Evergreen

Source: Wikipedia, the free encyclopedia.
This article is about the type of plant. For other uses, see Evergreen (disambiguation).
A silver fir
shoot showing three successive years of retained leaves.

In botany, an evergreen is a plant which has foliage that remains green and functional through more than one growing season. This contrasts with deciduous plants, which completely lose their foliage during the winter or dry season.

Evergreen species

There are many different kinds of evergreen plants, both trees and shrubs. Evergreens include:

The Latin binomial term sempervirens, meaning "always green", refers to the evergreen nature of the plant, for instance:

Cupressus sempervirens (a cypress)
Lonicera sempervirens (a honeysuckle)
Sequoia sempervirens (a sequoia)

Leaf longevity in evergreen plants varies from a few months to several decades (over thirty years in the Great Basin bristlecone pine[1]).

Evergreen families

Family name Example
Araucariaceae Kauri
Cupressaceae Sequoia
Pinaceae Pine
Podocarpaceae Real yellowwood
Taxaceae Yew
Cyatheaceae
Australian tree fern
Aquifoliaceae
 Holly
Fagaceae Live oak
Oleaceae Shamel ash
Myrtaceae Eucalyptus
Arecaceae Coconut
Lauraceae Bay
Magnoliaceae Southern magnolia
Cycadaceae
 Queen sago

Japanese umbrella pine is unique in that it has its own family of which it is the only species.

Differences between evergreen and deciduous species

Evergreen and deciduous species vary in a range of morphological and physiological characters. Generally, broad-leaved evergreen species have thicker leaves than deciduous species, with a larger volume of parenchyma and air spaces per unit leaf area.[2] They have larger leaf biomass per unit leaf area, and hence a lower specific leaf area. Construction costs do not differ between the groups.[citation needed] Evergreens have generally a larger fraction of total plant biomass present as leaves (LMF),[3] but they often have a lower rate of photosynthesis.

Reasons for being evergreen or deciduous

A southern live oak in South Carolina
during winter

Deciduous trees shed their leaves usually as an adaptation to a cold or dry/wet season. Evergreen trees also lose leaves, but each tree loses its leaves gradually and not all at once. Most

conifers because few evergreen broadleaf plants can tolerate severe cold below about −26 °C (−15 °F).[clarification needed][citation needed
]

In areas where there is a reason for being deciduous, e.g. a cold season or dry season, evergreen plants are usually an adaptation of low nutrient levels. Additionally, they usually have

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 favoring 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. This is the case with Mediterranean evergreen seedlings, which have unique C and N storages that allow stored resources to determine fast growth within the species, limiting competition and bolstering survival.[5] These conditions favor 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 younger evergreen plants to survive cold and/or drought.[6][7][8]

See also


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. PMID 24107583
    .
  3. PMID 26197869
    .
  4. ^
    S2CID 3798020. Archived
    from the original on 2022-09-13. Retrieved 2021-02-16.
  5. PMID 25817313
    .
  6. ^ Aerts, R. (1995). "The advantages of being evergreen" Archived 2015-09-24 at the Wayback Machine. Trends in Ecology & Evolution 10 (10): 402–407.
  7. ^ Matyssek, R. (1986) "Carbon, water and nitrogen relations in evergreen and deciduous conifers". Tree Physiology 2: 177–187.
  8. ^ Sobrado, M. A. (1991) "Cost-Benefit Relationships in Deciduous and Evergreen Leaves of Tropical Dry Forest Species". Functional Ecology 5 (5): 608–616.

External links

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