SOIL AND NATURAL VEGETATIONPhysical Geography

Soil

Soil is made up of 4 main parts:MineralsOrganic and Bacterial materials

MoistureAir

Think -MOMA

Minerals

Comes from parent material (usually rock) or loose material deposited from a glacier

Minerals become part of the soil when rock is broken down by weathering

Organic and Bacterial Material Dead plants and animals are

decomposed by bacteria in soil, nutrients are released to form humus

Humus provides nutrients and moisture to plants and gives soil its dark colour.

Moisture

Water dissolves nutrients in soil allowing plants to take them up through their roots

Water is also needed in the processes that weather rock and decay organic material

Air

Air in soil is created by high humus levels (loose, decaying material allows for many air pockets), worms, insects and small animals

Plants need air around roots

Typical Soil Profile

Typical Soil Profile

Horizon O Leaf litter, organic material (grass)

Horizon A Top Soil

Rich in organic materials Dark brown or black in colour

Horizon B Sub Soil

Combined mineral and organic layer Lighter brown in colour

Horizon C Parent Material

Mineral materials Usually bedrock or glacier deposits

What happens if the soil is too wet? Leaching- the excess water dissolves

nutrients and carries them away (downward), making it difficult for plant roots to reach nutrients Leached soil has poor, usually thin topsoil

layer

Much of Canada is covered with Wet-Climate soil

What if the soil is too dry?

Calcification-there is an upward movement of water As water in the top soil evaporates, water

from below is drawn up to replace it As water evaporates, it leaves behind

minerals Topsoil is thick and rich in minerals If soil is very dry, the amount of

minerals left can create a layer that is poisonous to plants

Natural Vegetation Regions

Draw a cross section of a typical soil sample in your notes (copy from page 147- fig 13-2)

Color a map showing the Soil Regions of Canada(figure 13-1, page 146)