Do soils breath more under elevated CO₂?

Project leader, researchers and collaborators: 
Dr Catriona Macdonald, Dist Prof Brajesh Singh, Prof Ian Anderson (Director of Research), Prof Mark Tjoelker, Dist Prof Peter Reich 

Funding period: 

Project summary: Soils represent a huge carbon store, and hold almost 80% (2500 gigatons [GT]) of the 3170 GT of C stored globally in terrestrial ecosystems^[1].

Although often unseen, soil is teaming with life and is one of the most diverse habitats on earth.  Archaea, bacteria, protists, tardigrades, rotifers, nematodes, mites, springtails, worms, macroarthopods, burrowing animals, fungi, lichens and plant roots form a complex soil food web.  Plant derived carbon, primarily in the form of plant litter and root exudates, forms the base of this food web, fuelling energy transfer throughout the system.

Consequently, soils respire and are a source of atmospheric CO₂.

Under rising atmospheric CO₂ (eCO₂) concentrations, it is predicted that higher rates of plant photosynthesis will results in increased C-inputs to soil.  However, uncertainty remains as to whether eCO₂ leads to increased soil C storage, or facilitates more rapid turnover and increases the release of CO₂ back to the atmosphere.

This is particularly uncertain for nutrient limited ecosystems that may have restricted capacity to store additional fixed C in plant biomass.

Here at EucFACE we are using long-term autochambers to measure soil respiration (R_soil) every 30 minutes.  Alongside regular survey measurements, we aim to determine how R_soil responds to eCO₂ in this P-limited forest ecosystem^[2,3], and, by monitoring soil C, help to identify longer-term consequences for C-sequestration^[4].

[1] Lal, R. 2008.  Carbon sequestration. Philosophical Transactions of the Royal Society B 363, 815-830.

[2] Drake, JE, Macdonald, CA, Tjoelker, MG, et al.  2016.  Short-term carbon cycling responses of a mature eucalypt woodland to gradual stepwise enrichment of atmospheric CO2 concentration.  Global Change Biology.

[3] Drake, JE, Macdonald, CA, Tjoelker, MG, et al.  2018.  Three years of soil respiration in a mature eucalypt woodland exposed to atmospheric CO2 enrichment.  Biogeochemistry 139, 52-101 10.1007/s10533-018-0457-7

[4] Jiang M, Medlyn BE, Drake JE et al. 2020.  The fate of carbon in a mature forest under carbon dioxide enrichment. Nature 280, 227-231.