Sensitivity of wetland methane emissions to model assumptions: application and model testing against site observations

Abstract. Methane emissions from natural wetlands and rice paddies constitute a large proportion of atmospheric methane, but the magnitude and year-to-year variation of these methane sources are still unpredictable. Here we describe and evaluate the integration of a methane biogeochemical model (CLM4Me; Riley et al., 2011) into the Community Land Model 4.0 (CLM4CN) in order to better explain spatial and temporal variations in methane emissions. We test new functions for soil pH and redox potential that impact microbial methane production in soils. We also constrain aerenchyma in plants in always-inundated areas in order to better represent wetland vegetation. Satellite inundated fraction is explicitly prescribed in the model, because there are large differences between simulated fractional inundation and satellite observations, and thus we do not use CLM4-simulated hydrology to predict inundated areas. A rice paddy module is also incorporated into the model, where the fraction of land used for rice production is explicitly prescribed. The model is evaluated at the site level with vegetation cover and water table prescribed from measurements. Explicit site level evaluations of simulated methane emissions are quite different than evaluating the grid-cell averaged emissions against available measurements. Using a baseline set of parameter values, our model-estimated average global wetland emissions for the period 1993–2004 were 256 Tg CH4 yr−1 (including the soil sink) and rice paddy emissions in the year 2000 were 42 Tg CH4 yr−1. Tropical wetlands contributed 201 Tg CH4 yr−1, or 78% of the global wetland flux. Northern latitude (>50 N) systems contributed 12 Tg CH4 yr−1. However, sensitivity studies show a large range (150–346 Tg CH4 yr−1) in predicted global methane emissions (excluding emissions from rice paddies). The large range is sensitive to (1) the amount of methane transported through aerenchyma, (2) soil pH (±100 Tg CH4 yr−1), and (3) redox inhibition (±45 Tg CH4 yr−1). Results are sensitive to biases in the CLMCN and to errors in the satellite inundation fraction. In particular, the high latitude methane emission estimate may be biased low due to both underestimates in the high-latitude inundated area captured by satellites and unrealistically low high-latitude productivity and soil carbon predicted by CLM4.

[1]  C. Potter.  An ecosystem simulation model for methane production and emission from wetlands , 1997 .

[2]  M. Lidstrom,et al.  Seasonal Study of Methane Oxidation in Lake Washington , 1984, Applied and environmental microbiology.

[3]  H. Akimoto,et al.  Development of region‐specific emission factors and estimation of methane emission from rice fields in the East, Southeast and South Asian countries , 2003 .

[4]  Jeroen A. H. W. Peters,et al.  Recent trends in global greenhouse gas emissions:regional trends 1970–2000 and spatial distributionof key sources in 2000 , 2005 .

[5]  F. Keppler,et al.  Methane emissions from terrestrial plants under aerobic conditions , 2006, Nature.

[6]  D. Schimel,et al.  Ecosystem and physiological controls over methane production in northern wetlands , 1994 .

[7]  Håkan Rydin,et al.  Biology of peatlands , 2006 .

[8]  C. Joly,et al.  Flooding tolerance of Tabebuia cassinoides: Metabolic, morphological and growth responses , 2009 .

[9]  J. Randerson,et al.  Systematic assessment of terrestrial biogeochemistry in coupled climate–carbon models , 2009 .

[10]  Cho,et al.  Deepwater rice: A model plant to study stem elongation , 1998, Plant physiology.

[11]  R. Sass,et al.  Effects of field drainage on soil parameters related to methane production and emission from rice paddies , 1997 .

[12]  Ralph J. Cicerone,et al.  Seasonal variation of methane flux from a California rice paddy , 1983 .

[13]  Jerome Chappellaz,et al.  Changes in the atmospheric CH4 gradient between Greenland and Antarctica during the Holocene , 1997 .

[14]  Hidenori Takahashi,et al.  Carbon fluxes from a tropical peat swamp forest floor , 2005 .

[15]  K. Yagi,et al.  Global estimations of the inventory and mitigation potential of methane emissions from rice cultivation conducted using the 2006 IPCC guidelines , 2010 .

[16]  P. Döll,et al.  MIRCA2000—Global monthly irrigated and rainfed crop areas around the year 2000: A new high‐resolution data set for agricultural and hydrological modeling , 2010 .

[17]  Markus Reichstein,et al.  Improving canopy processes in the Community Land Model version 4 (CLM4) using global flux fields empirically inferred from FLUXNET data , 2011 .

[18]  R. J. Bartlett,et al.  Soil pH buffering revisited , 1985 .

[19]  D. Lawrence,et al.  Parameterization improvements and functional and structural advances in Version 4 of the Community Land Model , 2011 .

[20]  Yuesi Wang,et al.  Methane and nitrous oxide emissions from three paddy rice based cultivation systems in Southwest China , 2006 .

[21]  R. Conrad.  Control of microbial methane production in wetland rice fields , 2002, Nutrient Cycling in Agroecosystems.

[22]  Peter E. Thornton,et al.  Systematic assessment of terrestrial biogeochemistry in coupled climate–carbon models , 2009 .

[23]  Martin Heimann,et al.  A process‐based, climate‐sensitive model to derive methane emissions from natural wetlands: Application to five wetland sites, sensitivity to model parameters, and climate , 2000 .

[24]  W. J. Riley,et al.  Barriers to predicting changes in global terrestrial methane fluxes: analyses using CLM4Me, a methane biogeochemistry model integrated in CESM , 2011 .

[25]  F. Aires,et al.  Global inundation dynamics inferred from multiple satellite observations, 1993–2000 , 2007 .

[26]  J. Middelburg,et al.  SEASONAL VARIATION IN METHANE OXIDATION BY THE RHIZOSPHERE OF PHRAGMITES AUSTRALIS AND SCIRPUS LACUSTRIS , 1998 .

[27]  Katharine Hayhoe,et al.  Atmospheric methane and global change , 2002 .

[28]  W. Mitsch,et al.  Methane emissions from tropical freshwater wetlands located in different climatic zones of Costa Rica , 2011 .

[29]  N. Shurpali,et al.  Micrometeorological measurements of methane flux in a Minnesota peatland during two growing seasons , 1998 .

[30]  B. Zhu,et al.  Methane and nitrous oxide emissions from three paddy rice based cultivation systems in Southwest China , 2006 .

[31]  Mingkui Cao,et al.  Global carbon exchange and methane emissions from natural wetlands : Application of a process-based model , 1996 .

[32]  Navin Ramankutty,et al.  Geographic distribution of major crops across the world , 2004 .

[33]  F. Chapin,et al.  Methane bubbling from Siberian thaw lakes as a positive feedback to climate warming , 2006, Nature.

[34]  N. Bartoloni,et al.  Different patterns of aerenchyma formation in two hygrophytic species of Paspalum (Poaceae) as response to flooding , 2005 .

[35]  J. F. Meirink,et al.  Inverse Modeling of Global and Regional CH4 Emissions Using SCIAMACHY Satellite Retrievals , 2009 .

[36]  A. Bouwman,et al.  Soils and the greenhouse effect. , 1990 .

[37]  P. Crill,et al.  Methane flux from the Amazon River floodplain: Emissions during rising water , 1990 .

[38]  J. Chanton,et al.  Evaluation of methane oxidation in therhizosphere of a Carex dominated fen in northcentral Alberta, Canada , 2000 .

[39]  J. Lerner,et al.  Three‐dimensional model synthesis of the global methane cycle , 1991 .

[40]  H. Neue,et al.  Ebullition of methane , 1994 .

[41]  R. Crawford,et al.  Methanogenic Bacteria, Including an Acid-Tolerant Strain, from Peatlands , 1985, Applied and environmental microbiology.

[42]  Robert C. Harriss,et al.  Review and assessment of methane emissions from wetlands , 1993 .

[43]  I. Prentice,et al.  Implementation and evaluation of a new methane model within a dynamic global vegetation model: LPJ-WHyMe v1.3.1 , 2010 .

[44]  W. Grosse,et al.  Root aeration in wetland trees by pressurized gas transport. , 1992, Tree physiology.

[45]  J. Knox,et al.  Using a Crop/Soil Simulation Model and GIS Techniques to Assess Methane Emissions from Rice Fields in Asia. II. Model Validation and Sensitivity Analysis , 2000, Nutrient Cycling in Agroecosystems.

[46]  Laurentius A. C. J. Voesenek,et al.  Growth responses of Rumex species in relation to submergence and ethylene , 1989 .

[47]  Inez Y. Fung,et al.  Methane emission from natural wetlands: Global distribution, area, and environmental characteristics of sources , 1987 .

[48]  Keith W. Oleson,et al.  Simulation of Global Land Surface Conditions from 1948 to 2004. Part I: Forcing Data and Evaluations , 2006 .

[49]  Graham D. Farquhar,et al.  A comment on the quantitative significance of aerobic methane release by plants. , 2006, Functional plant biology : FPB.

[50]  R. Delaune,et al.  Soil Redox and pH Effects on Methane Production in a Flooded Rice Soil , 1993 .

[51]  R. Dickinson,et al.  Couplings between changes in the climate system and biogeochemistry , 2007 .

[52]  Ronald G. Prinn,et al.  Joint Program on the Science and Policy of Global Change Methane Fluxes Between Terrestrial Ecosystems and the Atmosphere at Northern High Latitudes During the Past Century : A Retrospective Analysis with a Process-Based Biogeochemistry Model , 2004 .

[53]  Philippe Bousquet,et al.  Constraining global methane emissions and uptake by ecosystems , 2011 .

[54]  J. Waddington,et al.  Ebullition of methane‐containing gas bubbles from near‐surface Sphagnum peat , 2004 .

[55]  Paul J. Crutzen,et al.  An inverse modeling approach to investigate the global atmospheric methane cycle , 1997 .

[56]  N. Davidson,et al.  Global wetland inventory – current status and future priorities , 1999 .

[57]  P. Dunfield,et al.  Methane production and consumption in temperate and subarctic peat soils: Response to temperature and pH , 1993 .

[58]  R. Sass,et al.  Comparison of field measurements of CH4 emission from rice cultivation in Nanjing, China and in Texas, Usa , 2001 .

[59]  Changsheng Li,et al.  A process-oriented model of N2O and NO emissions from forest soils: 1. Model development , 2000 .

[60]  W. Seiler,et al.  Temporal patterns of methane emissions from wetland rice fields treated by different modes of N application , 1994 .

[61]  Pieter P. Tans,et al.  CH4 sources estimated from atmospheric observations of CH4 and its 13C/12C isotopic ratios: 2. Inverse modeling of CH4 fluxes from geographical regions , 2004 .

[62]  C. Curry.  The consumption of atmospheric methane by soil in a simulated future climate , 2009 .

[63]  Stephen Sitch,et al.  Methane flux from northern wetlands and tundra : An ecosystem source modelling approach , 1996 .

[64]  Mingkui Cao,et al.  Global methane emission from wetlands and its sensitivity to climate change , 1998 .

[65]  W. Seiler,et al.  Methane emission from rice paddies , 1983 .

[66]  Reiner Wassmann,et al.  Modeling greenhouse gas emissions from rice‐based production systems: Sensitivity and upscaling , 2004 .

[67]  Maosheng Zhao,et al.  Improvements of the MODIS terrestrial gross and net primary production global data set , 2005 .

[68]  J. Waddington,et al.  Effect of temperature and atmospheric pressure on methane (CH4) ebullition from near‐surface peats , 2006 .

[69]  W. Cheng,et al.  An empirical model of soil chemical properties that regulate methane production in Japanese rice paddy soils. , 2007, Journal of environmental quality.

[70]  Elaine Matthews,et al.  Modeling Modern Methane Emissions from Natural Wetlands. 1; Model Description and Results , 2001 .

[71]  Peter Bergamaschi,et al.  Satellite chartography of atmospheric methane from SCIAMACHY on board ENVISAT: 2. Evaluation based on inverse model simulations , 2007 .

[72]  P. M. Lang,et al.  Atmospheric methane levels off: Temporary pause or a new steady‐state? , 2003 .

[73]  F. Aires,et al.  Interannual variability of surface water extent at the global scale, 1993–2004 , 2010 .

[74]  W. Seiler,et al.  Methane emission during a cultivation period from an Italian rice paddy , 1986 .

[75]  Reinoud Segers,et al.  Methane production and methane consumption: a review of processes underlying wetland methane fluxes , 1998 .

[76]  David M. Lawrence,et al.  Improved simulation of the terrestrial hydrological cycle in permafrost regions by the Community Land Model , 2012 .

[77]  K. Butterbach‐Bahl,et al.  Impact of gas transport through rice cultivars on methane emission from rice paddy fields , 1997 .

[78]  Zong-Liang Yang,et al.  A simple TOPMODEL-based runoff parameterization (SIMTOP) for use in global climate models , 2005 .

[79]  Derek M. Cunnold,et al.  Renewed growth of atmospheric methane , 2008 .

[80]  R. Sass,et al.  A semi‐empirical model of methane emission from flooded rice paddy soils , 1998 .

[81]  A. K. Yadav,et al.  Methane Emissions from Irrigated Rice Fields in Northern India (New Delhi) , 2000, Nutrient Cycling in Agroecosystems.

[82]  J. Waddington,et al.  Dynamics of biogenic gas bubbles in peat and their effects on peatland biogeochemistry , 2005 .

[83]  Catherine Prigent,et al.  An attempt to quantify the impact of changes in wetland extent on methane emissions on the seasonal and interannual time scales , 2010 .

[84]  M. Kimura,et al.  Methane Emission from an Indonesian Paddy Field Subjected to Several Fertilizer Treatments , 1994 .

[85]  Christopher J. Banks,et al.  Global and regional importance of the tropical peatland carbon pool , 2011 .

[86]  K. Yagi,et al.  Global estimations of the inventory and mitigation potential of methane emissions from rice cultivation conducted using the 2006 Intergovernmental Panel on Climate Change Guidelines , 2009 .

[87]  S. Mariko,et al.  Mechanism of Methane Transport from the Rhizosphere to the Atmosphere through Rice Plants. , 1990, Plant physiology.

[88]  S. Whalen,et al.  Biogeochemistry of Methane Exchange between Natural Wetlands and the Atmosphere , 2005 .

[89]  David S. Reay,et al.  Large-Scale Controls of Methanogenesis Inferred from Methane and Gravity Spaceborne Data , 2010, Science.

[90]  Changsheng Li,et al.  An integrated model of soil, hydrology, and vegetation for carbon dynamics in wetland ecosystems , 2002 .

[91]  A. Bouwman.  Conference on soils and the greenhouse effect: organized by the International Soil Reference and Information Centre on behalf of the Netherlands' Ministry of Housing, Physical Planning and Environment, Wageningen, the Netherlands, 14–18 August 1989 , 1990 .

[92]  T. Colmer.  Long-distance transport of gases in plants: a perspective on internal aeration and radial oxygen loss from roots , 2003 .

[93]  P. Martikainen,et al.  Seasonal variation in CH4 emissions and production and oxidation potentials at microsites on an oligotrophic pine fen , 1997, Oecologia.

[94]  Paul J. Crutzen,et al.  Global distribution of natural freshwater wetlands and rice paddies, their net primary productivity, seasonality and possible methane emissions , 1989 .

[95]  C. Prigent,et al.  Modeling regional to global CH4 emissions of boreal and arctic wetlands , 2010 .

[96]  D. Etheridge,et al.  Atmospheric methane between 1000 A.D. and present: Evidence of anthropogenic emissions and climatic variability , 1998 .

[97]  D. Lovley,et al.  Competitive Mechanisms for Inhibition of Sulfate Reduction and Methane Production in the Zone of Ferric Iron Reduction in Sediments , 1987, Applied and environmental microbiology.

[98]  Peter Bergamaschi,et al.  Satellite chartography of atmospheric methane from SCIAMACHY on board ENVISAT: Analysis of the years 2003 and 2004 , 2006 .

[99]  L. Voesenek,et al.  A lack of aerenchyma and high rates of radial oxygen loss from the root base contribute to the waterlogging intolerance of Brassica napus , 1999 .

[100]  J. Chanton,et al.  Control of the Diurnal Pattern of Methane Emission from Emergent Aquatic Macrophytes by Gas Transport Mechanisms , 1996 .

[101]  R. Cicerone,et al.  Methane emissions from California rice paddies with varied treatments , 1992 .

[102]  J. Randerson,et al.  Modeling methane emissions from rice agriculture in China during 1961–2007 , 2010 .

[103]  J. B. Miller,et al.  Contribution of anthropogenic and natural sources to atmospheric methane variability , 2006, Nature.

[104]  R. Prinn,et al.  Estimation of atmospheric methane emissions between 1996 and 2001 using a three-dimensional global chemical transport model , 2006 .

[105]  Niels H. Batjes,et al.  IGBP-DIS soil data set for pedotransfer function development , 1996 .

[106]  Luiz Antonio Martinelli,et al.  Seasonal dynamics in methane emissions from the Amazon River floodplain to the troposphere , 1990 .

[107]  K. Yagi,et al.  Effect of water management on methane emission from a Japanese rice paddy field: Automated methane monitoring , 1996 .

[108]  R. Shannon,et al.  A three-year study of controls on methane emissions from two Michigan peatlands , 1994 .

[109]  Ralph J. Cicerone,et al.  Sources of atmospheric methane: Measurements in rice paddies and a discussion , 1981 .

[110]  Peter G. Hess,et al.  Sensitivity of wetland methane emissions to model assumptions: application and model testing against site observations: Sensitivity of wetland methane emissions to model assumptions , 2011 .

[111]  Kenneth L. Denman Canada.  Couplings between changes in the climate system and biogeochemistry , 2008 .

[112]  Evaluation of methane emissions from West Siberian wetlands based on inverse modeling , 2011 .

[113]  J. Dent,et al.  Modeling methane emissions from rice paddies , 1995 .

[114]  S. Schneider,et al.  A contribution of Working Groups I, II and III to the Third Assessment Report of the Intergovernment Panel on Climate Change , 2001 .

[115]  A. Zehnder,et al.  Geochemistry and biogeochemistry of anaerobic habitats. , 1988 .

[116]  A. Schapendonk,et al.  No evidence for substantial aerobic methane emission by terrestrial plants: a 13C-labelling approach. , 2007, The New phytologist.

[117]  A. Stams,et al.  Effects of alternative electron acceptors and temperature on methanogenesis in rice paddy soils , 1999 .

[118]  W. J. Riley,et al.  Barriers to predicting changes in global terrestrial methane fluxes: analyses using CLM4Me, a methane biogeochemistry model integrated in CESM , 2011 .