soil processes

Question 1

what are the processes involved in soil formation

Answer 1

• weathering of the parent material
• decay and decomposition of dead organic matter (DOMS) into humus

Question 2

why is humus important

Answer 2

• it provides the soil with nutrients which are released when matter is broken down by soil organisms
• it helps absorb and retain moisture in soil
• it improves the structure of the soil and helps bind soil particles together

Question 3

leaching

Answer 3

• the downward transfer of soluble soil bases and the temporary acidification of top soil
• in climates where rainfall is greater than the amount of water evaporated or transpired from the surface, a downward movement of water will be dominant.
• snow melt can also have the same effect
• in this way the water will carry nutrients beyond the reach of plant roots and into the ground water system
• this can leave the top soil acidic (low pH) due to high concentration of hydrogen ions

Question 4

capillary action

Answer 4

• upward movement of water and nutrients into the upper soil which plant roots can access
• this happens when rainfall totals are lower than the potential evapotranspiration
• high temps and low rainfall cause the upward movement of bases, particularly calcium (eg in temperature grasslands), resulting in the deposition of calcium nodules in the AIC horizon

Question 5

the temperate (mid-latitude) grassland biome climate

Answer 5

• extremely cold winters (-10°C)
• extremely hot summers (over 20°C)
• low rainfall (400mm-800mm)
  The lack of rainfall and limited water availability means that the seasonal grasses dominate vegetation.
  Trees cannot survive here, except alongside rivers and streams. This is due to lack of rainfall, natural fires and grazing animals killing the young tree saplings.

Question 6

what type of humus is mollisols soil associated with

Answer 6

mull humus

Question 7

what helps to create a deep, dark, nutrient rich A-horizon?

Answer 7

grass vegetation decomposes to produce neutral or slightly alkaline soils. this is quickly mixed by earthworms and other animals

Question 8

what is the structure like of the A-horizon?

Answer 8

granular crumb structure

Question 9

is the soil fertile? why? (mollisol)

Answer 9

grass blades and roots die in autumn each year and decompose. this adds lots or organic matter to the soil