Abstract:

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.

Key words: landslides, macropores, root systems, organic matter, particle size distribution