Estimating autotrophic respiration in streams using daily metabolism data

Abstract

AbstractThe fraction of gross primary production (GPP) that is immediately respired by autotrophs and their closely associated heterotrophs (ARf) is unknown. This value is necessary to calculate the autotrophic base of food webs, which requires knowing production available for grazers. ARf is also necessary for estimating heterotrophic respiration (HR) which is needed to calculate C spiraling in streams and rivers. We suggest a way to estimate ARf from daily metabolism data using quantile regression between GPP and 90% quantile of ecosystem respiration (ER). We reasoned that autotrophic respiration represents the lower limit for ER on any one day and used quantile regression to estimate the relationship of the lower quantile of ER with respect to GPP. We examined this approach with simulation modeling and application of quantile regression to estimates of continuous GPP and ER from >20 streams. Simulation modeling showed that low-uncertainty estimates of ARf required large variation in daily GPP. Covarian...