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Abstract Increases in the frequency and severity of climate-sensitive disturbances like wildfire, drought, and insect outbreaks pose an imminent threat to Earth’s forests, including their status as a net carbon sink. Forest treatments including thinning and prescribed fire are increasingly viewed as key tools for mitigating disturbance impacts, but their efficacy in stabilizing carbon stocks and reducing mortality, especially for drought and insect outbreaks, remains uncertain. Moreover, we have limited understanding of whether the moderating effect of forest treatments provides a net benefit to vegetation carbon stocks, or if the initial carbon loss required to implement treatments outweighs potential reductions in carbon losses during subsequent disturbance. Here we conduct a systematic meta-analysis of published literature to understand how thinning, prescribed fire, and combined treatments impact survival and carbon stocks following wildfires, droughts, and insect outbreaks. We found that treatments improved survival following wildfires, but had only marginal impacts on survival following drought and insect outbreaks. While thinning had a modest positive effect on carbon stocks following wildfire, treatments generally reduced carbon stocks following drought and had no impact following insect outbreaks. Overall, our findings suggest that the benefits of forest treatments for vegetation carbon stocks are limited, especially following drought and insect disturbances. These findings have important policy implications for carbon credit programs.
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Valuation of forest‐management and wildfire disturbance on water and carbon fluxes in mountain headwaters
Recent drought, wildfires and rising temperatures in the western US highlight the urgency of increasing resiliency in overstocked forests. However, limited valuation information hinders the broader participation of beneficiaries in forest management. We assessed how historical disturbances in California's Central Sierra Nevada affected live biomass, forest water use and carbon uptake and estimated marginal values of these changes. On average, low‐severity wildfire caused greater declines in forest evapotranspiration (ET), gross primary productivity (GPP) and live biomass than did commercial thinning. Low‐severity wildfires represent proxies for prescribed burns and both function as biomass removal to alleviate overstocked conditions. Increases in potential runoff over 15 years post‐disturbance were valued at $108,000/km2for commercial thinning versus $234,000/km2for low‐severity wildfire, based on historical water prices. Respective declines in GPP were valued at −$305,000 and −$1,317,000/km2, based on an average social cost of carbon. Considering biomass levels created by commercial thinning and low‐severity fire as more‐sustainable management baselines for overstocked forests, carbon uptake over 15 years post‐disturbance can be viewed as a benefit rather than loss. Realizing this benefit upon management re‐entry may require sequestering thinned material. High‐severity wildfire and clearcutting resulted in greater declines in ET and thus greater potential water benefits but also substantial declines in GPP and live carbon. These lessons from historical disturbances indicate what benefit ranges from fuels treatments can be expected from more‐sustainable management of mixed‐conifer forests and the importance of setting an appropriate baseline.
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- Award ID(s):
- 2153040
- PAR ID:
- 10522920
- Publisher / Repository:
- Wiley Online Library
- Date Published:
- Journal Name:
- Ecohydrology
- Volume:
- 17
- Issue:
- 3
- ISSN:
- 1936-0584
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1002/eco.2642
