Portal:Trees
Trees
In botany, a tree is a perennial plant with an elongated stem, or trunk, supporting branches and leaves in most species. 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 taxonomic group but include a variety of plant species that have independently evolved a trunk and branches as a way to tower above other plants to compete for sunlight. 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 just over 3 trillion mature trees in the world.
A tree typically has many secondary branches supported clear of the ground by the trunk. This trunk 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 parts 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.
Selected article
A forest, also referred to as a wood or the woods and less often as a "wold" (or "weald"), "holt", or "frith" (or "firth"), is an area with a high density of trees. There are many definitions of "forest" based on various criteria. These plant communities cover approximately 9.4% of the Earth's surface (or 30% of total land area), though they once covered much more (about 50% of total land area), in many different regions and function as habitats for organisms, hydrologic flow modulators, and soil conservers, constituting one of the most important aspects of the biosphere. Although forests are classified primarily by trees, the concept of a forest ecosystem includes additional species (such as smaller plants, fungi, bacteria, and animals) as well as physical and chemical processes such as energy flow and nutrient cycling.
Selected biography
John Krubsack (1858-1941) was a banker and naturalist from Embarrass, Wisconsin. He conceived, planted and shaped living trees to create the first known grown chair. He started his chair in 1903 and harvested 11 years later in 1914.
In addition to banking, Krubsack was a prominent naturalist who farmed, made cheese, and landscaped his property long before these were common practice.[clarification needed] His house was the first in his region to have running water. He also was skilled at piecing together furniture from found branches. He’d scour the local river flats with a yardstick and a saw, looking for just the right shaped piece of blue beech, a hardwood tree with a smooth, wavy bark and a beautiful blue color when varnished. John took his youngest son, Hugo, on these weekend wood-hunting excursions, and it was during one of his trips that the idea first came to him to grow his own chair. Read more...
In the news
Selected images
Alleé of London plane trees (Platanus × acerifolia) in garden
Buds, leaves and reproductive structures of white fir (Abies alba)
Selling firewood at a market
Trees in art: Weeping Willow, Claude Monet, 1918
Conifers in the Swabian alps
Buttress roots of the kapok tree (Ceiba pentandra)
European larch (Larix decidua), a coniferous tree which is also deciduous
Recently stripped cork oak (Quercus suber)
A young red pine (Pinus resinosa) with spread of roots visible, as a result of soil erosion
Form, leaves and reproductive structures of queen sago (Cycas circinalis)
Dormant Magnolia bud
Lepidodendron, an extinct lycophyte tree
Sugar maple (Acer saccharum) tapped to collect sap for maple syrup
Common ash (Fraxinus excelsior), a deciduous broad-leaved (angiosperm) tree
People trees, by Pooktre
Yggdrasil, the World Ash of Norse mythology
Tall herbaceous monocotyledonous plants such as banana lack secondary growth, but are trees under the broadest definition.
Diagram of secondary growth in a eudicot or coniferous tree showing idealised vertical and horizontal sections. A new layer of wood is added in each growing season, thickening the stem, existing branches and roots.
Latex collecting from a rubber tree (Hevea brasiliensis)
Roof trusses made from softwood
The General Sherman Tree, thought to be the world's largest by volume
Buds, leaves, flowers and fruit of oak (Quercus robur)
Palms and cycads as they might have appeared in the middle Tertiary
Northern beech (Fagus sylvatica) trunk in autumn
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Did you know?
- ... that the Top 10 New Species of the past year include a 40 foot (12 m) tall tree (pictured), a crustacean that looks like a skeleton, a protist that acts like a sponge, and a fungus named after the King of the Netherlands?
- ... that the Pass Christian Light was deactivated in part because neighboring property owners refused to trim their trees?
- ... that Cossinia trifoliata trees endemic to New Caledonia have become vulnerable to extinction, according to the International Union for Conservation of Nature's 1998 assessment?
- ... that the Hanlon Expressway is named after Felix Hanlon, who helped cut the first tree to inaugurate Guelph, Ontario?
- ... that British architect Richard Feilden was killed by a falling tree whilst creating a woodland memorial for his recently deceased father?
- ... that according to tradition the Church of the Holy Archangels, Rogoz was built from two huge elm trees?
- ... that the oak tree under which Goethe allegedly wrote Faust's Walpurgis Night scene stood inside Buchenwald concentration camp and was sketched by French Volontaires de la Liberté member and camp inmate Léon Delarbre?
