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. [1] 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 and 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. [2]
As elevation increases, the climate becomes cooler, due to a decrease in atmospheric pressure and the adiabatic cooling of airmasses. [3] In middle 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° of latitude) 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 causes life 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 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). [5]
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. [6] 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. [7]
Climates with biotemperatures below 1.5 °C (35 °F) tend to consist purely of rock and ice. [5]
Montane forests occur between the submontane zone and the subalpine zone. The elevation at which one habitat changes to another varies across the globe, particularly by latitude. The upper limit of montane forests, the tree line, is often marked by a change to hardier species that occur in less dense stands. [8] For example, in the Sierra Nevada of California, the montane forest has dense stands of lodgepole pine and red fir, while the Sierra Nevada subalpine zone contains sparse stands of whitebark pine. [9]
The lower bound of the montane zone may be a "lower timberline" that separates the montane forest from drier steppe or desert region. [8]
Montane forests differ from lowland forests in the same area. [10] 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. [11] Humans can disturb montane forests through forestry and agriculture. [10] On isolated mountains, montane forests surrounded by treeless dry regions are typical "sky island" ecosystems. [12]
Montane forests in temperate climate are typically one of temperate coniferous forest or temperate broadleaf and mixed forest, forest types that are well known from Europe and northeastern North America. Montane forests outside Europe tend to be more species-rich, because Europe during the Pleistocene offered smaller-area refugia from the glaciers. [13]
Montane forests in temperate climate occur in Europe (the Alps, Carpathians, and more), [14] in North America (e.g.,Appalachians, Rocky Mountains, Cascade Range, and Sierra Nevada), [15] South America, [16] New Zealand, [17] and the Himalayas.
Climate change is predicted to affect temperate montane forests. For example, in the Pacific Northwest of North America, climate change may cause "potential reduced snowpack, higher levels of evapotranspiration, increased summer drought" which will negatively affect montane wetlands. [18]
Montane forests in Mediterranean 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. [19] 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 are often evergreen, e.g. evergreen oak.[ citation needed ]
This type of forest is found in the Mediterranean Basin, North Africa, Mexico and the southwestern US, Iran, Pakistan and Afghanistan.[ citation needed ]
In the tropics, montane forests can consist of broadleaf forest in addition to coniferous forest. One example of a tropical montane forest is a cloud forest, which gains its moisture from clouds and fog. [20] [21] [22] Cloud forests often exhibit an abundance of mosses covering the ground and vegetation, in which case they are also referred to as mossy forests. Mossy forests usually develop on the saddles of mountains, where moisture introduced by settling clouds is more effectively retained. [23] 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). [24]
Tropical montane forests might exhibit high sensitivity to climate change. [25] [26] 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 affect biodiversity 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 the Monteverde cloud forest in Costa Rica. [27] [28]
The subalpine zone is the biotic zone immediately below the tree line around the world. In tropical regions of Southeast Asia the tree line may be above 4,000 m (13,000 ft), [29] whereas in Scotland it may be as low as 450 m (1,480 ft). [30] Species that occur in this zone depend on the location of the zone on the Earth; for example, Pinus mugo (scrub mountain pine) occurs in Europe, [31] the snow gum is found in Australia, [32] and the subalpine larch, mountain hemlock, and subalpine fir occur in western North America. [33]
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]
Meadows may be found in the subalpine zone. Tuolumne Meadows in the Sierra Nevada of California, is an example of a subalpine meadow. [35]
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 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 perennial grasses, sedges, and forbs. Annual plants are rare in this ecosystem and usually are only a few inches tall, with weak root systems. [36] Other common plant life-forms include prostrate shrubs; tussock-forming graminoids; and cryptogams, such as bryophytes and lichens. [6] : 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 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. [37] Non-flowering lichens cling to rocks and soil. Their enclosed algal cells can photosynthesize at temperatures as low as −10 °C (14 °F), [38] and the outer fungal layers can absorb more than their own weight in water. [39]
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. [37]
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 biome by the World 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 and endemic plants which evolved in response to the cool, wet climate and abundant sunlight.[ citation needed ]
The most extensive montane grasslands and shrublands occur in the Neotropical páramo of the Andes Mountains. This biome also occurs in the mountains of east and central Africa, Mount Kinabalu of Borneo, the highest elevations of the Western Ghats in South India and the Central Highlands of New Guinea. A unique feature of many wet tropical montane regions is the presence of giant rosette plants from a variety of plant families, such as Lobelia (Afrotropic), Puya (Neotropic), Cyathea (New Guinea), and Argyroxiphium (Hawaii).[ citation needed ]
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.[ citation needed ]
A biome is a distinct geographical region with specific climate, vegetation, and animal life. It consists of a biological community that has formed in response to its physical environment and regional climate. Biomes may span more than one continent. A biome encompasses multiple ecosystems within its boundaries. It can also comprise a variety of habitats.
In physical geography, tundra is a type of biome where tree growth is hindered by frigid temperatures and short growing seasons. There are three regions and associated types of tundra: Arctic tundra, alpine tundra, and Antarctic tundra.
A cloud forest, also called a water forest, primas forest, or tropical montane cloud forest, is a generally tropical or subtropical, evergreen, montane, moist forest characterized by a persistent, frequent or seasonal low-level cloud cover, usually at the canopy level, formally described in the International Cloud Atlas (2017) as silvagenitus. Cloud forests often exhibit an abundance of mosses covering the ground and vegetation, in which case they are also referred to as mossy forests. Mossy forests usually develop on the saddles of mountains, where moisture introduced by settling clouds is more effectively retained.
A grassland is an area 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. There are different types of grasslands: natural grasslands, semi-natural grasslands, and agricultural grasslands. They cover 31–69% of the Earth's land area.
Montane grasslands and shrublands are a biome defined by the World Wildlife Fund. The biome includes high elevation grasslands and shrublands around the world. The term "montane" in the name of the biome refers to "high elevation", rather than the ecological term that denotes the region below the treeline.
Alpine tundra is a type of natural region or biome that does not contain trees because it is at high elevation, with an associated harsh climate. 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.
The tree line is the edge of a habitat at which trees are capable of growing and beyond which they are not. 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, which is the line below which trees form a forest with a closed canopy.
Alpine climate is the typical climate for elevations above the tree line, where trees fail to grow due to cold. This climate is also referred to as a mountain climate or highland climate.
The ecology of California can be understood by dividing the state into a number of ecoregions, which contain distinct ecological communities of plants and animals in a contiguous region. The ecoregions of California can be grouped into four major groups: desert ecoregions, Mediterranean ecoregions, forested mountains, and coastal forests.
The life zone concept was developed by C. Hart Merriam in 1889 as a means of describing 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.
The ecology of the Sierra Nevada, located in the U.S. states of California and Nevada, is diverse and complex. The combination of climate, topography, moisture, and soils influences the distribution of ecological communities across an elevation gradient from 500 to 14,500 feet. Biotic zones range from scrub and chaparral communities at lower elevations, to subalpine forests and alpine meadows at the higher elevations. Particular ecoregions that follow elevation contours are often described as a series of belts that follow the length of the Sierra Nevada. There are many hiking trails, paved and unpaved roads, and vast public lands in the Sierra Nevada for exploring the many different biomes and ecosystems.
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 taxa 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.
Páramo may refer to a variety of alpine tundra ecosystems located in the Andes Mountain Range, South America. Some ecologists describe the páramo broadly as "all high, tropical, montane vegetation above the continuous timberline". A narrower 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", meaning that it's among the fastest evolving regions on Earth.
The Scandinavian montane birch forests and grasslands is defined by the World Wildlife Fund (WWF) as a terrestrial tundra ecoregion in Norway, Sweden, and Finland.
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.
Last Glacial Maximum refugia were places (refugia) in which humans and other species survived during the Last Glacial Period, around 25,000 to 18,000 years ago. Glacial refugia are areas that climate changes were not as severe, and where species could recolonize after deglaciation.
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.
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.
Vegetation classification is the process of classifying and mapping the vegetation over an area of the Earth's surface. Vegetation classification is often performed by state based agencies as part of land use, resource and environmental management. Many different methods of vegetation classification have been used. In general, there has been a shift from structural classification used by forestry for the mapping of timber resources, to floristic community mapping for biodiversity management. Whereas older forestry-based schemes considered factors such as height, species and density of the woody canopy, floristic community mapping shifts the emphasis onto ecological factors such as climate, soil type and floristic associations. Classification mapping is usually now done using geographic information systems (GIS) software.