Introduction to Ecosystems

What is an ecosystem?

• 
• 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:

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
• 

Deserts

• 
• 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
• 

Temperate Grasslands

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

Mediterranean

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

Deciduous Forest

• 
• 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

• 
• 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

• 
• 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.