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

Villarino SH, P Pinto, RB Jackson, G PiƱeiro
Science Advances
Journal Volume/Pages: 

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.

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