Topic 4: Terrestrial Environment

Question 1

What are the 3 big challenges that come with being on land?

Answer 1

1. Water balance and desiccation.
2. Gravitational forces.
3. Variability of conditions especially in temperature and moisture.

Question 2

The amount of light at any depth in the canopy is affected by what?

Answer 2

The amount of light at any depth in the canopy is affected by the amount of leafy material above it.

Question 3

How can plants sense shade?

Answer 3

Shade sensing via phytochrome.

Question 4

What is LAI?

Answer 4

Leaf area index (LAI) s the measure often used to quantify the impact of leaf quantity on available light.

Question 5

Why is there an increase in reflection in grasslands?

Answer 5

Because they are trying to minimize water loss because they environment is dry.

Question 6

Why is there an increase in absorption in forests?

Answer 6

This is because as the light is absorbed in the plants it heats up which causes water loss. Because plants in forests are in a wet area they can ‘survive’ with loosing the water because there is so much of it.

Question 7

What can influence a plants ability to capture light?

Answer 7

Leaf orientation

Question 8

What is soil?

Answer 8

A natural product formed by the weathering of rocks and the actions of living organisms.

Question 9

What are the six interdependent facts that affect soil formation and its properties?

Answer 9

Parent material
Living organisms
Site history
Climate
Topography
Time

Question 10

Soil formation starts with what? Give examples.

Answer 10

Weathering parent material.

• Mechanical weathering
  
  • wind, water, temp, peeling and flaking away at rocks.
• Chemical weathering
  
  • Interactions with water, oxygen and acids modify minerals and rocks..
  • microorganisms, plant roots and organic compounds.

Question 11

How do biological factors help with soil formation?

Answer 11

Play a role in enhancing rate of chemical weathering.
Stabilizing the surface of material (bind t/o to stop it from easily eroding away).

Decaying plants and animals add organic material and release of nutrients into the soil.

Question 12

What are humic substances? What is the importance of humic substances in soil?

Answer 12

Humic substances are components of organic material. They are the end products of slow chemical breakdown. Humic substances accumulate in soil b/c they are resistant to further degradation.

Humic subtonics are highly -ve charged so they hold nutrients well in soil.

Soil is brown/black in colour when there is ⬆️amounts of humic substances.

Question 13

Why is site history important for soil formation? Soil development in Mb is influenced by what?

Answer 13

It influences the parent material of soil. Soil in MB is influenced by glaciation.

Question 14

Compare these 3 properties with regards to Grasslands and Savannah.

Organic matter
Parent material weathering
Development

Answer 14

Organic material:
- prairie: net accumulation, breakdown is slow
- savannah: organic material will break down faster than it can accumulate.

Parent material weathering:
- prairie: slow mechanical and chemical weathering.
- savannah: much more rapid breakdown

Development:
- prairie: thick soil. not much downward movement. slow controlled release of nutrients. nutrient holding capacity is ⬆️. Hold on to the nutrients.
- savannah: thin soils, a lot leeches out.

Question 15

What does black colour of soil indicate? What about white/grey? What about red?

Answer 15

Black soil indicates organic matter accumulation (humic substance accumulation).

Grey/white indicates that there is a leeching of nutrients in the soil.

Red indicates that there is a big accumulation of iron (lots of chemical weathering).

Question 16

What does the different soil pore sizes mean?

Answer 16

Large pores cause rapid water infiltration, percolation and drainage but have low water holding capacity.

Small pores cause slow water infiltration, percolation and drainage, but the soil does have high holding capacity.

Question 17

There are different horizons of soil. Describe what the O horizon is?

Answer 17

O horizon is the organic layer, it is made up of debris, in various stages of decomposition

Question 18

There are different horizons of soil. Describe what the A horizon is?

Answer 18

A horizon is often called the topsoil, and it is composed of both mineral and organic materials.

Question 19

There are different horizons of soil. Describe what the B horizon is?

Answer 19

B Horizon is often called the subsoil and contains less organic and more mineral components relative to the A layer.

Question 20

There are different horizons of soil. Describe what the C horizon is?

Answer 20

C horizon is a layer of unconsolidated material and is in general made of the material from which the soil develops (much more like the parent material. gone through the least amount of changes).