Restoring the Oak-Hickory Forest at JK Black Oak

Volume 28 Issue 3, Summer 2023

by Sheila Ferguson and Gerco Hoogeweg

If you look at the oak-hickory forest at JK Black Oak Wildlife Sanctuary from the outside, it looks like a healthy forest. Once you walk into it, however, you see a very different picture. You’ll notice that there are very few tree saplings. Mature trees that die from disease or storm damage are not being replaced by young, growing trees. Look around at the floor of the forest and you see plenty of greenery, but much of it is invasive, which has little or no value to local wildlife.

What’s going on in the forest that the canopy and understory are not regenerating with native vegetation? The primary agent of destruction is the White-tailed Deer, in ways both direct and indirect.

Each spring, thousands of native tree seeds germinate and begin growing in the oak-hickory forest. Walk through the forest then, and you’ll see tree seedlings a few inches tall. However, by fall few seedlings remain, and by the next spring almost none are left. Although it is true that many of these seedlings wouldn’t make it to maturity due to other causes, deer browsing ensures that pretty much none do.

What the deer do not eat are nonnative trees, shrubs, and herbaceous plants, allowing them to flourish and displace native species. The deer further aid invasives by dispersing their seeds, which stick in their hooves or to their coats as they move about the forest. Deer also spread invasive seeds when they eat the fruit of invasive plants such as Multiflora Rose and Oriental Bittersweet and pass the seeds of these fruits in their droppings, spreading the plants to new areas. So deer represent a double whammy in the forest: they eat the native vegetation and help the invasives grow and spread.

Several years ago, the JK Black Oak Committee began discussing the idea of putting in some deer exclusion fences to see what would happen, but funding was an issue. In the fall of 2022, Loudoun Wildlife Conservancy received a generous grant from Microsoft in collaboration with the Society for Ecological Restoration for habitat restoration in the oak-hickory forest. This grant enabled us to install three deer exclusion fences and cages to protect an additional 100 tree seedlings in the forest.

Installation of the fences required a substantial amount of planning, including deciding where to locate the fences, choosing what materials should be used, creating a work plan, and having enough volunteers to support the work. Since we would all be learning as we went, we started with the smallest exclosure of 25 x 25 feet, with the goal of installing increasingly larger fences. This turned out to be a key decision that allowed us to work out some of the unknowns when using a deer-fencing kit. The 100-foot deer fence kit we ordered contained a fence roll that was indeed exactly 100 feet. This left no margin of error when situating the four corner posts. To ensure that we did not run out of fencing, the corner posts would be placed about 24 feet apart.

The first step in the installation of the poles was to hammer in the ground sleeves (in which the poles are inserted) using a mechanical post pounder. We thought the post pounder would make it easy. We were wrong. The ground was hard enough that it took two people and a lot of work to get each sleeve in. Another issue was not having enough tools and equipment (for example, ladder, hog ringer, and crimping tool). Having just one of each quickly resulted in volunteers waiting for a specific task to be completed before they could get going. We also learned that assembling the gate for the fence on the forest floor is not a good idea. Nuts and bolts are easy to lose and hard to find again.

Installing the second deer fence, measuring 50 x 50 feet, went more smoothly. We drilled pilot holes that made hammering the sleeves into the ground very easy. The gate was assembled in advance in a workshop, and having more tools and more volunteers made the installation process go faster. The fencing was cut into 50-foot segments, but even that required many hands, as the fencing was rather floppy and difficult to handle when lifting it into position.

The third deer fence presented a new challenge because of its size. With a total length of nearly 470 feet, this fence encloses 0.62 acres around a vernal pool and much of its catchment. Using a 500-foot deer fence kit as our starting point, we added wooden posts every 50 feet to provide additional structural strength. The first challenge was simply getting all the materials (11 ten-foot wooden posts, 33 metal posts and sleeves, concrete, and five 100-pound rolls of fencing) through the forest to the work site. It took several trips with everyone carrying materials to get all the materials there.

Spreading out the process over three monthly work days, we first installed the wood posts and then started on the pilot holes and sleeves for the metal posts. During the second work day, a team of volunteers installed three guide wires at different heights to connect the fence to. Another team was installing the post hooks for the fencing, and yet another team was cutting the fence roll to 50-foot pieces except for the last 100 feet. With 10 of us, we managed to hang up that 100-foot section of fence while carefully unrolling it in a vertical position and walking it into place. That gave us a total of 400 feet of fencing installed. On the third work day, we finished attaching the fencing, installed the remainder, and began clearing invasives inside the fence.

In coming years, we’ll be monitoring the deer exclosures to remove invasives and keep track of which native plants germinate and grow inside the fences.

Please note: To protect the environmentally sensitive habitat and rare species, JK Black Oak Wildlife Sanctuary is not open for general public access.