Short-term postfire dynamics following stand-replacing fire in the western Cascades

Status

Completed

Start Date

May, 2020

New vegetation after the 2017 Norse Peak Fire in western Washington. Photo by courtesy of Mark Stone, University of Washington.

Forest response to wildfire in the western Cascades of Washington and northwest Oregon is challenging to anticipate because fires are relatively rare and successional processes play out over years to decades.

Several notable wildfires that have occurred since 2014 provide a unique opportunity to track postfire dynamics in real time. In this project, we are examining how postfire vegetation responds to the interaction of burn severity, forest zone (warm or cold), and prefire stand age under a warming climate.

This study is part of the West-Side Fire and Climate Adaptation Research Initiative convened by the PNW Research Station in 2019.

Overview
Research
People
Resources

Project Description

Infrequent, stand-replacing fires are characteristic of many forests on the west side of the Cascade Range. In this project, we will sample vegetation in areas burned over past two decades in northwestern Oregon and Washington, including areas burned by the 2020 Labor Day fires.

We will use targeted field sampling to examine postfire ecological dynamics and their relationship to (reconstructed) prefire forest structure and age, burn severity, local topography, distance to seed sources, and postfire climate. Through multiple meetings (virtual and in the field), we will continually seek and incorporate stakeholder input into our study design and research communications.

Purpose and Scope

In collaboration with our partners and other funding agencies, we will install long-term vegetation plots that will provide critical insights about early vegetation development after disturbance for both scientists and land managers.

This project has three main objectives:

Quantify initial vegetation establishment and successional trajectories through the establishment of long-term permanent plots.
Improve understanding of the conditions that result in abundant or sparse natural regeneration.
Understand the drivers of variability in early-seral community structure, function, composition, and persistence following fire.

Methods

We will establish 1-hectare sample plots across each of the following categories:

Burn severity: Unburned; Less than severe (<~50% tree mortality); Severe (>90% tree mortality)
Forest zones: Warm or cold
Range of stand ages at the time of fire: Young (~60 years old) to late-seral (>250 years old)

Plots will be distributed across these gradients (up to four plots in each level of burn severity, two forest zones, and in varying levels of pre-fire stand age—depending on stand ages and forest zones that burned in each fire). In each plot, we will collect data on the following:

Prefire forest structure and burn severity
Snags and coarse woody debris
Postfire vegetation response

Project Deliverables

This project will result in a network of georeferenced long-term monitoring plots to assess postfire ecosystem trajectories in west-side forests with long fire return intervals.

Related Projects:

Re-evaluating historical fire regimes in west-side forests of the Pacific Northwest
Novel analysis of existing risk assessment data: Evaluation of plausible future community wildfire disasters in western Oregon and Washington
Assessing wildfire risk to municipal drinking water sources
Simulating the impacts of climate change on west-side fire regimes
Monitoring the effect of marine layer weather on active fires in the Rogue River Basin
Wildfire effects and postfire trajectories from an augmented, spatially balanced forest monitoring system