Mapping Soil Organic Carbon in Wildfire-Affected Areas of the McKenzie River Landscape, Oregon, USA

Abstract:

In the Pacific Northwest (PNW), forest fires are increasing in frequency and severity because of changing temperature and precipitation patterns. Wildfires are an integral part of forest ecosystems in this region, but catastrophic fires that are becoming annually record-breaking are detrimental to plant life, atmospheric conditions, and the livelihoods of nearby people. Studying the effects of forest fires on soil and carbon dynamics will further our understanding of the impacts of climate change on the PNW and could potentially drive fire-related land management plans with a soils focus. Within the pool of total soil organic carbon, there are two divisions: mineral association organic carbon (stable) and particulate organic carbon (unstable), with pyrogenic carbon (unpredictable post-fire carbon) falling into either category. Forest soils are variable on even the landscape level; therefore, site-specific and geographically focused research is needed in order to understand how wildfires affect individual landscapes. In this study, we quantify and map the variability of soil carbon pools across a burn severity gradient (unburned old growth, low severity, and high severity) in order to assess the conditions of soil carbon one year after the Holiday Farm Fire (September 2020) in the McKenzie River, Oregon landscape. Mapping the movement of soil carbon after a wildfire will give insight to the potential changes on a local scale and may provide progress on the inquiry of using low severity burns as a mechanism for carbon sequestration in PNW forests, as this fire management tool does not have clear impacts on soil carbon.

Keywords: soil geography, climate change, wildfire, Oregon

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