Friday, 1 March 2013
Pete explores pond types
Up at Druridge Bay the seasons are teetering. Winter’s sodden fields are still gluey wet, swathes of wheat shoots bedraggled or long dead. The calls of geese and the widgeons’ whistles carry in on the wind, but the robins are singing for spring and busy swarms of goldfinches decorate the headlines. There is a growing busyness. January and February have been relatively dry so we have started a central aim of our research: characterising how different pond types vary in their carbon capture. “Pond types” sounds like another quagmire as bad as lakes vs ponds in the last blog. How to describe ponds depends on what you want to know: could be done for their conservation value using scores for lists of invertebrates or plants, or by the nutrient levels or pond histories. We are starting with four broad types: (1) ponds in arable fields, which are usually temporary and support few plants, (2) ponds in pasture, often covered with fodder grasses but some amphibious species too, (3) the dune slacks and flashes overlying sand soil, vulnerable to occasional brackish overflows and (4) the permanent, plant rich wetlands. The photos show Pete coring a grass ley and amongst dune slacks at Blakemoor. Sounds easy but we have hit a snag immediately. The corer works well, screwing down into the mud but when we gently teased it out the top layers of mud dribble out. These upper layers are especially dark and rich in organic debris, we must capture their presence in the samples. Research is like that. Sounds easy, go out, drill in a core, take out the sediment, go back to the lab..... I like the practical struggle, working out how to engineer the equipment, which is often more a visit to B&Q DIY than Large Hadron Collider.
The recce proved useful though, revealing dark, perhaps anoxic mud under the apparently normal sediment surface of the grassy ponds and the distinctly sandy soils underlying the dune slacks. The photo above shows the grainy sand to the right in a core from the dune slacks under about 10cm of gooier mud.