The protection of tropical wetlands including below ground peats is a key internationally agreed strategy in reducing CO2 emissions from deforestation and land use change and therefore slowing climate change. Whilst numerous estimates of carbon stores exist, they often only focus on carbon close to the soil surface (0 to 0.5 m) or from mangrove swamps and seagrass meadows (Blue Carbon) environments. Consequently, surprisingly little is known about the carbon accumulating at depth (0 to 10 m) below tropical forests and particularly those in Central America.
A joint team of scientists led by Chris Vane (BGS) and Sofie Sjogersten (University of Nottingham, Biosciences) took on this challenge and undertook a pilot coring campaign in the extensive San San Pond Sak tropical peatland situated in Bocas del Toro, NE Panama. Coring in pristine freshwater swamp forest requires a high tolerance for biting insects, a keen eye to avoid the occasional snake and a good sense of direction to avoid getting lost. Nevertheless, the team cut a trail with the help of a local guide and hand-cored a lateral sequence spanning five vegetation zones. |
| From L-R: Eyelash pit viper; Litter degradation series |
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| Sofie finds quality peat at depth |
Upon return to the Organic Geochemistry team including visiting University of Nottingham MSci student Abbie Upton measured the carbon stored in each vegetation zone and assessed changes in organic matter input and decomposition rates down profile using Rock-Eval (6) pyrolysis, lipid compound distributions and infrared spectroscopy. Usually coastal mangroves are cited as among the most carbon-rich forests in the tropics with values around 1,023 Mg carbon per hectare (Mg ha-1) however we found that mixed swamp forest (1884 Mg ha-1), Camponsperma forest (1695 Mg ha-1) were even richer and that carbon accumulation increases with burial time/depth because selective decomposition of carbohydrates by bacteria effectively increases the proportion of polymerised aromatic structures as the peat mature sand stabilises. The findings of this research have just been published in the Journal Geoderma.
Upton, A., Vane, C.H., Girkin, N., Turner, B., Sjogersten, S. 2018 Does litter input determine carbon storage and peat organic chemistry in tropical peatlands. Geoderma, 326, 76-87. https://doi.org/10.1016/j.geoderma.2018.03.030
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