Linking temperature sensitivity of soil organic matter decomposition to its molecular structure, accessibility, and microbial physiology

Rota Wagai, Ayaka W. Kishimoto-Mo, Seiichiro Yonemura, Yasuhito Shirato, Syuntaro Hiradate, Yasumi Yagasaki

Research output: Contribution to journalArticle

75 Citations (Scopus)

Abstract

Temperature sensitivity of soil organic matter (SOM) decomposition may have a significant impact on global warming. Enzyme-kinetic hypothesis suggests that decomposition of low-quality substrate (recalcitrant molecular structure) requires higher activation energy and thus has greater temperature sensitivity than that of high-quality, labile substrate. Supporting evidence, however, relies largely on indirect indices of substrate quality. Furthermore, the enzyme-substrate reactions that drive decomposition may be regulated by microbial physiology and/or constrained by protective effects of soil mineral matrix. We thus tested the kinetic hypothesis by directly assessing the carbon molecular structure of low-density fraction (LF) which represents readily accessible, mineral-free SOM pool. Using five mineral soil samples of contrasting SOM concentrations, we conducted 30-days incubations (15, 25, and 35 °C) to measure microbial respiration and quantified easily soluble C as well as microbial biomass C pools before and after the incubations. Carbon structure of LFs (<1.6 and 1.6-1.8 g cm-3) and bulk soil was measured by solid-state 13C-NMR. Decomposition Q10 was significantly correlated with the abundance of aromatic plus alkyl-C relative to O-alkyl-C groups in LFs but not in bulk soil fraction or with the indirect C quality indices based on microbial respiration or biomass. The warming did not significantly change the concentration of biomass C or the three types of soluble C despite two- to three-fold increase in respiration. Thus, enhanced microbial maintenance respiration (reduced C-use efficiency) especially in the soils rich in recalcitrant LF might lead to the apparent equilibrium between SOM solubilization and microbial C uptake. Our results showed physical fractionation coupled with direct assessment of molecular structure as an effective approach and supported the enzyme-kinetic interpretation of widely observed C quality-temperature relationship for short-term decomposition. Factors controlling long-term decomposition Q10 are more complex due to protective effect of mineral matrix and thus remain as a central question.

Original languageEnglish
Pages (from-to)1114-1125
Number of pages12
JournalGlobal Change Biology
Volume19
Issue number4
DOIs
Publication statusPublished - Apr 1 2013
Externally publishedYes

Fingerprint

Physiology
Biological materials
accessibility
Molecular structure
physiology
soil organic matter
decomposition
Decomposition
Soils
respiration
substrate
Minerals
temperature
mineral
enzyme
soil
kinetics
Temperature
Enzyme kinetics
biomass

All Science Journal Classification (ASJC) codes

  • Global and Planetary Change
  • Environmental Chemistry
  • Ecology
  • Environmental Science(all)

Cite this

Linking temperature sensitivity of soil organic matter decomposition to its molecular structure, accessibility, and microbial physiology. / Wagai, Rota; Kishimoto-Mo, Ayaka W.; Yonemura, Seiichiro; Shirato, Yasuhito; Hiradate, Syuntaro; Yagasaki, Yasumi.

In: Global Change Biology, Vol. 19, No. 4, 01.04.2013, p. 1114-1125.

Research output: Contribution to journalArticle

Wagai, Rota ; Kishimoto-Mo, Ayaka W. ; Yonemura, Seiichiro ; Shirato, Yasuhito ; Hiradate, Syuntaro ; Yagasaki, Yasumi. / Linking temperature sensitivity of soil organic matter decomposition to its molecular structure, accessibility, and microbial physiology. In: Global Change Biology. 2013 ; Vol. 19, No. 4. pp. 1114-1125.
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