Images © by James L. Reveal, Norton-Brown Herbarium, University of Maryland, unless otherwise credited.

Mixed pine and aspen forest -- Montane Forest Biome -- Colorado

• A. Biogeography: the study of animal and plant distributions; known as zoogeography and phytogeography, respectively
  B. Biome: any one of the several major terrestrial ecosystems which may be characterized by the presence of specific plants and animals, climate, and soil conditions in a specific geographic setting. In terms of area, it is composed of several plant communities and ecosystems [Strongly recommended as a review]. The boundary between biomes is termed an ecotone and may be important in our understanding of speciation and dispersal. Many plants in a given biome may be an endemic, that is found no where else in the world; diversity differs considerably between biomes
  C. Biomes of North America: (1) tundra, (2) taiga, (3) montane forests, (4) temperate rain forests, (5) mixed conifer and sclerophyllous hardwood forests, (6) temperate deciduous forests, (7) chaparral, (8) grasslands, (9) deserts, (10) tropical forests.
  D. The world as a whole is often divided into six biogeographic kingdoms:
  • 1. Boreal kingdom - see a map of the world
    • a. Arctic and subarctic region
      b. East Asian region
      c. Western and Central Asian region
      d. Mediterranean region
      e. Eurosiberian region
      f. North American region

    2. Paleotropical kingdom

    • a. Malesian subkingdom
      b. Indoafrican subkingdom
      c. Polynesian subkingdom

    3. Neotropical kingdom
    4. South African kingdom
    5. Australian kingdom
    6. Antarctic kingdom

    • a. Subantarctic region
      b. Antarctic region

II. Role of Climate

• A. Biomes controlled by climate: extremes of temperatures and precipitation more significant than averages.
  B. Daily and seasonal cycles influence prevailing winds
  • 1. Climate is global and is ever changing - see current global weather
    2. Important features include the jet stream and the associated cloud patterns as well as ocean currents; the seasons of the year are determined by the tilt of the earth - see today's jetstream
    3. Weather moves west to east in North America.
    4. Precipitation influenced by physiographic features - distribution, size and height of mountain ranges, locations of oceans, etc., the amounts differing from biome to biome.
    • a. Rainshadow effect
      b. Slope: N vs. S, E vs. W
      c. El Nino and Humboldt currents affect flora and fauna of the Galapagos Islands.

  C. Elevation

  • 1. Biomes at higher elevations in more southern latitudes.
    2. With sufficient elevation, numerous biomes can be found on a single mountain range.
    3. Often subdivided into "life zones" such as the Merriam Model or the Holdridge model generally used today, it being adopted because it addresses the nature of tropical montane features. See this site for a summary of his life zone divisions.

  D. Change over time:

  • 1. Climatic changes over last 21.000 years.
    2. Tectonic plates
    

See the United States Forest Service's Ecosystem Provinces map
and online summary for details.

III. Tundra - check out this introduction

• A. Location:
  • 1. Northernmost and circumpolar in northern hemisphere.
    2. Northern Alaska and Canada, all of Hudson Bay in east.

  B. Features and polar environments

  • 1. Dry: (6-14 in or 15-35 cm) as summer and fall cold rains.
    2. Cold: Freezing temperature can occur any day of the year and temperatures rarely exceed 15° C even during the warmest of months. The growing season varies from 60 to 100 days a year.
    3. Soils: Wet, shallow, often frozen or with permafrost - for a detailed discussion of permafrost, which is found on 13% of the earth's surface, see this site; shallow lakes, known as polygons
    4. Representative subdivisions of the tundra biome in North America:
    • a. Arctic Coastal Plain
      b. Arctic Foothills
      c. Brooks Range
      d. Interior Forested Lowlands and Uplands
      e. Interior Highlands
      f. Interior Bottomlands
      g. Yukon Flats
      h. Ogilvie Mountains
      i. Subarctic Coastal Plains
      j. Seward Peninsula
      

    4. Similar regions in Canada include (a) the Arctic Cordillera, (b) the Northern Arctic Ecozone, and (c) the Southern Arctic Ecozone.
    5. One physical feature of the region (both here and in the montane biome) is the force of glaciation caused by a glacier. Glaciers are particularly impressive and massive in Antarctica. The consequences of past glaciation may be seen in Yosemite National Park in California.

  C. Vegetation:

  • 1. Low shrubs and herbs, mostly graminoids - grass-like plants. The inflorescence of Carex seen to the left is a member of the sedge family rather than the grass family.
    2. Representatives:
    • a. Lichens
      b. Sedges, rushes and grasses
      c. Willows (New World), heather (Old World).

    3. Some 700 species.
    4. Variety of survival strategies
    5. Defined by a distinct tree line

  D. Animals:

  • 1. Migratory birds, especially water birds.
    2. Predators: wolves (right, thanks to J. Colin), arctic fox, weasels, owls, etc.
    3. Large mammals: bear, caribou (New World) or rain deer (Old World), musk oxen, polar bears and Dall sheep.
    4. Small mammals: voles, lemmings
    5. Insects: Black flies, mosquitoes, gnats
    6. Still, low diversity and productivity

E. History:

• 1. Much (but not all) of the area dominated by last continental ice sheet ("Laurentide Ice Sheet"); effects ended about 4000 years ago.
  2. Vegetation moved northward forming "high" and "low" tundra.

F. Exploitation:

• 1. Habitat destruction due to exploitation of natural resources.
  2. This "frozen" or "polar desert" requires centuries to recover.
  3. Possible impact from global warming which is having a greater impact in the tundra than elsewhere.
  4. Threat of pollution.

Southern Taiga Forest or Boreal Forest - Michigan

• A. Location:
  • 1. Circumpolar in northern hemisphere.
    2. Alaska and Canada to northeastern and Great Lakes region of the United States - see this summary site.
    3. Area often characterized as "boreal forest", "northern coniferous forest" or even "Cold Climate Forest".
    4. Taiga subdivision divided into several ecozones: (a) taiga cordillera, (b) taiga plains, and (c) taiga shield.
    5. Boreal forest subdivision divided into several ecozones: (a) boreal cordillera, (b) boreal plains, and boreal shield.

  B. Features and environmental conditions:

  • 1. Forest dominated by densely arranged dark evergreen conifers; an effective "carbon sink".
    2. Little moisture (17-20 in or 40-50 cm) mostly as summer rains.
    3. Freezing temperature, extreme cold (-100° F are not uncommon). The temperature rarely exceeds 85° F in the summer. The growing season is 90 to 120 days per year. Snow is common.
    4. Shallow soils, wet, deep permafrost; nutrient poor.
    5. Fire and insect pests are an occasional factor.

  C. Vegetation:

  • 1. Northern edge defined by a timberline
    2. Trees: Examples include Pinus (pine), Abies (fir), Picea (spruce) and Larix (larch or tamarack). The latter is a deciduous conifer, meaning that the needles fall away each winter. Hardwoods include paper birch (Betula papyrifera) and quaking aspen (Populus tremuloides).
    3. Other plants: Shrubs include willows and members of the heath family (Ericaceae) but not Erica the true heath.
    4. Graminoids (mainly grasses), lichens and bryophytes (Sphagnum).
    5. Succession: Shallow ponds or lakes to peat bogs to graminoids to shrubs to trees. (See to the left)
    6. About 1800 species of vascular plants

  D. Animals:

  • 1. Large mammals: Elk, caribou, deer, bear (brown, grizzly).
    2. Predators: Wolves, bear, lynx, wolverine, fox.
    3. Birds: Migratory and some resident birds, especially song birds.
    4. Insects: black flies, midges, gnats, mosquitoes, etc.
    5. Soil organisms: protozoans, nematodes, fungi

  E. History:

  • 1. Most of the biome covered by repeated series of continental ice sheets, the most recent being the Wisconsin Ice Sheet which reached its height about 25,000 years ago, persisted until about 12,000 years ago, and declined over the period 10,000-7,000.
    2. Ancient Lake Agassiz existed before the Great Lakes and Lake Champlain were formed at end of Wisconsin event.
    3. Refugia (sing. refugium): areas where plants and animals escaped the effects of glaciation; land bridge across the Bering Straits between Siberia and Alaska, "islands" as in central Alaska and the "driftless" area of Wisconsin, and escape routes along the Pacific coast of Alaska.
    4. Nunataks: Isolated mountain tops or ridges that were unglaciated; resulted in many endemic and disjunct populations

  F. Exploitation:

  • 1. Hunting is leading to a loss of many species [a discussion of biodiversity in Canada], especially fur-bearing animals.
    2. Mineral and logging exploitation are resulting in the loss of habitat although current management of forest resources is reducing the impact, especially in Canada.
    3. Fire: mainly natural and part of the succession process.
    4. Lumbering: may be a threat in the near future.
    5. Productivity limited by cold and varies greatly throughout the region

Meadow succession in a taiga forest -- Michigan

Main Terrestrial Biome page

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Last revised: 17 Oct 1997 - Reveal