Unit 5- Soil Resources

Question 1

Soil Profile:

Answer 1

• Collection of various layers of soil, from surface to bedrock
Each layer is known as a horizon- O,A,B,C, and R

Question 2

Leaching:

Answer 2

• Process through which minerals are carried downward through the developing soil profile
• Materials suspended or dissolved in liquid are transported through the subsurface
• Acts like a coffee filter- water infiltrates soil, dissolves substances, and carries them down
Some of this material is deposited in zones of accumulation

Question 3

Soluble Minerals:

Answer 3

• Minerals that are easily leached
• i.e. iron, aluminum, silicate minerals
• In some soils, minerals are leached so quickly that plants are deprived of nutrients
Minerals may be carried into ground water, affecting water quality

Question 4

O Horizon:

Answer 4

Peat deposits

Question 5

Litter:

Answer 5

• Surface deposits of leaves, branches, mosses, and animal waste
Form organic horizon in upland forests

Question 6

A Horizon:

Answer 6

• Uppermost mineral horizon
• Organic mineral components with organic matter and humus from above mixed in
• Often referred to as topsoil
• Rich in nutrients, vital for ecosystems and agriculture
Humus gives topsoil its loose texture and dark colour

Question 7

B Horizon:

Answer 7

• Subsoil
• Minerals and organic matter leached down from topsoil
• Form hard, mineral rich layers called hardpan, claypan, duripan, or caliche (depending on composition and structure)
Create problems for plants because they interfere with drainage and prevent plant roots from penetrating to lower, nutrient rich horizons

Question 8

C Horizion:

Answer 8

• Transition zone below B horizon
• Broken up parents material only slightly altered by processes of soil formation
Contains rock particles larger and less weathered than above layers

Question 9

R Horizon:

Answer 9

• Unaltered parent material

R (rock) horizon

Question 10

W Horizon:

Answer 10

Some soils have a layer of water

Question 11

Permafrost:

Answer 11

Some arctic soils contain a perennially frozen layer

Question 12

Soil Variation:

Answer 12

• Young soils then to be thin
• Not all horizons are present in all soils
Soils classified into various categories using properties such as colour, texture, and pH

Question 13

Soil Colour:

Answer 13

• Colour can indicate composition and fertility
• Black or dark brown soils usually rich in organic matter
Pale grey to white soils usually chalky, leaching, or are low in organic content

Question 14

Loam:

Answer 14

Soil with a relatively even mixture of clay, silt, and sand

Question 15

Regional Differences and Soil Productivity:

Answer 15

• Rainforest ecosystems have high primary productivity, but nutrients are trapped in plants, not in the soil
• Temperate grasslands (prairies) have much higher productivity in soil
• High volume of rain in rainforests leaches minerals and nutrients out of topsoil- those not captured by plants are taken down to the water table
High temperatures speed decomposition of leaf litter and uptake of nutrients by plants, so only small amounts of humus are present, and layer of topsoil remains thin

Question 16

Swidden Agriculture:

Answer 16

• In tropical rainforests, organic matter is in the plant biomass, when plants are cleared, the soil’s fertility is depleted
• Farmers cultivates a plot for a few years, clears it, and then moves onto a new plot, leaving the first one to grow back to forest
Works for low population densities, but soils are not given enough time to regenerate in today’s population

Question 17

Plant Fertility in Temperate Grasslands:

Answer 17

• Rainfall low enough to prevent leaching of nutrients
• Plants take up nutrients and return them to soil when they die
• Low temperatures slow rate of decomposition, organic matter mainly stored below ground
Topsoil in grasslands can be farmed repeatedly with minimal loss of fertility if properly kept

Question 18

Human Acceleration of Erosion:

Answer 18

• Over cultivating fields through poor planning or excessive ploughing, especially when land is left bare (no vegetative cover)
• Over grazing rangelands with more livestock than the land can support reduces vegetative cover
Clearing forested areas on steep slopes or with large clear cuts

Question 19

Mechanisms of Erosion:

Answer 19

• Several types of erosion can occur, including wind erosion and 4 principal kinds of water erosion
• Rill erosion has the most potential to move topsoil, followed by sheet erosion and splash erosion
• All types of water erosion, particularly gull erosion, are more likely to occur where slopes are steeper
• Steeper slopes, greater precipitation, and sparser vegetative cover leads to greater water erosion
• Vegetation breaks up wind, slows water, plant roots hold soil in place and take up water
Removing plant cover accelerates erosion

Question 20

Universal Soil Loss Equation (USLE):

Answer 20

• Tool for estimating erosion losses by water from cultivated fields to show how different soil and management factors influence soil erosion

Question 21

The Dust Bowl:

Answer 21

• Native prairie grasses in grasslands used to hold erosion prone soils in place
  
  • People moved to grasslands, cultivated wheat, ranchers grazed cattle, caused erosion by removing native grasses and breaking down soil structure
  • Drought, strong winds intensified these effects, creating dust storms, grasshopper infestations

Question 22

Erosion Control:

Answer 22

• Stabilize eroding banks along creeks and roadsides by planting plants to anchor soil
Plant plants in rows to protect open fields from wind

Question 23

Crop rotation

Answer 23

○ Alternating kind of crop grown in a particular field from season to season
○ Returns nutrients to the soil, breaks cycles of disease associated with continuous cropping, minimizes erosion that occurs from letting fields lie exposed
○ i.e. rotating between what and legumes- legumes have nitrogen fixing bacteria in roots, can revitalize soil
If an insect lays effs on one particular crop, planting a different crop will leave its offspring with nothing to eat

Question 24

Intercropping

Answer 24

○ Planting different types of crops in alternating band or other spatially mixed arrangements
○ Slows erosion by providing more ground cover than a single crop does
Reduces vulnerability to insect and disease, replenishes soil when a nitrogen fixing legume is one of the crops

Question 25

Agroforestry

Answer 25

○ Crops interplanted with trees
○ More biologically productive than farm systems in which food crops are grown alone
○ Trees draw nutrients and water from deep in the soil, cycling them into the shallower layers of soil
○ Trees contribute to organic matter in topsoil from fallen branches and leaves
Trees provide partial shade for crops

Question 26

Contour farming

Answer 26

○ Ploughing furrows sideways across a hill (perpendicular to its slope) prevents formation of rills and gullies
○ Furrows follow the natural contours of the land
Downhill side of each furrow acts as a small dam that slows runoff and catches soil before it is carried away

Question 27

Terracing

Answer 27

○ Most effective method for preventing erosion of extremely steep terrain
○ Level platforms with raised edges cut into steep hillsides to contain water from irrigation and precipitation
Transforms slopes into a series of steps, prevents losses of huge amounts of soil to water erosion

Question 28

Shelterbelts

Answer 28

○ Reduces wind erosion
○ Row of trees or tall shrubs planted along edges of fields to slow wind
Commonly used in the Prairies

Question 29

Alley cropping

Answer 29

§ Shelterbelts combined with intercropping
Fields planted in rows of mixed crops surrounded by or interspersed with rows of trees that provide fruit, wood, or protection from trees

Question 30

Reduced tillage

Answer 30

○ Also known as the no-till method
○ Tractor pulls a drill that cuts long, shallow furrows through the litter of dead weeds and crop residue and upper levels of A horizon
○ Seeds dropped into furrow and closes the furrow over the seeds
○ Increases organic matter while reducing erosion (ploughing and planting cycles makes soil more erosion prone), allows soil to build up, aerate, and restore

Question 31

Physical Indicators of Desertification

Answer 31

○ Decrease in soil depth
○ Decrease in organic material
○ Decrease in soil fertility
○ Soil crust formation
○ Decline in quality/quantity of groundwater
Decline in quality/quantity of surface water

Question 32

Biological Indicators of Desertification- Vegetation

Answer 32

§ Decrease in cover
§ Decrease in above ground biomass
§ Decrease in yield
§ Alteration of key species distribution and frequency
Failure of species to reproduce successfully

Question 33

Biological Indicators of Desertification- Animal

Answer 33

§ Alteration of key species distribution and frequency
§ Change in population of domestic animals
§ Change in herd composition
Decline in livestock production and yields

Question 34

Socio-economic Indicators of Desertification

Answer 34

○ Change in land/water use
○ Change in settlement pattern
○ Migration change 
○ Increased conflict
Marginalisation and increased poverty

Question 35

UN Indicators of Desertifcation

Answer 35

• Water availability
• Change in land use
• Proportion of population living above the relative poverty line
• Food consumption per capita
• Capacity of soil to sustain agro-pastoral use
• Degree of land degradation
• Plant and animal biodiversity
• Drought index
• Land cover status
• Carbon stocks above and below ground
Land under Sustainable Land Management (SLM)