The carbon-quality temperature hypothesis: Fact or artefact?

Area of Science:

• Environmental Science
• Soil Science
• Biogeochemistry

Background:

• Climate warming enhances microbial decomposition, potentially reducing global soil carbon stocks.
• The temperature sensitivity of resistant soil carbon decomposition is uncertain, impacting climate change impact assessments.
• The carbon-quality temperature (CQT) hypothesis suggests recalcitrant carbon is more temperature-sensitive, implying amplified CO2 release under warming.

Purpose of the Study:

• To investigate the temperature sensitivity of soil carbon decomposition based on carbon quality.
• To test the validity of the carbon-quality temperature (CQT) hypothesis.
• To determine if climate warming could disproportionately accelerate the decomposition of recalcitrant soil carbon.

Main Methods:

• Redefined carbon quality using uncatalysed reaction rates to avoid reference temperature artefacts.
• Assessed the relationship between carbon quality and temperature sensitivity in enzyme-catalysed reactions.
• Analyzed decomposition rates of various soil carbon compounds under different temperature conditions.

Main Results:

• Previous evidence supporting the CQT hypothesis was found to be an artefact of reference temperature selection.
• No significant relationship was observed between carbon quality (uncatalysed rate) and temperature sensitivity in enzyme-catalysed reactions.
• Soil carbon decomposition exhibits similar temperature sensitivity irrespective of carbon quality.

Conclusions:

• The CQT hypothesis is not supported by enzyme-catalysed decomposition rates.
• Concerns regarding accelerated decomposition of recalcitrant soil carbon due to climate warming are likely unfounded.
• Soil carbon loss due to warming may be less sensitive to carbon chemical composition than previously assumed.