Institute of Food and Agricultural Sciences (IFAS ... · Si dA li ti Institute of Food and...

1

Biogeochemistry of WetlandsS i d A li tiS i d A li ti

Institute of Food and Agricultural Sciences (IFAS)

Science and ApplicationsScience and Applications

Wetland Biogeochemistry LaboratorySoil and Water Science Department

Carbon Cycling Processes Carbon Cycling Processes

6/22/2008 16/22/2008 WBL 1

InstructorK. Ramesh [email protected]

Soil and Water Science DepartmentUniversity of Florida

Institute of Food and Agricultural Sciences (IFAS)


CO2 OM

6/22/2008 WBL 2

CH4

2

L t O tli


Lecture Outline

IntroductionMajor components of carbon cycle Organic matter accumulationCharacteristics of organic matterDecomposition processes

6/22/2008 WBL 3

Regulators of organic matter decompositionGreenhouse gasesSummary

Learning Objectives


Learning ObjectivesDescribe major components of carbon cycleDevelop an understanding of the chemical composition of plant litter

and soil organic matterLong-term accumulation of organic matterDescribe the role of enzymes and microbial communities involved in

decomposition Determine organic matter turnover

6/22/2008 WBL 4

Determine organic matter turnover Indentify the role biogeochemical controls and regulatorsUnderstand the global significance of carbon cycleDraw a carbon cycle and identify storages and fluxes within and

between soil and water column

3

Oxidation States of CarbonOxidation States of Carbon[+4] [0]CO2 C6H12O6

[ ]

[-4]

[0]

6/22/2008 WBL 5

CH4

Carbon ReservoirsCarbon Reservoirs[10[101414 kg]kg]

Atmospheric CO2 7Biomass 4.8Fresh water 2.5Marine 5-8

6/22/2008 WBL 6

Soil organic matter 30-50

4

Soil Organic Matter [SOM]Undecayed plant and animal tissues

Partially decomposed material

Soil biomass

Sources of SOM External: Particulate (inputs)

6/22/2008 7

External: Particulate (inputs)

Internal: detrital material (macrophytes, algal mats, roots)

WBL

Detrital Plant Biomass

Aerobic

Grazers

microorganismsCO2

Detritus

Peat

Anaerobic

Decomposition

BurialWat

er ta

ble

6/22/2008 8

Compaction

WBL

5

Carbon Cycle Carbon Cycle

CO

UV

Litter Microbialbiomass

DOC HCO3-

CO2CO2

Decomposition/leaching


CH4

Import Export

6/22/2008 WBL 9

Peat Microbialbiomass

DOC HCO3-

CH4


Decompositionleaching

Storages Outputs

Organic Matter

StoragesSoil organic matterPlant detritus/litterDissolved organic matterMicrobial biomass

TransformationsMicrobial respirationM th i

OutputsGreenhouse gasesNutrient export

Ecological/Environmental Significance

Carbon sequestrationGlobal warming

6/22/2008 WBL 10

Methanogenesis Global warmingWater qualityEcosystem productivity

6

Net Primary Productivity[g/m2 - year]

Bog 380-800

[Craft, 2001]

Bog 380-800Marsh 500 -1100Riverine 400-1150Fresh tidal 500-1600Brackish 600-1600

6/22/2008 WBL 11

Salt 950-2000Mangroves 600-1200

Carbon Accumulation in Wetlands

[g C/m2 year]Alaska - Sphagnum 11-61Finland - Sphagnum - Carex 20-28Ontario - Sphagnum bog 30-32Georgia Taxodium 23

6/22/2008 WBL 12

Georgia - Taxodium 23 Florida - Cladium 70-105

7

Organic matter

0Organic Matter Accumulation

1964marker

gaccumulation

Soil

Dep

th [c

m]

10

6/22/2008 WBL 13

Cs-137 Activity

20

A. Detritus attachedto plant

B. Detritus detachedfrom plant

detritusWater

Soil

from plant

C. Decomposeddetritus fromprevious year

D. Organic matter

6/22/2008 WBL 14

Soil D. Organic matterand nutrientaccretion

PlantDetritus

Soil OrganicMatterA B C

Decay continuum

8

Live plant

Decay ContinuumDecay Continuum

CO CHPlant standing dead

Litter layer

CO2 CH4

6/22/2008 WBL 15

Surface peat

Buried peat

Microbialdecomposers

Carbon Accumulation in Wetlands

Potential energy source (reduced carbon, electron donor

Long-term storage of nutrients, heavy metals, and toxic organic compounds

6/22/2008 WBL 16

, g pMajor component of global carbon

cycles

9

Carbon FormsCarbon FormsParticulate organic carbon (POC)g ( )Microbial biomass carbon (MBC)Dissolved organic carbon (DOC) Dissolved inorganic carbon (DIC)

CO2 + H2O = H2CO3

6/22/2008 WBL 17

2 2 2 3

H2CO3 = HCO3- + H+

HCO3- = CO3

2- + H+

Non Humic compounds:Carbohydrates (Simple sugars)

Chemical constituents of organic matter

Carbohydrates (Simple sugars)Monosaccharides: glucose.Polysaccharides: Starch, Cellulose, and Hemicellulose

ProteinsLipids etc

Phenolic compounds:Li i (b h d d l f h l id i )

6/22/2008 18

Lignin (branched random polymer of phenyl propanoid unit)Tannins (heterogeneous groups of phenolic compounds)

WBL

10

Organic Matter (Plant and Soil)• Water soluble components [<10%]

Sugars amino acids and fatty acids– Sugars, amino acids and fatty acids• Cellulose [15-60%]• Hemicellulose [10-30%]• Lignin [5-30%]• Proteins [2-15%]

6/22/2008 WBL 19

• Lipids and Waxes [1-8%]• Ash (mineral) [1-13%]

β-D-glucosidic bond

Cellulose

OH

OH

OH

H

H HHO

CH2OH

H

OHH

HH

OO

CH2OH

H

OH

HH

HO

6/22/2008 20

CH2OHOHH OHH

WBL

11

Lignin

6/22/2008 21WBL

Soil Organic Matter [SOM]

SOMSOMSOMSOM

Extract with Alkali

HuminHumin[alkali-insoluble]

[alkali-soluble]

Treat with Acid

6/22/2008 WBL 22

Humic AcidHumic Acid[acid-insoluble]

Fulvic AcidFulvic Acid[acid-soluble]

12

FulvicFulvic AcidAcid

• More ‘O’ and less ‘C’• More O and less C .• MW 1000 -30,000.• Less advanced stage of decomposition.• More COOH group per unit mass.• Functional group acidity (11 2 mol/kg)

6/22/2008 WBL 23

• Functional group acidity (11.2 mol/kg).• Alkali and acid soluble.

HumicHumic AcidAcid

• More ‘C’ and less ‘O’• More C and less O .• MW 10,000 -100,000.• Advanced stage of decomposition.• Less COOH group per unit mass.• Functional group acidity (6.7 mol/kg).

6/22/2008 WBL 24

• Alkali soluble.

13

Available Carbon PoolAvailable Carbon PoolRepresents small but biologically active fraction of DOCfraction of DOCImmediately available for microbial utilizationExtremely small in C-limited systemRapid turnover

6/22/2008 WBL 25

May not be directly measurableAffects short-term community metabolism

Microbial BiomassMicrobial Biomass

6/22/2008 WBL 26

14

MicroorganismsMicroorganisms[Percent wet weight][Percent wet weight]

• 70% water Total weight of• 70% water• Macromolecules

• 15% protein• 3% polysaccharide• 2% lipids• 5% RNA

Total weight of actively growing cell of Escherichia coli

Wet wt = 9.5 x 10-13 gD t 2 8 10 13

6/22/2008 WBL 27

• 5% RNA• 1 % DNA

• 1 % Inorganic ions• 3 % others

Dry wt = 2.8 x 10-13 g

Microbial DecomposersMicrobial DecomposersTypically 1-5% of total C mass in soilP t f th t tProcess most of the ecosystem net productionPrincipal transformers of organic carbonRecycle carbon and nutrients in recalcitrant biopolymers

6/22/2008 WBL 28

recalcitrant biopolymersRegulate energy flow and nutrient retention

15

Techniques to Measure Techniques to Measure MICROBIAL BIOMASS MICROBIAL BIOMASS

Di t ll t b dDirect cell count : abundance

Lipid based : live microbial biomass

CHCl3 Fumigation-extraction based: estimate of Carbon

6/22/2008 WBL 29

Metabolic activity based: Enzyme activities

MICROBIAL COMMUNITY STRUCTUREMICROBIAL COMMUNITY STRUCTURE

Pure culture approach

Microscopy py

Community level physiological profile (CLPP): Substrate utilization: BIOLOG

Measurement of cellular component (physiological status, functional groups):PLFA

Methods based on nucleic acids analysis (abundance

6/22/2008 30

Methods based on nucleic acids analysis (abundance, diversity and phylogeny of organisms): gene specific analysis (16S rDNA, DGGE, TGGE, Trflp)

WBL

16

910

MICROBIAL BIOMASSMICROBIAL BIOMASS[Site = WCA-2A - Everglades]

345678

LITTER

0-10 cm

10-30 cm

6/22/2008 WBL 31

012

0 2 4 6 8 10

Distance from Inflow, km

Eutrophic Oligotrophic

MICROBIAL NUMBERS [MPN/g soil][Site = WCA-2A - Everglades]

SubstrateLactate 9.3 x 105 9.2 x 103

Acetate 2.3 x 105 3.6 x 103

Propionate 4.3 x 105 9.2 x 103

Butyrate 4 3 x 105 < 3 0 x 103

6/22/2008 WBL 32

Butyrate 4.3 x 105 < 3.0 x 103

Formate 2.3 x 105 < 3.0 x 103

Hector et al. 2003

17

DetritalDetrital MatterMatter

Complex PolymersComplex Polymers

Leaching

Complex PolymersComplex PolymersCellulose; Hemicellulose; Lignin

Proteins; Lipids and waxes

End product

6/22/2008 WBL 33

MonomersMonomersSugars;Amino acids

Fatty acids

End products+ energy

Bacterial Cell

Electron acceptors

Extracellular Extracellular EnzymesEnzymes

6/22/2008 WBL 34

18

Extracellular Enzymes• An extracellular enzyme is involved in transformation or degradation of polymeric substances external to cell membrane– Enzyme can be bound to the

cell membrane or are periplasmic (ectoenzyme)(Chrost,1990)

– Enzyme occurs free in the water or adsorbed to surface other than its producers e.g.,

membrane.

Bacterial cellPeriplasmic space

6/22/2008 WBL 35

detrital particles or clay material (extracellular enzyme)

•Most of these are hydrolases

Detrital/clay material

EnzymesEnzymes• Cellulose degradation

– Exocellulase - Cellulose– B-glucosidase - Cellobiose

• Hemicellulose degradation– Exoxylanase - Xylan– B-xylosidase - Xylobiose

6/22/2008 WBL 36

• Lignin degradation– Phenol oxidase - Lignin and Phenols

19

Enzyme Enzyme –– Catalyzed ReactionCatalyzed Reaction

E E SS EE + P+ P

S = Substrate E = Enzyme P = Product

EE + S+ S

6/22/2008 WBL 37

All enzymes are proteins – amino acid polymers

Reactions of EnzymesReactions of EnzymesR-O-PO32- + H2O R-OH + HO-PO3

2-

alkaline phosphatase

casein + H O tyrosine

R-O-SO3- + H2O R-OH + H+ + SO4

2-

arylsulfatase

R-O-glucose + H2O R-OH + glucoseβ-glucosidase

6/22/2008 WBL 38

phenolics + O2 quinones

casein + H2O tyrosine

phenol oxidase

protease

20

Humic acid

E

Humic acid-Enzyme complex

Active Enzyme

Inhibition of enzyme activity

Ca2+

+ ECa2+

Ca2+ Ca2+

Ca2+

E+

E+ E

6/22/2008 39

+ E Ca2+

Ca2+Ca2+

Ca2+

E+

WBL

• Spectroscopic i h l h h ( NPP)

Measurement of EnzymesMeasurement of Enzymes

– p-nitrophenol phosphate (pNPP)

• Fluorescence– Methylumbelliferyl phosphate (MUF)– Enzyme Labeled Fluorescence (ELF)

APaseAPase

6/22/2008 WBL 40

P PAPaseAPase

MUF-P MUF Pi

21

h-1

β β GlucosidaseGlucosidase ActivityActivity

g p-

nitro

phen

ol g

-1 h

0

50

100

6/22/2008 WBL 41

Oxygen Nitrate Sulfate BicarbonateE h (mV) 618 214 -145 -217

pH 4.5 7.6 7.5 6.5

ugvi

ty1

h-1) 2

4

Februaryimpactedtransitionalunimpacted

[Everglades [Everglades --WCAWCA--2A]2A]β β GlucosidaseGlucosidase ActivityActivity

D-G

luco

sida

se A

ctiv

g p-

nitr

ophe

nol g

-1

0

0

2

4May

4A t

6/22/2008 WBL 42

B-D (m

g

0

2

Detritus 0-10 cm 10-30 cm

August

Wright and Reddy, 2001

22

May45

ty -1)

PhenoPheno oxidaseoxidase ActivityActivity[Everglades [Everglades --WCAWCA--2A]2A]

Wright and Reddy, 2001

y

0123

345 August

nol O

xida

se A

ctiv

itol

e [D

QC

]g-1

min

-

impactedtransitionalunimpacted

6/22/2008 WBL 43

0123

Detritus 0-10 cm 10-30 cm

Phen

(um

o p

DQC = dihydroindole quinone carboxylate

Microbial ActivityMicrobial ActivityMicrobial ActivityMicrobial Activity

6/22/2008 WBL 44

23

DetritalDetrital MatterMatter

Complex PolymersComplex Polymers

Leaching

Complex PolymersComplex PolymersCellulose; Hemicellulose; Lignin

Proteins; Lipids and waxes

Reduced product

6/22/2008 WBL 45

MonomersMonomersSugars;Amino acids

Fatty acids

End products+ energy

Bacterial Cell

Electron acceptors

Organic Matter Decomposition

IL D

EPTH

6/22/2008 46

Decreasing energy

yield

SO

WBL

24

Metabolism• Catabolism• Anabolism• Types of energy source

• Light … Phototrophs• Inorganic … Lithotrophs• Organic …. Heterotrophs

6/22/2008 WBL 47

• Oxidation of organic compounds• Fermentation• Respiration

ChemolithotrophyInorganic compound as energy source

eg H S Hydrogen gas Fe(II) and NHeg. H2S, Hydrogen gas, Fe(II), and NH3

Source of carbon for biosynthesis cannot be organic therefore use CO2 and hence are autotrophs

Hydrogen oxidationSulfur oxidationFerrous iron oxidation

6/22/2008 48

AnnamoxNitrification

WBL

25

Phototrophy• Photosynthesis is conversion of light energy into

chemical energy.• Most phototrophs are autotrophs ( use CO2 as sole

Carbon source).

ADPCarbon

CO2H2SADP

Carbon CO2

H2O

hυ

OXYGENIC PHOTOTROPHS ANOXYGENIC PHOTOTROPHS

6/22/2008 WBL 49

ATP(CH2O)nSO42-

S0hυ

ATP(CH2O)n1/2O2

hυ

Energy sources:Organic inorganic

Waste products:O i i i

Catabolism

Metabolism

Organic, inorganic, light

Organic, inorganic

Cell biomass

6/22/2008 50

Anabolism

Nutrients:N, P, K, S, Fe,

Mg, ...

Carbon sources:Organic, CO2

WBL

26

Pathways for Oxidation of Organic Compounds

RESPIRATION: Molecular oxygen (aerobic) or other oxidant(Anaerobic) serves as external electron acceptor

FERMENTATION R d i h b fFERMENTATION: Redox processes occur in the absence of any external electron acceptor

Glucose reductant

TER

IA

oxidation Reduction

CO2, NO2-,

Fe(II), H2SO

6/22/2008 51

CO2 + H2oxidant

BA

CT

O2, NO3-,

Fe(III), SO4

WBL

MetabolismAssimilative metabolism (biomass)

bacteria(biomass)

Dissimilative Metabolism

(energy )

Respiration Fermentation

6/22/2008 WBL 52

Aerobic (Oxygen as

electron acceptor)

Anaerobic ( Inorganic, metal as electron acceptors)

AnaerobicOrganic compounds as electron acceptors

High energy yield Low energy yield

27

Detrital MatterEnzymeHydrolysisComplex Polymers

Cellulose, Hemicellulose,P t i Li id W Li i

MonomersSugars, Amino Acids

Fatty Acids

Aerobic RespirationAerobic Respiration

Glucose PyruvateGlycolysis

Substrate level phosphorylation

TCA Cycle

Proteins, Lipids, Waxes, Lignin Fatty Acids

Uptake

Bacterial Cell

6/22/2008 53

TCA Cycle

Oxidative phosphorylation

CO2

ATP

Acetyl Co A

O2 + e -

H2O

CO2

O2

WBL


Fatty Acids

Uptake

Nitrate RespirationNitrate Respiration

Products:CO2, H2O, N2, N2O, nutrients

Glucose

PyruvateGlycolysis

Substrate level phosphorylation Acetate

TCA Cycle

CO2

NO3- + e- Organic Acids

[acetate, propionate, butyrate, lactate, alcohols, H2, and CO2]

LactateUptake

6/22/2008 54

ATP2 2

Nitrate Reducing Bacterial Cell Fermenting Bacterial Cell

Terminal reductase enzyme (nitrous oxide reductase)

NO3-

WBL

28


Fatty Acids

Uptake

Iron RespirationIron Respiration

Products:CO2, H2O,

Fe2+, nutrients

Glucose

PyruvateGlycolysis


TCA Cycle

CO2

Fe3+ + e- Organic Acids[acetate, propionate, butyrate, lactate, alcohols, H2, and CO2]

LactateUptake

6/22/2008 55

ATP2 2

Iron Reducing Bacterial Cell Fermenting Bacterial Cell

Terminal reductase enzyme (ferric reductase)

Fe3+

WBL

Organic compound

Oxidation

Bacterial Cell

FermentationFermentation

OxidizedOrganic compounds[Pyruvate]

R d d

Electron carriers

Oxidation

Reduction

ReducedOrganic compounds[Ethanol]

6/22/2008 56WBL

29


Fatty Acids

Uptake

Sulfate Respiration

Glucose

PyruvateGlycolysis


TCA CycleOxidative phosphorylation

CO2

SO42- + e- Organic Acids

[acetate, propionate, butyrate, LactateUptake

Prod

ucts

:H

2O, S

2-, n

utrie

nts

6/22/2008 57

ATPlactate, alcohols, H2, and CO2]

LactateSubstrate level phosphorylation

Sulfate Reducing Bacterial Cell Fermenting Bacterial Cell

CO

2, H

SO42-

WBL

Methanogens

Archaea not bacteriaArchaea…not bacteria

H2 is electron donor and CO2 is electron acceptor and reduced to CH4 (autotrophic, chemolithotrophy) -131kJ/molRespiration, not fermentationSome other substrates that can yield electrons are:y

HydrogenmethanolFormate

6/22/2008 58WBL

30

Methanogens

Hydrogenotrophic methanogens: use HHydrogenotrophic methanogens: use H2(as electron donor) and CO2

Acetotrophic methanogens: oxidation of acetate results in CO2 and CH4.

6/22/2008 59WBL


Fatty Acids

UptakeFermenting Bacteria

Methanogenesis

Glucose

Pyruvate

Glycolysis

Substrate level phosphorylation

Organic Acids[acetate propionate butyrate

LactateSubstrate level phosphorylation

AcetateH2H+

CO2 + H2CH4Oxidative phosphorylation

CO2 + H2AcetateAcetogenesis

[Acetogens]

Prod

ucts

:C

O2,

H2O

, CH

4, nu

trie

nts

[Hydrogenotrophic methanogens]

[Acetotrophic methanogens]

AcetateCO2 + CH4

6/22/2008 WBL 60

[acetate, propionate, butyrate, lactate, alcohols]

Fermenting Bacteria

H2 + CH3-OHCH4H2

H2

[Methyl substrate utilizers]

CO2

31

Inorganic Terminal Electron AcceptorsHeavy metals as electron acceptors e.g.

Ch t C (VI) Ch i C (III)

Other Terminal Electron Acceptors

• Chromate Cr(VI) Chromium Cr(III)• Arsenate (AsO4

3-) Arsenite (AsO33-)

• Selenate (SeO42-) Selenite (SeO3

2-) inorg. Se

Organic Terminal Electron AcceptorsFumarate succinateTrimethyl amine oxide (TMAO) trimethlamine(TMA)

6/22/2008 61

Trimethyl amine oxide (TMAO) trimethlamine(TMA)Dimethyl sulfoxide (DMSO) Dimethyl sulfide Reductive dechlorination

WBL

2.0

1.61.8

ATIO

N

1 )

EVERGLADES - WCA-2A

0 40.6 0.8 1.0 1.2 1.4 1.6

OB

IC R

ESP

IRA

mg

CO

2-C

g-1

d-1

6/22/2008 WBL 62

0.0 0.2 0.4

0 5 10 15 20 25 30 35 40

MICROBIAL BIOMASS C (mg g-1)

AE

RO

(m

32

600700

tion,

ImpactedEverglades, FLEverglades FL

Unimpacted

Aerobic Respiration

100

200

300

400

500

600

xyge

n co

nsum

ptm

g/kg

day

y=-1036+200 ln(x)R2=0.84

g

Houghton Lakemarsh, MI

Everglades, FL

Salt marsh, LA

Lake Apopka marsh, FLPrairie pothole, ND

l

Talladega, AL

Belhaven, NC

6/22/2008 WBL 63

0 500 1,000 1,500 2,000 2,500 3,0000

Dissolved organic C, mg/kg

Ox p ,

Crowley, LA3,500

50

60

n,

y

ImpactedEverglades, FL

Houghton Lakemarsh, MI

Nitrate RespirationNitrate Respiration

10

20

30

40

Den

itrifi

catio

mg

N/k

g d

a y

y=-64+14 ln(x)R2=0.91

Talladega, AL

Salt marsh, LA

Lake Apopka marsh, FL

Prairie pothole, ND

Crowley, LA

UnimpactedEverglades, FL

Belhaven, NC

6/22/2008 WBL 64

0 500 1,000 1,500 2,000 2,500 3,000 3,5000

Dissolved organic C, mg/kg

Crowley, LA

33

50

60

DenitrifyingDenitrifying Sulfate reducingSulfate reducingfate

ions

Microbial Respiration[Everglades Soils]

20

30

40

y gy g

Den

itrify

ing/

Sulf

educ

ing

cond

iti[m

g kg

[mg

kg--11

hour

hour

--11]]

y = 0.41x + 1.1r2 = 0.89; n = 24

y = 0.33x + 1.3r2 = 0.88; n = 24

6/22/2008 WBL 65

0

10

10 20 30 40 50 60

D re

Aerobic [mg kg[mg kg--11 hourhour--11]]

tions

y = 0 13x + 0 3

10

Microbial Respiration[Everglades Soils]

anog

enic

con

dit

[mg

kg[m

g kg

--11ho

urho

ur--11

]]

y = 0.13x + 0.3r2 = 0.85, n = 24

y 0 08x 0 22

4

6

8 CO2

6/22/2008 WBL 66

Met

ha y = 0.08x - 0.2r2 = 0.70, n = 24

0

2

10 20 30 40 50 60Aerobic, , [mg kg[mg kg--11 hourhour--11]]

CH4

34

L

LL

L

A

0.5

0.6

0.7PI

RAT

ION

d)

Anaerobic Anaerobic vsvs Aerobic RespirationAerobic Respiration

L

L

L

L

L

LA

A

A

A

A

0.2

0.3

0.4

0.5

ER

OB

IC R

ESP

(mg

C/g

d

0 324 + 0 02

6/22/2008 WBL 67

A AA

AA

SSSSS

SSS

SS0

0.1

0 0.5 1.0 1.5 2.0

AN

AE

AEROBIC RESPIRATION (mg C/g d)

y = 0.324x + 0.02r2 = 0.94

RegulatorsRegulatorsRegulatorsRegulators

6/22/2008 WBL 68

35

Regulators of Organic MatterDecomposition

Substrate qualitySubstrate qualitycarbon to nitrogen ratio or carbon to

phosphorus ratio of the substrateTemperatureAvailability of electron acceptors

6/22/2008 WBL 69

Availability of electron acceptorsMicrobial populations

PlantN and P

CO2CH

Death/senescence

Flux

Regulators of Organic MatterDecomposition and Nutrient Release

Soil Organic MatterAccumulationN and P

BioavailableN and P

CH4

El t

Decomposition

Flux

Rainfall Hydrology ElectronAcceptors Nutrients

External LoadingEvapotranspiration

6/22/2008 70WBL

36

Substrate QualityDebusk and Reddy. 1998. Soil Sci. Soc. Am. J. 62:1460-1468

6/22/2008 WBL 71

14C-(Lignin) Lignocelluloses

Spartina

Carex

Spartina

Carex

6/22/2008 WBL 72

Red mangrove Red mangrove

Benner et al. 1985. Limnol. Ocenogr. 30:489-499

37

14C-(Polysaccharide) Lignocelluloses

Spartina Carex

CarexSpartina

6/22/2008 WBL 73

Red mangrove Red mangrove

Benner et al. 1985. Limnol. Ocenogr. 30:489-499

Detrital Decomposition in WetlandsOkeechobee Drainage Basin

6/22/2008 WBL 74

38

0.4


e co

nsta

nt, k

/day

0.3

6/22/2008 WBL 75

Rat

ey


ate

cons

tant

, k/d

ay

6/22/2008 WBL 76

Ra

39

Relative Biodegradability of Substrates [Aerobic]

[Time - half life, days]

Sugars 0.6 daysHemicellulose 7 daysCellulose 14 daysLignin 365 days

6/22/2008 WBL 77

Lignin 365 days

Plant Litter Decomposition

6/22/2008 WBL 78

40

50

60

Lignin Cellulose

Substrate Quality

10

% D

ry m

ass

30

40

20

0Cattail Sawgrass Litter Peat

(0-10 cm)Peat (10-30 cm)

6/22/2008 79WBL

A. Live Tissue[ LCI = 0.14-0.17]

B. Detritus attachedh l

[Lignin][Lignin + Cellulose]LCI =

Water

to the plant[LCI = 0.23-0.29]

C. Detritus[LCI = 0.6]

Soil0-10 cm soil[LCI = 0.73]

10-30 cm soil[LCI = 0.81]

6/22/2008 80WBL

41

Decomposition-Hydrology

6/22/2008 WBL 81

500

600

day-

1 )

Decomposition-Hydrology

0

100

200

300

400

k (m

g C

O2-

C m

-2d

-40 -30 -20 -10 0 10 20 30

Water Depth (cm)

42

3.75

)

AnaerobicAerobic

Alternate Aerobic/Anaerobic Conditions

0.75

1.50

2.25

3.00O

2-C

evo

lved

(mg

g-1 )

28 28 4-64

2-32

6-16

8 4 2

0

0.75

Number aerobic/anaerobic cycles0 1 2 4 8 16 32

CO 12 12 64 32 16 8- 4-

4

2-

0

6/22/2008 83WBL

0 08

0.12

0.16

day

Saggitaria

Decomposition of Decomposition of DetritalDetrital Plant Plant Tissue [Lake Apopka Marsh]Tissue [Lake Apopka Marsh]

0

0.04

0.08

0.12

0.16

yk/

d

Typha Summer

6/22/2008 WBL 84Decomposition N-release P-release

0

0.04

0.08

k/da

y yp Summer

Winter

43

300

on -1)

Microbial Respiration –Soil Temperature

100

200

Soil

resp

iratio

(mg

C m

-2hr

-

0

Soil temperature at 10 cm (°C)0 5 10 15 20

Arrhenius Equationk A E / RTk = A e - E / RT

k = Reaction Rate Constant ; A = Arrhenius coefficient ;E = Activation Energy ; R = Gas constant ; and T = Temperature (K)

6/22/2008 WBL 86

k1 = k2T1 T2

44

10

Microbial Respiration –Soil Temperature

2

4

6

8

Q10

0

2

5 10 15 20Temperature (°C)

0 25 30 35

250D i d ditih-

1 )

Microbial Activity[Site: Water Conservation 2A]

50

100

150

200y = 0.07x + 52

R2 = 0.58

Drained conditions

Flooded conditionsPro

duct

ion

(mg

C k

g-1

h

6/22/2008 WBL 88

0

50

500 1000 1500 2000

y = 0.06x + 26R2 = 0.72

Total Phosphorus (mg P kg-1)

CO

2P

0

45

121416

33.5

mg/

L)

L)

Lake Apopka Marsh

2468

1012

0.51

1.5

22.5

mm

oniu

m-N

(

olub

le P

(mg/

L

N = 0.13 C + 1.56R2 = 0.77; n = 94

P = 0.025 C + 0.56R2 = 0.68 ; n = 94

6/22/2008 WBL 89

0 20 40 60 80 100 1200 0

Dissolved (inorganic + CH4 )-C (mg/L)

Am So

Soil Organic MatterSoil Organic MatterSoil Organic MatterSoil Organic Matter

6/22/2008 WBL 90

46

Detrital plant tissueDetrital plant tissueor Carbon loadingor Carbon loading

Plant Detritus DecompositionPlant Detritus Decomposition

gg

Microbialbiomass

Residue[lignin]

COCO22

6/22/2008 WBL 91

HUMUSHUMUSHumus: Total of the organic compounds in soil exclusive of undecayed plant and animal tissues, their “partial decomposition” products and the soil microbial biomass

Functional Groups

Carboxylic COOHCarboxylic COOHPhenoloic

Hydroxyl OHAmine NH2

OH

6/22/2008 WBL 92

Amine NH2Sulfhydrl SH

47

Functional Groups

6/22/2008 WBL 93

Functions of Organic MatterFunctions of Organic Matter• Source of nutrients for plant growth.p g• Source of energy for soil microorganisms.• Source of exchange capacity for cations.• Provides long-term storage for nutrients.• Strong adsorbing agent for toxic organic

compounds

6/22/2008 WBL 94

compounds.• Complexation of metals.

48

Variable Charge on Soil Organic Matter

COOHOH

O

COO-

OH

O

COO-

O-

O

- H+

+ H+

- H+

+ H+

6/22/2008 WBL 95

Acidic pH Alkali pH

Complexation with Metals• Metal ions that would convert to insoluble

precipitates are maintained in solutionprecipitates are maintained in solution.• Influences the bioavailability of metals.• Some organic complexes with metals may

low solubility.. complexation with humic acids.• Inhibits enzyme activity.

6/22/2008 WBL 96

• Plays a significant role in transporting metals from one ecosystem to another.

49

Complexation with Metals

COOHOH

O

COOO

O

Acidic pH Alkali pH

+ M+ M2+2+

MM+ 2H+

6/22/2008 WBL 97

p p

Greenhouse GasesGreenhouse Gases

6/22/2008 WBL 98

50

6/22/2008 99WBL

400

day)

Methane FluxMethane Flux

100

200

300

Met

hane

Flu

x (m

g C

-CO

2/m2

d

6/22/2008 WBL 100

0 2 4 6 8 10 12 0

Net Ecosystem Productivity (g C-CO2/m2 day)

51

O CH

Methane Production and Oxidation

O2 CH4

CH4

WaterO2 + CH4 CO2

6/22/2008 WBL 101

Soil

CH4OrganicMatter

O2 + CH4

CO2

Carbon Cycle in WetlandsCarbon Cycle in Wetlands

CO

UV

Litter Microbialbiomass

DOC HCO3-

CO2CO2



CH4

Import Export

6/22/2008 WBL 102

Peat Microbialbiomass

DOC HCO3-

CH4


Decompositionleaching

52

SummaryCarbon is important for living systems because it can exist in a


Carbon is important for living systems because it can exist in a variety of oxidation states (-4, 0, +4) and serves as a source of electrons for microbial processes.

Most decomposition of organic matter is driven by oxygen, but less efficient electron acceptors are used in anaerobic processes

Humic substances are divided into three major groups: Fulvic acid (acid and base soluble); Humic acid (acid insoluble and base soluble); Humin (acid and base insoluble)

Detrital matter is broken down into complex polymers (cellulose,

6/22/2008 WBL 103

p p y (proteins, lipids, lignin). Enzymes break these polymers into simple monomers (sugars, amino acids, fatty acids)

Organic mater is a source (short term and long term storage) of nutrients for plants and soil microbes

Enzymatic hydrolysis is the rate limiting step in SOM decomposition

SummaryDecomposition is regulated by substrate quality, electron acceptors


p g y q y, p(who, how many), limiting nutrients, and temperature

Functions of Organic Matter: Source of nutrients for plant growth; source of energy for soil microorganisms; provides long-term storage for nutrients; strong adsorbing agent for toxic organic compounds; complexation of metals

Aerobic decomposition results in the production of oxidized species (CO2. H2O, NO3

-, SO42-, and Mn4+ and Fe3+ oxides), while the

anaerobic decomposition results in the production of reduced species (H f tt id NH + N N O lfid CH F 2+ d M 2+)

6/22/2008 WBL 104

(H2, fatty acids, NH4+, N2, N2O, sulfides, CH4, Fe2+ and Mn2+)

Wetlands contain approximately 15 to 22% of the terrestrial carbon and one of the major contributor to the global methane flux , which accounts for approximately 20 to 25% of global methane to atmosphere

53

Dissolved Organic MatterDissolved Organic Matter

6/22/2008 WBL 105

6/22/2008 WBL 106

http://wetlands.ifas.ufl.eduhttp://wetlands.ifas.ufl.eduhttp://soils.ifas.ufl.eduhttp://soils.ifas.ufl.edu

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