Download Soil and Natural Vegetation

Soil
and Natural
Vegetation
SOIL
• SOIL: surface layer of the earth,
composed of mineral and
organic materials, air , and water
SOIL
• True soil consists of 4 main
parts:
–
–
–
–
1. Minerals,
2. Bacteria and Organic Material
3. Air
4. Moisture
• If one of these parts is
missing, the material cannot
be considered soil
COMPONENTS OF SOIL
Minerals
• The minerals in soil come from rock,
known as the parent material.
• Rock is broken down by weathering
into smaller particles of sand, silt,
and clay.
• Many minerals are nutrients needed
by plants for growth. e.g. calcium,
potassium, etc.
Bacteria & Organic
Materials
• When plants &
animals die, they
are decomposed by
bacteria in the soil.
• As bacteria break
down the organic
matter, nutrients are
released.
Bacteria & Organic
Materials
• Decaying organic materials form humus
which provides nutrients and moisture for
plants
• HUMUS: Dark, upper layer of soil made up
of partially decayed plant material
• The process of decay is nature’s way of
recycling nutrients
• Humus gives the soil its dark colour
Air
• Air is found in all soils
usually in between soil
particles
• Plants need air around
their roots
• Air spaces also created
by insects / worms and
small animals that
tunnel through the soil
Moisture (Water)
• Water dissolves nutrients in the soil and
is then taken up by plants through their
roots
• Helps weather rock and decay
organic materials
ANIMALS
• Not an essential component of true soil
but few soils exist w/o them (worms,
mice, insects, etc.)
• Helps distribute soil particles and
nutrients & provide pathways /
openings for water and air
• Add organic material to the soil after
they have died.
Soil Profile
• O/A - TOPSOIL -this top
layer contains humus. It is
rich in organic material. It is
dark brown/black in colour
• B-SUBSOIL- combines
minerals and organic layers
• C- PARENT MATERIAL mineral materials from which
soil is made. Usually
bedrock or glacial deposits
Soil Formation
Two processes contribute to soil
formation:
• LEACHING
• CALCIFICATION
Leaching
• Is a continual downward movement
of water through the soil
• As the water moves down, it
dissolves the chemical nutrients and
carries them away
• This downward movement removes
nutrients that plants need
• You can identify leached soil by its
poor, often thin, topsoil layer
• Leached soils can be developed into
excellent farmland by adding
fertilizers
Calcification
• Occurs in dryer climates
• As water in the topsoil evaporates, water from
below is drawn up to replace it - CAPILLARY
ACTION
• As the water reaches the surface, it
evaporates leaving behind the minerals that
were dissolved in it
• The result is a thick topsoil layer, rich in
minerals
• Calcium is the main mineral deposited near
the surface
• In very dry climates the amount of mineral
deposits can be poisonous to plants