Forest succession occurs in all wooded areas, whether it is completely wild or strictly managed. Frick Park is no exception! Forest succession is the process by which a forest ecosystem rebuilds itself after a disturbance that leaves open areas of ground to be filled with trees and other plants. A disturbance can be anything from a forest fire to a timber harvest.
Forest succession occurs in four stages. The first of these is the grass and forbs stage. At this point, only small plants cover the ground, such as ragweed and crabgrass (n.d. Forest Succession and Wildlife). In Frick Park, you can walk around and find Queen Anne’s Lace and Goldenrod (iNaturalist, 2021)! These two plants are among those that are seen in early successional ecosystems (n.d. Forest Succession and Wildlife).
The second stage consists of shrubs and saplings. Due to a large amount of available sunlight and soil, many trees and shrubs are able to begin life in the budding forest (Hammonds, 2016). These “pioneer” species include locust, pine, and black cherry trees (n.d. Forest Succession and Wildlife). Look for them while you take a quick hike up to Clayton Hill!
Once the wooded area matures 5-10 more years, it enters the pole stage. The saplings have grown to be about as thick as a baseball or softball. This stage is also known as “stem exclusion” because the adolescent trees have grown enough to block sunlight from reaching the ground (Hammonds, 2016). Most new saplings will not receive enough light to develop. In Frick Park, the tulip, ash, and red maple trees are indicative of a forest that is in the pole stage (n.d. Forest Succession and Wildlife). In the past decade, ash trees in Frick Park and around Pittsburgh have been negatively affected by the Emerald Ash Borer. You will see some of the park’s ash trees wrapped with white tape. These trees have been selected as trees that will be closely monitored and cared for, so that some of the ash trees in the area will survive the ash borer. If you would like to read more about this conservation effort, click here!
After another 20 or 30 years, the forest moves into a mature state. By this time, the trees have developed and grown to tower over the forest floor. A mature forest will also have dead trees and decaying plants (n.d. Forest Succession and Wildlife). These also are important because some animals like to live in hollowed-out tree trunks. From time to time, small disturbances will open up space in the canopy where new trees can grow (Hammonds, 2016). Many trees that dominate mature forests can be found in Frick Park. These include oaks, hickories, maples, hemlock, and beeches (n.d. Forest Succession and Wildlife). Many of these species can be seen throughout the park!
You probably have noticed that there are not just trees and shrubs in Frick Park from one stage of forest succession. Healthy forest ecosystems need plant and tree species from all of the successional stages (Hammonds, 2016). Animals need diverse sources of food, and places to construct shelters in their habitat. For example, deer need shrubby bushes from the shrub and saplings stage to hide behind, but they also like eating the acorns of oak trees from the mature forest stage (n.d. Forest Succession and Wildlife). A good mix of tree and plant species allows for many different animal species to inhabit the area.
You can go out and observe some of the animals that prefer different successional stages! I have researched Frick Park’s page on iNaturalist to identify some species that you might see while walking around the park’s trails. If you get an account, you can post observations of these animals as well!
The chipping sparrow prefers ecosystems that display traits of the grass and forbs stage, and the shrub and sapling stage (n.d. Forest Succession and Wildlife). They like to hunt for food in fields. Cottontail rabbits also depend on plant species from these two stages (n.d. Forest Succession and Wildlife).
Northern Slimy Salamanders like the larger trees in the pole stage and mature forest (n.d. Forest Succession and Wildlife). They can be found scampering on the forest floor and on some tree trunks. Red-eyed Vireos prefer the pole and mature stages as well (n.d. Forest Succession and Wildlife).
The Gray Squirrel and Red-Tailed Hawk both prefer to live in mature forest ecosystems (n.d. Forest Succession and Wildlife). You will see the squirrels gathering acorns and scaling trees, and the hawks soaring far above them!
The Pittsburgh Parks Conservancy actively promotes the biodiversity of tree and plant varieties. The ash tree conservation project is one example. Another is the use of deer exclosures in Frick Park. If you have ever walked up past the top of Clayton Hill, you will see a fenced-in area with small shrubs and saplings growing inside of it. The fence protects the new trees from deer; they would eat all of the new growth if they had access to it. By offering these plants an opportunity to grow this patch of the forest will have more plants of different successional stages, making it more attractive to different animal species.
See this video from the PA Game Commission to learn more about forest succession in Pennsylvania. Have fun observing forest succession in Frick Park!
Matthew Beck - Pittsburgh Parks Conservancy Intern
Hammonds, T., 2016. Forest Succession and Management - Cornell Small Farms. [online] Cornell Small Farms Program. Available at: <https://smallfarms.cornell.edu/2016/04/forest-succession-and-management/> [Accessed 28 April 2021].
iNaturalist. 2021. Frick Park, Pittsburgh, PA, US. [online] Available at: <https://www.inaturalist.org/places/frick-park> [Accessed 28 April 2021].
n.d. Forest Succession and Wildlife. [ebook] Available at: <https://www.envirothonpa.org/documents/ForestSuccession.pdf> [Accessed 28 April 2021].