Global Change Biol. http://doi.org/cc33 (2017)
The temperature sensitivity of anaerobic decomposition of organic carbon in subtropical and tropical wetlands — a major natural source of global methane emissions — remains poorly represented in climate models. This is in part because experimental studies report variable carbon use efficiency (CUE) responses of the microbiota in response to warming, with reduced CUE equating to greater C losses to the atmosphere.
Debjani Sihi at the Wetland Biogeochemistry Laboratory, University of Florida, USA, and co-workers investigate the influence of the rate of temperature change on the relationship between temperature, CUE and soil organic carbon loss. They use two laboratory incubations, one with a large single-step temperature increase (10 °C within a day) and one with a similar magnitude, but a gradual temperature increase (0.1 °C per day for 100 days).
Warming rates are shown to affect thermal acclimation of microbial physiology with higher microbial CUE in treatments with slow warming rates. This resulted in relatively more microbial biomass carbon and enhanced soil C loss compared with rapid warming. The rapid warming treatment led to an overall greater radiative forcing, however, due to enhanced methane production. These findings tentatively imply that radiative forcing associated with anaerobic carbon processing could be lower