Biosphere

Question 1

Podzol soil

Answer 1

1. Low temperatures lead to slow decomposition.
2. Coniferous needles and cones produce acidic (mor) humus.
3. High precipitation leads to leaching which is the downward movement of the aluminium and iron oxides, leading to formation of an iron pan between the A/B horizons.
4. This iron pan may impede drainage causing water logging.
5. Eluviation leaves an ash grey A horizon.
6. Illuviation leads to a reddish brown B horizon.
7. Limited soil biota leads to well defined horizons.
8. Found on steep slopes, which further encourages leaching.
9. Shallow roots mean limited absorption of deep leached minerals and limited nutrient recycling.

Question 2

Brown earth soil

Answer 2

1. Deciduous forest vegetation provides deep leaf litter, which is broken down rapidly in mild/warm climate.
2. Trees have long roots which penetrate deep into the soil, accessing nutrients from lower layers which are recycled to leaves.
3. Soil organisms ensure the mixing of the soil, aerating it and preventing the formation of distinct layers.
4. Precipitation slightly exceeds evaporation, giving downward leaching of the most soluble minerals and the possibility of an iron pan forming, impeding drainage.
5. South-facing slopes in northern hemisphere with a greater amount of sunshine and higher temperatures increase the rate decomposition resulting in a thick mull humus layer.
6. Rock type 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.
7. Tends to be found on gentler slopes leading to lower rates of erosions so thicker soils.

Question 3

Gley

Answer 3

1. Cool to cold temperatures lead to a very slow rate of decomposition of organic matter creating a thin humus.
2. Plant roots do not penetrate deeply resulting in limited recycling of minerals back to the vegetation.
3. Anaerobic conditions means few organisms living in soil to burrow and tunnel through the soil.
4. The iron compounds are changed from red-brown to blue due to oxygen being extracted by microorganisms.
5. Red mottling in small air pockets due to re-oxygenation of the iron in the soil due to burrowing animals/soil drying out in summer.
6. Impermeable clay impedes drainage and causes waterlogging.
7. Found on flat surfaces such as plateau moorland or foot of slope means water cannot drain away. Poor drainage is the key soil- forming feature for this soil type.