BSC 314 Lecture Notes - Lecture 68: Allelopathy, Sclerophyll, Temperate Deciduous Forest
28 Jun 2018
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Terrestrial Biomes of the World
The study of the distribution of plants is the science of plant geography. The units of
vegetation the plant geographers study vary in size from the basic community, to
groups of communities and their environment— ecosystems—to assemblages of
ecosystems with distinctive vegetation and growth forms that extend over large
geographic areas— biomes. Although these three terms each delineate portions of
vegetation that occupy space, the terms imply no size per se. A plant community can be
the lichens and mosses growing on the bark of a single tree trunk, an acre woodlot, or
the plant communities of Yellowstone National Park. So, too, the size of ecosystems
varies, although in this case energy flow and nutrient cycling dynamics determine the
boundaries of the ecosystem; that is, more reactions occur within the system
than between systems. Biomes are the largest units and are identified on continental,
hemispheric, or worldwide scale. They are composed of similar growth forms and
occur in broadly similar environments. The following paragraphs describe some
commonly recognized terrestrial biomes.
Arctic tundraoccurs north of the tree line and principally north of the Arctic Circle in an
area of low precipitation and little snow with cold average temperatures. Vegetation
consists of small perennial herbs, low shrubs, creeping willows, and a variety of
grasses, sedges, mosses and lichens.
Taiga is the Russian name for the coniferous forest that forms a wide belt between the
tundra of the north and the temperate deciduous forest to the south. It is composed
primarily of species of pine, spruce, and fir with an understory of ericaceous shrubs
(heaths), mosses, and lichens. Over 65 percent is underlain by permafrost and thick
peat deposits. Lakes and ponds are common and soils are poor.
Temperate deciduous forest is a mixture of broad leaved deciduous trees (such as ‐
beech, maples, and oaks) together with species of perennial herbs. Seasons are
pronounced with precipitation distributed evenly throughout the year. In North America
this forest extends from the Atlantic coast westward to about 100° longitude.
Temperate moist evergreen forest, sometimes called “temperate rainforest,” occurs in
areas of heavy precipitation both north and south of the equator. In North America it is
the forest of the northwestern Pacific Coast. Western hemlock, white cedar, coast
redwood, spruce, and other trees attain large size with mosses and lichens festooning
their branches and the whole forming a luxuriant, dense forest.
Temperate grasslands are the typical vegetation of the interior of continents where
they cover thousands of acres. Although grasses are the dominant life form, trees occur
along streams in riparian woodlands. Most of the highly fertile grasslands have been
plowed and cropped and a majority of the remaining grasslands are managed as
rangeland.
Warm deserts have hot summer temperatures with great diurnal temperature
variations. Precipitation is slight and irregular. Shrubs, succulents, and annuals are
common life forms in deserts worldwide. Productivity is low and limited by lack of
moisture. Some deserts may have no rainfall for 10 to 15 years and plants survive on
dew.
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Document Summary
The study of the distribution of plants is the science of plant geography. The units of vegetation the plant geographers study vary in size from the basic community, to groups of communities and their environment ecosystems to assemblages of ecosystems with distinctive vegetation and growth forms that extend over large geographic areas biomes. Although these three terms each delineate portions of vegetation that occupy space, the terms imply no size per se. A plant community can be the lichens and mosses growing on the bark of a single tree trunk, an acre woodlot, or the plant communities of yellowstone national park. So, too, the size of ecosystems varies, although in this case energy flow and nutrient cycling dynamics determine the boundaries of the ecosystem; that is, more reactions occur within the system than between systems. Biomes are the largest units and are identified on continental, hemispheric, or worldwide scale.
