Plant rhizodeposition: a key factor for soil organic matter formation in stable fractions

Authors: Villarino SH, P Pinto, RB Jackson, G Piñeiro

Soil organic carbon formation remains poorly understood despite its importance for human livelihoods. Uncertainties

remain for the relative contributions of aboveground, root, and rhizodeposition inputs to particulate

(POC) and mineral-associated (MAOC) organic carbon fractions. Combining a novel framework with isotope tracer

studies, we quantified POC and MAOC formation efficiencies (% of C-inputs incorporated into each fraction). We

found that rhizodeposition inputs have the highest MAOC formation efficiency (46%) as compared to roots (9%)

or aboveground inputs (7%). In addition, rhizodeposition unexpectedly reduced POC formation, likely because it

increased decomposition rates of new POC. Conversely, root biomass inputs have the highest POC formation efficiency

(19%). Therefore, rhizodeposition and roots appear to play opposite but complementary roles for building

MAOC and POC fractions.