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Institute of Food and Agricultural Sciences (IFAS) Biogeochemistry of Wetlands S i Science and dA Applications li ti Carbon Cycling Processes Wetland Biogeochemistry Laboratory Soil and Water Science Department University of Florida Instructor K. Ramesh Reddy [email protected] 6/22/2008 6/22/2008 1 1 WBL Institute of Food and Agricultural Sciences (IFAS) Carbon Cycling Processes CO2 OM CH4 6/22/2008 WBL 2 1 Carbon Cycling Processes L t Lecture Outline O tli 6/22/2008 Introduction Major components of carbon cycle Organic matter accumulation Characteristics of organic matter Decomposition processes Regulators of organic matter decomposition Greenhouse gases Summary WBL 3 Carbon Cycling Processes Learning Objectives Describe major components of carbon cycle Develop an understanding of the chemical composition of plant litter and soil organic matter Long-term accumulation of organic matter Describe the role of enzymes and microbial communities involved in decomposition Determine organic matter turnover Indentify the role biogeochemical controls and regulators Understand the global significance of carbon cycle Draw a carbon cycle and identify storages and fluxes within and between soil and water column 6/22/2008 WBL 4 2 Oxidation States of Carbon [[+4]] [0] CO2 C6H12O6 [-4] CH4 6/22/2008 WBL 5 Carbon Reservoirs [1014 kg] Atmospheric CO2 Biomass Fresh water Marine Soil organic matter 6/22/2008 WBL 7 4.8 2.5 5-8 30-50 6 3 Soil Organic Matter [SOM] Undecayed plant and animal tissues Partially decomposed material Soil biomass Sources of SOM External: Particulate (inputs) Internal: detrital material (macrophytes, algal mats, roots) 6/22/2008 WBL 7 Detrital Plant Biomass Grazers microorganisms CO2 Aerobic Water table Detritus Decomposition Peat Burial Anaerobic Compaction 6/22/2008 WBL 8 4 Carbon Cycle UV CO2 CO2 CH4 Decomposition/leaching Decomposition/leaching Litter Import Peat Decomposition leaching Microbial biomass DOC HCO3- Microbial biomass DOC HCO3CH4 Export Decomposition/leaching 6/22/2008 WBL 9 Organic Matter ¾ Storages ¾ ¾ ¾ ¾ Soil organic matter Plant detritus/litter Dissolved organic matter Microbial biomass ¾ Transformations ¾ Outputs ¾ Greenhouse gases ¾ Nutrient export ¾ Ecological/Environment al Significance ¾ ¾ ¾ ¾ ¾ Microbial respiration ¾ Methanogenesis M th i 6/22/2008 WBL Carbon sequestration Global warming Water quality Ecosystem productivity 10 5 Net Primary Productivity [g/m2 - year] [Craft, 2001] Bog Marsh Riverine Fresh tidal Brackish Salt Mangroves 6/22/2008 380-800 500 -1100 400-1150 500-1600 600-1600 950-2000 600-1200 WBL 11 Carbon Accumulation in Wetlands [g C/m2 year] Alaska - Sphagnum Finland - Sphagnum - Carex Ontario - Sphagnum bog Georgia - Taxodium Florida - Cladium 6/22/2008 WBL 11-61 20-28 30-32 23 70-105 12 6 Organic Matter Accumulation Soil Depth [cm] 0 Organic g matter accumulation 10 1964 marker 20 Cs-137 Activity 6/22/2008 WBL 13 A. Detritus attached to plant B. Detritus detached from plant Water detritus D. Organic matter and nutrient accretion Soil Plant B C Detritus A Decay continuum 6/22/2008 C. Decomposed detritus from previous year WBL Soil Organic Matter 14 7 Decay Continuum Live plant CO2 CH4 Plant standing dead Litter layer Microbial decomposers Surface peat Buried peat 6/22/2008 WBL 15 Carbon Accumulation in Wetlands Potential energy source (reduced carbon, electron donor Long-term storage of nutrients, heavy metals,, and toxic organic g compounds p Major component of global carbon cycles 6/22/2008 WBL 16 8 Carbon Forms Particulate organic g carbon ((POC)) Microbial biomass carbon (MBC) Dissolved organic carbon (DOC) Dissolved inorganic carbon (DIC) CO2 + H2O = H2CO3 H2CO3 = HCO3- + H+ HCO3- = CO32- + H+ 6/22/2008 WBL 17 Chemical constituents of organic matter Non Humic compounds: Carbohydrates (Simple sugars) Monosaccharides: Polysaccharides: glucose. Starch, Cellulose, and Hemicellulose Proteins Lipids etc Phenolic compounds: 6/22/2008 Lignin Li i (branched (b h d random d polymer l off phenyl h l propanoid id unit) i) Tannins (heterogeneous groups of phenolic compounds) WBL 18 9 Organic Matter (Plant and Soil) • Water soluble components [<10%] – Sugars, Sugars amino acids and fatty acids • • • • • • Cellulose [15-60%] Hemicellulose [10-30%] Lignin [5-30%] Proteins [2-15%] Lipids and Waxes [1-8%] Ash (mineral) [1-13%] 6/22/2008 WBL 19 Cellulose β-D-glucosidic bond CH2OH OH H OH H O H OH H H H OH CH2OH H O H O H H O H 6/22/2008 H OH H H O CH2OH WBL H OH 20 10 Lignin 6/22/2008 WBL 21 Soil Organic Matter [SOM] SOM Extract with Alkali [alkali-soluble] Humin [alkali-insoluble] Treat with Acid Humic Acid Fulvic Acid [acid-insoluble] [acid-soluble] 6/22/2008 WBL 22 11 Fulvic Acid • • • • • • More ‘O’ O and less ‘C’ C. MW 1000 -30,000. Less advanced stage of decomposition. More COOH group per unit mass. Functional group acidity (11 (11.2 2 mol/kg) mol/kg). Alkali and acid soluble. 6/22/2008 WBL 23 Humic Acid • • • • • • More ‘C’ C and less ‘O’ O. MW 10,000 -100,000. Advanced stage of decomposition. Less COOH group per unit mass. Functional group acidity (6.7 mol/kg). Alkali soluble. 6/22/2008 WBL 24 12 Available Carbon Pool Represents small but biologically active fraction of DOC Immediately available for microbial utilization Extremely small in C-limited system Rapid turnover May not be directly measurable Affects short-term community metabolism 6/22/2008 WBL 25 Microbial Biomass 6/22/2008 WBL 26 13 Microorganisms [Percent wet weight] • 70% water • Macromolecules • 15% protein • 3% polysaccharide • 2% lipids • 5% RNA • 1 % DNA • • Total weight of actively growing cell of Escherichia coli Wet wt = 9.5 x 10-13 g 13 g D wtt = 2 Dry 2.8 8 x 10-13 1 % Inorganic ions 3 % others 6/22/2008 WBL 27 Microbial Decomposers Typically 1-5% of total C mass in soil P Process mostt off the th ecosystem t nett production Principal transformers of organic carbon Recycle carbon and nutrients in recalcitrant biopolymers Regulate energy flow and nutrient retention 6/22/2008 WBL 28 14 Techniques to Measure MICROBIAL BIOMASS Di t cellll countt : abundance Direct b d Lipid based : live microbial biomass CHCl3 Fumigation-extraction based: estimate of Carbon Metabolic activity based: Enzyme activities 6/22/2008 WBL 29 MICROBIAL COMMUNITY STRUCTURE Pure culture approach py Microscopy Community level physiological profile (CLPP): Substrate utilization: BIOLOG Measurement of cellular component (physiological status, functional groups):PLFA Methods based on nucleic acids analysis (abundance (abundance, diversity and phylogeny of organisms): gene specific analysis (16S rDNA, DGGE, TGGE, Trflp) 6/22/2008 WBL 30 15 MICROBIAL BIOMASS [Site = WCA-2A - Everglades] 10 9 8 7 LITTER 6 0-10 cm 5 4 10-30 cm 3 2 1 0 0 2 4 6 8 10 Distance from Inflow, km 6/22/2008 WBL 31 MICROBIAL NUMBERS [MPN/g soil] [Site = WCA-2A - Everglades] Substrate Eutrophic Oligotrophic Lactate 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 4.3 < 3.0 3 0 x 103 Formate 2.3 x 105 < 3.0 x 103 Hector et al. 2003 6/22/2008 WBL 32 16 Leaching Detrital Matter Complex Polymers Cellulose; Hemicellulose; Lignin Proteins; Lipids and waxes End product Monomers Bacterial Cell Sugars;Amino acids Fatty acids 6/22/2008 WBL Electron acceptors End products + energy 33 Extracellular Enzymes 6/22/2008 WBL 34 17 Extracellular Enzymes • An extracellular enzyme is involved in transformation or degradation of polymeric substances external to cell membrane 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., detrital particles or clay material (extracellular enzyme) Periplasmic space Bacterial cell Detrital/clay material •Most of these are hydrolases 6/22/2008 WBL 35 Enzymes • Cellulose degradation – Exocellulase - Cellulose – B-glucosidase - Cellobiose • Hemicellulose degradation – Exoxylanase - Xylan – B-xylosidase - Xylobiose • Lignin degradation – Phenol oxidase - Lignin and Phenols 6/22/2008 WBL 36 18 Enzyme – Catalyzed Reaction ES E+S S = Substrate E = Enzyme E+P P = Product All enzymes are proteins – amino acid polymers 6/22/2008 WBL 37 Reactions of Enzymes R-O-PO32- + H2O R-OH + HO-PO32alkaline phosphatase R-O-SO3- + H2O R-OH + H+ + SO42arylsulfatase R-O-glucose + H2O casein + H2O R-OH + glucose β-glucosidase tyrosine protease phenolics + O2 quinones phenol oxidase 6/22/2008 WBL 38 19 Inhibition of enzyme activity Humic acid-Enzyme complex Active Enzyme Humic acid E + E Ca2+ Ca2+ Ca2+ Ca2+ Ca2+ + E Ca2+ Ca2+ Ca2+ 6/22/2008 + E Ca2+ WBL 39 Measurement of Enzymes • Spectroscopic – p-nitrophenol i h l phosphate h h ((pNPP) NPP) • Fluorescence – Methylumbelliferyl phosphate (MUF) – Enzyme Labeled Fluorescence (ELF) P MUF-P 6/22/2008 APase P MUF WBL Pi 40 20 ugg p-nitrophenol g-1 h-1 β Glucosidase Activity 100 50 0 Oxygen Nitrate E h (mV) 618 214 pH 4.5 7.6 6/22/2008 Sulfate Bicarbonate -145 -217 7.5 6.5 WBL 41 β Glucosidase Activity B-D D-Glucosidase Activvity (mgg p- nitrophenol g-11 h-1) 4 [Everglades -WCA WCA--2A] February 2 impacted transitional unimpacted 0 4 May 2 0 4 A August t 2 0 Detritus 6/22/2008 Wright and Reddy, 2001 0-10 cm WBL 10-30 cm 42 21 Pheno oxidase Activity Phen nol Oxidase Activitty (umoole [DQC]g-1 min--1) [Everglades -WCA WCA--2A] Wright and Reddy, 2001 5 4 3 2 1 0 5 4 3 2 1 0 Mayy August Detritus 0-10 cm impacted transitional p unimpacted 10-30 cm DQC = dihydroindole quinone carboxylate 6/22/2008 WBL 43 Microbial Activity 6/22/2008 WBL 44 22 Leaching Detrital Matter Complex Polymers Cellulose; Hemicellulose; Lignin Proteins; Lipids and waxes Reduced product Monomers Bacterial Cell Sugars;Amino acids Fatty acids 6/22/2008 WBL Electron acceptors End products + energy 45 SOIL DEPTH Organic Matter Decomposition Decreasing energy yield 6/22/2008 WBL 46 23 Metabolism • Catabolism • Anabolism • Types of energy source • Light … Phototrophs • Inorganic … Lithotrophs • Organic …. Heterotrophs • Oxidation of organic compounds • Fermentation • Respiration 6/22/2008 WBL 47 Chemolithotrophy Inorganic compound as energy source eg H2S, eg. S Hydrogen gas gas, Fe(II), Fe(II) and NH3 Source of carbon for biosynthesis cannot be organic therefore use CO2 and hence are autotrophs Hydrogen oxidation Sulfur oxidation Ferrous iron oxidation Annamox Nitrification 6/22/2008 WBL 48 24 Phototrophy • Photosynthesis is conversion of light energy into chemical energy. • Most phototrophs are autotrophs ( use CO2 as sole Carbon source). OXYGENIC PHOTOTROPHS H2O Carbon CO2 ANOXYGENIC PHOTOTROPHS Carbon CO2 ADP (CH2O)n ATP ADP H2S hυ hυ 1/2O2 (CH2O)n 6/22/2008 S0 ATP SO42- WBL 49 Metabolism Catabolism Energy sources: Organic, inorganic Organic inorganic, light Waste products: O Organic, i iinorganic i Cell biomass Carbon sources: Organic, CO2 Anabolism 6/22/2008 WBL Nutrients: N, P, K, S, Fe, Mg, ... 50 25 Pathways for Oxidation of Organic Compounds RESPIRATION: Molecular oxygen (aerobic) or other oxidant (Anaerobic) serves as external electron acceptor FERMENTATION: Redox FERMENTATION R d processes occur in i the h absence b off any external electron acceptor reductant BACT TERIA Glucose oxidation Reduction oxidant CO2 + H2 6/22/2008 CO2, NO2-, Fe(II), H2SO O2, NO3-, Fe(III), SO4 WBL 51 Metabolism Assimilative metabolism (biomass) bacteria Dissimilative Metabolism (energy ) Fermentation Respiration Aerobic Anaerobic (Oxygen as electron acceptor) ( Inorganic, metal as electron acceptors) Low energy yield High energy yield 6/22/2008 Anaerobic Organic compounds as electron acceptors WBL 52 26 Aerobic Respiration Detrital Matter Enzyme Hydrolysis Complex Polymers Monomers Sugars, Amino Acids Fatty Acids Cellulose, Hemicellulose, P t i Proteins, Lipids, Li id W Waxes, Li Lignin i Uptake Bacterial Cell Glycolysis Glucose Pyruvate Substrate level phosphorylation TCA Cycle CO2 CO2 Acetyl Co A O2 + e - O2 ATP Oxidative phosphorylation 6/22/2008 WBL H2O 53 Monomers Nitrate Respiration Sugars, Amino Acids Fatty Acids Uptake Glucose Glycolysis Pyruvate TCA Cycle Products: CO2, H2O, N2, N2O, nutrients CO2 Substrate level phosphorylation Acetate NO3- + e- Uptake Lactate Organic Acids [acetate, propionate, butyrate, lactate, alcohols, H2, and CO2] ATP NO3- Nitrate Reducing Bacterial Cell Fermenting Bacterial Cell Terminal reductase enzyme (nitrous oxide reductase) 6/22/2008 WBL 54 27 Monomers Iron Respiration Sugars, Amino Acids Fatty Acids Uptake Glucose Glycolysis Pyruvate TCA Cycle Products: CO2, H2O, Fe2+, nutrients CO2 Substrate level phosphorylation Acetate Fe3+ + e- Organic Acids Uptake [acetate, propionate, butyrate, lactate, alcohols, H2, and CO2] Lactate ATP Fe3+ Iron Reducing Bacterial Cell Fermenting Bacterial Cell Terminal reductase enzyme (ferric reductase) 6/22/2008 WBL 55 Fermentation Organic compound Bacterial Cell Oxidation Oxidized Organic compounds [Pyruvate] Reduction Electron carriers Reduced R d d Organic compounds [Ethanol] 6/22/2008 WBL 56 28 Sulfate Respiration Monomers Sugars, Amino Acids Fatty Acids Uptake Products: CO2, H2O, S2-, nutrients Glucose Glycolysis Oxidative phosphorylation Pyruvate TCA Cycle CO2 Substrate level phosphorylation Acetate SO42- + e- Organic Acids Uptake Lactate Substrate level phosphorylation [acetate, propionate, butyrate, lactate, alcohols, H2, and CO2] ATP Sulfate Reducing Bacterial Cell Fermenting Bacterial Cell SO42- 6/22/2008 WBL 57 Methanogens Archaea…not Archaea not bacteria H2 is electron donor and CO2 is electron acceptor and reduced to CH4 (autotrophic, chemolithotrophy) 131kJ/mol Respiration, not fermentation Some other substrates that can yyield electrons are: Hydrogen methanol Formate 6/22/2008 WBL 58 29 Methanogens Hydrogenotrophic methanogens: use H2 (as electron donor) and CO2 Acetotrophic methanogens: oxidation of acetate results in CO2 and CH4. 6/22/2008 WBL 59 Methanogenesis Fermenting Bacteria CO2 + CH4 Acetate Uptake Substrate level phosphorylation Acetate Products: CO2, H2O, CH4, nutrients Monomers Sugars, Amino Acids Fatty Acids [Acetotrophic methanogens] H+ Lactate H2 Glucose Glycolysis Pyruvate CH4 CO2 + H2 Acetate CO2 + H2 Substrate level phosphorylation Acetogenesis Oxidative phosphorylation [Hydrogenotrophic methanogens] [Acetogens] Organic Acids H2 CH4 H2 + CH3-OH [acetate, propionate, [acetate propionate butyrate butyrate, lactate, alcohols] H2 CO2 Fermenting Bacteria [Methyl substrate utilizers] 6/22/2008 WBL 60 30 Other Terminal Electron Acceptors Inorganic Terminal Electron Acceptors Heavy metals as electron acceptors e.g. • Chromate Ch t Cr(VI) C (VI) Æ Ch Chromium i Cr(III) C (III) 3• Arsenate (AsO4 ) Æ Arsenite (AsO33-) 2• Selenate (SeO4 ) Æ Selenite (SeO32-) Æ inorg. Se Organic Terminal Electron Acceptors Fumarate Æ succinate Trimethyl amine oxide (TMAO) Æ trimethlamine(TMA) Dimethyl sulfoxide (DMSO) Æ Dimethyl sulfide Reductive dechlorination 6/22/2008 WBL 61 AERO OBIC RESPIRA ATION -1 -1 1 (m mg CO2-C g d ) EVERGLADES - WCA-2A 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 04 0.4 0.2 0.0 0 5 10 15 20 25 30 35 40 MICROBIAL BIOMASS C (mg g-1) 6/22/2008 WBL 62 31 Ox xygen consumpttion, mg/kg day Aerobic Respiration 700 600 500 Talladega, AL 400 Salt marsh, LA 300 Houghton Lake marsh, MI Belhaven, NC 200 y=-1036+200 ln(x) R2=0.84 Lake Apopka marsh, FL pothole,, ND Prairie p Crowley, l LA 100 0 Impacted Everglades, g FL Unimpacted Everglades, FL Everglades 0 500 1,000 1,500 2,000 2,500 3,000 3,500 Dissolved organic C, mg/kg 6/22/2008 WBL 63 Nitrate Respiration Denitrification, mg N/kg day y 60 Houghton Lake marsh, MI 50 Impacted Everglades, FL Salt marsh, LA 40 Unimpacted Everglades, FL 30 Prairie pothole, ND 20 Talladega, AL Lake Apopka marsh, FL Belhaven, NC Crowley, LA 10 y=-64+14 ln(x) R2=0.91 0 0 500 1,000 1,500 2,000 2,500 3,000 3,500 Dissolved organic C, mg/kg 6/22/2008 WBL 64 32 Microbial Respiration [Everglades Soils] [mg kg-1 hour-1] D Denitrifying/Sulf fate reeducing conditiions 60 50 Denitrifying y g 40 y = 0.41x + 1.1 r2 = 0.89; n = 24 Sulfate reducing y = 0.33x + 1.3 r2 = 0.88; n = 24 30 20 10 0 10 6/22/2008 20 30 40 50 1 1 Aerobic [mg kg hour ] 60 WBL 65 Microbial Respiration 10 [mg kg-1 hour-1] Metha anogenic condittions [Everglades Soils] 6/22/2008 y = 0.13x 0 13x + 0.3 03 8 CO2 r2 = 0.85, n = 24 6 4 2 y = 0.08x 0 08x - 0.2 02 CH4 r2 = 0.70, n = 24 0 10 20 30 40 50 Aerobic, [mg kg-1 hour-1] WBL 60 66 33 ANAE EROBIC RESP PIRATION (mg C/g d d) Anaerobic vs Aerobic Respiration 0.7 L L 0.6 L A L 0.5 A 0.4 L 0.3 0.2 A AA A S SA S S SSS SS 0.1 0 L L L A A AL L y = 0.324x 0 324 + 0.02 0 02 r2 = 0.94 S 0 0.5 1.0 1.5 2.0 AEROBIC RESPIRATION (mg C/g d) 6/22/2008 WBL 67 Regulators 6/22/2008 WBL 68 34 Regulators of Organic Matter Decomposition Substrate quality carbon to nitrogen ratio or carbon to phosphorus ratio of the substrate Temperature Availability of electron acceptors Microbial populations 6/22/2008 WBL 69 Regulators of Organic Matter Decomposition and Nutrient Release Death/senescence Plant N and P CO2 CH4 Soil Organic Matter Accumulation N and P Rainfall Electron El t Acceptors Hydrology Evapotranspiration 6/22/2008 Decomposition Flux Bioavailable N and P Nutrients External Loading WBL 70 35 Substrate Quality Debusk and Reddy. 1998. Soil Sci. Soc. Am. J. 62:1460-1468 6/22/2008 WBL 14C-(Lignin) 71 Lignocelluloses Carex Spartina Spartina Carex Red mangrove Red mangrove Benner et al. 1985. Limnol. Ocenogr. 30:489-499 6/22/2008 WBL 72 36 14C-(Polysaccharide) Spartina Lignocelluloses Carex Carex Red mangrove Spartina Red mangrove Benner et al. 1985. Limnol. Ocenogr. 30:489-499 6/22/2008 WBL 73 Detrital Decomposition in Wetlands Okeechobee Drainage Basin 6/22/2008 WBL 74 37 Detrital Decomposition in Wetlands Okeechobee Drainage Basin Rate e constant, k/day 0.4 6/22/2008 0.3 WBL 75 Detrital Decomposition in Wetlands Ra ate constant, k/dayy Okeechobee Drainage Basin 6/22/2008 WBL 76 38 Relative Biodegradability of Substrates [Aerobic] [Time - half life, days] Ð Ð Ð Ð 6/22/2008 Sugars Hemicellulose Cellulose Lignin 0.6 days 7 days 14 days 365 days WBL 77 Plant Litter Decomposition 6/22/2008 WBL 78 39 Substrate Quality 60 Lignin Cellulose % Dry mass 50 40 30 20 10 0 Cattail 6/22/2008 Sawgrass Litter Peat (0-10 cm) Peat (10-30 cm) WBL A. Live Tissue [ LCI = 0.14-0.17] 79 LCI = [Lignin] [Lignin + Cellulose] B. Detritus attached to the h plant l [LCI = 0.23-0.29] C. Detritus [LCI = 0.6] Water 0-10 cm soil [LCI = 0.73] Soil 10-30 cm soil [LCI = 0.81] 6/22/2008 WBL 80 40 Decomposition-Hydrology 6/22/2008 WBL 81 k (mg CO2-C m-2 d day-1) Decomposition-Hydrology 600 500 400 300 200 100 0 -40 -30 -20 -10 0 10 20 30 Water Depth (cm) 41 Alternate Aerobic/Anaerobic Conditions Anaerobic Aerobic 3.00 2.25 2-2 2 4 4-4 1 8-8 32 2-32 0 16 6-16 64 4-64 0.75 12 28 1.50 12 28 CO O2-C evolved (mg g-1) 3.75 4 8 16 32 0 0 Number aerobic/anaerobic cycles 6/22/2008 WBL 83 Decomposition of Detrital Plant Tissue [Lake Apopka Marsh] k/d day 0.16 0.12 Saggitaria 0 08 0.08 0.04 k/dayy 0 0.16 0.12 Typha yp 0.08 Summer Winter 0.04 0 6/22/2008 Decomposition N-release WBL P-release 84 42 Microbial Respiration – Soil Temperature Soil respiratio on -2 (mg C m hr--1) 300 200 100 0 0 5 10 15 20 Soil temperature at 10 cm (°C) Arrhenius Equation k = A e - E / RT k = Reaction Rate Constant ; A = Arrhenius coefficient ; E = Activation Energy ; R = Gas constant ; and T = Temperature (K) k1 = k2 6/22/2008 WBL T1 T2 86 43 Microbial Respiration – Soil Temperature 10 Q10 8 6 4 2 0 0 5 10 15 20 25 Temperature (°C) 30 35 Microbial Activity CO2 P Production (mg C kg-1 h-1) [Site: Water Conservation 2A] 250 D i d conditions Drained diti y = 0.07x + 52 200 R2 = 0.58 150 100 Flooded conditions 50 y = 0.06x + 26 R2 = 0.72 0 0 500 1000 1500 2000 Total Phosphorus (mg P kg-1) 6/22/2008 WBL 88 44 16 14 12 10 8 6 4 2 0 0 3.5 3 2.5 N = 0.13 C + 1.56 R2 = 0.77; n = 94 2 1.5 1 P = 0.025 C + 0.56 R2 = 0.68 ; n = 94 20 40 60 80 100 0.5 0 120 Sooluble P (mg/L L) Am mmonium-N (mg/L) Lake Apopka Marsh Dissolved (inorganic + CH4 )-C (mg/L) 6/22/2008 WBL 89 Soil Organic Matter 6/22/2008 WBL 90 45 Plant Detritus Decomposition Detrital plant tissue or Carbon loading g Residue [lignin] CO2 Microbial biomass HUMUS Humus: Total of the organic compounds in soil exclusive of undecayed plant and animal tissues, their “partial decomposition” products and the soil microbial biomass 6/22/2008 WBL 91 Functional Groups 6/22/2008 ¾ Carboxylic ¾ Phenoloic COOH OH ¾ Hydroxyl ¾ Amine ¾ Sulfhydrl OH NH2 SH WBL 92 46 Functional Groups 6/22/2008 WBL 93 Functions of Organic Matter • • • • • Source of nutrients for p plant g growth. 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 compounds. • Complexation of metals. 6/22/2008 WBL 94 47 Variable Charge on Soil Organic Matter COOH OH - H+ O COO+ OH - H + H+ O + H+ O Acidic pH 6/22/2008 COOO- Alkali pH WBL 95 Complexation with Metals • Metal ions that would convert to insoluble precipitates are maintained in solution solution. • Influences the bioavailability of metals. • Some organic complexes with metals may low solubility.. complexation with humic acids. • Inhibits enzyme activity. • Plays a significant role in transporting metals from one ecosystem to another. 6/22/2008 WBL 96 48 Complexation with Metals COOH OH COO M O + M2+ + 2H+ O O Acidic p pH 6/22/2008 Alkali p pH WBL 97 Greenhouse Gases 6/22/2008 WBL 98 49 6/22/2008 WBL 99 Methane Flux (mg C-CO2/m2 d day) Methane Flux 400 300 200 100 0 0 2 4 6 8 10 12 Net Ecosystem Productivity (g C-CO2/m2 day) 6/22/2008 WBL 100 50 Methane Production and Oxidation O2 CH4 CH4 Water O2 + CH4 CO2 CO2 Soil O2 + CH4 Organic Matter 6/22/2008 CH4 WBL 101 Carbon Cycle in Wetlands UV CO2 CO2 CH4 Decomposition/leaching Decomposition/leaching Litter Import Peat Decomposition leaching Microbial biomass DOC HCO3- Microbial biomass DOC HCO3CH4 Export Decomposition/leaching 6/22/2008 WBL 102 51 Carbon Cycling Processes Summary 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 p p polymers y ((cellulose, 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 6/22/2008 WBL 103 Carbon Cycling Processes Summary Decomposition p is regulated g by y substrate q quality, y, electron acceptors 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 (H2, fatty f tt acids, id NH4+, N2, N2O, O sulfides, lfid CH4, Fe F 2+ and dM 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 6/22/2008 WBL 104 52 Dissolved Organic Matter 6/22/2008 6/22/2008 WBL http://wetlands.ifas.ufl.edu http://soils.ifas.ufl.edu WBL 105 106 53
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