Efficacy of leaf litter mulch to mitigate runoff and sediment yield following mechanized operations in the Hyrcanian mixed forests

Abstract

Purpose

Following ground-based skidding operations, understory vegetation and litter layer are commonly damaged or displaced by the movement of machines and timber on the machine operating trails, thus leaving the area vulnerable to increased runoff flow and sediment yield. One of the interim options available to suppress runoff and soil loss is the application of litter mulch directly after mechanized harvesting operations. The goal of the study is to assess the effects of broadleaves litter mulch on runoff and sediment yield immediately after rainfall events on a severely compacted skid trail in a mixed forest in Hyrcanian forests, northern Iran.

Materials and methods

The study included six treatments (undisturbed area, untreated trail, and four levels of litter rate; 0.42, 0.81, 1.31, and 1.69 kg m² referred to as LR1, LR2, LR3, LR4, respectively) and two levels of trail gradient (10% and 20%), replicated in three plots (7 m long × 1 m width).

Results and discussion

The highest runoff values of 1.54 and 1.33 mm were measured at trail gradients of 20 and 10% for the untreated trail, respectively. The litter mulch application resulted in runoff decreasing by 49%, 67%, 75%, and 79% in the LR1, LR2, LR3, and LR4 treatments, respectively. The highest values of runoff coefficient were measured in the untreated trail (U; 4.6%), followed by LR1 > LR2 > LR3 ≈ LR4 treatments. Sediment yield in the untreated treatment was 7.32 g m⁻² on the 10% gradient trail and 6.15 g m⁻² on the 20% trail gradient. Sediment yield values in the LR1, LR2, LR3, and LR4 treatments were decreased by 76%, 85%, 90%, and 93%, respectively, compared to the untreated treatment.

Conclusions

By increasing the litter rate, runoff and sediment yield responses significantly decreased as the rainfall increased. The net differences between the tested litter rates and the runoff and sediment yield reductions were higher with increasing rainfall intensity.

from Energy Ecology Environment Ambio via Terpsi Hori on Inoreader https://ift.tt/2rIKnRU