Careful tree thinning

This summer, Seattle Parks & Recreation Department staff will be thinning trees in Magnolia’s Discovery Park to create better tree health and forest growth.

Friends of Discovery Park President Phil Vogelzang said members and city staff want to spread the word early before the tree removal takes place.

“Whenever people see people with chainsaws, cutting down trees in Discovery Park, there’s always concern and anxiety raised,” Vogelzang said.

Two localized areas of Discovery Park are targeted for tree removal, which is likely to happen in the late summer after nesting season is over. The first is a stand of trees near the old hospital site, which has stunted and crowded Douglas firs growing in the area. Vogelzang said about 20 percent of the trees in that small area will be removed. The trees are “tiny,” he said, only 30 to 40 feet tall and maybe 3 to 4 inches in diameter and are growing very close together.

“Pretty much anyone who looks at them realizes it is not a healthy forest,” he said.

The second area that will be thinned is by the south parking lot. Vogelzang said when those trees were first planted, the city placed too many, too close together thinking only some would live. Unfortunately, the majority lived but, again, produced stunted trees that grew without the needed 20 to 30 feet of space necessary for a healthy forest.

“It’s very much a monoculture of tiny, closely spaced trees that are all the same age,” Vogelzang said.

Again, Vogelzang said a small amount of the trees in that area will be removed to give the healthier trees a chance to grow and create a better forest environment.

All of the trees removed will be carefully selected and specifically removed to improve the forest health.

Vogelzang said city staff, including two arborists, and volunteers toured the park and identified the areas that needed to be thinned in order to free up space, permit more sunlight to come in and allow the trees to grow without having to compete for space or water.

“A forest is healthy when all the trees get an adequate amount of sunlight and an adequate amount of room to grow,” Vogelzang said, adding the ideal forest also features young trees and old trees and a wide range of foliage.

While there is a lot of discussion centering around the dwindling size of Seattle’s tree canopy, Vogelzang said, in this case, the tree thinning is necessary to improve the quality of the tree canopy in Discovery Park. When trees grow too close together and have to compete for space, they don’t store as much carbon or release as much oxygen. Removing the smaller, stunted trees will actually allow the bigger, healthier remaining trees to grow faster, store more carbon, produce more oxygen and allow for a more diverse understory to grow.

The idea behind removing these trees is to promote a healthy understory,” Vogelzang said, adding currently the sections targeted for tree removal have limited or no understory, and Friends of Discovery Park volunteers actively work to maintain a biodiverse forest with native plants growing.

Vogelzang said city staff will be posting signs throughout the park warning people of the tree thinning so they can expect it when the time comes. He doesn’t expect the tree removal to take more than a few weeks, however.

What happens to the trees when they are cut down is still being decided upon. While Vogelzang said all the waste will remain in the park in some form, there are a few different options as to how it will be used. The first idea is to leave the waste where it is because it is quicker and less expensive for the city, and it also discourages people from creating new trails in the park. Another idea is to mound it up to create habitat for wildlife. Some of the waste will likely be chipped and turned into mulch, Vogelzang said.