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 reaching several thousand years old. Trees have been in existence for 370 million years. It is estimated that there are around three trillion mature trees in the world.
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 it 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. Flowers and fruit may be present, but some trees, such as conifers, instead have pollen cones and seed cones. Palms, bananas, and bamboos also produce seeds, but 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...)
Banksia dentata, commonly known as the tropical banksia, is a species of tree in the genus Banksia. It occurs across northern Australia, southern New Guinea and the Aru Islands. Growing as a gnarled tree to 7 m (23 ft) high, it has large green leaves up to 22 cm (8.7 in) long with dentate (toothed) margins. The cylindrical yellow inflorescences (flower spikes), up to 13 cm (5.1 in) high, appear between November and May, attracting various species of honeyeaters, sunbirds, the sugar glider and a variety of insects. Flowers fall off the ageing spikes, which swell and develop follicles containing up to two viable seeds each.
Banksia dentata is one of four Banksia species collected by Sir Joseph Banks in 1770, and one of the four species published in 1782 as part of Carolus Linnaeus the Younger's original description of Banksia. Within the genus, it is classified in the series Salicinae, a group of species from Australia's eastern states. Genetic studies show it is a basal member within the group. Banksia dentata is found in tropical grassland known as savanna, associated with Pandanus and Melaleuca. It regenerates from bushfire by regrowing from its woody base, known as a lignotuber. (Full article...)Did you know? -
- ... that the Paget Marsh Nature Reserve in Bermuda has been called the "best surviving example of native cedar, palmetto (pictured), and mangrove forests", yet at one point the island lost 99% of its cedar trees?
- ... that a canopy walkway connects seven tree tops in Ghana's Kakum National Park?
- ... that the ivory curl tree can grow 30 m (100 ft) tall in its natural rainforest habitat?
- ... that the trumpet tree, a fast-growing tree native to the American tropics, is considered one of the hundred worst invasive alien species in the world?
- ... that the installation of an artificial Christmas tree in Brussels prompted an online petition against it with 25,000 signatures?
- ... that a white oak tree with a trunk circumference of over 26 feet (7.9 m) grew near Wolf Run until it was cut down in 1852?
- ... that the blue nuthatch (pictured) protects its corneas from falling debris when prospecting on trees by contracting the bare skin around its eyes – an adaptation apparently unique to the species?
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Pando (Latin for "I spread"), the world's largest tree, is a quaking aspen tree (Populus tremuloides) located in Central Utah in the Fishlake National Forest. A male clonal organism, Pando has an estimated 47,000 stems (ramets) that appear as individual trees, but are connected by a root system that spans 106 acres. Pando is the largest tree by weight and landmass and, is the largest known aspen clone. Pando was identified as a single living organism because each of its stems possesses identical genetic markers. The massive interconnected root system coordinates energy production, defense and regeneration across its expanse. Pando spans 0.63 miles by 0.43 miles of the southwestern edge of the Fishlake Basin in the Fremont River Ranger District of the Fishlake National Forest and lies 0.43 miles to the west of Fish Lake, the largest natural mountain freshwater lake in Utah. Pando is located at an elevation of 2,700 m (8,900 ft) above sea level.
Pando occupies approximately 106 acres (43 ha) and is estimated to weigh collectively 6,000 tonnes (6,000,000 kg), or 13.2 million pounds, making it the heaviest known organism. Systems of classification used to define large trees vary considerably, leading to some confusion about Pando's status. In contrast to the General Sherman Tree, the largest single stem tree, Pando is often characterized as an "organism" or "plant". Pando, however, is a tree and commonly known as the "Pando Tree". (Full article...)General images
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