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Global biomes
Ecosystem- a community of plants and animals interacting with each other and the environment
they live in (they are interdependent)
Biomes- large scale ecosystems which occupy distinct regions on earth
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Tundra- found in extreme high latitudes,
generally towards the poles at 60⁰ e
...
North
Alaska, no trees aka only low growing plants
can survive
Temperate grassland- found in mid latitudes
between 30⁰ and 40⁰ N/S
...
g
...
Less
extensive in Southern hemisphere e
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South
America

Hot dessert- located between 15⁰ and 30 ⁰
N/S where easterly trade winds blow
...
g
...
This is because the tundra receives very little solar insulation due to 1) very long
hours of darkness and 2) low angle of the sun in the sky
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Precipitation- precipitation levels are very low due to high pressure e
...
Annual precipitation in
barrow is only 110mm which mostly falls as snow
...
5m, there is a permanently frozen layer known as
permafrost
...
g
...

Above the permafrost the soils:
1) are waterlogged limiting percolation
2)have very low rates of decomposition of organic
c material as there are few soil organisms
3) Have no distinct layers
4) Very acidic, pH values can reach below 4
...
Frost heave may move some rock fragments towards the
surface
...
At the highest latitudes this may
extend as deep as 30cm but extends further in lower latitude areas
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The lack of plants cant fix the nitrogen in the ecosystem leaving limited nutrients and fertility
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Grasslands are far from the moderating influence of the sea aka not
effected by continentality
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During the spring/summer months the high temperatures mean there is a lot of
evapotranspiration, which reduces the amount of water available in the soil
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5m) and are rich consisting of two main horizons
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g
...
The
lack of rain coupled with high summer temps draw water
upwards from the lower levels through capillary action bringing
nodules of calcium carbonate into the upper c horizon aka Cca
horizon
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Precipitation levels are low overall and there are
significant evapotranspiration during the heat of the summer months
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They experience limited leaching and some capillary action
during the summer
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• Tundra biome temperatures are very low in the winter and quite low
during the summer
...

• The low temperatures of the tundra mean that the soils here are
underlain with a permafrost layer
...
g
...

The soils have limited fertility
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The thawing of permafrost is damaging infrastructure
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These
impacts are projected to increase throughout the 21st century
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The ecosystem as an open system
Inputs

Stores

Transfers

Outputs

Energy

photosynthesis Flora and
fauna (stored
as sugars and
proteins)

When organic
matter isn't
consumed by
hetrophores

respiration

Nutrients

Precipitation
and
weathering

Fallout
Decay
Uptake

Run off and
leaching

Biomass
Litter
soil

Energy flows
Energy moves through the ecosystem through a series of trophic levels and
then leaves via heat
...
They are
called producers or autotrophs
...

in the second trophic level the herbivores consume plants from the first level
...
Finally the fourth
trophic level is made up of larger carnivores and omnivores
...
g
...


On average only 10% of energy is transferred
up to the next trophic level
...
g
...
)
• The transfer of food energy is incomplete as
not everything that could be eaten is eaten e
...

animals dying of old age
• the transfer of food energy is insufficient as
not everything eaten can actually be
metabolised so is excreted which is then
broken down by detrivores thus leaving the
ecosystem
Due to this energy loss there is usually no more
than four trophic levels in an ecosystem

Nutrient cycles

Decay

Leaching

Nutrients mainly cycle around
stores within the ecosystem
along with some inputs and
outputs
The diagram can be drawn
proportionally to show the
relative amounts of nutrients
in the stores and transfers
The rate of nutrient transfer can
be affected by factors such as
• Climate (hotter climates have
faster decomposition)
• Soils (acidic soils have fewer
soil organisms so
decomposition is slower
• Vegetation type (coniferous
tree leaves take longer to
decompose than deciduous)

case study – Breen Wood forest, Ballycastle, Co
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Soils are thin and
have an acidic Ph (4
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High rainfall and sloped
relief cause lots of leaching
Because of these Abiotic factors the range of plants and
animals is smaller than expected in deciduous forest
and the 200 year old oak trees are half the size of
what they would be in lower areas
...
The harsh
climatic conditions mean the range of heterotrophs
is more limited than other deciduous forests
...
1% of the energy from level 1) is
passed to the fourth and final level, the tertiary
consumers aka carnivores and omnivores including
sparrow hawks, buzzards and badgers
At each trophic level only 10% of its energy is passed on
Detrivores which are found at each level include worms
and maggots, their work is limited due to the
podsols and decomposition is slow
Secondary
consumersbuzzard, badgers

decomposers

Secondary consumersblue tits, gold crests
Herbivores- orange tip butterflies,
red squirrel
Autotrophs- brambles & mosses hazel & holly,
oak & birch

Nutrient cycles in Breen Wood
Three main stores of nutrients•
biomass store- by far the largest store
consisting of the plants (autotrophs) such as oak
trees, hazel and mosses and the animals such as
buzzards, blue tits and orange tip butterflies
...
This contributes fresh leaf litter
via the fallout pathway to the litter store
•
Litter store- smaller than the biomass store but
is larger than the typical for a deciduous forest
due to the acidic podsols soils and cool average
summers (15⁰C)
...
It may take years for detrivores to
decompose leaves for them to travel to the soil
store via decay
•
Soil store –Similar size to the litter store
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biomass

litter

soil

Examples of food chains
Autotroph

herbivore

carnivore

Oak leaf

caterpillar

blue tit

Plant succession
Plant succession- the processes of change in plants, along with the soils and microclimate, in an
ecosystem
...

Plant succession is a series of changes that take place in vegetation over time as one plant species
replaces another
Primary succession- a succession that occurs on a previously unvegetated surface e
...
sand dunes
...

•Plants modify the microclimate- reducing ground wind speed,
sheltering the soil therefore there is less evapotranspiration and
higher soil temperatures
This creates conditions more favourable for other plant types which
will then come replace the previous plants but will also increases the
variety of species (each seral stage still has one dominant plant)
This occurs until a climatic climax is reached

Changes during a succession
Soil changes
Depth increases

Due to the addition of more organic matter from the biomass and more weathering of
the bedrock

Humus increases

More organic matter is added to the soil via nutrient cycling

Moisture increases

The humus aids moisture retention and the shade from plants reduces
evapotranspiration from the soil

Stability increases

The increasing root system binds the soil together

pH increases

The soil becomes less alkaline due to the addition of humic acids

Colour darkens

More organic matter is added to the soil via nutrient cycling

Plant changes
Biomass and plant
longevity increase

Deeper and richer soils can support larger and longer living plants such as trees
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g
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Heather moorlands that
are found in many British
isles
Where there should be a
deciduous forest climax the
forest have been cleared
for sheep grazing which
allows heather plants to
dominate
The heather is burned on a
15 year cycle to return
nutrients to the soil
preventing succession

Case study- Magilligan, NW Northern Ireland
Irelands largest area of coastal deposition (32km² area of flat
ground) consisting of wind and sea blown deposits
...
It
is resistant to salt and drought by storing water in its
succulent leaves and thrives on being buried
Sand couch grass helps slow and collect sand blown from the
beach
Vegetation is sparse with 80% of the dune being exposed
sand
Winter storms often wash away embryo dunes but they
usually build up again by the next
Fore dunes (yellow dunes)
Slightly higher dunes just inward of embryo dunes,
High proportion of visible sand (over 20%)
These are mobile dunes gathering sand and growing in
height
Marram begins to dominate which is tolerant of salt and
thrives on being buried by sand
...
Waxy surfaces on the outside of the leaf
help reduce moisture loss
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Long tap roots help tap
water and help to stabilise the sand allowing other
species to colonise the dunes
...
These are often near or below the water table
The environment is more sheltered – wide range of plants are
found here e
...
Wild strawbs and buttercups
Grey dunes (older fixed dunes)
Conditions of plant growth improves with distance from the
beach
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It is more sheltered so less salt is carried in by
the wind
...

The moisture and nutrients in the humus help
colonisation
...
g
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Plants with leafy stems (birds
foot treft) and grass like plants (meadow grass) are
present
Dune scrub (climatic climax)
The climatic climax vegetation in the umbra dune is a
deciduous forest (willow, hazel, birch trees)
Under the tree canopy there ground surface is rich in insect
and other life
In parts of the umbra dune system the climax vegetation has
been replaced including the planting of coniferous woods

Need to know summary!!!
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An ecosystem is an open system consisting of Abiotic components (climate and
soil) and biotic components (plants and animals) interacting with each other
After entering the ecosystem via photosynthesis
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The energy transfers are very inefficient but
much of the energy is lost before it reaches the next trophic level
...
In addition
there are inputs (via precipitation and weathering) and outputs (via runoff and
leaching) of nutrients from the ecosystem
Plant succession refers to the process of change in vegetation over time whereby
one dominant plant species replaces another through a series of seral stages until
the plants reach a balance with the environment known as a climatic climax
The initial pioneer plants must be adapted to harsh conditions of soils and
microclimate
...
Thus vegetation coverage,
plant height and species diversity increases as succession continues
If humans stop the natural process of succession by activities such as grazing or
burning, this stage is known as a plagioclimax



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