title: Abrupt rise in atmospheric CO2 overestimates community response in a model plant-soil system.
abstract: Attempts to understand the ecological effect of increasing atmospheric CO2 concentration, [CO2], usually involve exposing today's ecosystems to expected future [CO2] levels. However, a major assumption of these approaches has not been tested--that exposing ecosystems to a single-step increase in [CO2] will yield similar responses to those of a gradual increase over several decades. We tested this assumption on a mycorrhizal fungal community over a period of six years. [CO2] was either increased abruptly, as is typical of most [CO2] experiments, or more gradually over 21 generations. The two approaches resulted in different structural and functional community responses to increased [CO2]. Some fungi were sensitive to the carbon pulse of the abrupt [CO2] treatment. This resulted in an immediate decline in fungal species richness and a significant change in mycorrhizal functioning. The magnitude of changes in fungal diversity and functioning in response to gradually increasing [CO2] was smaller, and not significantly different to those with ambient [CO2]. Our results suggest that studies may overestimate some community responses to increasing [CO2] because biota may be sensitive to ecosystem changes that occur as a result of abrupt increases.
authors.affiliation: Department of Integrative Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada. jklirono@uoguelph.ca
authors.forename: John N
authors.initials: JN
authors.lastname: Klironomos
authors.forename: Michael F
authors.initials: MF
authors.lastname: Allen
authors.forename: Matthias C
authors.initials: MC
authors.lastname: Rillig
authors.forename: Jeff
authors.initials: J
authors.lastname: Piotrowski
authors.forename: Shokouh
authors.initials: S
authors.lastname: Makvandi-Nejad
authors.forename: Benjamin E
authors.initials: BE
authors.lastname: Wolfe
authors.forename: Jeff R
authors.initials: JR
authors.lastname: Powell
mesh_terms: D000704:Analysis of Variance; D001272:Atmosphere / Q000737:chemistry*; D018533:Biomass; D031724:Bromus / Q000378:metabolism* / Q000382:microbiology*; D002245:Carbon Dioxide / Q000032:analysis / Q000378:metabolism*; D017753:Ecosystem; D005658:Fungi / Q000378:metabolism; D009864:Ontario; D012987:Soil / Q000032:analysis*
chemical_list: D012987:Soil; D002245:Carbon Dioxide