Hillslope sediment production after wildfire and post‐fire forest management in northern California

Abstract

High severity wildfires impact hillslope processes, including infiltration, runoff, erosion, and sediment delivery to streams. Wildfire effects on these processes can impair vegetation recovery, producing impacts on headwater and downstream water supplies. To promote forest regeneration and maintain forest and aquatic ecosystem functions, land managers often undertake active post-fire land management (e.g., salvage logging, sub-soiling, re-vegetation). The primary objective of our study was to quantify and compare sediment yields eroded from (a) burned, (b) burned and salvage logged, and (c) burned, salvage logged, and sub-soiled plots following the 2015 Valley Fire in the northern California Coast Range. We distributed 25 sediment

Factors affecting connectivity and sediment yields following wildfire and post‐fire salvage logging in California's Sierra Nevada

“…Hillslope erosion rates can increase with increasing disturbance from post‐fire logging (Chase, 2006; Demirtaş, 2017; Wagenbrenner et al, 2015), although some studies also show that post‐fire logging can have no effect or even reduce sediment yield (Cole et al, 2020; James & Krumland, 2018). The lack of significant difference in the transformed normalized sediment yields between logged and unlogged swales echoes past research that did not detect significant increases in sediment yield after logging in burned catchments (Chase, 2006; Chou et al, 1994; Stone et al, 2014; Wagenbrenner et al, 2015).…”

“…Best management practices and post‐fire precipitation events may strongly control erosional responses (Fernández et al, 2007; McIver & McNeil, 2006). Post‐fire logging may significantly increase woody material that provides surface cover (Robichaud, Lewis, et al, 2020; Wagenbrenner et al, 2015), intercepting precipitation and overland runoff and potentially mitigating effects from fire and mechanical disturbance due to logging (Cole et al, 2020; Poff, 1989; Prats et al, 2020). Equipment design and weight can reduce salvage logging impacts to soils (Lucas‐Borja et al, 2019, 2020; Wagenbrenner et al, 2016).…”

“…Other alternative practices used to harvest unburned trees such as over‐the‐snow skidding may also reduce impacts caused by post‐fire salvage logging, but to our knowledge these have not yet been tested in post‐fire salvage logging operations. Post‐logging site preparation activities may also increase or decrease erosion, adding yet another factor to the effects of wildfire and post‐fire logging (Cole et al, 2020; James & Krumland, 2018; Slesak et al, 2015).…”

Compaction and cover effects on runoff and erosion in post‐fire salvage logged areas in the Valley Fire, California

“…Second, the soil in the field had been subjected to erosion from natural rainfall during the 20 months since the fire and eight months since the post-fire skidding operations. Given the high soil erosion rates measured at BMDSF in an associated study (Cole et al, 2020), this resulted in a preferential removal of fines and soil armoring by lapilli in the field experiment (Shakesby, 2011) ( Figure 3). Furthermore, the relationship of rainsplash with surface cover was stronger than with bulk density across the two studies ( Figure 6).…”

“…Laboratory experiments allowed the detailed assessment of hydrologic and erosion processes under more controlled conditions while the field experiments provided results more relevant to natural conditions. The field experiments also allowed direct comparison of different in-situ soil conditions using the same rainfall inputs, thus eliminating the variation in the results due to precipitation identified in an associated field experiment (Cole et al, 2020).…”