Boulder Creek Forest Restoration
Now that lightning strikes are quickly extinguished, the landscape has changed. Timber extraction, grazing and mining have also contributed to these changes. Today, the absence of frequent fire in Whiskeytown's forests has altered the ecological structure and composition within which these ecoystems evolved. For significant portions of the park, there has been an overall shift towards dense, heavily-stocked trees, which are primarily species adapted to shady conditions. These shade-loving species include Douglas-fir from 2,000 to 3,500 feet in elevation, with white fir becoming more prevalent as you climb above 3500 feet. In many places, the combination of logging and fire suppression has allowed the establishment of entirely different plant communities. Areas that were once open mixed conifer forests or open oak woodlands are now dominated by even-aged dense fir trees with little or no herbaceous or grass species in the understory. This crowded condition increases the chances of crown fire, pest outbreaks, and competition-induced stress on large diameter and older trees.
Park staff sought assistance from the Department of Forestry and Watershed Management at Humboldt State University and the Applied Forest Management Program at the University of Montana in assessing the condition of the park's old growth trees and developing a forest restoration strategy. These studies were able to determine the historic conditions of the forests, before settlers arrived in the mid-1800's, and determined that many areas were selectively logged in the 1950's and 1960's. Typically, the large and vigorous conifers were harvested and non-merchantable species like oaks and small diameter conifers were left. The ponderosa pines and old big black oaks that you find today in the upper canopy most likely witnessed the historic stand conditions and the extraction of timber. These trees experienced a period of increased growth and vigor after the other large trees were removed from the forest, which released light, water and nutrients in the process.
Historically, significant portions of the park could be described as an open woodland dominated by black oak, with ponderosa pine in lesser proportions. These areas were most likely once maintained by the local Native American tribes, which often targeted black oak stands for frequent underburning. Black oak acorns served as a valuable food source, so it makes sense that Native Americans maintained these stands through active fire management. The consequences of frequent low intensity fire include gaps within the canopy, a rich seed bed, and light reaching the forest floor, which results in a diverse understory of grasses, forbs, and shrub species, and even the germination of tree species. Specific to Whiskeytown, areas like "Sheep Camp" in the Brandy Creek watershed acquired its name because historically, there was once a diverse understory of grasses and forbs that could provide abundant forage for the livestock of early European settlers.
Today, many of these areas have transitioned into a very different forest type with an understory containing few species and seedlings. The dominant tree species have also shifted from black oaks with spreading limbs and diverse conifer species, to a dense Douglas-fir dominated forest. Is some areas, there is evidence of competition-induced stress and mortality, with a substantial quantity of dead and down woody material on the forest floor. Lacking intervention, the historically dominant oak woodland/ponderosa pine forest will not regenerate under current conditions, which lacks light and a natural fire regime of frequent low intensity fire. Although the stand conditions vary throughout the park, there are some locations that can make you feel as though you have walked into a closet and shut the door; it is dark and eerily silent.
Recognizing how substantially these forests have changed within such a short amount of time is alarming. Prescribed fire is typically used for maintaining these fire adapted ecosystems and is highly effective if the Douglas-fir is in the seedling/sapling stage. However, as Douglas-fir increases in size, they become more resistant to low intensity fires, which is typically the intensity of prescribed fire. Only under the hottest burn prescriptions allowable could prescribed fire begin to kill Douglas-fir that has encroached over the last 70 years, but this intensity of fire has the potential to kill the old oaks and conifers, which are already stressed and in a weakened state. Therefore, the removal of many of these young trees must be addressed by other means, such as mechanical equipment, to remove the larger, more fire-resistant Douglas-fir prior to the use of prescribed fire.
The overall goal of this forest restoration project is to retain old growth oaks and all of the large vigorous mature conifers, which will be released from the stresses of neighboring competition. In doing so, the park hopes to reduce the adverse impacts associated with future fire events, improve the vigor and survivorship of overstory trees, and to facilitate future prescribed fire operations. It is these prescribed fires that will be used to maintain these stands, by naturally thinning out the understory, reducing the surface fuel loads, and stimulating the native grass and herbaceous species in the understory. Park staff will have long-term monitoring plots and photo points installed in control and treated areas to track changes over time of such characteristics as seedling recruitment, tree diameter distribution, snag recruitment and longevity, forest floor fuel and coarse woody debris levels and accumulation rates, and grass, herbaceous, and shrub species cover.
The protection of these ecosystems is crucial not only at the park level, but also on a much larger global scale as stands of old growth trees are becoming rare. Logging and fire suppression has had a significant impact, but climate change is also contributing to the stress and decline of these old growth trees as they are sensitive to changes in precipitation. Increases in temperatures have been documented in drought stress, insect and pathogen outbreaks and the overall recent forest die-back in western North America. These conditions create landscapes that are susceptible to catastrophic fire and threatens habitat for many species of concern, such as the northern spotted owl and Pacific fisher. Similarly, due to their large size and the significant below-ground carbon pools, old growth forests store much more carbon than any other type of forest. Therefore, the conservation and protection of these large trees should be a priority for reversing the adverse effects associated with climate change.
For additional information:
Check out the 2008 Whiskeytown Nugget Safeguarding the Old Growth Forests of Whiskeytown article.