Soils - biosphere

Question 1

5 major components of soils

Answer 1

• Minerals : from weathered parent rock from which the soil develops (plant growth)
• Air: essential within the soil for plant growth and living organisms
• Water: essential for living plants and organisms and an important influence on the upward and downward movement of nutrients
• Organic matter: from decaying plants and animals
• Biota: living organisms (bacteria, worms, insects)

Question 2

Elements that influence soil formation

Answer 2

• Parent material: giving nutrients as the rocks weather and decay. contributes to Texture, depth, drainage, colour and quality
• climate: water. temperature changes and sunshine
• Vegetation and soil fauna: providing organic material and mixing up the soil.
• relief of the landscape: influences depth, drainage and texture
• Time: processes of weathering, accumulation of organic matter and water movement are very slow

Question 3

Parent material

Answer 3

• regolith
• unconsolidated materials such as boulder clay, gravels and alluvium from rivers
• defines whether the soils feels gritty (sandy), smooth and soapy ( silt) or sticky and plastic when wet (clay)

Question 4

Climate

Answer 4

• most important factor
• humid climates speed up weathering and plant growth, producing deeper soils with more organic matter
• lots of rainfall: percolates water down through the soil and leaches (drains away) minerals such as calcium, aluminium and iron

Question 5

Vegetation and soil fauna

Answer 5

• soil fertility: concentrate organic matter and nutrients at the surface
• determines the properties of the humus ( a dark-brown or black layer of partially decomposed plant and animal matter)
• stabilising the soil as they reduce soil erosion and run-off

Question 6

Relief

Answer 6

• as height increases, so does the amount of precipitation, cloud cover and wind; while temperature and growing season decrease

Question 7

Time

Answer 7

• when they are young; soils retain the features of their parent material.
• shaped by climate and environment

Question 8

3 different types of soils

Answer 8

• podzols: found in areas where climates are cool and where coniferous woodland is common; common in North and West of the UK
• Brown earth: common in Europe, deciduous woodland,
• Gley: influenced by parent rock and found in many climate zones

Question 9

Podzols

Answer 9

• found where there is good drainage and water moving downwards through the soil, where precipitation exceeds evaporation
• strongly acidic due to the overlying vegetation producing acidic humus
• well defined horizons
• used for forestry and recreation

Question 10

Horizons of a Podzol

Answer 10

• Ao Horizon: green in colour, pine needles, pine cones; very slow to decay due to the cold climate
• A horizon: ash grey due to eluviation (washing out of minerals), silty texture
• B horizon: red or dark brown due to illuviation of iron and clay. Hard pan present in this horizon, forms when iron accumulates over a period of time.
• C horizon: contains the parent material, not accessible due to iron pan

Question 11

Brown earth

Answer 11

• found further south than podzols
• drier and milder climate
• precipitation exceeds evaporation, so gradual leaching occurs
• brown colour throughout
• free drainage, but if an iron pan develops, the topsoil can become waterlogged
• most fertile in Scotland
• used for agriculture

Question 12

Horizons of brown earth soils

Answer 12

• Ao Horizon: ( mull humus) green in colour, consists of grasses, herbs and fleshy leaves due to mild climate and action of soil biota
• A horizon: well aerated due to soil organisms and bacteria. Dark brown is colour as humus replaced minerals. Limited leaching occurs as closer balance between precipitation and evaporation
• B horizon: lighter brown than the A horizon as humus is less abundant
• C horizon: contains parent material. Tree roots can penetrate here to extract minerals

Question 13

Gley soils

Answer 13

• most extensive soil cover in Scotland, on gentle slopes and in areas of high rainfall
• extensively waterlogged, forming anaerobic conditions
  (decaying of bacteria is slowed down)
• iron compounds in the soil are reduced
• used for rough grazing or forestry

Question 14

Horizons of Gley soils

Answer 14

• Ao Horizon: (mor humus - acidic); brown in colou, made from organic matter which is slow to decay due to anaerobic conditions
• A Horizon: dark grey in colour due to removal of iron compounds, silty texture due to poor drainage; acidic
• B Horizon: blue or grey in colour as iron compounds are altered chemically, orange/brown mottles due to re-oxygenation of iron, waterlogged
• C Horizon: impermeable rock or permafrost