In forestry circles, monocultures don’t get high marks. Most planted forests have just one kind of tree, and because of this they are often looked down upon as biological Levittowns: boring forests that are of little interest to other species.
Sometimes, however, nature does a pretty good imitation of a plantation, even if she does a poor job at keeping the trees in rows.
Pitch pine forests, like those that make up the New Jersey Pine Barrens, are a good example of a natural monoculture. The New Jersey forest is roughly 30 by 80 miles and has been dominated by pitch pine since the retreat of the last glacier.
How can one species dominate for so long? In this case, fire, and pitch pine’s adaptations to fire, have kept the forest in a state of ecological inertia. Continuous cycles of burning and re-sprouting prevent the progression of what would normally be considered a pioneer forest to one with more typical climax species.
Even when all of the needles on a pitch pine are burned, the crown can recover and be almost back to normal in just a few years. If the leader is killed, a new one may grow, and if most of the tree is killed, new sprouts will emerge from the trunk or the base of the trunk. The ability to sprout from the trunk is common in hardwoods but rare in a conifer. Dormant buds buried deep in the thick bark of a pitch pine come to life after a fire or other injury to the crown.
Like the more boreal jack pine, another “fire pine,” a percentage of a pitch pine’s cones are serotinous, which is another way of saying that they remain closed until the heat of a fire melts the resinous glue that holds the scales of the cone together. Only then are the seeds released. Pitch pines seem to spend their lives preparing for fire: they begin to produce cones when very young, and they hang on to them year after year. A tree crown with hoards of blackened cones is not pretty, but the abundant seed supply serves the tree well when bare, newly-burned land cools.
In the absence of fire, the monoculture breaks down. Most of Cape Cod and much of Long Island were once pitch pine forests, but because of development and the exclusion of fire, oaks, red maple, and other species have lately joined pine in the canopy.
By no means is pitch pine confined to pure stands. Throughout its range – from southern New England south to northern Georgia – small patches can be found among other trees on the rocky, dry, wet, or shallow soils that other species find challenging.
At present, uses for pitch pine are limited, but in early Colonial times it was an important source of pitch, tar, rosin, and turpentine, all vital to keeping sailing ships afloat. The tree has an unusually high concentration of these compounds, which were also important as exports. Sheila Connor, in her book New England Natives, writes that in 1628, the residents of Plymouth requested that “men skyfull in making of pitch” be sent from England. Indeed, this was a skill, involving the slow, controlled combustion of pitch pine wood for two weeks, with the pitch collected in ditches that circled the pitch kiln. Resin was gathered by cutting a channel in the trunk of a pitch pine with a hatchet and channeling it to a container.
In the early 1800s, a booming bog iron industry in New Jersey Pine Barrens used pitch pine wood to fire the smelters and forges. Each of the many furnaces used a thousand acres of pines each year; at the same time, pitch pine charcoal was being shipped to New York City by the schoonerful. The ability to recover from human abuses is another pitch pine trait. It can regrow from the stump and from seeds that do not depend upon heat to be released. Depleted soil is a plus – it helps keep other species out of the picture.
These survival mechanisms do take a toll on appearance. Pure, natural stands that have been burned repeatedly tend to consist of short-bodied, misshapen trees. Their irregular profiles include heavy, lopsided lower branches, and many years’ worth of aged cones blacken the crown.
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