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

Author(s): Ryan P. Cole, Kevin D. Bladon, Joseph W. Wagenbrenner, Drew B. R. Coe
Year Published: 2020
Description:

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, subsoiling, revegetation). 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 subsoiled plots following the 2015 Valley Fire in the northern California Coast Range. We distributed 25 sediment fences (~75 m2 contributing area) across four hillslopes burned at high severity and representative of the three management types. We collected eroded sediment from the fences after precipitation events for five years. We also quantified precipitation, canopy cover, ground cover, and soil properties to characterize the processes driving erosion across the three management types. Interestingly, during the second year after the fire, sediment yields were greater in the burned‐only plots compared to both the salvage logged and subsoiled plots. By the third year, there were no differences in sediment yields among the three management types. Sediment yields decreased over the five years of the study, which may have occurred due to site recovery or exhaustion of mobile sediment. As expected, sediment yields were positively related to precipitation depth, bulk density, and exposed bare soil, and negatively related to the presence of wood cover on the soil surface. Unexpectedly, we observed greater sediment yields on the burned‐only plots with greater canopy closure, which we attributed to increased throughfall drop size and kinetic energy related to residual canopy. While these results will aid post‐fire management decisions in areas with Mediterranean climates prone to low intensity, long duration rainstorms, additional research is needed on the comparative effects of post‐fire land management approaches to improve our understanding of the mechanisms driving post‐fire erosion and sediment delivery.

Citation: Cole, Ryan P.; Bladon, Kevin D.; Wagenbrenner, Joseph W.; Coe, Drew B.R. 2020. Hillslope sediment production after wildfire and post-fire forest management in northern California. Hydrological Processes 34(26):5242-5259. https://doi.org/10.1002/hyp.13932
Topic(s): Fire Effects, Ecological - Second Order, Aquatic Life, Soils, Water
Ecosystem(s): None
Document Type: Book or Chapter or Journal Article
NRFSN number: 23058
FRAMES RCS number: 62059
Record updated: May 5, 2021