Effects of Ground-Based Skidding on Soil Physical Properties in Skid Trail Switchbacks

Ahmad Solgi,Petros A Tsioras,Ramin Naghdi,Eric K Zenner,Vahid Hemmati

doi:10.5552/crojfe.2019.535

Abstract

Effective skid-trail design requires a solid understanding of vehicle-soil interactions, yet virtually no data exist on the effects of harvest traffic on soils in the switchback curves common in mountainous terrain. We contrast for the first time the effect of skidding on dry bulk density, total porosity, macroporosity, and microporosity in the straight segments of the skid trail and in various positions within switchbacks of differing trail curvature (deflection angle) on different slope gradients. Treatment plots with three replications included combinations of two classes of curvature (narrow = high deflection angle, 60–70°; wide = low deflection angle, 110–130°) and two categories of slope gradient (gentle = ≤20%; steep = &gt;20%). The Cambisol soil was sampled in control and trafficked areas both before and after three passes with a rubber-tired skidder. After only three passes, significant effects were seen for dry soil bulk density (+), total porosity (–), macroporosity (–), and microporosity (+), with steady trends from undisturbed controls to straight segments to wide curves to narrow curves. Soil damage increased gradually and consistently toward the apex of the curve, particularly in narrow curves on gentle slopes. Our results establish that curvature and switchback position are important factors affecting soil compaction in ground skidding. The strong observed effects of even low harvest traffic volume on soil physical properties in curves indicate that the degree of soil compaction in skid trails may be underestimated in areas with numerous switchbacks, the placement of which within a skid trail system may require careful consideration on mountainous terrain.

Highlights

Compaction of forest soils is a major problem in ground-based timber harvesting with heavy machinery that can change the physical and chemical properties of the soil, soil fauna, and plant diversity (Farrakh Nawaz et al 2013) and result in extensive damage that can persist for many years (McColl 1995)
Whereas adverse effects on soil physical properties by ground-based timber harvesting with heavy machinery has been amply documented on skid trails (e.g., Grigal 2000, Ampoorter et al 2007), this study extends these findings showing that: Þ such adverse effects are enhanced in skid trail switchbacks compared to straight segments
We compared the effect of skidding on dry bulk density, total porosity, macroporosity, and microporosity in the straight segments of the skid trail and in various positions within switchbacks of differing trail curvature on different slope gradients

Summary

Introduction

Compaction of forest soils is a major problem in ground-based timber harvesting with heavy machinery that can change the physical and chemical properties of the soil, soil fauna, and plant diversity (Farrakh Nawaz et al 2013) and result in extensive damage that can persist for many years (McColl 1995). The damage caused by harvesting equipment is related to three major compacting forces exerted on soils:. The effect of these forces strongly depends on the number of equipment passes, various other factors further modify the extent and severity of soil compaction, including inherent soil properties such as soil texture, soil structure, soil organic matter, Effects of Ground-Based Skidding on Soil Physical Properties in Skid Trail Switchbacks (341–350) Soil compaction can reduce tree height, diameter, and volume growth (Williamson and Neilsen 2003, Murphy et al 2004, Tan et al 2006).

Objectives

Methods

Results

Discussion

Conclusion