The 45 Road Ecological Thinning Project was the first such project conducted under the HCP. The site was a dense forest of small-diameter Douglas-fir trees with a salal-dominated understory.
Project objectives were to maintain/increase tree growth, increase structural diversity, improve plant species diversity, and facilitate decadence (standing and down dead wood) while protecting water quality and special habitats.
The project included 157 acres of variable density thinning, 64 acres of planting with a variety of native trees and shrubs, and 164 acres of untreated leave patches, to provide structural heterogeneity across the site.
To measure project effectiveness, trees, understory herbs and shrubs, dead wood, and seedling establishment and growth are being measured over time. Plots were measured before treatment, then at 1, 3, and 6 years post-treatment.
This graph illustrates that variable density thinning removed primarily the smaller trees in the project area. Increased light for the remaining trees allows them to increase both their diameter and crown. Over time, the number of the largest trees (over 20 inches) is increasing.
Upon exposure to more light, epicormic branches can sprout from the boles and branches of Douglas fir trees, seen here along the bole of the center tree. These branches allow the trees to rebuild their crowns, leading to higher structural complexity and individual tree vigor.
This is an example of variable density thinning one year after treatment, where the largest overstory trees are maintained.
This is the same plot six years after treatment, in 2009. Notice the growth of both the understory shrubs and trees.
Although thinning initially reduces shrub cover, the increased light available to the forest floor increases shrubs by year three, with an even greater response by year six. A similar trend was seen for herb species.
This is another plot from 2004, one year post-thinning.
By 2009 the understory has increased. The snags both protected and created during the project are still standing, seen to the back left of the center tree.