Reconciling the temperature dependence of respiration across timescales and ecosystem types

Ecosystem respiration is the biotic conversion of organic carbon to CO2 by all of the organisms in an ecosystem, including both consumers and primary producers. Respiration exhibits an exponential temperature dependence at the subcellular and individual levels1, but at the ecosystem level, this can be modified by many variables2,3, including community abundance and biomass4, which can vary substantially among ecosystems5. Despite its importance to predicting the responses of the biosphere to climate change, it is as yet unknown whether the temperature dependence of ecosystem respiration varies systematically between aquatic and terrestrial environments. Here we use the largest database of respiratory measurements yet compiled to show that the sensitivity of ecosystem respiration to seasonal changes in temperature is remarkably similar for aquatic and terrestrial systems from across the globe, with a similar average activation energy to that of the respiratory complex3 (~0.65 eV). By contrast, annual ecosystem respiration exhibits a substantially greater temperature-dependence across aquatic (~0.65 eV) versus terrestrial ecosystems (~0.32 eV). Using a model4 derived from metabolic theory6, these findings can be reconciled due to similarities in the biochemical kinetics of metabolism at the subcellular level, combined with differences in the importance of other variables besides temperature – such as allochthonous carbon inputs – on the structure of aquatic and terrestrial biota at the community level. Our findings suggest that the effects of warming on annual respiration may be far more pronounced in aquatic than in terrestrial ecosystemsJRC.H.7-Climate Risk Managemen

Reconciling the temperature dependence of respiration across timescales and ecosystem types

Ecosystem respiration is the biotic conversion of organic carbon to carbon dioxide by all of the organisms in an ecosystem, including both consumers and primary producers. Respiration exhibits an exponential temperature dependence at the subcellular and individual levels, but at the ecosystem level respiration can be modified by many variables including community abundance and biomass, which vary substantially among ecosystems. Despite its importance for predicting the responses of the biosphere to climate change, it is as yet unknown whether the temperature dependence of ecosystem respiration varies systematically between aquatic and terrestrial environments. Here we use the largest database of respiratory measurements yet compiled to show that the sensitivity of ecosystem respiration to seasonal changes in temperature is remarkably similar for diverse environments encompassing lakes, rivers, estuaries, the open ocean and forested and non-forested terrestrial ecosystems, with an average activation energy similar to that of the respiratory complex (approximately 0.65 electronvolts (eV)). By contrast, annual ecosystem respiration shows a substantially greater temperature dependence across aquatic (approximately 0.65 eV) versus terrestrial ecosystems (approximately 0.32 eV) that span broad geographic gradients in temperature. Using a model derived from metabolic theory, these findings can be reconciled by similarities in the biochemical kinetics of metabolism at the subcellular level, and fundamental differences in the importance of other variables besides temperature-such as primary productivity and allochthonous carbon inputs-on the structure of aquatic and terrestrial biota at the community level.5 page(s