PARENT SESSION
Symposium 2: Soil Biodiversity: Scaling from microbe to ecosystem
Organized by: A Fitter, C Kennan, and H Jones
Monday, August 8, 8:00 AM - 11:30 AM, Meeting Room 517 B, Level 5, Palais des congrès de Montréal

Stable isotope approaches: Identifying key players in the C cycle.

Ineson, Philip¹, Killham, Ken², Prosser, Jim², ¹ University of York, York, UK² University of Aberdeen, Aberdeen, UK

ABSTRACT- The task of linking a diverse and microscopic population of organisms to their known functions of global significance is extremely difficult, yet immensely important. We argue that the understanding of the activities of soil organisms is largely limited by technical barriers preventing our insights into the intrinsically opaque. In this paper we review some of these technical developments, with specific examples of how they are being applied to increase our understanding of the carbon cycle. The examples are mainly taken from a recent Soil Biodiversity research initiative at Sourhope in the U.K., funded by the Natural Environment Research Council, and resulting in the 'most highly biologically characterised hectare of soil in the world'. The project involved a consortium of research groups working in a closely co-ordinated programme of research at Sourhope, using the same plots, plant species and basic experiments. The research has succeeded in pioneering novel in situ 13C techniques for studying the terrestrial C cycle, and linking ecosystem fluxes to soil biodiversity. We shall describe the development of in situ pulse ¹³CO₂ labelling, with subsequent field monitoring of ¹³CO₂ release, including a novel technique to selectively label a single species of plant within a mixed grassland sward. We shall particularly focus on a liming treatment at the site where we found, in the short-term, the return of ¹³C-CO₂ to the atmosphere via ecosystem respiration was significantly enhanced by the lime treatment. These data support other data from the site showing a decrease in total soil organic C under the lime treatment, suggesting that these short-term in situ approaches may provide insight into longer-term C store changes. Having delivered a ¹³C pulse label to the soil via different plant species, it then becomes possible to trace the ¹³C pulse into both the biota and individual molecules in the soil; results from these investigations together with predictions from a an isotope-based trophic model will also be presented.

Key words: soil, biodiversity, stable, isotopes