Biochar induces mineralization of soil recalcitrant components by activation of biochar responsive bacteria groups

Amendment of soil with biochar induces a shift in microbial community structure and promotes faster mineralization of soil organic carbon (SOC), thus offsetting C sequestration effects. Whether biochar induces losses of
labile or persistent SOC pools remains largely unknown, and the responsible decomposers await identification.
Towards addressing these ends, a C3 soil was amended with Biochar500 or Biochar600 (pyrolyzed at 500 ◦C and
600 ◦C, respectively) produced from a C4-maize feedstock and incubated for 28 days. Combination of stable
isotope 13C techniques, high-throughput sequencing and Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) allowed changes in soil chemodiversity and biodiversity, as well as their interactive effects
on biochar induced SOC mineralization to be elucidated. Results indicated that: i) biochar addition shifted the
bacterial community towards dominance of Gemmatimonadetes, Bacteroidia, Alphaproteobacteria and Gammaproteobacteria classes, and coincidence with recalcitrant C components and neutral pH soil; ii) the persistent
DOM components (such as condensed aromatics and tannin) were depleted in biochar amended soils, while labile
DOM components (such as unsaturated hydrocarbons, lipids, carbohydrates and proteins/amino sugar) were
relatively enriched, and; iii) Biochar600 promoted additional soil derived CO2 carbon loss over 28 days (93 mg C
kg− 1 soil). Collectively, these results suggested that the majority of soil derived CO2 efflux in biochar amended
soils originated from recalcitrant components that were mineralized by the persistent organic matter decomposers. This research highlights the significance of biochar responsive taxa in changes of DOM chemodiversity and potential loss of SOC via mineralization.