Bogs and burning woods: small variations in elevation create the strange habitats of New Jersey's pine barrens

Natural History, May, 2003 by Robert H. Mohlenbrock

At frequent intervals between 135 million and five million years ago, the sea covered what is now the coastal plain of New Jersey, depositing days, silts, sands, and gravels. The sandy soil covering the plain today is acidic and low in fertility; it also retains little water, creating arid conditions that give rise to fires. Most plants cannot survive in such a hostile environment, but the ones that do make up a distinctive forest called the pine barrens.

Extending as far inland as fifty miles, the coastal plain comprises two sections. The wide, outer plain gradually rises from the New Jersey coast to a crest of low hills. Beyond that, a narrower but more fertile inner plain slopes down to the bank of the Delaware River. The pine barrens comprises more than 2,000 square miles of the outer coastal plain, about a fourth of the state. Much of it is uninhabited, but because of the acidity of the soil, some zones have been cleared for raising commercial crops of blueberries and cranberries. Here and there towns and villages have also been established. In 1978, concerned that development would obliterate the natural environment, the U.S. Congress designated the area the New Jersey Pinelands, the first so-called national reserve.

The pine barrens terrain is relatively fiat, never rising more than 200 feet above sea level. But minor differences in elevation create four identifiable habitats. Highest are two kinds of dry forests, one dominated by pitch pine and one dominated by oaks. Bogs (the third habitat) and cedar swamps (the fourth) occur in the lowlands. All four natural communities appear here and there throughout the national reserve, but large continuous acreages of the pine barrens are also administered by the state: Wharton State Forest, Brendan T. Byrne (formerly Lebanon) State Forest, and Belleplain State Forest.

Historically, fire has helped maintain the dry forests, striking at least once every twenty to forty years (large fires are becoming less frequent, however, because of increased control). The characteristic species are fire tolerant, usually surviving because they have extensive underground root or rhizome systems. In one twenty-square-mile zone of pitch-pine forest, the fires have burned every ten to twenty years, and the pitch pines and associated species grow only four to ten feet tall. Such stands are known as pine plains or dwarf pine forests. East of Brendan T. Byrne State Forest, along State Route 72 just west of its junction with County Road 539, the trees are only a few feet tall. Standing among them, the average adult can feel like a giant.

About seven and a half miles north of the same junction is Webb's Mill Bog, one of my favorite bogs in the pine barrens. It is the most accessible because it is surrounded by a metal walkway. Bogs develop in low depressions where as much as two feet of standing water collects. Atlantic white cedars scattered amid the other vegetation remain stunted as long as the water is deep, growing no more than four feet tall. As a bog fills in with dead vegetation, including the highly acidic cedar leaves, however, the water becomes increasingly acidic, discouraging the growth of some plant species. At the same time, the area starts to dry out, and me cedars begin to grow straight up as high as seventy-five feet, shading (and thereby stunting or killing) many of the small plants beneath them. The habitat is thus transformed into a cedar swamp.

The pine barrens of New Jersey is the northernmost range of 109 southern plant species. Among them are turkey beard, golden-crest, and yellow asphodel. Botanists have also discovered fourteen species of plants more common farther north that reach their southernmost limit in the pine barrens. Rarest and most unexpected of those are broom crowberry, a wiry shrub with crowded, quarter-inch-long leaves and black berries, and curly grass, a fern that has small curly leaves that look like immature grass.

HABITATS

Pitch-pine forest Made up primarily of pitch pine or a mixture of pitch pine and shortleaf pine, this kind of forest often includes a few broadleaved trees, particularly blackjack oak, post oak, and chinquapin oak. Several low-growing shrubs, such as lowbush blueberry and black huckleberry, are common. The few non-woody species include little bluestem, wintergreen, Virginia tephrosia, wild indigo, tall oatgrass, cowwheat, low frost weed, turkey beard, and bracken fern.

Oak forest Scarlet oak, white oak, black oak, and chestnut oak prevail in the canopy; pitch pine is a secondary species. Other trees are blackjack oak, post oak, and sassafras. The shrub layer includes lowbush blueberry, black huckleberry, dangleberry, staggerbush, inkberry and sheep laurel. The forest floor is home to the same species that grow in pitch-pine forests.

Dwarf-pine forest Pitch pine is the main tree, but blackjack oak, bear oak, and chestnut oak are also common. Shrubs include broom crowberry, mountain laurel, sheep laurel, sand myrtle, golden heather, black huckleberry, and lowbush blueberry. Other species include trailing arbutus, bearberry, wintergreen, inkberry, sweet fern, flowering pixie moss, and cowwheat.