Oak Survey Results
Our survey showed significantly lower quantities of mushroom crown shapes, indicating many oaks may not have the space or natural resources they need to fully expand. The trees with a mushroom crown shape were located on the edge of the woodland and into the prairie, where there is more space available. In the woodland center, where there is more overcrowding and higher competition, we noticed much higher quantities of columnar, vase, and asymmetrical crown shapes. Epicormic sprouts were recorded in about 60% of all trees measured. Our surveys illustrate that the columnar oaks located in the areas that received selective thinning have higher epicormic sprout counts, which indicates recovery from previous overcrowding. Our results suggest oaks are beginning to respond to the previous restoration project.
Left: percent share of all live oaks by epicormic sprout category; center: percent share of crown shape of all live oaks; right: map of crown shape distribution by woodland section. Crown shape categories are asymmetrical (red), vase (blue), columnar (green), and mushroom (purple).
The majority of snags measured in our project were Douglas fir, accounting for about half of all snags. All decay classes were seen amongst the woodland, however, higher decay classes were seen in oak snags compared to other snag species. Many of the conifer snags we noted had been man-made during previous restoration efforts. Few cavities were reported altogether, though oaks contained the highest amount of cavities compared to other species. Avian residency in both live and dead trees was observed throughout the assessment.
The majority of snags measured in our project were Douglas fir, accounting for about half of all snags. All decay classes were seen amongst the woodland, however, higher decay classes were seen in oak snags compared to other snag species. Many of the conifer snags we noted had been man-made during previous restoration efforts. Few cavities were reported altogether, however, avian residency in both live and dead trees was observed throughout the assessment.
Above: amount of snags per species (Douglas-fir, Oregon white oak, other, and unknown respectively).
Prairie Survey Results
In the prairie, there is a clear distribution of invasive and native species. Invasive species tend to cluster close together, as English hawthorn and Sweet briar rose are found dispersed within similar population boundaries. Some species, both invasive and native, are too widespread to map as they cover the entire prairie. This includes the invasive hairy and common vetch as well as the native tall camas. Native Western buttercups bloomed the earliest and were the most abundant flower in the prairie. Patches of multiple native flowers, clustered together, can be found within the upper border between the woodland and prairie. These rich hotspots of wildflowers are evidence of the historic legacy of mowing and cattle grazing that left edges of the prairie less disturbed to the effects of management, and with a high native seed volume. We have mapped these populations to prioritize removal treatments on invasive plants and to protect important native patches.
Left: mapped distribution of prairie species and estimated area they cover; center: total area per most common wildflower species; right: total area per most common invasive species.
Bird Survey Results
Multiple special status species were detected that Bob Altman did not detect in his 2018 survey. These birds include the acorn woodpecker, a lively woodland species that can be found nesting within tree cavities and using snags created from the Willamalane restoration efforts, as well as tending to a granary to store their acorn collections. A pair of nesting Western bluebirds were also detected this year, near a bird box within the prairie. However, the Chipping Sparrow, Yellow-breasted Chat, and Purple Finch were not detected within the survey times. Additionally, nesting sites within the park that include bird boxes and tree cavities are dominated by both tree swallows and invasive European starlings. These birds are not of any conservation concern. Ultimately, the bird surveys currently suggest the residence of oak-associated species that were not documented at the time of restoration actions, and indicate the furthering of a diverse, native oak habitat.
Above: species detected in each bird survey (prairie and woodland) compared to Altman’s surveys
Photo Points Results
Our photo points indicate there has been a change in foliage over time, as surrounding trees were removed. We notice an increase of epicormic sprouts on the trees located where selective thinning took place. This indicates some success from the treatment implemented in 2018. We also saw some new shrubs and maple trees beginning to regrow. Below is a few examples of photo points throughout the past six years.
Above: changes in foliage and epicormic sprouts from 2017 to 2022
Above: changes in density and vegetation from 2017 to 2022
Adaptive Management Recommendations
Based off of our findings, the Birds & Bloom team recommends:
In prairie and oak habitats to…
- Selectively removing competitive tree species
- Treating and removing invasive prairie species
- Assessing the benefits and limitations of a prescribed burn in the prairie
To promote avian residency by…
- Maintaining and installing bird boxes
- Maintaining and monitoring snags within the woodland
In terms of community education…
- Educating park visitors on the benefits of oak habitat restoration through signage and outreach events
- Enforcing leash laws to prevent disturbance of wildlife
- Setting up shoe brush site and signage near trailheads to prevent the introduction of new invasive species