Characteristics of preferential flow paths and their effects on soil properties

Preferential flow plays an important role in solute transport in soils and it indirectly affects the quality of groundwater. The objectives of this study were to investigate the vertical distribution characteristics of preferential flow paths under different-aged forest types and to determine the influence of preferential flow on soil properties and soil metal content. Dye tracer experiments were conducted at six forest sites at three ages. Results show a >50% dye cover at a soil depth of 10 cm in all sites. Vertical distribution differed widely. Preferential flow paths reached deeper soils in mature stands than in younger stands. Soil organic matter (SOM) content, saturated hydraulic conductivity (SHC) and soil metal content in the preferential flow paths were different from those in the soil matrix. SOM was 5% to 20% higher in the preferential flow paths than in the soil matrix. Average value of the SHC was 39.3 mm per minute in the preferential flow paths compared with 20.1 mm per minute in the soil matrix. Regardless of forest age, soil metal content was lower in the preferential flow paths than in the soil matrix. Soil metal content also showed a large difference in different aged forests.