by Dan Schneider and Peter Pautler
Confined, for the most part, to habitats shaped by cold, < dry, windy climates, coniferous trees dominate the enormous northern boreal forest, a region that blankets 11 percent of the earth’s surface. North of Ontario’s Great Lakes, this vast coniferous forest occupies 75 million hectares, nearly half of the land mass of the province. Pines, hemlocks and eastern white-cedars thrive in the mixed-forest region, which extends from Lake Superior west and east to the Manitoba and Quebec borders, respectively, and south to the deciduous forest zone along Lakes Ontario and Erie.
All of Ontario’s 12 coniferous trees and three shrubs retain their narrow needle- or scale-like leaves beyond one growing season, except the tamarack (see “The deciduous coniferous tree,” opposite page). Red pine needles may remain on the tree for three years; the needles of balsam fir may last up to seven years. Because conifers do not grow new leaves each spring, these species are able to conserve energy and scarce resources. Moreover, photosynthesis can begin with the first sign of spring and continue well into autumn, even at temperatures as low as –7 C.
Conifers have evolved so as to maximize a brief growing season and withstand harsh winters. To prevent desiccation, the narrow or flat leaves of coniferous species expose minimal surface area to the dry Arctic winds. A thick, transparent cuticle envelops the needles, preventing moisture loss year-round.
Coniferous trees have descended from an ancient lineage of plants – the gymnosperms (the term derives from the Greek word meaning “naked seeds”). These trees are cone bearers and most grow two types of cones. Male cones release copious amounts of pollen, which winds carry to the exposed ovules on the scales of the larger, female cones. After fertilization the seeds mature as the scales grow tightly together, forming the familiar looking cones. In spring the scales loosen and, with a gentle breeze, the winged seeds are released and twirl to a suitable site for germination. For some species, such as the jack pine, only the intense heat from a fire frees the seeds.
Use these tips to identify coniferous trees: Pines and larches have needles in clusters of two, three, five or more. Firs and hemlocks have flat, single needles, sometimes with a slender leaf-stalk joining the main needle to the branch, and sometimes without one. The needles of spruces have edges. Junipers and cedars have leaves composed of overlapping scales.
Dan Schneider and Peter Pautler are resource interpreters with the Grand River Conservation Authority.