title: Microcosm tests of the effects of temperature and microbial species number on the decomposition of Carex aquatilis and Sphagnum fuscum litter from southern boreal peatlands.
abstract: Increased decomposition rates in boreal peatlands with global warming might increase the release of atmospheric greenhouse gases, thereby producing a positive feedback to global warming. How temperature influences microbial decomposers is unclear. We measured in vitro rates of decomposition of senesced sedge leaves and rhizomes (Carex aquatilis), from a fen, and peat moss (Sphagnum fuscum), from a bog, at 14 and 20 degrees C by the three most frequently isolated fungi and bacteria from these materials. Decomposition rates of the bog litter decreased (5- to 17-fold) with elevated temperatures, and decomposition of the sedge litters was either enhanced (2- to 30-fold) or remained unaffected by elevated temperatures. The increased temperature regime always favoured fungal over bacterial decomposition rates (2- to 3-fold). Different physiological characteristics of these microbes suggest that fungi using polyphenolic polymers as a carbon source cause greater mass losses of these litters. Litter quality exerted a stronger influence on decomposition at elevated temperatures, as litter rich in nutrients decomposed more quickly than litter poorer in nutrients at higher temperatures (8.0%-25.7% for the sedge litters vs. 0.2% for the bryophyte litter). We conclude that not all peatlands may provide a positive feedback to global warming. Cautious extrapolation of our data to the ecosystem level suggests that decomposition rates in fens may increase and those in bogs may decrease under a global warming scenario.
authors.affiliation: Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada. mthorman@nrcan.gc.ca
authors.forename: Markus N
authors.initials: MN
authors.lastname: Thormann
authors.forename: Suzanne E
authors.initials: SE
authors.lastname: Bayley
authors.forename: Randolph S
authors.initials: RS
authors.lastname: Currah
mesh_terms: D001419:Bacteria / Q000378:metabolism; D001673:Biodegradation, Environmental; D018533:Biomass; D017753:Ecosystem; D004783:Environmental Microbiology; D005460:Fluorides, Topical / Q000378:metabolism*; D005658:Fungi / Q000378:metabolism; D017752:Greenhouse Effect; D018515:Plant Leaves / Q000378:metabolism / Q000382:microbiology; D044003:Sphagnopsida / Q000378:metabolism* / Q000382:microbiology*; D013696:Temperature
chemical_list: C070175:Carex; D005460:Fluorides, Topical