Patterns, Drivers, and Implications of Postfire Delayed Tree Mortality in Temperate Conifer Forests of the Western United States

Authors

Sebastian Busby, Portland State University
Cody Evers, Portland State UniversityFollow
Andrés Holz, Portland State UniversityFollow

Sponsor

National Science Foundation. Grant Numbers: EAR-1738104, GSS-1832483

Published In

Ecosphere

Document Type

Article

Publication Date

4-11-2024

Abstract

Conifer forest resilience may be threatened by increasing wildfire activity and compound disturbances in western North America. Fire refugia enhance forest resilience, yet may decline over time due to delayed mortality—a process that remains poorly understood at landscape and regional scales. To address this uncertainty, we used high-resolution satellite imagery (5-m pixel) to map and quantify delayed mortality of conifer tree cover between 1 and 5 years postfire, across 30 large wildfires that burned within three montane ecoregions in the western United States. We used statistical models to explore the influence of burn severity, topography, soils, and climate moisture deficit on delayed mortality. We estimate that delayed mortality reduced live conifer tree cover by 5%–25% at the fire perimeter scale and 12%–15% at the ecoregion scale. Remotely sensed burn severity (1-year postfire) was the strongest predictor of delayed mortality, indicating patch-level fire effects are a strong proxy for fire injury severity among surviving trees that eventually perish. Delayed mortality rates were further influenced by long-term average and short-term postfire climate moisture deficits, illustrating the impact of drought on fire-injured tree survival. Our work demonstrates that delayed mortality in conifer forests of the western United States can be remotely quantified at a fine grain and landscape scale, is a spatially extensive phenomenon, is driven by fire–climate–environment interactions, and has important ecological implications.

Rights

© 2024 The Authors. Ecosphere published by Wiley Periodicals LLC on behalf of The Ecological Society of America.

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

DOI

10.1002/ecs2.4805

Citation Details

Busby, S., Evers, C., & Holz, A. (2024). Patterns, drivers, and implications of postfire delayed tree mortality in temperate conifer forests of the western United States. Ecosphere, 15(4), e4805.