Updated respiration routines alter spatio-temporal patterns of carbon cycling in a global land surface model

We updated the routines used to estimate leaf maintenance respiration in the Energy Land Model (ELM) using a comprehensive global respiration data base. The updated algorithm includes a temperature acclimating base rate, an updated instantaneous temperature response, and new plant functional type (PFT) specific parameters. The updated maintenance respiration algorithm resulted in a very large increase in global maintenance respiration (MR) of 16.1 Pg (38%), but the signal was not geographically uniform. The increase was concentrated in the tropics and humid warm-temperate forests. The increase in maintenance respiration led to large but proportionally smaller decreases in global net primary production (NPP, 19%) and in average global leaf area index (LAI, 15%). The effect on global gross primary production (GPP) was a more modest 5.7 Pg (4%). A detailed site level analysis also demonstrated a wide range of effects the updated algorithm can have on the seasonal cycle of GPP. Output from the updated and old models did not differ markedly in how closely they matched a suite of benchmarks. Given the substantial impact on the land surface carbon cycle, a neutral influence on model benchmarks, and better alignment with empirical evidence, a maintenance respiration algorithm similar to the one presented here should be adopted into ELM.