Soil

Question 1

Brown forest properties

Answer 1

1. Thick leaf litter layer due to heavy leaf fall in autumn.
2. Milder temps encourages a greater decomposition leading to more alkaline or mull humus.
3. No clear boundary as milder temps encourages soil organisms e.g. worms to mix debris to a greater depth.
4. Deep tree roots take up bases/minerals which leaf fall returns to soil.
5. Some leaching of Al and Fe sesquioxides ours as precipitation exceeds evapotranspiration but is limited so there is an overall brown colour.
6. Weathered parent material by biological weathering from tree roots.

Question 2

Tundra Gley properties

Answer 2

1. Small shrubs
2. Subsoil is permanently frozen (permafrost) due to low temps.
3. Topsoil becomes waterlogged as drainage is impeded. It lacks oxygen thus Anaerobic.
4. Cold temps and waterlogging means limited bacterial action. Humus formation is slow.
   Humus is black, thin, acidic.
5. Micro-organisms extract 02 from the iron compound in the soil. Colour changes from brown orange to grey/blue.

Question 3

Podzol properties

Answer 3

1. Found in areas of coniferous forest/Taiga.
   2, Thin, raw, acid humus known as MOR. Cold/cool winters so decay is slow.
2. Shallow roots do not take up bases so trees contribute to acidic litter layer and acidic humus.
3. A-horison: mineral and organic layer.
4. E-Horizon: eluviated or leached layer, ash-grey in colour. Rainwater and meltwater cause downward perculation. Water becomes more acidic as it passes through needles and humus. Leaches the soluble basses - clays, iron, alluminium sesquioxides. This is known as podzolisation.
5. B-Horizon - Zone of illuviation. Leached minerals are redepositied. Iron redeposited first and may form a hard pan which can impede drainage. AL deposited next followed by clays lower down the horizon. (Reddish brown colour)
6. C-horizon or parent material. Slow to weather due to cold climate.

Question 4

Podzol formation

Answer 4

Vegetation is coniferous forests with needles and pine cones, that produces acidic mor humus. Low temperatures lead to slow decomposition. Limited soil biota leads to well defined horizons. High precipitation causes leaching which is the downward movement minerals (e.g. iron oxides), this leads to formation of an iron pan in the B horizon. This iron pan may impede drainage causing water logging.
Eluviation leaves an ash grey A horizon because the minerals have been leached out – this is podzolisation. C horizon is parent material, generally weathered rock.

Question 5

Brown earth formation

Answer 5

Vegetation is deciduous forest that provides deep leaf litter, this decomposes rapidly in mild climate resulting in a dark mildly acidic mull humus. Trees have long roots which
penetrate deep into the soil and absorb nutrients from lower layers. Biota are active and mix the soil so horizons are poorly defined. Precipitation slightly exceeds evaporation, giving downward leaching of minerals. This means an iron pan may form, which may impeding drainage.
Brown earth soils tend to be found on gentler slopes which allows for good drainage.
Parent material in C horizon is weathered rock.

Question 6

Gley soils formation

Answer 6

Gely soils have little vegetation (small shrubs) - mor acidic humus eventually forms. Low temperatures lead to a slow rate of decomposition of organic matter creating a thin dark humus. Plant roots do not penetrate deeply so limited recycling of minerals back to the vegetation.
Gleys tend to be waterlogged as drainage is prevented by the permafrost in the B Horizon. Anaerobic conditions cause the soil to turn a blue grey colour, this also means few organisms can live in the soil but horizons may become mixed by freeze-thaw weathering. Impermeable clay in the C horizon also impedes drainage and causes waterlogging.