Chapter 4

Question 1

Constraints for life on land

Answer 1

• desiccation (water evaporation)
• gravity
• temperature fluctuations

Question 2

Leaf Area Index(LAI)

Answer 2

Area of leaves per unit of ground area. Higher LAI=less light

Question 3

PAR

Answer 3

Photosynthetically active radiation.

• 400-700 nm
• most is filtered by canopy of trees

Question 4

Sun flecks

Answer 4

unaltered light on the forest floor. Approximately 70-80% of light that reaches the forest floor

Question 5

Chlorophyl

Answer 5

Green pigment in plants that absorbs light

Question 6

Importance of soil

Answer 6

• medium for plant growth
• controls where water ends up
• cycles nutrients
• biotic and abiotic interactions

Question 7

Regolith

Answer 7

Layer of broken rock over unweathered rock. The interface between air, water, rock and living organisms where soil formation begins.

Question 8

Modes of soil formation

Answer 8

1. mechanical/physical weathering
   - water, seeping, freezing, and cracking
   - wind-borne particles wearing away surfaces
   - growing roots
2. chemical weathering
   - water carrying chemicals (oxygen, or acid, etc.)

Question 9

Six factors affecting soil formation

Answer 9

1. Parent material-original material
2. Site history-volcanic, glacial, lake, etc.
3. Climate-affects rate of formation via biotic/abiotic factors
4. Biota-roots could potentially break up rock, reduce erosion, move up nutrients (promoting fungi and protists)
5. Topography-affects runoff and erosion
6. Time- well developed soil can take up to 2k-20k years to form. Causes concern when rate of formation is slower than the rate of erosion

Question 10

The colour of soil indicates….

Answer 10

• chemical content (organic matter, primarily humus, makes soil black)
• yellow-brown, or grey blotches indicates water saturation or poorly drained soil

Question 11

Soil texture affects….

Answer 11

• pore space and fertility
• movement of water and air
• penetration of roots