Biosphere

Question 1

What is the formation of a pod soil

Answer 1

-coniferous trees have short roots so don’t bring up minerals from weathered bedrock

-pine needles decompose slowly due to cold conditions and the humus layer is thin and is also acidic, as pine needles form an infertile Mor Humus.

• high rainfall and water from snow melt means leaching takes place. This washes away the minerals such as iron and aluminium out of the top soil leaving it grey in colour and infertile
• distinct layers as cold conditions mean few organisms in the soil so little mixing

-illuvation of minerals leave a hard pan. This can sometimes impede drainage and cause water logging

• reddish brown B horizon due to re-depositing of minerals which have been leached out

-

Question 2

What is the formation of brown earth soil

Answer 2

• deep leaf litter from deciduous trees. These decay more quickly in mild climates to produce a rich, fertile humus layer
• decidious leaves decay to form a less acidic and more fertile MULL humus
• precipitation exceeds evaporation so some leeching but minerals form organic matter are not broken down or washed away. Meaning minerals remain in the top soil so darker in colour
• older climate means more soil biota are present eg. Worms. This means the soil is well mixed with no distinct horizons
• lack of hard pans means a free draining, well aerated soil
• long roots bring minerals up from lower down in the soil producing more fertile top soil
• some lee hing can lead to some re- deposition of iron and aluminium, leaving a darker brown colour
• parent material is often sedimentary rocks. These are permeable so no water logging and break down, the weather can easily release minerals which adds to fertility

Question 3

What’s the formation of a gley soil

Answer 3

• there is an acidic mor humus created by a slow decay of heather, grasses etc in the cold climate
• there are short rods which means few minerals are brought up from lower in soil
• heavy rainfall/ snowmelt can cause leeching which can leave a greyish brownish layers. There may be some gleying
• there are a few organisms due to the cold and anaerobic conditions means little mixing and distinct layers
• the pore spaces fill with water due to a lack in oxygen , this is because the organisms take oxygen from iron compounds, turning them from from a red to a grey ferrous colour
• they may have some red mottling, this is due to small air pockets appearing and re-oxygen is action taking place. This could be due from a presence of burrowing animals or soil dying in the summer
• the permafrost means water can’t drain away so water logging occurs. Flat land can also cause drainage issues
• you can sometimes find large angular rocks fragment s due to freezethaw weathering