Transcript Nutrient Cycles in Ecosystems

Nutrient Cycles in
Ecosystems
Biogeochemical Cycle
 The
flow of a nutrient from the
environment to living organisms and
back to the environment
 Main
reservoir for the nutrient is in the
environment
Main nutrient
reservoirs in the
environment
fraction of
nutrient
available to
ecosystem
geochemical cycle
primary
producers
herbivores,
carnivores,
parasites
detritivores,
decomposers
Fig. 47-14, p.852
Three Categories
 Hydrologic

cycle
Water
 Atmospheric

Nitrogen and carbon
 Sedimentary

cycles
cycles
Phosphorus and sulfur
Hydrologic Cycle
Atmosphere
wind-driven water vapor
40,000
evaporation precipitation
from ocean into ocean
425,000
385,000
precipitation
onto land
111,000
evaporation from land
plants (evapotranspiration)
71,000
surface and
groundwater
flow 40,000
Ocean
Land
Figure 47-15
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EVAPORATION
PRECIPITATION
TRANSPIRATION
interception by plants
dripping, trickling
down along stems
falling through
to ground
surface pooling, etc.
infiltration of soil
moisture in soil
overland flow
lateral flow
seepage, percolation
groundwater storage
DEEP OUTFLOW
base flow
STREAM OUTFLOW
Fig. 47-16, p.853
Water Use and Scarcity
 Most
of Earth’s water is too salty for
human consumption
 Desalinization
is expensive and
requires large energy inputs
 Irrigation
of crops is the main use of
freshwater
Fig. 47-18, p.855
Negative Effects of Irrigation
 Salinization,
 Elevation
mineral buildup in soil
of the water table and
waterlogging
 Depletion
of aquifers
Aquifer Problems
Figure 47-19
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Carbon Cycle
 Carbon
moves through the atmosphere
and food webs on its way to and from
the ocean, sediments, and rocks
 Sediments
reservoir
and rocks are the main
diffusion between
atmosphere and ocean
bicarbonate and
carbonate in
ocean water
photosynthesis
combustion of fossil fuels
aerobic
respiration
marine food
webs
death,
incorporation sedimentation
into sediments
uplifting
sedimentation
marine sediments
Carbon Cycle - Marine
Figure 47-20
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atmosphere
combustion of
fossil fuels
volcanic action
terrestrial
rocks
weathering
photosynthesis
aerobic combustion
respiration of wood
sedimentation
land food
webs
soil water
leaching,
runoff
death, burial,
compaction over
geologic time
Carbon Cycle - Land
peat,
fossil
fuels
Figure 47-20
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Carbon in the Oceans
 Most
carbon in the ocean is dissolved
carbonate and bicarbonate
 Ocean currents carry dissolved carbon
Carbon in Atmosphere
 Atmospheric
carbon is mainly carbon
dioxide
 Carbon

dioxide is added to atmosphere
Aerobic respiration, volcanic action, burning
fossil fuels
 Removed
by photosynthesis
Nitrogen Cycle
 Nitrogen
is used in amino acids and
nucleic acids
 Main
reservoir is nitrogen gas in the
atmosphere
Nitrogen Cycle
gaseous nitrogen (N2)
in atmosphere
nitrogen fixation
by industry
food webs
on land
uptake by excretion, death, uptake by
fertilizers autotrophs decomposition autotrophs
nitrogen
fixation
NH3-,NH4+
in soil
leaching
nitrogenous
wastes, remains
NO3in soil
dentrification
ammonification 2. Nitrification
1. Nitrification
NO2in soil
leaching
Figure 47-25
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Nitrogen Fixation
 Plants
cannot use nitrogen gas
 Nitrogen-fixing
bacteria convert
nitrogen gas into ammonia (NH3)
 Ammonia
and ammonium can be
taken up by plants
Ammonification & Nitrification
 Bacteria
and fungi carry out
ammonification

conversion of nitrogenous wastes to ammonia
 Nitrifying
bacteria convert ammonium to
nitrites and nitrates
Nitrogen Loss
 Nitrogen
is often a limiting factor in
ecosystems
 Nitrogen
is lost from soils via leaching and
runoff
 Denitrifying
bacteria convert nitrates and
nitrites to nitrogen gas
Human Effects
 Humans
increase rate of nitrogen loss by
clearing forests and grasslands
 Humans
increase nitrogen in water and air
by using fertilizers and by burning fossil
fuels
 Too
much or too little nitrogen can
compromise plant health
mining
fertilizer
guano
excretion
uptake by agriculture
autotrophs
uptake by weathering
producers
marine
food webs
dissolved
in seawater
leaching, runoff
death,
decomposition
sedimentation
land food
webs
death,
decomposition
settling out
marine sediments
dissolved in
soil water,
lakes, rivers
weathering
uplifting over
geologic time
terrestrial rocks
Phosphorus cycle
Fig. 47-27, p.862
Phosphorus Cycle
 Phosphorus
is part of phospholipids and
all nucleotides
 It
is the most prevalent limiting factor in
ecosystems
 Main
reservoir is Earth’s crust; no
gaseous phase
Phosphorus Cycle
mining
FERTILIZER
GUANO
excretion
agriculture
uptake
by
autotrophs
MARINE
FOOD
WEBS
weathering
DISSOLVED
IN OCEAN
WATER
uptake
by
autotrophs
weathering
DISSOLVED IN
SOILWATER,
LAKES, RIVERS
death,
decomposition
sedimentation
LAND
FOOD
WEBS
death,
decomposition
settling
out
leaching, runoff
uplifting
TERRESTRIAL ROCKS
MARINE SEDIMENTS
over geologic time
Figure 47-27, Page 862
Human Effects
 In
tropical countries, clearing lands for
agriculture may deplete phosphoruspoor soils
 In
developed countries, phosphorus
runoff is causing eutrophication of
waterways