Science and conservation
Penn Swamp: the fence that changed the next forest
Documented history and research · Sources compared
A decade-long cedar experiment compared regeneration with and without deer protection. Its most consequential result concerned which young trees survived above browsing height, not simply whether seedlings appeared.
The experiment separated two possible obstacles
George Zimmermann and Kristin Mylecraine studied a harvested part of Penn Swamp using fenced and unfenced ground. Both areas received treatments with no logging debris, ordinary debris and doubled debris. Permanent plots were measured from 1990 through 1995 and again in 2000, allowing an early restoration response to be checked over a longer interval. Zimmermann and Mylecraine, Penn Swamp: Ten Years of Change (2005).
Deer mattered more than the debris treatment
Their 2005 proceedings paper reports inadequate cedar regeneration, shrub dominance and few cedars reaching the next height class outside protection. One debris-treatment difference was statistically detectable but, in the authors’ judgment, probably not biologically important. The comparison warns against giving every significant test result the same ecological weight. Zimmermann and Mylecraine, Penn Swamp: Ten Years of Change (2005).
The result fits a difficult seedling stage
The Forest Service’s silvics account explains that cedar establishment depends on both light and position above the water table. Very wet microsites can drown seedlings, while exposed hummocks can dry out. Dense shade also limits survival. Excluding deer addresses one obstacle; it does not remove these other conditions. USDA Silvics of North America, Atlantic White-Cedar.
A later NJDEP restoration description includes deer fencing alongside planting and control of competing vegetation at Burlington County sites. The combination reflects the practical lesson that a surviving seedling must pass several tests. A successful planting count on its first day cannot establish what kind of forest will occupy the site a decade later. NJDEP Atlantic White Cedar restoration project.
Sources and research limits
- Zimmermann and Mylecraine, Penn Swamp: Ten Years of Change (2005) — Proceedings PDF, printed pp. 65–72: abstract, experimental design and result discussion checked.
- USDA Silvics of North America, Atlantic White-Cedar — Regeneration, light and water-table sections read.
- NJDEP Atlantic White Cedar restoration project — Full description of treatments in Byrne and Wharton forests read.
The paper’s harvest dates differ slightly between abstract and methods; the period is given broadly. This is one experiment’s evidence, not a blanket recommendation to clearcut cedar wetlands. Later project descriptions do not establish measured long-term success by themselves.