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''Picea mariana'' (black spruce) is a North American species of spruce tree in the pine family. It is widespread across Canada, found in all 10 provinces and all 3 Arctic territories. Its range extends into northern parts of the United States: in Alaska, the Great Lakes region, and the Northeast. It is a frequent part of the biome known as taiga or boreal forest.〔Farjon, A. (1990). ''Pinaceae. Drawings and Descriptions of the Genera''. Koeltz Scientific Books ISBN 3-87429-298-3.〕〔Rushforth, K. (1987). ''Conifers''. Helm ISBN 0-7470-2801-X.〕〔Gymnosperm Database: (''Picea mariana'' )〕〔Flora of North America: (''Picea mariana'' )〕〔(Biota of North America Program 2014 state-level distribution map )〕 ==Description== ''Picea mariana'' is a slow-growing, small upright evergreen coniferous tree (rarely a shrub), having a straight trunk with little taper, a scruffy habit, and a narrow, pointed crown of short, compact, drooping branches with upturned tips. Through much of its range it averages 5–15 m tall with a trunk 15–50 cm diameter at maturity, though occasional specimens can reach 30 m tall and 60 cm diameter. The bark is thin, scaly, and grayish brown. The leaves are needle-like, 6–15 mm long, stiff, four-sided, dark bluish green on the upper sides, paler glaucous green below. The cones are the smallest of all of the spruces, 1.5–4 cm long and 1–2 cm broad, spindle-shaped to nearly round, dark purple ripening red-brown, produced in dense clusters in the upper crown, opening at maturity but persisting for several years.〔〔 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 firs, 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 ''Abies mariana, Picea brevifolia, Picea nigra''. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Picea mariana」の詳細全文を読む スポンサード リンク
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