Thermal acclimation of plant photosynthesis and autotrophic respiration in a northern peatland

Abstract Peatlands contain one-third of global soil carbon (C), but the responses of peatland ecosystems to long-term warming are not well understood. Here, we pursue an emergent understanding of warming effects on ecosystem C fluxes at peatlands by constraining a process-oriented model, the Terrestrial ECOsystem (TECO) model, with observation data from a long-term warming experiment at the Spruce and Peatland Responses Under Changing Environments (SPRUCE) site. Model-based assessments show that ecosystem-level photosynthesis and autotrophic respiration exhibited significant thermal acclimation, with temperature sensitivities being linearly decreased with warming. Using the thermal acclimated parameter values, simulated gross primary production (GPP), net primary production (NPP), and plant autotrophic respiration (Ra), were all lower than those simulated with non-thermal acclimated parameter values. In contrast, ecosystem respiration (ER) simulated with thermal acclimated parameter values was higher than that simulated with non-thermal acclimated parameter values. Net ecosystem CO2 exchange (NEE) was much higher after constraining model parameters with observational data from the warming treatments, releasing C at a rate of 28.3 g C m-2 yr-1 °C-1. Our data-model integration study suggests that peatlands are likely to release more C than previously estimated. Earth system models may overestimate C uptake by peatlands under warming if physiological thermal acclimation of plants is not incorporated. Thus, it is critical to consider the long-term physiological thermal acclimation of plants in the models to better predict global C dynamics under future climate and their feedback to climate change.