DOI: 10.5061/dryad.m0cfxpp9w
title: Organo-organic interactions dominantly drive soil organic carbon accrual

description: Organo-mineral interactions have been regarded as the primary mechanism
 for the stabilization of soil organic carbon (SOC) over decadal to
 millennial timescales, and the capacity for soil carbon (C) storage has
 commonly been assessed based on soil mineralogical attributes,
 particularly mineral surface availability. However, it remains contentious
 whether soil C sequestration is exclusively governed by mineral vacancies,
 making it challenging to accurately predict SOC dynamics. Here, through a
 400-day incubation experiment using 13C-labeled organic materials in two
 contrasting soils (i.e., Mollisol and Ultisol), we show that despite the
 unsaturation of mineral surfaces in both soils, the newly incorporated C
 predominantly adheres to "dirty" mineral surfaces coated with
 native organic matter (OM), demonstrating the crucial role of
 organo-organic interactions in exogenous C sequestration. Such
 interactions lead to multilayered C accumulation that is not constrained
 by mineral vacancies, a process distinct from direct organo-mineral
 contacts. The coverage of native OM by new C, representing the degree of
 organo-organic interactions, is noticeably larger in Ultisol (~14.2%) than
 in Mollisol (~5.8%), amounting to the net retention of exogenous C in
 Ultisol by 0.2–1.3 g kg−1 and in Mollisol by 0.1–1.0 g kg−1. Additionally,
 organo-organic interactions are primarily mediated by polysaccharide-rich
 microbial necromass. Further evidence indicates that iron oxides can
 selectively preserve polysaccharide compounds, thereby promoting the
 organo-organic interactions. Overall, our findings provide direct
 empirical evidence for an overlooked but critically important pathway of C
 accumulation, challenging the prevailing “C saturation” concept that
 emphasizes the overriding role of mineral vacancies. It is estimated that,
 through organo-organic interactions, global Mollisols and Ultisols might
 sequester ~0.1–1.0 Pg C and ~0.3–1.7 Pg C per year, respectively,
 corresponding to the neutralization of ca. 0.5%–3.0% of soil C emissions
 or 5%–30% of fossil fuel combustion globally.
description: # Organo-organic interactions dominantly drive soil organic carbon accrual
 This README file was
 generated on 2024-01-12 by Jie Kang. This dataset supports the findings
 reported in Kang, J., Qu, C., Chen, W., Cai, P.,Chen, C., & Huang, Q.
 (2024). Organo–organic interactions dominantly drive soil organic carbon
 accrual. Global Change Biology, 30, e17147.
 . ## Data descriptions by sheet:
 #### Sheet1 - General description #### MAOC - Mineral-associated organic
 carbon 1. Unit: g kg-1. 2. *MAOC source* -- MAOC fraction derived from
 exogenous carbon (new) or endogenous carbon (native). While the total MAOC
 is the sum of new MAOC and native-MAOC. 3. *Soil type* -- Mollisol and
 Ultisol used in the study. 4. *Treatment* -- Whether the soil sample is
 unamended (control) or amended with straw or glucose. 5. *Mean & SD*
 -- Mean values and standard deviation (n = 3). #### MNC - Microbial
 necromass carbon 1. Unit: g kg-1. 2. *MNC source* -- MNC fraction derived
 from fungal necromass or bacterial necromass. While the total MNC is the
 sum of fungal MNC and bacterial MNC. #### SR-FTIR - Synchrotron
 radiation-based Fourier transform infrared microspectroscopy 1. Values are
 summed peak intensities at the corresponding peak positions for each
 functional group. 2. Multiple data points were collected within the
 measured area for each sample. 3. *Clay* -- Phyllosilicates, clay–OH
 stretching at 3620 cm−1. 4. *Fe-O* -- Fe oxides, Fe–O stretching at 690
 cm−1. 5. *Al-O* -- Al oxides, Al–O stretching at 915 cm−1. 6. *Phen* --
 Phenolics, OH stretching at 3379 cm−1. 7. *Alip* -- Aliphatics, a
 combination of CH3 and CH2 stretching at 2920 and 2856 cm−1 and CH
 deformation at 1419 cm−1 8. *Carb* -- Carboxylics, a combination of C=O
 stretching at 1716 cm−1 and C–O stretching and OH deformation at 1252 cm−1
 9. *Arom* -- Aromatics, C=C vibration at 1618 cm−1. 10. *Poly* --
 Polysaccharides, C–O stretching at 1036 cm−1. #### NanoSIMS - Nano-scale
 secondary ion mass spectrometry imaging 1. Unit: %. 2. Only samples with
 exogenous carbon amendment were measured. 3. Nine spots were analyzed for
 each sample. 4. *native_mineral* -- The coverages of soil minerals
 occupied by native OM. 5. *new_native* -- The coverages of native OM
 occupied by new OC. #### Ascomycota - A fungal phylum known as primary
 decomposers of plant straw 1. Unit: %. 2. *Proportion* -- The relative
 abundance of Ascomycota. #### Artificial Soil 1. *Treatments* -- Two
 artificial soils with different Fe mineral proportions were prepared. The
 low-Fe artificial soil was composed of 60% sand, 17.5% kaolinite, 17.5%
 montmorillonite, and *5% goethite* (w:w), while the high-Fe artificial
 soil contained 60% sand, 15% kaolinite, 15% montmorillonite, and *10%
 goethite* (w:w). 2. *Poly* -- The proportion of polysaccharide compounds.
 3. *TOC* -- Total organic carbon. 4. *MNC_f* and *MNC_b* -- Fungal- and
 bacterial-derived microbial necromass carbon, respectively. 5. *MNC_t* --
 Total MNC, which is the sum of MNC_f and MNC_b. 6. *_SD* -- Standard
 deviation (n = 3). #### CO2+PE - CO2 analysis and priming effect (PE)
 calculation 1. Unit for CO2 emissions: mg C kg-1 soil day-1. 2. Unit for
 PE: %. 3. *Day* -- Gas sampling date. 4. *Flux* and *Cumulative* -- Fluxes
 and cumulative emissions of CO2. 5. *PE_inst* and *PE_cumu* --
 Instantaneous and cumulative PE. 6. *_SD* -- Standard deviation (n = 3).