Biogeochemical Cycles
Biogeochemical cycles: how nutrients cycle through biotic and abiotic components of ecosystems involve soil, atmosphere, and organisms examples: C and N cycles
Fig. 4-28 Hydrologic cycle
Precipitation toland
Transpirationfrom plants
RunoffSurface runoff(rapid)
Evaporationfrom land Evaporation
from ocean Precipitation toocean
Ocean storage
Surfacerunoff(rapid)
Groundwater movement (slow)
Rain cloudsCondensation
Transpiration
Evaporation
PrecipitationPrecipitation
Infiltration andPercolation
4-7 Matter Cycling in Ecosystems
Water cycles chemically unchanged natural renewal of water quality human interference
1. we use of large amounts of fresh water 2. we increase runoff 3. we modify water quality 4. we are speeding the water cycle (?) by
increasing global temperatures (?)
Diffusion between atmosphere and ocean
Carbon dioxide
dissolved in ocean water
Marine food websProducers, consumers,
decomposers, detritivores
Marine sediments, includingformations with fossil fuels
Combustion of fossil fuels
incorporation into
sediments
death, sedimentation
uplifting over geologic time
sedimentation
photosynthesis
aerobic respiration
Fig. 4-29a Carbon cycle
Figure 4-29b Carbon cycle
photosynthesis aerobic respirationTerrestrial
rocks
Soil water(dissolved
carbon)
Land food websproducers, consumers,
decomposers, detritivores
Atmosphere(most carbon is in carbon dioxide)
Peat,fossil fuels
combustion of wood (for clearing land; or for fuel
sedimentation
volcanic action
death, burial, compaction over geologic timeleaching
runoff
weathering
Combustion of fossil
fuels
Biogeochemical Cycles
The carbon cycle is based on CO2 in the atmosphere CO2 in atmosphere plants make organic matter through
photosynthesis autotrophs and heterotrophs use organic
matter through respiration and release CO2
if respiration exceeds photosynthesis, CO2 increases: greenhouse effect
human interference 1. we clear trees and plants 2. we add large amounts of CO2 to atmosphere
Fig. 4-30 Human interference in C cycle
Year
1850 1900 1950 2000 20300
2
3
4
5
6
7
8
9
10
11
12
13
14
CO
2 em
issi
on
s fr
om
fo
ssil
fuel
(b
illio
n m
etri
c to
ns
of
carb
on
eq
uiv
alen
t)
1
Highprojection
Lowprojection
Fig. 4-31 Nitrogen cycle
NO3 –
in soil
Nitrogen Fixation
by industry for agriculture
Fertilizers
Food Webs On Land
NH3, NH4+
in soil
1. Nitrification
bacteria convert NH4+ to
nitrate (NO2–)
loss by leaching
uptake by autotrophs
excretion, death,
decomposition
uptake by autotrophs
Nitrogen Fixationbacteria convert N2 to
ammonia (NH3) ; this
dissolves to form ammonium
(NH4+)
loss by leaching
Ammonificationbacteria, fungi convert the
residues to NH3 , this
dissolves to form NH4+
2. Nitrification
bacteria convert NO2- to
nitrate (NO3-)
Denitrificationby bacteria
Nitrogenous Wastes, Remains In Soil
Gaseous Nitrogen (N2)
in Atmosphere
NO2 –
in soil
© 2004 Brooks/Cole – Thomson Learning
Biogeochemical Cycles
The nitrogen cycle depends largely on bacteria N2 NH3 NO2
- and NO3-
ammonia nitrite nitrate human interference
1. we add NO to the air when we burn fuel it can become NO2 and then HNO3, causing
acid rain 2. we add N2O to the atmosphere indirectly
through the action of bacteria on livestock waste and fertilizers
Biogeochemical Cycles human interference, cont.
3. we release nitrogen stored in soils and plants into atmosphere by removing trees
4. we upset aquatic ecosystems by adding excess nitrates in agricultural runoff and sewage systems
5. remove nitrogen from topsoil when harvesting, irrigating, or burn or clear grasslands or crops
6. we are affecting biodiversity
Fig. 4-32 Human interference in N cycle
1920 1940 1960 1980 2000
Glo
bal
nit
rog
en (
N)
fixa
tio
n(t
rill
ion
gra
ms)
0
50
100
150
200
Year
Nitrogen fixation by natural processes
Fig. 4-33 Phosphorus cycle
GUANO
FERTILIZER
ROCKS
LAND FOOD WEBS
DISSOLVED IN OCEAN
WATER
MARINE FOOD WEBS
MARINE SEDIMENTS
weathering
agriculture
uptake by autotrophs
death, decomposition
sedimentation settling out weathering
leaching, runoff DISSOLVED IN SOIL WATER,
LAKES, RIVERS
uptake by autotrophs
death, decomposition
miningmining
excretionexcretion
uplifting over geologic time
Biogeochemical Cycles
The phosphorus cycle does not move through the atmosphere human interference
1. we mine phosphate rock to make fertilizer 2. we reduce phosphate availability in tropics
by cutting tropical forests 3. we add phosphates to runoff and disrupt
aquatic systems
Fig. 4-34 Sulfur cycle
Sulfur
Hydrogen sulfide
Sulfate salts
Plants
Acidic fog and precipitation
Ammonium sulfate
Animals
Decaying matterMetallic
sulfide deposits
Ocean
Dimethyl sulfide
Sulfur dioxide Hydrogen sulfide
Sulfur trioxide Sulfuric acidWater
Ammonia
Oxygen
Volcano
Industries