Altitudinal zonation
Altitudinal zonation (or elevational zonation
Factors
A variety of environmental factors determines 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 the growing season at different elevations of the mountain.[2][7] For mountains located in deserts, extreme high temperatures also limit the ability of large deciduous or coniferous trees to grow near the base of mountains.[8] In addition, plants can be especially sensitive to soil temperatures and can have specific elevation ranges that support healthy growth.[9]
Humidity
The humidity of certain zones, including precipitation levels, atmospheric humidity, and potential for
Soil composition
The nutrient content of soils at different elevations 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 elevation 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.[14] 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 (warmer sites or deeper soils).[15][16] 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.[17]
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.
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.[2][3]
Elevation levels
Elevation models of zonation are complicated by factors discussed above and thus the relative elevations each zone begins and ends is not tied to a specific elevation.[20] However it is possible to split the altitudinal gradient into five main zones used by ecologists under varying names. In some cases these level follow each other with the decrease in elevation, which is called vegetation inversion.
- Nival level (glaciers):[21] Covered in snow throughout most of the year. Vegetation is extremely limited to only a few species that thrive on silica soils.[7][20]
- Alpine level:[7][20] The zone that stretches between the tree line and snowline. This zone is further broken down into Sub-Nival and Treeless Alpine (in the tropics-Tierra fria; low-alpine)
- Sub-nival:sedgesand rush heaths typical of arctic zones . Snow is found in this region for part of the year.
- Treeless alpine (low-alpine): Characterized by a closed carpet of vegetation that includes alpine meadows, shrubs and sporadic dwarfed trees. Because of the complete cover of vegetation, frost has less of an effect on this region, but due to the consistent freezing temperatures tree growth is severely limited.
- Sub-nival:
- Montane level:coniferous forestsoften dominate.
- Lowland layer:[4][23] This lowest section of mountains varies distinctly across climates and is referred to by a wide range of names depending on the surrounding landscape. Colline zones are found in tropical regions and Encinal zones and desert grasslands are found in desert regions.
- Colline:[3] Characterized by deciduous forests when in oceanic or moderately continental areas, and characterized by grassland in more continental regions. Extends from sea level to about 3,000 feet (roughly 900 m). Vegetation is abundant and dense.
- Encinal:[12] Characterized by open evergreen oak forests and most common in desert regions. Evaporation and soil moisture control limitation of which encinal environments can thrive. Desert grasslands lie below encinal zones. Very commonly found in the Southwestern United States.
- Desert grassland:[12] Characterized by varying densities of low lying vegetation, grasslands zones cannot support trees due to extreme aridity. Some desert regions may support trees at base of mountains however, and thus distinct grasslands zones will not form in these areas.
For detailed breakdowns of the characteristics of altitudinal zones found on different mountains, see List of life zones by region.
Treeline
The most decisive biogeographic and climatic boundary along elevation gradients is the climatic high-elevation treeline. The treeline separates the
Animal zonation
Animals also exhibit zonation patterns in concert with the vegetational zones described above.[7] Invertebrates are more clearly defined into zones because they are typically less mobile than vertebrate species. Vertebrate animals often span across altitudinal zones according to the seasons and food availability. Typically animal species diversity and abundance decrease as a function of elevation above the montane zone because of the harsher environmental conditions experienced at higher elevations. Fewer studies have explored animal zonation with elevation because this correlation is less defined than the vegetation zones due to the increased mobility of animal species.[7]
Land-use planning and human utilization
The variability of both natural and human environments has made it difficult to construct universal models to explain human cultivation in altitudinal environments. With more established roads however, the bridge between different cultures has started to shrink.[28] Mountainous environments have become more accessible and diffusion of ideas, technology, and goods occur with more regularity. Nonetheless, altitudinal zonation caters to agricultural specialization and growing populations cause environmental degradation.
Agriculture
Human populations have developed agricultural production strategies to exploit varying characteristics of altitudinal zones. Elevation, climate, and soil fertility set upper limits on types of crops that can reside in each zone. Populations residing in the Andes Mountain region of South America have taken advantage of varying altitudinal environments to raise a wide variety of different crops.[11] Two different types of adaptive strategies have been adopted within mountainous communities.[29]
- Generalized Strategy – exploits a series of microniches or ecozones at several elevational levels
- Specialized Strategy – focuses on a single zone and specializes in the agricultural activities suitable to that elevation, developing elaborate trade relationships with external populations
With improved accessibility to new farming techniques, populations are adopting more specialized strategies and moving away from generalized strategies. Many farming communities now choose to trade with communities at different elevations instead of cultivating every resource on their own because it is cheaper and easier to specialize within their altitudinal zone.[28]
Environmental degradation
Population growth is leading to environmental degradation in altitudinal environments through deforestation and overgrazing. The increase in accessibility of mountainous regions allows more people to travel between areas and encourage groups to expand commercial land use. Furthermore, the new linkage between mountainous and lowland populations from improved road access has contributed to worsening environmental degradation.[28]
Debate on continuum versus zonation
Not all mountainous environments exhibit sudden changes in altitudinal zones. Though less common, some tropical environments show a slow continuous change in vegetation over the altitudinal gradient and thus do not form distinct vegetation zones.[30]
See also
Examples
- Life zones of central Europe
- Life zones of the Great Basin of North America
- Life zones of the Mediterranean region
- Life zones of the North Cascades in the Pacific Northwest of America
- Life zones of the Sierra Nevada in California
- Life zones of Peru
References
- ^ McVicar & Körner 2013
- ^ a b c Daubenmire 1943
- ^ a b c d e f g h Frahm & Gradstein 1991
- ^ a b Salter et al. 2005
- ^ Fukarek et al. 1982
- ^ Shipley & Keddy 1987
- ^ a b c d e f Nagy & Grabherr 2009
- ^ Daubenmire 1943, pp. 345–349
- ^ a b Nagy & Grabherr 2009, pp. 30–35
- ^ Daubenmire 1943, pp. 349–352
- ^ a b Stadel 1990
- ^ a b c d Shreve 1922
- ^ Daubenmire 1943, p. 355
- ^ Keddy 2001, p. 552
- ^ Goldberg 1982
- ^ Wilson 1993
- ^ Keddy 2007, p. 666
- ^ Daubenmire 1943, p. 345
- ^ Nagy & Grabherr 2009, p. 31
- ^ a b c d Troll 1973
- ^ Pauli, Gottfried & Grabherr 1999
- ^ Tang & Ohsawa 1997
- ^ Pulgar Vidal 1979, pp. 145–161
- ^ Körner 2012
- ^ Paulsen & Körner 2014
- ^ Zwinger & Willard 1996, p. 58
- ^ Zwinger & Willard 1996, p. 55
- ^ a b c Allan 1986
- ^ Rhoades & Thompson 1975
- ^ Hemp 2006
Sources
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- Daubenmire, R.F. (June 1943). "Vegetational Zonation in the Rocky Mountains". Botanical Review. 9 (6): 325–393. S2CID 10413001.
- Frahm, Jan-Peter; Gradstein, S. Rob. (Nov 1991). "An Altitudinal Zonation of Tropical Rain Forests Using Bryophytes". Journal of Biogeography. 18 (6): 669–678. JSTOR 2845548.
- Fukarek, F; Hempel, I; Hûbel, G; Sukkov, R; Schuster, M (1982). Flora of the Earth (in Russian). Vol. 2. Moscow: Mir. p. 261.
- Goldberg, D.E. (1982). "The distribution of evergreen and deciduous trees relative to soil type: an example from the Sierra Madre, Mexico, and a general model". Ecology. 63 (4): 942–951. JSTOR 1937234.
- Hemp, Andreas (May 2006). "Continuum or Zonation? Altitudinal Gradients in the Forest Vegetation of Mt. Kilimanjaro". Plant Ecology. 184 (1): 27. S2CID 21864541.
- Hemp, Andreas (2006a). "The banana forests of Kilimanjaro. Biodiversity and conservation of the agroforestry system of the Chagga Home Gardens". Biodiversity and Conservation. 15 (4): 1193–1217. S2CID 32921501.
- Keddy, P.A. (2001). Competition (2nd ed.). Dordrecht: Kluwer.
- Keddy, P.A. (2007). Plants and Vegetation: Origins, Processes, Consequences. Cambridge, UK: Cambridge University Press.
- Körner, C (2012). Alpine Treelines. Basel: Springer.
- McVicar, TR; Körner, C (2013). "On the use of elevation, altitude, and height in the ecological and climatological literature". Oecologia. 171 (2): 335–337. S2CID 17254606.
- Nagy, Laszlo; Grabherr, Georg (2009). The Biology of Alpine Habitats: Biology of Habitats. New York: Oxford University Press. pp. 28–50. ISBN 978-0-19-856703-5.
- Pauli, H.; Gottfried, M.; Grabherr, G. (1999). "Vascular Plant Distribution Patterns at the Low-Temperature Limits of Plant Life - the Alpine-Nival Ecotone of Mount Schrankogel (Tyrol, Austria)". Phytocoenologia. 29 (3): 297–325. .
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- Pulgar Vidal, Javier [in German] (1979). Geografía del Perú; Las Ocho Regiones Naturales del Perú. Lima: Edit. Universo S.A., note: 1st Edition (his dissertation of 1940); Las ocho regiones naturales del Perú, Boletín del Museo de Historia Natural „Javier Prado“, n° especial, Lima, 1941, 17, pp. 145–161.
- Rhoades, R.E.; Thompson, S.I. (1975). "Adaptive strategies in alpine environments: Beyond ecological particularism". American Ethnologist. 2 (3): 535–551. .
- Salter, Christopher; Hobbs, Joseph; Wheeler, Jesse; Kostbade, J. Trenton (2005). Essentials of World Regional Geography 2nd Edition. New York: Harcourt Brace. pp. 464–465.
- Shipley, B.; Keddy, P.A. (1987). "The individualistic and community-unit concepts as falsifiable hypotheses". Vegetation. 69 (1–3): 47–55. S2CID 25395638.
- Shreve, Forrest (Oct 1922). "Conditions Indirectly Affecting Vertical Distribution on Desert Mountains" (PDF). Ecology. 3 (4): 269–274. JSTOR 1929428. Retrieved 2010-05-06.
- Stadel, Christoph (October 1990). Tom L. Martinson (ed.). "Altitudinal Belts in the Tropical Andes: Their Ecology and Human Utilization". Yearbook. Conference of Latin Americanist Geographers. 17/18. Auburn, Alabama: 45–60. JSTOR 25765738.
- Tang, C. Q.; Ohsawa, M. (1997). "Zonal Transition of Evergreen, Deciduous, and Coniferous Forests Along the Altitudinal Gradient on a Humid Subtropical Mountain, Mt. Emei, Sichuan, China". Plant Ecology. 133 (1): 63–78. S2CID 30790987.
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- Wilson, S.D. (1993). "Competition and resource availability in heath and grassland in the Snowy Mountains of Australia". Journal of Ecology. 81 (3): 445–451. JSTOR 2261523.
- Zwinger, A.; Willard, B. E. (1996). Land Above the Trees: A Guide to American Alpine Tundra. Big Earth Publishing. ISBN 978-1-55566-171-7.