| Dept of Biology, Lewis and Clark College | Dr Kenneth Clifton
|
|
Biology
141 Lecture Outline
|
Defining the biological environment: biomes as biological organizing units
The relationship between climate and biomes generates spatial pattern.
Combinations of rainfall and temperature determine vegetation types
Highest productivity, plant height, and plant density in areas with warm temperature and high precipitation: tree-dominated biomes.
Lowest productivity, height, and density in areas with either cold temperatures, low precipitation, or both: deserts, tundra... sagebrush/chaparral
In between: grasslands, savannah, steppe.
Talk about Primary Productivity: gC/m2/yr
In turn, the organisms that exploit the products of these vegetative groups show pattern
Seasonality varies dramatically across biomes, so there is also temporal pattern.
Technically, the term "biome" is generally reserved for terrestrial ecosystems... What about marine environments?
Underwater, depth and the penetration of sunlight plays a more important role than temperature (and, obviously, rainfall).
Tropical seas are warm and clear and nutrient poor.
"Plant" communities are protected from too much sun either by morphology or location
Low nutrient levels highlight the importance of photosynthesis for carbon production.
Temperate seas are cool, turbid, with higher nutrient levels
Kelp "forests" dominate temperate shorelines
Regular (seasonal) disturbance also plays a role in determining the biological community
Polar seas are frigid and seasonally clear, with very high nutrients but cyclic productivity
Most photosynthesis is done by phytoplankton
Salinities can be very high
General latitudinal patterns emerge:
Tropical regions are relatively stable
moderate levels of productivity are not limited by sunlight
Nutrient availability is important.
these regions support extremely high biodiversity
Temperate regions are intermediate in many ways:
Less stable in terms of temperature, rainfall, disturbance (waves, fire, etc)
Productivity can be high but biodiversity is lower than in the tropics.
Polar regions are extreme habitats
Very low temperatures, little liquid water (on land) and high salinities (in the oceans).
Productivity varies from almost nothing to high levels, depending on season.
Biodiversity is often low (with some organisms in super abundance during periods of high productivity.
