Social and Behavioral Sciences Commons^™

Lightning-Ignited Wildfires In The Western United States: Ignition Precipitation And Associated Environmental Conditions, Dmitri Alexander Kalashnikov, John T. Abatzoglou, Paul Loikith, Nicholas J. Nauslar, Yianna Sotirios Bekris, Deepti Singh

Geography Faculty Publications and Presentations

Cloud-to-ground lightning with minimal rainfall (“dry” lightning) is a major wildfire ignition source in the western United States (WUS). Although dry lightning is commonly defined as occurring with <2.5 mm of daily-accumulated precipitation, a rigorous quantification of precipitation amounts concurrent with lightning-ignited wildfires (LIWs) is lacking. We combine wildfire, lightning and precipitation data sets to quantify these ignition precipitation amounts across ecoprovinces of the WUS. The median precipitation for all LIWs is 2.8 mm but varies with vegetation and fire characteristics. “Holdover” fires not detected until 2–5 days following ignition occur with significantly higher precipitation (5.1 mm) compared to fires detected promptly after ignition (2.5 mm), and with cooler and wetter environmental conditions. Further, there is substantial variation in precipitation associated with promptly-detected (1.7–4.6 mm) and holdover (3.0–7.7 mm) fires across ecoprovinces. Consequently, the widely-used 2.5 mm threshold does not fully capture lightning ignition risk and incorporating ecoprovince-specific precipitation amounts would better inform WUS wildfire prediction and management.

Spatial Analysis Of Streamflow Trends In Burned Watersheds Across The Western Contiguous United States, Heejun Chang, Will B. Long

Geography Faculty Publications and Presentations

Despite increasing magnitude and frequency of wildfire, understanding hydrological processes contributing to changes in streamflow is not well examined for the entire western contiguous United States (WCONUS). This study provides insight into whether considering spatially varying watershed characteristics, including burn severity patterns, can better explain streamflow trends at broad spatial and temporal scales. Standard geographically weighted regression (GWR) and multi-scalar (MS) GWR were benchmarked against ordinary least squares (OLS) regression to determine if spatially varying coefficients could better explain spatially varying patterns and processes of peak flow, low flow, center timing of flow, and flashiness trends in burned watersheds. In …

Reduced Fire Severity Offers Near-Term Buffer To Climate-Driven Declines In Conifer Resilience Across The Western United States, Kimberly T. Davis, Marcos D. Robles, Kerry B. Kemp, Teresa Chapman, Philip E. Higuera, Kerry L. Metlen, Jamie L. Peeler, Andres Holz, Multiple Additional Authors

Geography Faculty Publications and Presentations

Increasing fire severity and warmer, drier postfire conditions are making forests in the western United States (West) vulnerable to ecological transformation. Yet, the relative importance of and interactions between these drivers of forest change remain unresolved, particularly over upcoming decades. Here, we assess how the interactive impacts of changing climate and wildfire activity influenced conifer regeneration after 334 wildfires, using a dataset of postfire conifer regeneration from 10,230 field plots. Our findings highlight declining regeneration capacity across the West over the past four decades for the eight dominant conifer species studied. Postfire regeneration is sensitive to high-severity fire, which limits …

Event Scale Analysis Of Streamflow Response To Wildfire In Oregon, 2020, Will B. Long, Heejun Chang

Geography Faculty Publications and Presentations

Wildfire increases the magnitude of runoff in catchments, leading to the degradation of ecosystems, risk to infrastructure, and loss of life. The Labor Day Fires of 2020 provided an opportunity to compare multiple large and severe wildfires with the objective of determining potential changes to hydrologic processes in Oregon Cascades watersheds. Geographic information systems (GIS) were implemented to determine the total percentage burned and percentage of high burn severity class of six watersheds on the west slope of the Oregon Cascade Range. In addition, two control watersheds were included to contrast the influence of climatic effects. Spatial arrangements of burned …

Reimagine Fire Science For The Anthropocene, Jacquelyn K. Shuman, Jennifer K. Balch, Rebecca T. Barnes, Philip E. Higuera, Andres Holz, Multiple Additional Authors

Geography Faculty Publications and Presentations

Fire is an integral component of ecosystems globally and a tool that humans have harnessed for millennia. Altered fire regimes are a fundamental cause and consequence of global change, impacting people and the biophysical systems on which they depend. As part of the newly emerging Anthropocene, marked by human-caused climate change and radical changes to ecosystems, fire danger is increasing, and fires are having increasingly devastating impacts on human health, infrastructure, and ecosystem services. Increasing fire danger is a vexing problem that requires deep transdisciplinary, trans-sector, and inclusive partnerships to address. Here, we outline barriers and opportunities in the next …

A Possible Role For River Restoration Enhancing Biodiversity Through Interaction With Wildfire, Brittany E. Pugh, Megan Colley, Stephen J. Dugdale, Patrick Edwards, Rebecca Flitcroft, Andres Holz, Mathew Johnson, Michela Mariani, Mickey Means-Brous, Multiple Additional Authors

Geography Faculty Publications and Presentations

Background

Historically, wildfire regimes produced important landscape-scale disturbances in many regions globally. The “pyrodiversity begets biodiversity” hypothesis suggests that wildfires that generate temporally and spatially heterogeneous mosaics of wildfire severity and post-burn recovery enhance biodiversity at landscape scales. However, river management has often led to channel incision that disconnects rivers from their floodplains, desiccating floodplain habitats and depleting groundwater. In conjunction with predicted increases in frequency, intensity and extent of wildfires under climate change, this increases the likelihood of deep, uniform burns that reduce biodiversity.

Predicted synergy of river restoration and biodiversity increase

Recent focus on floodplain re-wetting and restoration …

Broad-Scale Surface And Atmospheric Conditions During Large Fires In South-Central Chile, David B. Mcwethy, René D. Garreaud, Andres Holz, Gregory T. Pederson

Geography Faculty Publications and Presentations

The unprecedented size of the 2017 wildfires that burned nearly 600,000 hectares of central Chile highlight a need to better understand the climatic conditions under which large fires develop. Here we evaluate synoptic atmospheric conditions at the surface and free troposphere associated with anomalously high (active) versus low (inactive) months of area burned in south-central Chile (ca. 32–41° S) from the Chilean Forest Service (CONAF) record of area burned from 1984–2018. Active fire months are correlated with warm surface temperatures, dry conditions, and the presence of a circumpolar assemblage of high-pressure systems located ca. 40°–60° S. Additionally, warm surface temperatures …