Oak trees in Southern U.S. cities are natural urban air filters

Researchers at the University of North Texas have found that two oak tree species, post oak and live oak, that are widespread across the U.S. South remove black carbon from the urban atmosphere. The findings may offer a natural ...

Threatened beetles benefit from forest thinning

Wood-living beetles that use oak trees are a species-rich and threatened animal group in modern forestry and agriculture in southern Sweden. New research from the University of Gothenburg shows that management with conservation ...

Dehesa health starts from the ground up

Holm oak decline threatens dehesa sustainability. Though the pseudofungus oomycete Phytophthora cinnamomiserĂ­a is thought to be the main cause of holm oak decline, climate conditions have been shown to influence it, as well. ...

Floodplain forests under threat

A team from the Institute of Forest Sciences at the University of Freiburg shows that the extraction of ground water for industry and households is increasingly damaging floodplain forests in Europe given the increasing intensity ...

New tree ring analysis method may open insights to past climate

Satellite imagery of earth's vegetation, measurements of carbon dioxide in the air and computer models all help scientists understand how climate is affecting carbon dynamics and the world's forests. But these technologies ...

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Oak

An oak is a tree or shrub in the genus Quercus ( /ˈkwɜrkəs/; Latin "oak tree"), of which about 600 species exist. "Oak" may also appear in the names of species in related genera, notably Lithocarpus. The genus is native to the northern hemisphere, and includes deciduous and evergreen species extending from cold latitudes to tropical Asia and the Americas.

Oaks have spirally arranged leaves, with a lobed margin in many species; some have serrated leaves or entire leaves with a smooth margin. The flowers are catkins, produced in spring. The fruit is a nut called an acorn, borne in a cup-like structure known as a cupule; each acorn contains one seed (rarely two or three) and takes 6–18 months to mature, depending on species. The live oaks are distinguished for being evergreen, but are not actually a distinct group and instead are dispersed across the genus.

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