Immediate Post-Forest Fire Salvage Logging, Soil Erosion, and Sediment Delivery

A 4-year study of erosion associated with post-fire salvage logging was initiated on 10 headwater swales (0.35 to 0.57 ha; total 4.8 ha) within 40 days of fire containment, thereby capturing all post-fire rainfall. Seven swales received 1 of 4 combinations of logging and contour subsoiling treatments; 3 unlogged swales served as controls. Within this high-severity fire, control first-year sediment yields averaged 2.8 to 27 times greater than treated swales. Sediment yield was highly negatively correlated with increasing ground disturbance (R-2 = 0.87), including subsoiling and feller buncher tractor treads. Similar ground disturbance relationships were found for rill erosion measures: volume, surface area, and cross-sectional area at sediment fences. Control second-year sediment yields declined to 63% of first-year values but were twice that of all treated swales. Treated swales without subsoiling declined to 90% of first-year values. Swales with subsoiling doubled their first-year values but were collectively half of treated non-subsoiled swales. Third-year sediment yields were substantially lower than first-and second-year yields, with little difference among all swales. Fourth-year sediment yields were virtually non-existent. The study suggests that on moderately sloped sites affected by high-severity forest fires, salvage logging-particularly when implemented immediately post-fire-can substantially reduce erosion.