The Taiga or Boreal Forest

Brule River

Climate:  

Climate in the taiga is cold, with average annual temperatures from about +5°  to -5°  C (see figure at right).  I always find it interesting to note that one location with a coniferous forest, Yellowstone National Park in Wyoming, has an average annual temperature of only 1° C!   Precipitation varies, from about 20 cm of precipitation per year to over 200 cm.  Much of the precipitation, of course, is in the form of snow.  The winters are cold and long; summers are relatively short and cool.  With snowmelt and low temperatures, there is little evaporation in the summer, so the ground is usually very moist during the growing season.  Add to the availability of water the fact that the short summer has extremely long day length at the northerly latitudes and you have a situation for explosive plant growth in the summer. Still the growing season is short, usually less than 3 months.

 

 

 

World Distribution:  

The map  to the left shows the boreal forests, which extend in broad bands across North America and Eurasia.  The boreal forest, also known as Taiga, a Russian word that recognizes the swampy nature of much of this forest in the summer, lies to the south of the tundra and to the north of deciduous forests and grasslands.  There is no comparable zone in the southern hemisphere, probably because there is little land area there with the proper climate (cold temperatures in the southern hemisphere being moderated by close proximity to the sea; at high latitudes in the southern hemisphere most land is relatively close to the ocean, unlike the northern hemisphere.  Also, circulation of the oceans in the southern hemisphere is not blocked by the continental land masses to the same extent as it is in the north.    It should be noted that a similar coniferous forests exist on some mountains of the alpine biome; on this map the southern extension of the boreal forests into eastern North America along the Appalachian Mountains is shown, while the coniferous forests of the western North American mountains is not.

 

 

 

Indicator Plant Species:

Pine cones closed (left) and open (right)

Pine cones closed (left) and open (right)

Pine Cone

Pine Cone

Many plant species are found in the Taiga, but coniferous trees are obviously the dominant plant form.  These trees shed snow easily, and they retain their needles through the winter. The needles themselves are well-adapted, with thick waxy coatings and small surface area, to resist cold conditions and minimize water loss, an important consideration even in the swampy taiga where water may be frozen much of the year.  Together, these adaptations  mean that even in cool conditions, if the temperature rises above freezing during the day photosynthesis can proceed.  Broadleaf plants usually lose their leaves at the onset of freezing conditions in the fall and will not regrow them until most of the danger of frost has passed.  This means that the growing season of broad-leafed trees is much shorter than it is for coniferous trees, and the advantage the coniferous trees gain allows them to dominate in the cold taiga climate (note that broad leaves are much more efficient, so if conditions are favorable (warm and moist) they are the preferred leaf type).

Important conifer types include firs and pines (right, with the fir on the left of the image and the pine on the right), spruces, hemlocks, and larches.  All of these tree types bear cones of one sort or another (above).  The seeds are retained in these structures until they open and cast the seeds out, often from a considerable height.  Some species of birds and mammals may also open the cones foraging for the seeds.  With two seeds per scale, it is likely that as the animal breaks one seed loose the other will fall free to the forest floor.  Some cones do not open until there has been a fire, but since fire is not an important aspect of the taiga that is probably not the case for most taiga conifers.

 

Fir (left and pine (right)

Fir (left and pine (right)

   

Polytrichum Moss.

Polytrichum Moss.

British Soldiers, a Lichen

British Soldiers, a Lichen

In addition to the conifers, mosses (above and below) and lichens are also important in the taiga and may be an important part of the diet for many animals.  Please note that the species shown here are not necessarily found in the Taiga.

 

Giant Sequoia (Sequoiadendron giganteum) are not really a boreal species (they live in the Sierra Nevada of California, and are probably more of a temperate rainforest species.  I put them here because they are neat.

Another Lichen

Another Lichen

Moss growing in coniferous forest at Yellowstone National Park

Moss growing in coniferous forest at Yellowstone National Park

Giant Sequoia (Sequoiadendron giganteum)

Giant Sequoia (Sequoiadendron giganteum), Mariposa Grove, Yosemite National Park

Indicator Animal Species:

Bobcat Felis rufus

Bobcat Felis rufus - Captive Specimen at Cleveland Museum of Natural History.

 

Elk (Wapiti) (Cervus elaphus) Yellowstone National Park

Elk (Wapiti) (Cervus elaphus) Yellowstone National Park

Numerous animal species are found in coniferous forests.  Several are arrayed here; others are shown with the tour section below.  

Among the main carnivores of the boreal forest are a number of felids (cats) and canids (dogs).  The cats range in size from the Siberian Tiger (below), down through the lynx to the bobcat (above).  The Amur (Siberian) Tigers are but one subspecies of this large Asian cat which is known from the tropics of India and Indonesia all the way north to the boreal forests of Russia.  

The Bobcat is a much smaller cat with a range that extends far into the temperate zone, unlike its larger and more northerly relative the lynx (not pictured).  

Herbivores range in size from the large members of the deer family such as the Elk (above right) to insects on the small end of the scale.  The name Elk needs some explanation.  In Europe, the term Elk is applied to what we in North America would call a moose, and the animal they call a Red Deer is probably in the same species as our Elk.  To avoid at least some confusion, a number of authorities in the United States and Canada have begun using a Native American name, Wapiti, in place of the name Elk (of course, scientists use the scientific name Cervus elaphus and avoid ALL confusion).

Among the smaller mammalian herbivores are the arboreal (tree-living) Porcupine (right) and the terrestrial Snowshoe Hare (below right).  The Snowshoe Hare pictured here is just beginning its winter transformation; the brown coat that camouflaged it so well in the summer and fall is beginning to be shed and replaced with white fur that will help hide it in the winter snows. 

Porcupine Erethizon dorsatum

Porcupine (Erethizon dorsatum) Baxter State Park, Maine

 

Amur Tigers (Panthera tigris altaica) AKA Siberian Tiger.  Cleveland Zoo

Amur Tigers (Panthera tigris altaica) AKA Siberian Tiger.  Cleveland Zoo.

 

Snowshoe Hare (Lepus americanus)

Snowshoe Hare (Lepus americanus) - Captive Specimen

Ecological Notes:

The big story in the taiga is adaptation to winter cold and snow.  As seen above, the Snowshoe Hare with its large paws (for running over the snow) and white fur (to blend in) is well adapted for life in the snow.  Other animals may burrow beneath the snow and forage for their food in tunnels on and in the forest floor; they are insulated from the worst cold of winter by the snow.  Still others will hibernate throughout the winter.  The cold, however, does take its toll; compared to temperate forests there are fewer species of plants and animals, and among the animals the cold-blooded amphibians and reptiles are noticeably reduced.  Bird species mostly deal with the cold by migrating south during the cold winter and returning in the spring.  During the brief summer, the very long days that exist at high latitudes means a lot of photosynthesis can take place, and this profusion of plant growth is accompanied by a burst of insect activity.  Birds migrating to the taiga in summer are able to take advantage of the new growth and insect abundance - not to mention the reduced competition in the vast forests - and raise their young.  

We've already dealt with how the plants deal with the cold in the section on indicator plants, above.  One other aspect of the boreal forest with regard to plants should be mentioned, however.  The cold, as well as the acid conditions produced by the fallen conifer needles, reduces the rate of decomposition on the forest floor.  This in turn reduces the availability of nutrients in the soils, and competition for nutrients by plants growing in the boreal forest may be stiff.  In addition, many of the soils are wet and bog-like during the brief summer when the snow finally melts.  In many places, the conditions for plants are more reminiscent of a bog.  Carnivory, parasitism, use of mycorrhizae - all of these are just a few of the tricks that are used by boreal forest plants.

 

Threats:

Hydroelectric Project, Quebec

Hydroelectric Project, Quebec

Perhaps the biggest threat to the boreal forest today is exploration and development of oil and natural gas reserves.  From Alaska to Canada to Russia, it is estimated that vast amounts of petroleum products lie under these forests.  Increased instability in the Middle East, more effective technology for working in the cold, and the high demand for fossil fuels are pushing exploration and development into areas once thought impossible to exploit.  It is not clear whether the slow-growing coniferous forests can recover.

Other threats abound.  Perhaps the most serious is Global Warming; as the planet warms the southern reaches of the boreal forest will become warm enough for deciduous trees to outcompete the conifers and replace them.  It is not clear whether the tundra areas to the north will support forests even under warmer conditions, and it is less clear if the trees will be able to move north rapidly enough in any event. There is some evidence to suggest that additional carbon dioxide and methane - both greenhouse gasses - will be liberated from warmer tundra and taiga soils as the built up detritus of thousands of years is finally free to decompose.  This additional release of greenhouse gasses could accelerate global warming even further.

  Logging is always a threat; unless carefully managed these forests are very slow to regrow and corporate pressures may reduce the amount of management and/or accelerate cutting beyond what can be sustained.  Large areas of boreal forest have also been flooded as part of hydroelectric projects (right).

 

 

 

Tour:

Half Dome - Yosemite National Park

Half Dome - Yosemite National Park

Bobcat Felis rufus

Bobcat Felis rufus

Many of the great American National Parks in the west are covered with a coniferous forest that resembles in many ways the boreal forests of the north (above).  Yosemite National Park, for instance, mostly lies at an elevation that is cool enough to select for coniferous trees over deciduous ones.  These alpine coniferous forests differ from the boreal coniferous forests of the north, however, in a number of important ways.  Usually the slopes are steeper and the ground rockier; while the trees may resemble a boreal forest the undergrowth does not.

Mammalian predators in the coniferous forest range from the small, like the bobcat (above right), which feeds on rodents, hares and other small prey, to the Grizzly (right) which is capable of taking down very large prey indeed (although a surprising majority of their diet consists of plant material, often dug from the ground with the help of the mass of muscles that makes up the characteristic hump of the grizzly's back).  Much of the meet that grizzlies eat may be scavenged from the carcasses of large herbivores killed by winter conditions or other predators, such as wolves.  Reading the journals of Lewis and Clark, the first Europeans to encounter the grizzly, one gets the sense that the members of the Corps of Discovery were being stalked as prey by the grizzlies they encountered. It often took several of the best marksmen in the country, armed with the finest weapons of the time, to stop a single bear.  It makes one wonder how Native Americans were able to coexist with these bears.

The Spruce Grouse (below) isn't much of a threat to human life.  Restricted to the boreal forest, it penetrates only into the northernmost parts of the northernmost lower 48 states (and is present in a wide swath across Canada and Alaska).  A secretive, rarely seen bird, we were fortunate to see a male displaying on Great Wass Island in Maine during our 1998 expedition.

Grizzly Bear - Ursus arctos - Cleveland Metroparks Zoo

Grizzly Bear - Ursus arctos - Cleveland Metroparks Zoo

Spruce grouse Falcipennis canadensis - Great Wass Island, Maine

Spruce grouse Falcipennis canadensis - Great Wass Island, Maine

Grizzly Bear

Grizzly Bear - Ursus arctos - Yellowstone NP

Gray Fox - Urocyon cinereoargenteus - Captive Specimen

Gray Fox - Urocyon cinereoargenteus - Captive Specimen

Red Fox - Vulpes vulpes - Captive Specimen

Red Fox - Vulpes vulpes - Captive Specimen

Gray Fox - Urocyon cinereoargenteus - Captive Specimen

Gray Fox - Urocyon cinereoargenteus - Captive Specimen

Canids (dogs) are important carnivores in the boreal forest.  In North America, the range in size from large (wolves, an expedition is planned for fall 2006 to get pictures of them) to medium (coyotes, see the grassland biome) to small (foxes, pictured here above and left).  All of the canids are very adaptable and can be found (or could be found) over a wide range of biomes in North America.  Foxes, which prey primarily on small herbivores such as rodents, are well at home in the boreal forests.  The Red Fox (above) is found in Europe, North America, Asia (and has been introduced into Australia) and its range extends from the tundra to the tropics, but the boreal forest seems to be an anchor in its range.  The Gray Fox, on the other hand, is restricted to North America and is more southern in its distribution, only reaching the fringe of the boreal forest (though it may be more common in alpine coniferous forests).

The Porcupine, below, is well-protected against canid and other predators.  Its hindquarters are covered with long barbed quills which penetrate the skin of a predator (particularly near the mouth) and which are difficult to remove once they have attached.  The hind view of this porcupine is no accident; with the quills on their backs porcupines quickly turn tail and don't worry too much about close pursuit.  They spend much of their time in the trees and feed exclusively on vegetation.  Primarily a creature of the north woods, they can also be found in alpine areas, grasslands and even deserts.  They do have a few predators, including bobcats and larger members of the weasel family including fishers and wolverines.

The tiny saw-whet owl is sometimes seen in the north woods.  In the winter, it may migrate south into temperate forests, but its bread-and-butter hunting grounds are the coniferous forests, including alpine forests in the west.  They prefer a forest with at least a few deciduous trees, for these are more likely to harbor boring insects than are the resin-laden conifers.  And burrowing insects mean woodpeckers, and woodpeckers mean cavities for the saw-whet owl to nest in. Like most owls, they feed on small mammals such as mice and voles; they may also take small birds, reptiles and amphibians.

Northern Saw-whet Owl - Aegolius acadicus - Maine

Northern Saw-whet Owl - Aegolius acadicus - Maine

Porcupine (Erethizon dorsatum) Baxter State Park, Maine

Porcupine (Erethizon dorsatum) Baxter State Park, Maine

Elk (Wapiti) (Cervus elaphus) Yellowstone National Park

Elk (Wapiti) (Cervus elaphus) Yellowstone National Park

Elk (Wapiti) (Cervus elaphus) Yellowstone National Park

Elk (Wapiti) (Cervus elaphus) Yellowstone National Park

Bull Moose - MaineThe boreal forest and its alpine cousins are host to a wide variety of deer, ranging from the large moose (inset, right) to the whitetail deer.  All of these large herbivores prefer the cool forest lest they overheat in the sun, but all need open land on which to graze.  Of the deer, moose are perhaps best adapted to wetlands and thrive in the boggy boreal forest.  The wapiti prefers mature forest (and more open land in the winter), while the deer move between forest and grassland constantly.  In addition to grass and other ground plants, deer of all types can graze on a variety of plant materials including leaves and berries picked from trees overhead; often these are taken by the deer standing on its hind legs.  A forest with too many deer may have a "browse line" where the height of the deer is demonstrated graphically by the absence of green vegetation anywhere in reach of the deer.  Such heavy grazing pressure can dramatically alter plant communities.  The moose is also a heavy grazer, but compared to the other species it also spends a lot of its time consuming aquatic plants.  Mule Deer and White-tailed deer coexist in the western US (the Mule Deer is not found in the east) with the Mule deer preferring open, dry areas to the moister, more covered areas sought out by the smaller white-tails.

Cow Moose (Alces alces) - Baxter State Park, Maine

Cow Moose (Alces alces) - Baxter State Park, Maine

White-tailed Deer (fawns) - Odocoileus virginianus - The Wilds, Ohio

White-tailed Deer Fawns - Odocoileus virginianus - The Wilds, Ohio

Mule Deer Odocoileus hemionus - Theodore Roosevelt National Park

Mule Deer Odocoileus hemionus - Theodore Roosevelt National Park

 

Black-fly larva (Simuliidae)

Black-fly larva (Simuliidae)

Moose (Alces alces) - Glacier National Park

Moose (Alces alces) - Glacier National Park

Boreal Forest - Quebec

Boreal Forest - Quebec

Continuing with moose (above) we once again see that these large deer do like to spend time in water.  I have seen arguments that one of the reasons they prefer to spend time in water is because of the huge populations of black flies (above left, it is the adult females that bite to obtain blood protein to produce eggs).  Black flies, like many insects, are very abundant during the short boreal forest summer, another attraction for the birds that migrate there to raise their young.  

To the left is an aerial view of the boreal forest in Quebec.  This picture, taken in January, shows snow on the ground - as well as the green needles of the coniferous trees, ready to photosynthesize as soon as temperatures allowed.  It would take deciduous trees weeks to grow the leaves required to take advantage of a quick warm spell.

Below are two views of Yellowstone National Park.  On the left, note the thick duff on the forest floor.  Acids from the needles and cold temperatures prevent decomposition and allow material to build up.  This is less of a fire hazard in the boggy, sodden boreal forest than in the well-drained western alpine forests, and indeed wildfires often rage through the latter.

Forest Floor - Yellowstone National Park

Forest Floor - Yellowstone National Park

Taiga at Sunset - Yellowstone National Park

Taiga at Sunset - Yellowstone National Park

Giant Sequoia (Sequoiadendron giganteum), Mariposa Grove, Yosemite National Park

Giant Sequoia (Sequoiadendron giganteum), Mariposa Grove, Yosemite National Park

 

Giant Sequoia (Sequoiadendron giganteum), Mariposa Grove, Yosemite National Park

Giant Sequoia (Sequoiadendron giganteum), Mariposa Grove, Yosemite National Park

These pictures show off the Giant Sequoias of the Mariposa Grove in Yosemite National Park.  The Sequoias are an interesting species not just because of their great size.  Like their large brethren the coastal redwoods, they require more water than the typical conifer, and they find it here on the western slope of the Sierra Nevada as moist air coming off the Pacific Ocean rises, cools, and loses its moisture in the form of rain and snow over the western slopes.  This microclimate isn't so wet as to be classified as a temperate rain forest, but it is obviously different than the climate of the surrounding Sierra Nevada which supports a more typical conifer assemblage.

 Giant Sequoia (Sequoiadendron giganteum), Mariposa Grove, Yosemite National Park

Giant Sequoia (Sequoiadendron giganteum), Mariposa Grove, Yosemite National Park

Giant Sequoia (Sequoiadendron giganteum), Mariposa Grove, Yosemite National Park

Giant Sequoia (Sequoiadendron giganteum), Mariposa Grove, Yosemite National Park

Giant Sequoia (Sequoiadendron giganteum), Mariposa Grove, Yosemite National Park

Giant Sequoia (Sequoiadendron giganteum), Mariposa Grove, Yosemite National Park

Giant Sequoia (Sequoiadendron giganteum), Mariposa Grove, Yosemite National Park

Giant Sequoia (Sequoiadendron giganteum), Mariposa Grove, Yosemite National Park

Tuolumne Meadows. Yosemite National Park

Tuolumne Meadows. Yosemite National Park

Brule River, Wisconsin

Brule River, Wisconsin

Birch Forest, Upper Peninsula, Michigan

Birch Forest, Upper Peninsula, Michigan

Water plays an important role in the boreal forest (or the alpine forests of the west, for that matter).  The Brule River, above, drains a relatively flat boreal forest and the dark brown water carries the stains from the tannins and other plant products produced in the leaves of the species occupying the boggy forest floor.  In contrast, the water drains more quickly from the inclined meadows at Tuolumne in Yosemite (above left), where the water runs more clear.  Both streams are relatively free of silt and other evidence of soil erosion; both no doubt swell in the spring with snowmelt runoff.

To the left is a birch forest on the edge of the boreal forest in the upper peninsula of Michigan.  Birches are among the most cold-tolerant of the deciduous trees and their presence is usually a sign that one is at the boundary of a coniferous and a deciduous forest. Aspens play a similar role in the mountains of the western United States.

Below - Northern and southern deer.  Reindeer (Caribou in the New World) are the most northern deer species and are relatively large (but not as big as moose or elk).  They frequent not only the tundra (where they are featured here) but the boreal forests as well.  The little whitetail pictured below is a mature male, but because it lives far south in Florida it has a much smaller body size.  There is a general tendency towards larger body size within a species (or within closely related species) as one moves towards the poles.  This apparently has to do with thermoregulation, larger animals are more efficient at retaining body heat in cold climates, while smaller animals can more easily cool off in warmer climates.  The rule is known as Bergman's Rule.

 Reindeer (Rangifer tarandus)

 Reindeer (Rangifer tarandus)

White-tailed Deer Buck - Odocoileus virginianus - Corkscrew Swamp Sanctuary, Florida


White-tailed Deer Buck - Odocoileus virginianus 

- Corkscrew Swamp Sanctuary, Florida

Birches Left: More birches, this time in northern Wisconsin. The taiga extends down into the northernmost of the contiguous United States, but much of it is transitional to the deciduous forest, as seen here.
Right: This boreal forest in northern Wisconsin has a complex understory including ferns and asters. Forest flowers

 

Updated 10/14/2013

 

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