Ecology: Lecture 2Ecology: Lecture 2

Biomes as related to Biomes as related to Temperature and MoistureTemperature and Moisture

Global distribution of Global distribution of terrestrial biomesterrestrial biomes

What causes the poles to be colder What causes the poles to be colder than equatorial regions?than equatorial regions?

Key reason: Curvature of the earth and resultant angle of sun’s rays [Fig. 2.7a]

Which other factors mediate the Which other factors mediate the distribution of global distribution of global

temperature?temperature? Earth’s rotation air and ocean

currents that affect the distribution of heat energy

Earth’s tilt (angle of axis) Albedo

Movement of air massesMovement of air masses

If the earth had no rotation:

Movement of air massesMovement of air masses With rotation:

Ocean circulation Ocean circulation patterns and heat patterns and heat

distributiondistribution Example: Effect of the Gulf Stream on

temperatures (E. North America; W. Europe)

The angle of the earth’s axis is responsible for seasonal variations on the earth.

Fig. 50.12

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Position shifts between summer and winter (why?)

Albedo: Albedo: reflectance of reflectance of solar radiationsolar radiation

Snow and Ice: high albedo

(Photo: K. Haberman) Forested areas:

low albedo Photo: Natl. Park Svc.

Global patterns of precipitationGlobal patterns of precipitation

Global patterns of precipitationGlobal patterns of precipitation Warm air holds more moisture than cold air Warm air rises and cools, dropping moisture close to

where it was picked up, so that moist areas tend to remain moist, and dry areas tend to remain dry

Warm, dry air picks up additional moisture…

Altitude and Rain Altitude and Rain shadowsshadows

North vs. south facing North vs. south facing slopesslopes

North vs. south facing slopes (cont.)North vs. south facing slopes (cont.)

MicroclimateMicroclimate example: example: Effects of vegetation on Effects of vegetation on

temperature temperature

NutrientsNutrients Macronutrients

Definition? Examples: C, H, N, O, P, Ca, Mg, K, S, Na,

Cl Micronutrients

Definition? Examples: Fe, Mn, B, Co, Cu, Mo, Zn, I,

Se

Global distribution of Global distribution of productivity in the oceanproductivity in the ocean

UpwellingUpwelling

Focus on lightFocus on light Characteristics that vary with

climate/microclimate wavelength intensity duration directionality

Light energy as a Light energy as a function of latitude and function of latitude and

time of yeartime of year

PAR: Photosynthetically PAR: Photosynthetically active radiation (400-740 active radiation (400-740

nm)nm)

Attenuation of light Attenuation of light through waterthrough water

Attenuation of light Attenuation of light through vegetationthrough vegetation

Leaf area index

Attenuation of light Attenuation of light through vegetation through vegetation

(cont.)(cont.)

Other key factorsOther key factors Salinity

Example: Different estuarine species are tolerant to different conditions

Oxygen concentration Example 1: Surface waters vs.

sediments in an estuary pH Substrate (i.e. soil type, rocky

vs. muddy river bottom, etc…) Example: Distribution of

macroinvertebrates in streams.