马卡山不同植被群落下非饱和带大孔隙流路径示踪试验

为辨识在天然降雨条件下，植被发育斜坡非饱和带中具有优先流效应的大孔隙流路径，不包括死端大孔隙，分析两种植被群落下非饱和带大孔隙流路径分布模式差异及植被根系、有机质含量、土壤颗粒尺寸分布对大孔隙流路径分布模式的影响；选择亚甲基蓝作为染色示踪剂，结合降雨入渗模拟试验，在马卡山草本植被群落斜坡和木本植被群落斜坡开展染色示踪渗透试验。基于垂直开挖剖面采用图像处理技术获得大孔隙流路径分布模式图像。采用非参数检验分析大孔隙流路径差异。采用差方分析、回归分析法分析根系质量分数、有机质含量和颗粒尺寸分布对大孔隙流路径分布模式的影响。结果显示：木本植被群落斜坡大孔隙流路径分布模式更复杂，尺度更大；根系显著影响大孔隙流路径数量、尺度和分布特征，尤其是垂直向下和顺坡向下的根系，当根系尺寸增大时，其对大孔隙流路径影响更显著；有机质有利于团聚体间大孔隙的形成；黏粒、粉粒和砂粒对大孔隙流路径形成没有积极功效，但砾粒有利于大孔隙路径形成，尤其是在表土层；根-土界面和砾-土界面也是重要的大孔隙流路径。研究表明，可以通过根系分布形态、规模，有机质含量和砾粒含量综合评价植被发育斜坡大孔隙流路径分布模式。

A Dye Tracer Experiment to Study Macropore Flow Paths in Unsaturated Zone Under Different Vegetation Communities in Maka Mountain,China

The objectives of this study is to distinguish the macropore flow paths that have preferential flow effect in natural rainfall conditions in unsaturated zone of well vegetated slopes, not including dead-end macropores, and to analyse the differences of distribution patterns of macropore flow paths between two different vegetation communities and to investigate the influence of root systems, organic matter, particle size distribution on the distribution patterns of macropore flow paths. Methylene blue was chosen as the dye tracer. Dye tracer infiltration experiment and rainfall infiltration simulation experiments were performed together in herbaceous community slopes and in woody plant community slopes in Maka Mountain, China. The distribution patterns of macropore flow paths were obtained based on vertical sections excavated through each experimental plot by image processing technology. The differences of macropore flow paths were analysed using nonparametric test. The analysis of variance and regression analysis methods were used to analyse the effects of the mass density of root, the organic matter content and particle size distribution on the distribution patterns of macropore flow paths. Results show that: 1)the distribution patterns of macropore flow paths in woody plant community slopes were more complex and larger than in herbaceous community slopes;2)root systems had significant effects on the quantity, the scale and the distribution patterns of macropore flow paths, especially, those which had developed vertically or in a downslope direction,as the root size increased, the effects were more significant;3)the organic matter was favorable for the formation of the inter-aggregate pore;4)Clay, silt and sand didn’t produce positive effects on the evolution of macropore flow paths and gravel was favorable for the formation of macropore flow paths, especially in the topsoils; 5)root-soil interface and gravel-soil interface were important macropore flow paths. Our results indicate that the distribution patterns of macropore flow paths could be synthetically evaluated through the root systems morphology and scale, the organic matter content, the gravel content in well vegetated slopes. Further work is needed to estimate the risk of macropore flow paths to the stability of well vegetated slopes.