page_title: Montane ecosystems
section_title: Life zones
hierarchical_section_title: Montane ecosystems / Life zones
caption_attribution_description: English: Mountain birch (Betula pubescens subsp. ssp. czerepanovii) trees reaching 4-5m tall. The ground is covered with bilberry plants, and there are some Juniperus communis. Picture taken near the path to Jøldalshytta (lodge) in Trollheimen mts, altitude approximately 750 m (2400 ft). Rennebu municipality, Sør-Trøndelag, Norway. Norsk bokmål: Typisk fjellbjørkeskog i Jøldalen på stien inn mot Jøldalshytta, Trollheimen. Blåbærlyng dominerer på bakken, noen einer er ogsås synlige. Einer er ofte et tegn på at området beites av husdyr, og mange av dalene i Trollheimen ble da også brukt som seterdaler. Rennebu kommune, Sør-Trøndelag, ca 750 m over havet. Suomi: Tunturikoivuja (Betula pubescens subsp. ssp. czerepanovii) ovat noin 4-5 metriä korkeita. Tunturikoivujen ympärillä on mustikkaa ja muutamia katajia (Juniperus communis). Kuva on otettu arviolta noin 750 metrin korkeudessa merenpinnasta. Rennebu, Sør-Trøndelag, Norway.
context_page_description: Montane ecosystems are found on the slopes of mountains. The alpine climate in these regions strongly affect the ecosystem because temperatures fall as elevation increases, causing the ecosystem to stratify. Dense montane forests are common at moderate elevations, due to moderate temperatures and high rainfall. At higher elevations, the climate is harsher, with lower temperatures and higher winds, preventing the growth of trees and causing the plant community to transition to montane grasslands, shrublands or alpine tundra.
context_section_description: As elevation increases, the climate becomes cooler, due to a decrease in atmospheric pressure and the adiabatic cooling of airmasses. The change in climate by moving up 100 meters on a mountain is roughly equivalent to moving 80 kilometers (45 miles or 0.75° of latitude) towards the nearest pole. The characteristic flora and fauna in the mountains tend to strongly depend on elevation, because of the change in climate. This dependency causes life zones to form: bands of similar ecosystems at similar altitude.
  One of the typical life zones on mountains is the montane forest: at moderate elevations, the rainfall and temperate climate encourages dense 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). Above the elevation of the montane forest, the trees thin out in the subalpine zone, become twisted krummholz, and eventually fail to grow. Therefore, montane forests often contain trees with twisted trunks. This phenomenon is observed due to the increase in the wind strength with the elevation. 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).
  Above the tree line the ecosystem is called the alpine zone or alpine tundra, dominated by grasses and low-growing shrubs. The biotemperature of the alpine zone is between 1.5 and 3 °C (34.7 and 37.4 °F). Many different plant species live in the alpine environment, including perennial grasses, sedges, forbs, cushion plants, mosses, and lichens. Alpine plants must adapt to the harsh conditions of the alpine environment, which include low temperatures, dryness, ultraviolet radiation, and a short growing season. Alpine plants display adaptations such as rosette structures, waxy surfaces, and hairy leaves. Because of the common characteristics of these zones, the World Wildlife Fund groups a set of related ecoregions into the "montane grassland and shrubland" biome. A region in the Hengduan Mountains adjoining Asia’s Tibetan Plateau have been identified as the world’s oldest continuous alpine ecosystem with a community of 3000 plant species, some of them continuously co-existing for 30 million years.
  Climates with biotemperatures below 1.5 °C (35 °F) tend to consist purely of rock and ice.
caption: A stand of mountain birch at around 750 m in Trollheimen, typical of Scandinavian subalpine forests
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