Updated: Feb 5, 2021
The following article was written by Guy Dunkle, Forester with the Foundation for Sustainable Forests and was originally included in the Summer/Fall 2020 edition of the "Tracking Invasive Species with Pennsylvania iMapInvasives" newsletter.
Dense understory of natives and multiflora rose. Credit: Guy Dunkle, FSF
Forestland managers have a few prominent tools that are used in efforts to build vibrant, resilient ecosystems. Logging is the tool that catches everybody's eye, generally because it's messy, with treetops scattered around. However, to improve the health of forests, land managers use this tool because it restores the forest to a more natural condition.
Logging allows for patches of light to access the forest floor, thus encouraging new growth of understory and mid-story plants. While it can be controversial and look unsightly in the short term, logging has direct benefits when implemented correctly.
In recent years, another tool has seen as increase in popularity in Pennsylvania; the use of herbicide. As invasive plant species spread, public and private landowners have ramped up efforts to address this concern.
Suppressing invasive species with careful use of herbicides is a cost-effective and time-saving way to control large infestations of invasive plants compared to other methods. At the Foundation for Sustainable Forests (FSF), forest managers remove invasive species to restore native forests. The FSF is a small, not-for-profit land trust operating in the northern and western portions of Pennsylvania and adjacent regions of New York and Ohio. With a mission centered around harmonic utilization of forests, the Foundation has a mandate to actively manage and steward the lands that we protect.
In addition to stewardship of the forestland we own, the FSF has partnered with a handful of local organizations to assist them in the care of their forests. These partners include the City of Erie, the U.S. Army Corps of Engineers (USACE), and the Presque Isle Audubon Society.
Our forestry process focuses on developing multiple age classes of trees, improving native species diversity, maintaining a "full" understory with dense plant cover, and enhancing the vigor of trees. Over time, this management style builds resilience in the forest system - healthy vigorous trees and plants of diverse species and age are better able to bounce back from the disturbances of extreme weather, introduced pests, and invasive species.
FSF property will full understory. Credit: Guy Dunkle, FSF
So far in 2020, we have embarked on invasive plant control projects covering 60 acres of forestland. These have involved partner properties such as the USACE's Union City Dam in Erie County, Presque Isle Audubon's Laura Olsen Memorial Sanctuary in Crawford County, and a property owned by FSF located near Platea in Erie County. (Note: More information about projects to control invasive species at these properties is available by logging into iMapInvasives and using the Filter Records tool to search for data observed by Guy Dunkle.)
At the Platea Forest, the most problematic invasive plant is multiflora rose (Rosa multiflora). In addition, there are populations of garlic mustard (Alliaria petiolata) and common privet (Ligustrum vulgare) near an abandoned farmyard site.
Our control work this year was the continuation of efforts begun in the summer of 2012, when we embarked on a large-scale habitat improvement project through a partnership with Ducks Unlimited and the National Fish and Wildlife Foundation. At that time, we utilized a tractor-mounted herbicide sprayer to control dense thickets of multiflora rose and release native plants.
Fast forward to the year 2020, and now much of the area treated in 2012 has had native plant regeneration. There are thickets of tree seedlings and saplings, and only scattered multiflora rose bushes are still present. However, in several areas, the native plants are being out-competed by several invasive plants that were able to reestablish themselves.
Ecological Field Services crew working at Platea Forest. Credit: Guy Dunkle, FSF
To combat this issue, we contracted with Ecological Field Services, based in the nearby town of Waterford, to handle this round of herbicide application. The crew was composed of five hard-working folks toting backpack sprayers through the forest. As they wrapped up work at the Platea Forest, they drove an ATV-mounted sprayer into the densest patch of multiflora rose bushes and were able to thoroughly treat what had appeared to be an impenetrable bramble.
Our expectation is not to eliminate invasive plants from the forest; that seems to be an unattainable goal. Rather, our objective is to reduce invasive species to a small enough presence that native components and processes are able to function effectively.
Oak seedlings at USACE Union City Dam. Credit: Guy Dunkle, FSF
Another very important consideration for us is maintaining the fullness of the forest understory. As the saying goes, "Nature abhors a vacuum", and forests with open understories and very few plants growing at ground level seem to be ripe for invasion by non-natives. Therefore, we pair our control efforts with strategic thinnings of the forest canopy (aka, logging).
By releasing light onto the ground, we are able to bolster the health and density of wildflowers, tree seedlings, shrubs, and other desirable ground cover. As the understory fills with desirable plants, there is less space available for non-natives to occupy. Then, through selective herbicide applications, we reduce the invasive species to a small, low-impact component of the forest. Thankfully, this process also reduces the impact of deer browse, spreading the damage across many plants in a dense, lush understory.
In pursuit of a vibrant, resilient forest ecosystem, managers have a variety of tools available. Implementing these tools successfully requires observation, thoughtfulness, and intimacy with the forest.