Area IIE: The Living World

Natural Biogeochemical Cycles

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 (?)

Water cycle

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

Carbon cycle

Carbon cycle

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

Nitrogen cycle

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

Phosphorus cycle

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

Biogeochemical Cycles

The sulfur cycle human interference

we add sulfur dioxide (SO2) to the atmosphere by:

1. burning coal and oil to generate electricity 2. refining oil to make gasoline and other

petroleum products 3. converting sulfur-containing ores into free

metals