Molecular-Scale Characterization of Hot-Water-Extractable Organic Matter in Organic Horizons of a Forest Soil
Author(s)
Balaria, Ankit
Johnson, Chris E
Xu, Zhihong
Griffith University Author(s)
Year published
2009
Metadata
Show full item recordAbstract
Hot-water-extractable organic matter (HWEOM) has been shown to be highly correlated with microbial biomass in forest soils. We conducted elemental and 13C solid-state nuclear magnetic resonance spectroscopic analyses to assess the composition and structural chemistry of HWEOM and its variations with soil depth within O horizons in a forest site in New Hampshire. The HWEOM fraction exhibited a higher H/C ratio and higher O-alkyl C proportion than the soil from which it was extracted. It also had a 30 to 40% lower C/N ratio than the whole soil. The relative proportion of O-alkyl C in the HWEOM increased with soil depth in the ...
View more >Hot-water-extractable organic matter (HWEOM) has been shown to be highly correlated with microbial biomass in forest soils. We conducted elemental and 13C solid-state nuclear magnetic resonance spectroscopic analyses to assess the composition and structural chemistry of HWEOM and its variations with soil depth within O horizons in a forest site in New Hampshire. The HWEOM fraction exhibited a higher H/C ratio and higher O-alkyl C proportion than the soil from which it was extracted. It also had a 30 to 40% lower C/N ratio than the whole soil. The relative proportion of O-alkyl C in the HWEOM increased with soil depth in the forest floor, while alkyl C decreased, contrary to the pattern observed for the whole soil. The spectral and elemental properties of HWEOM present in these acidic Spodosols support the hypothesis that HWEOM is largely a mixture of carbohydrates and proteins. We estimate that while HWEOM includes both labile C fractions and microbial biomass, microbial biomass can account for no more than 40% of the C extracted by hot water.
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View more >Hot-water-extractable organic matter (HWEOM) has been shown to be highly correlated with microbial biomass in forest soils. We conducted elemental and 13C solid-state nuclear magnetic resonance spectroscopic analyses to assess the composition and structural chemistry of HWEOM and its variations with soil depth within O horizons in a forest site in New Hampshire. The HWEOM fraction exhibited a higher H/C ratio and higher O-alkyl C proportion than the soil from which it was extracted. It also had a 30 to 40% lower C/N ratio than the whole soil. The relative proportion of O-alkyl C in the HWEOM increased with soil depth in the forest floor, while alkyl C decreased, contrary to the pattern observed for the whole soil. The spectral and elemental properties of HWEOM present in these acidic Spodosols support the hypothesis that HWEOM is largely a mixture of carbohydrates and proteins. We estimate that while HWEOM includes both labile C fractions and microbial biomass, microbial biomass can account for no more than 40% of the C extracted by hot water.
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Journal Title
Soil Science Society of America Journal
Volume
73
Issue
3
Subject
Environmental sciences
Carbon sequestration science
Soil chemistry and soil carbon sequestration (excl. carbon sequestration science)
Biological sciences
Agricultural, veterinary and food sciences