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

Authors: 
Villarino SH, P Pinto, RB Jackson, G PiƱeiro
Year: 
2021
Journal: 
Science Advances
Journal Volume/Pages: 
7:eabd3176

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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