Effects of post-fire salvage logging and a skid trail treatment on ground cover, soils, and sediment production in the interior western United States

Post-fire salvage logging adds another set of environmental effects to recently burned areas, and previous studies have reported varying impacts on vegetation, soil disturbance, and sediment production with limited data on the underlying processes. Our objectives were to determine how: (1) ground-based post-fire logging affects surface cover, soil water repellency, soil compaction, and vegetative regrowth; (2) different types of logging disturbance affect sediment production at the plot and small catchment (“swale”) scales; and (3) applying logging slash to skid trails affects soil properties, vegetative regrowth, and sediment production. Four study areas were established in severely burned forests in the interior western USA. We installed plots at two study areas to compare burned but unlogged controls against skid trails, feller-buncher trails, and skid trails with added slash. Salvage logged and control swales were established at each study area, but only one study area had simultaneous measurements on replicated swales. Data were collected for 0-2 years prior to logging and from 2-8 years after logging.

The skidder and feller-buncher plots generally had greater compaction, less soil water repellency, and slower vegetative regrowth than the controls. Sediment production from the skidder plots was 10–100 times the value from the controls. The slightly less compacted feller-buncher plots produced only 10–30% as much sediment as the skidder plots, but regrowth was similarly inhibited. The relative differences in sediment production between the disturbed plots and the controls tended to increase over time as the controls exhibited more rapid regrowth. Adding slash to skid trails increased total ground cover by 20–30% and reduced the sediment yields by 5–50 times compared to the untreated skidder plots.

The replicated logged swales at one study area generally had higher sediment production rates than their controls but the absolute values per unit area were much lower than from the skidder and feller-buncher plots. Results from the swales at the other study areas indicated that logging did not increase runoff, peak flows, or sediment yields.

Vegetative regrowth and sediment production rates varied widely among the four study areas. This variation was largely due to differences in rainfall and soil properties, with the more productive sites having more rapid regrowth and thereby a more rapid reduction in sediment production. The susceptibility to surface runoff and erosion after high severity fires suggests that areas disturbed by ground-based salvage logging need additional mitigation practices.