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