In 2002, the Biscuit Wildfire burned a portion of the previously established, replicated conifer unthinned and thinned experimental units of the Siskiyou Long-Term Ecosystem Productivity (LTEP) experiment, southwest Oregon. Charcoal C in pre and post-fire O horizon and mineral soil was quantified by physical separation and a peroxide-acid digestion method. The abrupt, short-term fire event caused O horizon charcoal C to increase by a factor of ten to >200 kg C ha⁻¹. The thinned wildfire treatment produced less charcoal C than unthinned wildfire and thinned prescribed fire treatments. The charcoal formation rate was 1 to 8% of woody fuels consumed, and this percentage was negatively related to woody fuels consumed, resulting in less charcoal formation with greater fire severity. Charcoal C averaged 2000 kg ha⁻¹ in 0–3 cm mineral soil and may have decreased as a result of fire, coincident with convective or erosive loss of mineral soil. Charcoal C in 3–15 cm mineral soil was stable at 5500 kg C ha⁻¹. Long-term soil C sequestration in the Siskiyou LTEP soils is greatly influenced by the contribution of charcoal C, which makes up 20% of mineral soil organic C. This research reiterates the importance of fire to soil C in a southwestern Oregon coniferous forest ecosystem.

The increasing use of cable-assisted steep-slope harvesting has presented different operational, safety, and environmental opportunities and challenges. One of the primary benefits is the increased safety introduced when tethered equipment is used appropriately—notably, “appropriate” use is the use of cable tension for assistance, not stability. However, the stability of such equipment on realistic soils under wet or dry conditions is not well defined, blurring the transition between tethering as a safety measure or as an aid for traction. Therefore, we propose an approach that enables assessment of the stability and required tensions to ensure stable equipment operation under various configurations on steep slopes. A sensitivity analysis was performed, including two equipment track geometric parameters: track width and grouser depth, and soil properties by evaluating two distinctive soil types. Equipment geometry had a role in stability, but less than the influence of soil shear strength. For equipment properties, grouser depth presented the greatest effect on stability, concentrated between slopes of 36–70 percent. Greater soil moisture increases equipment stability in sandy loams and significantly decreases stability in clay loams. When the effects of soil properties are isolated, cohesion and angle of friction are the properties with the greatest effect on equipment stability.

Restoring resilient forest structure in the fire-prone, densely stocked forests of the Inland Pacific Northwest depends on mechanical thinning, much of it too steep for conventional ground-based equipment. Winch-assisted (tethered) harvesting has expanded mechanized access to such terrain, but its soil impacts on the ash-cap soils of the Blue Mountains remain poorly characterized, with research focused on near-surface response. This study characterized soil response following two operationally distinct tethered mechanized systems, cut-to-length (CTL) and whole-tree (WTL), within the same 15-ha unit on a 40% ash-cap slope in the Wallowa-Whitman National Forest, Oregon. Bulk density and moisture content were measured at the surface and at 30 cm across pre-harvest, immediate post-harvest, and one-year post-harvest periods, and cross-slope profiles were measured to quantify surface soil displacement. CTL corridors showed minimal immediate surface disturbance due to slash-mat protection but densified significantly by one year, likely driven by environmental exposure rather than machine traffic; sub-surface compaction was transient, relaxing within a year. WTL corridors densified immediately at the surface and remained elevated at one year, while sub-surface bulk density declined significantly below pre-harvest levels by one year, though this decrease may partly reflect sampling variability rather than a purely soil-driven process. Neither system showed sustained compaction at 30 cm after one year. These results indicate that, at this study site and under the operating conditions evaluated, no persistent increase in bulk density was detected at 30 cm depth for either system within the one-year monitoring period, though CTL and WTL produced distinct disturbance timelines that land managers should weigh when selecting equipment for similar terrain.