Tundra

How Tundra Develops

Kinds of Tundras

Climate

Geography of Tundras

Plant Life

Animal Life

Human Life

The Food Web

Spotlight on Tundras

For More Information

In the northern lands close to the Arctic, and on the upper slopes of high mountains all over the world, a unique biome called the tundra is found. The word tundra comes from a Finnish word tunturia, which means barren land. In this cold, dry, windy region where trees cannot grow, the often bare and rocky ground supports only hardy, low-growing plants, such as mosses, sedges, heaths, and plantlike lichens (LY-kens), which give it a greenish-brown color. During the brief spring and summer, flowers burst into bloom with the warmth of the sun, dotting the landscape with color.

Tundra covers about 20 percent of Earth’s surface. Almost all tundra is located in the Northern Hemisphere (the half of Earth above the equator); small areas do exist in Antarctica in the Southern Hemisphere. Antarctica is much colder than the Arctic and the ground is usually covered by ice. Conditions are seldom right for tundra to form there.

The tundra is not an environment with high biodiversity. (An area with high biodiversity supports a wide variety of plants and animals.) Only a few species of plants and animals live in the tundra, but those few, such as lichens and mosquitoes, are found in great numbers.

The tundra may seem bleak and unfriendly, but it can be a place of eerie beauty, especially in the Arctic during the winter. Winter nights last for weeks and are often lit up by the blue, red, and green colors of the Aurora Borealis, or northern lights. The Aurora Borealis occurs when energy-charged particles from the sun enter Earth’s atmosphere and create flashes of light. The Arctic is called the Land of the Midnight Sun because, during the summer, the sun never sets below the horizon and daylight lasts for twenty-four hours.

How Tundra Develops

Tundra forms primarily because of climate. In the Arctic, winters are long and cold, and summers are short and cool. This allows limited plant growth. On high mountains, tundra forms when the location is right to produce the necessary climate.

The lack of soil in a tundra region may be due to erosion (wearing away) from wind and rain. During the Ice Ages more than 10,000 years ago, glaciers scraped away any soil, leaving only bare rock.

Kinds of Tundras

There are two types of tundra: Arctic and alpine. Arctic tundra is found near the Arctic Circle. Alpine tundra forms on mountaintops where the proper conditions exist.

Arctic tundra

Several characteristics are typical of Arctic tundra. One is the polar climate, which has an average July temperature of not more than 50°F (10°C). Arctic tundra is far from the equator. Sunlight hits Earth here at an angle and must pass through more atmosphere. This means the sunlight that reaches the soil contains less energy per square foot (square meter) than at the equator.

Another characteristic of the Arctic tundra is a deep layer of permanently frozen ground called permafrost. Generally, fewer than 18 inches (45 centimeters) of tundra soil thaws during the cool summer. Below that the ground remains frozen. Water from melting snow cannot drain into

the frozen ground, and little evaporates in the cool summer air. As a result, the water becomes trapped on the surface.

Arctic tundra is found on all three northern continents close to or above the Arctic Circle and near the Arctic Ocean. In Asia, Arctic tundra is found in the part of Russia known as Siberia. In Europe, it is found in northern Scandinavia, which includes the countries of Norway, Sweden, and Finland. In North America, Arctic tundra is found in northern Alaska and Canada. Some Arctic tundra is located on islands, such as Greenland and Iceland.

Alpine tundra

Alpine tundra is found at the tops of mountains above the timberline, the point above which trees cannot grow. The timberline and tundra are found at different elevations (heights) in different mountain ranges. The farther the mountains are from the equator, the lower the elevation needed for tundra to form.

Compared to Arctic tundra, alpine tundra gets more rain and its soil drains better because of the sloping terrain. It also gets more sunlight because it is found at lower latitudes (a distance north or south of the equator, measured in degrees) where day and night are more equal in length than in the Arctic. Usually, there is no lower layer of permafrost in alpine tundra.

Alpine tundra is found in the Rocky, Cascade, and Sierra Mountains in North America, the Andes Mountains in South America, the Alps and Pyrenees in Europe, and the Himalayas in Asia.

Storms on the Sun

The Aurora Borealis, or Northern Lights, occur when there are “storms” on the sun. These storms shoot out streams of energy-charged particles called electrons. When the electrons enter Earth’s atmosphere and collide with each other, a flash of light occurs. The magnificent Aurora Borealis is created when billions of these collisions occur at the same time.

Climate

Both Arctic and alpine tundra have very cold climates. Variations in temperature ranges may occur because of location. Arctic tundra located high above sea level (the average height of the sea) has a colder climate. If tundra is found near the coast, ocean currents can affect the temperature. For example, the North Atlantic Drift, a warm ocean current, warms the coast of northern Scandinavia. The coast of northeastern Canada is colder due to the influence of the Labrador Current, an icy current that mixes with the warmer waters. Arctic tundra is windy, with winds ranging between 30 to 60 miles (48 to 97 kilometers) per hour.

Unlike Arctic tundra, alpine tundra has a more moderate climate that varies with latitude and altitude. The farther away from the equator, the colder the temperature becomes. The higher the altitude, the colder and

windier the climate. At 15,000 feet (4,500 meters) above sea level, the climate changes as much as if it were located 10° latitude farther north. High altitude also means that the atmosphere is thin, which results in little oxygen present in the air.

Arctic Heat Wave

Sometimes the weather can become quite warm during summer on the Canadian tundra, warm enough for people to swim in the Arctic Ocean. In 1989 the temperature rose above 90°F (32°C) at Coppermine in the Northwest Territories. These temperature increases are caused by warmer water brought into the Arctic Ocean by northward-moving currents, such as the Irminger current. This current is a branch of the Gulf Stream, which is a warm ocean current that begins in the Gulf of Mexico.

Temperature

The Arctic tundra is one of the driest and coldest biomes on Earth. It is generally described as a cold desert. January temperatures average from –4° to –22°F (–20° to –30°C). In Siberia, an extremely cold area in north central Asia, winter temperatures may drop to –40°F (–30°C) or lower. Scandinavian tundra is relatively warm, and the winter temperatures may average 18°F (–8°C). Average arctic temperatures in summer range from 38° to 50°F (3.3° to 10°C). Although daytime temperatures above 90°F (32°C) have been recorded, normally the average does not rise much above 50°F (10°C) because temperatures drop significantly in the evenings.

Antarctica’s small tundra region is even colder, with an average annual inland temperature of –70°F (–56°C).

Alpine tundra is cold, but temperatures are more moderate than in the Arctic. Elevation affects the temperature in an alpine tundra, and mountains have been described as “open windows letting the heat out.” Scientists estimate that for every 1,000 feet (305 meters) in height, the temperature drops 3.6°F (–15.8°C).

Winter temperatures in an alpine tundra rarely fall below 0°F (–18°C) and summers are cool. The average annual temperature in the Peruvian mountains seldom falls below 50°F (10°C). On Alaskan mountains, temperatures in January average about 8°F (–13°C) and almost 47°F (8°C) in July.

Precipitation

Arctic tundra is similar to a cold desert in that it receives little precipitation (rain, snow, or sleet), usually fewer than 10 inches (25 centimeters) annually. Most precipitation falls as snow in winter.

Alpine tundra receives more rain than Arctic tundra, but the water runs rapidly off the mountain slope, leaving any dry soil to blow away in the wind.

Geography of Tundras

The excessively cold temperatures affect the geography of the tundra.

Landforms

In Arctic tundra, water trapped in the top layer of soil does strange things to the landscape. The water freezes each winter, and the ice melts each summer. When water freezes, it expands (takes up more space). When ice melts, it contracts (shrinks). This yearly expansion and contraction cracks and breaks rocks, creating hills, valleys, and other physical features.

A pingo is a small circular or oval hill formed when a pool of water under the ground freezes and forces the soil up and out. The hill may grow a few inches taller every year. Some pingos are as high as 300 feet (90 meters) and more than half a mile (800 meters) wide. Stone circles are formed by piles of rocks that have been moved into a more or less circular shape by the expansion of freezing water.

Polygons are cracks in the ground that take on geometric shapes because of the freezing and thawing action. If the soil is rocky, the rocks can be pushed up through the cracks, making the geometric shapes even more distinct.

Irregularly shaped ridges, called hummocks or hammocks, are formed when large blocks of ice meet and one slides over the top of the other. When the ice melts, the ground is uneven. Their heights range from 65 to 100 feet (20 to 30 meters).

Areas of bare, rock-covered ground on alpine tundra are called fell-fields. They are often formed when rock and soil slide down a slope.

Elevation

Most of the low, rolling plains of the Arctic tundra are located about 1,000 feet (300 meters) above sea level, whereas alpine tundra is found high on mountains above the tree line. In northern latitudes, close to the Arctic Circle, arctic tundra may begin at about 4,000 feet (1,200 meters) above sea level. In more southern mountains, alpine tundra usually begins around 12,000 feet (3,657 meters) above sea level.

Soil

The soil in Arctic tundra has two layers. The surface layer is called the active layer because it freezes in winter and thaws when the weather warms up. This layer is shallow, its depth ranging from about 10 inches to 3 feet (25 centimeters to 1 meter). About 15 percent of the active layer is well drained because it is located on stony or gravelly material, on slopes,

and in elevated areas. The remaining 85 percent of the active layer is usually poorly drained and remains wet.

The lower, or inactive, layer of soil stays frozen throughout the year and is called permafrost. Permafrost prevents the water captured in the active layer of soil from draining away. Made of such materials as gravel, bedrock, clay, or silt, permafrost reaches depths of 300 to almost 2,000 feet (90 to 609 meters). In Russia on the Taimyr Peninsula, permafrost goes very deep, reaching 1,968 feet (600 meters), whereas permafrost on tundra near Barrow, Alaska, descends to only 984 feet (300 meters).

Tundra soil is generally poor in nutrients, such as nitrogen and phosphorous. In some areas where animal droppings are plentiful and fertilize the soil, vegetation is lush. Near the southern edge of the Arctic tundra, for example, the soil can be boggy. Bog soil contains little oxygen, is acidic, and is low in nutrients and minerals.

Treasures in the Ice

The remains of plants and animals millions of years old have been discovered in tundra permafrost. Tree stumps found on Canadian tundra could still be burned for fuel.

The bodies of many mammoths have been perfectly preserved in the Siberian tundra. These large animals, now extinct, are related to modern-day elephants. In the early 1900s, a mammoth was discovered with its head sticking out of a bank of the Berezovka River. Although wolves had eaten part of his head, its tongue and part of its mouth were still preserved. In its mouth, between its teeth, were the remains of the sedge and buttercups it had been eating. Both of these plants still grow on the tundra.

Alpine tundra rarely has a permafrost layer, but the soil does freeze and thaw as in the Arctic. When permafrost does occur in alpine tundra, it is at higher elevations where temperatures are colder and in areas where mud, rock, and snow slides are common.

Similar to arctic soil, alpine soil is stratified (arranged in layers). Alpine soil has good drainage because of the sloping terrain. However, fierce winds may dry it out and blow it away. Some alpine regions are covered with material so weathered and thin it cannot be classified as soil.

Water sources

Melting snow in Arctic tundra has nowhere to go since it cannot sink into the ground, and temperatures never get warm enough for it to evaporate. As a result, in summer the tundra is covered with marshes, lakes, bogs, and streams. Marshes are a type of wetland characterized by poorly drained soil and plant life dominated

by nonwoody plants. Bogs are a type of wetland that has wet, spongy, acidic soil, called peat.

Thermokarst, or thaw lakes, are shallow bodies of water unique to Arctic tundra and formed by melting ground ice. Permanent rivers flow into tundra, like the Mackenzie and Yukon rivers in Alaska, and the Lena, Ob, and Yenisei in Siberia. These rivers are partially or completely covered by ice for about six months of the year.

In alpine tundra, water from melting snow and glaciers usually runs off the slopes. In areas where depressions in the ground occur, ponds and marshes form. Mountain streams, which flow during the five warm months of the year, are formed by surface runoff and from springs.

Nature’s Hothouses

Since the tundra growing season is so short, some plants get a head start by making use of hothouses formed by the sun. Darker colors absorb more heat, so the sun melts some snow close to the dark soil. This forms small caves in the snow. The floor is the soil and the roof is a dome of snow that remains frozen. Poppies and saxifrages grow well in these miniature hothouses because the air inside is warmer than the outside air.

Plant Life

Permafrost and the yearly freezing and thawing, break up plant roots and make it impossible for trees and other tall plants to survive on Arctic tundra. Plant growth in the alpine tundra is also affected by freezing and thawing. The sloping terrain, exposure to more light, and the lesser amount of moisture available affect the kinds of plants that grow in mountainous alpine tundra.

Despite the harsh conditions, about 1,700 kinds of plants grow on tundra, including sedges, reindeer mosses, liverworts, and grasses. The 400 varieties of flowers found add a wide range of colors.

Algae, fungi, and lichens

It is generally recognized that algae (AL-jee), fungi (FUHN-ji), and lichens do not fit neatly into the plant category.

Algae

Algae play an important role in the tundra. Most species have the ability to make their own food by means of photosynthesis (fohtoh-SIHN-thuh-sihs); the process by which plants use the energy from sunlight to change water and carbon dioxide from the air into sugars and starches. Other species of algae absorb nutrients from their surroundings. In the Arctic, algae are found in the ocean and wetland areas. In alpine tundra, algae grow on unmelted snow. These algae have a red pigment.

Algae may reproduce in one of three ways. Some split into two or more parts, with each part becoming a new, separate plant. Others form spores (single cells that have the ability to grow into a new organism). A few reproduce sexually, during which male and female cells unite to create a new plant.

Fungi

Fungi are plantlike organisms that cannot make their own food by means of photosynthesis; instead they grow on decaying organic (derived from living organisms) matter or live as parasites on a host. Fungi are decomposer organisms that, together with bacteria, are responsible for the decay and decomposition of organic matter. One of the most important roles of fungi in tundra is formation of lichens.

Fungi form spores to reproduce. These spores are carried from one location to another on the air or by animals.

Lichens

Lichens are the most common tundra plant, with about 2,500 species growing in Arctic and alpine regions. Lichens are combinations of algae and fungi living in cooperation. The fungi surround the algae cells. The algae obtain food for themselves and the fungi by means of photosynthesis. It is not known if the fungi aid the algae organisms, but they may provide them with protection and moisture. In harsher climates, lichens are often the only vegetation to survive. They have no root system so they can grow on bare rock, adding beauty to the tundra with their colors of orange, red, green, white, black, and gray.

Despite the short growing season, lichens thrive in their harsh environment. They freeze in winter, but continue to grow in spring. Lichens often live for hundreds of years, although growth is slow.

Like algae, lichens can reproduce in several ways. If a spore from a fungus lands near an alga these two different organisms can join together to form a new lichen. Lichens can also reproduce by means of soredia (algal cells surrounded by a few strands of fungus). When soredia break off and are carried away by wind or water they form new lichens wherever they land.

Reindeer lichen, also called reindeer moss, is one of the most common tundra plants. It provides a key source of food for Arctic plant-eating animals like caribou and reindeer. Another common type of lichen, called the British soldier, has a tall stalk with a red cap on top, which makes it resemble its namesake.

Green plants

Most green plants need several basic things to grow: light, air, water, warmth, and nutrients. Light, air, and water provide almost all of their needs. The remaining nutrients, primarily nitrogen, phosphorus, and potassium, are obtained from the soil. While water is plentiful for tundra plants, warmth, which brings on the growing season, is available for only a short period of time.

Plants in the tundra grow low to the ground. This helps them stay warm and protected from the high winds. Since the tundra receives little precipitation, many plants have nearly invisible hairs on their leaves, stems, and flowers that reduce moisture loss. Their roots form a dense mat just under the surface of the ground enabling them to quickly draw moisture from melting snow and store it in their leaves. Many plants grow in a tight clump, which helps traps heat. Tussocks are thick clumps of plants, such as cotton grass, that grow to about 1 foot (30 centimeters) in height and are found in marshy areas.

Cozy Flowers

Some tundra insects find warmth and shelter by hiding inside flowers. Inside a buttercup, for example, the temperature can be 40°F (4°C) warmer than the outside air. During the day, these flowers lean toward the sun, following its path to get as much heat as possible. For that reason, they are called heliotropes, which means “to turn toward the sun.”

Some alpine plants have deeper roots that help prevent soil erosion. Many alpine plants have red leaves because of a coloring matter called anthocyanin. This special pigment protects plants from the dangers of ultraviolet radiation (a form of harmful light within the sun’s rays). Twice as much ultraviolet radiation reaches alpine tundra than regions at sea level because of the high elevation.

Common green plants

Typical flowering plants on Arctic tundra include Arctic lupine, yellow poppy, saxifrage, Arctic campion, Lapland rhododendron, buttercup, campanula, and barberry. The Labrador tea, a hardy evergreen, is very common. Non-grass perennials, called forbs, lie dormant all winter with their growth buds protected underground.

The rosette plant is well-designed to survive in harsh Arctic weather. This type of plant forms rings of leaves around a central growth bud. The leaves protect the fragile bud and help to trap insulating snow in winter and dew during the dry growing season.

Examples of alpine tundra plants include sorrel, saxifrage buttercup, plane leaf, tufted hair grass, alpine bluegrass, and alpine sandwort. The alpine azalea is a member of the heath family called a cushion plant. Cushion plants grow in groups, tightly clumped together, so the plants on the outer edge can protect the ones in the middle. At the lower edges of alpine tundra grow Krummholz, dwarf trees kept small by the cold, icy, windy environment.

The small area of tundra located on the Antarctic Peninsula is home to the only two flowering plants found on that continent, pearlwort and hair grass.

Growing season

The growing season on tundra is short, lasting from six to ten weeks in June, July, and August. In the Arctic, during those weeks the sun shines almost all day. As a result, plants must make the most of the opportunity for growth.

Green plants may be annuals or perennials. Annuals live only one year or one growing season. Perennials live at least two years or two growing seasons. The above ground portion of perennials often appears to die in winter, while the roots remain dormant underground. The plant returns to “life” in the spring when the weather becomes warmer. Most tundra plants are perennials that can flower quickly and take advantage of the short growing season.

Reproduction

Perennials reproduce and spread by forming seeds. Some plants are self-pollinating, which means that the male and female reproductive cells come from the same plant. Most perennials need pollen from another plant. This process is aided by insects attracted to the colors of the flowers and that travel between flowering plants transferring the pollen from the male reproductive part of a plant, called the stamen, to the female reproductive part of another plant, called the pistil. Strong winds help scatter the fertilized seeds.

Some plants in the more northern, colder Arctic tundra reproduce by budding and division rather than by flowering since the growing season is short. In budding, a new plant develops from any part of the parent. In division, a piece of the parent plant breaks off and develops into a new plant. Forbs reproduce in this way. Mountain sorrel reproduces through rhizomes (RY-zohmz), rootlike stems that spread out under the soil and form new plants.

Endangered species

Tundra plants are very fragile. In the Arctic, traffic during construction of the Alaskan oil pipeline that began in the 1970s damaged the tundra, which did not recover until long after construction had ended. In alpine tundra, beautiful plants are endangered because people pick them or step on them. Their short growing season makes it difficult for them to be easily replaced.

The Penland alpine fen mustard, a small perennial with white flowers found on the Rocky Mountain tundra in Colorado, grows on wetlands fed by melting snowfields. This little plant is endangered because mining and off-road vehicles, which leave tracks in the soil, divert the flow of water away from its habitat.

Animal Life

The tundra is a permanent home to only a few species of animals because of its harsh environment. Birds, caribou, and red deer, for example, spend only the summers there. The Antarctic tundra has the fewest animals.

For tundra animals, size is an important factor in preventing heat loss. When an animal’s appendages (arms, legs, tails, ears) are small, they lose less heat. The Arctic fox, for example, has small ears, short legs, and a short tail. This means there is less area from which body heat can escape.

Microorganisms

Microorganisms are small organisms, such as a protozoan or bacterium, that cannot be seen with the human eye. Bacteria live in the active layer of tundra soil and help decompose dead plants and animals.

Invertebrates

Invertebrates are animals that do not have a backbone. Clams, mussels, snails, crabs, and shrimp are invertebrates found in marshy areas. The primary invertebrate population of tundra consists of a few species of insects that are present in large numbers. There are more mosquitoes on the Arctic tundra, for example, than anywhere else on Earth, because the wet summers provide perfect breeding conditions. As many as one million mosquitoes can be found in an area 1 square yard (0.8 square meter). Springtails are the dominant organism of tundra soil. Populations can reach in excess of several billion per acre (0.405 hectare).

Arctic insects are darker in color than insects elsewhere, which is better for absorbing heat from the sun. They also have more hair to help them conserve heat and energy. Many tundra insects do not have wings.

Some scientists believe this helps them conserve energy. Others believe it is because they would not be able to fly in the strong winds. The springtail, for example, has a springlike appendage on its stomach. It hits the ground with this spring and then bounces to a new location, much like a person can on a pogo stick. Those that can fly, stay close to the ground so they do not get blown away.

Common invertebrates

Two common tundra insects are the aphid and the midge. Aphids, also called plant lice, feed on the sap from willows, saxifrages, sedges, and other plants. Most aphids are wingless females. During the warmer weather, the females produce live young, which are also all females, without mating. In the fall, they give birth to a generation that includes both males and females. After mating, the females of this generation lay eggs that hatch in the spring to start new colonies.

Midges are small insects with two sets of wings. One set is for flying and the other for balance. Unlike the mosquito, midges do not bite. They are so numerous that their mating swarms are said to look like tornado clouds and can obstruct the vision of any animal they encounter. Midge larvae live in watery areas and feed on algae and dead matter. Midges can grow very old, some living as long as six years.

While Arctic tundra is infamous for its mosquito population, alpine tundra is known for butterflies and biting flies. In the small area of tundra in Antarctica, spiderlike mites and wingless springtails are found. The largest animal living here is the midge, which is half an inch (1.27 centimeters) long.

Food

Some insects eat plants and some eat other insects or animals. Male mosquitoes, for example, feed on plant juices, while females feed on the blood of animals and humans. During the summer, plenty of water is available in Arctic tundra because the surface water cannot sink into the frozen ground. In alpine tundra, surface water and streams are sources of water.

Reproduction

The first part of an insect’s life cycle is spent as an egg. The second stage is the larva, the immature or young stage of a developing insect. This second part of the life cycle may be divided into several steps between which the developing insect grows larger and sheds an outer skin casing. Some larvae store fat in their bodies and do not need to seek food. During the third, or pupal, stage, the insect’s casing offers as much protection as an egg. Finally, in the last stage, the adult emerges. These stages can occur quickly or take up to several years. In the colder tundra regions the process is slow. The midge, for example, takes two years to complete its life cycle in tundra, but only six months in warmer climates.

Mosquito Antifreeze

Mosquitoes can keep themselves from freezing in winter the same way people keep their cars from freezing—with antifreeze. Some mosquitoes replace the water in their bodies with a chemical called glycerol. Their bodies are able to manufacture glycerol from other substances such as fat. With this protection, they can spend the winter under the snow and live to bite again the following summer.

In order to mate, some wingless, female insects in tundra emit a scent into the air that attracts males, who can fly. In species where both males and females fly, the insects swarm in great numbers. Some males are able to recognize females by the vibrations given off by the beating of their wings. In some species of Arctic insects, like the caddis fly and midge, males are few. Females carry all the necessary genetic information and reproduce without having to mate with a male. The eggs are stimulated to develop by chemical means rather than by male sperm.

Amphibians

Amphibians, such as salamanders and frogs are vertebrates (animals with a backbone) that live at least part of their lives in water. Most amphibians are found in warm, moist, freshwater environments and in temperate zones (areas in which temperatures are seldom extreme). Only a few amphibians live in Arctic tundra and none are usually found in alpine tundra.

Common amphibians

The Siberian salamander is the only salamander found in the tundra. This hardy creature spends winter frozen in the permafrost in Russia and has been found alive at depths of almost 50 feet (14 meters).

The Hudson Bay toad lives in Arctic tundra in North America. The wood frog, which is common in Alaska, is sometimes found on the tundra as well.

Food

Amphibians use their long tongues to capture prey. Even though they have teeth they do not chew, but swallow their food whole. As larvae, amphibians eat mostly plants, such as algae, or tiny water animals. Adults eat insects, worms, and other amphibians or small animals.

Bumblebee Heating System

Arctic bumblebees are able to produce their own heat. They vibrate their wing muscles so fast that they actually warm their bodies. When enough bees get together, this combined body heat is able to warm their nests to 86°F (30°C).

Reproduction

Mating and egg-laying for most amphibians takes place in water. Male sperm are usually deposited in the water and must swim to the eggs, which are encased in a jellylike substance. Here the sperm penetrate the eggs. As the young develop into larvae and young adults, they often have gills and require a watery habitat. Once they mature, they develop lungs and can live on land. Salamanders often have internal fertilization in which male sperm penetrate the eggs while they are still in the female.

Some amphibian females carry their eggs inside their bodies until they hatch. Certain species lay eggs and protect them until they hatch. Others lay eggs and abandon them.

Most amphibians reach maturity at three or four years. They breed for the first time about one year after they become adults.

Reptiles

Reptiles are cold-blooded vertebrates, such as lizards and snakes. Cold-blooded animals are unable to regulate internal body temperature and depend on their environment for warmth. They are usually most active when the weather is warm. No reptiles do well in extreme temperatures, either hot or cold. Many hibernate (remain inactive) during the winter.

Common reptiles

The viviparous lizard in Europe and the garter snake in North America live on the tundra borders. Only one reptile, the European viper, lives north of the Arctic Circle on the Scandinavian tundra.

The European viper is a highly venomous (poisonous) snake found only in Europe, Asia, and Africa. It grows to an average length of 19 to 23 inches (50 to 60 centimeters), but some may attain 31 inches (80 centimeters). It eats small vertebrates, such as rats or mice, and sometimes birds. The viper paralyzes or kills its prey by injecting it with venom.

This viper tolerates cold better than any other member of the viper family. It is able to move at temperatures as low as 37°F (3°C) and cannot thrive in weather much warmer than 93°F (34°C). During the coldest parts of winter it hibernates, hiding from 6 to 19 inches (15 to 50

centimeters) underground in areas that are moist, like rock crevices or rodent dens.

Food

Most reptiles are carnivorous (meat-eating). Snakes consume their prey whole and often alive without chewing, taking an hour or more to swallow a large victim. Many have teeth that are curved backward so their prey cannot escape.

Reproduction

Most reptiles reproduce sexually with the male depositing sperm in the body of the female, and their young come from eggs. Reptiles in tundra give birth to live young that have developed inside eggs contained in the mother’s body, which protects them from the cold.

Fish

Fish are cold-blooded vertebrates that live in water. They have fins for swimming and breathe through gills. Some tundra fish, like the Arctic char, spend their entire lives in tundra lakes and streams. Others, like the salmon, live in the ocean, returning to tundra streams to breed.

Common fish

The Arctic char, a relative of the salmon, is found in both the sea and polar lakes in Arctic tundra. Char are dark colored with light spots and blend in with their environment. Their size ranges from 2 to 10 pounds (0.9 to 4.5 kilograms). Those that live in the sea swim up the rivers of the Arctic tundra to freshwater lakes where they lay their eggs. Graylings, another relative of the salmon, live in tundra streams. Pike and trout spend some time in tundra.

Reproduction

Fish reproduce by laying eggs. Usually, the female releases eggs and the male releases sperm and fertilization takes place in the water. The eggs can cling to rocks or float on the water’s surface. Some species dig depressions in the ground under the water and deposit eggs there.

Salmon spend three to five years at sea before they return to the same stream where they were born to spawn (reproduce). When spawning is complete, they die.

Birds

Birds are vertebrates. Hundreds of species of birds visit Arctic and alpine tundra, but few stay all year long. The snowy owl, the raven, the willow ptarmigan (TAHR-mah-guhn), and the rock ptarmigan are permanent residents of the Arctic. One of the only species of birds found in both the Arctic and alpine areas is the water pipit.

Many species of birds migrate to the Arctic tundra to breed. They fly south in winter and return to the tundra in summer with their mates to build nests and lay their eggs.

Common birds

Water birds that migrate to the Arctic tundra include geese, ducks, and even a few swans. The Arctic tern makes the

longest journey, flying from Antarctica in a round trip of at least 25,000 miles (40,000 kilometers).

Birds that summer on Arctic tundra include gulls, plovers, redpolls, buntings, loons, warblers, red phalaropes, and skuas. Some of these birds eat insects, which are plentiful during the summer. The skua and the gyrfalcon are predators that eat other birds and small animals.

Alpine tundra is home to many birds. Some species of hawks, eagles, and falcons live above the tree line and eat small mammals, such as rodents and hares, or smaller birds. Wall-creepers eat insects and may move lower down the mountain in winter. Alpine cloughs, wall-creepers, and accentors stay close to the ground to avoid the winds. Some finches remain at higher elevations all year.

The ptarmigan is a brownish-colored grouse with feathered legs and feet. It is one of the few birds that spends nearly all year on the tundra, both in Arctic and alpine regions. Its feathers grow very dense and turn white during the winter. Sometimes ptarmigans sleep in the snow in order to preserve body heat, which is more easily lost out in the open. The ptarmigan is a plant-eater and, in very severe winter weather, travels below the timberline in search of food.

Food

The marshy areas of tundra provide plenty of water for all animals, and many birds feed on water insects. Plant material, shellfish, and carrion are other sources of food. The golden eagle feeds on small mammals, usually rabbits. It will also eat other birds and carrion.

Reproduction

All birds reproduce by laying eggs. Usually, male birds must attract the attention of females by singing, displaying feathers, or stomping their feet. After they mate and the female lays her eggs, she sits on them to keep them warm until they hatch. Two species of Arctic swimming birds, the red phalaropes and the northern phalaropes, reverse these roles. The female shows off to attract the attention of the male. After they mate, she usually lays four eggs. The male sits on them until they hatch and then he cares for the young.

The Monster of the Mountains

The Sherpa people of Nepal believe they share their mountain home with a creature even larger than the yak—the Yeti, or abominable snowman. A yak can weigh up to 2,200 pounds (1,000 kilograms), which would make a Yeti huge. Many footprints have been found and a number of Sherpa claim to have seen one, yet no Yeti, dead or alive, has ever been proven to exist.

Some birds, like the least sandpiper, take advantage of the short breeding season by rotating parental duties. After the female lays the eggs, the male mates with one other female and then returns to the nest of the first female to take care of the young. This frees the female to mate again with another male, ensuring that enough young birds will be born to survive the cold weather.

Many birds, like the ruddy turnstone, shelter along rocky coasts and shores. Their nests are hidden in depressions in the ground, called scrapes, that they line with tundra grasses.

Mammals

Mammals are warm-blooded vertebrates (having a backbone). They maintain a consistent body temperature, are covered with at least some hair, and bear live young that are nursed with milk.

In a barren land such as tundra, animals that live there all year long must be very clever in seeking shelter from both predators and the cold. Mammals adapt in several ways. Many, like the Arctic fox, grow a thick, insulating cover of fur, which not only keeps them warm, but also helps to camouflage them. Their coats turn white in winter and brown in summer so that they blend in with the environment making it hard for predators to see them. Most mammals accumulate deposits of fat under their skins, which insulates them and provides a source of nourishment when food is scarce. Some mammals, like the Alaskan marmot and the Arctic ground squirrel, wait out the cold by hibernating until the weather turns warm.

Alpine mammals must adapt to mountain living as well as the cold. Ibexes, for example, have soft pads on their feet that act like suction cups to help them grip the steep rocks. Since there is less oxygen high in the mountains, the yak and mountain goat have developed large hearts and lungs and have more red blood cells (which absorb oxygen) than would be found in similar animals living closer to sea level. These features allow their bodies to use oxygen more effectively. Alpine mammals often seek shelter in forests below the tundra or in rock caves underground. Yaks and musk oxen can withstand the worst cold the tundra has to offer.

Common mammals

About forty-eight species of land mammals live on tundra. Large Arctic mammals include musk oxen, caribou, barren-ground grizzly bears, wolves, and polar bears. Smaller Arctic mammals include hares, lemmings, and squirrels. Large alpine mammals include mountain goats, wild sheep, ibexes, red deer, and snow leopards. Pikas, marmots, chinchillas, hares, and viscachas are among the smaller alpine mammals.

Food

Mammals are either meat-eaters or plant-eaters. Musk oxen and caribou are among the tundra’s plant-eaters. Reindeer lichen, is the bulk of the caribou’s diet. Other vegetarians include lemmings, hares, and squirrels.

The barren-ground grizzly and the polar bear are primarily meat-eaters, feeding on seals, birds, and fish. The polar bear supplements its diet with seaweed and grass. Wolves eat hares, musk oxen, and caribou. Foxes eat lemmings, stoats, ptarmigans, and hares.

Reproduction

Mammals give birth to live young that have developed inside the mother’s body. All young are nursed with milk produced by the mother and must remain close to her until they are able to find their own food. Some mammals, like lemmings, are helpless at birth, while others, like caribou, are able to walk and even run almost immediately. Some are even born with fur, and with their eyes open.

Polar bears give birth in dens under the snow in the Arctic tundra. Caribou calves are born in the open as the animals migrate north in spring to their tundra feeding grounds. Musk oxen are also born on open tundra.

Caribou

Caribou are migratory herd animals that spend their summers in the Arctic and their winters in the forest on the edge of tundra. Their winter coat is long and thick to protect them from freezing. Their hooves are wide and flat for easy movement over the snow and ice.

Caribou is a Native American word that means “wandering one.” Caribou migrate farther than any other land animal, some traveling over

Lemmings on the March

Lemmings are small plant-eating mammals related to field mice. During winter they live in the shelter of burrows in the snow, feeding on seeds and plants. In years when there is a good food supply, lemmings reproduce rapidly. One female may give birth four or five times a year and have six to ten offspring at a time. After three to five good years the tundra is swarming with lemmings. Before long, there is not enough food for all of them. Suddenly, small groups of lemmings begin to run north.

As the lemmings run, they are joined by more and more of their fellow creatures until thousands are on the march. They cross mountains and rivers, never stopping to eat. Many starve to death along the way and many more are eaten by predators.

When the survivors reach the Arctic Ocean they jump in the water. Some scientists say it is an attempt to cross it, some say it is to get food. The tundra seems empty, but the lemmings that stayed behind soon repopulate it.

1,200 miles (2,000 kilometers) each year. They are found in Alaska, the Yukon, and the Northwest Territories of Canada.

In summer, caribou feed on birch leaves and grasses. In the winter they feed on lichens, a staple in their diet, and any remaining twigs or tree buds.

Caribou give birth to their young on the Arctic tundra, usually in the same area the herd has used for many years. After only three days, a calf is strong enough to travel with the adults.

Pika

The pika is a small, short-legged animal that resembles a cross between a guinea pig and a rabbit. An adult pika weighs about 5 ounces (140 grams), has rounded ears, a stocky body, and almost no tail. Pika’s have sharp, curved claws to help it climb on rocks, and the pads of their feet have thick fur to ensure stable footing when they leap from rock to rock. Protected against the cold by its thick fur, a pika can remain active all winter.

Pikas have two sets of upper teeth, one behind the other. These teeth are sharp and used for tearing the plants they eat for food. They produce two different types of droppings. One is a special, jellylike pellet the animal eats to gain extra nutrients that may not have been absorbed the first time the food went through its digestive tract. The second is a normal solid pellet of unneeded waste matter.

Pikas are found in rocky areas, usually at high altitudes. Colonies are formed around large boulders or rock slides where vegetation can be found nearby. They collect plant materials in the summer and make “haystacks,” which are their winter food stores. These haystacks consist of their chief food-plant, the avens, a member of the rose family.

Male and female pikas mark an area in which they live all year. They have two to six young in a litter and produce two litters every summer. Females generally do not leave their territories, but the males roam in search of food.

Pikas are most common in Asia, especially northeast Siberia, but a few species are found in Arctic tundra and alpine tundra in Alaska.

Musk oxen

When winter comes to the Arctic tundra, most animals head for shelter. Some go south while others go underground. Musk oxen do neither. Their thick coats keep them warm in the worst Arctic weather, and they remain on the open tundra all winter long, foraging under the snow for plants to eat. In spring, musk oxen shed their warm undercoat, called qiviut. This hair is highly prized by local women who gather it as it is shed each year to knit it into garments, such as scarves, to be worn or sold.

The Warmest Coat on the Tundra

The chinchilla is a small South American rodent that lives high in the Andes Mountains. It has one of the warmest coats found in nature, a beautiful blue-gray fur. Usually, a mammal grows only one hair per pore, but chinchillas have as many as sixty hairs growing in each pore. As a result, their fur is extremely thick and soft, keeping the chinchilla warm in the cold, even during the freezing alpine nights.

Wolves

Wolves live together in familylike packs of five to twenty members on both Arctic and alpine tundra. They are sociable animals, which helps the pack remain together. Each pack is led by a male and female called the alpha (lead) pair. These two wolves produce the yearly litter and other members of the pack help care for the pups. Pack members may watch the young so the mother can join in a hunt. When a kill is made, a wolf can store partially digested meat in its stomach. This is then regurgitated (vomited) and fed to the pups or is shared with a nursing mother.

Endangered species

Overhunting and overfishing are two of the most common reasons animals in tundra are endangered. Their habitats are also being disrupted as more people move into the area. Some animals, like the snow leopard and the chinchilla, are rarely seen in the wild, but are raised in captivity in zoos or on fur farms.

The Eskimo curlew is a dark-colored shore-bird with a long, downward-curving bill. At one time, the nesting grounds of the curlew were on Arctic tundra of Alaska and Canada and on the coast of the Chukotka Peninsula in Siberia. The bird is endangered because of unrestricted hunting. Its habitats have been destroyed as land is cultivated for farming and used for grazing herds. Scientists do not know

the location of its current breeding grounds. The Eskimo curlew is close to extinction, if not extinct already.

Caribou in Greenland and the Peary Caribou in the Canadian Arctic are two groups whose numbers are low. Caribou are affected by predators such as wolves and hunters, as well as changes in their habitats, including the building of natural gas pipelines that cut across their migration routes.

Human Life

Few people live on Arctic tundra; those who do are spread all around the polar region. Most people who live in areas of alpine tundra make their homes below the timberline. In some areas, people live below the timber-line in winter and move onto the tundra in summer. The Kohistani people of Pakistan, for example, move from 2,000 feet (600 meters) in winter to 14,000 feet (4,300 meters) in summer. Swiss farmers move their goats to the tundra to graze during summer. While there, the farmers raise some crops and make butter and cheese.

Although some native peoples continue to live a traditional way of life, most tundra peoples have adopted more modern lifestyles.

Impact of the tundra on human life

Arctic tundra is harsh land, and life is shaped by the bitter cold. For humans, a few minutes’ exposure to the cold can lead to frostbite and the possible loss of fingers, toes, noses, or ears. Longer exposure can lead to hypothermia (a lowering of the body temperature) and death.

There is very little people can do to physically adapt to tundra conditions, instead, they must change their behavior. This is done by living a lifestyle in which nature is respected, people are creative, and nothing is wasted. For example, when the Inuit peoples of North America kill a caribou for food, they use the skin for tents, bedding, and clothes. Harpoons are fashioned from the antlers, and needles and other tools are made from the bones. Thread for sewing is made from the animal’s tendons.

Food

Unlike people in more temperate and fertile biomes where the growing season is much longer, the people of the Arctic tundra do not rely on growing grains for food. They find their food by hunting and gathering. Some peoples, such as the Sami, who live in Scandinavia and Russia, survive by herding animals. Their diet consists primarily of meat from caribou and freshwater fish like char. The ocean is another source of food, and they hunt whales, walruses, and seals. Berries and herbs supplement the diet, and leaves are used for medicine. The traditional diet may be supplemented by canned goods shipped in during the summer months.

Alpine tundra dwellers hunt wild mountain animals for food, such as sheep, goats, and red deer. They also use domesticated llamas and yaks as food sources. South American Indians raise llamas for milk. In the milder alpine climate crops such as barley and potatoes are grown.

The Wheels that Dug Lakes

The tundra environment is very fragile and its ability to restore itself is limited. When a construction truck or bulldozer drives on the tundra during the summer it leaves ruts in the ground. When the sun hits these ruts it causes the permafrost to melt, which then causes erosion, and the ruts get bigger. Each summer more of the exposed permafrost melts and eventually the rut turns into a gully. During World War II (1939–1945), heavy trucks were driven on the tundra, leaving large ruts behind. The areas of permafrost that melted because of these ruts have grown so large over the years that some of them are now lakes.

Shelter

Traditionally, people of the tundra have built their homes from the materials at hand, mainly frozen blocks of snow, pieces of sod, animal skins, or stone. The Sherpas of the Himalayas build their houses of stone, making very thick walls. They live on top of the yak stables so that the warmth given off by the animals helps warm the home.

Clothing

Tundra dwellers wear layers of clothing during the cold weather. If traditional, these clothes are made from the skins of animals. Caribou skin is a favorite choice because it is very warm yet light. During winter, two pairs of pants are worn. The inside pair is made with the animal hair facing in for warmth. The outside pair is made with the hair facing outward to provide waterproofing.

People on the tundra may wear parkas, which are jackets with hoods. The lining of the hood is usually wolf or wolverine hair. Sealskin is desirable for boots because it is waterproof. Bird skin lines the boots to make them warm. Moss, which is very absorbent, may be dried out and used for baby diapers.

Economic factors

For traditional hunter-gatherers, possessions are almost meaningless. They do not have traditional jobs or seek to gain wealth. They spend their time finding the food they need and making clothing, weapons, and tools. In the past, reindeer herders were totally self-sufficient, getting food, clothing, and shelter from their herds. After World War II (1939–1945) the economy of many tundra regions changed.

Many minerals have been discovered in Arctic tundra. Coal, iron, nickel, gold, tin, and aluminum are found in eastern European countries such as Russia. Lead and zinc are mined in Greenland and gold in Canada. The largest mining activity on the tundra is drilling for natural gas and oil. Oil found on tundra changed the economy of Western nations, who no longer need to rely so heavily on the Middle East for their oil supplies. The discovery of oil and the need to build a pipeline to move it brought many non-native people to the Alaskan tundra. The creation of jobs was a boost to the economy of the countries that provided the work force.

After World War II, the Arctic tundra was the site of military activity. In North America, the United States built a series of radar stations from Alaska to Greenland called the Distant Early Warning (DEW) Line. This brought new residents and new jobs to the area.

Impact of human life on the tundra

Due to its relative isolation, either in the far north or high in the mountains, the tundra biome has not been affected as much by the presence of humans as have many other biomes. Its harsh environment has helped keep people away, but this is changing.

Use of plants and animals

When native peoples use plants and animals only for their own food and necessary materials, wildlife populations remain stable. When people hunt with guns for commercial reasons, more animals are killed than are born. In the 1800s and throughout much of the 1900s, tundra animals were overhunted. Musk oxen were almost wiped out when their meat was sold to sailors on whaling ships. The skins were traded and baby musk oxen were sold to zoos. Caribou were so severely overhunted that their herds were reduced by 90 percent.

Many countries have since set limits on the number of tundra animals that can be killed each year, including caribou, musk oxen, and polar bears.

Quality of the environment

The quality of the Arctic tundra environment has been threatened by the effects of mining, the use of pesticides, and air pollution.

Effects of mining Mining and drilling operations pollute the air, lakes, and rivers, and damage the land. In Russia, the land around some nickel mines has become so polluted that all the plants have died. With no plant life to anchor it, the soil has washed away. Delicate plants are trampled as roads, airstrips, and houses are constructed. These plants take years to grow back, and some never recover. When mines are abandoned, the old equipment and debris may be left behind, becoming eyesores.

Animals will not go near mining and drilling operations because of the noise and activity. This may cut them off from familiar food and water sources. The Alaskan pipeline, for example, was built across the caribou migration route. In order to correct this problem, the pipeline has been raised like an overpass so they can walk underneath, but the road beside the pipeline may be a problem. Scientists do not know what long-range effects these human-made additions will have on the animals.

The increasing number of people moving to the tundra to work in mining operations has created a need for houses, towns, and additional roads to bring in supplies. Getting rid of waste is a serious problem. The cold weather prevents decomposition of garbage and it cannot be buried in the frozen ground. The choices are to ship it out, which is very expensive, or create above-ground garbage dumps, which destroy the landscape.

Use of pesticides Pesticides (poisons) affect tundra wildlife. A migratory bird such as a goose may eat plants sprayed with pesticides in the United States, where it spends the winter. When it returns to the Arctic in summer, a predator such as a fox may kill it. The fox and her young eat the goose. A falcon or polar bear might eat one of the young foxes. In this way, the pesticide contaminates a number of animals.

Peregrine falcons and polar bears have been especially affected by pesticide use. Some pesticides make falcon eggs soft, causing them to break open before the chick has fully matured. Pesticides that have built up in the bodies of polar bears after they have eaten a number of contaminated animals can, ultimately, kill them.

Air pollution The quality of the environment is affected by what happens outside the tundra. Air pollution may travel to the tundra from thousands of miles away. In 1986, a nuclear reactor blew up at the Chernobyl power station in Prypìyat, near Kiev in the Ukraine. Nuclear waste was carried on air currents all over Europe and landed on plants in the tundra. When it reached Lapland tundra, reindeer ate the contaminated plants, got sick, and had to be destroyed.

Travel on the Tundra

People who live on the tundra use cars, airplanes, and snowmobiles, but methods of travel were not always so modern. Hunter-gatherers walked. Herders walked or rode their animals. The Laplanders rode in carts or sleighs pulled by reindeer. The Inuit invented a type of sled pulled by dogs, usually huskies. In summer, when the ice melted, the Inuit traveled in boats called kayaks, which could be made from seal-skin spread over animal bones or wood.

Air pollution has also affected the ozone layer. Ozone is a chemical that forms naturally high up in Earth’s atmosphere. Ozone helps to protect Earth from the harmful ultraviolet rays in sunlight. Pollution destroys the ozone, without which people, animals, and plants can suffer severe burns and develop cancers. The density of the ozone layer over the Arctic has been changing since the 1970s and is now reduced.

The change in the ozone layer may be impacting the world’s climate. Carbon dioxide and other gases build up in Earth’s atmosphere, preventing heat from escaping. Called global warming, this may cause a change in temperature, melt glaciers, and cause the level of the sea to rise. Permafrost may begin thawing, which would cause flooding and erosion, changing the landscape. Animal and plant life would be affected as habitats change.

Native peoples

Alpine tundra is home to the South American Indians who live in the Andes Mountains in Colombia, Ecuador, Peru, Bolivia, Chile, and Argentina. The Himalayan Mountains in Nepal are home to the Sherpas.

Arctic tundra dwellers include the Aleuts, Lapps, and Sami of Scandinavia and Russia, the Chukchi of eastern Siberia, and the Inuit of North America.

Traditionally, the Inuit of the Arctic tundra build snow houses (called igloos) when they need a temporary home while hunting. More permanent homes are built of bones and stones, with moss for roofing. The bladder of a seal or walrus is stretched across a hole in the wall to serve as a window. Platforms for sleeping are built up off the ground and lined with sealskin. Homemade lamps made of soapstone burn seal and whale blubber, giving off both heat and light.

Hunters of seals, whales, and caribou, the Inuit people have been impacted by the presence of military stations in the north. Many native peoples have taken jobs building, and later rebuilding, these stations.

A Dangerous Chill

The wind chill factor is the combination of cold temperature and strong wind that makes the effect of cold weather on the body worse than the temperature indicates. For example, if the temperature is 20°F (–6°C) and a 20 mile-(32-kilometer-) per-hour wind is blowing, the temperature will feel like –10°F (–23°C). In the Arctic, wind chill factors are so severe that bare flesh can freeze within 30 seconds.

The Food Web

The transfer of energy from organism to organism forms a food chain. All the possible feeding relationships that exist in a biome make up its food web. In the tundra, as elsewhere, the food web consists of producers, consumers, and decomposers. An analysis of the food web shows how energy is transferred within the tundra.

Green plants are the primary producers in the tundra. They produce organic materials from inorganic chemicals and outside sources of energy, like the sun. Tundra annuals and hardy perennials, such as buttercups and dwarf willows, turn the sun’s energy into plant matter through photosynthesis.

Animals are consumers. Plant-eating animals, such as certain insects, caribou, reindeer, mountain goats, pikas, marmots, waterfowl, and lemmings, are primary consumers in the tundra food web. These animals become food for secondary consumers, which include predators such as spiders, wolves, and foxes. Tertiary consumers, such as grizzly bears and humans, eat other secondary consumers. Some tertiary consumers are omnivores, meaning they eat both plants and animals.

Decomposer organisms, like bacteria and fungi, eat decaying matter from dead plants and animals and release their nutrients back into the environment. Decaying matter in soils provides nutrition for flowering plants and grasses, as well as for the fungi and bacteria themselves.

Spotlight on Tundras

Niwot Ridge

Niwot Ridge, an area of alpine tundra, is located about 22 miles (35 kilometers) west of Boulder, Colorado, and more than 9,843 feet (3,000 meters) above sea level. The ridge and the adjoining Green Lakes Valley cover approximately 3.8 square miles (10 square kilometers). Runoff from the mountains feeds the Colorado and Mississippi Rivers.

Niwot Ridge

Location: Rocky Mountains west of Boulder, Colorado

Area: 3.8 square miles (10 square kilometers)

Classification: Alpine tundra

Alpine tundra in the Rocky Mountains generally begins forming from 4,000 to 10,000 feet (1,219 to 3,048 meters) above sea level. Since its elevation is fairly high, Niwot Ridge is characterized by low temperatures throughout the year. The annual mean temperature is 5°F (–3.7°C). Temperatures in January average about 8°F (–13°C) and in July about 47°F (8°C).

This tundra is surrounded by subalpine forest at the lower elevations. Where the forest and tundra meet, subalpine meadows and patches of krummholz (dwarf trees) exist. Other physical features include a cirque glacier, the Arikaree, which is a U-shaped glacier with its open end facing down the valley. Talus slopes formed by the accumulation of rock fragments are also found here.

Some areas are snow covered. Strong winds that occasionally reach 170 miles (273 kilometers) per hour blow snow from other areas, leaving them bare. Meltwater (water melted from ice or snow) is found only where there is snow. Although precipitation in summer is uneven, yellow, pink, and purple flowers color the tundra in warm months. Plants include snow buttercup, old-man-of-the-mountain, Parry’s primrose, and shooting stars.

Many birds live on this tundra only in summer. These include the water pipit, horned lark, and white-crowned sparrow. The only year-round resident is the white-tailed ptarmigan.

Thirty-two species of mammals live on Niwot Ridge. Small plant-eating mammals include deer mice, voles, golden-mantled ground squirrels, pikas, yellow-bellied marmots, snowshoe hares, and porcupines. Badgers and weasels are seen from time to time.

Many scientists and students work in the area studying the weather, analyzing the soil, and observing plant and animal life. Niwot Ridge is designated as a Biosphere Reserve by the United Nations’ Educational, Scientific, and Cultural Organization (UNESCO) and an Experimental Ecology Reserve by the United States Department of Agriculture (USDA) Forest Service.

The ridge is part of Roosevelt National Forest. When visitors are allowed on the tundra, they are encouraged to use the trails designated for this purpose because even one footprint can damage the fragile landscape.

Bering Tundra

The Bering Tundra is a western extension of the arctic coastal plain, a broad lowland in western Alaska between Kotzebue and Norton Sound. It is located on the Seward Peninsula on the American

Bering Tundra

Location: Seward Peninsula, Alaska

Area: 23,400 square miles (60,610 square kilometers)

Classification: Arctic tundra

side of the former Bering Land Bridge (a narrow strip of land with water on both sides that at one time connected two continents) and is usually in the form of snow.

The Bering Tundra has cold winters and cool summers. Although summer temperatures in a polar climate rarely exceed 50°F (10°C), a high of 90°F (32°C) in summer has been recorded here. In winter, the low has reached –70°F (–57°C). Annual precipitation averages 17 inches (43 centimeters).

Thousands of shallow lakes and marshes (wetlands with poorly drained soil and nonwoody plants) are found along the coast. Two large rivers, the lower Yukon and the Kuskokwim, flow out of the province to the southwest. The terrain on the peninsula varies from lava fields to hot springs to tundra.

Much of the tundra is less than 1,000 feet (305 meters) above sea level. Some small mountain groups range from 2,500 to 3,500 feet (762 to 1,067 meters) high. The highest point is Mount Osborn, which reaches a height of 4,714 feet (1,436 meters).

Permafrost lies under most of the area and the active layer of soil is considered young and undeveloped. Despite permafrost and a growing season that can be as short as two weeks, there is still a wide variety of vegetation.

Species of dwarf trees, like birch, border the tundra. Birch, willow, and alder thickets are found between shoreline and forest. The lower Yukon and Kuskokwim Valleys are dominated by white spruce and cottonwood. Typical tundra plants include sedges, lichens, mosses, and cottongrass tussocks. Labrador tea, cinquefoil, and brightly colored forbs also grow in the region.

The coast provides habitats for migrating waterfowl and shore birds. Other bird species include ospreys, falcons, grouse, ravens, golden eagles, and various hawks and owls.

Mammals living in the tundra include musk oxen, brown and black bears, wolves, wolverines, coyotes, and a large herd of moose. Snowshoe hares, red foxes, lynxes, beavers, and squirrels summer here. Polar bears, walruses, and arctic foxes are sometimes seen along the northern coast of the Bering Sea.

Caribou migrate every summer to the tundra to give birth to their calves. They sometimes mix with domestic caribou, causing the native Eskimo herders to lose many of their animals, which join the wild herds.

An Inupiat Eskimo settlement of about 170 people is located in Wales on the western tip of the Seward Peninsula. Fewer than 60 miles (96 kilometers) from Siberia, Wales is one of the Alaskan settlements closest to Russia. Here, and in other places on the peninsula, native hunter-gatherers still live off the land. They are faced with the challenge of adapting to changes caused by development, especially by the exploitation of natural resources such as oil.

During the early twentieth century, thousands of non-native people came to Alaska in search of gold. As a result, more than a million dollars in gold was taken from the peninsula.

Kola Peninsula

Murmansk is a province in northwestern Russia on the Kola Peninsula, a peak of high land that juts out into the ocean between the Barents and White Seas. Most of the peninsula lies across the Arctic Circle. It extends about 190 miles (305 kilometers) from north to south, and 250 miles (400 kilometers) from east to west. Elevations in the peninsula’s Khibiny Mountains reach 3,907 feet (1,191 meters), and Arctic tundra covers the northern areas.

Kola Peninsula

Location: Murmansk Oblast Province, northern Russia

Area: 40,000 square miles (100,000 square kilometers)

Classification: Arctic tundra

The largest town is the ice-free port of Murmansk, on the eastern shore, with a population of more than one million people. Fishing is the main occupation along the coast, but mining is the most important part of the economy.

Many minerals are found on the peninsula, including the world’s largest deposits of apatite, a mineral rich in phosphorus and used for fertilizer production. Nephelinite (a source of aluminum), zirconium, iron, and nickel are also mined here.

Bogs (wetlands with wet, spongy, acidic soil) are widespread and form in areas where the soil is saturated by water. Since summer melt-water cannot drain into the permafrost and temperatures are too cool for evaporation, conditions are ideal for bog formation.

Despite problems with permafrost and thin, poorly developed top-soil, the peninsula has been called a botanical garden. Mosses, lichens, and dwarf Arctic birch cover most of the region. A forested area in the south has birch, spruce, and pine. Other typical tundra vegetation include lichens, Lapp rhododendrons, Arctic willows, and white mountain avens, a yellow-flowered member of the rose family.

Bird life typical to the tundra includes Siberian jays, Siberian titmice, grouse, and ptarmigans. Migrating seabirds include eider ducks, skuas, gulls, and Atlantic puffins. Lemmings, beavers, otters, and brown bears are common mammals, and thousands of reindeer migrate to the tundra in summer.

In the interior, a few thousand Sami are engaged in reindeer herding, which was the basis of their economy until the twentieth century. Families lived in tents and migrated with their herds. This way of life is disappearing as families now have permanent homes and only the herders move with the reindeer.

The deepest hole ever created by humankind is in the Kola Peninsula. The drilling experiment taken on by the Russians in 1962 through 1994, in order to investigate Earth’s crust, ended with a hole 7 miles (12 kilometers) deep.

The western part of Kandalaksha Bay and the area south of Murmansk are wildlife reserves. No visitors are allowed in these areas. They are headquarters only for scientific research.

Northeastern Svalbard Nature Reserve

The Svalbard Reserve is one of the largest and most important nature reserves in Norway. The area became protected by the Norwegian government in 1973 and includes North East Land, Kvit Island, Kong Karls Land, smaller adjoining islands, and the surrounding territorial waters. North East Land, the largest part of northeastern Svalbard, is covered by glaciers and ice caps all year long. Svalbard means “the land with the cold coast.”

Northeastern Svalbard Nature Reserve

Location: Svalbard Islands, Norway

Area: 7,350 square miles (19,030 square kilometers)

Classification: Arctic tundra

Arctic tundra covers the reserve, which is characterized by high winds, extremely cold temperatures, and permafrost that reaches depths of 1,640 feet (500 meters). Only the upper 6 to 10 feet (1.8 to 3 meters) of ground thaw in the summer, making it impossible for trees or plants with deep roots to grow.

In most Arctic climates winters are extremely severe and summers are short and cool. A branch of the warm ocean current called the North Atlantic Drift, moderates the climate here. Temperatures range from 59°F (15°C) in the summer to –40°F (–40°C) in the winter.

The growing season is very short, lasting only a few weeks in the summer. Plant life is typical for Arctic tundra and includes more than 150 species of plants. There are many lichens and mosses, and tiny polar willows and dwarf birches grow along the tundra borders.

Almost twenty species of birds nest on the islands. These include murres, which are diving shorebirds with stocky bodies, short tails, wings, and webbed feet. Several types of gulls, ptarmigans, arctic terns, and phalaropes also nest here. Two species of ptarmigan, the rock ptarmigan and the willow ptarmigan, are the only birds that live here year round.

There are fewer species of mammals than birds in the area. Polar bears, Arctic foxes, reindeer, and musk oxen live in the reserve. Polar bears in this region eat only meat; seals are a big part of their diet. Not native to the reserve, the musk ox was imported from Greenland in 1929.

Since trapping is an important economic activity, land game, such as foxes, reindeer, and bears, is protected by law so it does not become endangered by overhunting. Hunters once lived on the tundra, but very few spend the winter there. Most live in permanent communities at lower elevations. Svalbard’s economy depends upon industrial operations and coal mining.

Tromsø University in Norway, in cooperation with the University of Alaska, runs a Northern Lights research station in the reserve.

Katmai National Park and Preserve

The Katmai National Park and Preserve is located on the northeast coast of the Alaska Peninsula, along Shelikof Strait. The northern part of the park is Alpine tundra. Moving south, the terrain changes to forests, which line the bays and fjords (narrow inlets or arms of the sea bordered by steep cliffs).

Katmai National Park and Preserve

Location: Alaska

Area: 5,806 square miles (15,038 square kilometers)

Classification: Alpine tundra

Katmai tundra begins at a relatively low elevation, around 2,000 to 2,300 feet (600 to 700 meters) above sea level. The highest peaks in the park reach 7,585 feet (2,312 meters).

The climate is cold and windy with harsh winters; short, cool, summers with constant winds. In Katmai, the average summer temperature is 60°F (15.5°C). In winter there are only about six hours of sunlight each day.

The terrain in this park includes glaciers, waterfalls, and mountains. The Valley of Ten Thousand Smokes, where thousands of steam vents once came through the valley floor, was formed in 1912 when the Novarupta Volcano erupted violently. Only a few active vents remain.

Forests of blue spruces, alders, and willows border the tundra. Higher up, heaths, mountain avens (a member of the rose family), and bearberries grow.

Mammals include brown bears, wolves, foxes, moose, and caribou. The park is home to the largest population of protected brown bears in the world. The Alaskan brown bear, also known as the grizzly bear, is the world’s largest carnivore and feeds on red salmon that spawn in the area.

People do not live here permanently because it is too inhospitable, but many visitors come to camp.

Taymyr

Taymyr (also spelled Taimyr or Tajmyr) is a province located in northeastern central Russia. Mostly Arctic tundra, it extends from the Taymyr Peninsula south to the northern edge of the Central Siberian Plateau. The area includes the Severnaya Zemlya archipelago (a group of many islands) in the high Arctic.

Taymyr

Location: North Central Russia

Area: 332,850 square miles (862,100 square kilometers)

Classification: Arctic tundra

The climate in Taymyr is exceptionally severe, with prolonged, bitter winters. The average temperature in January is –22°F (–30°C) and in July from 35° to 55°F (2° to 13°C). There are few sunny days. Precipitation ranges from 4 to 14 inches (11 to 35 centimeters) annually.

The region has a variety of landforms, including mountains, lowlands, and plateaus (raised, flat-surfaced areas). The mountains of Byrrang are at an elevation of 3,760 feet (1,146 meters). In the Arctic, plateaus of ice can be as thick as 4,900 feet (1,500 meters). This ice was formed when glaciers covered much of the Arctic more than 10,000 years ago. The Plateau of Plutoran has an elevation of 4,399 feet (1,341 meters).

A variety of minerals are found in Taymyr, including complex ores such as copper, nickel, platinum, gold, and coal. Gas is also mined.

The soil in Taymyr is typical tundra soil. The active layer of topsoil above the permafrost thaws in summer and freezes in winter. Bogs are widespread and form in areas where the soil is saturated with water. Since summer meltwater cannot drain into the permafrost and temperatures are too cool for evaporation, conditions are ideal for bog formation.

Although the growing season is only a few weeks long, plants take advantage of the long hours of daylight during the short summer months. Most of the area is covered with mosses, sedges, rushes, and some grasses. Lichens grow on the hillsides and bilberries, a type of blueberry, grow in clusters. Many flowering plants provide color. On the edge of the tundra, dwarf willows and birch trees grow.

Taymyr is the summer home for the red-breasted goose, which is a threatened species. Steller’s eider, a large sea duck, is found on the peninsula. The mammal population includes reindeer, sable, wolf, fox, and white hare. Polar bears live farther north.

Few people live above the Arctic circle. Those that do include Russians, Dolgans, Nenets, Ukrainians, and Nganasans. Their chief economic activities are hunting, reindeer herding, fishing, and fur farming. Animals whose fur is used for clothing, such as the sable, are raised domestically rather than trapped in the wild. Only two cities are located in Taymyr province, the capital, Dudinka, and the port of Dikson. Their combined population is estimated at about 55,000.

Many traditional native lifestyles are slowly dying out. The Dolgan, for example, were primarily reindeer herders and lived a nomadic lifestyle for the last several hundred years. Since the 1970s their lifestyle has become less nomadic. Now they rely on gardening as well as hunting for food.

The Russian government established the Great Arctic Reserve in 1993 on the Arctic tundra for shorebird conservation and research. This area is the breeding zone for many shorebirds who summer in Africa or along the Atlantic coasts of Europe.

Gaspé

The Gaspé (Gas-PAY) Peninsula lies in eastern Quebec, Canada. The forests and alpine tundra extend east-northeastward for 150 miles (240 kilometers) from the Matapédia River into the Gulf of St. Lawrence. The name Gaspé is from the Mi’kmaq Indian word gespeg, which means “land’s end.”

Gaspé

Location: Eastern Quebec, Canada

Area: 11,390 square miles (29,500 square kilometers)

Classification: Alpine tundra

The tundra covers 24 percent of Quebec and lies in the Chic-Choc, or Shickshock, Mountains, which are part of the Appalachian range. They are the highest in Quebec, with Mount Jacques Cartier rising to 4,160 feet (1,268 meters). The tundra on the Gaspé Peninsula begins around 3,280 feet (1,000 meters) above sea level.

Gaspé lies between a humid continental climate and a subarctic climate. Continental climates are warmed somewhat in summer as tropical air moves north. In winter the cold polar air moves south. Gaspé faces severe winters, which have kept the population sparse. Temperatures can range from lows of –11° to 14°F (–10° to –24°C) in January to highs of 52° to 68°F (11° to 20°C) in July.

The land is crisscrossed by a number of rivers, and the peninsula is surrounded on three sides by the St. Lawrence River and the Gulf of St. Lawrence. A coniferous (evergreen) forest separates the province’s deciduous (trees that loose their leaves at the end of each growing season) forests to the south from the subarctic and tundra areas where no trees grow.

Arctic-alpine plants that grow along the cliffs of the peninsula include lichens, mosses, sedges, grasses, and other low woody and leafy plants. On the edges of the tundra maples, yellow birches, white spruces, and balsam firs grow.

Many seabirds are found along the cliffs, including black-legged kittiwakes, double-crested cormorants, black guillemots, and razorbills. This is the only area of Quebec where caribou, moose, and white-tailed deer are found. Other mammals include foxes, lynxes, black bears, beavers, Arctic hares, and porcupines.

People do not live in this alpine tundra. It is a place for visitors and research only. The rest of the peninsula is sparsely populated, with about one-fifth of the people earning a living through agriculture. In summer months, many tourists visit the peninsula and support the economy. Lumbering, mining, and fishing are the major economic activities. Minerals mined in the area are copper, lead, and zinc.

The Mi’kmaq (also spelled Micmac) people have inhabited the Gaspé Peninsula for thousands of years. They were one of eight major tribes who comprised the Woodland First Nations peoples. Traditionally, they were a seasonally nomadic people, hunting moose, caribou, and small game in winter and fishing in summer. Their winter homes were conical (cone-shape) wigwams covered with birch bark or animal skins. In summer, they lived in open-air, oblong wigwams. Homes were portable and easy to put up or move. Travel was by canoe, toboggan, or snowshoe. Some of the Mi’kmaq still live on Gaspé, but many have migrated to the United States.

The Gaspésian Provincial Park is a large conservation area covering much of the peninsula. Another park, Forillon National Park, covers 93 square miles (240 square kilometers) at the northeastern tip of the peninsula.

Arctic National Wildlife Refuge

The Arctic National Wildlife Refuge in Alaska is one of the largest wildlife refuges in the world. To the north is the Arctic Ocean and to the south is Porcupine River. The refuge extends east to west more than 200 miles (322 kilometers) from the Trans-Alaska pipeline corridor to Canada, and almost 200 miles north to south from the Beaufort Sea to the Yukon Flats National Wildlife Refuge. It supports both Arctic and alpine tundra.

Arctic National Wildlife Refuge

Location: Alaska

Area: 19,000,000 acres (7,600,000 hectares)

Classification: Arctic and alpine tundra

The Brooks Range, with peaks as high as 9,000 feet (2,743 meters), extends from east to west through the refuge. The Brooks Range is the highest mountain range within the Arctic Circle and is the northernmost extension of the Rocky Mountains in northern Alaska.

Winter on the refuge is long, and snow usually covers the ground at least nine months of the year. The average winter temperature here is below 0°F (below –17°C). The wind chill factor makes the temperature feel like –100°F (–73°C) to exposed skin. In summer, the temperature averages 50°F (10°C). Annual precipitation ranges from 4 to 16 inches (10 to 40 centimeters).

Besides two tundra zones, the refuge includes barren mountains, forests, shrub thickets, and wetlands. The alpine tundra is crisscrossed by braided rivers and streams, with clusters of shallow, freshwater lakes and marshes.

The Arctic National Wildlife Refuge contains the greatest variety of plant and animal life of any conservation area within the Arctic Circle. Even though the growing season can be as short as two weeks, the continuous summer daylight helps plants grow rapidly. Reindeer moss, sedges, and flowering plants are common. Spruces, poplars, birches, and willow trees grow in areas surrounding the tundra.

More than 180 species of birds have been observed here. Peregrine falcons are common in the refuge as are rock ptarmigans, grebes, snow geese, plovers, and sandpipers.

Thirty-six species of land mammals live here, including all three species of North American bears (black, brown, and polar). Smaller mammals include lynxes, wolverines, lemmings, Arctic hares, and wolves.

In the summer, tens of thousands of caribou give birth to and raise their calves on the tundra. These caribou migrate south in winter to northeastern Alaska and the northern Yukon, almost 1,000 miles (1,609 kilometers), farther than any other land animal. Even though their winter habitat is milder than their tundra breeding grounds, they still face Arctic weather. The caribou can dig through snow almost 2 feet (60 centimeters) deep to reach food, which consists of lichens, sedges, and grasses. The refuge protects most of the calving grounds for the Porcupine caribou herd, the second largest herd in Alaska, which numbers about 180,000 animals. It also protects a large part of their migration routes.

Dall sheep live in the refuge all year, mostly in the tundra. They stay close to rocky outcrops and cliffs where they are safe from predators that include wolves, golden eagles, bears, and humans. Dall sheep eat grasses, sedges, broad-leaved plants, and dwarf willows. In winter, when these foods are scarce, they eat lichens.

The area is home to several groups of native peoples and is the site of controversy over oil development. Kaktovik, an Inupiat Eskimo village, borders the refuge on the north side. The Inupiat have incorporated and, along with the government, own part of Alaska. The Gwich’in, another native group, are one of the few who have not incorporated and choose to maintain their reservation status and a subsistence lifestyle in their nine villages.

The Inupiat see the value of oil development in the area. It provides jobs and supports schools and community improvements. The Gwich’in see it as endangering the fragile tundra environment and disturbing migration routes and breeding places for the caribou.

Huascaran National Park

Huascaran (hwa-SCAH-run) National Park is a place of biological diversity. Situated in the Andes Mountains in Peru, the landscape is dominated by mountain peaks, glaciers, lakes, and alpine tundra. It became a national park in 1975 and a World Heritage Site in 1985. The Quechua (QWAY-chwah) people live near the park and maintain a traditional lifestyle.

Huascaran National Park

Location: Peru

Area: 840,000 acres (340,000 hectares)

Classification: Alpine tundra

Alpine tundra, characterized by cold winds, is found on mountains above the timberline. The lower portion of the mountain is covered by tropical rain forest.

The snowcapped peak of Mount Huascaran, the highest mountain in Peru, rises to an elevation of 22,205 feet (6,768 meters) above sea level. The climate varies, with temperatures getting colder and rainfall decreasing as the elevation increases. The tundra climate has an average annual temperature below 50°F (10°C).

Much of Huascaran National Park is covered with permanent ice and snow. A permanent snowline begins between 14,700 and 16,400 feet (4,480 and 5,000 meters). Just below the tundra is the puna, an area of alpine grasslands with no trees. Below that is the tierra fria, the cool land, where most of the people live. This area has forest and land suitable for growing wheat and potatoes.

Vegetation is typical of alpine tundra in other parts of the world. Mosses and lichens grow on bare rocks. Short flowering plants and grasses, cushion plants, and sedges are common.

The South American, or Andean, condor nests on the cliffs in the high tundra. A member of the vulture family, it is one of the largest flying birds in the world with a wing span of about 10 feet (3 meters). The condor is carnivorous and feeds on dead animals.

Mammals in the Andes are different from those in other alpine tundra. The llama, alpaca, vicuña, and guanaco are native to this part of the world. Although they are all relatives of the camel, they have no hump. The vicuña is an endangered species hunted for its fleece, from which some of the world’s finest wool is made. The chinchilla, a small rodent common here, was hunted almost to extinction for its fur.

South American Indians living near the Huascaran Park are the Quechua and the Aymara, who have adapted to cold, high-altitude living. They have larger lungs and hearts, and their blood contains more red blood cells, allowing it to hold more oxygen. This makes it easier for them to live and work in the thin atmosphere of the mountains. They are also able to walk barefoot on icy rocks. These native peoples lead isolated lives as herders and farmers. Women make clothes and blankets to sell at market, spinning their own wool and weaving fabrics.

For More Information

BOOKS

Cox, C.B., and P.D. Moore. Biogeography and Ecological and Evolutionary Approach. 7th ed. Oxford: Blackwell Publishing, 2005.

Gaston, K.J., and J.I. Spicer. Biodiversity: An Introduction. 2nd ed. Oxford: Blackwell Publishing, 2004.

Grzimek, Bernhard. Grizmek’s Animal Encyclopedia. 2nd edition. Volumes 4-5. Reptiles, edited by Michael Hutchins, Dennis A. Thorney, Paul V. Loiselle, and Neil Schlager. Farmington Hills, MI: Gale Group, 2003.

Houghton, J. Global Warming: The Complete Briefing. 3rd ed. Cambridge: Cambridge University Press, 2004.

McGonigal, D., and L. Woodworth. Antarctica: The Complete Story. London: Frances Lincoln, 2003.

Moore, P.D. Biomes of the Earth: Tundra. New York: Chelsea House, 2006.

PERIODICALS

Payette, Serge, Marie-Josee Fortin, and Isabelle Gamache. “The Subarctic Forest—Tundra: The Structure of a Biome in a Changing Climate.” BioScience. 51. 9 September 2001: 709.

Pennisi, Elizabeth. “Neither Cold Nor Snow Stops Tundra Fungi.” Science. 301. 5,638 September 5, 2003: 1,307.

Weir, Kirsten L. “Don’t Tread on It.” Natural History. 110. 9 November 2001: 37.

ORGANIZATIONS

Center for Environmental Education, Center for Marine Conservation, 1725 De Sales St. NW, Suite 500, Washington, DC 20036

Environmental Defense Fund, 257 Park Ave. South, New York, NY 10010, Phone: 800-684-3322; Fax: 212-505-2375, Internet: http://www.edf.org.

Environmental Network, 4618 Henry Street, Pittsburgh, PA 15213, Internet: http://www.envirolink.org.

Environmental Protection Agency, 401 M Street, SW, Washington, DC 20460, Phone: 202-260-2090, Internet: http://www.epa.gov.

Friends of the Earth, 1025 Vermont Ave. NW, Ste. 300, Washington, DC 20003, Phone: 202-783-7400; Fax: 202-783-0444.

Greenpeace USA, 1436 U Street NW, Washington, DC 20009, Phone: 202-462-1177; Fax: 202-462-4507, Internet: http://www.greenpeaceusa.org.

Nature Conservancy, 1815 N. Lynn Street, Arlington, VA 22209, Phone: 703-841-5300; Fax: 703-841-1283, Internet: http://www.tnc.org.

Sierra Club, 85 2nd Street, 2nd Floor, San Francisco, CA 94105, Phone: 415-977-5500; Fax: 415-977-5799, Internet: http://www.sierraclub.org.

World Wildlife Fund, 1250 24th Street NW, Washington, DC 20037, Phone: 202-293-4800; Fax: 202-229-9211, Internet: http://www.wwf.org.

WEB SITES

Arctic Studies Center: http://www.nmnh.si.edu/arctic (accessed August 9, 2007).

Long Term Ecological Research Network: http://lternet.edu (accessed August 9, 2007).

National Geographic: http://www.nationalgeographic.com (accessed August 9, 2007).

National Park Service, Katmai National Park and Preserve. http://www.nps.gov/katm/(accessed August 9, 2007).

National Science Foundation: http://www.nsf.gov (accessed August 9, 2007).

Thurston High School: Biomes: http://ths.sps.lane.edu/biomes/index1.html (accessed August 9, 2007).

“The Tundra Biome.” University of California, Museum of Palentology. http://www.ucmpberkeley.edu/exhibits/biomes/tundra.php (accessed August 9, 2007).

Tundra

Introduction

Tundra is land that is covered with plants but is treeless because of a cold climate with a short growing season. There are two kinds of tundra, Arctic and alpine. Arctic tundra covers landscapes in the polar regions, especially in the North, while alpine tundra occurs at high altitudes in mountain ranges. Arctic tundra covers about 20% of Earth's whole land surface; alpine tundra covers a much smaller area, only about 3% of the vegetation-covered area. Arctic tundra usually grows on top of permafrost and is found in a roughly ring-shaped area surrounding the North Pole (and in smaller areas of Antarctica, which is mostly ice-covered).

Arctic tundra supports native human peoples and such animals as fox, wolves, caribou, musk-oxen, and ptarmigan (a species of game bird). Alpine tundra occurs as small islands surrounded by lower-altitude, warmer environments. Both kinds of tundra are being strongly affected by global climate change. The Arctic has experienced twice as much warming as the global average, and alpine tundra areas are shrinking as treelines ascend.

Historical Background and Scientific Foundations

Arctic Tundra

In Arctic tundra, most of which is found above the Arctic Circle, the average year-round temperature is 10-20°F (-12-6°C). In summer, when the Earth's tilt keeps the sun above the horizon around the clock, temperatures go above freezing and the top layer, from a few feet to about 10 ft (3 m) deep, melts. This allows plants to grow for 50-60 days per year. Below the roots of the living plants is a thick layer of permafrost, a mixture of rock, soil, and dead plant matter that is typically about 1,475 ft (450 m) deep but in some places, such as Siberia in northern Asia, may be up to three times thicker. All water is frozen year-round in permafrost, hence its name. The great thickness of the permafrost means that it contains a great deal of carbon locked up in ancient plant tissues. Thirty to forty percent of all the carbon stored in soils worldwide is stored in Arctic tundra.

During the last half century, temperatures in Alaska, western Canada, and eastern Russia have gone up by 4-7°F (3-4°C), twice as much as the world has warmed as a whole. In 2007, scientists were forecasting that by the end of this century, Arctic temperatures would have risen by another 7-13°F (4-7 °C). Warming means that not only is the growing season warmer, it is also longer— spring arrives sooner, fall later. Arctic climate change has been seen in increased temperatures, melting of permafrost in the more southerly areas, and the rapid shrinkage of the north-polar ice cap. The number of shrubs (low bushy plants) growing in the Arctic has also increased. Recent studies suggest that 1,544,000 square mi (4,000,000 square km) of tundra could change to shrub-land as a result of global warming.

Alpine Tundra

In alpine or mountain tundra, cold is created not by Earth's tilt but by altitude. In most parts of the world, temperature goes down as altitude goes up. The rate of chilling with increased height, called the environmental lapse rate, is about 3.5°F per every 1,000 ft (6.5°C per every 1,000 m).

In many environments, species that require a colder environment shift northward as climate warms, staying with the colder weather. For example, butterflies and birds in the temperate zones have shifted their ranges toward the poles at about 3.8 mi (6.1 km) per decade since the 1960s. Inhabitants of alpine tundra, however, have nowhere to go: as warmer zones climb the side of the mountain, the area available for cold-loving species simply shrinks. In effect, alpine tundra environments are islands, and treeline (the highest altitude at which trees grow and lowest altitude at which tundra grows), their equivalent of sea level, is rising rapidly. Since 1970, the lowest altitude at which permanent freezing occurs in temperate-zone mountain ranges has climbed 490 ft (150 m) since 1970. In the European Alps, grassland species have crept uphill as much as 13 ft (4 m) per decade over the last century, probably a response to the 1.26°F (.7° C) average warming that has occurred in that region.

WORDS TO KNOW

ALBEDO: A numerical expression describing the ability of an object or planet to reflect light.

CARBON: Chemical element with atomic number 6. The nucleus of a carbon atom contains 6 protons and from 6 to 8 neutrons. Carbon is present, by definition, in all organic substances; it is essential to life and, in the form of the gaseous compounds CO₂ (carbon dioxide) and CH₄ (methane), the major driver of climate change.

GREENHOUSE GASES: Gases that cause Earth to retain more thermal energy by absorbing infrared light emitted by Earth's surface. The most important greenhouse gases are water vapor, carbon dioxide, methane, nitrous oxide, and various artificial chemicals such as chlorofluorocarbons. All but the latter are naturally occurring, but human activity over the last several centuries has significantly increased the amounts of carbon dioxide, methane, and nitrous oxide in Earth's atmosphere, causing global warming and global climate change.

PERMAFROST: Perennially frozen ground that occurs wherever the temperature remains below 32°F(0°C) for several years.

TEMPERATE ZONE: Band of moderate, seasonal climate located between the tropics and the polar regions. There is one temperate zone in the Northern Hemisphere and one in the Southern Hemisphere.

TREELINE: The highest-altitude (or highest-latitude) line along which trees can grow. As climate warms, treelines advance to higher altitudes and latitudes.

Impacts and Issues

In 2007, Arctic warming set records that surprised scientists. The area covered in summer by floating sea ice shrank to the lowest area ever measured, about 20% less than the area of the previous record year, 2005 (a difference equal to the area of California and Texas combined). The Northwest Passage, the land-hugging ocean route connecting the Pacific and Atlantic over the top of North America, was free of ice for the first time in recorded history. The melting of permafrost and the alteration of tundra vegetation do not occur as fast as sea-ice melting and cannot be so easily watched from space. However, these processes are certainly furthered by the warm summers that have been melting the ice. In the early 2000s, researchers predicted that between 77% and 90% of the Arctic tundra that existed in 1920 will be gone by the end of the twenty-first century.

One effect of tundral warming will be the release of carbon stored in permafrost. As noted earlier, from 30% to 40% of Earth's soil carbon is locked up in permafrost. About 90% of the carbon in a tundra ecosystem is in the soil, far more than in other ecosystems. (In a rainforest, for example, most of the carbon is in living plants.) As permafrost melts, microorganisms will digest the dead plant material that contains this carbon, releasing carbon dioxide (CO₂) to the atmosphere. Since CO₂ is the major greenhouse gas causing the warming that is melting the permafrost to begin with, this is a positive feedback—an effect that strengthens its own cause.

Some scientists had suggested that breakdown of plant material in the permafrost would make nutrients more available to plants, which, along with a longer growing season and the shift to large, shrubby plants, would cause plants to grow faster and remove CO₂ from the atmosphere, actually increasing ecosystem carbon storage and so acting as a brake on global warming. Experiments with tundra fertilization have shown that release of CO₂ from melted soils is greater than uptake by growing plants, so permafrost melting will indeed accelerate, rather than brake, global climate change. However, the exact balance between increased plant growth and CO₂ release is not yet known.

A second positive feedback to climate change from Arctic melting is the shrinkage of snow and ice cover. Snow and ice have high albedo (brightness) and reflect most of the solar energy that strikes them back into outer space. Open water and ground, being much darker, absorb far more solar energy. Heat absorbed by soil or water is eventually transferred, for the most part, to the atmosphere. Therefore, when snow melts to expose open ground or sea-ice melts to expose open water, this speeds up the climate warming that caused the melting.

The shift to shrubs accelerates global warming even apart from the issue of carbon storage. Observations of Alaskan tundra have found that when shrubs grow above a certain small size, their upper twigs remain exposed to sunlight all winter rather than being covered with snow. This greatly increases the amount of solar energy absorbed over any given area, and so adds to warming of the atmosphere.

For alpine tundra, the consequences of warming may be particularly harsh. Not only do alpine tundra biomes have limited area and no way to shift their location, but the isolation of these environmental islands has led, as on ocean islands, to the evolution of many distinct species. Many of these species are threatened with extinction as climate warms and treeline ascends.

See Also Arctic Melting: Greenland Ice Cap; Arctic Melting: Polar Ice Cap; Arctic People: Climate Change Impacts; Polar Bears.

BIBLIOGRAPHY

Periodicals

Foley, Jonathan A. “Tipping Points in the Tundra.” Science 310 (2005): 627-628.

Sturm, Matthew, and Tom Douglas. “Changing Snow and Shrub Conditions Affect Albedo with Global Implications.” Journal of Geophysical Research 110 (2005): 546-547.

Sturm, Matthew, et al. “Increasing Shrub Abundance in the Arctic.” Nature 411 (2001): 546-547.

Walker, Gabrielle. “A World Melting from the Top Down.” Nature 446 (2007): 718-721.

Web Sites

Roach, John. “Forests Have Replaced Tundra Due to Warming, Study Finds.” National Geographic News, June 22, 2007. <http://news.nationalgeographic.com/news/2007/03/070309-warming-tundra.html> (accessed October 16, 2007).

Larry Gilman

Tundra

Arctic tundra

Alpine tundra

Resources

Tundra is a generic name for an ecosystem characterized by low-growing vegetation in a climatically stressed environment with short and cool growing seasons. Latitudinal tundra occurs in the Arctic and to a much lesser extent in the Antarctic, where the environments are characterized by cool, short growing seasons. Altitudinal tundra occurs under a similar climatic regime, but at the tops of mountains.

After temperature, the second most important environmental factor affecting most tundra communities is moisture. Under wet conditions, sedge and grass-dominated meadow communities develop, while moist conditions favor a vegetation dominated by dwarf shrubs and herbaceous species, and dry sites have cushion plants and lichens. The flora of arctic and alpine

tundra share many structural characteristics, most genera, and some species. However, there are important environmental differences between these two tundra types, with thealpinetypebeing subjecttomuchlarger variations of daily temperature during the growing season, as well as more intense inputs of solar radiation during the day. In contrast, arctic tundra can experience continuous exposure to the sun’s rays, with 24-hour days for an extended period during the growing season.

Arctic tundra

Arctic tundra occurs in the northernmost parts of the northern hemisphere, intergrading across the latitudinal tree-line with the boreal forest to the south. In North America, arctic tundra occurs on all nonglaciated regions of the islands of northern Canada and on Greenland, as a northern fringe of Alaska and continental Canada, and penetrating to relatively southern latitudes in the vicinity of Hudson Bay, which acts as a climate-influencing extension of the cold Arctic Ocean. (An ecological analogue of arctic tundra occurs on the southernmost islands of the Southern Ocean and as a narrow fringe of parts of Antarctica. However, compared with arctic tundra, antarctic tundras are less well developed and have few species of plants.) The distribution of arctic tundra is determined by climate, generally occurring where the annual precipitation is less than about 2 in (5 cm) each year (including melted snow), and the average annual temperature is colder than 23° F (-5° C). Much of the arctic tundra covers permanently frozen ground, or permafrost, above which only the active layer—comprised of the surface 1.6 ft (0.5 m) or so— thaws during the growing season. Arctic tundra experiences continuous inputs of solar radiation during much of the growing season, a condition that can last for more than two months, depending on latitude. The incessant insolation during this time allows the vegetation to be relatively productive, as long as the availabilities of moisture and nutrients are not excessively constrained. During the arctic winter, when plants are dormant but some animals remain active, there is continuous night for several months, and extremely cold conditions.

There are several categories of arctic tundra vegetation. The low-arctic tundra occurs in southern areas. On wet sites, the low-arctic tundra of North America develops as relatively productive wet meadows dominated by a tussock-forming cotton grass (Eriophorum vaginatum ), while better-drained sites are dominated by shrubs such as willow (e.g, Salix glauca) and birch (e.g., Betula glandulosa ), growing to about 1.6 ft (0.5 m) in height. These sites also support herbaceous plants, such as arctic lupin (Lupinus arcticus ).

The high-arctic tundra is less productive and the plants are of lower stature. In North America, poorly drained wet meadows are dominated by graminoid plants, especially sedges (e.g., Carex membranacea and C. stans ) and cotton grass (Eriophorum angustifolium ). Drier sites are typically dominated by dwarf shrubs such as arctic willow (Salix arctica ), arctic heather (Cassiope tetragona ), mountain cranberry (Vaccinium vitis-idaea ), and arctic bilberry (V. uliginosum ), along with herbaceous plants such as lousewort (Pedicularis spp. ), grasses (such as Arctagrostis latifolia ), mosses, and lichens.

The polar desert is a very sparse tundra that occurs where climatic extremes of temperature and moisture availability allow only an incomplete cover of vegetation to develop. Such sites typically have a sparse cover of lichens and a few species of vascular plants, including cushion plants such as arctic avens (Dryas integrifolia ) and purple saxifrage (Saxifraga oppositifolia ), along with a few grasses and herbs. However, within the polar desert landscape there are occasional places that, because of their topography and drainage patterns, are relatively warm and moist throughout the growing season. These more moderate places are called high-arctic oases. They sustain a relatively lush growth of vegetation and, if the oasis is large enough, relatively large populations of animals.

The arctic tundra sustains only a few species of resident animals that remain active throughout the year. In the high-arctic tundra of North America, resident birds include the raven (Corvus corax) and rock ptarmigan (Lagopus mutus). Resident mammals include Peary caribou (Rangifer tarandus pearyi), muskox (Ovibos moschatus), arctic fox (Alopex lagopus), collared lemming (Dicrostonyx torquatus groenlandicus), and arctic hare (Lepus arcticus ). However, there is a much larger number of seasonally abundant animals. These include insects, some of which can be very abundant during the growing season, including dense populations of mosquitoes. Migratory species of birds include finches such as snow bunting (Plectrophenax nivalis ), Lapland longspur (Calcarius lapponicus ), and hoary redpoll (Acanthis hornemanni ); shorebirds such as Baird’s sand-piper (Calidris bairdii ) and red knot (Calidris canutus ); waterfowl such as oldsquaw duck (Clangula hyemalis ) and greater snow goose (Chen caerulescens atlantica ); and larids such as arctic tern (Sterna paradisaea ), glaucous gull (Larus hyperboreus ), and parasitic jaeger (Stercorarius parasiticus ).

Alpine tundra

Alpine tundra occurs in climatically stressed environments at high elevation. Alpine tundra can also occur on mountaintops at tropical latitudes, although it is much more common in temperate regions. Compared with the arctic tundra, alpine environments have much larger daily variations of temperature and solar radiation during the growing season. Because of the thinness of the atmosphere at high altitude, alpine tundra is also subject to large inputs of ultraviolet radiation, which can be an important biological stressor. Because the skies are often clear at high altitude, the surface cools very quickly at night, so that frost can be a daily occurrence during the growing season.

In general, alpine tundra is considerably richer in plant species than arctic tundra. At temperate latitudes, this occurs because alpine environments were not regionally obliterated by glacial ice during the most recent glaciations, so the component species were able to endure this period of intense climatic stress. This survival was made possible by the occur-rence of non-glaciated refugia where plants could survive on some mountaintops (these are called nunataks). In addition, as the climate deteriorated, alpine tundra could migrate to loweraltitude, nonglaciated parts of mountainous regions, as the tree-line moved downward. In contrast, almost all of the arctic tundra was destroyed by the extensive continental glaciers that covered northern regions during the most recent ice ages. It is believed that after deglaciation the arctic tundra was re-established by a northward migration of some of the plant species of alpine tundra. However, because only some species were capable of undertaking the extensive migrations that were necessary, the arctic tundra is relatively poor in species, compared with temperate alpine tundras.

There are relatively few animals that only occur in alpine tundra and not in other types of ecosystems. In North America some of the characteristic mammals of alpine tundra include a small relative of rabbits called the pika (Ochotona princeps ), and the hoary marmot (Marmota caligata ). The gray-crowned rosy finch (Leucostichte tephrocotis ), horned lark (Eremophila alpestris ), and water pipit (Anthus spinoletta ) all breed in alpine tundra of North America, but also in arctic tundra (the lark also breeds in other open habitats, such as prairie and fields).

Resources

BOOKS

Begon, M., C. R. Townsend, and J. L. Harper. Ecology:
From Individuals to Ecosystems. Malden, MA:
Blackwell, 2005.

Wiens, J. A., and M. R. Moss, eds. Issues and Perspectives in
Landscape Ecology. Cambridge, UK: Cambridge University Press, 2005.

Bill Freedman

Tundra

Tundra is treeless vegetation found at high elevation in mountains and in many landscapes of the Arctic. Collectively, ecosystems with tundra vegetation are grouped into the tundra biome. A distinction is usually made between Arctic tundra, which exists beyond the northern limit of tree growth, and alpine tundra, which exists above the elevational limit of tree growth in mountains. In mountains of the far north this distinction becomes blurred as tree lines descend to meet the northern limits of trees. Tundra is dominated by low-growing, perennial angiosperms and by mosses and lichens. Larger plants include grasses, sedges, herbs, and dwarf shrubs, but it is the lack of trees that most characterizes tundra. Plant species commonly found in tundra include sedges; grasses, including many of the genus Poa; willows, blueberries, dwarf birch, and other deciduous and evergreen shrubs or other low-growing woody plants; a host of herbaceous perennials, including many species of the genus Saxifragra, many members of the buttercup family, and several members of the rose family.

Climates of tundra regions are generally cold, and temperatures are commonly below freezing for much of the year, limiting the period of plant growth to a briefly thawed period during summer. Annual precipitation in tundra regions includes snow, although the amount of snow and total precipitation varies tremendously among different areas of tundra. Tundra regions are snow-covered much of the year, but the depth and duration of snow cover differs between locations. The tundra of the Sierra Nevada of California is characterized by heavy winter snow and little summer precipitation, while tundra in the Rocky Mountains generally has less snow but dependable summer rains. Precipitation in tundra regions of the Arctic is generally extremely low, often less than that found in many desert regions, but most soils nonetheless remain moist and may be waterlogged.

It may seem paradoxical that Arctic regions may have less precipitation than many deserts, yet they are covered by moist or wet tundra with numerous ponds and lakes. Low temperatures explain this apparent contradiction, limiting effects of evaporation and contributing to the formation of frost. Soils and materials beneath tundra are considered to be in a permafrost (perennially frozen) condition when they remain frozen for periods of two or more years. Permafrost is a condition generally characteristic of Arctic tundra soils but is also descriptive of isolated portions of the soils of alpine tundra regions. The top of the permafrost layer occurs a few inches to several feet below the surface and can extend downward for many feet. Permafrost soils drain poorly since the frozen soil is as impermeable as rock, and because much of the Arctic landscape is flat. A small amount of precipitation in the Arctic may be held in the thawed soil near the tundra surface, creating a moist landscape dotted with ponds and lakes. The flat Arctic plain is also patterned with irregularly shaped ridges and depressions, called polygons.

Soils of tundra regions are slow to develop due largely to low temperatures and limited periods of thaw. A variety of soil types may develop with time, depending primarily upon moisture or the degree of saturation. Wet tundra, with poor aeration and slow decomposition of plant roots, mosses, and other organic matter, produces highly organic soils, while well-drained tundra is characterized by mineral soils. The soil supply of nitrogen, phosphorus, or other elements needed by plants is often low and limits plant growth, and thus tundra regions generally support fewer animals than grasslands and other biomes. Despite low net primary productivity (plant growth potentially available to grazing animals), tundra regions support a variety of mammals, birds, and insects. Arctic tundra herbivores (plant eaters) include caribou, musk ox, lemmings, insects, hares, ground squirrels, and ptarmigan. Carnivores (eaters of insects or other animals) include many birds, especially waterfowl and shorebirds (that appear only in summer), snowy owls, jaegers, and ravens. Other important Arctic carnivores include Arctic fox, wolves, brown bears, and mosquitoes. The fauna of alpine tundra is variable but commonly includes various species of mountain sheep and/or mountain goats, voles and other rodents, bears, eagles, insects, and a variety of animals characteristic of the adjacent forests that sporadically use tundra habitats.

Within both Arctic and alpine regions exist extremes of vegetation considered atypical of tundra. Many areas within the Arctic are true desert; vegetation scientists classify these areas as polar desert. Tropical high mountains exhibit treeless zones at high elevations, sharing many similarities with the alpine tundra of temperate regions, but the lack of seasons, the large diurnal temperature variations, and the presence of distinct plant growth forms are clear differences. Tropical alpine vegetation commonly includes one plant life form not found in other tundra regions: the tall columnar rosette. In the tropical alpine of Africa this life form is represented by members of the genus Lobelia, in the Andes of South America by members of the genus Espeletia, and in high mountains of Java it is represented by tree ferns. The absence of this life form in Arctic and temperate alpine tundra probably reflects the importance of wind in shaping plants of these ecosystems. Floristic similarities between tropical alpine and temperate alpine or even Arctic tundra regions include genera or species of mosses, lichens, and occasionally vascular plants that are held in common.

During glacial periods of the past, much of the area now covered by the Bering Sea was a land mass. This Bering land bridge, connecting North America and Eurasia, allowed plant and animal populations to migrate between Northern Hemisphere continents of Eurasia and North America. Today many tundra genera, including both plants and animals, have circumpolar distributions (surrounding the northern parts of the world). Since species migrations were made possible during the cold periods of the Pleistocene with lowered sea levels due to great masses of ice on land, tundra-like vegetation formed over great expanses in the Northern Hemisphere. Today isolated alpine regions show remarkable similarities in flora and fauna to those of the Arctic echoing a common tundra heritage.

see also Biogeography; Biome.

Kim Moreau Peterson

Bibliography

Archibold, O. W. Ecology of World Vegetation. London: Chapman & Hall, 1995.

Billings, William Dwight. "Alpine Vegetation." In North American Terrestrial Vegetation, 2nd ed., ed. Michael G. Barbour and William Dwight Billings. Cambridge: Cambridge University Press, 2000.

Bliss, Lawrence C. "Arctic Tundra and Polar Desert Biome." In North American Terrestrial Vegetation, 2nd ed., ed. Michael G. Barbour and William Dwight Billings. Cambridge: Cambridge University Press, 2000.

Chapin, F. Stuart III, Robert L. Jefferies, James F. Reynolds, Gaius R. Shaver, and Josef Svoboda, eds. Arctic Ecosystems in a Changing Climate: An Ecophysiological Perspective. San Diego, CA: Academic Press, 1992.

Wielgolaski, F.E., ed. "Polar and Alpine Tundra." In Ecosystems of the World, Vol. 3.

New York: Elsevier Science Ltd., 1997.

COMMON PLANT SPECIES FOUND IN TUNDRA

Sedges (Cyperaceae family)

Carex aquatilis

Carex bigelowii

Eriophorum vaginatum

Eriophorum scheuchzeri

Grasses (Poaceae family)

Poa arctica

Poa alpina

Alopecurus alpinus

Arctophila fulva

Deschampsia caespitosa

Arctagrostis latifolia

Trisetum spicatum

Willows (Salicaceae family)

Salix arctica

Salix rotundifolia

Salix reticulata

Blueberries and Heaths (Ericaceae family)

Vaccinium uliginosum

Vaccinium vitis-idaea

Arctostaphylos alpina

Arctostaphylos uva-ursi

Ledum palustre

Cassiope tetragona

Empetrum nigrum

Dwarf birch Betula glandulosa Herbaceous perennials

Saxifrage family

Saxifragra oppositifolia

Saxifragra cernua

Saxifragra caespitosa

Ranunculaceae (Buttercup family)

Ranunculus nivalis

Anemone parviflora

Caltha leptosepala

Rosaceae (Rose family)

Geum Rosii

Dryas integrifolia

Potentilla species Rubus species

Brassicaceae (Mustard family)

Draba species

Artemisia species

Lupinus species

Castilleja species

Pedicularis species

Senecio species

Silene species

Tundra

Tundra is a generic name for a low-growing ecosystem found in climatically stressed environments with short and cool growing seasons . Latitudinal tundra occurs in the Arctic and to a much lesser extent in the Antarctic, where the environments are characterized by cool, short growing seasons. Altitudinal tundra occurs under a similar climatic regime, but at the tops of mountains .

After temperature , the second most-important environmental factor affecting most tundra communities is moisture. Under wet conditions, sedge and grass-dominated meadow communities develop, while moist conditions favor a vegetation dominated by dwarf shrubs and herbaceous species , and dry sites have cushion plants and lichens . The vegetation of arctic and alpine tundras share many structural characteristics, most genera, and some species. However, there are important environmental differences between these two tundras, with the alpine type being subject to much larger variations of daily temperature during the growing season, as well as more intense inputs of solar radiation during the day. In contrast, arctic tundra can experience continuous exposure to the sun's rays, with 24-hour days for an extended period during the growing season.

Arctic tundra

Arctic tundra occurs in the northern most parts of the Northern Hemisphere, intergrading across the latitudinal tree-line with the boreal forest to the south. In North America , arctic tundra occurs on all non-glaciated regions of the islands of northern Canada and on Greenland, as a northern fringe of Alaska and continental Canada, and penetrating to relatively southern latitudes in the vicinity of Hudson Bay, which acts as a climate-influencing extension of the cold Arctic Ocean. (An ecological analogue of arctic tundra occurs on the southernmost islands of the Southern Ocean and as a narrow fringe of parts of Antarctica . However, compared with arctic tundra, antarctic tundras are less well developed and have few species of plants.) The distribution of arctic tundra is determined by climate, generally occurring where the annual precipitation is less than about 2 in (50 cm) each year, and the average annual temperature is colder than 23oF (-5oC). Much of the arctic tundra covers permanently frozen ground, or permafrost , above which only the active layer—comprised of the surface 1.6 ft (0.5 m) or so—thaws during the growing season. Arctic tundra experiences continuous inputs of solar radiation during much of the growing season, a condition that can last for more than two months, depending on latitude. The incessant insolation during this time allows the vegetation to be relatively productive, as long as the availabilities of moisture and nutrients are not excessively constrained. During the arctic winter, when plants are dormant but some animals remain active, there is continuous night for several months, and extremely cold conditions.

There are several categories of arctic tundra vegetation. The low-arctic tundra occurs in southern areas. On wet sites, the low-arctic tundra of North America develops as relatively productive wet meadows dominated by a tussock-forming cottongrass (Eriophorum vaginatum), while better-drained sites are dominated by shrubs such as willow (e.g, Salix glauca) and birch (e.g., Betula glandulosa), growing to about 1.6 ft (0.5 m) in height. These sites also support herbaceous plants, such as arctic lupin (Lupinus arcticus).

The high-arctic tundra is less productive and the plants are of lower stature. In North America, poorly drained wet meadows are dominated by graminoid plants, especially sedges (e.g., Carex membranacea and C. stans) and cottongrass (Eriophorum angustifolium). Drier sites are typically dominated by dwarf shrubs such as arctic willow (Salix arctica), arctic heather (Cassiope tetragona), mountain cranberry (Vaccinium vitis-idaea), and arctic bilberry (V. uliginosum), along with herbaceous plants such as lousewort (Pedicularis spp.), grasses (such as Arctagrostis latifolia), mosses, and lichens.

The polar desert is a very sparse tundra that occurs where climatic extremes of temperature and moisture availability allow only an incomplete cover of vegetation to develop. Such sites typically have a sparse cover of lichens and a few species of vascular plants, including cushion plants such as arctic avens (Dryas integrifolia) and purple saxifrage (Saxifraga oppositifolia), along with a few grasses and herbs. However, within the polar desert landscape there are occasional places that, because of their topography and drainage patterns, are relatively warm and moist throughout the growing season. These more moderate places are called high-arctic oases. They sustain a relatively lush growth of vegetation and, if the oasis is large enough, relatively large populations of animals.

The arctic tundra sustains only a few species of resident animals that remain active throughout the year. In the high-arctic tundra of North America, resident birds include the raven (Corvus corax) and rock ptarmigan (Lagopus mutus). Resident mammals include Peary caribou (Rangifer tarandus pearyi), muskox (Ovibos moschatus), arctic fox (Alopex lagopus), collared lemming (Dicrostonyx torquatus groenlandicus), and arctic hare (Lepus arcticus). However, there is a much larger number of seasonally abundant animals. These include insects , some of which can be very abundant during the growing season, including dense populations of mosquitoes . Migratory species of birds include finches such as snow bunting (Plectrophenax nivalis), Lapland longspur (Calcarius lapponicus), and hoary redpoll (Acanthis hornemanni); shorebirds such as Baird's sandpiper (Calidris bairdii) and red knot (Calidris canutus); waterfowl such as oldsquaw duck (Clangula hyemalis) and greater snow goose (Chen caerulescens atlantica); and larids such as arctic tern (Sterna paradisaea), glaucous gull (Larus hyperboreus), and parasitic jaeger (Stercorarius parasiticus).

Alpine tundra

Alpine tundra occurs in climatically stressed environments at high mountainous altitudes. Alpine tundra can even occur on mountaintops at tropical latitudes, although this vegetation type is much more common in temperate regions. Compared with the arctic tundra, alpine environments have much larger daily variations of temperature and solar radiation during the growing season. Because of the thinness of the atmosphere at high altitude, alpine tundra is also subject to large inputs of ultraviolet radiation, which can be an important biological stressor. Because the skies are often clear at high altitude, the surface cools very quickly at night, so that frost can be a daily occurrence during the growing season.

In general, alpine tundra is considerably richer in plant species than arctic tundra. At temperate latitudes, this occurs because alpine environments were not regionally obliterated by glacial ice during the most recent glaciations, so the component species were able to endure this period of intense climatic stress. This survival was made possible by the occurrence of non-glaciated refugia where plants could survive on some mountaintops (these are called nunataks). In addition, as the climate deteriorated, alpine tundra could migrate to lower-altitude, non-glaciated parts of mountainous regions, as the tree-line moved downwards. In contrast, almost all of the arctic tundra was destroyed by the extensive continental glaciers that covered northern regions during the most recent ice ages . It is believed that after deglaciation the arctic tundra was re-established by a northward migration of some of the plant species of alpine tundra. However, because only some species were capable of undertaking the extensive migrations that were necessary, the arctic tundra is relatively poor in species, compared with temperate alpine tundras.

There are relatively few animals that only occur in alpine tundra and not in other types of ecosystems. In North America some of the characteristic mammals of alpine tundra include a small relative of rabbits called the pika (Ochotona princeps), and the hoary marmot (Marmota caligata). The gray-crowned rosy finch (Leucostichte tephrocotis), horned lark (Eremophila alpestris), and water pipit (Anthus spinoletta) all breed in alpine tundra of North America, but also in arctic tundra (the lark also breeds in other open habitats, such as prairie and fields).

Resources

books

Barbour, M.G., and W.D. Billings. North American TerrestrialVegetation. Cambridge: Cambridge University Press, 1988.

Barbour, M.G., J.H. Burk, and W.D. Pitts. Terrestrial PlantEcology, 2nd ed. Don Mills, Ontario: Benjamin/Cummings Pub. Co., 1987.

Bill Freedman