Warming-related increases in soil CO₂ efflux are explained by increased below-ground carbon flux

Abstract

The universally observed exponential increase in soil-surface CO₂ effux (‘soil respiration’; FS) with increasing temperature has led to speculation that global warming will accelerate soil organic carbon (SOC) decomposition, reduce SOC storage, and drive a positive feedback to future warming. However, interpreting temperature–FS relationships, and so modelling terrestrial carbon balance in a warmer world, is complicated by the many sources of respired carbon that contribute to FS and a poor understanding of how temperature influences SOC decomposition rates. Here we quantified FS, litterfall, bulk SOC and SOC fraction size and turnover, and total below-ground carbon flux (TBCF) across a highly constrained 5.2 degree C mean annual temperature (MAT) gradient in tropical montane wet forest. From these, we determined that: increases in TBCF and litterfall explain >90% of the increase in FS with MAT; bulk SOC and SOC fraction size and turnover rate do not vary with MAT; and increases in TBCF and litterfall do not influence SOC storage or turnover on century to millennial timescales. This gradient study shows that for tropical montane wet forest, long-term and whole-ecosystem warming accelerates below-ground carbon processes with no apparent impact on SOC storage.

Keywords

soil organic carbon, tropical forests, ecosystem carbon fluxes, climate change, warming

Citation

Giardina, Christian P.; Litton, Creighton M.; Crow, Susan E.; Asner Gregory P. 2014. Warming-related increases in soil CO2 efflux are explained by increased below-ground carbon flux. Nature Climate Change 4, 822 827