PubMed Health⌕ Search

Biomedical subjects

David S Reay

Publications and source records attributed to David S Reay.

8 recordsLinked to original sources
PubMed2006

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

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 mug CH4 m(-2) h(-1)) compared to the low one (-3.5+/-6.8 microg CH4 m(-2) h(-1)). Natural abundance delta13C values of CH4 showed a strong depletion in high water-table cores (-56.7+/-2.9 per thousand) compared to methane in ambient air (-46.0 per thousand) indicative of methanogenic processes. The delta13C values of CH4 from low water-table cores (delta13C-46.8+/-0.2 per thousand) 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) microg 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.

Carbon Isotopes↗
PubMed2003

Sinking methane.

Concentrations of the powerful greenhouse gas, methane, in our atmosphere have doubled since the beginning of the industrial age. Reducing these levels is a vital part of global efforts to combat global warming. Could we make use of the Earth's own methane sinks?

Atmosphere↗
PubMed2002

Costing climate change.

Debate over how, when, and even whether man-made greenhouse-gas emissions should be controlled has grown in intensity even faster than the levels of greenhouse gas in our atmosphere. Many argue that the costs involved in reducing emissions outweigh the potential economic damage of human-induced climate change. Here, existing cost-benefit analyses of greenhouse-gas reduction policies are examined, with a view to establishing whether any such global reductions are currently worthwhile. Potential for, and cost of, cutting our own individual greenhouse-gas emissions is then assessed. I find that many abatement strategies are able to deliver significant emission reductions at little or no net cost. Additionally, I find that there is huge potential for individuals to simultaneously cut their own greenhouse-gas emissions and save money. I conclude that cuts in global greenhouse-gas emissions, such as those of the Kyoto Protocol, cannot be justifiably dismissed as posing too large an economic burden.

Air Pollutants↗
PubMed2002

Identification of active methylotroph populations in an acidic forest soil by stable-isotope probing.

Stable-isotope probing (SIP) is a culture-independent technique that enables the isolation of DNA from micro-organisms that are actively involved in a specific metabolic process. In this study, SIP was used to characterize the active methylotroph populations in forest soil (pH 3.5) microcosms that were exposed to (13)CH(3)OH or (13)CH(4). Distinct (13)C-labelled DNA ((13)C-DNA) fractions were resolved from total community DNA by CsCl density-gradient centrifugation. Analysis of 16S rDNA sequences amplified from the (13)C-DNA revealed that bacteria related to the genera Methylocella, Methylocapsa, Methylocystis and Rhodoblastus had assimilated the (13)C-labelled substrates, which suggested that moderately acidophilic methylotroph populations were active in the microcosms. Enrichments targeted towards the active proteobacterial CH(3)OH utilizers were successful, although none of these bacteria were isolated into pure culture. A parallel analysis of genes encoding the key enzymes methanol dehydrogenase and particulate methane monooxygenase reflected the 16S rDNA analysis, but unexpectedly revealed sequences related to the ammonia monooxygenase of ammonia-oxidizing bacteria (AOB) from the beta-subclass of the PROTEOBACTERIA: Analysis of AOB-selective 16S rDNA amplification products identified Nitrosomonas and Nitrosospira sequences in the (13)C-DNA fractions, suggesting certain AOB assimilated a significant proportion of (13)CO(2), possibly through a close physical and/or nutritional association with the active methylotrophs. Other sequences retrieved from the (13)C-DNA were related to the 16S rDNA sequences of members of the Acidobacterium division, the beta-Proteobacteria and the order Cytophagales, which implicated these bacteria in the assimilation of reduced one-carbon compounds or in the assimilation of the by-products of methylotrophic carbon metabolism. Results from the (13)CH(3)OH and (13)CH(4) SIP experiments thus provide a rational basis for further investigations into the ecology of methylotroph populations in situ.

Ammonia↗