The Trees Portal
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...)
Zombia antillarum, commonly known as the zombie palm, is a species of palm tree and the only member of the genus Zombia. It is endemic to the island of Hispaniola (both the Dominican Republic and Haiti) in the Greater Antilles. Usually found in dry, hilly areas of northern and southern Haiti and the northwest of the Dominican Republic, Z. antillarum is a relatively short fan palm with clustered stems and a very distinctive appearance caused by its persistent spiny leaf sheaths. Threatened by habitat destruction in Haiti, Z. antillarum is a popular ornamental species due to its distinctive appearance, low maintenance requirements and salt tolerance. (Full article...)
Did you know? -
- ... that fossil leaves almost identical to those of the Australian rainforest tree Orites excelsus (pictured) have been found in New Zealand?
- ... that more than 8000 trees were planted in Backmuir Wood to celebrate the 2000 millennium?
- ... that the name of the newly defined genus of macadamia-like trees, Lasjia, is derived from the initials of Lawrence Alexander Sidney Johnson?
- ... that at St Athan, a wild fig tree grew out of the cement of the East Orchard chapel walls?
- ... that in the churchyard of St Mary and St Peter's Church in Wilmington, East Sussex, there is a 1,600-year-old, 23-foot (7 m) wide yew tree?
- ... that Christopher Werner made a lifelike South Carolina Palmetto tree out of iron, copper, and brass?
- ... that seed from an endangered Chrysophyllum imperiale tree planted in Royal Botanic Gardens, Sydney in 1868 by Prince Alfred has been sent to its native Brazil to aid in recovering the species there?
Selected article -
Eucalyptus fraxinoides, commonly known as the white ash or white mountain ash, is a medium-sized to tall tree of mountain country and is endemic to south eastern Australia. It has rough, compacted greyish bark on the lower trunk, smooth white bark with scribbles above, lance-shaped adult leaves, flower buds in groups of between seven and eleven, white flowers and barrel-shaped or urn-shaped fruit. (Full article...)
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