Biosphere

Question 1

• Describe and explain the formation of a podzol soil.

Answer 1

• A podzol soil is formed as a result of the following factors:
  ➞ parent material
  ➞ climate
  ➞ relief
  ➞ drainage
  ➞ vegetation
  ➞ and organisms

1. Firstly, the podzol soil is quite a shallow soil.
   ➞ This is due to the limited leaf litter of pine needles and cones, and the parent material is not well weathered, often resulting in more acidic soils.
   ↳ The parent rock is acidic (e.g. granite or schist), resulting in a reddish brown layer in the B horizon.
2. Secondly, podzols are often found in upland areas where the climate is wet and cold.
   ➞ This results in low levels of soil biota, meaning the horizons are not mixed and are clearly defined.
   ↳ Also, high precipitation and snow melt lead to leaching of nutrients downwards through the soil (podzolisation).
   ➜ This leaves the A horizon a pale grey colour due to the absence of nutrients.
3. Also, podzols are poorly drained and waterlogged which denies the presence of oragnisms
   ➞ and creates a layer of hard iron pan which is impermeable.
4. Lastly, the vegetation in the area plays an important role in soil development.
   ➞ Confierous trees are present, which results in decaying needles and cones, causing a thin acid mor humus.

Question 2

• Describe and explain the formation of a brown earth soil.

Answer 2

• A brown earth soil is formed as a result of the following factors:
  ➞ parent material
  ➞ climate
  ➞ relief
  ➞ drainage
  ➞ vegetation
  ➞ and organisms

1. Firstly, the natural vegetation is deciduous trees.
   ➞ This is important in the soil formation as the vegetation provides deep leaf litter, which is broken down rapidly in mild/warm climate.
   ↳ These trees have roots which penetrate deep into the soil, ensuring the recycling of minerals back into the vegetation.
2. Secondly, brown earth soils are found in areas where precipitation slightly exceeds evaporation.
   ➞ This results in downward leaching of the most soluble minerals and the possibility of an iron pan forming, impeding drainage.
   ↳ Also, as the climate is warm/mild, soil biota is present.
   ➜ This results in the mixing of soil, aerating it and preventing the formation of distinct layers.
   (Soil biota also breaks down leaf litter, producing mildly acidic mull humus).
3. Also, the parent rock determines the rate of weathering,
   ➞ with hard rocks, such as schist, taking longer to weather, producing thinner soils.
   ↳ Softer rocks, such as shale, weather more quickly.
4. Lastly, brown earths tend to be found on gentler slopes,
   ➞ resulting in lower rates of erosion, so thicker soils form.

Question 3

• Describe and explain the formation of a gley soil.

Answer 3

• A gley soil is formed as a result of the following factors:
  ➞ parent material
  ➞ climate
  ➞ relief/drainage
  ➞ vegetation
  ➞ and organisms

1. Firstly, the parent material is impermeable clay, which causes waterlogging.
   ➞ This is because gley soils are found on flat surfaces, such as the foot of a slope, which means water cannot drain away.
2. Secondly, low temperatures lead to a slow rate of decomposition of organic matter, creating a thin acid humus.
   ➞ Also, due to the cold climate, little organisms are present, which result in a lack of mixing of the horizons, meaning the soil horizons are clearly defined.
3. Also, as a result of high levels of waterlogging (precipitation exceeding evaporation), this results in anaerobic soil conditions (little oxygen)
   ➞ which gives the soil a blue/gray appearance.
4. Lastly, mottled red colour can occur within the soil if iron deposits are found.

Question 4

• What are the annotations of PODZOL soil profile?

Answer 4

1. A/O HORIZON:
   ➞ Layers of needles and cones from coniferous forests.
   ➞ Thin, black acidic humus (mor) as humification is slow
   ➞ Shallow and spreading roots
2. A HORIZON:
   ➞ Ash grey lower ‘A’ horizon with a sandy texture as minerals leach out.
   ➞ Some darker staining in the upper ‘A’ horizon from humus.
3. E HORIZON:
   ➞ Iron pan forms when a lot of iron is deposited and accumulated.
   ➞ Sometimes waterlogged as iron pan prevents drainage.
4. B HORIZON:
   ➞ Clearly defined horizons as there are few soil biota
   ➞ Reddish, brown layer as rich in iron and aluminium oxides.
5. C HORIZON:
   ➞ Weathered parent rock
   ➞ Parent material, generally weathered rock or glacial materials.

Question 5

• What are the annotations of BROWN EARTH soil profile?

Answer 5

1. A/O HORIZON:
   ➞ Abundant leaf litter from deciduous woodland
   ➞ Mull humus: thin black layer with loamy texture
   (mixture of sand, silt and clay)
2. A HORIZON:
   ➞ Darker brown ‘A’ horizon - enriched with nutrients
3. B HORIZON:
   ➞ Lighter brown in upper ‘B’ horizon with some staining from organic matter
   ➞ Dark brown/red brown in lower ‘B’ horizon
   ➞ Presence of soil biota (e.g. worms) mixes layers (indistinct horizons)
   ➞ Well drained, but an iron pan may be present in the ‘B’ horizon caused by moderate leaching.
4. C HORIZON:
   ➞ Long roots break up parent material and take nutrients up.
   ➞ Clay particles in C horizon above the bedrock.

Question 6

• What are the annotations of GLEY soil profile?

Answer 6

1. A/O HORIZON:
   ➞ Short shrubs and grasses with short roots
   ➞ Black with acidic humus as humification is slow
   ➞ Silty (smooth) texture
2. A HORIZON:
   ➞ Dark brown/grey colour
   ➞ Build up of organic material in ‘A’ horizon - peat may form
   ➞ Anaerobic conditions (little oxygen) and little soil biota, results in clearly defined horizons
3. B HORIZON:
   ➞ Very little leaching because soil is frozen for most of the year
   ➞ Waterlogged blue/grey ‘B’ horizon due to lack of oxygen
   ➞ Much gleying (waterlogging) due to poor drainage, flat land and impermeable permafrost.
   ➞ Large rock fragments as weathering is really slow
4. C HORIZON:
   ➞ Bedrock
   ➞ Permafrost below 1 metre - summer heat does not penetrate.