From the top of towering Douglas-firs down to the leafy ferns in the understory, forests are an iconic symbol of our home here in King County. These forestlands are important for our everyday lives improving air and water quality, and providing places for us to hike, bike, ride a horse, or just sit and enjoy the view.
Over 29,000 acres of King County’s public forest lands are managed by King County Parks – Your Big Backyard. Of this acreage, roughly 3,800 acres are designated as working forests. These working forests provide many social and economic benefits for communities, including jobs and wood products, and provide sites for forestry education. King County Parks also owns conservation easements on 145,000 acres of public and private forest lands.
Types of Stewardship Actions
Many county forests are the product of past management actions that were not necessarily designed to create natural old forest structure. In order to help return forests to a more natural condition, King County Parks uses a variety of forest stewardship practices that mimic natural events. By implementing these practices, King County Parks ensures diversity of not only trees, but the animals that call the forest home.
Developing Stewardship Plans: King County is developing and implementing stewardship plans for our forests. These plans describe how the forests will be managed and the appropriate recreational activities for each site.
Ensuring Forest Health: In some cases, King County will conduct forest management activities that mimic natural events like fires and wind storms. These actions, such as thinning, vary the density and spacing of trees and promote diverse species and ages.
To increase the diversity of tree species in a forest, a variable thinning practice may be implemented. Using this method, foresters select the type of trees that need to be cut and removed to:
- Allow remaining trees to grow
- Make space to plant different species
After trees are removed, the area is replanted with a diverse array of tree species that results in a forest that has a mix of young and old trees.
There are two main types of variable forest management:
1. Variable Density -
In a variable density thinning, the trees are removed in a mixed manner, leaving large and small trees and retaining under-represented species to maintain biodiversity.
2. Variable Retention -
This practice mimics tree mortality that results from natural disturbances such as wind storms or fires much like old growth forests. In a variable retention harvest, trees are removed in patterns that create small to large gaps (up to 5 acres in King County forests) and intentionally leave groups and scattered standing live and dead trees.
Many of King County Parks’ forests were logged heavily and then neglected, allowing for red alder trees to dominate the landscape. Red alder is a pioneer tree species that quickly adapts to disturbed sites following fires, windstorms and large cut over areas known as clearcuts. To increase biodiversity and improve habitat, a red alder forest management practice can be implemented.
Using the variable retention technique, foresters create gaps in the canopy by removing most red alder in some areas, while retaining some alder and most or all conifers elsewhere. A variety of conifers such as Douglas-fir, western red cedar, grand fir, Sitka spruce and western white pine are planted in the open spaces that are created following tree removal.
Red alder conversions provide the following benefits:
- Improved habitat - By planting a variety of native conifer species while retaining red alder patches, the forest will eventually develop multiple canopy layers and more variable spaces that provide diverse wildlife habitat.
- More resistant forests - With more native conifers, forests become more bio-diverse. Research shows a more diverse forest is more resistant to disturbances such as insect attacks and disease, and is also better able to recover from such events. Diverse forests with a variety of tree species and ages are also more resilient to site conditions impacted by changes in climate.
A common tree disease in King County known as root rot is a fungus that destroys the roots of Douglas-fir, true firs, and western hemlock. The rot typically spreads via root contact in a circular direction, infecting the roots of surrounding healthy trees.
To prevent the disease from spreading, affected trees can be cut down around the center of the rot. The area is then replanted with trees (often western redcedar, white pine or broadleaf trees) that are not affected. In some cases, the affected trees are cut and left on the ground to return valuable nutrients to the soil.