World Geography 3202 Ecosystems

1. Threats to Soil

2. Threats to Soil
Environmental or Natural Factors: Temperature
 Extremes - too hot or too cold!
 Affects humus accumulation (low temps.= slow the decay of
organic matter).
 Too cold for any vegetation to grow = nothing to die, no humus.
Ex. Tundra and Polar ice caps.
 Too hot = drought, with wind = dust storms or wind erosion. Ex.
deserts
 Too cold = frozen ground, slow growth or short growing season.
Again no humus! Ex. Tundra & Polar Ice Cap.

3. Threats to Soil
Environmental or Natural Factors: Precipitation
 Extremes = too wet or too dry!
 affects mineral content (rain causes minerals to be
eluviated or leached.)
 Washing away the soil or ground . (Erosion)…
nutrients (leaching)
 Too dry = less vegetation growth = less
accumulation of humus ex. Deserts
 Too wet = muddy, soaked soil = plants less able to
obtain nutrients

4. Human –
Threats
to
Soil
pg. 140-143
Poor Soil Management
• Overusing the land …planting the same crop ALL the time.
• Determine what land is BEST suited for and using it for that reason.
• Ex. Don’t build on agricultural land. (urban expansion!)
• Ex. Don’t grow grasses where land BEST suited for grapes.
• Ex. Using chemical fertilizers and pesticides.
• Ex. Leaving soil / land fallow. (NOT planting)

5. URBAN EXPANSION:
Q. Is this the BEST use of this land?
Q. What does this land seem MORE suitable for?
Q. What other OPTIONS do they have?
Threats
to
Soil
pg. 140-143

6. Threats to Soil - Desertification
• the spread of desert-like soil conditions in a semi-arid
environment.
• Turning productive soil into unproductive, dry, desert-like soil!
• Occurs in hotter, drier areas and is accelerated by
overgrazing, deforestation, leaving land fallow

7. Threats to Soil
• Erosion
• Flooding
• Overgrazing
• Deforestation

8. Reducing Soil Erosion Pg. 142
Strip cropping
 Alternating strips of open-growing crops and close-growing
crops.
 the close-growing crops act as a buffer or barrier to wind
erosion.
 As well, the close-growing plants and roots prevent or hamper
soil erosion (running water)

9. Reducing Soil Erosion Pg. 142 - Strip cropping

10. Reducing Soil Erosion
Cover cropping
• Planting close-
growing crop when
NOT planting a
harvest crop.
• Ground cover =
shade = prevents soil
from drying out,
• Close growing plants
prevent wind erosion
• Roots prevent water erosion.
• Soak up water preventing flooding
• Increasing humus content = plants get ploughed back into the

11. Reducing Soil Erosion - Cover cropping

12. Reducing Soil Erosion
Contour ploughing
• Respects the natural shape of the land.
•Crops planted perpendicular to slope of land and water run-off.
•Prevents soil erosion due to run-off.

13. Reducing Soil Erosion
Terracing
• Constructing steps
or shelves in the
sides of hills or
sloping land to
reduce water run-off
and retain moisture.

14. Three Types of Soil
 Podzol :
– soils which predominate the boreal forest and
tend to be somewhat acidic
 Chernozem :
– soils which tend to be the best for
agriculture.
– are found in grasslands which are semi-arid
resulting in less leeching and a mineral rich
soil.
 Latosol :
– soils which are very infertile due to the high
amount of leeching.
– found in tropical rain forests with high