Life zone

Life zone

The Life Zone concept was developed by C. Hart Merriam in 1889 as a means of describing areas with similar plant and animal communities. Merriam observed that the changes in these communities with an increase in latitude at a constant elevation are similar to the changes seen with an increase in elevation at a constant latitude.

The life zones Merriam identified are most applicable to western North America, being developed on the San Francisco Peaks, Arizona and Cascade Range of the northwestern USA. He tried to develop a system that is applicable across the North American continent, but that system is rarely referred to.

The life zones that Merriam identified, along with characteristic plants, are as follows:
* Lower Sonoran (low, hot desert): Creosotebush, Joshua Tree
* Upper Sonoran (desert steppe or chaparral): Sagebrush, Scrub Oak, Colorado Pinyon, Utah Juniper
* Transition (open woodlands): Ponderosa Pine
* Canadian (fir forest): Rocky Mountain Douglas-fir, Quaking Aspen
* Hudsonian (spruce forest): Engelmann Spruce, Rocky Mountains Bristlecone Pine
* Arctic-Alpine (alpine meadows or tundra): Lichen, Grass

The Canadian and Hudsonian life zones are commonly combined into a Boreal life zone.

This system has been criticized as being too imprecise. For example, the scrub oak chaparral in Arizona shares relatively few plant and animal species with the Great Basin sagebrush desert, yet both are classified as Upper Sonoran. However it is still sometimes referred to by biologists (and anthropologists) working in the western United States. Much more detailed and empirically based classifications of vegetation and life zones now exist for most areas of the world.

Holdridge

In 1947, Leslie Holdridge published a life zone classification using indicators of:
* mean annual biotemperature (logarithmic)
* annual precipitation (logarithmic)
* ratio of annual potential evapotranspiration to mean total annual precipitation.

Biotemperature refers to all temperatures above freezing, with all temperatures below freezing adjusted to 0°C, as plants are dormant at these temperatures. Holdridge's system uses biotemperature first, rather than the temperate latitude bias of Merriam's life zones, and does not primarily use elevation. The system is considered more appropriate to the complexities of tropical vegetation than Merriam's system.

ee also

*California chaparral and woodlands

References

* [http://www.radford.edu/~swoodwar/CLASSES/GEOG235/lifezone/holdrdge.html Holdridge's Life Zones] , Radford University, Geology class notes.


Wikimedia Foundation. 2010.

Игры ⚽ Поможем сделать НИР

Look at other dictionaries:

  • life zone — n. any of a series of biogeographic zones into which a continent, region, etc. is divided both by latitude and altitude on the basis of the characteristic animal and plant life in a zone * * * …   Universalium

  • life zone — n. any of a series of biogeographic zones into which a continent, region, etc. is divided both by latitude and altitude on the basis of the characteristic animal and plant life in a zone …   English World dictionary

  • life zone — life′ zone n. ecl any extensive area defined by its characteristic animal life and vegetation; a biogeographical region …   From formal English to slang

  • life zone — noun : a biogeographic zone * * * life zone, a region that generally has a uniform type of plant or animal life, and a single type of climate. Because of environment, the plants in one life zone usually differ from the plants in another zone.… …   Useful english dictionary

  • life zone — noun Date: 1893 a region characterized by specific plants and animals …   New Collegiate Dictionary

  • life zone — noun any large portion of the Earths land area which has a generally uniform climate and soil and therefore a high degree of uniformity in the composition of species; a number of different classifications have been proposed by different people …   Wiktionary

  • The Life Zone — est un film américain pro vie de 2011, réalisé par Rod Weber, sur un scenario du candidat au poste de sénateur du New Jersey, Kenneth Del Vecchio. Distribution Amanda : Amanda Antonucci Dr Victoria Wise : Blanche Baker Rebecca :… …   Wikipédia en Français

  • Zone — one (z[=o]n), n. [F. zone, L. zona, Gr. zw nh; akin to zwnny nai to gird, Lith. j[*u]sta a girdle, j[*u]sti to gird, Zend y[=a]h.] 1. A girdle; a cincture. [Poetic] [1913 Webster] An embroidered zone surrounds her waist. Dryden. [1913 Webster]… …   The Collaborative International Dictionary of English

  • Zone axis — Zone one (z[=o]n), n. [F. zone, L. zona, Gr. zw nh; akin to zwnny nai to gird, Lith. j[*u]sta a girdle, j[*u]sti to gird, Zend y[=a]h.] 1. A girdle; a cincture. [Poetic] [1913 Webster] An embroidered zone surrounds her waist. Dryden. [1913… …   The Collaborative International Dictionary of English

  • Zone of the Enders: The 2nd Runner — North American box art Developer(s) KCEJ …   Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”