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Chapter 6

Environmental Change Ch. 6.docx


Department
School of Environment
Course Code
ENV222H1
Professor
Simon Appolloni
Chapter
6

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Environmental Change
Chapter 6- Ecosystems in the Environment
- similar climactic conditions are repeated in different geographical areas and
result in similar assemblages of biological organisms, known as biomes
- Biomes are defined as having climactically and geographically similar
conditions that result in certain communities of plants, animals, and soil
organisms
- Unlike ecozones, biomes are not defined by genetic, taxonomic or historical
similarities
- Each biome has a characteristic assemblage of plants and animals that have
adapted and evolved to these climactic conditions
- Near the poles, temperature is generally the overriding climate factor
defining a biome, whereas in temperate and tropical regions, precipitation is
more significant than temperature
- Canada’s terrestrial land base has been classified into biomes using the
Canadian Committee on Ecological Land Classification System as developed
by Natural Resources Canada
Tundra
- Tundra occurs in the extreme northern latitudes where the snow melts
seasonally
- The southern hemisphere has no equivalent of the arctic tundra because it
has no land in the corresponding latitudes
- A similar ecosystem located in the higher elevations of mountains, above the
tree line is called alpine tundra
- Most tundra soils formed when glaciers began retreating after the last ice
age, about 17,000 years ago
- These soils are usually nutrient poor and have little detritus
- Although the tundra’s surface soil that’s during summer, beneath it lies a
layer of permafrost, permanently frozen ground that varies in depth and
thickness
- Tundra supports relatively few species that do occur there often exist in
great numbers
- Animals adapted to live year-round in the tundra include polar bears,
lemmings, voles, weasels, arctic foxes, snowshoe hares, ptarmigan, snowy
owls, and muskox
- Tundra recovers slowly from even small disturbances
- Oil and natural gas exploration and development and military use have
caused damage to tundra likely to persist for hundreds of years
Boreal Forest
- Just south of the tundra is the boreal forest, or northern coniferous forest,
which stretches across North America and Eurasia
- There is no biokme comparable to the boreal foest in the southern
hemisphere
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- Winters are extremely cold and severe, although not as harsh as those in the
tundra
- Boreal forest receives little precipitation and its soil is typically acidic and
mineral poor, with a thick surface layer of partly decomposed pine and
spruce needles
- Where permafrost occurs, it is found deep under the surface
- Conifers have many drought resistant adaptions, such as needle-like leaves
whose minimal surface area prevents water loss by evaporation
- Being evergreen, conifers resume photosynthesis as soon as warmer
temperatures return
- The animal life of the boreal forest consists of some larger species such as
caribou, wolves, brown and black bears and moose
- Currently, boreal forest is the world’s top source of industrial wood and
wood fibre
Temperate Rainforest
- A coniferous temperate rainforest, known as coast forest in the CCELC
system, occurs on the northwest coast of North America
- Annual precipitation is high
- The proximity of temperate rainforest to the coastline moderates its
temperature so that the seasonal fluctuation is narrow; winters are mils and
summers are cool
- Temperate rainforest has relatively nutrient-poor soil, though its organic
content may be high
- The dominant vegetation in the North American temperate rainforest is large
evergreen tress such as western hemlock, Douglas fir western red cedar
Temperate Deciduous Forest
- Hot summers and cold winters characterize the temperate deciduous forest
- Typically, the soil of a temperate deciduous forest consists of a topsoil rich in
oganic material and a deep clay-rich lower layer
- The trees of the temperate deciduous forest form a dense canopy that
overlies saplings and shrubs
- They originally conatin a variety of large mammals, such as puma, wolves
and bison, deer, and bears
- Logging and land clearing for farms, tree plantations and cities destroyed
much of the original temperate deciduous forest
Temperate Grassland
- Summers are hot, winters are cold and rainfall is often uncertain
- Average annual precipitation ranges from 25-75 cm
- Grassland soil has considerable organic material because the aboveground
portions of many grasses die off each winter and contribute to the organic
content of the soil
- Moist temperate grasslands have largely disappeared from the Canadian
prairies except in preserved locations in Manitoba
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