Forest Habitats and Deer Deterrent Fencing
When and why do we fence? To manage state game lands for forest habitat quality and diversity to meet the needs of the many wildlife species in Pennsylvania, we conduct periodic harvesting activities using sound silviculture – the science of managing forests over time to achieve desired tree species composition and habitat structure. Because nearly 88 percent of the total acres of state game lands are forested, there may be no more important habitat management practice than silviculture.
Browsing by white-tailed deer is a significant factor preventing successful forest regeneration of desired tree species. Deer exclosures have been used widely and have proven effective in increasing desirable plant species abundance and reducing regeneration failures caused by deer browsing. Although fences are not effective at excluding all deer, they can greatly increase regeneration success when used under the right conditions and at the right time.
Use of deer exclosures is considered in forest habitat management when deer browsing is, or is expected to be a problem. Fencing ensures forest stands can successfully reproduce and promotes plant species diversity. Deer fences are used in a range of situations to establish, protect, or increase regeneration. For example, fences are used in forests that are stocked fully and have already received a silvicultural treatment or are scheduled for a silvicultural treatment designed to regenerate the stand. They also are utilized in a fully stocked stand or an understocked stand that has experienced some natural mortality or natural disaster (gypsy moth defoliation or ice damage). Finally, they also are used in forest habitats that need rehabilitation from past failed forest management activities.
The Game Commission prioritizes deer fencing needs. In all cases, it must be determined that deer browsing pressure will impact the forest habitat's ability to regenerate. First priority is given to recently-harvested areas where regeneration is not progressing to satisfaction. Second priority is given to areas scheduled to receive multiple intermediate harvests over a period of about 10 years to achieve successful regeneration. The fence usually remains in place until after the final harvest. Third priority is areas in need of rehabilitation. Lowest priority is given to fully stocked mature forests that are to be "pre-fenced." These areas are fenced before any silvicultural work, because of poor site quality or absence of desirable or sufficient regeneration. In all cases, the silvicultural system is based on habitat objectives, forest composition, and site limitations.
When we remove fences and how we decide. Throughout the progression of a given forest habitat management project, foresters conduct periodic inventories of conditions within the project area. The first assessment takes place during the first or second growing season after a silvicultural treatment. Regeneration is assessed to determine the abundance, diversity, and competitive position of desired plants and tree seedlings. It ensures the forestland ultimately meets the demands of it managers and fulfills its in-tended goal to provide habitat for scores of species.
These sites are revisited about five years later for a second assessment. On some occasions, regeneration is favorable and the fence may be scheduled for removal. More of-ten, additional treatments are necessary to eliminate competing vegetation or to release regenerating plants to full sunlight conditions (in the case of a shelterwood sequence). These additional treatments may include herbicide applications, prescribed fire, or additional timber harvest. Inventories are continued after these treatments about every other year until desired species composition is achieved and most regeneration is beyond the reach of deer.
The standard for successful regeneration inside a fence is for a six-foot-radius plot to have at least two desirable seedlings that are more than five feet tall and in position to compete with other vegetation. To ensure statistical reliability, four plots are conducted for the first 10 acres of the project area, and an additional plot is added for every additional five acres. For example, on an 80-acre area, we would sample 18 plots. Seventy percent of these plots must achieve the regeneration standard before we'd consider removing the fence. From installation to removal, a fence may remain from eight to 12 years; 10 years is the average. In some cases, where extensive rehabilitation efforts have been undertaken, fences may remain even longer.
In recent years, as deer numbers have been reduced and stabilized, some fences have been scheduled for removal sooner than they otherwise would have. This is a result of reduced deer browsing pressure outside the fence and our conclusion that regeneration would not be negatively affected if the fence was removed.
Variables that dictate how forest habitat will be managed largely depend on what's available to manage, limiting factors that will influence forest health, and corrective actions available to foresters to remedy what ails a forest. Deer deterrent fencing helps protect and promote growth of plant and tree seedlings; it is a valuable tool in forest management. Although fencing represents a temporary inconvenience for hunters, it almost always provides a better forest for future hunting in shorter time than an unfenced stand.
- The Game Commission first used deer-deterrent fencing in forest habitat treatments in the late 1990s. In 2008, the Pennsylvania Game Commission began to contract for the removal of fences, as well as using volunteer and conservation groups to help remove some fences. From 2008 through 2010, fence removal equaled or exceeded new installations.
- Deterrent fencing has never exceeded more than one percent of the total forested acreage on State Game Lands.
- Hunters are permitted – even encouraged – to hunt within fenced areas. All fences are constructed with gates to provide hunters access.
By Dave Gustafson
Pennsylvania Game Commission