Soil and Natural VegetationPhysical Geography
1Do We Really Need Soil?Lets Dig Up the Facts!
Soil Contains the Minerals All Living Things Need!
We Use Soil to Grow Food!
Many Animals and Microscopic Creatures Live in the Soil!
Soil Helps Soak Up Rainwater So We Dont Have Flooding!
SoilSoil is made up of 4 main parts:MineralsOrganic and
Bacterial materialsMoistureAir
Think -MOMA MineralsEx. calcium, phosphorus, potassium,
etc..Comes from parent material (usually rock) or loose material
deposited from a glacierMinerals become part of the soil when rock
is broken down by weathering
Organic and Bacterial MaterialDead plants and animals are
decomposed by bacteria in soil, nutrients are released to form
humusHumus provides nutrients and moisture to plants and gives soil
its dark colour.MoistureWater dissolves nutrients in soil allowing
plants to take them up through their rootsWater is also needed in
the processes that weathers rock and decays organic materialAirAir
in soil is created by high humus levels (loose, decaying material
allows for many air pockets), worms, insects and small
animalsPlants need air around rootsTypical Soil Profile
Typical Soil ProfileHorizon OLeaf litter, organic
materialHorizon ATop SoilRich in organic materialsDark brown or
black in colourHorizon BSub SoilCombined mineral and organic
layerLighter brown in colourHorizon CParent MaterialMineral
materialsUsually 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 nutrientsLeached 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 waterAs water in the top soil evaporates, water from
below is drawn up to replace itAs water evaporates, it leaves
behind mineralsTopsoil is thick and rich in mineralsIf soil is very
dry, the amount of minerals left can create a layer that is
poisonous to plants
