Montane ecosystems are found on the slopes ofmountains. Thealpine climate in these regions strongly affects theecosystem because temperaturesfall as elevation increases, causing the ecosystem to stratify. This stratification is a crucial factor in shaping plant community, biodiversity, metabolic processes and ecosystem dynamics for montane ecosystems.[1] Dense montaneforests 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 tomontane grasslands and shrublands oralpine tundra. Due to the unique climate conditions of montane ecosystems, they contain increased numbers of endemic species. Montane ecosystems also exhibit variation inecosystem services, which include carbon storage and water supply.[2]
As elevation increases, theclimate becomes cooler, due to a decrease inatmospheric pressure and theadiabatic cooling of airmasses.[3] Inmiddle latitudes, the change in climate by moving up 100 meters on a mountain is roughly equivalent to moving 80 kilometers (45 miles or 0.75° oflatitude) towards the nearest pole.[4] The characteristic flora and fauna in the mountains tend to strongly depend on elevation, because of the change in climate. This dependency causeslife zones to form: bands of similar ecosystems at similar elevations.[5]
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).[5] Above the elevation of the montane forest, the trees thin out in the subalpine zone, become twistedkrummholz, 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 thetree line. The biotemperature of the subalpine zone is between 3 and 6 °C (37 and 43 °F).[5]
Above the tree line the ecosystem is called the alpine zone oralpine 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, includingperennial grasses,sedges,forbs,cushion plants,mosses, andlichens.[7] 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, theWorld Wildlife Fund groups a set of relatedecoregions into the "montane grassland and shrubland" biome. A region in theHengduan 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.[8]
Climates with biotemperatures below 1.5 °C (35 °F) tend to consist purely of rock and ice.[5]
Montane forests occur between thesubmontane zone and thesubalpine zone. The elevation at which one habitat changes to another varies across the globe, particularly bylatitude. The upper limit of montane forests, thetree line, is often marked by a change to hardier species that occur in less dense stands.[9] For example, in theSierra Nevada ofCalifornia, the montane forest has dense stands oflodgepole pine andred fir, while theSierra Nevada subalpine zone contains sparse stands ofwhitebark pine.[10]
The lower bound of the montane zone may be a "lower timberline" that separates the montane forest from driersteppe ordesert region.[9]
Montane forests differ from lowland forests in the same area.[11] 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.[12] Humans can disturb montane forests throughforestry andagriculture.[11] On isolated mountains, montane forests surrounded by treeless dry regions are typical "sky island" ecosystems.[13]
Montane forests in temperate climate are typically one oftemperate coniferous forest ortemperate broadleaf and mixed forest, forest types that are well known fromEurope and northeasternNorth America. Montane forests outside Europe tend to be more species-rich, because Europe during the Pleistocene offered smaller-area refugia from the glaciers.[14]
Montane forests in temperate climate occur in Europe (theAlps,Carpathians, andmore),[15] inNorth America (e.g.,Appalachians,Rocky Mountains,Cascade Range, andSierra Nevada),[16]South America,[17]New Zealand,[18] and theHimalayas.
Climate change is predicted to affect temperate montane forests. For example, in thePacific Northwest of North America, climate change may cause "potential reduced snowpack, higher levels of evapotranspiration, increased summer drought" which will negatively affect montane wetlands.[19]
.jpg)
Montane forests inMediterranean climate are warm and dry except in winter, when they are relatively wet and mild. Montane forests located in Mediterranean climates, known as oro-Mediterranean, exhibit towering trees alongside high biomass.[20] These forests are typically mixed conifer and broadleaf forests, with only a few conifer species.Pine andjuniper are typical trees found in Mediterranean montane forests. The broadleaf trees show more variety and are often evergreen, e.g.evergreen oak.[citation needed]
This type of forest is found in theMediterranean Basin,North Africa,Mexico and thesouthwestern US,Iran,Pakistan andAfghanistan.[citation needed]
In the tropics, montane forests can consist ofbroadleaf forest in addition toconiferous forest. One example of a tropical montane forest is acloud forest, which gains its moisture from clouds and fog.[21][22][23] Cloud forests often exhibit an abundance ofmosses covering the ground and vegetation, in which case they are also referred to as mossy forests. Mossy forests usually develop on thesaddles of mountains, where moisture introduced by settling clouds is more effectively retained.[24] Depending on latitude, the lower limit of montane rainforests on large mountains is generally between 1,500 and 2,500 metres (4,900 and 8,200 ft) while the upper limit is usually from 2,400 to 3,300 metres (7,900 to 10,800 ft).[25]
Tropical montane forests might exhibit high sensitivity to climate change.[26][27] Climate change may cause variation in temperature, precipitation and humidity, which will cause stress on tropical montane forests. The predicted upcoming impacts of climate change might significantly affectbiodiversity loss and might result in change of species range and community dynamics.Global climate models predict reduced cloudiness in the future. Reduction in cloudiness may already be affecting theMonteverde cloud forest inCosta Rica.[28][29]
The subalpine zone is thebiotic zone immediately below thetree line around the world. In tropical regions ofSoutheast Asia the tree line may be above 4,000 m (13,000 ft),[30] whereas in Scotland it may be as low as 450 m (1,480 ft).[31] Species that occur in this zone depend on the location of the zone on the Earth; for example,Pinus mugo (scrub mountain pine) occurs inEurope,[32] thesnow gum is found in Australia,[33] and thesubalpine larch,mountain hemlock, andsubalpine fir occur in western North America.[34]
Trees in the subalpine zone often becomekrummholz, that is, crooked wood, stunted and twisted in form. At tree line, tree seedlings may germinate on thelee 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.[35]
Meadows may be found in the subalpine zone.Tuolumne Meadows in theSierra Nevada ofCalifornia, is an example of a subalpine meadow.[36]
Example subalpine zones around the world include theFrench Prealps in Europe, theSierra Nevada andRocky Mountain subalpine zones in North America, and subalpine forests in theeastern Himalaya,western Himalaya, andHengduan mountains of Asia.
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 ofperennial grasses,sedges, andforbs. Annual plants are rare in this ecosystem and usually are only a few inches tall, with weak root systems.[37] Other commonplant life-forms includeprostrate shrubs;tussock-forminggraminoids; andcryptogams, such asbryophytes andlichens.[7]: 280
Plants have adapted to the harsh alpine environment.Cushion plants, looking like ground-hugging clumps of moss, escape the strong winds blowing a few inches above them. Many flowering plants of the alpine tundra have dense hairs on stems and leaves to provide wind protection orred-colored pigments capable of converting the sun's light rays into heat. Some plants take two or more years to form flower buds, which survive the winter below the surface and then open and produce fruit with seeds in the few weeks of summer.[38] Non-floweringlichens cling to rocks and soil. Their enclosedalgal cells canphotosynthesize at temperatures as low as −10 °C (14 °F),[39] and the outer fungal layers can absorb more than their own weight in water.[40]
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.[38]
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 abiome by theWorld Wildlife Fund. The biome, called "Montane grasslands and shrublands", often evolved as virtual islands, separated from other montane regions by warmer, lower elevation regions, and are frequently home to many distinctive andendemic plants which evolved in response to the cool, wetclimate and abundant sunlight.[citation needed]
The most extensive montane grasslands and shrublands occur in theNeotropicalpáramo of theAndes Mountains. This biome also occurs in the mountains ofeast andcentral Africa,Mount Kinabalu ofBorneo, the highest elevations of theWestern Ghats in South India and the Central Highlands ofNew Guinea. A unique feature of many wet tropical montane regions is the presence of giant rosette plants from a variety of plant families, such asLobelia (Afrotropic),Puya (Neotropic),Cyathea (New Guinea), andArgyroxiphium (Hawaii).[citation needed]
Where conditions are drier, one finds montane grasslands,savannas, andwoodlands, like theEthiopian Highlands, and montanesteppes, like the steppes of theTibetan Plateau.[citation needed]
This article incorporatespublic domain material fromGrassland Habitat Group(PDF).Bureau of Land Management. Archived fromthe original(PDF) on 24 July 2008. This article incorporatespublic domain material from"Alpine Tundra Ecosystem".Rocky Mountain National Park.National Park Service.
Media related toMontane ecology at Wikimedia Commons
Definitions from Wiktionary
Media from Commons
