Biosphere Flashcards
The A horizon contains…
A mix of humus and and other mineral particles
The B horizon contains…
Coarser material - this is the subsoil layer.
The C horizon contains…
Weathered rock fragments
The D horizon is the…
Bottom layer - this is the parent rock layer
Define Leaching
Leaching occurs when there is excessive rainfall, water moving downwards through the soil transports minerals downwards.
Capillary Action is…
The process by which soil moisture moves through the fine pores of the soil. This produces more alkaline soils.
Leached soils such as…
Tend to be…
Podsols
Acidic
The rate of weathering of the parent rock greatly depends on…
The climate - the quickest rate of breakdown occurs in hot, humid climates
What are the first two stages in the formation of soils?
- The weathering of parent rock over a considerable period of time
- The result of adding water, gases, living organisms and decayed organic matter.
The type of vegetation in an area is related to the amount of precipitation. The vegetation provides humus. Humus is found more in… than in…
Tropical Forests
Tundra Areas
Define Eluviation
The washing out of material, that is the removal of minerals such as Calcium and aluminium, and organic material from the A horizon.
Define Illuviation
The deposition of washed material in the subsoil. Heavy minerals are deposited much deeper, effecting soil fertility.
Organisms within the soil….
Affect the breakdown and decay of vegetation and therefore impact on the depth of the humus layer.
Living creatures affect the development of the soil through…
Exposing the soil to air by aerating it and can add to the chemical balance of the soil through their excreta
Podsolisation is common in areas where…
Precipitation greatly exceeds evapotranspiration - Common in areas with cool climates and mainly coniferous forest
Podsolisation is when…
Percolating rainwater becomes acidic as it passes through an acidic humus formed from falling pine cones and needles.
The water dissolves and removes iron and aluminium oxides from the topsoil -leaving a high level of silica in the A horizon.
Greying occurs when…
Waterlogged conditions exist in the soil due to the loss of water from the soil being restricted.
In poorly drained areas where the land is more gently sloping.
Describe the formation of a podsol
Falling pine needles and cones create an acidic humus called mor.
Very little mixing or movement of the horizons due to earthworm absence.
Cementing affect takes places between the A and B horizons to form a hardpan which effects drainage - upper layers become waterlogged.
Decomposition of Ao horizon is very slow due to the cold climatic conditions.
High silica residue left behind due to leaching in A horizon caused by meltwater during spring.
Describe the colours in a Podsols horizons
Ao - Black ; Layer of cones and needles
Mor
Mineral and organic layer
A - ash-grey layer with iron pan due to mineral removal
B - Reddish- brown layer due to iron oxides
C - Parent material - grey with black weathering
Describe the formation of a brown earth soil
Humus layer is thick/fertile due to the variety of vegetation that is decayed.
Warmer - Leaf litter decomposes quick due to organisms in the soil - less acidic humus referred to as mull.
Precipitation exceeds evaporation - causing leaching. Not enough to cause Podsolisation.
Horizons merge more than in Podsols due to the activity of biota.
Re deposition of iron and aluminium due to Illuviation causes reddish brown colour.
No hardpan unlike Podsols and soils tend to be free draining.
High clay content throughout profile - increasing soil fertility.
Brown earth soil colours
Ao - Leaf debris
Black - with mild acid humus containing plant foods
A - Dark brown layer
B - Brown layer
C - Deep roots take up the bases
Weathered parent material at bottom
Describe the formation of a tundra grey soil
Subsoil remains frozen throughout the year. Brief summer allows for ground surface to thaw but meltwater cannot melt freely.
Results in soil becoming waterlogged or gleyed
Bacterial action restricted due to cold temps.
Waterlogged soil lacks oxygen and tundra vegetation is also limited.
Alternate periods of freezing and thawing cause disturbance and mixing of soil.
Restricted use and less defined horizons.
Colours in a Gley/Tundra soil
Small shrubs on top
A horizon - Black acidic humus
B - Waterlogged
Blue grey
Clayey mud
C - Angular rock fragments
D - Stone coloured
Permafrost
Bedrock
Capillary Action
The upward movement of water in a soil
