User:Hike395/altitudinal zonation
Article titled either Altitudinal zonation or Ecology of mountains
Factors
A variety of environmental factors determine the boundaries of altitudinal zones found on mountains, ranging from direct effects of temperature and
Temperature
Decreasing air temperature usually coincides with increasing elevation, which directly influences the length of the growing season at different altitudes on the mountain.[3][4] For mountains located in deserts, extreme high temperatures also limit the ability of large trees to grow near the base of mountains.[5] In addition, plants can be especially sensitive to soil temperatures and can have specific elevation ranges that support healthy growth.[6]
Humidity
The humidity of certain zones, including precipitation levels, atmospheric humidity, and potential for
Soil composition
The nutrient content of soils at different altitudes further complicates the demarcation of altitudinal zones. Soils with higher nutrient content, due to higher decomposition rates or greater weathering of rocks, better support larger trees and vegetation. The altitude of better soils varies with the particular mountain being studied. For example, for mountains found in the
Biological forces
In addition to physical forces, biological forces may also produce zonation. For example, a strong competitor can force weaker competitors to higher or lower positions on the elevation gradient.[12] The importance of competition is difficult to assess without experiments, which are expensive and often take many years to complete. However, there is an accumulating body of evidence that competitively dominant plants may seize the preferred locations (that is warmer sites or deeper soils).[13][14] Two other biological factors can influence zonation: grazing and mutualism. The relative importance of these factors is also difficult to assess, but the abundance of grazing animals, and the abundance of mycorrhizal associations, suggests that these elements may influence plant distributions in significant ways.[15]
Solar radiation
Light is another significant factor in the growth of trees and other
Massenerhebung effect
The physical characteristics and relative location of the mountain itself must also be considered in predicting altitudinal zonation patterns.[7] The Massenerhebung effect describes variation in the tree line based on mountain size and location. This effect predicts that zonation of rain forests on lower mountains may mirror the zonation expected on high mountains, but the belts occur at lower altitudes.[7] A similar effect is exhibited in the Santa Catalina Mountains of Arizona, where the basal elevation and the total elevation influence the altitude of vertical zones of vegetation.[10]
Other factors
In addition to the factors described above, there are a host of other properties that can confound predictions of altitudinal zonations. These include: frequency of disturbance (such as fire or monsoons), wind velocity, type of rock, topography, nearness to streams or rivers, history of tectonic activity, and latitude.[3][7]
History
Merriam
Altitudinal zonation was first described by C. Hart Merriam in 1889, who used the term life zone to define 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.[18]
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): creosote bush, Joshua tree
- Upper Sonoran (desert steppe or Utah juniper
- Transition (open woodlands): ponderosa pine
- Canadian (fir forest): Rocky Mountain Douglas fir, quaking aspen
- Hudsonian (spruce forest): Rocky Mountains bristlecone pine
- Arctic-Alpine (alpine meadows or tundra): 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
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.[21]
At moderate elevations in mountains, the rainfall and temperate climate encourages dense montane forests to grow. Holdridge defines the climate of montane forest as having a biotemperature of between 6 and 12 °C (43 and 54 °F), where biotemperature is the mean temperature considering temperatures below 0 °C (32 °F) to be 0 °C (32 °F).[22] Above the elevation of the montane forest, the trees thin out in the subalpine zone, become twisted krummholz, and eventually fail to grow. The elevation where trees fail to grow is called the tree line. The biotemperature of the subalpine zone is between 3 and 6 °C (37 and 43 °F).[22]
Above the tree line the ecosystem is called the alpine zone or
Climates with biotemperatures below 1.5 °C (35 °F) tend to consist purely of rock and ice.[22]
Biotic zones in mountains
The details of the altitudinal zonation in mountains depends on the latitude and other local factors.
Montane forests
Montane forests occur around the world. The elevation of these forests varies across the globe, particularly by
The lower bound of the montane zone may be a "lower timberline" that separates the montane forest from drier steppe or desert region.[24]
Montane forests differ from lowland forests in the same area.[26] The climate of montane forests is colder than lowland climate at the same latitude, so the montane forests often have species typical of higher-latitude lowland forests.[27] Humans can disturb montane forests through forestry and agriculture.[26] On isolated mountains, montane forests surrounded by treeless dry regions are typical "sky island" ecosystems.[28]
Temperate climate
Montane forests in temperate climate are typically one of
Montane forests around the world tend to be more species-rich than those in Europe, because major mountain chains in Europe are oriented east-west, which blocked species migration in the last ice age.
Montane forests in temperate climate occur in Europe (the
Mediterranean climate
Montane forests in mediterranean climate are warm and dry except in winter, when they are relatively wet and mild. These forests are typically mixed conifer and broadleaf forests, with only a few conifer species. Pine and Juniper are typical trees found in Mediterranean montane forests. The broadleaf trees show more variety and often evergreen, e.g., evergreen Oak.
This type of forest is found in the
.Subtropical and tropical climate
In the tropics, montane forests can consist of
Subalpine zone
The subalpine zone is the
Trees in the subalpine zone often become krummholz, that is, crooked wood, stunted and twisted in form. At tree line, tree seedlings may germinate on the lee side of rocks and grow only as high as the rock provides wind protection. Further growth is more horizontal than vertical, and additional rooting may occur where branches contact the soil. Snow cover may protect krummholz trees during the winter, but branches higher than wind-shelters or snow cover are usually destroyed. Well-established krummholz trees may be several hundred to a thousand years old.[34]
Example subalpine zones around the world include the French Prealps in Europe, the Sierra Nevada and Rocky Mountain subalpine zones in North America, and subalpine forests in the eastern Himalaya, western Himalaya, and Hengduan mountains of Asia.
Alpine grasslands and tundra
Alpine grasslands and tundra lie above the tree line, in a world of intense radiation, wind, cold, snow, and ice. As a consequence, alpine vegetation is close to the ground and consists mainly of
Plants have adapted to the harsh alpine environment.
The adaptations for survival of drying winds and cold may make tundra vegetation seem very hardy, but in some respects the tundra is very fragile. Repeated footsteps often destroy tundra plants, leaving exposed soil to blow away, and recovery may take hundreds of years.[36]
Alpine meadows form where sediments from the weathering of rocks has produced soils well-developed enough to support grasses and sedges. Alpine grasslands are common enough around the world to be categorized as a
The most extensive montane grasslands and shrublands occur in the
).Where conditions are drier, one finds montane grasslands, savannas, and woodlands, like the Ethiopian Highlands, and montane steppes, like the steppes of the Tibetan Plateau.
Examples of zonation
- Ecology of the Rocky Mountains
- California montane chaparral and woodlands, an ecoregion.
- Ecology of the Sierra Nevada
- Great Basin Desert
- East African montane forests
- Afromontane, a series of high-elevation regions in Africa
- Angolan montane forest-grassland mosaic, an ecoregion.
- Australian Alps montane grasslands, an ecoregion.
- South Western Ghats montane rain forests, an ecoregion
- Life zones of central Europe
- Life zones of the Mediterranean region
- Life zones of Peru
See also
- Biome
- Ecozone
- Ecoregion
- Forest ecology
- Temperate coniferous forests
References
- ^ Fukarek, F; Hempel, I; Hûbel, G; Sukkov, R; Schuster, M (1982). Flora of the Earth (in Russian). Vol. 2. Moscow: Mir. p. 261.
- .
- ^ a b Daubenmire 1943
- ^ Nagy & Grabherr 2009 harvnb error: multiple targets (2×): CITEREFNagyGrabherr2009 (help)
- ^ Daubenmire 1943, pp. 345–349
- ^ a b Nagy & Grabherr 2009, pp. 30–35 harvnb error: multiple targets (2×): CITEREFNagyGrabherr2009 (help)
- ^ a b c d e f Frahm & Gradstein 1991
- ^ Daubenmire 1943, pp. 349–352
- ^ Stadel 1990
- ^ a b Shreve 1922
- ^ Daubenmire 1943, p. 355
- ^ Keddy, P.A. (2001). Competition (2nd ed.). Dordrecht: Kluwer. p. 552.
- JSTOR 1937234.
- JSTOR 2261523.
- ^ Keddy, P.A. (2007). Plants and Vegetation: Origins, Processes, Consequences. Cambridge, UK: Cambridge University Press. p. 666.
- ^ Daubenmire 1943, p. 345
- ^ Nagy & Grabherr 2009, p. 31 harvnb error: multiple targets (2×): CITEREFNagyGrabherr2009 (help)
- ISBN 9780816072293.
- ^ Ricketts, Taylor H.; Dinerstein, Eric; Olson, David M.; Loucks, Colby J.; et al. (1999). Terrestrial Ecoregions of North America: a Conservation Assessment. Washington DC: Island Press.
- ^ "Ecological Regions of North America: Toward a Common Perspective" (PDF). Commission for Environmental Cooperation. 1997.
- ^ "Holdridge's Life Zones". Geology class notes. Radford University.
- ^ .
- ^ a b Körner, Christian (2003). Alpine Plant Life: Functional Plant Ecology of High Mountain Ecosystems. Berlin: Springer.
- ^ ISBN 9780520058866. Retrieved 2012-03-09.
- ^ Rundel, P.W.; D. J. Parsons; D. T. Gordon (1977). "Montane and subalpine vegetation of the Sierra Nevada and Cascade Ranges". In Barbour, M.G.; Major, J. (eds.). Terrestrial vegetation of California. New York, USA: Wiley. pp. 559–599.
- ^ a b Nagy, László; Grabherr, Georg (2009). The biology of alpine habitats. Oxford University Press.
- ISBN 0-8018-4987-X. Retrieved 2012-03-09.
- ISBN 978-0-520-26868-5. Retrieved 2012-03-09.
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{{cite book}}
: CS1 maint: multiple names: editors list (link - ^ Clarke, C.M. (1997). Nepenthes of Borneo. Kota Kinabalu: Natural History Publications (Borneo). p. 29.
- JSTOR 176859.
- doi:10.1016/S0006-3207(00)00032-X. Archived from the original(PDF) on 2012-09-04. Retrieved 2012-03-11. p. 178.
- PMID 12324278. fig. 1.
- ^ "Subalpine ecosystem". Rocky Mountain National Park. U.S. National Park Service.
- ^ This article incorporates public domain material from "Grassland Habitat Group" (PDF). Archived from the original (PDF) on 2008-07-24.
- ^ a b This article incorporates public domain material from Rocky Mountain National Park: Alpine Tundra Ecosystem. National Park Service.
Sources
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- Frahm, Jan-Peter; Gradstein, S. Rob. (Nov 1991). "An Altitudinal Zonation of Tropical Rain Forests Using Byrophytes". Journal of Biogeography. 18 (6): 669–678. JSTOR 2845548.
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