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Jack Pine-Oak Community

A second community very much in evidence on this hike is the jack pine-oak forest. While the presence of jack pines and oaks characterize this community, a striking feature is geological rather than biological. Bald rock ridges and rock outcroppings are distinguishing features. Glaciers have scoured the ridges clean of any soil, and forest fires have consumed much of any soil that has tried to accumulate on these slow weathering granite ridges. As a result, the soils are very thin; from only 6 to 20 inches deep.

Stands of jack pine-oak communities tend to be among the youngest, being from 60-105 years old on average, as they develop in the wake of major forest fires. Jack pine is a tree of the pioneer stage of succession following significant forest fires. Jack pines are sun-loving trees. Their seedlings do not do well in shade. To ensure that its seeds will germinate only when conditions are right for the seedlings, saplings, and trees they will produce, this plant has adapted its cone to withstand forest fires. In fact, the cones not only withstand the fires, they need them if they are ever to see the light of day. The tightly shut cones need the heat of fires to melt the resin that would otherwise keep the seeds locked up forever. Without the disturbance of forest fires, this community type will gradually shift to black and white spruces, balsam firs, and paper birch. In other areas, maples and oaks may succeed, or red and white pines.

While jack pine is the dominant tree species, red maples, red oak, and black spruce are next in importance. They tend to occupy the under-story, waiting to take over when the jack pine fall to the ravages of old age and are unable to reproduce without the aid of fire. Bush honeysuckle, juneberry, and beaked hazel are important tall shrubs in this community, while late sweet blueberry, wintergreen, and velvet-leaf blueberry are the major low shrubs. The presence of these later shrubs indicates relatively open, dry conditions. On the ground, false lily-of-the-valley, large leaf northern aster, and mosses are common.

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