Many of the trees at Strawberry Hill Park are too skinny because the forest is too thick.

So, Bainbridge Island Metro Parks and Recreation plans to thin them out so the strongest trees survive.

“It should not be this heavily stocked for this size of tree,” said Lydia Roush, natural resources manager for Bainbridge parks. “It’s kind of a miracle more trees haven’t come down, or they’re not in even worse shape.”

The 10-acre parcel reflects the shifting uses of the landscape. You can see it in their rings: a 5-10 year burst of enthusiastic growth – wide, healthy circles at the core – followed by decades of stagnation as the trees fought each other for nutrients and sunlight. Parts of the forest grew at 300 trees per acre, half-again above a sustainable density.

In a warming world, carbon sequestration has taken on new urgency. Carbon sequestration, Roush said, is a function of trees adding new mass each year. It’s hoped that thinning will help the remaining trees bulk up, and boost the understory below. “Once we open this up and let some sunlight in,” she said, “I think what’s here will really take off.”

Ironically, the stand’s density helps keep it upright. Roush likens thinning to “a high-risk game of Jenga” – removing the “blocks” to the point where the best trees will still stand on their own.

Bike park

Meanwhile, tree removal is also a part of the new mountain bike park. John Benjes, a member of the park district’s bike park advisory group, said it’s a great location. “Just the lay of the land, it’s got plenty of slope for great trails, and a lot of variability in the slopes to make very interesting riding. Every trail will be different, every trail will be fun for every rider.”

Benjes and local mountain bike clubs are grubbing out holly, ivy and other invasives. Seattle-based Evergreen Mountain Bike Alliance is designing the bike park, to feature downhill runs of progressive difficulty with jumps, berms and other challenging features. A skills area will let new and inexperienced riders hone their chops. The bike park plan is expected to go to the BI park board by the end of the year. Fundraising by the parks and trails foundation will follow.

Also, Winslow’s Moritani Preserve will see more thinning on its west and north boundaries as part of a five-year stewardship plan, and the park district is assessing the health of tree stands at other parks, including Grand Forest East.