Get Full Government Meeting Transcripts, Videos, & Alerts Forever!
Get email alerts on the Forest Health Assessment topic
No spam. Unsubscribe anytime.
Trust hears preliminary findings of 2024 forest health assessment for Mercer Island open spaces
Summary
A consultant‑led forest health assessment found wide spatial variability in tree density, coarse woody debris and understory invasive cover across trust properties; staff said the data will be used to establish baselines, guide planting and target future thinning or maintenance.
Natural Resources Program Manager Lizzie Stone presented preliminary results of the city’s 2024 forest health assessment at the Open Space Conservancy Trust meeting on April 29, noting the study will inform baseline metrics for the city’s climate action plan and future management decisions.
Stone said the city worked with Haven Ecology and Research to survey overstory and understory plots across trust properties. She told the trust the 2024 survey used macro (10×40 m) and micro (10×10 m and 5×5 m) plots that measured basal area, tree density, seedlings and saplings, ivy on trees, coarse woody debris volume and percent cover of understory species. She said there were 61 overstory plots across trust property and 196 understory plots on trust land.
Key takeaways: Stone reported “very wide variability” across plots. Most overstory trees in Pioneer Park and Engstrom were native, but some plots showed very high tree density while others were sparse. Coarse woody debris and snag volumes varied widely; some plots had roughly target levels (about 2,000 cubic feet per acre is a general forestry benchmark) while others had little. Seedling and sapling regeneration was spatially variable; deciduous regeneration (bigleaf maple) tended to be natural while conifer regeneration remained primarily from past plantings. Stone said the survey showed high non‑native understory cover is negatively correlated with native species richness, validating the program’s invasive‑removal and native‑planting strategy.
Questions and next steps: trustees asked about tree root disease, thinning, and how the assessment’s consultant recommendations align with city objectives. Stone said the study did not include a separate root‑disease survey and that potential thinning decisions will be plot‑by‑plot, informed by follow‑up inspections and arborist input. She said staff will use the survey to establish a baseline tied to the city’s climate action plan targets, update the open space vegetation management plan, investigate targeted thinning where appropriate, and refine planting priorities. Stone said staff expect to finalize baseline metrics and further analysis by the end of the year.
Context: trustees described the report as dense but informative, asked staff to return with prioritized recommendations that apply specifically to Mercer Island open space goals, and suggested using the assessment to aid volunteer planning, species selection and long‑term metrics for measuring restoration success.
