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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.
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.
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.
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.
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.
Global Distribution of Terrestrial Biomes
In response to: Moisture, Temperature, Light, Soil, and Topography