Curtis, John T.
White Pine
Curtis: The Vegetation of Wisconsin, Madison, 1959, pp204-205.
University of Wisconsin
Original Date

LIFE-HISTORIES OF DOMINANTS White Pine (Pinus strobus) If there is one tree which can be used to exemplify the northern forests, it is the white pine. It is the only species which is present in appreciable quantities in all segments of the full moisture gradient from wet bogs to xeric sand plains. It is the largest and the longest lived tree of the region. when the vacation-bound traveler from the hot and steamy cities of the south sees his first white pine, he knows that he is entering the "north woods." This innate and almost totally unrecognized ecological skill at judging climate by vegetation is probably a vestigial holdover from the days when man was more intimately connected to his landscape than he now believes himself to be. In any case, the judgment is a sound one, since white pine is truly a sign of pleasant summer days and cool nights. Its corollary, deep snow and bittere winter cold, is less well appreciated.

Like the oaks, the pines are similar to each other in most of their life-history characteristics; there are just enough differences in environmental requirements to bring about significant ecological separations. All of the pines are wind-pollinated; all produce wind-disseminated, winged seeds; all germinate best on exposed mineral soil; all grow rapidly; none is tolerant of shade; and all exert similar influences on the soil.

Of the three species in Wisconsin, white pine is the most exacting with respect to the moisture and nutrient supply required for optimum development. It grows best on deep loams or sandy loams which have an appreciable quantity of available bases, but it can survive as stunted specimens on any soil in the area or, indeed on no soil at all, as it does in the cracks on sandstone cliffs. The seeds of white pine are shed in autumn in large numbers after a two-year ripening period, with intervals of 3 to 5 years between bumper crops. Germination occurs in the spring on moist surfaces. Invasion of open sites can occur but the presence of a nurse crop of aspen, birch, or other pioneer species promotes the best regeneration. The young trees grow rapidly and may reach 8 to 10 inches d.b.h.[diameter breast height] at forth years, with a height of 60 feet or more. Ultimate heights over 200 feet are common, and ages of five hundred years or more are easily possible.

The statement is frequently seen in forestry publications that white pine avoids all types of organic soils. This is definitely not true in Wisconsin, where 37 per cent of the stands of bog conifers in the P.E.I. study which were dominated by tamarack swamps in stream valleys in the Driftless Area are frequently invaded by white pine. However, no stands were observed in which white pine was more than a minor and accidental component in forests on mineral soils which were subject to frequent or prolonged inundation by flood waters. It is not known whether the trees of organic swamps represent distinct ecotypes or not.