Foliar respiration acclimation to temperature and temperature variable Q10 alter ecosystem carbon balance

The response of respiration to temperature in plants can be considered at both short- and long-term temporal scales. Short-term temperature responses are not well described by a constant Q(10) of respiration, and longer-term responses often include acclimation. Despite this, many carbon balance models use a static Q(10) of respiration to describe the short-term temperature response and ignore temperature acclimation. We replaced static respiration parameters in the ecosystem model photosynthesis and evapo-transpiration (PnET) with a temperature-driven basal respiration algorithm (Rd(acclim)) that accounts for temperature acclimation, and a temperature-variable Q(10) algorithm (Q(10var)). We ran PnET with the new algorithms individually and in combination for 5 years across a range of sites and vegetation types in order to examine the new algorithms' effects on modeled rates of mass- and area-based foliar dark respiration, above ground net primary production (ANPP), and foliar respiration-photosynthesis ratios. The Rd(acclim) algorithm adjusted dark respiration downwards at temperatures above 18 degrees C, and adjusted rates up at temperatures below 5 degrees C. The Q(10var) algorithm adjusted dark respiration down at temperatures below 15 degrees C. Using both algorithms simultaneously resulted in decreases in predicted annual foliar respiration that ranged from 31% at a tall-grass prairie site to 41% at a boreal coniferous site. The use of the Rd(acclim) and Q(10var) algorithms resulted in increases in predicted ANPP ranging from 18% at the tall-grass prairie site to 38% at a warm temperate hardwood forest site. The new foliar respiration algorithms resulted in substantial and variable effects on PnETs predicted estimates of C exchange and production in plants and ecosystems. Current models that use static parameters may over-predict respiration and subsequently under-predict and/or inappropriately allocate productivity estimates. Incorporating acclimation of basal respiration and temperature-sensitive Q(10) have the potential to enhance the application of ecosystem models across broad spatial scales, or in climate change scenarios, where large temperature ranges may cause static respiration parameters to yield misleading results.