Climate and Biogeography
Climate has a direct impact on the biogeographic distribution of the natural vegetation in a region. In fact, the two are often inseparable. The major factors of climate that affect vegetation patterns are humidity (precipitation) and temperature. High humidity and high temperature are associated with lush, green vegetation, such as that found in the Southeastern US. High temperature and low humidity are associated with arid, desert vegetation, such as is found in the southwestern US. Humidity becomes less important as temperatures decrease. The lowest temperature regions are associated with spruce coniferous trees (found in most of Canada) and tundra (a treeless type of grass and moss found in the northern extremes of the continent). Between these three extremes (1 high temperature and humidity, 2 high temperature and low humidity, and 3 low temperature), is a mixture of evergreen trees, deciduous trees (those that lose their leaves in winter), and grasslands.
Community and Ecosystem Dynamics* - This website does a great job in describing the Earth's major biological communities, including:
· Terrestrial Biomes: tundra, grassland, desert, taiga, temperate forest & tropical forest
· Aquatic Biomes: marine & freshwater
Vegetation Climagraphs (diagrams)
Vegetation Triangle (diagram)
North America's Climate Regions (Map)
- Examples of Major Vegetation Types in the US
Vegetation and Human Settlement
The discussion and diagrams above focus on "natural vegetation" patterns. Human settlement in North America has significantly modified these natural vegetation patterns. Native Americans may have been responsible for changing the natural woodland areas of the western Midwest region into grasslands through the use of fire in the hunting of big game at the end of the last period of ice coverage about 10,000 years ago. Europeans cut down almost all of the virgin forests of the eastern US. All we see today are secondary growth that is very different from the original vegetation. In the West, the suppression of forest fires has resulted in forests that are far more dense (and dangerous) than the natural patterns. Humans have also turned biologically diverse habitats into monocultural agricultural and forestry farms. Exotic plants and animals, introduced through human migration and trade, have threatened indigenous varieties in many parts of the US -- and have caused some to become extinct. While long term climate and vegetation change is a normal process, such changes have been greatly accelerated by human activity since the beginning of the industrial revolution (mid-1800s). This situation has made climate change a major research area for climatologists and biogeographers.
Date: 2015-02-16; view: 3534