Introduction to Ecosystems

What is an ecosystem?

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Ecosystems are geographic regions that hold specific environments and inhabitants.   An ecosystem is made up of plants, animals, and their surrounding physical environment.   Ecosystems are made up of biotic (living) and abiotic (non-living) parts that have important interrelationships.

Global Distribution of Ecosystems:

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Tropical Rainforests

Found in tropical regions   High temperatures and rainfall    Four layers of vegetation: emergents, canopy, under canopy, and forest floor   High biodiversity   Evergreen forest

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Deserts

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Found near the Tropics of Cancer and Capricorn   High temperatures and very little rainfall   Sand or coarse soils    Low biodiversity   Small shrubs and cacti

Tropical Grasslands

Found in tropical regions   High temperatures, rainfall for 6-8 months and occasional drought    Tall grasses during wet season   Few trees

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Temperate Grasslands

Very few trees   Also known as Prairies   Purple needlegrass and Buffalo grass

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Mediterranean

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30-40 degrees North of the equator   Drought-resistant small trees   Only found on the west coast of continents

Deciduous Forest

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Grow at higher altitudes   High rainfall   Trees lose their leaves in winter to reduce transpiration   Vegetation in 4 layers: canopy, sub-canopy, herb, and ground   Dominant species is Oak

Coniferous Forest

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Found at 60 degrees North of the equator   Extremely cold winter temperatures   Trees have thick bark to protect them from the cold   Needle leaves reduce transpiration   Shallow root systems because of shallow soil

Tundra

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Areas within the Arctic circle   Extremely cold temperatures   Only short grasses can survive   Permafrost   Very poor surface drainage

Factors that Control Ecosystems:

Climate decides the temperatures and rainfall for ecosystems and is the most important factor in the distribution and characteristics of ecosystems.   Latitude influences the amount of sunlight a region receives.   Altitude influences vegetation and temperature. As altitude gets higher, temperatures drop, soils become thinner, and there is less organic matter.   Ocean currents can affect surface temperatures and rainfall. Warm ocean currents bring warmer temperatures and cold ocean currents can sometimes bring arid conditions.

Ecosystem Balance:

Ecosystems are extremely intricate and interdependant; a small change in an ecosystem can affect the entire system. When an ecosystem is balanced it is in equilibrium.   Example: When grey wolves were reintroduced into Yellowstone National Park, elk populations dropped by 50%. This meant that grasslands could recover and more trees started to grow. This stabilised river banks and lead to more woody debris in the rivers creating pools. This increased the trout population. More available food increased the grizzly bear population.