Dr. Ray L. Winstead
Professor of Biology, Indiana University of Pennsylvania

Biomes


Biomes are large land areas consisting of similar ecosystems.  Regional climates and regional physical environments interact with the living communities to produce these large areas of similar ecosystems. 

For example, large areas of the earth are covered with grasslands.  Smaller, basically self-contained ecosystems of different types of grasses and associated animals are found in local areas and when considered together form the grassland biome worldwide.  Each biome has a distinct vegetation structure related to the prevailing climate and physical environment.  Basically, these biomes are oriented along the earth's latitudes and tend to be shifted by ocean currents northward or southward along the continental coasts.  For example, the warm waters of the Gulf Stream give England, which has almost the same high latitude as southern Alaska, a climate and vegetation similar to the Carolinas.  Other factors such as mountain ranges, large bodies of water, and prevailing wind direction also introduce climatic variations and influence the pattern of regional vegetation. 

Types of Biomes 

1. Tundra
  Located in Northern latitudes of the Arctic Circle.
  A fragile environment characterized by relatively short vegetation composed of only a few species
        (i.e., low diversity), e.g., some grasses, mosses, lichens, dwarf trees.
  Birds and insects are abundant in summer.
  Except for the summer, very cold area for much of the year with the ground moisture frozen as permafrost.
        
Free, non-frozen water is scarce - a limiting factor.
  No corresponding biome occurs in the southern regions of the earth, because the southern oceans occupy
        the corresponding latitudes.
  Note that on some high mountains around the world there is an alpine tundra where the prevailing climate
        is similar to that of the arctic, even though the mountains may be much farther south.
  Very low productivity.
 

2. Taiga = Coniferous Forest
  Northern border is tundra and southern border is deciduous forest and prairie, e.g., Canada.
  The dominant vegetation is not dormant in the winter, i.e., the trees are the species that do not lose
        their leaves in the winter, that have needle-shaped leaves (e.g., spruce), that have cones rather than
        flowers.
  The climate consists of long, dark, cold winters and short, warm summers.
  The productivity is higher than the tundra but lower than the deciduous forest.
 

3. Temperate Deciduous Forest
  Historically located in eastern North America, and western Europe, however the natural deciduous
        forest has been reduced to small remnants (e.g., Joyce Kilmer Memorial Forest in North Carolina)
        because of Human development.  Present-day forests are just "brush heaps" in comparison to the
        historical forests. 
  Climate consists of relatively moderate temperatures (both in summer and winter) and relatively
        moderate rainfall (30 inches to 60 inches per year).
  Dominant vegetation consists of deciduous hardwoods (trees that become dormant in the winter and
        lose their leaves)
  Productivity is moderately high.
 

4. Grassland
  Includes the prairies of North America, the steppes of Eurasia, the pampas of South America, the veld
        of Africa.  The area is usually flat or gently rolling hills.  Natural grassland areas are extensively and
        intensively used for Human agriculture - only a very few natural remnants are left, e.g. along old railroad
         rights-of-way.
  Vegetation consists of different types of grasses.
  Climate consists of cool to cold winters and hot and dry summers.  Rainfall is between 10 inches and 30
        inches per year.
  Productivity is lower than the deciduous forest.
 

5. Savanna
  A savanna is basically a grassland with widely scattered trees.
  Savannas are found in Africa, South America, and Australia.
  The climate consists of moderate rainfall (30 - 60 inches of rain per year).  The rainfall is about the
        same as for the temperate deciduous forest, however the rainfall in a savanna is highly seasonal with
        long dry periods each year. 

6. Desert
  The defining characteristic is the climate with very little water - rainfall less than 10 inches per year.
  Temperatures vary considerably in different deserts.  Some deserts are very hot, while others are very
        cold.
  Productivity is very low with sparse plant growth.  Brief spurts of growth and reproduction occur after
        a rare rain.

           7. Tropical Rainforest = Jungle
  The climate consists of high temperatures and very high rainfall (about 400 inches per year)
  Productivity is very high.
  Diversity is very high.
  Tropical rainforests cover only about 2% of the earth's land surface, but they are home to about half
         of all the earth's species.
  The soil is very poor, since the organic material in the tropical ecosystems is mainly in the plants and
        recycled rapidly.  Less than one-fourth of the organic material in an ecosystem is in the soil.  If you clear
        the land and plant crops, you get very poor production.  In contrast, in temperate regions, such as in the
        USA, over one-half of the organic material in an ecosystem is in the soil.
.

           8. Oceanic "Biome"
  The Oceans consist of salty water and makeup about two-thirds of the earth's surface.
  In general, overall, the ocean is not very productive compared to other biomes.  The reason is there are
        very small amounts of nutrients out in the ocean.  People have a misconception of this, since the edges
        of the ocean are very productive.
  The "Immeasurable riches" of the sea is a gigantic myth, from the perspective of food production.  Just
        as much of the land area is not suited for agriculture, about 90% of the ocean is essentially a
        "biological desert."  The upper layer of the ocean, where there is enough light for photosynthesis,
        lacks the nutrients necessary for high productivity.
  The edges of the ocean are extremely productive.  Marsh estuaries have many nutrients available. 
        Half of all fish production in the ocean is dependent upon the marshes around the edge as a nursery
        ground for the young.
  Humans are busily destroying the most productive part of the ocean by filling in and polluting the
        marshes around the ocean edges.  Furthermore, modern fishing fleets are completely wiping out
        historically productive fishing grounds with no thought to the future.
  Food production from the ocean will, indeed, be an important part of food resources for Humans,
        but primarily for communities that live near the ocean edges. 



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Dr. Ray L. Winstead
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