Transcript What is Soil?

What is Soil?
“a living, dynamic system with
organic and inorganic
components. Soil is a product of
its environment and parent
material”.
components
By volume:
– 45% mineral
– 5% organic material
– 50% space (air/water)
By mass?
–
–
–
–
0% air
18% water
80% mineral
2% organic material
1. The mineral component
• inorganic
• “mineral”: definition?
– Primary: original
components of earth
crust
– Secondary: new
minerals made by
weathering of earth’s
crust
• divided by particle
size:
– Sand, silt, clay
• mineral make-up due to:
a. Parent Material
b. How resistant minerals are
c. Climate
d. “Age”
a. parent material
material on and in which soil develops
Examples of soil developing IN rather than ON parent
material: 1. Apostle Islands
2. Boundary Waters
• 11 different parent materials …..
Regolith/bedrock:
weathered rock
Alluvium:
deposits on a flood plain from a river
Marine deposits:
shell, reef and other “bits” formerly at bottom of
ocean that have been uplifted
Lacustrine deposits:
clay deposits originally laid down at the bottom
of a lake; lake is no longer there
Example: glacial lakes in MN
Till:
unconsolidated material deposited by glacial ice
Outwash:
unconsolidated, sorted material deposited by
meltwater from a glacier
Organic sediments: peat
Volcanic ash
Loess:
deep deposits of silt that have been deposited
by wind
Sand:
beach sand, dune sand
Colluvium;
material that moved downslope, as in a
landslide
• mineral make-up due to:
a. Parent Material
b. How resistant minerals are
c. Climate
d. Age
b. resistance of minerals
• Soluble minerals are readily
LEACHED from soil profile
(Ca,Mg,Na)
• Certain minerals tend to accumulate
in soil
– (oxides of Fe, Al, Si)
• mineral make-up due to:
a. Parent Material
b. How resistant minerals are
c. Climate
d. Age
c. Climate
• Amount of leaching
• Rate of weathering
• mineral make-up due to:
a. Parent Material
b. How resistant minerals are
c. Climate
d. Age
d. Age
• Parent material is (usually) less
influential in “older” (more highly
developed) soil
2. Organic Component
• Living (primarily
decomposers)
• Non-living (dead
and all in-between
stages of
decomposition)
…about decomposers:
• Nutrient recycling
• Respiration
decomposer activity depends
on:
climate
soil moisture conditions
Micro-environmental factors (relief,
drainage)
decomposers and climate:
1) climate
type)
vegetation, litter (amount,
2) rate of decomposition
hot,wet >> cold, dry
soil moisture conditions
• Hot, wet preference of decomposers
micro-environmental factors
(relief, drainage)
• Slope aspect affects temperature
• Drainage affects anaerobic/aerobic
decomposition
3. The Space component
• Soil pores
– filled with air
and/or water
A. soil air
O2
CO2 N2
(per cents by volume)
Above-ground atm.
20.97
Soil (grassland) atm. 18.4
H 2O vapor
(rh)
0.03
79.0
<100%
1.6
79.2
100 %
B. soil water
• Functions?
• Polar molecule