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Drunken Trees
Drunken trees, tilted trees, or a drunken forest, is a stand of trees rotated from their normal vertical alignment. This most commonly occurs in northern subarctic taiga forests of black spruce (''Picea mariana'') under which discontinuous permafrost or ice wedges have melted, causing trees to tilt at various angles. Tilted trees may also be caused by frost heaving, and subsequent palsa development, hummocks, earthflows, forested active rock glaciers, landslides, or earthquakes. In stands of spruce trees of equal age that germinated in the permafrost active layer after a fire, tilting begins when the trees are 50 to 100 years old, suggesting that surface heaving from new permafrost aggradation can also create drunken forests. Permafrost Permafrost, which is soil (or rock) that remains below 0 °C for at least two consecutive years, forms a solid matrix in soil which can extend to a depth of hundreds of meters. The permafrost prevents trees from developing deep root syst ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Floss Silk Tree
''Ceiba speciosa'', the floss silk tree (formerly ''Chorisia speciosa''), is a species of deciduous tree that is native to the tropical and subtropical forests of South America. It has several local common names, such as ''palo borracho'' (in Spanish literally "drunken stick"), or '' árbol del puente'', ''samu'ũ'' (in Guarani), or ''paineira'' (in Brazilian Portuguese). In Bolivia, it is called toborochi, meaning "tree of refuge" or "sheltering tree". In the USA it often is called the silk floss tree. It belongs to the same family as the baobab; the species ''Bombax ceiba''; and other kapok trees. Another tree of the same genus, '' Ceiba chodatii'', is often referred to by the same common names. Description The natural habitat of the floss silk tree is in the northeast of Argentina, east of Bolivia, Paraguay, Uruguay, and southern Brazil. It is resistant to drought and moderate cold. It grows fast in spurts when water is abundant, and sometimes reaches more than in height. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
University Of Alaska Fairbanks
The University of Alaska Fairbanks (UAF or Alaska) is a public land-grant research university in College, Alaska, a suburb of Fairbanks. It is the flagship campus of the University of Alaska system. UAF was established in 1917 and opened for classes in 1922. Originally named the Alaska Agricultural College and School of Mines, it became the University of Alaska in 1935. Fairbanks-based programs became the University of Alaska Fairbanks in 1975. UAF is classified among "R2: Doctoral Universities – High research activity." It is home to several major research units, including the Agricultural and Forestry Experiment Station; the Geophysical Institute, which operates the Poker Flat Research Range and several other scientific centers; the Alaska Center for Energy and Power; the International Arctic Research Center; the Institute of Arctic Biology; the Institute of Marine Science; and the Institute of Northern Engineering. Located just 200 miles (320 km) south of the Ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Little Ice Age
The Little Ice Age (LIA) was a period of regional cooling, particularly pronounced in the North Atlantic region. It was not a true ice age of global extent. The term was introduced into scientific literature by François E. Matthes in 1939. Matthes described glaciers in the Sierra Nevada of California that he believed could not have survived the hypsithermal; his usage of "Little Ice Age" has been superseded by "Neoglaciation". The period has been conventionally defined as extending from the 16th to the 19th centuries, (noted in Grove 2004:4). but some experts prefer an alternative timespan from about 1300 to about 1850. The NASA Earth Observatory notes three particularly cold intervals. One began about 1650, another about 1770, and the last in 1850, all of which were separated by intervals of slight warming. The Intergovernmental Panel on Climate Change Third Assessment Report considered that the timing and the areas affected by the Little Ice Age suggested largely independent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dendrochronology
Dendrochronology (or tree-ring dating) is the scientific method of dating tree rings (also called growth rings) to the exact year they were formed. As well as dating them, this can give data for dendroclimatology, the study of climate and atmospheric conditions during different periods in history from wood. Dendrochronology derives from Ancient Greek (), meaning "tree", (), meaning "time", and (), "the study of". Dendrochronology is useful for determining the precise age of samples, especially those that are too recent for radiocarbon dating, which always produces a range rather than an exact date. However, for a precise date of the death of the tree a full sample to the edge is needed, which most trimmed timber will not provide. It also gives data on the timing of events and rates of change in the environment (most prominently climate) and also in wood found in archaeology or works of art and architecture, such as old panel paintings. It is also used as a check in radiocar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reaction Wood
Reaction wood in a woody plant is wood that forms in place of normal wood as a response to gravity, where the cambial cells are oriented other than vertically. It is typically found on branches and leaning stems. It is an example of mechanical acclimation in trees. Progressive bending and cracking would occur in parts of the tree undergoing predominantly tensile or compressive stresses were it not for the localised production of reaction wood, which differs from ordinary wood in its mechanical properties. Reaction wood may be laid down in wider than normal annual increments, so that the cross section is often asymmetric or elliptical. The structure of cells and vessels is also different, resulting in additional strength. The effect of reaction wood is to help maintain the angle of the bent or leaning part by resisting further downward bending or failure. There are two different types of reaction wood, which represent two different approaches to the same problem by woody plants: * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gravitropism
Gravitropism (also known as geotropism) is a coordinated process of differential growth by a plant in response to gravity pulling on it. It also occurs in fungi. Gravity can be either "artificial gravity" or natural gravity. It is a general feature of all higher and many lower plants as well as other organisms. Charles Darwin was one of the first to scientifically document that roots show ''positive gravitropism'' and stems show ''negative gravitropism''. That is, roots grow in the direction of gravitational pull (i.e., downward) and stems grow in the opposite direction (i.e., upwards). This behavior can be easily demonstrated with any potted plant. When laid onto its side, the growing parts of the stem begin to display negative gravitropism, growing (biologists say, turning; see tropism) upwards. Herbaceous (non-woody) stems are capable of a degree of actual bending, but most of the redirected movement occurs as a consequence of root or stem growth outside. The mechanism is bas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermokarst
Thermokarst is a type of terrain characterised by very irregular surfaces of marshy hollows and small hummocks formed as ice-rich permafrost thaws. The land surface type occurs in Arctic areas, and on a smaller scale in mountainous areas such as the Himalayas and the Swiss Alps. These pitted surfaces resemble clusters of small lakes formed by dissolution of limestone in some karst areas, which is how they came to have "''karst''" attached to their name, even though no limestone is actually present. Small domes that form on the surface due to frost heaving with the onset of winter are only temporary features. They collapse during the following summer thaw, leaving a small surface depression. Some ice lenses grow and form larger surface hummocks ("pingos") which can last for many years, and sometimes become covered with grasses and sedges, until they begin to thaw. These domed surfaces eventually collapse – either annually or after longer periods – and form depressions which bec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deforestation
Deforestation or forest clearance is the removal of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. The most concentrated deforestation occurs in tropical rainforests. About 31% of Earth's land surface is covered by forests at present. This is one-third less than the forest cover before the expansion of agriculture, a half of that loss occurring in the last century. Between 15 million to 18 million hectares of forest, an area the size of Bangladesh, are destroyed every year. On average 2,400 trees are cut down each minute. The Food and Agriculture Organization of the United Nations defines deforestation as the conversion of forest to other land uses (regardless of whether it is human-induced). "Deforestation" and "forest area net change" are not the same: the latter is the sum of all forest losses (deforestation) and all forest gains (forest expansion) in a gi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Melting Point
The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at a standard pressure such as 1 atmosphere or 100 kPa. When considered as the temperature of the reverse change from liquid to solid, it is referred to as the freezing point or crystallization point. Because of the ability of substances to supercool, the freezing point can easily appear to be below its actual value. When the "characteristic freezing point" of a substance is determined, in fact, the actual methodology is almost always "the principle of observing the disappearance rather than the formation of ice, that is, the melting point." Examples For most substances, melting and freezing points are approximately equal. For example, the melting point ''and'' freezing point of mercury is . How ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Taproot
A taproot is a large, central, and dominant root from which other roots sprout laterally. Typically a taproot is somewhat straight and very thick, is tapering in shape, and grows directly downward. In some plants, such as the carrot, the taproot is a storage organ so well developed that it has been cultivated as a vegetable. The taproot system contrasts with the adventitious or fibrous root system of plants with many branched roots, but many plants that grow a taproot during germination go on to develop branching root structures, although some that rely on the main root for storage may retain the dominant taproot for centuries, for example ''Welwitschia''.Taproot also store nutrition. Plants with taproots are often vegetables. Description Dicots, one of the two divisions of flowering plants (angiosperms), start with a taproot, which is one main root forming from the enlarging radicle of the seed. The tap root can be persistent throughout the life of the plant but is most oft ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Black Spruce
''Picea mariana'', the black spruce, is a North American species of spruce tree in the pine family. It is widespread across Canada, found in all 10 provinces and all 3 territories. It is the official tree of the province of Newfoundland and Labrador and is that province's most numerous tree. The range of the black spruce extends into northern parts of the United States: in Alaska, the Great Lakes region, and the upper Northeast. It is a frequent part of the biome known as taiga or boreal forest.. The Latin specific epithet ''mariana'' means “of the Virgin Mary”. Description ''P. mariana'' is a slow-growing, small upright evergreen coniferous tree (rarely a shrub), having a straight trunk with little taper, a scruffy habit, and a narrow, pointed crown of short, compact, drooping branches with upturned tips. Through much of its range it averages tall with a trunk diameter at maturity, though occasional specimens can reach tall and diameter. The bark is thin, scaly, and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Denali National Park And Preserve
Denali National Park and Preserve, formerly known as Mount McKinley National Park, is an American national park and preserve located in Interior Alaska, centered on Denali, the highest mountain in North America. The park and contiguous preserve encompass which is larger than the state of New Hampshire. On December 2, 1980, Denali Wilderness was established within the park. Denali's landscape is a mix of forest at the lowest elevations, including deciduous taiga, with tundra at middle elevations, and glaciers, snow, and bare rock at the highest elevations. The longest glacier is the Kahiltna Glacier. Wintertime activities include dog sledding, cross-country skiing, and snowmobiling. The park received 594,660 recreational visitors in 2018. History Prehistory and protohistory Human habitation in the Denali Region extends to more than 11,000 years before the present, with documented sites just outside park boundaries dated to more than 8,000 years before the present. However, rel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
