soil forming processes

Question 1

soil forming processes (4 general, 3 specific)

Answer 1

• additions
• losses
• translocation (-> E, B hzns)
• transformations
• Podzolization
• Gleization
• Laterization

Question 2

Podzolization (5)

Answer 2

found in: temperate climates w/ high precip., cool temps

associated w/ coarser soil & certain veg (Abies, heath/vacc.), which produce organic acids that chelate (bind Al & Fe)

1. ​organic acids are produced from decomposing litter (ex: by fungi)
2. soluble organic acids leach from O hzn into mineral soil
3. org. acids form complexes w/ Fe & Al
4. complexes leach from E -> B
5. precipitate out of solution in B, coating surfaces of particles

-> Bhs, Bs… Spodosol

Question 3

Gleization (4)

Answer 3

occurs in waterlogged or poorly drained soils
may occur only in lower soil

A
Bg - mottles of color
Cg - grey / orange

Fe+3 (red, oxidized) + e -> Fe+2 (grey, reduced)

oilrig

1. water saturates soil pores
2. organisms deplete water O2 while decomposing OM
3. once O2 depleted, organisms give electrons to Fe+3, reducing it to Fe+2
4. surface of aggregate turns grey, or eventually the whole soil

wet/dry cycles = mottled

always wet = all grey

Question 4

Laterization (3)

Answer 4

• occurs in soils w/ high precip & high temp (tropics), good drainage, stable landscape (>100k yrs), lots of Fe
• super orange due to in place oxide formation (Bo)
• high decomp rate = little O hzn = little org acids (compared to Podzolization)

1. OM decomposes fast, so little to no O hzn
2. high leaching removes Si, but Fe & Al oxides remain = red soil
3. Fe & Al oxides dominate soil & form in place = Bo

Question 5

4 sources of pedoturbation (mixing loss of hzns)

Answer 5

1. freeze/thaw
2. wind throw
3. worms
4. clay -> shrink/swell