Research Forester USDA Forest Service, PNW Research Station Wenatchee, Washington, United States
Abstract: Restoration treatments are used in dry coniferous forests of western North America to improve forest health, reduce fuels, and make forests more resilient to wildfires. Recent studies have shown that restoration treatments, particularly those that include prescribed burning, can be effective for ameliorating wildfire behavior and effects, though there are still fire weather thresholds beyond which forests can burn at high severity. Restoration treatments – especially those employing prescribed fire – may also provide benefits for post-fire forest recovery by promoting the establishment and persistence of woody and herbaceous plant populations that can persist through fire, rapidly generate post-fire organic soil cover, and compete with unwanted exotic plant species. The 2014 Carlton Complex – one of the largest wildfires in Washington State history – burned through many recently treated forest restoration units, offering an opportunity to evaluate the effects of different restoration (or fuel) treatments and burn severities on initial vegetation cover and diversity, longer-term vegetation dynamics, tree regeneration, and fuel dynamics following wildfire. We found that restoration treatments altered understory vegetation prior to wildfire and reduced tree mortality rates during wildfire. Restoration treatments also promoted faster recovery and higher understory plant cover during the first year following fire, but relative treatment effects diminished in the second and third years after fire. Post-fire fuel dynamics were driven by burn severity and pre-fire forest density and species composition. Natural tree regeneration after seven years was highly variable but appeared to be influenced primarily by seed source distances and local environmental conditions. This study shows that restoration treatment benefits are not limited to fire behavior and initial fore effects.
