Wednesday, 31 October 2012

Coring for carbon

Here is the target of Scott’s coring, pictured in last Saturday’s blog; a core of sediment drilled out from the bottom of a pond at Hauxley Nature Reserve. The ponds were dug in a field that was back-filled after the Hauxley coal mine closed. The soil that was used for this was very clayey. To the right you can see the sheer, glistening clay from deeper in the core. To the left side of the core the clay is conspicuously gnarly and flecked with bits of plant; this is the sediment from the bed of the pond and immediately below. The ponds started as bare, square holes but since their creation in 1994 have colonised with amphibious mosses and grasses, or, occasionally, submerged plants such as water buttercup, Ranunculus aquatilitis, and Stoneworts, Chara. As the plants die their debris is mired in the sediment at the bottom of the pond. Where thick swards of moss have covered the bed of the pond the mud underneath has become black and foetid because of a lack of oxygen and these conditions slow natural decay. Hence the top of the core has the accumulated plant fragments, creating the darker, rougher texture. Coring is surprisingly hard work in the clinging clay but the greater challenge is to measure how much organic carbon the plant fragments have locked into the mud. The little ponds are very verdant and productive so the plant growth has the potential to take significant amounts of carbon dioxide out of the air and down into the mud when the plants die. One little pond may not seem very important, but there are a lot of little ponds out there.....

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