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Impact of water table depth on forest soil methane turnover in laboratory soil cores deduced from natural abundance and tracer 13C stable isotope experiments.

Research output: Contribution to journalJournal article

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  • Niall P. McNamara
  • Paul M. Chamberlain
  • Trevor G. Piearce
  • Darren Sleep
  • Helaina I. Black
  • David S. Reay
  • Phil Ineson
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<mark>Journal publication date</mark>2006
<mark>Journal</mark>Isotopes in Environmental and Health Studies
Issue number4
Volume42
Number of pages12
Pages (from-to)379-390
Publication statusPublished
Original languageEnglish

Abstract

We investigated turnover of methane (CH4) in soils from a poorly drained UK forest. In situ, this forest exhibited a negligible soil-atmosphere CH4 flux, whereas adjacent grassland plots were sources of CH4. We hypothesised that the forest plots exhibited reduced anaerobic CH4 production through water-table draw down. Consequently, we exposed soil cores from under oak to high and low water-table conditions in the laboratory. Methane fluxes increased significantly in the high water-table (1925±1702 μg CH4 m-2 h-1) compared to the low one (-3.5±6.8 μg CH4 m-2 h-1). Natural abundance δ13C values of CH4 showed a strong depletion in high water-table cores (-56.7±2.9 ‰) compared to methane in ambient air (-46.0 ‰) indicative of methanogenic processes. The δ13C values of CH4 from low water-table cores (δ13C-46.8±0.2 ‰) was similar to ambient air and suggested little alteration of headspace CH4 by the soil microbial community. In order to assess the CH4 oxidizing activity of the two treatments conclusively, a 13CH4 spike was added to the cores and 13CO2 production was measured as the by-product of CH4 oxidation. 13CH4 oxidation rates were 57.5 (±12.7) and 0.5 (±0.1) μg CH4 m-2 h-1 for high and low water-tables, respectively. These data show that the lower water-table hydrology treatment impacted methanogenic processes without stimulating methanotrophy.