The role of brush mats in mitigating machine-induced soil disturbances: an assessment using absolute and relative soil bulk density and penetration resistance

Abstract

Forest soils often exhibit low bearing capacities and as a result are often incapable of withstanding high axle loads. In New Brunswick, Canada, five different brush amounts (0, 5, 10, 15, and 20 kg·m–2) were applied as brush mats on machine operating trails during a cut-to-length harvesting operation in a softwood stand to analyze soil disturbance as a result of off-road forest harvesting machine traffic. Soil absolute and relative bulk density and soil penetration resistance measurements were completed below the varying brush mats both before and after forwarding. The mean differences between pre- and post-impact absolute soil dry bulk density values recorded on track areas were 0.24 g·cm–3 for 5–20 kg·m–2 of brush and 0.33 g·cm–3 for 0 kg·m–2 of brush. On average, 40.5%, 17.9%, 14.3%, 15.5%, and 3.6% of all post-forwarding measurements exceeded the threshold for growth-impeding soil bulk density (80% standard Proctor density) for 0, 5, 10, 15 and 20 kg·m–2 of brush, respectively. Soil penetration values >3.0 MPa represented 23.7%, 15.0%, 9.4%, 4.6%, and 0.7% of all post-forwarding test plots with 0, 5, 10, 15, and 20 kg·m–2 of brush, respectively. The results suggest that softwood brush mats of 10 to 20 kg·m–2 placed on machine operating trails play a considerable role in reducing forwarder-induced soil compaction and penetration resistance.

Predicting rut depth induced by an 8-wheeled forwarder in fine-grained boreal forest soils

“…Moreover, it has to be noticed that the wheeling experiments were performed without any protective brush mat. It is well-known that the protective mat effectively reduces magnitude of soil displacement (Poltorak et al 2018;Labelle et al 2019).…”

“…At harvest, logging trail networks should be carefully planned by directing main routes to the areas withstanding the heaviest load, minimizing the number of passes on trails with low bearing capacity or by widening trail width by steering the tires not to follow exactly the same track in every pass (Uusitalo et al 2015). Rutting can also be minimized by processing the trees above the trail leading to formulation of protective brash mat (Murphy et al 2009;Poltorak et al 2018;Labelle et al 2019). Technical factors that decrease soil damage include total mass of a machine (Ampoorter et al 2010;Liu et al 2010), tire dimensions (Haas et al 2016), tire pressures (Eliasson 2005), tracks (Bygdén et al 2003;Sakai et al 2008;Haas et al 2016), steering and transmission system (Edlund et al 2012), distribution of vertical stress induced by tires or tracks (Vossbrink and Horn 2004;Horn et al 2007) and traffic intensity (Ampoorter et al 2010).…”

Timber extraction by cable yarding on flat and wet terrain: a survey of cable yarder manufacturer’s experience

“…Manufacturers of ground-based solutions seek to lower the impact of machine traffic on soils by enlarging the contact area between machine and soil through adapting tyre pressure, hydro-pneumatic suspension (e.g. the Forwarder2020 project, FORWARDER2020) and employing wider or longer tracks (Ala-Ilomäki et al 2011), as well as by reinforcing strip roads with brush mats (LaBelle et al 2019) or smart routing solutions to bypass areas of very low bearing capacity. Recent developments for soft terrain include an optional fifth axle for PONSSE forwarders or a forwarder with a rubbertracked undercarriage (OnTrack project, OnTrack 2017).…”

Management Implications of Using Brush Mats for Soil Protection on Machine Operating Trails during Mechanized Cut-to-Length Forest Operations

“…As a result, efficient spatial distribution of brush over a trail network is mostly addressed on a stand-by-stand approach. The 6 brush mat amounts used for calculations (5,10,15,20,25, and 30 kg m −2 ) were selected based on previous studies where identical brush amounts were subjected to forwarder traffic while load distribution was recorded below the mats [6][7][8]15].…”

“…The use of brush as a soil protective layer during mechanized forest operations has been proven to lower average dynamic peak ground pressures [6,8], minimize soil compaction [9][10][11][12][13], reduce soil resistance to penetration [14,15], and lower rut depth [7,10,12]. Using brush mats on machine operating trails is therefore a key method of minimizing the negative effects of heavy machine traffic on forest soils.…”