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)
Carbon Cycling Processes Carbon Cycling Processes
CO2 OM
6/22/2008 WBL 2
CH4
2
L t O tli
Carbon Cycling Processes Carbon Cycling Processes
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
Carbon Cycling Processes Carbon Cycling Processes
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
Decomposition/leaching
CH4
Import Export
6/22/2008 WBL 9
Peat Microbialbiomass
DOC HCO3-
CH4
Decomposition/leaching
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
MonomersSugars, Amino Acids
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
MonomersSugars, Amino Acids
Fatty Acids
Uptake
Iron RespirationIron Respiration
Products:CO2, H2O,
Fe2+, nutrients
Glucose
PyruvateGlycolysis
Substrate level phosphorylation Acetate
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
MonomersSugars, Amino Acids
Fatty Acids
Uptake
Sulfate Respiration
Glucose
PyruvateGlycolysis
Substrate level phosphorylation Acetate
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
MonomersSugars, Amino Acids
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
Detrital Decomposition in WetlandsOkeechobee Drainage Basin
e co
nsta
nt, k
/day
0.3
6/22/2008 WBL 75
Rat
ey
Detrital Decomposition in WetlandsOkeechobee Drainage Basin
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
Decomposition/leaching
Decomposition/leaching
CH4
Import Export
6/22/2008 WBL 102
Peat Microbialbiomass
DOC HCO3-
CH4
Decomposition/leaching
Decompositionleaching
52
SummaryCarbon is important for living systems because it can exist in a
Carbon Cycling Processes Carbon Cycling Processes
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
Carbon Cycling Processes Carbon Cycling Processes
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