Download Biosphere - RothesayGeography

The Biosphere
Soils
• All forms of life depend on soil. It is a
delicate, fragile living resource. It
needs to be managed carefully to
ensure sustainability.
• Soil is the uppermost layer of the earth.
Soil is made up of the following:
• Mineral Matter (weathered rock)
• Organic material (living plants and
animals)
• Water
• Air
And what percentages are they?
Water
25%
Mineral
Matter
Air
45%
25%
5% organic matter
• The mineral matter consists of material
derived from the parent rock by physical
and chemical weathering.
• The organism matter is derived from
decaying roots, leaves, needles and the
remains of dead organisms.
• The other two important components are
water and air which fill up the pore spaces.
These are found in variable amounts e.g. if
a soil is waterlogged it lacks oxygen.
What factors affect soil
development?
• Climate
How much water and air enter the soil - and their
temperatures - will affect the organic life of the soil and
evaporation rates on the surface. Water movement tends
to be down through the soil (Leaching).
• Relief
Different soils will form on different degrees of slope and
aspect. Gravity and temperatures will affect the degree
of slope movement and weathering.
• Parent Material
The rock type affects the acidity, texture and fertility of
the soil.
What factors affect soil
development?
• Soil Organisms
• These are important in decomposing
organic material and in mixing up the soil
components. They are most abundant in
warm, moist conditions.
• Time
The process of soil formation is very slow
yet it can be destroyed very quickly.
Soil Profile
A soil profile is a
vertical section
through the soil from
the surface vegetation
to the bedrock. A fully
developed soil profile
displays a sequence
of layers. Each layer
is called a horizon.
The A horizon is the
top soil.
• organic layer made
up of decomposed
leaf litter called
humus.
•Contains weathered
rock from below.
•Soil organisms
usually mix up the 2
components.
The B horizon is
the subsoil.
A
B
C
•Contains higher
proportion of
weathered
material.
•It is generally less
fertile.
•Most fertile layer
(usually).
The C horizon is the regolith.
•Weathered rock material which
provides the soil with its mineral
matter.
•Beneath the regolith is the bedrock
(Parent material)
Soil Classification- Zonal Soils
•
•
•
•
These are soils that broadly correspond to
the main biomes. Influenced by time,
climate and vegetation.
Examples are:
Podzols in the Taiga (coniferous forests)
Brown Earth soils in the deciduous forests
Tundra Gleys in the tundra
Intra-zonal soils
These are soils that are influenced by local
factors e.g. the parent material in an area
or local drainage. The climate is not an
important influence.
• Example:
• Gley soils
• Limestone soils
Azonal Soils
These are young, immature soils which
have not developed horizons. Examples:
• Alluvial soils deposited by rivers
• Boulder clay soils deposited by glacal
deposition.
• Volcanic soils
Ecosystems
An ecosystem is a unit which links all living
things (plants, animals, people) with each other
and with their physical environment (rock, soil,
air and precipitation).
• The driving force for the whole system is solar
energy.
• Ecosystems can exist at a variety of scales from
a single tree to the major biomes (bioclimatic
zones).
Solar energy
Precipitation
Soil
Vegetation
Man
The Ecosystem
Temperature
Relief
Biotic factors
Podzols-summary
Location- Europe, Northern Asia and
North America.
Climate- precipitation greater than
evaporation= leaching
Vegetation- pine woodland, coniferous
trees, heather moorland.
Low temperatures mean slow
decomposition of organic
matter producing raw humus.
Needles from conifer
trees produce raw
acid
Spring meltwater causes
leaching (downward
movement of water).
Low summer
temperatures= little
evaporation.
Leaching of
aluminium and iron
oxides leaves a silica
(light sandy layer).
Red / Brown iron or
hard pan.
Aluminium oxide
deposited in light
clay.
Thin layer of black humus.
Dark staining
Shallow roots of coniferous
trees take few minerals from
the soil.
Ash grey
Low temperatures
mean little earthworm
(or other organism)
activity, therefore
distinct horizons.
IRON PAN
Yellow / Brown
Waterlogging as water
cannot penetrate hard
pan.
leaching is dominant in the
A Horizon. The leaching
washes down the soluble
minerals such as iron, humus
and leaves behind a
bleaching horizon
(insoluble silicates).
RAW ACIDICS HUMUS (MOR) &
SHALLOW ROOTS
B
HORIZON
IRON PANGLEYING
The C horizon is derived
from the weathered parent
material.
The low
temperatures means
that there is little
mixing of the
horizons due to the
lack of soil biota.
Podzols are not naturally fertile soils. Lime needs to be added to
counteract the soils acidity and animal manure can improve the poor
quality mor humus.
Brown Earths
Location
• These forests are located on the west coasts of
continents between approximately 40° and 60° N/S of
the equator.
Climate
• Summers are cool (15-16°C) as a result of the relative
low angle of the sun, combined with frequent cloud
cover.
• Winters are mild.
• Precipitation is high (depressions throughout year).
• Although snow is common in the mountains it rarely lieslong at sea level.
Natural Vegetation
• Deciduous trees have a growing season of 6-8
months and they shed their leaves in the winter.
• Such species as oak, elm, ash, chestnut and
beech are common. They all develop large
crowns and have broad but thin leaves.
• The forest floor is often covered in a thick
undergrowth of brambles, ferns and in the
spring, bluebells.
Mild climate, rapid
decomposition of organic
matter. Humus is mild (not
raw) and alkaline.
Thick leaf debris,
much organic matter
in soil.
Deep roots plus
earthworm activity
caused by high
temperatures results
in mixing of the soil
and indistinct
horizons.
Iron pan can develop
where leaching is
more active.
Leaching
Iron pan
Light Brown
The soil biota helped
to decompose the
leaf litter quickly.
The B horizon is
not too distinct but
is lighter in colour
than the A horizon
as humus
becomes less
abundant.
The C horizon is
weathered
parent material.
The A horizon is well aerated
and dark brown in colour as
humus is enriched.
These mildly acidic brown
earth soils have been
extensively exploited for
agriculture and have
supported a much higher
density of population
compared with the podzols.
Tundra Gley
Location
• The tundra lies to the north of the taiga. It includes the
extreme northern parts of Alaska, Canada, Russia and
Greenland.
Climate
• Summers may have long continuous daylight, but with
the angle of the sun so low in the sky, temperatures
struggle to rise above freezing point and the growing
season is very short.
• Winters are long, dark and severe and the sea freezes.
• Precipitation is light and mainly falls as snow.
Natural Vegetation
• There are few species of plant in the tundra.
• Most are very slow and low growing such as
mosses, lichen and small shrubs.
• Most have small leaves to limit transpiration and
short roots to avoid the permafrost
(permanently frozen sub-soil).
• Much of the tundra is waterlogged in summer
due to the impermeable permafrost preventing
inflation.
Mosses, dwarf shrubsshort growing season
Little activity from
organisms because of
low temperatures.
Therefore breakdown
of material is minimal,
plus incorporation of
organic matter into the
profile is low= infertile.
Permafrost layer
prevents water from
draining downwards
therefore
waterlogging the
soil.
Rock
Fragments
Blue/grey
clayed
mud.
Permafrost
Bedrock
Slow decaying plant
mater results in raw
acid humus (slow
because of low
temperatures). Black
in colour.
Freeze-thaw action
(expansion and contraction)
leads to vertical mixing
incorporation of rock
fragments. Therefore no
distinct horizons.
The limited plant
growth due to the
climate produces a
small amount of litter.
There are few soil
biota due to the low
temperatures.
Spring meltwater
may cause a little
leaching.
If the bedrock is
close to the surface
the parent material
is weathered by
freeze-thaw action.
There is only a thin
layer of peaty
humus.
The permafrost acts as an
impermeable layer,
restricting moisture
percolation and causes
waterlogging and gleying
(blue-grey in colour).
Shattered angular
material can be raised
to the surface by frost
heave in winter.
Intra-Zonal Soil
The A horizon is dark in
colour due to the organic
matter.
Slow rate of decay because of
anaerobic conditions.
B horizon mainly bluey/grey
in colour due to continuous
waterlogging
C horizon (parent material) is
an impermeable layer.
Gleys can support wetlands,
permanent pasture and
arable farming once drained
and ploughed.
When soil is waterlogged
for a long time, its pore
spaces lose oxygen. Such
a soil is called anaerobic
and this means that any
decay of bacteria is slowed
down.
Soil Catenas
• A soil catena illustrates a sequence variation in soil
types down a slope where underlying parent material
is the same throughout.
Relief of the land
• angle affects the drainage conditions which then
influences the amount of leaching and gleying.
• The underlying parent material should be the same
along the slope.
• The climate should also be constant but altitude will vary
the climate.
Plant Succession
• A plant community (ecosystem) is a group of
plants that occur in the same place at the same
time.
• They evolve over time from simple beginnings
when pioneer plants colonise new land to even
more complex communities (building stage)
and eventually climax vegetation.
• During a typical plant succession, the ecosystem
will go through the following stages:
• On a plot of bare ground it is only a short
time before basic pioneering plants start to
colonise.
• pioneer plants stabilise the environment
binding the loose material.
• plants die and decompose the
environment conditions change and
humus starts to develop.
• Further developments of humus and
weathering means that the soil becomes
richer and deeper.
• competition between the plants may occur.
• new plants may be taller and create shady
conditions, altering the micro-climate.
• Plants continue to compete for the
available nutrients, water and space.
• Eventually the plant succession reaches
climax vegetation.
Climax Vegetation
This is the ultimate stage of plant
succession. It is reached through plant
communities going through plant
colonisation, competition and stabilisation.
It is when the vegetation no longer
changes. The vegetation is in a state of
equilibrium with the climate and soils of
the local environment.
Coastal Sand Dunes
Sand dunes are formed where:
1. there is a plentiful supply of sand
2. a strong onshore wind
3. there are obstacles to trap the sand at the bern
line (high tide mark).
• A plant succession on a sand dune is called a
psammosere. To study this plant succession
from pioneer plants to climax vegetation it is best
to look at a transect of coastal sand dunes.
Stand Line and Embryo Dune
(mobile dune)
• Sand may become trapped by seaweed or
driftwood on berns.
• Windborne seeds may germinate and a pioneer
community of annual plants such as sea rocket
grow.
• plants have to be able to withstand the dry, salty
conditions.
• plants allow sand to accumulate, The grasses
have runners and are extremely salt resistant.
• Sea couch cannot grow upwards and though the
sand and the sand dunes tend to be low.
Sea Couch Grass
Embryo and Foredunes at
Sandwood Bay
Sea Couch Grass colonising
foreshore
Embryo Dunes at John Muir
Country park near Dunbar
Embryo Dune
Sea Lyme Grass (1)
Sea Lyme Grass (2)
Yellow Dunes
(mobile dune)
• They are above the high tide limit, are dry
and exposed to wind.
• The dominant plant is marram grass.
• There is always bare loose sand between
the marram grass giving the dune a yellow
appearance.
Marram grass has adapted to the
harsh conditions as:
• It is xerophytic
• Its leaves are re-rolling inwards to reduce
transpiration.
• It has long tap roots.
• It can grow upwards very quickly.
Yellow Dunes at Sandwood Bay
Lagoon and Yellow Dunes
Marram Grass (1)
Marram Grass (2)
• Where marram grass dominates the sand
dunes will grow very quickly in height to 10
meters. The wind is forced up over the
dunes and in the lee of the dune, the
speed of the wind drops, and the windblown sand is deposited.
• This means the dunes migrate inland.
Grey Dunes and Slacks
(Fixed Dune)
• smaller in size as the grey dunes cease to
grow.
• As the fresh supply of sand is cut off
marram stops growing and begins to thin
out.
• plants die and decompose which adds
nutrients and the ‘soil’ is able to hold more
moisture.
• In the damp and wet hollows between the
dune ridges, where the watertable is close
to the surface, dune slacks develop
supporting water loving plants such as
rushes, iris, reeds and cotton grass.
• the dunes mature and becomes more
isolated from the sea, new embryo dunes
form.
Semi-fixed Dunes with Dune
Slacks
Dune Slacks
Snails and Mosses in Dune
Slacks
Bird’s Foot Trefoil (Fixed Dune)
Saltwort (1)
Saltwort (2)
Ragwort
Heathland and Woodland
• increasing distance= non-maritime species
enter the dune community.
• rich grasslands are found depending on
amount of calcium carbonate in the dunes
as.
• where the lime has been leached out
leaving the dune acidic, acid loving
heathland plants are found such as
heather.
• The final stage of this plant succession, is mixed
woodland where species such as pine, birch and
oak are common.
• Generally, in a transect through a sand dune
certain characteristics occur when moving
inland.
• Acidity increases
• Salinity decreases
• Water retention and biomasses increase.
• Exposure to wind is reduced
• Plant coverage and diversity increases.
Wind blown Hawthorn (Fixed
Dune)
The end