Research ArticleENVIRONMENTAL STUDIES

Temperature sensitivity of SOM decomposition governed by aggregate protection and microbial communities

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Science Advances  10 Jul 2019:
Vol. 5, no. 7, eaau1218
DOI: 10.1126/sciadv.aau1218
  • Fig. 1 Q10 values for various SOM components in the topsoil and subsoil.

    (A) Q10 for bulk soil, active pool, and slow pool. (B) Q10 for three cumulative respired soil C fractions. The ends of the boxes represent the 25th and 75th percentiles. The horizontal lines inside each box and the whiskers show the median and the SD, respectively (n = 9). *P < 0.05, significant difference between the topsoil and the subsoil; ns, no significant difference.

  • Fig. 2 Comparison of SOM composition and mineral protection between the topsoil and the subsoil.

    (A) 13C CPMAS NMR spectra. Chemical shifts of 0 to 50, 50 to 110, 110 to 165, and 165 to 220 parts per million (ppm) represent alkyl C, O-alkyl C, aromatic C, and carboxylic C, respectively. (B) Percentage of alkyl C and O-alkyl C relative to total SOC and ratio of the two SOM compositions. (C) Percentage of Fe-bound SOC and silt + clay–bound SOC relative to total SOC. Error bars denote SE (n = 9). *P < 0.01, significant difference between the topsoil and the subsoil. ns, no significant difference.

  • Fig. 3 Relationships between Q10 and C distribution in aggregates.

    (A and B) Bulk soil Q10 with macro and micro. (C and D) Active pool Q10 with macro and micro. (E and F) Slow pool Q10 with macro and micro. Macro refers to the percentage of soil C stored in macroaggregates (250 to 2000 μm), and micro denotes the percentage in microaggregates (53 to 250 μm). Red circles represent samples in the topsoil (n = 9), and blue circles represent samples in the subsoil (n = 9). r2 is the proportion of variance explained. The insets show the depth-associated variations of C distribution in macroaggregates and microaggregates, respectively. Error bars denote SE (n = 9). *P < 0.01, significant difference between the two soil depths.

  • Fig. 4 Relationships between Q10 and fungal PLFAs.

    (A) Bulk soil Q10. (B) Active pool Q10. (C) Slow pool Q10. Fungal PLFAs refer to the relative abundance of fungi (fungal PLFAs/total PLFAs). Red circles represent samples in the topsoil (n = 9), and blue circles represent samples in the subsoil (n = 9). r2 is the proportion of variance explained. The inset shows the comparison of relative abundance of fungal PLFAs between the topsoil and the subsoil. *P < 0.01. Error bars are SE (n = 9).

  • Fig. 5 Variation partitioning analyses for Q10 in various SOM components.

    (A) Bulk soil Q10. (B) Active pool Q10. (C) Slow pool Q10. The variation is partitioned to the following fractions: pure effect of aggregate protection (X1), pure effect of microbial communities (X2), joint effects of aggregate protection and microbial communities (X3), and unexplained variations. Aggregate protection includes the percentage of soil C stored in macroaggregates (250 to 2000 μm) and microaggregates (53 to 250 μm). Microbial communities refer to the relative abundance of fungal PLFAs.

  • Fig. 6 Q10 in active and slow pools derived from two manipulative experiments.

    (A) Microorganism reciprocal transplant. (B) Aggregate disruption. △Q10 is the Q10 difference between the topsoil and the subsoil, with a positive value representing larger Q10 in the topsoil and a negative value representing larger Q10 in the subsoil. Error bars denote SE (n = 9). *P < 0.01, significant difference between control and treatment. ns, no significant difference.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/7/eaau1218/DC1

    Fig. S1. Field soil sampling and laboratory incubation.

    Fig. S2. Effects of microorganism reciprocal transplant on Q10 for the two soil depths.

    Fig. S3. Changes in the cumulative respired soil C with incubation time.

    Fig. S4. Comparison between modeled and measured soil C flux.

    Table S1. Analysis of variance table for Q10 values from different sites and soil depths.

    Table S2. Comparison of topsoil and subsoil microbial communities at three sites.

    Table S3. Physicochemical characteristics in the two soil depths at three sites.

    Table S4. Prior parameter ranges for C pool partitioning coefficients (fi), decay rates (ki), and temperature sensitivity (Q10i).

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Field soil sampling and laboratory incubation.
    • Fig. S2. Effects of microorganism reciprocal transplant on Q10 for the two soil depths.
    • Fig. S3. Changes in the cumulative respired soil C with incubation time.
    • Fig. S4. Comparison between modeled and measured soil C flux.
    • Table S1. Analysis of variance table for Q10 values from different sites and soil depths.
    • Table S2. Comparison of topsoil and subsoil microbial communities at three sites.
    • Table S3. Physicochemical characteristics in the two soil depths at three sites.
    • Table S4. Prior parameter ranges for C pool partitioning coefficients (fi), decay rates (ki), and temperature sensitivity (Qi10).

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