Elevated moisture stimulates carbon loss from mineral soils by releasing protected organic matter.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 29176688.
- Also identified by DOI 10.1038/s41467-017-01998-z and PMC identifier 5701196.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Moisture response functions for soil microbial carbon (C) mineralization remain a critical uncertainty for predicting ecosystem-climate feedbacks. Theory and models posit that C mineralization declines under elevated moisture and associated anaerobic conditions, leading to soil C accumulation. Yet, iron (Fe) reduction potentially releases protected C, providing an under-appreciated mechanism for C destabilization under elevated moisture. Here we incubate Mollisols from ecosystems under C<sub>3</sub>/C<sub>4</sub> plant rotations at moisture levels at and above field capacity over 5 months. Increased moisture and anaerobiosis initially suppress soil C mineralization, consistent with theory. However, after 25 days, elevated moisture stimulates cumulative gaseous C-loss as CO<sub>2</sub> and CH<sub>4</sub> to >150% of the control. Stable C isotopes show that mineralization of older C<sub>3</sub>-derived C released following Fe reduction dominates C losses. Counter to theory, elevated moisture may significantly accelerate C losses from mineral soils over weeks to months-a critical mechanistic deficiency of current Earth system models.