Ongoing climatic changes are affecting the species composition and functioning of terrestrial ecosystems, with potential consequences for ecosystem services and the rate of climate change itself. To characterize the sensitivity of an old-field ecosystem to future climate scenarios, the Boston-Area Climate Experiment subjected 4m2 plots to each of twelve climate treatments: four levels of warming (spanning 0 to 4 degrees C of warming relative to the ambient canopy temperature) under three precipitation treatments (50% reduction, ambient rainfall, or a 50% growing season supplementation). Here, we report on the climate change sensitivity of ecosystem-level carbon and nitrogen fluxes and transformations, and community composition shifts during the first five years of the experiment.
Results/Conclusions
Treatment effects were rarely additive, as small effects of precipitation under ambient temperature were dramatically amplified in the warmed treatments. Precipitation removal suppressed both production of woody and herbaceous species and soil respiration, but primarily under warmed conditions. Precipitation addition promoted growth and to a lesser extent soil respiration, but only under warmed conditions. The precipitation reduction affected herbaceous community composition, but this effect was much more dramatic under warmed than ambient conditions. The response of nitrogen transformations to precipitation was similarly affected by the warming treatment. Understanding the dependence of temperature responses on precipitation (and vice versa) can improve our ability to forecast shifts in ecosystem services and climate feedbacks on our changing planet.