The effect of sawdust mulch application on amount of runoff in the skid trails (Case study: Kheyrud Forest)

Forest machinery traffic on forests causes significant changes in increasing the bulk density, reducing porosity, ventilation and reducing water infiltration rate which resulted in an increasing surface runoff. According to the results of previous studies on the effect of mulch on reducing runoff in laboratory conditions, The aim of the present study was to determine and compare the amount of runoff produced in untreated skid trail, undisturbed forest (control area), and the skid trail plots covered by sawdust, under natural conditions in Namkhaneh District, Kheyrud Forest to find useful strategies to reduce the effects of forest utilization in order to maintain the function of forest water protection and reduce runoff. In this study, the runoff plots (6 m2) were triplicate established and runoff collected by pipes in the outlet plots were measured based on natural rainfall conditions. The results revealed that applying sawdust mulch to the skid trail decreased runoff compared to the untreated skid trail, and the runoff amount in undisturbed forest, untreated skid trail and sawdust mulch treatments were 0.40, 1.44 and 0.71 mm, respectively. The highest and the lowest amount of runoff were found for untreated skid trail and undisturbed forest treatments, respectively. Also, by application of sawdust mulch, the amount of runoff produced reduced by 48.4%, while the amount of runoff before the use of mulch in skid trail was 72.2% higher than the intact forest. Also, the runoff produced in skid trail control treatment was 51.1% higher compared to sawdust treatment.