EcosystemsEcosystems

Biogeochemical CyclesBiogeochemical Cycles

KEY CONCEPT 1KEY CONCEPT 1Ecosystems consist of nonliving (abiotic) Ecosystems consist of nonliving (abiotic)

and living (biotic) components.and living (biotic) components.

KEY CONCEPT 2KEY CONCEPT 2

An ecosystem An ecosystem survives by a survives by a combination of combination of energy flow and energy flow and matter recycling.matter recycling.

KEY CONCEPT 3KEY CONCEPT 3Earth is a Closed System!Earth is a Closed System!

Biosphere

Carboncycle

Phosphoruscycle

Nitrogencycle

Watercycle

Oxygencycle

Heat in the environment

Heat Heat Heat

BIOGEOCHEMICAL CYCLES: ABIOTIC CYCLESBIOGEOCHEMICAL CYCLES: ABIOTIC CYCLES

GLOBAL RECYLING - A GLOBAL RECYLING - A closed pathway closed pathway where matter cycles where matter cycles from the from the nonlivingnonliving environment to environment to livingliving and then and then back back again again for for reusereuse..

Key feature- nutrients recycle through the earth’s air, land, Key feature- nutrients recycle through the earth’s air, land, water, and living organisms. water, and living organisms.

Nutrients are the elements and compounds that Nutrients are the elements and compounds that organisms need to live, grow, and reproduce.organisms need to live, grow, and reproduce.

The overall The overall rate rate of nutrient movement is limited most by of nutrient movement is limited most by decompositiondecomposition. .

The rate of nutrient loss is a key characteristic in any The rate of nutrient loss is a key characteristic in any ecosystem. ecosystem.

Assim

ilati

on

Loss to erosion or leaching into groundwater

Soil nutrient pool

Decomposerfood web

Detritus

Death

Herbivore

Uptake

Plants

Feces or urine

Overview of Nutrient CyclingOverview of Nutrient Cycling

PrecipitationPrecipitation

Transpiration

Condensation

Evaporation

Ocean storage

Transpiration from plants

Precipitation to land

Groundwater movement (slow)

Evaporation from land Evaporation

from ocean Precipitation to ocean

Infiltration and Percolation

Rain clouds

RunoffSurface runoff

(rapid)

Surface runoff (rapid)

Water CycleWater Cycle

Water CycleWater Cycle Causes wind currentsCauses wind currents There are strong forces of There are strong forces of

attraction between attraction between molecules of water.molecules of water.

Water exists as a liquid over Water exists as a liquid over a wide temperature range. a wide temperature range.

Liquid water changes Liquid water changes temperature slowly.temperature slowly.

It takes a large amount of It takes a large amount of energy for water to energy for water to evaporate.evaporate.

Liquid water can dissolve a Liquid water can dissolve a variety of compounds.variety of compounds.

Water expands when it Water expands when it freezes.freezes.

Water has greatest influence of all non-living components

Effects of Human Activities Effects of Human Activities on Water Cycleon Water CycleWe alter the water cycle We alter the water cycle

by:by:Withdrawing large Withdrawing large

amounts of freshwater.amounts of freshwater.Clearing vegetation and Clearing vegetation and

eroding soils.eroding soils.Polluting surface and Polluting surface and

underground water.underground water.Contributing to climate Contributing to climate

change.change.

Carbon CycleCarbon Cycle Erosion:Erosion:

CaCOCaCO3 3 shells shells limestone limestone

Combustion:Combustion:

Burning- COBurning- CO22

Fossil fuels –hydrocarbonsFossil fuels –hydrocarbons

Volcanic ActionVolcanic Action

Forest FiresForest Fires

Photosynthesis and Photosynthesis and Cellular respiration:Cellular respiration:

OO22 CO CO22

Effects of Human Activities Effects of Human Activities on Carbon Cycleon Carbon Cycle

We alter the carbon We alter the carbon cycle by adding cycle by adding excess COexcess CO22 to the to the atmosphere atmosphere through:through:Burning fossil fuels.Burning fossil fuels.Clearing vegetation Clearing vegetation

faster than it is faster than it is replaced.replaced.

Figure 3-28Figure 3-28

Greenhouse gasesGreenhouse gases

Nitrous oxideNitrous oxide

WaterWater

Carbon dioxideCarbon dioxide MethaneMethane

Sulfur hexafluorideSulfur hexafluoride

1414

Most Important Greenhouse GasesMost Important Greenhouse Gases

Source: U.S. EPA 2005

GHGs Source ExamplesWater: H2O Oceans, rivers, plants, soil

Carbon Dioxide: CO2 Combustion of fossil fuels, plant respiration, oceans, volcanoes

Methane: CH4 Mining operations, combustion, animals, wetlands, landfills

Other GHGsOther GHGs : Nitrous oxide (N : Nitrous oxide (N22O), Ozone (near surface), O), Ozone (near surface),

Learn more about GHGs: http://www.epa.gov/climatechange/emissions/index.html

http://www.for.gov.bc.ca

Nitrogen CycleNitrogen Cycle Availability of Nitrogen is a Availability of Nitrogen is a limiting factor for primary limiting factor for primary productivityproductivity78% N gas in atmosphere 78% N gas in atmosphere

unusableunusable

Nitrogen CycleNitrogen Cycle

AssimilationAssimilation Absorption and Absorption and

incorporation of nitrogen incorporation of nitrogen by plantsby plants

AmmonificationAmmonification

Decomposition by bacteria Decomposition by bacteria during decayduring decay

DenitrificationDenitrification

Denitrifying bacteria Denitrifying bacteria convert nitrates back into Nconvert nitrates back into N22

Bacteria can “fix nitrogen” which means they break apart nitrogen gas and convert it into ammonia or ammonium.

NitrificationNitrification

Ammonia to nitrates and Ammonia to nitrates and nitrites by bacterianitrites by bacteria

Then can be assimilated Then can be assimilated by plantsby plants

These nodules are These nodules are called called rhyzomesrhyzomes. . They are where the They are where the nitrifying bacteria nitrifying bacteria reside. They have a reside. They have a symbiotic relationship symbiotic relationship with the plantwith the plant

Effects of Human Activities Effects of Human Activities on the Nitrogen Cycleon the Nitrogen Cycle

We alter the nitrogen cycle by:We alter the nitrogen cycle by:Adding gases that contribute to Adding gases that contribute to

acid rain.acid rain.Adding nitrous oxide to the Adding nitrous oxide to the

atmosphere through farming atmosphere through farming practices which can warm the practices which can warm the atmosphere and deplete ozone.atmosphere and deplete ozone.

Contaminating ground water from Contaminating ground water from nitrate ions in inorganic fertilizers.nitrate ions in inorganic fertilizers.

Releasing nitrogen into the Releasing nitrogen into the troposphere through troposphere through deforestation.deforestation.

Effects of Human Activities Effects of Human Activities on the Nitrogen Cycleon the Nitrogen Cycle

Human activities Human activities such as such as production of production of fertilizers now fix fertilizers now fix more nitrogen more nitrogen than all natural than all natural sources sources combined.combined.

Phosphorous CyclePhosphorous Cycle No gaseous component No gaseous component (from land to sediment (from land to sediment and back to land only)and back to land only)

Erosion Erosion releases releases phosphatephosphate soil soil plantsplants

Decomposers Decomposers phosphate phosphate soil soil

Deposited in oceanic Deposited in oceanic sediment sediment unavailable unavailable for yearsfor years

Fertilizers, run off Fertilizers, run off containing animal containing animal wastes, and sewage wastes, and sewage aquatic ecosystemsaquatic ecosystems

The Phosphorous CycleThe Phosphorous Cycle

Effects of Human Activities Effects of Human Activities on the Phosphorous Cycleon the Phosphorous CycleWe remove large amounts of We remove large amounts of

phosphate from the earth to phosphate from the earth to make fertilizer.make fertilizer.

We reduce phosphorous in We reduce phosphorous in tropical soils by clearing tropical soils by clearing forests.forests.

We add excess phosphates to We add excess phosphates to aquatic systems from runoff aquatic systems from runoff of animal wastes and of animal wastes and fertilizers.fertilizers.

The Sulfur CycleThe Sulfur Cycle

Effects of Human Activities Effects of Human Activities on the Sulfur Cycleon the Sulfur CycleWe add sulfur dioxide to We add sulfur dioxide to

the atmosphere by:the atmosphere by: Burning coal and oilBurning coal and oil Refining sulfur containing Refining sulfur containing

petroleum.petroleum. Converting sulfur-containing Converting sulfur-containing

metallic ores into free metals metallic ores into free metals such as copper, lead, and zinc such as copper, lead, and zinc releasing sulfur dioxide into releasing sulfur dioxide into the environment.the environment.

Acid PrecipitationAcid Precipitation

• Rain, snow or fog that Rain, snow or fog that has a pH value of less has a pH value of less than 5.6 because of the than 5.6 because of the carbon dioxide from carbon dioxide from air dissolved in itair dissolved in it

• Any rainfall has a Any rainfall has a pHpH value value less thanless than 5.65.6 is is defined as defined as acid rainacid rain

• When gas pollutants e.g. When gas pollutants e.g. sulfur dioxidesulfur dioxide, , nitrogen dioxidenitrogen dioxide dissolve in rain water, dissolve in rain water, various acids are formed.various acids are formed.

CO2 + H2O H2CO3 (carbonic acid)SO2 + H2O H2SO3 (sulphorous acid)NO2 + H2O HNO2 (nitrous acid) +

HNO3 (nitric acid)

Acid PrecipitationAcid Precipitation

CAUSES OF ACID RAINCAUSES OF ACID RAIN

SO2 : 70% NOx : 30%X = 1 or 2