BIOSPHERE

Question 1

brown earth soil

Answer 1

Brown earth soils are found in temperate deciduous woodland. There is a large amount of recycled leaf litter, especially in autumn. Mild temperatures cause rapid decomposition, producing less acidic humus.

There are many soil organisms, which mix the soil and create well-defined horizons. The A horizon is dark brown and fertile due to humus, while the B horizon is lighter with less humus. Leaching is limited because of a balance between evaporation and precipitation. Deep tree roots recycle nutrients by bringing minerals from lower horizons.

Question 2

podzol

Answer 2

Podzol soils are found in cold, wet climates, often in coniferous woodland. Decomposition is slow due to low temperatures, producing more acidic humus. High rainfall and snowmelt cause pronounced leaching.

The A horizon becomes ash-grey due to eluviation, where iron, clay and humus are leached out. These materials accumulate in the B horizon through illuviation, giving it a redish colour and sometimes forming an iron pan, which restricts drainage. The soils are nutrient-poor and have shallow roots.

Question 3

Gley soils

Answer 3

Gley soils form in waterlogged areas where precipitation is > evaporation. poor drainage often due to clay causes low oxygen conditions.

cold temperatures slow vegetation growth and decomposition leads to a thin acidic humus layer, with little soil biota, decomposition and nutrient recycling is limited, so horizons are weakly developed and leaching is low.

waterlogging created anaerobic conditions where iron is reduced, turning the soil blue-grey. when the soil dry’s out oxygen returns and red mottling can form often around plant roots.