Biomes OCR

7.35-6

Tropical rain forest

Tropical seasonal forest

Temperate

deciduous forest

Temperate

deciduous forest

Boreal forest

Tropical grassland / forest ecotone (Bolivia)

Tropical grassland (Bolivia)

Tropical grassland = savannah (Tanzania)

Temperate grassland = prairie

Tundra

Bare rock in montane region (& boreal forest)

Cactus desert (Arizona)

Hot desert

Hyper-arid desert

EnergyEnergy

OCR 7.32

There are 2 types of There are 2 types of cyclecycle

EnergyEnergy

NutrientsNutrients

Trophic Trophic PyramidsPyramids

Trophic or energy Trophic or energy pyramids show how pyramids show how energy is transferred energy is transferred through an ecosystem.through an ecosystem.

They are an easily They are an easily accessible way of accessible way of looking at whether looking at whether there is dynamic there is dynamic equilibrium, or whether equilibrium, or whether the system is becoming the system is becoming unsustainable.unsustainable.

Trophic PyramidsTrophic PyramidsSunlight energy fixed Sunlight energy fixed by green plants is by green plants is passed through the passed through the ecosystem in food ecosystem in food chains and webs form chains and webs form one trophic level to the one trophic level to the next. As energy is next. As energy is passed through the passed through the system it is stored at system it is stored at various trophic levels. various trophic levels. The storage of energy The storage of energy (I.e. the amount of (I.e. the amount of living matter present) is living matter present) is referred to as Biomass referred to as Biomass or Standing Crop.or Standing Crop.

Primary producers

Secondary consumers

Tertiary consumers / top predators

Primary consumers

OCR 7.31

Energy transfer OCR 7.30, Energy transfer OCR 7.30, 7.31, 7.377.31, 7.37

Trophic PyramidsTrophic Pyramids

Primary producerPrimary producer

(Plants)(Plants)

Primary consumer Primary consumer

(Herbivore)(Herbivore)

SecondarySecondary

consumer consumer

(Carnivore)(Carnivore)

Total biomass Total biomass

Loss of

energy

Loss of

biomass

Trophic

level 1

Trophic

level 2

Trophic

level 3

Why does each successive Why does each successive Trophic level get smaller?Trophic level get smaller?

• Energy is lost by: respiration, movement, Energy is lost by: respiration, movement, reproduction and growth.reproduction and growth.• Transfer of energy is inefficient. Not everything is Transfer of energy is inefficient. Not everything is eateneaten

at each level so some is removed by detritivores. at each level so some is removed by detritivores. The transfer of light energy to food energy is only The transfer of light energy to food energy is only 1% efficient.1% efficient.

• Not all energy can be metabolised efficiently at eachNot all energy can be metabolised efficiently at each

level and some is lost via defecation, removed by detritivores.level and some is lost via defecation, removed by detritivores.

Q) If we assume our trophic pyramid is a UK Q) If we assume our trophic pyramid is a UK woodland ecosystem (although whether woodland ecosystem (although whether there are any truly natural ones left is there are any truly natural ones left is debatable). How would the introduction of debatable). How would the introduction of mink effect it?mink effect it?Make sure you refer to the changes in terms Make sure you refer to the changes in terms of energy transfer, and work through you of energy transfer, and work through you example carefully.example carefully.

A few years ago, Animal rights protesters A few years ago, Animal rights protesters freed a large number of mink from a farm freed a large number of mink from a farm and let them run wild in the local woods. and let them run wild in the local woods. Mink are not indigenous to this country and Mink are not indigenous to this country and have no natural predators. They are have no natural predators. They are efficient killers and, like catsefficient killers and, like catsand foxes, kill instinctively whether they and foxes, kill instinctively whether they need food or not.need food or not.

The addition of mink to a The addition of mink to a woodland woodland ecosystemecosystem

Primary producerPrimary producer

(Plants)(Plants)

Primary consumer Primary consumer

(Herbivore)(Herbivore)

SecondarySecondary

consumer consumer

(Mink added)(Mink added)

Total biomass Total biomass

Loss of

energy

Loss of

biomass

The massive The massive

increase in increase in the the

number of number of

carnivores carnivores will will

lead to the lead to the

reduction in reduction in thethe

number of number of herbivoresherbivores

The addition of mink to a The addition of mink to a woodland woodland ecosystemecosystem

Primary producerPrimary producer

(Plants)(Plants)

SecondarySecondary

consumer consumer

(Mink added)(Mink added)

Total biomass Total biomass

The primary The primary consumersconsumers

will continue to will continue to decreasedecrease

and this will lead to and this will lead to anan

increaseincrease in the in the total total

biomass of the biomass of the plants.plants.

Q) Although the totalQ) Although the total

biomass of the plantsbiomass of the plants

has increased. Is thishas increased. Is this

likely to be sustainablelikely to be sustainable

and are the plants thatand are the plants that

are increasing going toare increasing going to

be beneficial to the be beneficial to the

ecosystem?ecosystem?

The addition of mink to a woodland The addition of mink to a woodland ecosystemecosystem

Total biomassTotal biomass

Mink will eventuallyMink will eventually

run out of food andrun out of food and

a) die of starvation ora) die of starvation or

b) move to another b) move to another

ecosystemecosystem

Most herbivores will

be killed

The balance of plants in the ecosystem will be The balance of plants in the ecosystem will be

irreversably altered. Pioneer species such as nettlesirreversably altered. Pioneer species such as nettles

which are usually kept down by the herbivores which are usually kept down by the herbivores

will grow shading out other less will grow shading out other less

hardy plants and saplings.hardy plants and saplings.

They will also rapidly use upThey will also rapidly use up

nutrients and minerals fromnutrients and minerals from

the soil for their growth.the soil for their growth.

Some plants will not be able to Some plants will not be able to

reproduce without the herbivoresreproduce without the herbivores

eating their seeds.eating their seeds.

What other factors will affect the What other factors will affect the Trophic Pyramid?Trophic Pyramid?

1) Fertilisers (NPK) could increase production beyond 1) Fertilisers (NPK) could increase production beyond that which the land could manage and possibly lead to that which the land could manage and possibly lead to eutrophicationeutrophication

2) Pesticides can reduce populations of organisms which could2) Pesticides can reduce populations of organisms which could

have a knock on effect throughout the systemhave a knock on effect throughout the system

3) Deforestation can have a direct adverse effect on the area3) Deforestation can have a direct adverse effect on the area

4) Artificial maintenance of the ecosystem. For example burning4) Artificial maintenance of the ecosystem. For example burning

heather to allow grouse to feed on the young shoots. heather to allow grouse to feed on the young shoots.

Productivity OCR 7.37Productivity > refers to the rate of energy production, normally on an annual basis

Primary Productivity > refers to plant productivity

Secondary Productivity > refers to that produced by animals

Gross Productivity > is the total amount of energy fixed

Net Productivity > is the amount of energy left after losses of respiration and growth are taken into account

Net Primary Productivity (NPP) is the amount of energy made available by plants to animals at the herbivore level

The nitrogen cycle

NutrienNutrient t

CyclesCycles

Gershmels Gershmels Nutrient Nutrient CyclesCycles

OCR 7.39 Gershmel’s

Nutrient Cycles

Nutrient Cycles

Gershmels nutrient cycles Gershmels nutrient cycles are a simple way of are a simple way of showing how nutrients are showing how nutrients are transferred around an transferred around an ecosystem. They can be ecosystem. They can be represented in 2 ways:represented in 2 ways:

STORESSTORES

FLOWSFLOWS

What do all these represent? Page 38

The size of the arrows and the The size of the arrows and the circles indicates the amount of circles indicates the amount of

nutrients in that store or transferred nutrients in that store or transferred in flows in the systemin flows in the system

There are 3 typestypes of store

Biomass (total mass of Biomass (total mass of

living material) living material)

Littter

Soil

Case Study Tropical Rainforest Case Study Tropical Rainforest EcosystemEcosystem

Look at the diagram below and explain :Look at the diagram below and explain :

a) How the nutrients are being cycled a) How the nutrients are being cycled

b) Why the removal of the rainforest would be so b) Why the removal of the rainforest would be so

Detrimental – human impactDetrimental – human impact

Biomass

SoilLitter

PrecipitationPrecipitation

DecomposersDecomposers

Dead matterDead matter

Removal of

minerals

Uptake by plant roots

Runoff

Leaching

Tro

pic

al ra

in f

ore

st

•biomass is main store

•rapid transfer between stores and environment

Once the vegetation is removed, nutrients are quickly removed from the system - creating

infertile conditions - even deserts

The nutrient cycle is easily disrupted here – it is a closed system

Nutrient Cycle

Human Impact: Rainforest Human Impact: Rainforest Ecosystem after deforestationEcosystem after deforestation

TreesTrees removed and logged

AshAsh

IncreasedIncreased leaching

CropCrop

IncreasedIncreased runoff

HarvestHarvest

The removal

of trees

decreases

interception and

increases

runoffDepletion ofDepletion of

nutrients in soilnutrients in soil

LitterLitter

BiomassBiomass

PrecipitationPrecipitation

Case Study Tropical Rainforest Case Study Tropical Rainforest EcosystemEcosystem

Human Impact:

1 Acre of rainforest is lost per second – 74 species areLost every day

200 million people live in rainforests

Demand for timber / cleared land

Eg 5-15% of Madagascar’s GNP is lost each year through soil erosion, flooding of rice paddies and silting of electricity turbines

Case Case Study: Study:

Temperate Temperate Deciduous Deciduous

ForestForest

Case Study Temperate Case Study Temperate Deciduous ForestDeciduous ForestExplain the Explain the

nutrient flow in a nutrient flow in a deciduous forest deciduous forest

ecosystemecosystem

OCR 7.40OCR 7.40

Case Study Temperate Deciduous Case Study Temperate Deciduous ForestForest

Litter

Precipitation Biomass

SoilRun-off

LeachingWeathering

Tem

pera

te d

eci

duou

s fo

rest

•balance between stores

•moderate transfers between stores

Case Study Temperate Deciduous Case Study Temperate Deciduous ForestForest

Why is there a large store of nutrients in the soil?

1. Slow growth in winter

2. A low density of vegetation compared with the tropical rainforest

3. Uptake of nutrients is about 25% as efficient as a tropical rainforest

Case Study Temperate Deciduous Case Study Temperate Deciduous ForestForest

Why is there a larger store of nutrients in Litter?

•Deciduous leaves are shed in winter to retain moisture, conserve nutrients, avoid damage by snow and ice, strong cold winter winds, conserve energy when the sun’s power is low.

•Decomposition is slow (by detritivores) > nutrients return to the soil

Case Study Temperate Case Study Temperate Deciduous ForestDeciduous Forest

Human Impact:Clearing for agriculture - the input of leaf fall has been

replaced by chemical and organic fertilizers

Forests are heavily managed for recreation, conservation, economic exploitation

Very few areas of natural forest remain

ConclusionConclusionYou should now be able to understand the importance of You should now be able to understand the importance of

the cycling of nutrients through the different types ofthe cycling of nutrients through the different types of

ecosystem and also the following;ecosystem and also the following;

b) How mans influence can radically alter the flows andb) How mans influence can radically alter the flows and

storesstores

c) How these different ecosystems can lead to, c) How these different ecosystems can lead to,

or rely on particular soil typesor rely on particular soil types

d) which stores dominate particular ecosystemsd) which stores dominate particular ecosystems

a) How a complex ecosystem can be understood using nutrientsa) How a complex ecosystem can be understood using nutrients

Psammosere

Macro-nutrientsCarbonOxygenHydrogenNitrogen Micro-Nutrients

MagnesiumSulphurPhosphorous

In this way they differ from energy or trophic In this way they differ from energy or trophic

cycles and pyramids where the energy arrives cycles and pyramids where the energy arrives

from the sun and is eventually lost as heatfrom the sun and is eventually lost as heat

energy into space.energy into space.

At an ecosystem level nutrient cyclingAt an ecosystem level nutrient cycling

is part of an open system.is part of an open system.

At a At a global scaleglobal scale however the nutrients are however the nutrients are

being continually cycled and recycled.being continually cycled and recycled.

Bore

al fo

rest

(ta

iga)

•litter is main store (needles)

•little transfer between stores

Temperate coniferous Temperate coniferous forestforest

A) Why is the litter store so large?A) Why is the litter store so large?

B) Why are the flows so small?B) Why are the flows so small?

C) What sort of soil would you expect here?C) What sort of soil would you expect here?