Alpine tundra

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Hikers traversing the Franconia Ridge in the White Mountains of New Hampshire, much of which is in the alpine zone. Hikers on franconia ridge.JPG
Hikers traversing the Franconia Ridge in the White Mountains of New Hampshire, much of which is in the alpine zone.
Alpine tundra in the Venezuelan Andes Valle de Mifafi 3.jpg
Alpine tundra in the Venezuelan Andes

Alpine tundra is a type of natural region or biome that does not contain trees because it is at high elevation. As the latitude of a location approaches the poles, the threshold elevation for alpine tundra gets lower until it reaches sea level, and alpine tundra merges with polar tundra.

Contents

The high elevation causes an adverse climate, which is too cold and windy to support tree growth. Alpine tundra transitions to sub-alpine forests below the tree line; stunted forests occurring at the forest-tundra ecotone are known as Krummholz . With increasing elevation it ends at the snow line where snow and ice persist through summer.

Alpine tundra occurs in mountains worldwide. The flora of the alpine tundra is characterized by dwarf shrubs close to the ground. The cold climate of the alpine tundra is caused by adiabatic cooling of air, and is similar to polar climate.

Geography

Alpine tundra occurs at high enough altitude at any latitude. Portions of montane grasslands and shrublands ecoregions worldwide include alpine tundra. Large regions of alpine tundra occur in the North American Cordillera and parts of the northern Appalachian Mountains in North America, the Alps and Pyrenees of Europe, the Himalaya and Karakoram of Asia, the Andes of South America, the Eastern Rift mountains of Africa, and the South Island of New Zealand. [1] [2] [3]

Alpine tundra occupies high-mountain summits, slopes, and ridges above timberline. Aspect plays a role as well; the treeline often occurs at higher elevations on warmer equator-facing slopes. Because the alpine zone is present only on mountains, much of the landscape is rugged and broken, with rocky, snowcapped peaks, cliffs, and talus slopes, but also contains areas of gently rolling to almost flat topography. [4]

Averaging over many locations and local microclimates, the treeline rises 75 meters (245 ft) when moving 1 degree south from 70 to 50°N, and 130 meters (430 ft) per degree from 50 to 30°N. Between 30°N and 20°S, the treeline is roughly constant, between 3,500 and 4,000 meters (11,500 and 13,100 ft). [5]

Climate

Summer in Northern Sweden's Tarfala Valley with its alpine climate Tarfala Valley - Sweden.jpg
Summer in Northern Sweden's Tarfala Valley with its alpine climate

Alpine climate is the average weather (climate) for the alpine tundra. The climate becomes colder at high elevations—this characteristic is described by the lapse rate of air: air tends to get colder as it rises, since it expands. The dry adiabatic lapse rate is 10 °C per km (5.5 °F per 1000 ft) of elevation or altitude. Therefore, moving up 100 meters (330 ft) on a mountain is roughly equivalent to moving 80 kilometers (45 miles or 0.75° of latitude) towards the pole. [6] This relationship is only approximate, however, since local factors such as proximity to oceans can drastically modify the climate.

Typical high-elevation growing seasons range from 45 to 90 days, with average summer temperatures near 10 °C (50 °F). Growing season temperatures frequently fall below freezing, and frost occurs throughout the growing season in many areas. Precipitation occurs mainly as winter snow, but soil water availability is highly variable with season, location, and topography. For example, snowfields commonly accumulate on the lee sides of ridges while ridgelines may remain nearly snow free due to redistribution by wind. Some alpine habitats may be up to 70% snow free in winter. High winds are common in alpine ecosystems, and can cause significant soil erosion and be physically and physiologically detrimental to plants. Also, wind coupled with high solar radiation can promote extremely high rates of evaporation and transpiration. [4]

Quantifying the climate

Alpine tundra above the tree line below Musala Peak in Rila Mountain, Bulgaria Musala.JPG
Alpine tundra above the tree line below Musala Peak in Rila Mountain, Bulgaria

There have been several attempts at quantifying what constitutes an alpine climate.

Climatologist Wladimir Köppen demonstrated a relationship between the Arctic and Antarctic tree lines and the 10 °C summer isotherm; i.e., places where the average temperature in the warmest calendar month of the year is below 10 °C cannot support forests. See Köppen climate classification for more information.

Otto Nordenskjöld theorized that winter conditions also play a role: His formula is W = 9 − 0.1 C, where W is the average temperature in the warmest month and C the average of the coldest month, both in degrees Celsius (this would mean, for example, that if a particular location had an average temperature of −20 °C (−4 °F) in its coldest month, the warmest month would need to average 11 °C (52 °F) or higher for trees to be able to survive there).

In 1947, Holdridge improved on these schemes, by defining biotemperature: the mean annual temperature, where all temperatures below 0 °C are treated as 0 °C (because it makes no difference to plant life, being dormant). If the mean biotemperature is between 1.5 and 3 °C (34.7 and 37.4 °F), [7] Holdridge quantifies the climate as alpine.

Flora

Silky phacelia (Phacelia sericea, blooming) and spreading phlox (Phlox diffusa) are species of alpine regions of western North America. Phacelia sericea 4793.JPG
Silky phacelia ( Phacelia sericea , blooming) and spreading phlox ( Phlox diffusa ) are species of alpine regions of western North America.
Alpine flora at 11,500 feet (3500 m) on the Flat Tops plateau in the Colorado Rocky Mountains U.S.A Flat Tops tundra.jpg
Alpine flora at 11,500 feet (3500 m) on the Flat Tops plateau in the Colorado Rocky Mountains U.S.A

Since the habitat of alpine vegetation is subject to intense radiation, wind, cold, snow, and ice, it grows close to the ground and consists mainly of perennial grasses, sedges, and forbs. Perennial herbs (including grasses, sedges, and low woody or semi-woody shrubs) dominate the alpine landscape; they have much more root and rhizome biomass than that of shoots, leaves, and flowers. The roots and rhizomes not only function in water and nutrient absorption but also play a very important role in over-winter carbohydrate storage. Annual plants are rare in this ecosystem and usually are only a few inches tall, with weak root systems. [4] Other common plant life-forms include prostrate shrubs, graminoids forming tussocks, cushion plants, and cryptogams, such as bryophytes and lichens. [8]

Relative to lower elevation areas in the same region, alpine regions have a high rate of endemism and a high diversity of plant species. This taxonomic diversity can be attributed to geographical isolation, climate changes, glaciation, microhabitat differentiation, and different histories of migration or evolution or both. [8] These phenomena contribute to plant diversity by introducing new flora and favoring adaptations, both of new species and the dispersal of pre-existing species. [8]

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 or red-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. [9]

Alpine areas are unique because of the severity and complexity of their environmental conditions. Very small changes in topography – as small as 1 foot (0.3 m) or less – may mean the difference between a windswept area or an area of snow accumulation, changing the potential productivity and plant community drastically. Between these extremes of drought versus saturation, several intermediate environments may exist all within a few yards of each other, depending on topography, substrate, and climate. Alpine vegetation generally occurs in a mosaic of small patches with widely differing environmental conditions. Vegetation types vary from cushion and rosette plants on the ridges and in the rock crannies; to herbaceous and grassy vegetation along the slopes; dwarf shrubs with grasses and forbs below the melting snowdrifts; and sedges, grasses, low shrubs, and mosses in the bogs and along the brooks. [4]

An alpine mire in the Swiss Alps GlarusAlps.jpg
An alpine mire in the Swiss Alps

Alpine meadows form where sediments from the weathering of rocks has produced soils well-developed enough to support grasses and sedges. Non-flowering lichens cling to rocks and soil. Their enclosed algal cells can photosynthesize at any temperature above 0 °C (32 °F), and the outer fungal layers can absorb more than their own weight in water. 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, allowing exposed soil to blow away; recovery may take hundreds of years. [9]

Fauna

The Himalayan tahr Himalaja-Tahr.JPG
The Himalayan tahr

Because alpine tundra is located in various widely separated regions of the Earth, there is no animal species common to all areas of alpine tundra. Some animals of alpine tundra environments include the kea, marmot, mountain goat, Bighorn sheep, chinchilla, Himalayan tahr, yak, snow leopard, and pika.

See also

Related Research Articles

Tundra Biome where plant growth is hindered by cold temperatures

In physical geography, tundra is a type of biome where the tree growth is hindered by low temperatures and short growing seasons. The term tundra comes through Russian тундра from the Kildin Sámi word тӯндар meaning "uplands", "treeless mountain tract". Tundra vegetation is composed of dwarf shrubs, sedges, grasses, mosses, and lichens. Scattered trees grow in some tundra regions. The ecotone between the tundra and the forest is known as the tree line or timberline. The tundra soil is rich in nitrogen and phosphorus.

Grassland Area with vegetation dominated by grasses

Grasslands are areas where the vegetation is dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur naturally on all continents except Antarctica and are found in most ecoregions of the Earth. Furthermore, grasslands are one of the largest biomes on earth and dominate the landscape worldwide. They cover 31-43% of the Earth's land area. There are different types of grasslands: natural grasslands, semi-natural grasslands, and agricultural grasslands.

Great Basin Desert Desert in the western United States

The Great Basin Desert is part of the Great Basin between the Sierra Nevada and the Wasatch Range. The desert is a geographical region that largely overlaps the Great Basin shrub steppe defined by the World Wildlife Fund, and the Central Basin and Range ecoregion defined by the U.S. Environmental Protection Agency and United States Geological Survey. It is a temperate desert with hot, dry summers and snowy winters. The desert spans a large part of the state of Nevada, and extends into western Utah, eastern California, and Idaho. The desert is one of the four biologically defined deserts in North America, in addition to the Mojave, Sonoran, and Chihuahuan Deserts.

Tree line Edge of the habitat at which trees are capable of growing

The tree line is the edge of the habitat at which trees are capable of growing. It is found at high elevations and high latitudes. Beyond the tree line, trees cannot tolerate the environmental conditions. The tree line is sometimes distinguished from a lower timberline or forest line, which is the line below which trees form a forest with a closed canopy.

Alpine climate

Alpine climate is the typical weather (climate) for the regions above the tree line. This climate is also referred to as a mountain climate or highland climate.

Alpine plant Plants that grow at high elevation

Alpine plants are plants that grow in an alpine climate, which occurs at high elevation and above the tree line. There are many different plant species and taxon that grow as a plant community in these alpine tundra. These include perennial grasses, sedges, forbs, cushion plants, mosses, and lichens. Alpine plants are adapted to the harsh conditions of the alpine environment, which include low temperatures, dryness, ultraviolet radiation, wind, drought, poor nutritional soil, and a short growing season.

Andean Moorland High-altitude wet tundra in South America

PáramoAndino or Andean Moorland can refer to a variety of alpine tundra ecosystems located in the Andes Mountain Range, South America. Some ecologists describe the andean moorland broadly as "all high, tropical, montane vegetation above the continuous timberline". A more narrow term classifies the páramo according to its regional placement in the northern Andes of South America and adjacent southern Central America. The páramo is the ecosystem of the regions above the continuous forest line, yet below the permanent snowline. It is a "Neotropical high mountain biome with a vegetation composed mainly of giant rosette plants, shrubs and grasses". According to scientists, páramos may be "evolutionary hot spots" and among the fastest evolving regions on Earth.

Life zones of Peru

When the Spanish arrived, they divided Peru into three main regions: the coastal region, that is bounded by the Pacific Ocean; the highlands, that is located on the Andean Heights, and the jungle, that is located on the Amazonian Jungle. But Javier Pulgar Vidal (es), a geographer who studied the biogeographic reality of the Peruvian territory for a long time, proposed the creation of eight Natural Regions. In 1941, he presented his thesis "Las Ocho Regiones Naturales del Perú" at the III General Assembly of the Pan-American Institute of Geography and History.

Puna grassland

The puna grassland ecoregion, of the montane grasslands and shrublands biome, is found in the central Andes Mountains of South America. It is considered one of the eight Natural Regions in Peru, but extends south, across Bolivia, as far as northern Argentina and Chile. The term puna encompasses diverse ecosystems of the high Central Andes above 3200–3400 m.

Sierra Nevada subalpine zone

The Sierra Nevada subalpine zone refers to a biotic zone below treeline in the Sierra Nevada mountain range of California, United States. This subalpine zone is positioned between the upper montane zone at its lower limit, and tree line at its upper limit.

In the Arctic, the low tundra vegetation clothes a landscape of wide vistas, lit by the low-angle light characteristic of high latitudes. Much of the Arctic shows little impact from human activities, making it one of the few places on earth one can see intact ecosystems. Arctic plants are adapted to short, cold growing seasons. They have the ability to withstand extremely cold temperatures in the winter, but what is even more important is the ability to be able to function in limiting summer conditions.

Altitudinal zonation in mountainous regions describes the natural layering of ecosystems that occurs at distinct elevations due to varying environmental conditions. Temperature, humidity, soil composition, and solar radiation are important factors in determining altitudinal zones, which consequently support different vegetation and animal species. Altitudinal zonation was first hypothesized by geographer Alexander von Humboldt who noticed that temperature drops with increasing elevation. Zonation also occurs in intertidal and marine environments, as well as on shorelines and in wetlands. Scientist C. Hart Merriam observed that changes in vegetation and animals in altitudinal zones map onto changes expected with increased latitude in his concept of life zones. Today, altitudinal zonation represents a core concept in mountain research.

International Tundra Experiment

The International Tundra Experiment (ITEX) is a long-term international collaboration of researchers examining the responses of arctic and alpine plants and ecosystems to climate change. Researchers measure plant responses to standardized, small-scale passive warming, snow manipulations, and nutrient additions. Researchers use small open-top chambers (OTCs) to passively increase mean air temperature by 1-2 °C. The ITEX approach has been validated by tundra responses at the plot level. The network has published meta-analyses on plant phenology, growth, and reproduction, composition and abundance, and carbon flux.

The biogeoclimatic zones of British Columbia are units of a classification system used by the British Columbia Ministry of Forests for the Canadian province's fourteen different broad, climatic ecosystems. The classification system, termed Biogeoclimatic Ecosystem Classification, exists independently of other ecoregion systems, one created by the World Wildlife Fund and the other in use by Environment Canada, which is based on one created by the Commission for Environmental Cooperation (CEC) and also in use by the American Environmental Protection Agency (EPA). The system of biogeoclimatic ecosystem classification was partly created for the purpose of managing forestry resources, but is also in use by the British Columbia Ministry of Environment and Climate Change Strategy and other provincial agencies. A biogeoclimatic zone is defined as "a geographic area having similar patterns of energy flow, vegetation and soils as a result of a broadly homogenous macroclimate."

Ecology of the North Cascades Ecosystems of the Cascade mountain range in northern Washington state and southern British Columbia

The Ecology of the North Cascades is heavily influenced by the high elevation and rain shadow effects of the mountain range. The North Cascades is a section of the Cascade Range from the South Fork of the Snoqualmie River in Washington, United States, to the confluence of the Thompson and Fraser Rivers in British Columbia, Canada, where the range is officially called the Cascade Mountains but is usually referred to as the Canadian Cascades. The North Cascades Ecoregion is a Level III ecoregion in the Commission for Environmental Cooperation's classification system.

North American Arctic

The North American Arctic is composed of the northern portions of Alaska (USA), Northern Canada and Greenland. Major bodies of water include the Arctic Ocean, Hudson Bay, the Gulf of Alaska and North Atlantic Ocean. The North American Arctic lies above the Arctic Circle. It is part of the Arctic, which is the northernmost region on Earth. The western limit is the Seward Peninsula and the Bering Strait. The southern limit is the Arctic Circle latitude of 66° 33’N, which is the approximate limit of the midnight sun and the polar night.

Southland montane grasslands

The Southland montane grasslands, also known as the South Island montane grasslands, is a montane grasslands and shrublands ecoregion on New Zealand’s South Island. The ecoregion covers the middle portion of the Southern Alps, and includes extensive alpine grasslands, fellfields, and montane forests.

Montane ecosystems

Montane ecosystems are found on the slopes of mountains. The alpine climate in these regions strongly affects the ecosystem because temperatures fall 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. 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. Due to the unique climate conditions of montane ecosystems, they contain increased numbers of endemic species. Montane ecosystems also exhibit variation in ecosystem services, which include carbon storage and water supply.

Northern Andean páramo

The Northern Andean páramo (NT1006) is an ecoregion containing páramo vegetation above the treeline in the Andes of Colombia and Ecuador. In the past, when the climate was cooler, the treeline and the páramo units were lower and the units were connected. During the present warmer Holocene epoch the páramos have migrated uphill, shrinking and becoming isolated. They contain many rare or endangered species, some of them restricted to a narrow area of one mountain or mountain range. The ecoregion is relatively well preserved, but faces threats from over-grazing and farming.

Altai alpine meadow and tundra

The Altai alpine meadow and tundra ecoregion is a terrestrial ecoregion covering the higher elevation of the Altai Mountains at the center of the "X" formed by the borders separating Russia, Kazakhstan, China, and Mongolia. The mountain peaks are the farthest north in Central Asia, separating the plains of Siberia to the north from the hot, dry deserts to the south. Altitudes above 2,400 meters display characteristics of tundra, with patches of alpine meadows and some trees immediately below the treeline. The ecoregion is in the montane grasslands and shrublands biome, and the Palearctic realm, with a humid continental climate. It covers an area of 90,132 square kilometres (34,800 sq mi).

References

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  3. "South Island montane grasslands". Terrestrial Ecoregions. World Wildlife Fund.
  4. 1 2 3 4 PD-icon.svg This article incorporates  public domain material from the Bureau of Land Management document: "Grassland Habitat Group" (PDF). Archived from the original (PDF) on 2008-07-24.
  5. Körner, Ch (1998). "A re-assessment of high elevation treeline positions and their explanation" (PDF). Oecologia. 115 (4): 445–459. Bibcode:1998Oecol.115..445K. CiteSeerX   10.1.1.454.8501 . doi:10.1007/s004420050540. PMID   28308263.
  6. Blyth, S; Groombridge, B.; Lysenko, I; Miles, L.; Newton, A (2002). Mountain Watch: environmental change & sustainable development in mountains (PDF). UNEP World Conservation Monitoring Centre. ISBN   978-1-899628-20-9. Archived from the original (PDF) on 2013-10-14.
  7. "Biodiversity lectures and practicals of Allan Jones". dundee.ac.uk. Archived from the original on 2007-09-29.
  8. 1 2 3 Körner, Christian (2003). Alpine Plant Life: Functional Plant Ecology of High Mountain Ecosystems. Berlin: Springer. pp. 9–18. doi:10.1007/978-3-642-18970-8. ISBN   978-3-540-00347-2.
  9. 1 2 PD-icon.svg This article incorporates  public domain material from the National Park Service document: "Rocky Mountain National Park: Alpine Tundra Ecosystem".