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Portal:Trees

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The Trees Portal

Common ash (Fraxinus excelsior), a deciduous broad-leaved (angiosperm) tree

In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are usable as lumber or plants above a specified height. In wider definitions, the taller palms, tree ferns, bananas, and bamboos are also trees.

Trees are not a monophyletic taxonomic group but consist of a wide variety of plant species that have independently evolved a trunk and branches as a way to tower above other plants to compete for sunlight. The majority of tree species are angiosperms or hardwoods; of the rest, many are gymnosperms or softwoods. Trees tend to be long-lived, some trees reaching several thousand years old. Trees evolved around 370 million years ago, and it is estimated that there are around three trillion mature trees in the world currently.

A tree typically has many secondary branches supported clear of the ground by the trunk, which typically contains woody tissue for strength, and vascular tissue to carry materials from one part of the tree to another. For most trees the trunk is surrounded by a layer of bark which serves as a protective barrier. Below the ground, the roots branch and spread out widely; they serve to anchor the tree and extract moisture and nutrients from the soil. Above ground, the branches divide into smaller branches and shoots. The shoots typically bear leaves, which capture light energy and convert it into sugars by photosynthesis, providing the food for the tree's growth and development.

Trees usually reproduce using seeds. Flowering plants have their seeds inside fruits, while conifers carry their seeds in cones, and tree ferns produce spores instead.

Trees play a significant role in reducing erosion and moderating the climate. They remove carbon dioxide from the atmosphere and store large quantities of carbon in their tissues. Trees and forests provide a habitat for many species of animals and plants. Tropical rainforests are among the most biodiverse habitats in the world. Trees provide shade and shelter, timber for construction, fuel for cooking and heating, and fruit for food as well as having many other uses. In much of the world, forests are shrinking as trees are cleared to increase the amount of land available for agriculture. Because of their longevity and usefulness, trees have always been revered, with sacred groves in various cultures, and they play a role in many of the world's mythologies. (Full article...)

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Pi de les tres branques in 2012

Pi de les tres branques (Catalan: [ˈpi ðə ləs ˈtɾɛz ˈβɾaŋkəs]; meaning "the three-branched pine") is a dead pine tree located in the countryside near the town of Berga in north-central Catalonia, Spain. It has long been regarded by some Catalan nationalists as representing the unity of the three "Catalan Countries" and is the site of regular political-cultural gatherings.

The tree has been dead since 1915 and is in poor structural condition, due in part to politically-motivated vandalism, but there is a very similar living tree a short distance away known as Pi jove de les tres branques ("the young three-branched pine"), which is regarded as its successor. Both are protected as "monumental trees" by the Catalan Generalitat. (Full article...)

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Saalfeld Easter egg tree with 9200 eggs, taken March 24, 2009

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Utah juniper (Juniperus osteosperma) in Nevada, United States

Junipers are coniferous trees and shrubs in the genus Juniperus (/ˈnɪpərəs/ joo-NIP-ər-əs) of the cypress family Cupressaceae. Depending on the taxonomy, between 50 and 67 species of junipers are widely distributed throughout the Northern Hemisphere as far south as tropical Africa, including the Arctic, parts of Asia, and Central America. The highest-known juniper forest occurs at an altitude of 4,900 metres (16,100 ft) in southeastern Tibet and the northern Himalayas, creating one of the highest tree lines on earth. (Full article...)

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