Excerpts from a UC Berkeley Forest Research and Outreach blog post, with info aimed at landowners. It reminds us that thinning and fuels reduction isn’t only about reducing fire intensity/severity: it’s also about forest health.
What is forest resilience? Forest resilience is a measure of adaptability. It focuses on retaining a forest’s essential structure and composition to a range of stresses or complex disturbances. In other words, a resilient forest may lose some trees to drought, fire or insect attack, but the mortality rate will not overtake the forest’s ability to continue growing trees and provide habitat. Some will die, but many will live.
Today’s [Sierra] forests have huge increases in basal area and tree density compared to the historical record. Historically, forests were generally low in density yet highly variable in their structure, with open patches and clumps of trees. Twenty-two trees per acre was not uncommon in the Sierras, but those 22 trees were huge! The older and bigger trees get, the more adaptations they have, like thicker bark, a high canopy and higher levels of resilience to disturbances. We have normalized high density, homogeneous stand structure and high competition forests that would not have occurred historically. Today’s forests are more vulnerable to fire and drought related mortality due to a legacy of timber harvesting in early 1900’s that focused on large tree removal; a century of fire suppression policy and action, and climate change effects such as less humidity recovery in the night.
Timber harvesting or commercial thinning:
- Sometimes you have to commercially thin in order to restore lower density forest conditions;
- You can leverage saw logs/forest products to pay for other management activities; and
- It is effective in reducing tree density in the canopy and ladder fuels and reduces competition for the remaining trees.
Commercial thinning plus prescribed fire: Very effective in reducing tree density, ladder fuels and surface fuels. Combining meaningful thinning and prescribed fire can mitigate fire hazard and improved the growth and vigor of your trees to maximize resistance and resilience to wildfire and drought-related tree mortality!