Wildfire severity and postfire salvage harvest effects on long‐term forest regeneration

Following a wildfire, regeneration to forest can take decades to centuries and is no longer assured in many western U.S. environments given escalating wildfire severity and warming trends. After large fire years, managers prioritize where to allocate scarce planting resources, often with limited inf...

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Published in:Ecosphere (Washington, D.C) Vol. 11; no. 8
Main Authors: Povak, Nicholas A., Churchill, Derek J., Cansler, C. Alina, Hessburg, Paul F., Kane, Van R., Kane, Jonathan T., Lutz, James A., Larson, Andrew J.
Format: Journal Article
Language:English
Published: Washington John Wiley & Sons, Inc 01.08.2020
Wiley
Subjects:
Climate change
climatic tolerance
cold
Coniferous forests
Dispersal
Douglas fir
dry forest
fire severity
Forest & brush fires
forest regeneration
forests
Global warming
Harvesting
high severity
Influence
Larix occidentalis
lodgepole pine
managers
Physiology
Picea engelmannii
Pine trees
Pinus contorta var. latifolia
Pinus ponderosa
planting
ponderosa pine
Prescribed fire
Pseudotsuga menziesii
regeneration
resilience
salvage harvest
salvage logging
Salvage operations
Seed dispersal
stems
timber production
Trees
Trends
uncertainty
Vegetation
Washington (state)
Water stress
weather
western larch
wildfire
Wildfires
United States > US
Washington (state)
ISSN:2150-8925, 2150-8925
Online Access:Get full text
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Summary:Following a wildfire, regeneration to forest can take decades to centuries and is no longer assured in many western U.S. environments given escalating wildfire severity and warming trends. After large fire years, managers prioritize where to allocate scarce planting resources, often with limited information on the factors that drive successful forest establishment. Where occurring, long‐term effects of postfire salvage operations can increase uncertainty of establishment. Here, we collected field data on postfire regeneration patterns within 13‐ to 28‐yr‐old burned patches in eastern Washington State. Across 248 plots, we sampled tree stems <4 m height using a factorial design that considered (1) fire severity, moderate vs. high severity; (2) salvage harvesting, salvaged vs. no management; and (3) potential vegetation type (PVT), sample resides in a dry, moist, or cold mixed‐conifer forest environment. We found that regeneration was abundant throughout the study region, with a median of 4414 (IQR 19,618) stems/ha across all plots. Only 15% of plots fell below minimum timber production stocking standards (350 trees/ha), and <2% of plots were unstocked. Densities were generally highest in high‐severity patches and following salvage harvesting, although high variability among plots and across sites led to variable significance for these factors. Post hoc analyses suggested that mild postfire weather conditions may have reduced water stress on tree establishment and early growth, contributing to overall high stem densities. Douglas fir was the most abundant species, particularly in moderate‐severity patches, followed by ponderosa pine, lodgepole pine, western larch, and Engelmann spruce. Generalized additive models (GAMs) revealed species‐level climatic tolerances and seed dispersal limits that portend future challenges to regeneration with expected future climate warming and increased fire activity. Postfire regeneration will occur on sites with adequate seed sources within their climatic tolerances.
Bibliography:Corresponding Editor: Carrie R. Levine.
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ISSN:2150-8925
2150-8925
DOI:10.1002/ecs2.3199