Prescribed Burn above Tin Can Hollow

Burn Area
Approximately 25 acres of the Susquehannock State Forest between Green Timber and Tin Can hollows, starting about 100 feet from the Susquehannock Trail System, was set ablaze under carefully controlled conditions by Forest District 15 on May 12, 2011.

The purpose of the burn is to promote the regeneration of red, white, and chestnut oak trees by setting back the development of competing woody species in this case, striped maple and mountain laurel. This is made possible by the location of the buds on the root collars of the different tree and shrub species. Most maple and laurel buds are located just far enough above ground that the fire will kill them. Oaks, on the other hand, have many buds located on the root collar a short distance below ground, where they are protected from fire.

Oak trees are extremely valuable for both timber and wildlife food. Deer, turkeys, squirrels, blue jays, and several other wildlife species feed heavily on acorns when they are available. On the other hand, striped maple is a small, non-timber tree that rarely exceeds four inches in diameter, and produces only typical small winged maple seeds which are less useful as wildlife food. Mountain Laurel, the state flower, is an attractive understory shrub, but its seeds are of only minor value to wildlife.

Observations of areas where wildfires have burned in recent years generally reveal more oak regeneration than is found in areas that haven't burned for decades. That has led foresters to conclude that the current abundance of oak timber in Pennsylvania was brought about by the great forest fires of the late 1800's and early 1900's. An acorn, by virtue of its size, moisture content and food supply, can support its seedling on a hot dry sun-baked seedbed resulting from a fire, much longer than the smaller seeds of most other species. Little seeds quickly dry out and die under those conditions.

But when an area of forest hasn't burned for decades, the forest floor is covered by a moist layer of rotting leaves, duff, and humus. The acorns can still sprout, and oak seedlings can still grow well in the duff, but in that moister environment, numerous other species with much smaller seeds will sprout prolifically. The seedlings of those species will survive in large numbers and are able to grow faster than the oaks, effectively choking out most of the oak seedlings. A prescribed burn can kill most of the competing seedlings and saplings, and give the young oak roots a chance to produce new sprouts with less competition for sunlight and moisture.

No one wants to see the conflagrations of the past repeated, but foresters and wildlife managers are becoming concerned about the declining population of oak trees. Small-scale, tightly controlled "prescribed burns" are an effort to bring back the oaks in small areas.

Prescribed burning works best when the oak seedlings have been growing in the understory for several years, gradually enlarging their root systems. As soon as the competing vegetation is killed by the fire, and sunlight warms the ground, the oaks will send up vigorous, fast-growing new shoots fed by their large root systems. The striped maple and mountain laurel will recover more slowly. It will take them a few years to reestablish themselves, and by then the oaks will have such a head start in height growth that the striped maple and laurel can never catch up. Within a few years, the oaks will have grown taller than the striped maple and mountain laurel are capable of growing. From then on, the main canopy of the forest belongs to the oaks, and the striped maple and mountain laurel will take their places in the understory. Mountain laurel's greatest benefit to wildlife is that it provides low protective cover from predators and weather.

Other tree species will seed in, and a scattered few of them may even join the oaks in the main canopy. This is desirable from the standpoint of forest diversity. Hickories, for example, are also timber trees that have large seeds and provide food for wildlife. Black locust, on the other hand, is of minor importance for timber and of limited value as a wildlife-food producer, but would be a worthy addition to the site for another reasonsoil fertility. The roots of black locust support bacteria that add nitrogen to the soil, while its leaves provide only light shade. The presence of black locust usually helps other plants grow better. That effect has been shown in faster height growth in trees, and more rapid establishment of ground vegetation that provides protective cover for wildlife.

One important tree species that will be rare, if present at all on this site, is black cherry. Although black cherry timber is just as valuable as oak timber, and cherry also provides nutritious food for wildlife, that species does not grow well on the dry ridge tops and south- and west-facing slopes favorable to the oaks. Cherry prefers moister, cooler sites, and its regeneration does not benefit from prescribed burning. The cherry sites along the Susquehannock Trail System are found mostly in the northern parts of the trail system. In the southern areas of the STS, cherry is mostly restricted to coves and the cooler, damper north- and east-facing slopes.

Hikers are encouraged to walk into the burned area in the years to come, and observe whether the effort to convert this site to mostly oaks has been successful.