管理与水土保持研究提供参考。

Soil erosion is a serious environmental problem in the world, which is a complex process depending on a set of factors, such as topography of the river basin, rainfall, soil characteristics, and landscape pattern. The relationship between landscape pattern and ecological process is an important research project in landscape ecology. The impact of landscape pattern changes on soil erosion remains a major issue in ecosystem service. Therefore, research on soil erosion in Han River Basin is of great significance for ensuring the development of regional economic. The purpose of this study is to explore the impact of landscape pattern changes on soil erosion through Chinese soil loss equation and stepwise regression method, based on the land use data and environmental meteorological data from 2000 to 2015. The results show that:(1) from 2000 to 2015, the amount of soil erosion in Han River Basin presents downward trend. The high-value areas are distributed in the middle areas of the watershed, which is grass land. And the low-value areas are located in the east and west of the watershed, with the land type of forest and arable. In addition, slope is an important factor which affects the amount of soil erosion. As the slope increases, soil erosion shows an inverted U-shaped trend of increasing first and then decreasing. The amount of soil erosion is different for each grade under different slopes, and the maximum value appears in the slope range of 10—30 °.(2) At landscape level, the degree of landscape fragmentation in Han River Basin increased during the study period, the shape of patches became simpler, the connectivity of each patch enhanced, and the spatial distribution of landscape types was distributed evenly. At the class level, the area of forest land and cultivated land were decreased, and the other land types were increased. The forest land is the dominant land type in Han River Basin, and the patch shape of forest land is relatively simple and stable. The landscape patch shapes of grassland and arable land are more complex than others, with landscape is more shattered. However, the overall landscape distribution in the region is even and stable.(3) The soil erosion in Han River Basin was positively correlated with patch density and average contiguity index, and negatively correlation with contagion index and Shannon′s evenness index. The results show that the higher landscape fragmentation and the worse connectivity between patches, the easier erosion of soil. On the contrary, the higher landscape connectivity between patches and the richer of landscape diversity, the more difficult erosion of soil. Furthermore, rainfall changes have an important role in soil erosion, and rainfall erosivity is not only consistent with the soil erosion in spatial distribution, but also consistent with temporal trend of that. In conclusion, this study indicates that the change of landscape pattern has a significant impact on soil erosion, and the results can provide a reference for watershed-scale landscape management and soil-water conservation.