Pinus contorta

Pinus contorta, with the common names lodgepole pine and shore pine, and also known as twisted pine, and contorta pine, is a common tree in western North America. It is common near the ocean shore and in dry montane forests to the subalpine, but is rare in lowland rain forests. Like all pines (member species of the genus Pinus), it is an evergreen conifer. There are four subspecies of Pinus contorta, and one of them is sometimes considered to have two varieties. The subspecies are sometimes treated at the rank of variety. Depending on subspecies, Pinus contorta grows as an evergreen shrub or tree. The shrub form is krummholz and is approximately 1 to 3 m (3 to 10 ft) high. The thin and narrow-crowned tree is 40 to 50 m (130 to 160 ft) high and can achieve up to 2 m (7 ft) in diameter at chest height. The murrayana subspecies is the tallest. The crown is rounded and the top of the tree is flattened. In dense forests, the tree has a slim, conical crown. The formation of twin trees is common in some populations in British Columbia. The elastic branches stand upright or overhang and are difficult to break. The branches are covered with short shoots that are easy to remove. The species name is contorta because of the twisted, bent pines found at coastal areas and the tree's twisted needles. Pinus contorta is occasionally known under several English names: black pine, scrub pine, and coast pine. P. contorta subsp. latifolia will hybridise with the closely related jack pine (Pinus banksiana). The egg-shaped growth buds are reddish-brown and between 20 and 30 mm (3⁄4 and 1 1⁄4 in) long. They are short pointed, slightly rotated, and very resinous. Spring growth starts in beginning of April and the annual growth is completed by early July. The dark and mostly shiny needles are pointed and 4 to 8 cm (1 1⁄2 to 3 in) long and 0.9 to 2 mm (0.04 to 0.08 in) wide. The needle edge is weak to clearly serrated. The needles are in pairs on short shoots and rotated about the shoots' longitudinal axes. In Alberta above 2,000 m (6,600 ft), 1 to 5 needles occur per short shoot. A population with a high proportion of three-needled short shoots occurs in the Yukon. Needles live an average of four to six years, with a maximum of 13 years. The cones are 3–7 centimetres (1–3 in) long. The cones have prickles on the scales. Many populations of the Rocky Mountain subspecies, P. contorta subsp. latifolia, have serotinous cones. This means that the cones are closed and must be exposed to high temperatures, such as from forest fires, in order to open and release their seeds. The variation in their serotiny has been correlated with wildfires and mountain pine beetle attacks. The cones of the coastal Pacific subspecies, P. contorta subsp. contorta, are typically non-serotinous, and those of the inland Pacific subspecies, P. contorta subsp. murrayana, are completely non-serotinous. Pinus contorta is a fire-dependent species, requiring wildfires to maintain healthy populations of diverse ages. The bark of the lodgepole pine is fairly thin, minimizing the tree's defense to fire; however, the heat of fire opens the cones to release the seeds. This allows the species to regenerate and maintain its place in the forest habitat. One plant community in which Pinus contorta is found is the closed-cone pine forest of coastal California.