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Information about Evergreen

This article is about plant types. For other uses, see Evergreen (disambiguation).


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A Silver Fir shoot showing three successive years of retained leaves
In botany, an evergreen plant is a plant that has leaves all year round. This contrasts with deciduous plants, which completely lose all their foliage for part of the year.

Leaf persistence in evergreen plants may vary from only a few months (with new leaves constantly being grown and old ones shed), up to a maximum of 45 years in Great Basin Bristlecone Pine Pinus longaeva [1]. However, very few species show leaf persistence of over 5 years.

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A Southern live oak in winter
One additional special case exists in Welwitschia, an African gymnosperm plant which produces only two leaves, which grow continuously throughout the plant's life but gradually wear away at the apex, giving about 20–40 years' persistence of leaf tissue.

Reasons for being evergreen or deciduous

Deciduous trees shed their leaves for a reason--usually as an adaptation to a cold season or a dry season, when carrying leaves may become a liability. Most tropical rainforest plants are evergreens, replacing their leaves gradually throughout the year as the leaves age and fall, whereas species growing in seasonally arid climates may be either evergreen or deciduous. Most warm temperate climate plants are also evergreen. In cool temperate climates, fewer plants are evergreen, with a predominance of conifers, as few evergreen broadleaf plants can tolerate severe cold below about -30 °C.

In areas where there is a reason for being deciduous (e.g. a cold season or dry season), being evergreen is usually an adaptation to low nutrient levels. Deciduous trees lose nutrients whenever they lose their leaves, and they must replenish these nutrients from the soil to build new leaves. When few nutrients are available, evergreen plants have an advantage. In warmer areas, species such as some pines and cypresses grow on poor soils and disturbed ground. In Rhododendron, a genus with many broadleaf evergreens, several species grow in mature forests but are usually found on highly acidic soil where the nutrients are less available to plants. In taiga or boreal forests, it is too cold for the organic matter in the soil to decay rapidly, so the nutrients in the soil are less easily available to plants, thus favouring evergreens.

In temperate climates, evergreens can reinforce their own survival; evergreen leaf and needle litter has a higher carbon-nitrogen ratio than deciduous leaf litter, contributing to a higher soil acidity and lower soil nitrogen content. These conditions favour the growth of more evergreens and make it more difficult for deciduous plants to persist. In addition, the shelter provided by existing evergreen plants can make it easier for other evergreen plants to survive cold and/or drought.[2][3][4]

References

1. ^ Ewers, F. W. & Schmid, R. (1981). Longevity of needle fascicles of Pinus longaeva (Bristlecone Pine) and other North American pines. Oecologia 51: 107-115.
2. ^ Joshua, W. (1995). The advantages of being evergreen. Trends in Ecology & Evolution 10 (10): 402-407.
3. ^ Matyssek, R. (1986) Carbon, water and nitrogen relations in evergreen and deciduous conifers. Tree Physiology 2: 177–187.
4. ^ Sobrado, M. A. (1991) Cost-Benefit Relationships in Deciduous and Evergreen Leaves of Tropical Dry Forest Species. Functional Ecology 5 (5): 608-616.

See also



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The primary meaning of evergreen refers to evergreen plants. Other meanings are derived from the botanical sense.

Places

Evergreen is the name of several places:

United States of America
  • Evergreen, Alabama
  • Evergreen, Colorado

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Botany is the scientific study of plant life. As a branch of biology, it is also called plant science(s), phytology, or plant biology. Botany covers a wide range of scientific disciplines that study plants, algae, and fungi including: structure, growth,
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leaf is an above-ground plant organ specialized for photosynthesis. For this purpose, a leaf is typically flat (laminar) and thin, to expose the cells containing chloroplast (chlorenchyma tissue, a type of parenchyma) to light over a broad area, and to allow light to penetrate
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Deciduous means "temporary" or "tending to fall off" (deriving from the Latin word decidere, to fall off) and is typically used in reference to trees or shrubs that lose their leaves seasonally.
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P. longaeva

Binomial name
Pinus longaeva
D.K.Bailey

The Great Basin Bristlecone Pine (Pinus longaeva
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Welwitschiales

Family: Welwitschiaceae

Genus: Welwitschia

Species: W.
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gymnosperms (Gymnospermae) are a group of spermatophyte seed-bearing plants with ovules on the edge or blade of an open sporophyll, the sporophylls usually arranged in cone-like structures.
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Tropical rainforests are rainforests generally found near the equator. They are common in Asia, Africa, South America, Central America, and on many of the Pacific Islands.
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temperate latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally mild, rather than extreme hot or cold. However, a temperate climate can have very unpredictable weather.
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Pinophyta

Class: Pinopsida

Orders & Families

Cordaitales †
Pinales
  Pinaceae - Pine family
  Araucariaceae - Araucaria family
  Podocarpaceae - Yellow-wood family
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Magnoliophyta

Classes

Magnoliopsida - Dicots
Liliopsida - Monocots

The flowering plants or angiosperms are the most widespread group of land plants. The flowering plants and the gymnosperms comprise the two extant groups of seed plants.
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Psychrophiles or Cryophiles (adj. cryophilic) are extremophilic organisms that are capable of growth and reproduction in cold temperatures. They can be contrasted with thermophiles, which thrive at unusually hot temperatures.
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Pinus
L.

Subgenera
  • Subgenus Strobus
  • Subgenus Ducampopinus
  • Subgenus Pinus
See Pinus classification for complete taxonomy to species level.
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Cupressaceae
Richard ex Bartling

Genera

Actinostrobus - Cypress-pine
Athrotaxis - Tasmanian Cedar Austrocedrus
Callitris - Cypress-pine
Callitropsis - Cypress * (Cupressus)
Calocedrus
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Rhododendron
L.

Subgenera
  • Azaleastrum
  • Candidastrum
  • Hymenanthes
  • Mumeazalea
  • Pentanthera (Azaleas)
  • Rhododendron
  • Therorhodion
  • Tsutsusi (Azaleas)

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Taiga (IPA pronunciation: /ˈtaɪgə/ or /taɪˈga/, from Mongolian) is a biome characterized by coniferous forests.
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Boreal may refer to:
  • Northern, from Boreas, god of the North Wind in Greek mythology
  • Boreal climate, the climate found in a region of boreal forests, and designated Dfc, Dwc or Dsc in the Köppen climate classification scheme.

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Oecologia is an international peer-reviewed English language journal that publishes original research into topics related to ecology. As of 2005 it had an impact factor of 3.032, giving it a ranking of 24 among ecology journals.
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Deciduous means "temporary" or "tending to fall off" (deriving from the Latin word decidere, to fall off) and is typically used in reference to trees or shrubs that lose their leaves seasonally.
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Semi-deciduous is a botanical term which refers to plants that lose their foliage. Semi-deciduous plants lose their foliage for a very short period, when old leaves fall off and new foliage growth is starting.
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evergreen game is a famous chess game played in 1852 between Adolf Anderssen and Jean Dufresne.

Adolf Anderssen was one of the strongest players of his time, and was considered by many to be the world champion after winning the 1851 London tournament.
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