Background/Question/Methods: Ectomycorrhizal (ECM) fungi contribute significantly to ecosystem respiration, but little research has addressed the effect of temperature on ECM fungal respiration. Some plants have the ability to acclimate to temperature such that long-term exposure to warmer conditions slows respiration at a given measurement temperature and long-term exposure to cooler conditions increases respiration at a given measurement temperature. We examined acclimation to temperature of respiration by ECM fungi by incubating them for a week at one of three temperatures and measuring respiration over a range of temperatures.

Results/Conclusions: Among the 12 ECM fungal isolates that were tested, Suillus intermedius, Cenococcum geophilum, and Lactarius cf. pubescens exhibited significant acclimation to
temperature, exhibiting an average reduction in respiration of 20-45% when incubated at 23^oC compared to when incubated at 11^oC or 17^oC. We conclude that substantial variation exists among ECM fungal isolates in their ability to acclimate to temperature and so the structure of ectomycorrhizal fungal communities will determine the ability of the community as a whole to acclimate. As soil temperatures increase, ECM fungi that acclimate may require less carbon from their host plants than fungi that do not acclimate. The ability of some ECM fungi to acclimate may partially ameliorate the anticipated positive feedback between soil respiration and temperature.