For more than 35-years, Pioneer Parkway has been lined with silver maple trees. These fast-growing, softwood trees provide shade, beauty, and some benefits to wildlife. It would be difficult to imagine Pioneer Parkway without these trees.
As we began the process of designing a trial that will run along the road, we wanted to keep in mind the benefits of these trees while also providing the safest route for pedestrians and bicycles.
City leaders took into consideration four critical elements of the project.
- Safety of the trail users and motorists
- Potential construction impacts
- Age and quality of the trees
- Diversifying the greenbelt with different species of trees
Safety of Trail Users and Motorists
Safety is the most important consideration of this project. The trail must be strategically placed to ensure all users are as safe as possible, so this means having some space between the back of the curb and the trail. In most areas, this distance will be at least ten feet.
This buffer will also allow for snow storage during the winter to ensure the trail can be maintained and used throughout all seasons. At each intersection and driveway, the trail will transition closer to the roadway to pass in front of the stop bar. This is done to ensure motorists can see the trail user and react if there is someone in their path. This will cause the removal of several trees near the intersection. The added benefit from these removals will be increased visibility for the motorists sitting at the intersection.
Potential Construction Impacts
Silver Maples tend to have shallow root structures. Construction activities, even in protected areas, can and will take a toll on the health of trees. Trees that are located within the construction zone will need to be removed as they will be damaged during the project. The trees that are removed will be double ground and wood chips will be available to the public this spring at Terra Park.
Other trees will be in protected areas, but their overall health will need to be watched in future years. The contractor will do everything possible to maintain the health of any tree that is located outside of the construction zone.
Age and Quality of Existing Trees
The silver maples lining Pioneer Parkway are 35+ years old. That is relatively old for these types of trees (especially since they line a street). Although silver maples can live 50+ years, they do begin showing signs of stress as they age. Typically, these signs are loss of branches and hollowing out of the trunk. Many of these silver maples are showing those signs. As the trail was designed, the health of the trees was analyzed and decisions were made on the trail location based on the health of the tree. Several trees will be removed due to their health and the safety concerns for the public if they were to fall or lose a large branch.
Diversifying the Greenbelt
A healthy urban forest should have a vast diversity of trees. Areas that have only one or two species of trees are susceptible to insects or other diseases as it is easily passed from one tree to the next.
This has been true with ash trees (Emerald Ash Borer), and with maples. The Asian Long-Horned Beetle is an insect that is making its way west and damaging maples along the way. Pioneer Parkway will be highly susceptible to this insect if/when it makes it to Iowa. Diversifying the species and ages of the trees will ensure tree loss is minimized by having a variety. We will be replanting nearly 200 trees throughout the corridor, and the 10-15 different species will create the right mix to ensure a healthy urban forest corridor. This replanting project will occur after the trail construction is finished.
At this time, it is estimated September as the month trees will begin being replanted. The following list is not meant to be comprehensive but will provide the foundation of the trees that will be replanted along Pioneer Parkway after the trail project is complete. We will work with each property owner adjacent to the site to determine the best combination of trees and if any ornamental or evergreen trees will be included.
- Redmond Linden
- Silver Linden
- Horse Chestnut
- Kentucky Coffeetree (pod-less)
- Bald Cypress
- Regal Prince Oak
- American Hophornbeam
- Burr Oak
- Northern Red Oak
- Elm (varieties)
- Honey locust (thornless)
- Northern Catalpa
- London Plane Tree
- Black Gum
- Swamp White Oak
More information about the Pioneer Parkway Trail can be found by visiting the project page, www.cityofjohnston.com/925/Pioneer-Parkway-Trail.