Hillslope erosion and sediment yield after wildfire and post-fire forest management in California's Northern Coast Range

High-severity wildfire can increase erosion on burned, forested hillslopes. Forest managers often use multiple post-fire strategies, including salvage logging, to extract economic value from burned landscapes, reduce fuel loading, and improve worker and visitor safety. Few studies have assessed the impact of post-fire salvage logging or alternative land management approaches on erosion in forested landscapes. In September 2015, the Valley Fire burned approximately 31,366 ha of forested land and wildland-urban interface in California's Northern Coast Range, including most of Boggs Mountain Demonstration State Forest. Many of the burned hillslopes were subsequently managed using post-fire salvage logging, subsoiling, vegetation control, and tree planting. The primary objective of our study was to quantify and compare plot scale ( 75 m²) erosion rates from the different post-fire land management treatments. We measured sediment yields using sediment fences in four sets of replicated plots. We also quantified ground cover, soil water repellency, canopy openness, field saturated hydraulic conductivity, and precipitation depth and intensity in each plot to understand site factors influencing erosion. Preliminary results indicate that burned, unlogged reference plots yielded the highest median sediment over the 2017 water year (34 Mg ha^-1), followed by burned, logged, and subsoiled plots (17 Mg ha^-1) and burned and salvage logged plots (6.9 Mg ha^-1). During water year 2018, herbicide was applied to some of the salvage logged and subsoiled plots. Water year 2018 median sediment yields ranked by treatment were subsoiled + herbicide (3.3 Mg ha^-1), subsoiled (1.7 Mg ha^-1), unlogged reference (1.2 Mg ha^-1), logged + herbicide (0.80 Mg ha^-1), and logged (0.41 Mg ha^-1). Cumulative sediment yields for WY 2018 were substantially lower than 2017 likely due to a combination of reduced hillslope sediment supply from previous erosion and less total rainfall. These results support a recent study suggesting post-fire salvage logging decreases sediment yields, but contradicts the majority of past studies indicating salvage logging increases sediment yields at small spatial scales.