Characteristics Of Preferential Flow In Two Typical Types Of Soil In Beijing

Soil preferential flow is an important way of soil water infiltration and plays an important guiding role in the water use of agricultural land and plant species selection.In this study,the field brilliant blue dyeing and tracing test was used to compare two typical types of common soil in Beijing mountainous and plain areas:leached cinnamon soil and fluvo-aquic soil with 35mm heavy rainfall.The morphological characteristics of the dyeing profiles were obtained and the development degree of preferential flow was analyzed.At the same time,CT tomography was used to quantify the distribution of macropores in undisturbed soil columns of two types of soil.The distribution of soil macropores was comprehensively analyzed and the formation mechanism of preferential flow in the study area was studied,with a view to further understanding of the preferential flow patterns in mountainous and plain areas of Beijing and provide guidance for the deployment of agricultural and forestry production and environmental ecological work.The main conclusions of this study are as follows:(1)The characteristics of preferential flow development of leached cinnamon soil and fluvo-aquic soil were the same in certain aspects.The relationship between the dyeing ratio of the two types of soil and the soil depth was negatively correlated.The regression relationship between the dyeing ratio and the soil depth were 0.988 and 0.975 respectively in leached cinnamon soil and fluvo-aquic soil.Leached cinnamon soil and fluvo-aquic soil had the main preferential path concentration distribution area,and lateral flow was found in both types of soil.(2)There were great differences in the dyeing morphological characteristics of the two types of soil.The dyeing ratio,stromal flow depth,preferential flow ratio and length index of leached cinnamon soil were larger than that of fluvo-aquic soil.Preferential flow development of leached cinnamon soil was better than fluvo-aquic soil and the morphological change of leached cinnamon soil was more intense than that of fluvo-aquic soil.It occurred in the same soil type that dyeing morphological characteristics were different because of differences in vegetation cover,altitude,et al.(3)The development of macropores in leached cinnamon soil was higher than that of fluvo-aquic soil.Although the macropores volume of leached cinnamon soil was lower than that of fluvo-aquic soil,the total volume of soil macropores and the macroporosity were higher than that of fluvo-aquic soil.The macroporosity of the two types of soil did not exceed 5%,leached cinnamon soil was 2.83%and fluvo-aquic soi was 1.965%;in the soil depth of 0?3300mm,the maximum diameter of the two types of soil macropores appeared in the soil depth range of 200-300 mm.(4)The factors affecting the dyeing ratio were soi1 texture,soil organic matter and root length density of l?3mm in diameter.The factors affecting length index were soil bulk density,soil texture and root length density of l?3mm.The correlation between the length index of the two types of soil and the physical and chemical properties of the soil was quite different.The length index in leached cinnamon soil were significantly correlated with soil bulk density,the content of sand,powder and clay in the soil texture,and the root length density of l?3mm in diameter while in fluvo-aquic soil,it was significantly correlated with root length density of 1?3 mm in diameter.