Ақ қайын – Солтүстік Американың бір түрі

Species of birch

Betula populifolia, known as the gray (or grey) birch, is a deciduous tree in the family Betulaceae. It is native to eastern North America and is most commonly found in the northeast United States as well as southern Quebec, New Brunswick, and Nova Scotia. The tree is a pioneer species that is commonly found in sites following disturbance, such as fire or logging. Gray birches don't have as much economic value as other birch species but are still commonly used as ornamental trees.

Betula populifolia is a small tree that reaches heights of 20 to 30 feet (6 to 9 m) with a diameter at breast height (DBH) of 4 to 8 inches (10 to 20 cm). The tree is often found with multiple stems. The crown is pyramidal with somewhat drooping branches. The bark is smooth, a grayish white or chalky color with visible lenticels and black triangular patches located at the base of branches. Like other members of the Betula genus, leaves turn yellow in autumn. The flowers are wind pollinated catkins 2 to 3 inches (5 to 8 cm) long, the male catkins pendulous and the female catkins erect. The fruit, maturing in autumn, is composed of many tiny winged seeds packed between the catkin bracts.

Gray birch can be found in the northeast United States and small portions of Canada. It ranges from southeastern Quebec along the St. Lawrence River east to parts of New Brunswick and Nova Scotia, south through New England and upstate New York to Pennsylvania and New Jersey. The tree prefers well drained, loamy soils, but can also grow in dryer, gravelly soils. They thrive in sunlight since they are a shade intolerant species, but eventually give way to longer lived, more shade tolerant species. In regenerative stands, Betula populifolia are commonly found along other early successional species such as paper birch, quaking aspen, and bigtooth aspen (Populus grandidentata). This is due to birches in North America sharing a coevolutionary relationship with the borer, allowing it to develop resistance to the bug. Despite this, the borers can still damage the trees if they are weakened by other means. Between about 1930 and 1950, many gray birch trees, along with paper birch and yellow birch (Betula alleghaniensis), were weakened by birch dieback disease, which allowed for the bronze birch borer to attack and kill the trees.