Environmental ecology

Dr Deborah Pearce

 

We study methane and carbon dioxide production in, transport through, and efflux from peatlands. That CH4 and CO2 are produced during decay in peatlands and that there are seasonally and spacially changing effluxes of both gases is not new. However there has been no attempt to locate or to quantify the sources of the CH4 below the surface. Profiles of gas concentrations through surface and deep peat, and of effluxes, all measurements with a mass spectrometer in the field at a single site, has allowed us to infer the location and nature of the processes of production, movement and disappearance of gases in peat.

We have shown that efflux of CH4 and CO2 from a peatland surface consists of two components: a larger seasonal one produced in a thin layer just below the water table, and a smaller-non seasonal one from the continued decay of the main mass of peat. We are now using molecular tools to relate gaseous concentrations with microbial communities. Work in this area is joint with Dr Shirley McCready (create link). I have a long-standing interest in adaptations of plants to waterlogging. Work in this area is joint with Dr David Evans and Dr Mike Jackson (IACR).

Projects

The role of sphagnan in preventing decay of anoxic peat:

Although there is continuous decay in anoxic peat it is very slow. We are investigating whether the extremely slow decay of anoxic peat is due to reductions in essential metals and amino-nitrogen due to their sequestration by sphagnan and discover which factors limit the rate of decay.

Characterising bubbles in peat:

A zone of intense CH4 production just below the water table is thought to contribute significantly to the overall flux from peat bogs. We are using membrane inlet Quadrupole Mass Spectrometry (QMS) to confirm the existence of bubbles, their gaseous concentrations and their localisation at fine spatial resolution within intact peat cores. We use the distribution of the noble gas Argon (Ar) and the distinct QMS responses to dissolved and gaseous (bubble) phases to identify trapped bubbles with a resolution of 0.6 mm.

The importance of cation exchange in peat decay:

Cation availability is hypothesised to limit CH4 production in peatlands. We quantify total, soluble and exchangeable cation concentrations, together with Exchange Site Saturation Levels (ESSL) and total organic fractions within profiles from an ombotrophic peat bog in Scotland and compare these with profiles from a calcareous fen and a transitional valley mire in south-central England.

Spatial variability in peat:

The vertical distribution of gases in the upper 300 mm of peat comprising the zone of peak production has been extensively studied at a fine scale resolution using Quadrupole Mass Spectrometry (QMS). The variability in the dissolved gas concentration profiles is high and we are relating it to physical structure within the peat and we are using in Situ Hybridisation techniques to relate the abundance of CH4 producing and consuming microbes to the gas concentration profiles to explain this spatial variability.

 

People

 

Funding

  • NERC (grant and studentship)
  • Oxford Brookes University

 

Collaborations

 

Publications

Dr Deborah Pearce

CONTACT US

dpearce@brookes.ac.uk
+44 (0) 1865 483965
Publications