Effects of plot length and soil texture on runoff and sediment yield occurring on machine-trafficked soils in a mixed deciduous forest

Abstract

Runoff decreased significantly in each soil texture group, as plot length increased (2–40 m), whereas sediment yield showed an increasing trend. Runoff and sediment yield were higher in the clayey soil than in the loamy soil texture. An important issue for decreasing the negative impact of ground-based skidding operations on the physical environment is the appropriate drainage of the surface flow away from the skid trail to decrease runoff and subsequent soil loss. Water diversion structures can be used to disperse the water from the trail to the stand but information on adequate spacing is lacking, especially when considering machine-trafficked forest soils. The objective of this study was to quantify the effects of plot length (2, 5, 10, 20, 30, and 40 m) and two soil texture types (clayey and loamy) on runoff and sediment yield in skid trails in a mixed deciduous forest in order to determine the ideal spacing between adjacent water diversion structures. Runoff and sediment yield were measured for 25 rainfall events occurring over a 6-month period. The Pearson correlation was applied to determine the relationship among runoff, sediment yield, selected soil properties, plot length, soil texture, and canopy cover. In each soil texture group, runoff and sediment were plotted with rainfall intensity and plot length by a Gaussian polynomial regression model. Results show that plot length and soil texture significantly affected the amount of runoff and sediment yield. Plot length was positively and significantly correlated with sediment yield and negatively correlated with runoff. The highest runoff was found on the plot length of 2 m under clay soil by 1.49 mm followed by plot length of 5 m with clay by 1.15 mm and plot length of 2 m with loamy soil by 1.03 mm. In both soil texture classes, the runoff decreased significantly, as plot length increased. Likewise, in each plot length tested, the values of runoff were higher in the clayey soil than in the loamy soil texture. Significantly higher values of sediment yield were found in the plot length of 40 m and 30 m under the clayey soil (8.63 g m−2 and 6.84 g m−2) followed by plot length of 40 m under loamy soil (6.15 g m−2). In each soil texture, sediment yield increased significantly, as plot length increased. Additionally, in each plot length, sediment yield was higher in the clayey soil than in the loamy soil texture. The results of this study can be applied to mitigate the environmental impacts of ground-based skidding operations on skid trails and to determine the optimal distance of water diversion structure.