Chapters #4 and #5The Physical Environment

Chapters #4 and #5The Physical Environment

5.1 – Life on land Imposes Unique Constraints.5.2 – Plant Cover Influences the Vertical Distribution of Light.5.3 – Soil is the Foundation Upon Which All Terrestrial Life

Depends.5.4 – The Formation of Soil Begins With Weathering.

5.1 – Life on land Imposes Unique Constraints.

5.1 – Life on land Imposes Unique Constraints.

Terrestrial Organisms:- must maintain water balance

- water loss through respiration.- replacement or desiccation.

5.1 – Life on land Imposes Unique Constraints.

The upward force of buoyancy due to the

displacement of water helps aquatic organisms

overcome the constraints of gravity.

5.1 – Life on land Imposes Unique Constraints.

Air is less dense than water. This means a lower “drag” on an

organisms'’ movement, but increases gravitational

forces. As a result, terrestrial organisms

(both plant an animals) invest heavily in

structural components.

80% of mass in structure

5.1 – Life on land Imposes Unique Constraints.

Temperature variations on land are greater than in water. The high specific heat of water prevents wide fluctuations. On/around land, air temperatures vary widely and seasonally.

The timing and quantity of precipitation varies widely across the terrestrial landscape.

Thus, geographic variation in temperatures and moisture governs large-scale plant and animal distributions in terrestrial ecosystems.

Attenuation of light through water

5.2 – Plant Cover Influences Vertical

Distribution of Light.

The dominant factor influencing the vertical

gradient of light in terrestrial environments

is the absorption and reflection of solar

radiation by plants.

5.2 – Plant Cover Influences Vertical

Distribution of Light.

Much of the same effect is seen in forests and

grasslands.

PAR: Photosynthetically active radiation (400-740 nm)

PAR: Photosynthetically active radiation (400-740 nm)

Attenuation of light through Vegetation

• Leaf area index –The amount of light at any

depth in the canopy is a function of the number of

leaves above. Foliage density is expressed in terms of leaf area

index.

Attenuation of light through Vegetation

Attenuation of light through Vegetation

Light energy is a function of latitude and time of year

Seasonal Variation in PAR – A Yellow Poplar Forest

5.3 – Soil is the Foundation Upon Which All Terrestrial Life Depends

Soil – The “Living”

Medium and/or System for Plant

Growth.Weathering of Parent

Material via:

- Mechanical- Chemical

5.3 – Soil is the Foundation Upon Which All Terrestrial Life Depends

Biotic and Abiotic factors contribute to

Soil Formation

Parent Material is influenced via biotic

interaction, climate and topography.

Example: different soils can influence ion exchange and plant nutrient uptake.

World Soil Distribution

Global Distribution of Terrestrial Biomes

In response to: Moisture, Temperature, Light, Soil, and Topography

Changing Times. . .

www.barry.warmkessel.com/barry/YELLOWSTONE.

Changing Times. . .

www.barry.warmkessel.com/barry/YELLOWSTONE.