Institute of Food and Agricultural Sciences (IFAS) Biogeochemistry of Wetlands SiScience an dAd App litilications NITROGEN Wetland Biogeochemistry Laboratory Soil and Water Science Department University of Florida Instructor : Patrick Inglett [email protected] 6/22/20086/22/2008 P.W.WBL Inglett1 1 Nitrogen Introduction N Forms, Distribution, Importance Basic processes of N Cycles Examples of current research Examples of applications Key points learned 6/22/2008 P.W. Inglett 2 1 Nitrogen Learning Objectives Identify the forms of N in wetlands Understand the importance of N in wetlands/global processes Define the major N processes/transformations Understand the importance of microbial activity in N transformations Understand the potential regulators of N processes See the application of N cycle principles to understanding natural and man-made ecosystems 6/22/2008 P.W. Inglett 3 Nitrogen Cycling Plant biomass N N2 NH3 N2 N2O (g) Litterfall Nitrogen Fixation Volatilization Mineralization. Water - Nitrification + + NO3 NH4 Organic N NH4 Column AEROBIC - Plant Peat NO3 + + [NH4 ]s uptake accretion [NH4 ]s Denitrification ANAEROBIC Microbial + Organic N Biomass N Adsorbed NH4 N2, N2O (g) 6/22/2008 P.W. Inglett 4 2 Forms of Nitrogen Organic Nitrogen Inorganic Nitrogen + • Proteins • Ammonium (NH4 ) - • Amino Sugars • Nitrate N (NO3 ) - • Nucleic Acids • Nitrite N (NO2 ) • Urea • Nitrous ox ide (N2O) • Dinitrogen (N2) 6/22/2008 P.W. Inglett 5 N Transformations Solid Gaseous Phase: Phase: Particulate N N2 + Bound: NH4 N2O - - NO3 NO2 Aqueous Phase: + NH4 DON - DIN NO3 - Particulate N NO2 6/22/2008 P.W. Inglett 6 3 Reservoirs of Nitrogen Lithosphere 163,600 x 1018 g Atmosphere 3,860 x 1018 g Hydrosphere 23 x 1018 g Biosphere 0.28 x 1018 g 6/22/2008 P.W. Inglett 7 Forms of Nitrogen Total Soil N Organic Inorganic + Protein NH4 + Amino sugars Clay-fixed NH4 Heterocyclic N 6/22/2008 P.W. Inglett 8 4 Nitrogen Transformations 1. Ammonification/Mineralization 2. Immobilization 3. Nitrification 4. Denitrification 5. Dissimilatory nitrate reduction to ammonia (DNRA) 6. Nitrogen fixation 7. Ammonia volatilization 6/22/2008 P.W. Inglett 9 Transformation of N Species Organic N 2 1 + NH4 5 8e- 7 3 NO - 3 3 3 4e- - NH2OH 4 2e - NH3 - 2e NO2 2 e- 4 2e- N2O 6 3e- 4 N2 1e- 0 +1 +2+3 +4 -3 -2 -1 +5 Oxidation Number 6/22/2008 P.W. Inglett 10 5 Nitrogen Cycle Plant/Algae + - Org-N NH4 NO3 N-FixersMicrobialNit rBiomassifi ers DitifiDen it rifiers N2 N2/N2O 6/22/2008 P.W. Inglett 11 Productivity 6/22/2008 P.W. Inglett 12 6 Greenhouse Gas Emissions 6/22/2008 P.W. Inglett 13 Nitrogen Budget Biological N2 fixation Dry and wet deposition Non-point sources Wastewaters Plant biomass Microbial biomass Soil organic N Porewater (DIN, DON) Exchangeable N Clay fixed NH4-N Volatilization Outflow Gaseous losses Plant harvest 6/22/2008 P.W. Inglett 14 7 Ammonium Ion Wet Deposition 1985-2003 1985 2003 http://nadp.sws.uiuc.edu/isopleths/ 6/22/2008 P.W. Inglett 15 Nitrate Ion Wet Deposition 1985-2003 1985 2003 6/22/2008 P.W. Inglett 16 8 Inorganic N Wet Deposition 1985 1985-2003 2003 6/22/2008 P.W. Inglett 17 Biological Nitrogen Fixation Plant biomass N N2 NH3 N2 N2O (g) Litterfall Nitrogen Fixation Volatilization Mineralization. Water - Nitrification + + NO3 NH4 Organic N NH4 Column AEROBIC - Plant Peat NO3 + + [NH4 ]s uptake accretion [NH4 ]s Denitrification ANAEROBIC Microbial + Organic N Biomass N Adsorbed NH4 N2, N2O (g) 6/22/2008 P.W. Inglett 18 9 Nitrogen Fixation 12 -1 Type of fixation N2 fixed (10 g yr ) Non-biological Industrial about 50 Combustion about 20 Lightning about 10 Total about 80 Biological Agricultural land about 90 FtdForest and non-agriltlldicultural land abt50bout 50 Sea about 35 Total about 175 6/22/2008 P.W. Inglett 19 Biological N2 Fixation + - N N + 8H + 8e + 16ATP → 2NH3 + H2 + 16ADP + 16Pi Nitrogenase 6/22/2008 P.W. Inglett 20 10 Biological N2 Fixation Prokaryotes Aerobic Anaerobic Associated w/ Plants Azotobacter Clostridium Rhizobium Beijerinckia Desulfovibrio Frankia Klebsiella Cyanobacteria Azospirillum Cy anobacteria 6/22/2008 P.W. Inglett 21 Biological N2 Fixation Heterocysts (cyanobacteria) Leghaemoglobin (rhizobium) Exopolysaccharides Temporal isolation http://www.bact.wisc.edu/Microtextbook/ images/book_4/chapter_2/2-53.jpg 6/22/2008 P.W. Inglett 22 11 Temporal Isolation y Heterocystous Nitrogenase activit Non-heterocystous 12:00 24:00 12:00 Time (h) 6/22/2008 P.W. Inglett 23 Biological N2 Fixation Regulators? Light Concentration of Oxygen Growth limitation Macro nutrients (C, P) Co-factors (Fe, Mo) Inc. Growth Inc. N Demand Species Inc. N2 shift Fixation 6/22/2008 P.W. Inglett 24 12 Nitrogen Mineralization Plant biomass N N2 NH3 N2 N2O (g) Litterfall Nitrogen Fixation Volatilization Mineralization. Water - Nitrification + + NO3 NH4 Organic N NH4 Column AEROBIC - Plant Peat NO3 + + [NH4 ]s uptake accretion [NH4 ]s Denitrification ANAEROBIC Microbial + Organic N Biomass N Adsorbed NH4 N2, N2O (g) 6/22/2008 P.W. Inglett 25 Organic Nitrogen Proteins Amino acids (30-50% of total organic N) Nucleic Acids 2-5 % of total organic N Amino Sugars 3-13% of total organic N Urea 6/22/2008 P.W. Inglett 26 13 Protein Decomposition Proteins Peptides AiAmino ac ids Arg Pro ProteasesPro Peptidases Arg Ala Ala Asp Phe Phe Asp Lys Pro Lys Pro 6/22/2008 P.W. Inglett 27 H R1 O H R2 O H R3 O N -C -C -OH N -C -C -OH N -C -C -OH H H H H H H -2H2O H R1 O R2 O R3 O N -C -C - N -C -C - N -C -C - OH H H H HHH Peptide Bonds 6/22/2008 P.W. Inglett 28 14 H R1 O H R2 O H R3 O N -C -C -OH N -C -C -OH N -C -C -OH H H H H H H + 2H2O H R1 O R2 O R3 O N -C -C - N -C -C - N -C -C - OH H H H H H H Peptide Bonds 6/22/2008 P.W. Inglett 29 Detrital Matter Enzyme Leaching Complex Polymers Hydrolysis Monomers Cellulose, Hemicellulose, Sugars, Amino Acids Proteins, Lipids, Waxes, Lignin Fatty Acids Uptake Bacterial Cell Electron Acceptors: Amino acids - 4+ O2, NO3 , Mn , 3+ 2- Fe , SO4 , CO2 Products: + NH4 CO2, H2O, Energy + 2+ NH4 , Mn , ATP 2+ 2- Fe ,S ,CH4 + NH4 6/22/2008 P.W. Inglett 30 15 Urea Decomposition NH2 Urease C = O + H2O CO2 + 2NH3 NH2 6/22/2008 P.W. Inglett 31 Urea Decomposition Urease activity (14C Tracer) [Thorén (2007)] 6/22/2008 P.W. Inglett 32 16 Ammonification [Mineralization] Organic N Ammonium N [Brea kdown of O rgani c M att er] Immobilization Inorganic N Organic N (NH4-N and NO3 -N) [Buildup of Organic Matter] 6/22/2008 P.W. Inglett 33 Ammonification/NAmmonification/N--MineralizationMineralization Organic N Ammonium R - HOOCC NH 2 NH4 + H NN--ImmobilizationImmobilization Inorganic N Organic N R NH 4 - + HOOCC NH 2 - NO3 H 6/22/2008 P.W. Inglett 34 17 Microbial Biomass C & N [Everglades[Everglades--WCAWCA--2A]2A] y = 10.7 x + 2.2 25 R2 = 0.78 20 15 ) -1 10 5 (g C kg robial biomass C c 0 Mi 00.51.0 1.5 2.0 Microbial biomass N (g N kg-1) White and Reddy, 2000 6/22/2008 P.W. Inglett 35 Decomposition Microbial Biomass C/N ratio = 10 Effic iency o f car bon ass im ilati on Aerobic = 20-60% Anaerobic = 10% Plant Detritus [100 units] 40% carbon (dry weight basis) = 40 units C Amount of C assimilated during decomposition Aerobic = 16 units [40% efficiency] Anaerobic = 4 units [10% efficiency] 6/22/2008 P.W. Inglett 36 18 Carbon/Nitrogen Ratio Nitrogen Demand? Micro bia l Biomass C/N ra tio = 10 Aerobic = 1.6 units Anaerobic = 0.4 units Critical Plant Detritus Nitrogen? Aerobic = 1.6 % Anaerobic = 0.4% Critical Carbon/Nitrogen Ratio? Aerobic = [40% C]/[1.6% N] = 25 Anaerobic = [40% C]/[0.4% N] = 100 6/22/2008 P.W. Inglett 37 Carbon/Nitrogen Ratio Mineralization [M] vs. Immobilization [I] Aerobic I > M = C/N ratio > 25 M > I = C/N ratio < 25 Anaerobic I > M = C/N ra tio > 100 M > I = C/N ratio < 100 6/22/2008 P.W. Inglett 38 19 N Mineralization/Immobilization [Aerobic] ase C/N = 15 e C/N = 35 organic N Rel C/N = 100 n I Decomposition (days) 6/22/2008 P.W. Inglett 39 N Mineralization/Immobilization [Aerobic] 40 Immobilization Ratio n 30 20 Mineralization rbon/Nitroge 10 a C C/N ratio of soil humus/ microbial biomass 0 0 150 Decomposition Period [days] 6/22/2008 P.W. Inglett 40 20 Regulators of Ammonification Substrate quality C/N ratio of the substrate Secondary compounds N forms (soluble vs. structural compounds) Microbial Activity Extracellular enzyme activity Supply of electron acceptors (Redox) Temperature pH 6/22/2008 P.W. Inglett 41 Mineralizable Nitrogen [Everglades[Everglades--WCAWCA--2A]2A] 400 y = 0.317 x + 52.4 R2 = 0.76 ) 300 -1 d -1 200 (mg N kg 100 ineralization Rate M 0 0 100 200 300 400 + -1 Extractable NH4 (mg N kg ) 6/22/2008 P.W. Inglett 42 21 Fate of Ammonium Plant biomass N N2 NH3 N2 N2O (g) Litterfall Nitrogen Fixation Volatilization Mineralization. Water - Nitrification + + NO3 NH4 Organic N NH4 Column AEROBIC - Plant Peat NO3 + + [NH4 ]s uptake accretion [NH4 ]s Denitrification ANAEROBIC Microbial + Organic N Biomass N Adsorbed NH4 N2, N2O (g) 6/22/2008 P.W. Inglett 43 Nitrogen Uptake by Rice (15N) TtlNTotal N up tktake Added 15N uptake Nitrogen uptake N-uptake fro m Soil organic N Growing season 6/22/2008 P.W.