Increases in Atmospheric [CO2] and the Soil Food Web
Bacterial and fungal communities in soil ecosystems use such plant materials as resources to support multiple levels of tiny grazers and predators, which comprise soil food webs.
Ten years of elevated [CO2] at the ETH FACE site produced data on soil protozoa and nematodes that are consistent with adjustments predicted for availability of soil bacteria and fungi.
Disparate changes in soil microorganisms and complex adjustments in food web structure reported under higher [CO2] in a multitude of other experiments suggest that a better understanding of C resource availability is needed.
Increases in living root mass under elevated [CO2] could affect soil food webs through additional exudation, but limited information is available on changes in root exudation under such conditions. We summarize here a new, more complex, understanding of root exudation that includes mechanisms by which microorganisms, and possibly their predators within the food web, can actively enhance root exudation. Initial experiments indicate that higher [CO2] can increase root exudation of amino acids under axenic conditions by two separate mechanisms and these could result in more rhizodeposition.
Little is known about how elevated [CO2] levels alter predation, another key connection between the soil food web and the plant, but reductionist studies are beginning to support the concept that specific molecules affect predation and influence many organismic interactions in the root zone.
Because the fossil record suggests soil food webs were exposed to widely varied levels of [CO2] for long periods, a certain stability of these interactions should be expected as global atmospheric [CO2] increases.
KeywordsFine Root Root Exudation Root Colonization Global Change Biol Biol Fertil Soil
Unable to display preview. Download preview PDF.
- Bargmann CI, Mori I (1997) Chemotaxis and thermotaxis. In: Riddle DL, Blumenthal T, Meyer BJ, Preiss JR (eds) C. elegans II. Cold Spring Harbor Laboratory Press, Cold Spring Harbor, pp 717–737Google Scholar
- Brussaard L, Behan-Pelletier VM, Bignell DE, Brown VK, Didden W, Folgarait P, Fragoso C, Freckman DW, Gupta V, Hattori T, Hawksworth DL, Klopatek C, Lavelle P, Malloch DW, Rusek J, Soderstrom B, Tiedje JM, Virginia RA (1997) Biodiversity and ecosystem functioning in soil. Ambio 26:563–570Google Scholar
- De Leij F, Dixon-Hardy JE, Lynch JM (2002) Effect of 2,4-diacetylphloroglucinol-producing and non-producing strains of Pseudomonas fluorescens on root development of pea seedlings in three different soil types and its effect on nodulation by Rhizobium. Biol Fertil Soils 35:114–121CrossRefGoogle Scholar
- Farrar J, Hawes M, Jones D, Lindow S (2003) How roots control the flux of carbon to the rhizosphere. Ecology 84:827–837Google Scholar
- Ferris H (1982) The role of nematodes as primary consumers. In: Freckman DW (ed) Nematodes in soil ecosystems. University of Texas, Austin, pp 3–13Google Scholar
- Inubushi K, Cheng WG, Chander K (1999) Carbon dynamics in submerged soil microcosms as influenced by elevated CO2 and temperature. Soil Sci Plant Nutr 45:863–872Google Scholar
- Jones DL, Darrah PR (1994) Amino-acid influx at the soil-root interface of Zea Mays L. and its implications in the rhizosphere. Plant Soil 163:1–12Google Scholar
- Jones TH, Thompson LJ, Lawton JH, Bezemer TM, Bardgett RD, Blackburn TM, Bruce KD, Cannon PF, Hall GS, Hartley SE, Howson G, Jones CG, Kampichler C, Kandeler E, Ritchie DA (1998) Impacts of rising atmospheric carbon dioxide on model terrestrial ecosystems. Science 280:441–443PubMedCrossRefGoogle Scholar
- Klingler J (1965) On the orientation of plant nematodes and of some other soil animals. Nematologica 11:14–18Google Scholar
- Laakso J, Setälä H (1999) Sensitivity of primary production to changes in the architecture of belowground food webs. Oikos 87:57–64Google Scholar
- Lal R (2003) Global potential of soil carbon sequestration to mitigate the greenhouse effect. Crit Rev Plant Sci 22:151–184Google Scholar
- Langley JA, Dijkstra P, Drake BG, Hungate BA (2003) Ectomycorrhizal colonization, biomass, and production in a regenerating scrub oak forest in response to elevated CO2. Ecosystems 6:424–430Google Scholar
- Lee DL (2002) Behaviour. In: Lee DL (ed) The biology of nematodes. Taylor and Francis, London, pp 369–387Google Scholar
- Moens T, Verbeeck L, de Maeyer A, Swings J, Vincx M (1999) Selective attraction of marine bacterivorous nematodes to their bacterial food. Mar Ecol Progr Ser 176:165–178Google Scholar
- Moore JC, McCann K, Setälä H, Ruiter PC de (2003) Top-down is bottom-up: Does predation in the rhizosphere regulate aboveground dynamics? Ecology 84:846–857Google Scholar
- Owensby CE, Coyne PI, Ham JM, Auen LM, Knapp AK (1993) Biomass production in a tallgrass prairie ecosystem exposed to ambient and elevated CO2. Ecol Appl 3:644–653Google Scholar
- Perry RN, Aumann J (1998) Behaviour and sensory responses. In: Perry RN, Wright DJ (eds) The physiology and biochemistry of free-living and plant-parasitic nematodes. CAB International, Wallingford, pp 75–102Google Scholar
- Phillips DA, Ferris H, Cook DR, Strong DR (2003) Molecular control points in rhizosphere food webs. Ecology 84:816–826Google Scholar
- Poinar GO (1983) The natural history of nematodes. Prentice-Hall, Englewood Cliffs, N.J.Google Scholar
- Prot JC (1977) Amplitude et cinétique des migrations du nématode Meloidogyne javanica sous l’influence d’un plant de tomate. Cah ORSTOM Ser Biol 11:157–166Google Scholar
- Rovira AD (1991) Rhizosphere research — 85 years of progress and frustration. In: Keister DL, Cregan PB (eds) The rhizosphere and plant growth. Kluwer Academic, Dordrecht, pp 3–13Google Scholar
- Taraz K, Schaffner EM, Budzikiewicz H, Korth H, Pulverer G (1990) 2,3,9-Trihydoxyphenazin-1-carbonsäure — ein unter Berylliumeinwirkung gebildetes neues Phenazinderivat aus Pseudomonas fluorescens. Z Naturforsch 45b:552–556Google Scholar
- Viglierchio DR (1961) Attraction of parasitic nematodes by plant root emanations. Phytopathol 51:136–142Google Scholar
- Zak DR, Ringelberg DB, Pregitzer KS, Randlett DL, White DC, Curtis PS (1996) Soil microbial communities beneath Populus grandidentata crown under elevated atmospheric CO2. Ecol Appl 6:257–262Google Scholar