Improving Forest Health
We're using prescribed fire to restore Ponders Tract.
For well over 100 years, people have been taught that forest fires are destructive, causing great harm to the trees and animals that call the woodlands home. However, when properly managed, fire can be a force for good. In fact, some plants and animals require fire to reproduce.
The Nature Conservancy and the Delaware Forest Service are using prescribed fire at the Conservancy’s Ponders Tract Preserve in order to keep invasive species in check and natural areas from becoming overgrown. Much of the 908-acres that make up the Ponders Tract were planted as a pine plantation in the years before it was acquired by the Conservancy in 2004. Prescribe fire helps thin the loblolly pines that grow unnaturally thick here and restores a more natural mixture of tree species that provide a wider variety of food and habitat for native wildlife.
Delaware Chapter Land Steward Natasha Whetzel tells us about forest restoration at Ponders Tract and how our efforts are paying off.
nature.org: What have you observed about how the forest has responded to the land management practices of the past two years?
Natasha Whetzel: The site, being a former loblolly pine plantation, has many pine trees that out-compete and dominate most of the other tree species in the forest, especially oaks. Our state forester at Ponders, Erich Burkentine, and I spent a morning at the burn site at the end of December 2017 scoping out the effects of the burn and timber harvest.
I noticed some of the shaded immature oak trees were producing what are called epicormic shoots, which sprouts from the bole [trunk] of the tree. Epicormic shoots are commonly the result of two things, increased light levels or fire, and are common in oak species post-disturbance. It makes sense the shaded immature oaks produced epicormic sprouts, as they saw increased light levels and fire in the same year. I noted the mature oak trees with ample sunlight did not produce epicormic sprouts. Although epicormic sprouting is indicative of disturbance or stress, it is not harmful to the tree but is undesirable because it is a sign of an unhealthier tree and lowers timber value.
nature.org: How do we strengthen the oaks and reduce epicormic branches?
Natasha Whetzel: We need to increase the trees’ vigor by allowing them more room to expand their crowns and access sunlight.
nature.org: And how do we do that?
Natasha Whetzel: By thinning, and although thinning may cause epicormic branching in the short term by exposing tree boles to sunlight, it is the most efficient management technique to promote the expansion of crowns on oak trees.
nature.org: What other changes have you observed?
Natasha Whetzel: Erich and I have noticed a number of red oak species with large round black spots. At first, we were unsure what they were but Erich soon realized it was the stress-related fungal disease known as Hypoxylon canker. It is a weak ascomycete fungus that affects growth and can lead to the death of a tree. The fungus usually appears as gray splotches, but in this case appeared black due to the char received from the prescribed fire earlier in the year. This fungus strictly colonizes stressed shade trees and is a secondary disease, meaning the tree needs a primary factor such as drought or physical damage to infect the already decaying or dying tree. In this case, we believe the spring 2016 timber harvest caused the infection of Hypoxylon canker and the prescribed fire weakened the infected trees more.
nature.org: What sort of preexisting stresses were the trees dealing with?
Natasha Whetzel: There were many factors that played into the unhealthiness of these trees. First and foremost, the immature oak trees were stressed from lack of sunlight due to the overtopping dense pines outcompeting them. To help remedy this problem, in Spring of 2016, the site received a selective thinning of pines to promote more sunlight to the mid and understory species. During the harvest process trees were stressed from machine operations and the environmental changes from the treatment. Following the thinning treatment, a prescribed fire was implemented to lower duff [the layer of decaying forest litter consisting of organics such as needles and leaves] and litter layers, reduce basal area [the cross-sectional area of all tree trunks in a stand, measured at breast height] and kill pine sapling regeneration [immature trees]. The prescribed fire succeeded in meeting those objectives and although may have stressed the infected oaks even more, we noted numerous new oak seedlings sprouting on the forest floor.
Still, the best technique for restoring the health of these trees is by continuing timber harvest and prescribed fire operations so oak species may grow large, tall and healthy. When we have healthy oak trees, we will remedy the Hypoxylon canker and oaks will not be stressed by prescribed fire but instead produce acorns able of germination on an open forest floor.