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5.3 Soil Degradation and Conservation - Coggle Diagram
5.3 Soil Degradation and Conservation
Soil Ecosystems change through succession.
Fertile soil contains a community of organisms that work to maintain functioning nutrient cycles and that are resistant to soil erosion
Pioneer stages: Bare rock , lichens, small annual plants, lichens, perennial herbs, grasses
Intermediate stages: Grasses, shrubs, shade-intolerant trees
Climax community: Shade-tolerant trees
Present environment: A -> A/B -> B -> C
Influence biotic factors range from organism or bacteria to humans
Bacteria fix atmospheric nitrogen converting into a usable form for plants roots
Mycorrhizal fungi on tree roots take up soil nutrients and pass them directly to the tree
Decomposers break down litter releasing nutrients into the soil
Soil organisms help to mix the soil improving its structure
animal burrows help to aerate the soil
animal faeces return nutrient to the soil
Indirect influences: Interception of precipitation by vegetation
REduction of precipitation via evapotranspiration
Soil degradation is caused by 1. Erosion by water and wind 2. Physical degradation 3. Chemical degradation 4. Biological degradation 5. Climate and land use change may accelerate the above factors
Factors influencing the erosion of soil by water and wind
Water erosion:
Soil erodibility
Rainfall intensity
Slope gradient
Vegetation
Wind Erosion
Soil erodibility
Soil surface and roughness
Climate
Unsheltered distance
vegetative cover
Reduced soil fertility may result in soil erosion, toxification, salinization and desertification
Wind erosion
Gullying
Sheet wash
Soil erosion
Salinization
Desertification
Human activities that can reduce soil fertility include deforestation, intensive grazing, urbanization and certain agricultural practices
Deforestation: Removal of some or all of a cover of trees.
The greater the proportion of tree removed, the less interception occurs, the more soil compaction by raindrop impact, increase soil erosion potential
Rate of erosion are highest in semi arid areas when there is discontinuous of vegetation cover and seasonal rainfall
Intensive grazing: The Grazing of natural pastures at stocking intensities above the livestock carrying capacity
Greater the intensity of grazing -> the more vegetation covers is removed 2. Large herds may destroy vegetation covers is removed 3, Grazers may compact the soil
Urbanization
Requires the removal of vegetation for construction and heavy machinery compacting the soil surface
Making soil impermeablem water is unable to infiltrate
Certain agricultural practicesL increase amount of salt in soil.
Evaporation: capillary action bring water to the surface, evaporated and leaving soluble salt behind
Paddy field as water evaporate, salinity increases
Ciasrak and estuarine: salt water intrusion
Commercial, industrialized food production systems generally tend to reduce soil fertility more than small scale subsistence farming methods
• Large amount of chemical and energy input is required in
commercial and industrialized food production systems.
• Usually alters the natural environment /deforestation,
deteriorates soil quality, and eliminates biodiversity →
Maximize the potential yield of crops.
• The use of heavy machine compact the soil→ more
impermeable → reduce O2
content.
• The use of fertilizer alter soil’s chemical composition +
increase nutrient runoff
• The use of pesticides / herbicides → increase amount of
dangerous toxins
Soil conservation measures include:
✓Soil conditioners (such as organic materials
Corrects the soil deficiencies in structure
and lime).
✓Wind reduction techniques (wind breaks,
shelterbelts).
✓Cultivation techniques (terracing, contour
ploughing, strip cultivation).
✓Avoiding the use of marginal lands.
