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Picea mariana, the black spruce, is a North American species of spruce tree in the Pinaceae. It is widespread across Canada, found in all 10 provinces and all 3 territories. It is the official tree of Newfoundland and Labrador and is that province's most abundant tree. Its range extends into northern parts of the United States: in Alaska, the Great Lakes region, and the upper Northeast. It is a frequent part of the biome known as taiga or boreal forest..K. Rushforth (1987). 074702801X, Helm. 074702801X
The Latin specific epithet mariana means "of the Virgin Mary".
Natural hybridization occurs regularly with the closely related Picea rubens (red spruce) and very rarely with Picea glauca (white spruce). It differs from P. glauca in having a dense cover of small hairs on the bark of young branch tips, an often darker reddish-brown bark, shorter needles, smaller and rounder cones, and a preference for wetter lowland areas. Numerous differences in details of its needle and pollen morphology also exist but require careful microscopic examination to detect. From true Fir, such as Abies balsamea (balsam fir), it differs in having pendulous cones, persistent woody leaf-bases, and four-angled needles, arranged all round the shoots.
Due to the large difference between heartwood and sapwood moisture content, it is easy to distinguish these two wood characteristics in ultrasound images, which are widely used as a nondestructive technique to assess the internal condition of the tree and avoid useless log breakdown. Older taxonomic synonyms include A. mariana, P. brevifolia, or P. nigra.
In the southern portion of its range it is found primarily on wet organic soils, but farther north its abundance on uplands increases. In the Great Lakes region it is most abundant in peat bogs and swamps, also on transitional sites between peatlands and uplands. In these areas it is rare on uplands, except in isolated areas of northern Minnesota and the Upper Peninsula of Michigan.
Most stands are even-aged due to frequent fire intervals in black spruce forests. It commonly grows in pure stands on organic soils and in mixed stands on mineral soils. It is tolerant of nutrient-poor soils and is commonly found on poorly drained acidic peatlands. It is considered a climax species over most of its range; however, some ecologists question whether black spruce forests truly attain climax because fires usually occur at 50 to 150 year intervals, while "stable" conditions may not be attained for several hundred years. The frequent fire return interval, a natural fire ecology, perpetuates numerous successional communities. Throughout Boreal ecosystem North America, Betula papyrifera (paper birch) and Populus tremuloides (quaking aspen) are successional hardwoods that frequently invade burns in black spruce. Black spruce typically seeds in promptly after fire and with the continued absence of fire eventually dominates the hardwoods.
Black spruce is a Pioneer species that invades the sphagnum mat in filled-lake bogs, though often preceded slightly by Larix laricina (tamarack). Black spruce frequently out-competes shade-intolerant tamarack in the course of bog succession. However, as the peat soil is gradually elevated by the accumulation of organic matter and the fertility of the site improves, balsam fir and northern white cedar ( Thuja occidentalis) eventually replace black spruce and tamarack. On drier sites following fires, black spruce can take over stands of faster growing jack pine ( Pinus banksiana) by virtue of its ability to grow in partially shaded conditions which inhibit pine seedlings. (1974). 9780124242555, Academic Press. ISBN 9780124242555 But black spruce seedlings are intolerant to the low light and low moisture conditions under mature spruce stands. Balsam fir and northern white cedar, both more understory-tolerant species with deeper Taproot, survive and eventually succeed the spruce in the absence of fire.
The spruce budworm, a moth larva, causes defoliation which kills trees if it occurs several years in a row, though black spruce is less susceptible than white spruce or balsam fir. Trees most at risk are those growing along with balsam fir and white spruce.
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