A common motif in comic books presents characters as having two distinct personalities. Think of mild-mannered Clark Kent and the high flying Superman, or inept Peter Parker and the amazing Spider Man. Such dual personalities can be found in the natural world as well, and one of the more common examples regularly occurs on the Addison County shores of Lake Champlain in Vermont.
White cedar trees (Thuja occidentalis), also known as arbor vitae, dominate in very wet or very dry conditions, but seldom in between. Typically, white cedars thrive in lowland swamps or along the banks of rivers. However around Lake Champlains shoreline in Addison County they are frequently found atop cliffs. Here shallow soils and incessant winds create a dry setting where the trees form a thick dark forest. Within several hundred feet of the cliff top, the cedars typically give way to other upland community types like hardwood forests.
There are commonalities between the two very different environments: nutrient rich soils and stressful growing conditions. Cliffs hosting white cedars are invariably comprised of limestone or dolomite, two calcium-based rocks. Cedar-dominated wet- lands also occur in association with calcium-rich bedrock. Just as growing bodies use the calcium in milk for strong bones and teeth, plants use calcium to strengthen cell walls, and plant communities growing on limestone derived soils frequently contain species unusual in more nutrient poor areas. Dolomite limestone adds magnesium as well as calcium. Stressful growing conditions reduce competition from faster growing species like white pine.
Along the Champlain cliffs in Addison County stress comes from wind, shallow soil, and limited water. In the swamps stress comes from the constant inundation of roots, limiting oxygen supply. The harsh conditions, coupled with numerous cavities created by woodpeckers and fallen limbs, produce twisted and deformed trees. Many topple in strong storms, strewn about like matchsticks.
It is unwise to guess the age of a tree from its size, and white cedars demonstrate why. They can attain great ages without achieving great stature.
Naturalists Elizabeth Thompson and Eric Sorenson describe cedar trees over 300 years old in their guide to the natural communities of Vermont. Some trees on cliff tops with hollowed trunks are over 200 years old yet less than 15 feet tall. In similar communities around Lake Ontario, thousand year old cedars have been documented. Meanwhile, white pines growing in association with the cedars can tower above them despite being much younger.