Biosphere Soils Soils properties and formation processes:
properties of podzols, brown earths and gleys horizons, colour,
texture, drainage the influence of soil-forming processes on
profiles as demonstrated by podzolisation, gleying, organic and
nutrient movement SQA Biosphere Soils Terminology Pedalfer soil:
soils where precipitation exceeds evaporation wet areas. Pedocal
soil: soils where evaporation exceeds precipitation dry areas. mor:
acidic humus associated with coniferous forests/tundra areas mull:
chemically neutral humus associated with deciduous forests
anaerobic : without oxygen gleying : waterlogging eluviation :
movement of humus, chemical substances, and mineral particles from
the upper layers of a soil to lower layers by the downward movement
of water through the soil profile illuviation : Deposition of
humus, chemical substances, and fine mineral particles in the lower
layers of a soil from upper layers because of the downward movement
of water through the soil profile Biosphere Soils What is soil?
Soil is a mixture of weathered rock, decayed organic matter, water
and gases. Mineral matter. This consists of minerals from chemical
and physical weathering of the parent material. Organic material.
Material from decaying plants and organism. Air and water. Ever
changing and fills the voids or spaces in the soil. Soil formation
Relief Climate Vegetation Time Humans Drainage
Biosphere Soils Soil forming processes Relief Climate Vegetation
Soil formation Time Humans Drainage Soil biota Parent material
Biosphere Soils Soil forming processes Climate Climate Temperature
and precipitation have a major influence on the soil.Higher
temperatures encourage soil biota activity whilst the opposite is
true. In wetter areas where, precipitation is greater than
evaporation, this causes the leaching of the soil and the removal
of soluble minerals and humus.However where evaporation is greater
than precipitation, water actually moves upwards through the soil,
called capillary action, and this brings minerals from deeper down
up to the surface. Biosphere Soils Soil forming processes Relief
and drainage Relief and drainage A steep slope will allow water to
run-off and increase the chances of soil erosion.Flat land is
usually poorly drained and this waterlogging can prevent soil
forming properly. Aspect can lead to south-facing slopes being
warmer and encouraging biota activity and vegetation more so than
in north-facing slopes. The ease with which water can pass through
as soil can also affect its development. Biosphere Soils Soil
forming processes Vegetation Vegetation Vegetation provides plenty
of humus aiding soil fertility.Soil biota activity is encouraged
and these areas are more likely to be warm and moist further
improving soil fertility.The type of vegetation present will affect
the type of soils that develops. Biosphere Soils Soil forming
processes Humans Humans People increasingly cause change in
soils.By clearing woodlands in one area, planting trees in another,
growing crops, adding chemicals and fertilisers, draining marshes
the soil is altered much more quickly than would occur naturally.
Biosphere Soils Soil forming processes Soil biota Soil biota This
is all the animals living in the soil.Bacteria, worms, plants,
roots and insects all absorb nitrogen, mix the soil by burrowing
through it, and also aerate it (create air pockets that can be
filled by water).The decaying humus in the topsoil makes this the
most fertile section of any soil. Biosphere Soils Soil forming
processes Parent material Parent material This is the main rock
type under the soil, usually the bedrock (regolith).The parent
material affects the colour, texture and chemical make-up of the
soil.Eg red sandstone bedrock produces red, sandy soil. Biosphere
Soils Soil forming processes Time Time Long periods of time are
needed for soils to reach maturity by the processes already
mentioned (about 1000 years for one cm - in many parts of Britain
we have had only 10,000 years since the last Ice Age stripped the
original surface soils away).It is thought that years are needed
for a soil to settle and mature. Topsoil Subsoil Regolith A Horizon
B Horizon Soil profile C Horizon
Biosphere Soils Soil profiles A soil profile is a vertical section
from the surface vegetation to the bedrock. By examining the
different layers or horizons it is possible to work out the soil
type. A Horizon The A Horizon: This is the main layer and consist
of a mixture of organic and inorganic material. This is usually
nutrient rich and fine textured. Often referred to as topsoil.
Topsoil Subsoil B Horizon Soil profile The B Horizon: This is the
subsoil, which contains less organic matter and is coarser in
texture, reflecting the importance of weathering.Nutrients may
leach out of the A Horizon. Regolith C Horizon The C Horizon: This
is the zone of regolith (fragments of rock). Large particles sit on
the underlying bedrock. Soil profile can vary in depth. In Britain
the average depth is 1.5m Biosphere Soils Brown Earth forest soils
Soils Biosphere Brown Earth forest soils Biosphere Soils Brown
Earth forest soils Location:Temperate deciduous forests of Central
Europe, Russia and North America. Further south than podsols.
Climate: Moderate climate.Milder winters, cooler summers and lower
precipitation, allowing more rapid decomposition although it is
still exceeds evaporation (pedalfer).Good conditions for vegetation
growth/soil biota. Relief & drainage: Gently rolling landscape,
allows soil to drain well. The A horizon is greasy due to its high
organic content and is a light brown colour due to the
humus.Leaching occurs but is less than in other soils from wetter
areas, but where it is more pronounced an iron pan may develop in
the B horizon. Soil biota: Warmer temperatures encourage soil biota
activity, making horizons less distinct.Leaf litter is more rapidly
decomposed. Biosphere Soils Brown Earth forest soils Natural
vegetation: Deciduous forests (ash, beech, oak).Plentiful supply of
leaf litter.The resulting humus is deep and only slightly acidic
(mull). Type of soil: Horizons here a less distinct due to more
soil biota activity mixing the layers.A pedalfer soil, but less
acidic.more alkaline soil due to leaf litter type. Processes:
Climate is less of a negative influence mixing is promoted vis
biota and some gentler leaching may occur, possible leading to the
development of an ironpan. Parent material: Weathering of the
parent material contributes to the soil forming process here. Human
use: More fertile and useful than the other main soil types and
populations here are greater.With the addition of manure and
fertilisers these soils support grain crops and grazing cattle. A
Horizon B Horizon C Horizon
Biosphere Soils Brown earth soils Precipitation = evaporation
approx Deciduous trees/ heathers/shallow roots Thick leaf debris
Mild acid humus with plant foods A Horizon Brown layer well aerated
Dark brown layer No marked horizons Merging boundary due to mixing
by biota B Horizon Lighter brown layer Deep brown layer C Horizon
Parent material Biosphere Soils Podsol soils Soils Biosphere World
biomes - Podsol soils Biosphere Soils Podsol soils Location:
Northern coniferous forests. Climate: Long cool/cold winters and
short mild summers.Precipitation can be variable low to fairly
heavy.Considerable snowfall though leading to spring snow-melt..
Leads to low soil biota activity and slow decomposition. Relief
& drainage: On mountain sides or tops, up to 350m.Precipitation
and drainage leads to rapid leaching of iron and aluminium oxides
(eluviation) from the A horizon leaving it rich in silica and
ash-grey in colour. The deposition of iron oxides in the B horizon
(illuviation) creates a red-brown colouring and may concentrate to
forma thin solid layer called an iron pan.This impedes drainage and
can cause waterlogging. Soil biota:Not much activity here because
of the cold climate and this means that the soil is not mixed,
leading to clear horizons developing. Biosphere Soils Podsol soils
Natural vegetation: Coniferous trees (pines, spruces,
firs).Produces litter of needles and pines, creating a thin acidic
humus (mor). Type of soil: Heavy with aluminium and iron, leading
to an acidic pedalfer soil.This soil has clearly defined horizons.
Processes: The climate has a strong influence here, ie lack of
warmth limits soil biota activity restricts mixing of soil and
causes humus to decay slowly; and leaching of iron and aluminium,
as spring snow melts, and humus causes an iron pan to develop.
Parent material: This only has a small influence with podsols.
Human use:Mainly used for commercial forestry plantations
(conifers). If lime were added, some cultivation could take place
with oats, potatoes or hay.Waterlogging due to the ironpan is a
major problem. A Horizon B Horizon C Horizon
Biosphere Soils Podsol soils Precipitation > evaporation
Coniferous trees/ heathers/shallow roots Layer of needles and cones
A Horizon Raw,black acid humus (mor) Sandy texture Ash grey layer
Iron pan impedes drainage B Horizon Reddish brown layer Denser
texture C Horizon Parent material Biosphere Soils Gley soils Soils
Biosphere Gley soils Biosphere Soils Gley soils Location: Found in
Tundra areas, or in places with poor drainage and low temperatures
eg Dartmoor (SW England) Climate: Cold and wet.Summers are mild and
brief and severe winters limit soil biota activity.The important
factor here is the lack of warmth.The continual process of freezing
and thawing, and consequent expansion and contraction, leads to
vertical mixing of soil particles and poorly defined horizons. The
presence of permafrost impedes drainage. Relief & drainage: Wet
and exposed flat regions with very poor drainage - the soil is
damp/waterlogged due to the permafrost.The presence of water here
causes a lack of oxygen (anaerobic conditions), leading to a
gleying of the soil, turning it blue-grey in colour and greasy to
the touch. Soil biota: Severely restricted due to extreme cold and
waterlogging.Soil is mixed by freeze/thaw action, but very slowly.
Biosphere Soils Gley soils Natural vegetation:Vegetation growth is
limited due to lack of warmth and waterlogging.Typically mosses,
lichens and marsh vegetation dominate.Larger plants cant survive
due top the shallow soils (permafrost).Produces a dark, acidic
humus (mor). Type of soil:Pedalfer soil.Clearly defined horizons.
Processes: As the soil is usually waterlogged it is deficient in
oxygen, limiting soil biota activity.Litter is broken down very
slowly in the cold temperatures.This soil is closely linked to the
climate and vegetation. Parental material: Fragments of parent
material are moved through this soil by freeze/thaw action. Human
response: Limited potential for humans so populations are scarce.By
ploughing, liming and fertilising/manuring this soil is still only
capable of growing low value crops such as oats or potatoes.These
areas are remote from population centres though so profits would be
hard to make with such crops. A Horizon B Horizon C Horizon
Biosphere Soils Gley soils Precipitation > evaporation Mosses
and lichens Grassy meadowland/small shrubs A Horizon Silty texture
Black withacid humus (mor) B Horizon Waterlogged blue grey gleyed
mud Angular rock fragments Waterlogged C Horizon Permafrost Parent
material Impermeable clay Biosphere Soils Summary Brown Earth
forest soils Summary: Precipitation is slightly greater than
evaporation, leading to a downwards movement of water and moderate
leaching.A narrow hard pan can sometimes develop. Faster
decomposition due to warmer temperatures and less water.Lots of
soil biota activity worms, rodents, insects. Litter is mainly from
deciduous leaves, leading to only a mild acid humus. Clearly
defined horizons. Biosphere Soils Summary Podsol soils Summary:
Precipitation is greater than evaporation, leading to a downwards
movement of water andleaching. An iron/aluminium hardpan is formed
which acts as a barrier to drainage. Low temperatures result in
limited biota activity and a slow breakdown/decomposition of
litter. An acidic (mor) humus develops due to the layer of pine
needles/fir cones. Clearly defined horizons. Biosphere Soils
Summary Gley soils Summary: Damp waterlogged soils.Inadequate
drainage.Permafrost layer may be present. Poorly defined horizons.
Dark, acidic (mor) humus develops from the slowly decaying mosses,
lichens and harsh vegetation. Limited soil biota activity due to
waterlogging and low temperatures, so little biological
activity.Humus decays very slowly. Soil profile Biosphere Soils
Soil profiles
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Soil profile A Horizon B Horizon C Horizon
Biosphere Soils Brown earth soils Precipitation = evaporation
approx Deciduous trees/ heathers/shallow roots Thick leaf debris
Mild acid humus with plant foods A Horizon Brown layer well aerated
Dark brown layer No marked horizons Merging boundary due to mixing
by biota B Horizon Lighter brown layer Deep brown layer C Horizon
Parent material A Horizon B Horizon C Horizon
Biosphere Soils Podsol soils Precipitation > evaporation
Coniferous trees/ heathers/shallow roots Layer of needles and cones
Raw,black acid humus (mor) A Horizon Sandy texture Ash grey layer
Iron pan impedes drainage B Horizon Reddish brown layer Denser
texture C Horizon Parent material A Horizon B Horizon C
Horizon
Biosphere Soils Gley soils Precipitation > evaporation Grassy
meadowland/small shrubs Silty texture Black withacid humus (mor) A
Horizon Waterlogged blue grey gleyed mud B Horizon Angular rock
fragments Waterlogged Permafrost C Horizon Parent material
Impermeable clay