Chapters #4 and #5
The Physical Environment
Chapters #4 and #5
The 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.