Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 6 11 2006 10.5194/acp-6-3181-2006 http://www.atmos-chem-phys.net/6/3181/2006/ http://www.atmos-chem-phys.net/6/3181/2006/acp-6-3181-2006.html http://www.atmos-chem-phys.net/6/3181/2006/acp-6-3181-2006.pdf 3181 3210 2006-08-02 Estimates of global terrestrial isoprene emissions using MEGAN (Model of Emissions of Gases and Aerosols from Nature) A. Guenther guenther@ucar.edu T. Karl P. Harley C. Wiedinmyer P. I. Palmer C. Geron Atmospheric Chemistry Division, National Center for Atmospheric Research, 1850 Table Mesa Drive, Boulder Colorado, 80305, USA School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK National Risk Management Research Laboratory, U.S. Environmental Protection Agency, 109 TW Alexander Dr., Research Triangle Park, NC, 27711, USA Reactive gases and aerosols are produced by terrestrial ecosystems, processed within plant canopies, and can then be emitted into the above-canopy atmosphere. Estimates of the above-canopy fluxes are needed for quantitative earth system studies and assessments of past, present and future air quality and climate. The Model of Emissions of Gases and Aerosols from Nature (MEGAN) is described and used to quantify net terrestrial biosphere emission of isoprene into the atmosphere. MEGAN is designed for both global and regional emission modeling and has global coverage with ~1 km² spatial resolution. Field and laboratory investigations of the processes controlling isoprene emission are described and data available for model development and evaluation are summarized. The factors controlling isoprene emissions include biological, physical and chemical driving variables. MEGAN driving variables are derived from models and satellite and ground observations. Tropical broadleaf trees contribute almost half of the estimated global annual isoprene emission due to their relatively high emission factors and because they are often exposed to conditions that are conducive for isoprene emission. The remaining flux is primarily from shrubs which have a widespread distribution. The annual global isoprene emission estimated with MEGAN ranges from about 500 to 750 Tg isoprene (440 to 660 Tg carbon) depending on the driving variables which include temperature, solar radiation, Leaf Area Index, and plant functional type. The global annual isoprene emission estimated using the standard driving variables is ~600 Tg isoprene. Differences in driving variables result in emission estimates that differ by more than a factor of three for specific times and locations. It is difficult to evaluate isoprene emission estimates using the concentration distributions simulated using chemistry and transport models, due to the substantial uncertainties in other model components, but at least some global models produce reasonable results when using isoprene emission distributions similar to MEGAN estimates. In addition, comparison with isoprene emissions estimated from satellite formaldehyde observations indicates reasonable agreement. The sensitivity of isoprene emissions to earth system changes (e.g., climate and land-use) demonstrates the potential for large future changes in emissions. Using temperature distributions simulated by global climate models for year 2100, MEGAN estimates that isoprene emissions increase by more than a factor of two. This is considerably greater than previous estimates and additional observations are needed to evaluate and improve the methods used to predict future isoprene emissions. Abbot, D., Palmer, P., Martin, R., Chance, K., Jacob, D., and Guenther, A.: Seasonal and interannual variability of isoprene emissions as determined by formaldehyde column measurements from space, Geophys. Res. Lett., 17, 1886, doi:10.1029/2003GL017336, 2003. Adams, J., Constable, J., Guenther, A., and Zimmerman, P.: An estimate of natural volatile organic compound emissions from vegetation since the last glacial maximum, Chemosphere- Global Change Science, 3, 73–91, 2001. Alcamo, J., Leemans R., and Kreileman, E. (Eds.): Global change scenarios of the 21st century. Results from the IMAGE 2.1 model, Pergamon & Elseviers Science, London, pp. 296, 1998. Alessio, G. A., De Lillis, M., Fanelli, M., Pinelli, P., and Loreto, F.: Direct and indirect impacts of fire on isoprenoid emissions from Mediterranean vegetation, Functional Ecology, 18(3), 357–364, 2004. Andreae, M. O., Artaxo, P., Brandao, C., Carswell, F. E., Ciccioli, P., da Costa, A. L., Culf, A. D., Esteves, J. L., Gash, J., and Grace, J.: Biogeochemical cycling of carbon, water, energy, trace gases, and aerosols in Amazonia: The LBA-EUSTACH experiments, J. Geophys. Res., 107(D20), 8066, doi:10.1029/2001JD000524, 2002. Atkinson, R. and Arey, J.: Atmospheric chemistry of biogenic organic compounds, Acc. Chem. Res., 31, 574–583, 1998. Bai, J., Baker, B., Liang, B., Greenberg, J., and Guenther, A.: Isoprene and monoterpene emissions from an Inner Mongolia grassland, Atmos. Environ., in press, 2006. Baldocchi, D.: Flux footprints within and over forest canopies, Boundary-Layer Meteorology, 85(2), 273–292, 1997. Bey, I., Jacob, D. J., Yantosca, R. M., Logan, J. A., Field, B. D., Fiore, A. M., Li, Q., Liu, H. Y., Mickley, L. J., and Schultz, M. G.: Global modeling of tropospheric chemistry with assimilated meteorology: Model description and evaluation, J. Geophys. Res., 106, 23 073–23 096, 2001. Bonan, G. B., Levis, S., Kergoat, L., and Oleson, K. W.: Landscapes as patches of plant functional types: An integrating concept for climate and ecosystem models, Global Biogeochem. Cycles, 16(2), 1021, doi:10.1029/2000GB001360, 2002. Brown, J. and Smith, J.: Wildland fire in ecosystems: effects of fire on flora, U.S. Department of Agriculture, Forest Service, Ogden, UT, 2000. Bruggemann, N. and Schnitzler, J. P.: Diurnal variation of dimethylallyl diphosphate concentrations in oak (Quercus robur L.) leaves, Physiol. Plant., 115, 190–196, 2002. Buckley, P. T.: Isoprene emissions from a Florida scrub oak species grown in ambient and elevated carbon dioxide, Atmos. Environ., 35, 631–634, 2001. Centritto, M., Nascetti, P., Petrilli, L., Raschi, A., and Loreto, F.: Profiles of isoprene emission and photosynthetic parameters in hybrid poplars exposed to free-air CO2 enrichment, Plant Cell and Environment, 27(4), 403–412, 2004. Che, H., Shi, G., Zhang, X., Arimoto, R., Zhao, J., Zhao, L., Wang, B., and Chen, Z.: Analysis of 40 years of solar radiation data from China, Geophys. Res. Lett., 32, L06803, doi:10.1029/2004GL022322, 2005. Chen, F. and Dudhia, J.: Coupling an Advanced Land Surface – Hydrology Model with the Penn State – NCAR MM5 Modeling System. Part I: Model Implementation and Sensitivity, Mon. Wea. Rev., 129(4), 569–585, 2001. Clark, W.: China's Green Manure Revolution, Science, 80(1) 69–73, 1980. Collins, W. J., Derwent, R. G., Johnson, C. E., and Stevenson, D. S.: The oxidation of organic compounds in the troposphere and their global warming potentials, Climatic Change, 52(4), 28, 2002. DeFries, R., Hansen, M., Townshend, J. R. G., Janetos, A. C., and Loveland, T. R.: A new global 1 km data set of percent tree cover derived from remote sensing, Global Change Biology, 6, 247–254, 2000. Dudhia, J. and Bresch, J. F.: A global version of the PSU-NCAR mesoscale model, Mon. Wea. Rev., 130, 2989–3007, 2002. Ehhalt, D. and Prather, M.: Atmospheric Chemistry and Greenhouse Gases, in: Climate Change 2001; Working Group 1: The Scientific Basis, edited by: Houghton, J., Ding, Y., Griggs, D., Noguer, M., van der Linden, P., and Xiaosu, D., Cambridge University Press, 2001. Ennis, C. A., Lazrus, A. L., Zimmerman, P. R., and Monson, R. K.: Flux determination and physiological response in exposure of red spruce to gaseous hydrogen peroxide, ozone, and sulfur dioxide., Tellus Series B – Chemical and Physical Meteorology, 42B, 183–199, 1990. Fall, R. and Wildermuth, M. C.: Isoprene synthase: From biochemical mechanism to emission algorithm, J. Geophys. Res., 103(D19), 25, 1998. Friedl, M. A., McIver, D. K., Hodges, J. C. F., Zhang, X. Y., Muchoney, D., Strahler, A. H., Woodcock, C. E., Gopal, S., Schneider, A., Cooper, A., Baccini, A., Gao, F., and Schaaf, C.: Global Land Cover Mapping from MODIS: Algorithms and Early Results, Remote Sens. Environ., 83(1–2), 287–302, 2002. Fuentes, J. D., Lerdau, M., Atkinson, R., Baldocchi, D., Bottenheim, J. W., Ciccioli, P., Lamb, B., Geron, C., Gu, L., Guenther, A., Sharkey, T. D., and Stockwell, W.: Biogenic Hydrocarbons in the Atmospheric Boundary Layer: A Review, Bull. Amer. Meteorol. Soc., 81(7), 1537–1576, 2000. Fukui, Y. and Doskey, P. V.: Air-surface exchange of nonmethane organic compounds at a grassland site: Seasonal variations and stressed emissions, J. Geophys. Res., 103(D11), 13, 1998. Funk, J. L., Jones, C. G., Baker, C. J., Fuller, H. M., Giardina, C. P., and Lerdau, M. T.: Diurnal variation in the basal emission rate of isoprene, Ecological Applications, 13(1), 269, 2003. Geron, C. D., Guenther, A. B., and Pierce, T. E.: An improved model for estimating emissions of volatile organic compounds from forests in the eastern United States (Paper 94JD00246), J. Geophys. Res., 99(D6), 12 773, 1994. Geron, C., Guenther, A., Sharkey, T., and Arnts, R. R.: Temporal variability in basal isoprene emission factor, Tree Physiology, 20(12), 799–805, 2000. Geron, C., Owen, S., Guenther, A., Greenberg, J., Rasmussen, R., Bai, J. H., Li, Q. J., and Baker, B.: Volatile organic compounds from vegetation in southern Yunnan Province, China: Emission rates and some potential regional implications, Atmos. Environ., 40(10), 1759–1773, 2006. Goldstein, A., Goulden, M., Munger, J. W., Wofsy, S., and Geron, C.: Seasonal course of isoprene emissions from a midlatitude forest, J. Geophys. Res., 103, 31 045–31 056, 1998. Graedel, T. E., Bates, T. S., Bouwman, A. F., Cunnold, D., Dignon, J., Fung, I., Jacob, D. J., Lamb, B. K., Logan, J. A., Marland, G., Middleton, P., Pacyna, J. M., Placet, M., and Veldt, C.: A compilation of inventories of emissions to the atmosphere, Global Biogeochem. Cycles, 7, 1–26, 1993. Granier, C., Petron, G., Muller, J. F., and Brasseur, G.: The impact of natural and anthropogenic hydrocarbons on the tropospheric budget of carbon monoxide, Atmos. Environ., 34(29–30), 5255–5270, 2000. Greenberg, J. P., Guenther, A., Zimmerman, P., Baugh, W., Geron, C., Davis, K., Helmig, D., and Klinger, L. F.: Tethered balloon measurements of biogenic VOCs in the atmospheric boundary layer, Atmos. Environ., 33(6), 855–867, 1999. Guenther, A. B., Monson, R. K., and Fall, R.: Isoprene and monoterpene emission rate variability: Observations with eucalyptus and Emission Rate Algorithm Development, J. Geophys. Res., 96, 10 799–10 808, 1991. Guenther, A. B., Zimmerman, P. R., Harley, P. C., Monson, R. K., and Fall, R.: Isoprene and Monoterpene Emission Rate Variability – Model Evaluations and Sensitivity Analyses, J. Geophys. Res.-Atmos., 98(D7), 12 609–12 617, 1993. Guenther, A., Hewitt, C. N., Erickson, D., Fall, R., Geron, C., Graedel, T., Harley, P., Klinger, L., Lerdau, M., Mckay, W. A., Pierce, T., Scholes, B., Steinbrecher, R., Tallamraju, R., Taylor, J., and Zimmerman, P. A.: Global-Model of Natural Volatile Organic-Compound Emissions, J. Geophys. Res.-Atmos., 100(D5), 8873–8892, 1995. Guenther, A., Greenberg, J., Harley, P., Helmig, D., Klinger, L., Vierling, L., Zimmerman, P., and Geron, C.: Leaf, branch, stand and landscape scale measurements of volatile organic compound fluxes from US woodlands, Tree Physiology, 16(1–2), 17–24, 1996. Guenther, A., Baugh, B., Brasseur, G., Greenberg, J., Harley, P., Klinger, L., Serca, D., and Vierling, L.: Isoprene emission estimates and uncertainties for the Central African EXPRESSO study domain, J. Geophys. Res.-Atmos., 104(D23), 30 625–30 639, 1999a. Guenther, A., Archer, S., Greenberg, J., Harley, P., Helmig, D., Klinger, L., Vierling, L., Wildermuth, M., Zimmerman, P., and Zitzer, S.: Biogenic hydrocarbon emissions and landcover/climate change in a subtropical savanna, Phys. Chem. Earth Part B – Hydrology Oceans and Atmosphere, 24(6), 659–667, 1999b. Guenther, A., Geron, C., Pierce, T., Lamb, B., Harley, P., and Fall, R.: Natural emissions of non-methane volatile organic compounds; carbon monoxide, and oxides of nitrogen from North America, Atmos. Environ., 34(12–14), 2205–2230, 2000. Guenther, A. B. and Hills, A. J.: Eddy covariance measurement of isoprene fluxes, J. Geophys. Res., 103(D11), 13, 1998. Guenther, A.: The contribution of reactive carbon emissions from vegetation to the carbon balance of terrestrial ecosystems, Chemosphere, 49(8), 837–844, 2002. Hansen, M., DeFries, R., Townshend, J. R. G., and Sohlberg, R.: Global land cover classification at 1 km resolution using a decision tree classifier, Int. J. Remote Sens., 21, 1331–1365, 2000. Hansen, M., DeFries, R. S., Townshend, J. R. G., Carroll, M., Dimiceli, C., and Sohlberg, R. A.: Global Percent Tree Cover at a Spatial Resolution of 500 Meters: First Results of the MODIS Vegetation Continuous Fields Algorithm" Earth Interactions, 7(10), 1–15, 2003. Hanson, D. T. and Sharkey, T. D.: Rate of acclimation of the capacity for isoprene emission in response to light and temperature, Plant, Cell & Environment, 24(9), 937–946, 2001. Harley, P. C., Litvak, M. E., Sharkey, T. D., and Monson, R. K.: Isoprene Emission from Velvet Bean-Leaves – Interactions among Nitrogen Availability, Growth Photon Flux-Density, and Leaf Development, Plant Physiology, 105(1), 279–285, 1994. Harley, P., Vasconcellos, P., Vierling, L., Pinheiro, C., Greenberg, J., Guenther, A., Klinger, L., Almeida, S., Neill, D., Baker, T., Phillips, O., and Malhi, Y.: Variation in potential for isoprene emissions among Neotropical forest sites, Global Change Biology, 10, 630–650, 2004. Houweling, S., Dentener, F., and Lelieveld, J.: The impact of nonmethane hydrocarbon compounds on tropospheric photochemistry, J. Geophys. Res., 103, 10 673–10 696, 1998. Isebrands, J. G., Guenther, A. B., Harley, P., Helmig, D., Klinger, L., Vierling, L., Zimmerman, P., and Geron, C.: Volatile organic compound emission rates from mixed deciduous and coniferous forests in Northern Wisconsin, USA, Atmos. Environ., 33(16), 2527–2536, 1999. Isidorov, V.: Organic Chemistry of the Earth's Atmosphere, Springer-Verlag, Berlin, 1990. Janson, R., De Serves, C., and Romero, R.: Emission of isoprene and carbonyl compounds from a boreal forest and wetland in Sweden, Agric. For. Meteorol., 98–9, 671–681, 1999. Kanamitsu, M., Ebisuzaki, W., Woollen, J., Yang, S. K., Hnilo, J. J., Fiorino, M., and Potter, G. L.: NCEP-DOE AMIP-II reanalysis (R-2), Bull. Amer. Meteorol. Soc., 83(11), 1631–1643, 2002. Karl, T., Guenther, A., Spirig, C., Hansel, A., and Fall, R.: Seasonal variation of biogenic VOC emissions above a mixed hardwood forest in northern Michigan, Geophys. Res. Lett., 30(23), 2186, 2003. Karl, T., Potosnak, M., Guenther, A., Clark, D., Walker, J., Herrick, J. D., and Geron, C.: Exchange processes of volatile organic compounds above a tropical rain forest: Implications for modeling tropospheric chemistry above dense vegetation, J. Geophys. Res.-Atmos., 109(D18), D18306, doi:10.1029/2004JD004738, 2004. Keller, M. and Lerdau, M.: Isoprene emission from tropical forest canopy leaves, Global Biogeochem. Cycles, 13, 19–29, 1999. Kesselmeier, J., Kuhn, U., Wolf, A., Andreae, M. O., Ciccioli, P., Brancaleoni, E., Frattoni, M., Guenther, A., Greenberg, J., Vasconcellos, P. D., de Oliva, T., Tavares, T., and Artaxo, P.: Atmospheric volatile organic compounds (VOC) at a remote tropical forest site in central Amazonia, Atmos. Environ., 34(24), 4063–4072, 2000. Keppler, F., Hamilton, J. T. G., Braß, M., and Röckmann, T.: Methane emissions from terrestrial plants under aerobic conditions, Nature, 439, 187–191, doi:10.1038/nature04420, 2006. Kinnee, E., Geron, C., and Pierce, T.: United States land use inventory for estimating biogenic ozone precursor emissions, Ecological Applications, 7(1), 46–58, 1997. Kirstine, W., Galbally, I., Ye, Y., and Hooper, M.: Emissions of volatile organic compounds (primarily oxygenated species) from pasture, J. Geophys. Res., 103(D9), 10, 1998. Klein Goldewijk, K.: Estimating global land use change over the past 300 years: The HYDE database, Global Biogeochem. Cycles, 15(2), 417–433, 2001. Klinger, L., Zimmerman, P., Greenberg, J., Heidt, L., and Guenther, A.: Carbon trace gas fluxes along a successional gradient in the Hudson Bay lowland, J. Geophys. Res., 99, 1469–1494, 1994. Klinger, L. F., Li, Q. J., Guenther, A. B., Greenberg, J. P., Baker, B., and Bai, J. H.: Assessment of volatile organic compound emissions from ecosystems of China, J. Geophys. Res., 107(D21), 4603, doi:10.1029/2001JD001076, 2002. Kuhn, U., Rottenberger, S., Biesenthal, T., Wolf, A., Schebeske, G., Ciccioli, P., Brancaleoni, E., Frattoni, M., Tavares, T. M., and Kesselmeier, J.: Isoprene and monoterpene emissions of Amazonian tree species during the wet season: Direct and indirect investigations on controlling environmental functions, J. Geophys. Res.-Atmos., 107, 8071, 2002. Lamb, B., Allwine, E., Dilts, S., Westberg, H., Pierce, T., Geron, C., Baldocchi, D., Guenther, A., Klinger, L., Harley, P., and Zimmerman, P.: Evaluation of forest canopy models for estimating isoprene emissions, J. Geophys. Res., 101, 22 787–22 798, 1996. Leemans, R. and Cramer, W.: IIASA database for mean monthly values of temperature, precipitation, and cloudiness on a global terrestrial grid: Digital raster data on a 30 minute geographic (lat/long) 320 times 720 grid, in: Global ecosystems Database Version 1.0: Disc A, NOAA National Geophyscial Data Center, Boulder, CO, 1992. Leff, B., Ramankutty, N., and Foley, J. A.: Geographic distribution of major crops across the world, Global Biogeochem. Cycles, 18, GB1009, doi:10.1029/2003GB002108, 2004. Liepert, B. G.: Observed reductions of surface solar radiation at sites in the United States and worldwide from 1961 to 1990, Geophys. Res. Lett., 29(10), doi:10.1029/2002GLO14910, 2002. Makar, P., Fuentes, J., Wang, D., Staebler, R., and Wiebe, H.: Chemical processing of biogenic hydrocarbons within and above a temperate deciduous forest, J. Geophys. Res., 104(D3), 3581–3603, 1999. Martin, P. H. and Guenther, A. B.: Insights into the dynamics of forest succession and non-methane hydrocarbon trace gas emissions, J. Biogeography, 22, 493–499, 1995. Martin, R. V., Parrish, D. D., Ryerson, T. B., Nicks Jr., D. K., Chance, K., Kurosu, T. P., Fried, A., Wert, B. P., Jacob, D. J., and Sturges, E. D.: Evaluation of GOME satellite measurements of tropospheric NO₂ and HCHO using regional data from aircraft campaigns in the southeastern United States, J. Geophys. Res., 109, D24307, doi:10.1029/2004JD004869, 2004. Monson, R., Harley, P., Litvak, M., Wildermuth, M., Guenther, A., Zimmerman, P., and Fall, R.: Environmental and developmental controls over the seasonal pattern of isoprene emission from aspen leaves, Oecologia, 99, 260–270, 1994. Muller, J. F.: Geographical-Distribution and Seasonal-Variation of Surface Emissions and Deposition Velocities of Atmospheric Trace Gases, J. Geophys. Res.-Atmos., 97(D4), 3787–3804, 1992. Myneni, R. B., Nemani, R. R., and Running S. W.: Estimation of global leaf area index and absorped par using radiative transfer models, IEEE Trans. Geosci. Rem. Sens., 35, 1380–1393, 1997. Neilson, R. P.: A model for predicting continental-scale vegetation distribution and water balance, Ecological Applications, 5, 362–385, 1995. Olson, J.: World ecosystems (WE1.4): Digital raster data on a 10 minute geographic 1080×2160 grid, Global Ecosytems Database, Version 1.0: Disc A., N. G. D. Center, Boulder CO, Nat. Ocean. Atmos. Admin., 1992. Olson, D. M., Dinerstein, E., Wikramanayake, E. D., Burgess, N. D., Powell, G. V. N., Underwood, E. C., D'Amico, J. A., Itoua, I., Strand, H. E., Morrison, J. C., Loucks, C. J., Allnutt, T. F., Ricketts, T. H., Kura, Y., Lamoreux, J. F., Wettengel, W. W., Hedao, P., and Kassem, K. R.: Terrestrial Ecoregions of the World: A New Map of Life on Earth., BioScience, 51(11), 933–938, 2001. Otter, L., Guenther, A., Wiedinmyer, C., Fleming, G., Harley, P., and Greenberg, J.: Spatial and temporal variations in biogenic volatile organic compound emissions for Africa south of the equator, J. Geophys. Res., 108(13), doi:10.1029/2002JD002609, 2003. Palmer, P. I., Jacob, D. J., Chance, K., Martin, R. V., Spurr, R. J. D., Kurosu, T. P., Bey, I., Yantosca, R., Fiore, A., and Li, Q. B.: Air mass factor formulation for spectroscopic measurements from satellites: Application to formaldehyde retrievals from the Global Ozone Monitoring Experiment, J. Geophys. Res., 106, 14 539–14 550, 2001. Palmer, P. I., Jacob, D. J., Fiore, A. M., Martin, R. V., Chance, K., and Kurosu, T. P.: Mapping isoprene emissions over North America using formaldehyde column observations from space, J. Geophys. Res., 108(D6), 4180, doi:10.1029/2002JD002153, 2003. Palmer, P., Abbot, D., Fu, T.-M., Jacob, D., Chance, K., Kurosu, T., Guenther, A., Wiedinmyer, C., Stanton, J., Pilling, M., Pressley, S., Lamb, B., and Sumner, A.: Quantifying the seasonal and interannual variability of North American isoprene emissions using satellite observations of formaldehyde column, J. Geophys. Res., in press, 2006. Pegoraro, E., Rey, A., Bobich, E., Barron-Gafford, G., Grieve, A., Malhi, Y., and Murthy, R.: Effect of CO2 concentration and vapour pressure deficit on isoprene emission from leaves of \textitPopulus deltoides during drought, Functional Plant Biology, 31(12), 1137–1147, 2004. Petron, G., Harley, P., Greenberg, J., and Guenther, A.: Seasonal temperature variations influence isoprene emission, Geophys. Res. Lett., 28 (9), 1707–1710, 2001. Pierce, T. E. and Waldruff, P. S.: Pc-Beis – a Personal-Computer Version of the Biogenic Emissions Inventory System, J. Air Waste Manage. Assoc., 41(7), 937–941, 1991. Pierce, T., Geron, C., Bender, L., Dennis, R., Tonnesen, G., and Guenther, A.: Influence of increased isoprene emissions on regional ozone modeling, J. Geophys. Res.-Atmos., 103(D19), 25 611–25 629, 1998. Poisson, N., Kanakidou, M., and Crutzen, P. J.: Impact of non-methane hydrocarbons on tropospheric chemistry and the oxidizing power of the global troposphere: 3-dimensional modelling results, J. Atmos. Chem., 36, 157–230, 2000. Ramankutty, N. and Foley, J. A.: Estimating historical changes in land cover: North American croplands from 1850 to 1992, Global Ecology and Biogeography, 8, 381–396, 1999. Rapparini, F., Baraldi, R., Miglietta, F., and Loreto, F.: Isoprenoid emission in trees of \textitQuercus pubescens and \textitQuercus ilex with lifetime exposure to naturally high CO2 environment, Plant, Cell and Environment, 27, 381–391, 2004. Rasmussen, R. and Went, F.: Volatile organic material of plant origin in the atmosphere, Proc. Natl. Acad. Sci., 53, 215–220, 1965. Rosenstiel, T. N., Potosnak, M. J., Griffin, K. L., Fall, R., and Monson, R. K.: Increased CO2 uncouples growth from isoprene emission in an agriforest ecosystem, Nature, 421, 256–259, 2003. Sanadze, G.: The nature of gaseous substances emitted by leaves of Robinia pseudoacacia, Soobshch. Akad. Nauk Gruz. SSR, 27, 747–750, 1957. Sanderson, M. G., Jones, C. D., Collins, W. J., Johnson, C. E., and Derwent, R. G.: Effect of climate change on isoprene emissions and surface ozone levels, Geophys. Res. Lett., 30(18), 1936, 2003. Schaab, G., Steinbrecher, R., Lacaze, B., and Lenz, R.: Assessment of long-term vegetation changes on potential isoprenoid emission for a Mediterranean-type ecosystem in France, J. Geophys. Res.-Atmos., 105(D23), 28 863–28 873, 2000. Sharkey, T. D., Singsaas, E. L., Lerdau, M. T., and Geron, C.: Weather effects on isoprene emission capacity and applications in emissions algorithms, Ecol. Appl., 9, 1132–1137, 2000. Shim, C., Wang, Y., Choi, Y., Palmer, P., Abbot, D., Chance, K.: Constraining global isoprene emissions with Global Ozone Monitoring Experiment (GOME) formaldehyde column measurements, J. Geophys. Res., 110, D24301, doi:10.1029/2004JD005629, 2005. Silver, G. M. and Fall, R.: Characterization of Aspen Isoprene Synthase, an Enzyme Responsible for Leaf Isoprene Emission to the Atmosphere, J. Biological Chemistry, 270(22), 13 010–13 016, 1995. Simpson, D., Winiwarter, W., Borjesson, G., Cinderby, S., Ferreiro, A., Guenther, A., Hewitt, C. N., Janson, R., Khalil, M. A. K., Owen, S., Pierce, T. E., Puxbaum, H., Shearer, M., Skiba, U., Steinbrecher, R., Tarrason, L., and Oquist, M. G.: Inventorying emissions from nature in Europe, J. Geophys. Res.-Atmos., 104(D7), 8113–8152, 1999. Strong, C., Fuentes, J. D., and Baldocchi, D.: Reactive hydrocarbon flux footprints during canopy senescence, Agric. For. Meteorol., 127(3–4), 159–173, 2004. Stroud, C., Makar, P., Karl, T., Guenther, A., Geron, C., Turnipseed, A., Nemitz, E., Baker, B., Potosnak, M., and Fuentes, J.: Role of Canopy-Scale Photochemistry in Modifying Biogenic-Atmosphere Exchange of Reactive Terpene Species: Results from the CELTIC Field Study, J. Geophys. Res., 110, D17303, doi:10.1029/2005JD005775, 2005. Tian, Y., Dickinson, R. E., Zhou, L., Myneni, R. B., Friedl, M., Schaaf, C. B., Carroll, M., and Gao, F.: Land boundary conditions from MODIS data and consequences for the albedo of a climate model, Geophys. Res. Lett., 31(5), L05504, doi:1029/2003GL019104, 2004. Trostdorf, C., Gatti, L., Yamazaki, A., Martins, W., Potosnak, M., Guenther, A., Martins, W., and Munger, J.: Seasonal cycles of isoprene concentrations in the Amazonian rainforest, Atmos. Chem. Phys. Discuss., 4, 1291–1310, 2004. Turner, D. P., Baglio, J. V., Wones, A. G., Pross, D., Vong, R., Mcveety, B. D., and Phillips, D. L.: Climate change and Isoprene emissions from vegetation, Chemosphere, 23, 37–56, 1991. Velikova, V., Pinelli, P., Pasqualini, S., Reale, L., Ferranti, F., and Loreto, F.: Isoprene decreases the concentration of nitric oxide in leaves exposed to elevated ozone, New Phytologist, 166(2), 419–426, 2005. Wagner, W., Nemecek-Marshall M., and Fall, R.: Three Distinct Phases of Isoprene Formation during Growth and Sporulation of Bacillus subtilis, J. Bacteriology, 181(15), 4700–4703, 1999. Wang, Y. and Jacob, D. J.: Anthropogenic forcing on tropospheric ozone and OH since preindustrial times, J. Geophys. Res., 103, 31 123–31 135, 1998. Went, F. W.: Blue hazes in the atmosphere, Nature, 187(4738), 641–643, 1960. Wert, B. P., Trainer, M., Fried, A., Ryerson, T. B., Henry, B., Potter, W., Angevine, W. M., Atlas, E., Donnelly, S. G., Fehsenfeld, F. C., Frost, G. J., Goldan, P. D., Hansel, A., Holloway, J. S., Hubler, G., Kuster, W. C., Nicks, D. K., Neuman, J. A., Parrish, D. D., Schauffler, S., Stutz, J., Sueper, D. T., Wiedinmyer, C., and Wisthaler, A.: Signatures of terminal alkene oxidation in airborne formaldehyde measurement during TexAQS 2000, J. Geophys. Res., 108(D3), 4104, doi:10.1029/2002JD002502, 2003. Wiedinmyer, C., Guenther, A., Harley, P., Hewitt, C. N., Geron, C., Artaxo, P., Steinbrecher, R., and Rasmussen, R.: Global organic emissions from vegetation, in: Emissions of Atmospheric Trace Compounds, edited by: Granier, C., Kluwer Publishing Co., Dordrecht, The Netherlands, 2004. Wiedinmyer, C., Tie, X., Guenther, A., Neilson,, R., and Granier, C.: Future Changes in Biogenic Isoprene Emissions: How Might They Affect Regional and Global Atmospheric Chemistry?, Earth Interact., 10(3), EI174, doi:10.1175/EI174.1, 2006. Wolfertz, M., Sharkey, T. D., Boland, W., Kuhnemann, F., Yeh, S., and Weise, S. E.: Biochemical regulation of isoprene emission, Plant Cell and Environment, 26(8), 1357–1364, 2003. Zeng, X.: Global Vegetation Root Distribution for Land Modeling, J. Hydrometeorol., 2(5), 525–530, 2001. Zhang, P. Anderson, B., Barlow, M., Tan, B., and Myneni, R.: Climate related vegetation characteristics derived from MODIS LAI and NDVI, J. Geophys. Res., 109, D20105, doi:10.1029/2004JD004720, 2004. Zimmerman, P.: Testing of hydrocarbon emissions from vegetation, leaf litter and aquatic surfaces and development of a method for compiling biogenic emission inventories, EPA-450-4-70-004, U.S. Environmental Protection Agency, Research Triangle Park, NC, 1979.