Ecological Succession

Viable seeds are safely stored throughout the soil profile of peat or sphagnum moss. Seeds delay germination until flooding subsides, fires pass over the land, or a forest is cut over. While seeds germinate in mineral soil if moisture is adequate, they also germinate in the crevices of old logs once buried in the litter and now exposed to the air. Pine needles and autumn's fallen broadleaf foliage are improbable germination beds.

Silvically, a temporary or early pioneer species in ecological succession precludes expansion of the acreage of white-cedar stands. More shade-tolerant species growing more rapidly take over the land, in spite of the vast acreages of peaty and other satisfactory seedbeds within the species' range.

While white-cedar competes reasonably well with broadleaf encroachers like gray birch, species of greater shade tolerance, such as blackgum and sweetbay, form the climax forest on swampy sites. Hardwood trees that get an early start in white-cedar bogs increase in vigor with time. As the health of the white-cedars declines and the canopy thins because of this competition (at about age 60), species composition abruptly changes. Dense shrub growth sometimes overtops the young conifers; in that event, the white-cedar stems may be nearly as slender as pencils.

White-cedar trees do not readily self-prune. While lower branches die early, they persist—especially in closed stands—for many years. The rot-resistance of the durable wood likely contributes to this characteristic.

As many as 1700 stems per acre occur in stands 60 years old. Volumes before maturity of 30,000 board feet per acre have been reported. This is a high-volume stand for almost any site east of the northern Rocky Mountains.

Height growth remains steady until mid-age, then gradually declines until cessation at maturity. Trees mature on better sites at 80 years of age. At that time, long, straight boles with little taper provide quality lumber. Diameter growth continues well beyond the culmination of height growth.

Species' Antagonists

White-cedar stands near the coast are killed by salt water blown in by storm tides. On the other hand, nearby stands of other species, especially hardwoods killed by salt spray, may be replaced by white-cedar. When that occurs, the water-loving conifer should be free of competition until past middle age. Then, broadleaf species like bay magnolia and holly intrude.

Black bears roaming these remote and inaccessible (to man) woods and birds flying over them affect growth of young and mid-aged white-cedar trees. Both beasts and birds carry seeds of the greenbriar, Smilax, in their bellies. Passed in droppings, the germinating seeds produce clumps of vines in initial encroachment. Great masses of the thorny vine weigh down tree tops and break trunks, deforming the boles. Browsing by white-tailed deer in winter, seedling nibbling by cottontail rabbits, and seedling girdling by meadow mice also tell of the abundance of wildlife.

Not only is white-cedar wood durable due to its natural impregnation with pesticidal chemicals, living trees are notably free of fungi and insect attacks. One pathogen, Gymnosporangium ellisii, causes a spherical swelling of the bole or of a branch. A growth of foliage, called a witches' broom, then arises from dormant buds beneath the bark and close by the canker.

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