## Effects of Elevated Atmospheric $CO_2$ Concentrations on Soil Microorganisms 

**The journal of microbiology** v.42 no.4 , 2004년, pp.267 - 277 

Freeman Chris  (School of Biological Sciences, University of Wales ) ; Kim Seon-Young  ( Department of Environmental Science and Engineering, Ewha Womans University ) ; Lee Seung-Hoon  ( Department of Environmental Science and Engineering, Ewha Womans University ) ; Kang Hojeong ( Department of Environmental Science and Engineering, Ewha Womans University) 

###### Abstract  


Effects of elevated $CO_2$ on soil microorganisms are known to be mediated by various interactions with plants, for which such effects are relatively poorly documented. In this review, we summarize and syn­thesize results from studies assessing impacts of elevated $CO_2$ on soil ecosystems, focusing primarily on plants and a variety the of microbial processes. The processes considered include changes in microbial biomass of C and N, microbial number, respiration rates, organic matter decomposition, soil enzyme activities, microbial community composition, and functional groups of bacteria mediating trace gas emission such as methane and nitrous oxide. Elevated $CO_2$ in atmosphere may enhance certain micro­bial processes such as $CH_4$ emission from wetlands due to enhanced carbon supply from plants. How­ever, responses of extracellular enzyme activities and microbial community structure are still controversy, because interferences with other factors such as the types of plants, nutrient availabilitial in soil, soil types, analysis methods, and types of $CO_2$ fumigation systems are not fully understood.

#### 주제어

#microbial process  #trace gas emission  #soil enzyme activity  #microbial community structure 

#### 참고문헌 (121)

  1. Arnone, J.A. and C. Korner. 1995. Soil and biomass carbon pools in model communities of tropical plants under elevated CO2. Oecologia 104, 61-71 
  2. Ball, A.S. and B.G. Drake. 1998. Stimulation of soil respiration by carbon dioxide enrichment of marsh vegetation. Soil Biol. Biochem. 1203-1205 
  3. Barnard, R., L. Barthes, X. Le Roux, H. Harmens, A. Raschi, J.F. Soussana, B. Winkler, and P.W. Leadley. 2004a. Atmospheric CO2 elevation has little effect on nitrifying and denitrifying enzyme activity in four European grasslands. Glob. Change Biol. 10, 488-497 
  4. Barnard, R., L. Barthes, X. Le Roux, and P.W. Leadley. 2004b. Dynamics of nitrifying activities, denitrifying activities and nitrogen in grassland mesocosms as altered by elevated CO2. New Phytol. 162, 365-376 
  5. Curtis, P.S., D.R. Zak, K.S. Pregitzer, and J.A. Teeri. 1994b. Above and below ground response of Populus grandidentata to elevated atmospheric CO2 and soil N availability. Plant Soil 165, 45-51 
  6. Day, F.P., E.P. Weber, C.R. Hinkle, and B.G. Drake. 2000. Effects of elevated CO2 on fine root length and distribution in an oakpalmetto scrub ecosystem in central Florida. Global Change Biol. 2, 143-148 
  7. Diaz, S., J.P. Grime, J. Harris, and E. McPherson. 1993. Evidence of a feedback mechanism limiting plant response to elevated carbon dioxide. Nature 364, 616-617 
  8. Fitter, H., J.D. Graves, J. Wolfenden, G.K. Self, T.K. Brown, D. Bogie, and T.A. Mansfield. 1997. Root production and turnover and carbon budgets of two contrasting grasslands under ambient and elevated atmospheric carbon dioxide concentrations. New Phytol. 137, 247-255 
  9. Gorissen, A., J.H. van Ginkel, J.J.B. Keurentjes, and J.A. van Veen. 1995. Grass root decomposition in retarded when grass has been grown under elevated CO2. Soil Biol. Biochem. 27, 117-120 
  10. Griffiths, B.S., K. Ritz, R.D. Bardgett, R. Cook, S. Christensen, F. Ekelund, S.J. Sørensen, E. Bååth, J. Bloem, P.C. de Ruiter, J. Dolfing, and B. Nicolardot. 2000. Ecosystem response of pasture communities to fumigation-induced microbial diversity reductions: an examination of the biodiversity-ecosystem function relationship. Oikos 90, 279-294 
  11. Hungate, B.A., P. Dijkstra, D.W. Johnson, C.R. Hinkle, and B.G. Drake. 1999. Elevated CO2 increases nitrogen fixation and decreases soil nitrogen mineralization in Florida scrub oak. Global Change Biol. 5, 781-789 
  12. Ineichen, K., V. Wiemken, and A. Wiemken. 1995. Shoots, roots and ectomycorrhizal formation of pine seedlings at elevated atmospheric carbon dioxide. Plant Cell Environ. 18, 703-707 
  13. Insam, H., K. Amor, M. Renner, and C. Crepaz. 1996. Changes in the functional abilities of the microbial community during composting of manure. Microb. Ecol. 31, 77-87 
  14. Jongen, M., M.B. Jones, T. Hebeisen, H. Blum, and G.R. Hendrey. 1995. The effects of elevated CO2 concentrations on the root growth of Lolium perenne and Trifolium repens grown in a FACE system. Global Change Biol. 1, 361-371 
  15. Kampichler, C., E. Kandeler, R.D. Bardgett, T.H. Jones, and J. Thompson. 1998. Impact of elevated atmospheric CO2 concentration on soil microbial biomass and activity in a complex, weedy field model ecosystem. Global Change Biol. 4, 335-346 
  16. Körner, C., M. Diemer, B. Schappi, P.A. Niklaus, and J.A. Arnone. 1997. The responses of alpine grassland to four seasons of CO2 enrichment: a synthesis. Acta Oecol. 18, 165-176 
  17. Matamala, R. and B.G. Drake. 1999. The influence of atmospheric CO2 enrichment on plant-soil nitrogen interactions in a wetland plant community on the Chesapeake Bay. Plant Soil 210, 93-101 
  18. Niklaus, P.A., M. Wohlfender, R. Siegwolf, and C. Körner. 2001. Effects of six years atmospheric CO2 enrichment on plant, soil, and soil microbial C of a calcareous grassland. Plant Soil 233, 189-202 
  19. O'Neill, E.G., R.J. Luxmoore, and R.J. Norby. 1987a. Elevated atmospheric CO2 effects on seedling growth, nutrient uptake, and rhizosphere bacterial populations of Liriodendron tulipifera L. Plant Soil 104, 3-11 
  20. O'Neill, E.G., R.J. Luxmoore, and R.J. Norby. 1987b. Increases in mycorrhizal colonization and seedling growth in Pinus echinata and Quercus alba in an enriched CO2 atmosphere. Can. J. For. Res. 17, 878-883 
  21. Paterson, E., J.M. Hall, E.A.S. Rattray, B.S. Griffiths, K. Ritz, and K. Killham. 1997. Effect of elevated CO2 on rhizosphere carbon flow and soil microbial processes. Global Change Biol. 3, 363-377 
  22. Rice, C.W., J.L. Halvin, and J.S. Schepers. 1995. Rational nitrogen fertilization in intensive cropping systems. Fertil. Res. 42, 89-97 
  23. Rogers, H.H., S.A. Prior, and E.G. ONeill. 1992. Cotton root and rhizosphere responses to free-air CO2 enrichment. Crit. Rev. Plant Sci. 11, 251-263 
  24. Runion, G.B., E.A. Curl, H.H. Rogers, P.A. Backman, R. Rodriguez-Kabana, and B.E. Helms. 1994. Effects of free-air CO2 enrichment on microbial on microbial populations in the rhizosphere and phyllosphere of cotton. Agric. For. Meteorol. 70, 117-130 
  25. Sass, R.L., F.M. Fisher, P.A. Harcombe, and F.T. Turner. 1990. Methane production and emission in a Texas rice field. Global Biogeochem. Cycles 4, 47-68 
  26. Schrope, M.K., J.P. Chanton, L.H. Allen, and J.T. Baker. 1999. Effect of CO2 enrichment and elevated temperature on methane emissions from rice, Oryza sativa. Global Change Biol. 5, 587-599. 
  27. Wang, B. and K. Adachi. 1999. Methane Production in a flooded soil in response to elevated atmospheric carbon dioxide concentrations. Biol. Fertil. Soils 29, 218-220 
  28. Wiemken, V., E. Laczko, K. Ineichen, and T. Boller. 2001. Effects of elevated carbon dioxide and nitrogen fertilization on mycorrhizal fine roots and the soil microbial community in Beech-Spruce ecosystems on siliceous and calcareous soil. Microb. Ecol. 42, 126-135 
  29. Williams, M.A., C.W. Rice, and C.E. Owensby. 2000. Carbon dynamics and microbial activity in tallgrass prairie exposed to elevated $CO_2$ for 8 years. Plant Soil 227, 127-137 
  30. Curtis, P.S., E.G. O'Neill, J.A. Teeri, P.R. Zak, and K.S. Pregitzer. 1994a. Below ground responses to rising atmospheric CO2 : implications for plants, soil biota and ecosystem processes. Plant Soil 165, 1-6 
  31. Griffiths, B.S., K. Ritz, N. Ebblewhite, E. Paterson, and K. Killham. 1998. Ryegrass rhizosphere microbial community structure under elevated carbon dioxide concentrations, with observations on wheat rhizosphere. Soil Biol. Biochem. 30, 315-321 
  32. Rice, C.W., F.O. Garcia, C.O. Hampton, and C.E. Owensby. 1994. Soil microbial response in tall grass prairie to elevated CO2. Plant Soil 165, 67-74 
  33. Sadowsky, M.J. and M. Schortemeyer. 1997. Soil microbial responses to increased concentrations of atmospheric CO2. Global Change Biol. 3, 217-224 
  34. Foissner, W. 1999. Soil protozoa as bioindicators: pros and cons, methods, diversity, representative examples. Agric. Ecosyst. Environ. 74, 95-112 
  35. Kaplan, W., I. Valiela, and J.M. Teal. 1979. Denitrification in a salt marsh ecosystem. Limn. Ocean. 24, 726-734 
  36. Saarnio, S. and J. Silvola. 1999. Effects of increased CO2 and N on CH4 efflux from a boreal mire: a growth chamber experiment. Oecologia 119, 349-356 
  37. Cotrufo, M.F. and P. Ineson. 1995. Effects of enhanced atmospheric CO2 and nutrient supply on the quality and subsequent decomposition of the fine roots of Betula pendula Roth. and Picea sitchensis (Bong.) Carr. Plant Soil 170, 267-277 
  38. Drake, B.G. 1992. A field study of the effects of elevated CO2 on ecosystem processes in a Chesapeake Bay wetland. Aust. J. Bot. 40, 579-595 
  39. van de Geijn, S.C. and J.A. van Veen, 1993. Implications of increased carbon dioxide levels for carbon input and turnover in soils. Vegetatio. 104-105, 283-292 
  40. Whiting, G.J. and J. Chanton. 1992. Plant-dependent CH4 emission in a subarctic Canadian Fen. Global Biogeochem. Cycles 6, 225-231 
  41. Zak, D.R., K.S. Pregitzer, P.S. Curtis, and W.E. Holmes. 2000b. Atmospheric $CO_2$ and the composition and function of soil microbial communities. Ecol. Appl. 10, 47-59 
  42. Lewis, J.D. and B.R. Strain. 1996. The role of mycorrhizas in the response of Pinus taeda seedlings to elevated CO2. New Phytol. 133, 431-443 
  43. Pregitzer, K.S., D.R. Zak, J. Maziasz, J. DeForest, P.S. Curtis, and J. Lussenhop. 2000. Interactive effects of atmospheric CO2 and soil-N availability on fine roots of Populus tremuloides. Ecol. Appl. 10, 18-13 
  44. Runion, G.B., R.J. Mitchell, H.H. Rogers, S.A. Prior, and T.K. Counts. 1997. Effects of nitrogen and water limitation and elevated atmospheric CO2 on ectomycorrhiza of longleaf pine. New Phytol. 137, 681-689 
  45. Whipps, J.M. 1985. Effects of CO2 -concentrations on growth, carbon distribution and loss of carbon from the roots of maize. J. Exp. Bot. 36, 645-651 
  46. Lekkerkerk, L.J.A., S.C. van de Geijn, and J.A. van Veen. 1990. Effects of elevated atmospheric CO2-levels on the carbon economy of a soil planted with wheat, p. 423-429. In A.F. Bouwman (ed.), Soils and the Greenhouse Effect, John Wiley and Sons, New York 
  47. Dacey, V.W.H., B.G. Drake, and M.J. Klug. 1994. Stimulation of methane emission by carbon dioxide enrichment of marsh vegetation. Nature 370, 47-49 
  48. IPCC (Intergovernmental Panel on Climate Change). 1995. Climate Change 1994, p. 7-34. Cambridge University Press, Cambridge, UK 
  49. Marilley, L., G. Vogt, M.P. Blanc, and M. Aragno. 1998. Bacterial diversity in the bulk soil and rhizosphere fractions of Lolium perenne and Trifolium repens as revealed by PCR restriction analysis. Plant Soil 198, 219-224 
  50. Megonigal, J.P. and W.H. Schlesinger. 1997. Enhanced CH4 emissions from a wetland soil exposed to Elevated CO2.Biogeochemistry 37, 77-88 
  51. Ringelberg, D.B., J.O. Stair, J.S. Alameida, R.J. Norby, E.G. O'Neill, and D.C. White. 1997. Consequences of rising atmospheric carbon dioxide levels for the belowground microbiota associated with white oak. J. Environ. Qual. 26, 409-503 
  52. Hungate, B.A., C.H. Jaeger III, G. Gamara, S.F. Chapin II, and C.B. Field. 2000. Soil microbiota in two annual grasslands: Responses to elevated atmospheric CO2. Oecologia 124, 589-598 
  53. Cotrufo, M.F., P. Ineson, and A.P. Rowland. 1994. Decomposition of tree leaf litters grown under elevated CO2: Effect of litter quality. Plant Soil 163, 121-130 
  54. Deiglmayr, K., L. Philippot, U.A. Hartwig, and E. Kandeler. 2004. Structure and activity of the nitrate-reducing communityin the rhizosphere of Lolium perenne and Trifolium repens under long-term elevated atmospheric p CO2. FEMS Microbiol. Ecol. 49, 445-454 
  55. Tuchman, N.C., K.A. Wahtera, R.G. Wetzel, and J.A. Teeri. 2003. Elevated atmospheric CO2 alters leaf litter nutritional quality for stream ecosystems: An in situ leaf decomposition study. Hydrobiologia 495, 203-211 
  56. Zak, D.R., K.S. Pregitzer, P.S. Curtis, J.A. Teeri, R. Fogel, and D.L. Randlett. 1993. Elevated atmospheric $CO_2$ and feedback between carbon and nitrogen cycles. Plant Soil 151, 105-117 
  57. Rogers, H.H., G.B. Runion, and S.V. Krupa. 1994. Plant responses to atmospheric CO2 enrichment with emphasis on roots and the rhizosphere. Environ. Pollut. 83, 155-189 
  58. Allen, L.H. Jr., S.L. Albrecht, W. Colon, and S.A. Covell. 1994. Effects of carbon dioxide and temperature on methane emission of rice. Int. Rice Research Notes 19, 43 
  59. Baggs, E.M., M. Richter, G. Cadisch, and U.A. Hartwig. 2003. Denitrification in grass swards is increased under elevated atmospheric CO2. Soil Biol. Biochem. 35, 729-732 
  60. Larson, J.L., D.R. Zak, and R.L. Sinsabaugh. 2002. Extracellular enzyme activity beneath temperature trees growing under elevated carbon dioxide and ozone. Soil Sci. Soc. Am. J. 66, 1848-1856 
  61. Berntson, G.M. and F.A. Bazzaz. 1998. Regenerating temperate forest mesocosms in elevated CO2: belowground growth and nitrogen cycling. Oecologia 113, 115-125 
  62. Billings, S.A, S.M. Schaeffer, S. Zitzer, and R.D. Evans. 2003. Trace N gas losses and N mineralization in an intact Mojave Desert ecosystem with elevated CO2. Soil Biol. Biochem. 34, 1777-1784 
  63. Cardon, Z.G. 1996. Influence of rhizodeposition under elevated CO2 on plant nutrition and soil organic matter. Plant Soil. 187, 277-288 
  64. Mooney, H.A., J. Canadell, F.S. Chapin, J.R.III Ehleringer, C. Körner, R.E. McMurtrie, W.J. Parton, L.F. Pitelka, and E-D. Schulze. 1999. Ecosystem physiology responses to global change, p. 141-189. In B. Walker, W. Steffen, J. Canadell, and J. Ingram (eds), The terrestrial biosphere and global change, Cambridge University Press, Cambridge, UK 
  65. Rouhier, H., G. Billes, A. El Kohen, M. Mousseau, and P. Bottner. 1994. Effect of elevated CO2 on carbon and nitrogen distribution within a tree (Castanea sativa Mill.)-soil system. Plant Soil 162, 281-292 
  66. Schortemeyer, M., P. Dijkstra, D.W. Johnson, and B.G. Drake. 2000. Effects of elevated atmospheric CO2 concentration on C and N pools and rhizosphere processes in a Florida scrub oak community. Global Change Biol. 6, 383-391 
  67. Zanetti, S., U.A. Hartwig, A. Luscher, T. Hebeisen, M. Frehner, B.U. Fischer, G.R. Hendrey, H. Blum, and J. Nosberger. 1996. Stimulationof symbiotic $N_2$ fixation in Trifolium repens L. under elevated atmospheric $pCO_2$ in a grassland ecosystem. Plant Physiol. 112, 575-583 
  68. Arnone III, J.A. and G. Hirschel. 1997. Does fertilizer application alter the effects of elevated CO on Carex leaf litter quality and in situ decomposition in an alpine grassland? Acta Oecol. 18, 201-206 
  69. Curtis, P.S. and X. Wang. 1998. A meta-analysis of elevated CO2 effects on woody plant mass, form, and physiology. Oecologia 113, 299-313 
  70. Hirschel, G., C.H. Körner, and J.A.III Arnone. 1997. Will rising atmospheric CO2 affect leaf litter quality and in situ decomposition rates in native plant communities? Oecologia 110, 387-392 
  71. Kattenburg, A., F. Giorgi, H. Grassl, G.A. Meehl, J.B.F. Mitchell, R.J. Stouffer, T. Tokioka, A.J. Weaver, and T.M.L. Wigley. 1995. Climate models-projections of future climate, p. 290-349. In J.T. Houghton, L.G. Meira Fiho, B.A. Callander, N. Harris, A. Kattenburg, and K, Maskell (eds.), Intergovernmental Panel on Climate Change. Cambridge University Press, New York 
  72. Poorter, H. 1993. Interspecific variation in the growth response of plants to an elevated ambient CO2 concentration. Vegetatio. 104/105, 77-97 
  73. Adams, J.M. and H. Faure. 1998. A new estimate of changing carbon storage on land since the last glacial maximum, based on global land ecosystem reconstruction. Global Planet. Change 16-17, 3-241 
  74. Cheng, W.X. 1999. Rhizosphere feedbacks in elevated CO2. Tree Physiol. 19, 313-320 
  75. Garland, J. and A. Mills. 1991. Classification and characterization of heterotrophic microbial communities on the basis of patterns of community-level sole-carbon-source utilization. Appl. Environ. Microbiol. 57, 2351-2359 
  76. Kennedy, A.C. 1999. Bacterial diversity in agroecosystems. Agric. Ecosyst. Environ. 74, 65-76 
  77. Niklaus, P.A. and C. Körner. 1996. Responses of soil microbiota of a late successional alpine grassland to long term CO2 enrichment. Plant Soil 184, 219-229 
  78. Wallenda, T. and I. Kottke. 1998. Nitrogen deposition and ectomycorrhizas. New Phytol. 139, 169-187 
  79. Zak, D.R., K.S. Pregitzer, J.S. King, and W.E. Holmes. 2000a. Elevated atmospheric $CO_2$, fine roots and the response of soil microorganisms: A review and hypothesis. New Phytol. 147, 201-222 
  80. Zak, J.C., M.R. Willig, D.L. Moorehead, and H.G. Wildman. 1994. Functional diversity of microbial communities: a quantitative approach. Soil Biol. Biochem. 26, 1101-1108 
  81. Klamer, M., M.S. Roberts, L.H. Levine, B.G. Drake, and J.L. Garland. 2002. Influence of Elevated CO2 on the Fungal Community in a Coastal Scrub Oak Forest Soil Investigated with Terminal-Restriction Fragment Length Polymorphism Analysis. Appl. Environ. Microbiol. 68, 4370-4376 
  82. Körner, C. 1996. The response of complex multispecies systems to elevated CO2, p. 20-42. In B.H. Walker and W.L. Steffen (eds.), Global change and terrestrial ecosystems, Cambridge University Press, Cambridge, UK 
  83. Mitchell, E.A.D., D. Gilbert, A. Buttler, C. Amblard, P. Grosbernier, and J.M. Gobat. 2003. structure of microbial communities in Sphagnum peatlands and effect of atmospheric carbon dioxide enrichment. Microb. Ecol. 46, 187-199 
  84. Montealegre, C.M., C. van Kessel, J.M. Blumenthal, H.G. Hur, U.A. Hartwig, and M.J. Sadowsky. 2000. Elevated atmospheric CO2 alters microbial structure in a pasture ecosystem. Global Change Biol. 6, 475-482 
  85. Saarnio, S., T. Saarinen, H. vasander, and J. Silvola. 2000. A moderate increase in the annual CH4 efflux by raised CO2 or NH4NO3 supply in a boreal oligotrophic mire. Global Change Biol. 6, 137-144 
  86. Whiting, G.J., J. Chanton, D. Bartlett, and J. Happell. 1991. Methane Flux, net primary productivity and biomass relationships in a Subtropical grassland community. J. Geophys. Res. 96, 13067-13071 
  87. Hebeisen, T., A. Lüscher, S. Zanetti, B.U. Fischer, U.A. Hartwig, M. Frehner, G.R. Hendrey, H. Blum, and J. Nösberger. 1997. Growth response of Trifolium repens and Lolium perenne as monocultures and bi-species mixture to free air CO2 enrichment and management. Global Change Biol. 3, 149-160 
  88. Dakora, F.D. and B.G. Drake. 2000. Elevated CO2 stimulates associative N2 fixation in a C3 plant of the Chesapeake Bay wetland. Plant Cell Environ. 23, 943-953 
  89. Edwards, N.T. and R.J. Norby. 1999. Below-ground respiratory response of sugar maple and red maple saplings to atmospheric CO2 enrichment and elevated air temperature. Plant Soil 206, 85-97 
  90. Freeman, C., R. Baxter, J.F. Farrar, S.E. Jones, S. Plum, T.W. Ashendon, and C. Stirling. 1998. Could competition between plants and microbes regulate plant nutrition and atmospheric CO2 concentrations? Sci. Total Environ. 220, 181-184 
  91. Gorham, E. 1991. Northern peatlands: role in the carbon cycle and probable responses to climatic warming. Ecol. Appl. 1, 182-195 
  92. Hutchin, P.R., M.C. Press, J.A. Lee, and T.W. Ashenden. 1995. Elevated concentrations of CO2 may double methane emissions from mires. Global Change Biol. 1, 25-128 
  93. Kang, H.J., C. Freeman, and T.W. Ashendon. 2001. Effects of elevated CO2 on fen peat biogeochemistry. Sci. Total Environ. 279, 45-50 
  94. Walker, R.F., D.R. Geisinger, D.W., Johnson, and J.T. Ball. 1997. Elevated atmospheric CO2 and soil N fertility effects on growth, mycorrhizal colonization, and xylem water potential of juvenile ponderosa pine in a field soil. Plant Soil 195, 25-36 
  95. Dhillion, S.S., J. Roy, and M. Abrams. 1996. Assessing the impact of elevated CO2 on soil microbial activity in a Mediterranean model ecosystem. Plant Soil 187, 333-342 
  96. Insam, H., E. Bååth, M. Berreck, A. Frostegård, M.H. Gerzabek, A. Kraft, F. Schinner, P. Schweiger, and G. Tschuggnall. 1999. Responses of the soil microbiota to elevated CO2 in an artificial tropical ecosystem. J. Microbiol. Methods 36, 45-54 
  97. Mayr, C., M. Miller, and H. Insam. 1999. Elevated CO2 alters community-level physiological profiles and enzyme activities in alpine grassland. J. Microbiol. Methods. 36, 35-43 
  98. Norby, R.J. 1994. Issues and perspectives for investigating root responses to elevated atmospheric carbon dioxide. Plant Soil 165, 9-20 
  99. Rogers, A., B.U. Fischer, J. Bryant, M. Frehner, H. Blum, C.A. Raines, and S.P. Long. 1998. Acclimation of photosynthesis to elevated CO2 under low-nitrogen nutrition is affected by the capacity for assimilate utilization. Perennial ryegrass under free-air CO2 enrichment. Plant Physiol. 118, 683-689 
  100. Ball, A.S. 1997. Microbial decomposition at elevated CO2 levels: effect of litter quality. Glob. Change Biol. 3, 379-386 
  101. Jones, T.H., L.J. Thompson, J.H. Lawton, T.M. Bezemer, R.D. Bardgett, T.M. Blackburn, K.D. Bruce, P.F. Canon, G.S. Hall, S.E. Harley, G. Howson, C.G. Hones, C. Kampichler, E. Kandler, and D.A. Richie. 1998. Impacts of rising atmospheric carbon dioxide on model terrestrial ecosystems. Science 280, 441- 443 
  102. Marilley, L., U.A. Hartwig, and M. Aragno. 1999. Influence of an elevated atmospheric CO2 content on soil and rhizosphere bacterial communities beneath Lolium perenne and Trifolium repens under field conditions. Microb. Ecol. 38, 39-49 
  103. van Veen, J.A., E. Liljeroth, L.J.A. Lekkerkerk, and S.C. van de Geijn. 1991. Carbon fluxes in plantsoil systems at elevated atmospheric CO2 levels. Ecol. Appl. 1, 175-181 
  104. Billings, S.A., S.M. Schaeffer, and R.D. Evans. 2004. Soil microbial activity and N availability with elevated CO2 in Mojave Desert soils. Global Biogeochem. Cycles. 18, GB1011 
  105. Lewis, J.D., R.B. Thomas, and B.R. Strain. 1994. Effect of elevated CO2 on mycorrhizal colonizination of loblolly pine (Pinus taeda L.) seedlings. Plant Soil 165, 81-88 
  106. Moorhead, D.L. and A.E. Linkins. 1997. Elevated CO2 alters belowground exoenzyme activities in tussock tundra. Plant Soil 189, 321-329 
  107. Zak, D.R., D.B. Ringelberg, K.S. Pregitzer, D.L. Randlett, D.C. White, and P.S. Curtis. 1996. Soil microbial communities beneath Populus granddentata grown under elevated atmospheric $CO_2$. Ecol. Appl. 6, 57-262 
  108. Montealegre, C.M., C. van Kessel, M.P. Russelle, and M.J. Sadowsky. 2002. Changes in microbial activity and composition in a pasture ecosystem exposed to elevated atmospheric carbon dioxide. Plant Soil 243, 197-207 
  109. Robinson, D. and J.P. Conroy. 1999. A possible plant-mediated feedback between elevated CO2, denitrification and the enhanced greenhouse effect. Soil Biol. Biochem. 31, 43-53 
  110. Roulet, N., T. Moore, and P. Lafleur. 1992. Northern fens: methane flux and climatic change. Tellus 44B, 100-105 
  111. Smart, D.R., K. Ritchie, J.M. Stark, and B. Bugbee. 1997. Evidence that elevated CO2 levels can indirectly increase rhizosphere denitri.er activity. Appl. Environ. Microbiol. 63, 4621-4624 
  112. Guthrie, P.D. 1986. Biological methanogenesis and the CO2 greenhouse effect. J. Geophy. Res. 91, 10847-10851 
  113. Kang, H., S-Y. Kim, N. Fenner, and C. Freeman. 2004. Shift of soil enzyme activities in wetlands exposed to elevated CO2. Sci. Total Environ. (in press) 
  114. Körner, C. 2000. Biosphere responses to CO2 enrichment. Ecol. Appl. 10, 1590-1619 
  115. Niklaus, P.A. 1998. Effects of elevated atmospheric CO2 on soil microbiota in calcareous grassland. Global Change Biol. 4, 451-458 
  116. Schortemeyer, M., U.A. Hartwig, G.R. Hendrey, and M.J. Sadowsky. 1996. Microbial community changes in the rhizospheres of white clover and perennial ryegrass exposed to free air carbon dioxide enrichment (FACE). Soil Biol. Biochem. 28, 1717-1724 
  117. Ineson, P., P.A. Coward, and U.A. Hartwig. 1998. Soil gas fluxes of N2O, CH4 and CO2 beneath Lolium perenne under elevated CO2: The Swiss free air carbon dioxide enrichment experiment. Plant Soil 198, 89-95 
  118. Johnson, D.W., B.A. Hungate, P. Dijkstra, G. Hymus, and B.G. Drake. 2001. Effects of elevated carbon dioxide on soils in a Florida scrub oak ecosystem. J. Environ. Qual. 30, 501-507 
  119. King, J.S., R.B. Thomas, and B.R. Strain. 1997. Morphology and tissue quality of seedling root systems of Pinus taeda and Pinus ponderosa as affected by varying CO2, temperature, and nitrogen. Plant Soil 195, 107-119 
  120. O'Neill, E. 1994. Responses of soil biota to elevated atmospheric carbon dioxide. Plant Soil 165, 55-65 
  121. Saarnio, S., J. Alm, P.J. Martikainen, and J. Silvola. 1998. Effects of raised CO2 on potential CH4 production and oxidation in, and CH4 emission from, a boreal mire. Ecology 86, 261-268