The Alpine Biome

 

Climate:  

Alpine biomes by their nature do not fit into a simple climatic scheme.  In general, as one ascends a mountain, temperature drops by about  10 C for every 1000 meters in altitude gained (a suspiciously round number!).  This means that if you start at sea level at 30 C and go up 1,000 meters the temperature will be 20 C; at the top of a 3,000 meter mountain the temperature will be 0 C.  This the only thing you can say about the climate in alpine regions is that it is colder than one would expect at sea level at the same latitude.  Rainfall also varies considerably; as the rising air cools it loses the ability to retain moisture and clouds form, with the result of increasing precipitation on the side of a mountain exposed to winds.  On the other side, the descending air (already dried by its trip over the mountains) warms and removes moisture from the ground - this is one of the driving forces behind the deserts in the American Southwest.

In these web pages the alpine "biome" will be considered to be the upper altitudes of mountains, where cooler climates give rise to communities which resemble (but do not duplicate) the taiga, tundra and ice biomes.

World Distribution:

As you can see on the map above, alpine conditions are found in the great mountain ranges of the world.  The map above is somewhat parochial as the author is more familiar with the mountains in the American west than in other parts of the world.  Still, the global mountain ranges that are parts of the alpine biome include the Rockies, Sierra, and Cascade mountains in North America, the Andes in South America, the Himalayas in Asia, the Alps and Pyrenees in Europe, and the Rift Mountains of Africa.  There are other mountain regions to be sure, but they are not shown on the map above either because they are too small to show up at this resolution, are too low to support tundra or ice conditions,  or occur so far north that they are effectively subsumed into the rock and ice or tundra biomes.  You might want to explore mountain ranges further at this site:

http://www.peakware.com/

Most of the mountain ranges are associated, of course, with plate tectonics.

Indicator Plant Species:

Coniferous Forest, Yosemite National Park

Coniferous Forest, Yosemite National Park

Flowers, Mt. St. Helens, Washington

Flowers, Mt. St. Helens, Washington

As one moves up a mountain, the first indication one has that you are entering an alpine area is the appearance of coniferous trees.  Able to shed snow easily, and retaining photosynthetic needles that are able to start photosynthesis quickly as soon as the temperature exceeds the freezing point, conifers such as firs and pines (right) are ideally adapted for cool environments.

Further up the mountain a tree line occurs; above this point climactic conditions are too harsh for trees to grow, and a tundra-like plant community develops.  Plants here include various wildflowers (below) , mosses, succulents (adapted to the harsh dry conditions that often prevail), and other low-growing plants (below right). Lichens can also be important.

Fir (left) and Pine (right)

Fir (left) and Pine (right)

Wildflowers, Mt. Rainier, Washington

Wildflowers, Mt. Rainier, Washington

Moss, Yellowstone National Park

Moss, Yellowstone National Park

 

 

Below:  Lichens (left) are important in many alpine areas.  At lower levels, they may grow extensively on trees and even function as a food source in the winter.  The snowflower, below right, is very interesting.   It is saprophytic.  It has no above-ground structures except for the flowers.  Instead, it has underground roots which feed on decaying roots of trees killed by fires.  These flowers appear in areas where a number of trees have been killed by fires.  This individual was photographed in Yosemite National Park.

 

Lichen

Lichen

Snowflower

Snowflower

Indicator Animal Species:

Steller's Jay Cyanocitta stelleri, Mt. Rainier

Steller's Jay Cyanocitta stelleri, Mt. Rainier

Chickaree (Tamiasciurus douglasi), Mt Rainier

Chickaree (Tamiasciurus douglasi), Mt Rainier

Again, many of the animal species one encounters in the mountains are similar to those that would be found in taiga or tundra habitats.  Others, however, have specific adaptations to the mountains.  Steller's jays (above) and the Chickaree (right) are two species one often encounters in coniferous forests in the western mountains of the United States.  

The hoary marmot, below right, is a montane species as compared to the western golden marmot which is found at lower elevations.    A close relative of the groundhog found in the eastern United States, the hoary marmot makes its burrows among the rocky fields at high elevations.

Grouse of various species may also be encountered in the western US mountains, as this ruffed grouse (inset) was in Grand Teton National Park.

Mountain goats, below, have a host of adaptations that allow them to live on the most precarious of cliffs.  Chief among those adaptations are special pads on their hooves which are both cushioned (to absorb the shock of jumping from rock to rock) and slip resistant. 

 

Chickaree (Tamiasciurus douglasi), Mt Rainier

Chickaree (Tamiasciurus douglasi), Mt Rainier

Mountain Goat (Oreamnos americanus), Glacier National Park

Mountain Goat (Oreamnos americanus), Glacier National Park

Hoary marmot (Marmota caligata), Glacier National Park

Hoary marmot (Marmota caligata), Glacier National Park

 

Clark's nutcracker Nucifraga columbiana - Mt. Rainier, Washington

Clark's nutcracker Nucifraga columbiana - Mt. Rainier, Washington

Clark's nutcracker is normally found at the higher elevations on the mountains, getting up towards timberline where they feed on the seeds of pines.  The long beak is used to remove the seeds from the cones.  The seeds are then cached on the ground, much in the same way a squirrel caches nuts.  Amazingly, the birds are able to find the seeds through the winter.  The Clark of Clark's Nutcracker is  also the Clark of Lewis & Clark, William Clark found the species on the famous expedition.

Ecological Notes:

In very high mountains, some species may require physiological adaptations to help them survive.  Humans, for instance, will increase the oxygen-carrying capacity of their blood (by increasing the number of red blood cells, among other responses).  There are also adaptations for surviving the cold; these are usually similar to the adaptations seen in other species living in cold climates closer to the poles.  Mountaintop plants often have adaptations which enable them to survive the very dry conditions that prevail there (water runs off mountaintops quickly, the soil may have little ability to hold water, and the air may be dry with a constant wind).  Many high mountains plants are succulents, with water stored in thick leaves; others grow much closer to the ground (as compared to related plants from lower altitudes), this keeps them out of the wind.  Flagging; where tree limbs only grow with the prevailing winds, is a oft-seen phenomenon on mountaintops (right).

Mountain areas have been used extensively to support studies of island ecology, in parts because mountains act as islands of habitat in a "sea" of very different habitats.  Mountain species are thus very isolated and subject to different ecological pressures.  

Threats:

Ruffed Grouse, Grand Teton National Park

Mountains in general have been fairly safe from most forms of development; indeed, one criticism of the American National Park system is that it protects too much mountain habitat, with lots of nice views but relatively little biomass.  Such parks are relatively easy to create because there are few human uses for such areas.  In addition, particularly in the west, mountain regions are also deemed worthy of protection because of their value as a watershed; the water from the snowmelt alone makes the mountaintops where the snowpack lies a relatively valuable piece of property.

 

There are threats, however.  One of the photos below shows a ski development; in general ski slopes are a threat to mountain habitats.  Airborne pollution, including acid rain, also threatens alpine areas. Acid rain has sterilized many mountain lakes, which often have little buffering capacity.  Global warming may be the greatest threat, however.  In addition to the loss of snow pack and its vital water, many mountains are refuges for cold-loving species which used to be found at much lower latitudes during periods of glacial expansion. As the glaciers retreated, these species were often forced to move up mountains to find suitable cold habitats.  As the Earth warms, they may continue to move upwards, but because of the pointy shape of mountains there is less habitat at the higher altitudes, and once you reach the top of the mountain, where do you go?

flagging

Flagging - the wind is coming from the right; the trees branches grow to the left.

 

Tour:

Near Mt. Rainier, Washington

Near Mt. Rainier, Washington

Big Mountain, Montana

Big Mountain, Montana

Alpine habitats encompass a wide variety, as seen in these images.  Above, a rocky spire has little soil to support tree life; what little soil is formed in freeze-thaw cycles quickly drops off the sheer rock face.  In contrast, the gentler slope of the summit of Big Mountain in Montana would probably support trees had they not been cleared for a ski facility.  

In Yosemite National Park (right) the granite of Half-Dome sticks out above the coniferous forests, which themselves are patchy on the very rocky ground.  Below, a view from a high vantage point in Yosemite shows a more continuous coniferous forest lapping up to the steep (and high) slopes of the surrounding Sierra Nevada mountains.  These high slopes - either because they are too steep; too rocky; or too cold, windswept and dry - exhibit a definite treeline above which no trees grow.  

To the right, below, steep slopes of talus (big chunks) and scree (small chunks) line a canyon gouged by glacial action and meltwater.  Clearly the elevation here is not the issue for the trees as they are bountiful at the altitude from whence the picture was taken; rather, stability of the slopes may be the factor preventing tree growth.

Yosemite National Park

Yosemite National Park

Yosemite National Park

Yosemite National Park

Near Mt. Rainier, Washington

Near Mt. Rainier, Washington

Glacier National Park

Glacier National Park

Glacier National Park

Glacier National Park

MacDonald Lake, Glacier National Park

MacDonald Lake, Glacier National Park

High mountains (above) may be perpetually covered with snow and ice (and glaciers) throughout the year and thus resemble the arctic.  Global warming may be changing this, however, as the glaciers begin to melt and retreat (above left).  The mountains in the photo to the left show snow only at the peaks; this picture was taken in June at a time when traditionally the snowline on the mountains was lower.  

In the lower left photo wildflowers typical of an alpine tundra Johnston Ridge across from Mt. St. Helens; it would be tempting to conclude that at this altitude such a tundra-like habitat was the norm - until one realized that this ridge was covered by a coniferous forest until the 1980 eruption.  As of the time this photo was taken in 2004, the forest had not been able to regenerate.

Below, the Appalachian Mountains rarely peak high enough to show a treeline, but they do bring taiga-like plant and animal species down into lower latitudes than they normally would be seen.  During past periods of glaciation, northern species were common much further south - as the glaciers retreated, the northern species moved back north with the glaciers, although some were able to persist at the higher elevations in the mountains.

Wildflowers, Mt. St. Helens

Wildflowers, Mt. St. Helens

Appalachian Mountains, West Virginia

Appalachian Mountains, West Virginia

Aspens

Aspens

Above: Aspens are often found in the zone where deciduous trees transition into conifers in the mountains.  If you are hiking up a mountain in the west, the sight of aspens is a sign that the coniferous forest will start soon.

Below:  A mountain meadow in Glacier National Park.  Such open areas may appear for several reasons - fires, avalanches, storms, wetlands, serpentine soils, etc. may all contribute to the development of grassy areas without trees.

Mountain Meadow, Glacier National Park

Mountain Meadow, Glacier National Park

 

Olympic Mountains, Olympic Peninsula, Washington

Olympic Mountains, Olympic Peninsula, Washington

Olympic Mountains, Olympic Peninsula, Washington

Olympic Mountains, Olympic Peninsula, Washington

These views show some of the higher peaks in the Olympic Range on the Olympic Peninsula of Washington State.  Snow and ice sculpt the high elevations of these relatively young mountains.

Below, snow and ice are still actively sculpting Mt. Rainier, a dormant volcano looming over the city of Seattle.  

Olympic Mountains, Olympic Peninsula, Washington

Olympic Mountains, Olympic Peninsula, Washington

Mt. Rainier, Washington

Mt. Rainier, Washington

Mt. Rainier, Washington

 Mt. Rainier, Washington

Rocky Mountains, Colorado

Rocky Mountains, Colorado

Mt. Rainier, Washington

Mt. Rainier, Washington

Rocky Mountains, Montana

Rocky Mountains, Montana

In these photos one catches a glimpse of the role of snow and ice in the mountains.  The aerial view above left is of the Rocky Mountains in Colorado.  This picture is disturbing as it was taken in early June, 2004, a time when one would expect to see a much greater snow pack.  The snow pack, as it gradually melts over the course of the summer, supplies fresh water to the aquatic ecosystems of the mountains - and to the deserts and cities beyond.  A thin snow pack will not provide enough water, and a snow pack that melts too quickly will overwhelm storage structures such as dams and leave the rivers dry in the later summer.  The skimpy snow pack seen here is the result of a long-term western drought and the effects of global warming.  

Above right and to the left:  At a closer approach, one can see how the melting snow fills rivers and even small cirque lakes carved out of the mountainsides by mini-glaciers.  These small lakes (left) are a unique alpine habitat.

Below left, snowpoles about 15 feet high illustrate how thick the snow pack may be at the end of winter, instead of the beginning of winter, such as the September day this photo was taken.  These poles just outside of Yellowstone National Park will help the crews find and open the road the next June.  

Below, mountains make their own weather.  As air is pushed over this high peak north of Vancouver, British Columbia it cools; the water in it condenses, and a snowstorm erupts in June.

Rocky Mountains, Montana

Rocky Mountains, Montana

Cascade Range, near Vancouver, British Columbia

Cascade Range, near Vancouver, British Columbia

Steller's Jay Cyanocitta stelleri, Mt. Rainier

Steller's Jay, Cyanocitta stelleri, Mt. Rainier

Yosemite Valley, Yosemite National Park

Yosemite Valley, Yosemite National Park

Above - the incredible Yosemite Valley, scooped out of the granite bedrock by a glacier, leaving streams hanging to fall thousands of feet in spectacular waterfalls.

 

Grand Teton Mountains, Wyoming

Grand Teton Mountains, Wyoming

 wildflowers, Mt Rainier

 

See Also - Boreal Forests

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