Fluvial organic carbon fluxes from oil palm plantations on tropical peatland

Cook, Sarah; Whelan, Mick J.; Evans, Chris D. ORCID: https://orcid.org/0000-0002-7052-354X; Gauci, Vincent; Peacock, Mike; Garnett, Mark H.; Kho, Lip Khoon; Teh, Yit Arn; Page, Susan E.. 2018 Fluvial organic carbon fluxes from oil palm plantations on tropical peatland [in special issue: Biogeochemical processes in highly dynamic peat-draining rivers and estuaries in Borneo] Biogeosciences, 15 (24). 7435-7450. https://doi.org/10.5194/bg-15-7435-2018

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Abstract/Summary

Intact tropical peatlands are dense long-term stores of carbon. However, the future security of these ecosystems is at risk from land conversion and extensive peatland drainage. This can enhance peat oxidation and convert long-term carbon sinks into significant carbon sources. In Southeast Asia, the largest land use on peatland is for oil palm plantation agriculture. Here, we present the first annual estimate of exported fluvial organic carbon in the drainage waters of four peatland oil palm plantation areas in Sarawak, Malaysia. Total organic carbon (TOC) fluxes from the plantation second- and third-order drains were dominated (91 %) by dissolved organic carbon (DOC) and ranged from 34.4 ± 9.7 C m−2 yr−1 to 57.7 %, 16.3 g C m−2 yr−1 (± 95 % confidence interval). These fluxes represent a single-year survey which was strongly influenced by an El Ninõ event and therefore lower discharge than usual was observed. The magnitude of the flux was found to be influenced by water table depth, with higher TOC fluxes observed from more deeply drained sites. Radiocarbon dating on the DOC component indicated the presence of old (pre-1950s) carbon in all samples collected, with DOC at the most deeply drained site having a mean age of 735 years. Overall, our estimates suggest fluvial TOC contributes ∼ 5 % of total carbon losses from oil palm plantations on peat. Maintenance of high and stable water tables in oil palm plantations appears to be key to minimising TOC losses. This reinforces the importance of considering all carbon loss pathways, rather than just CO2 emissions from the peat surface, in studies of tropical peatland land conversion.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.5194/bg-15-7435-2018
UKCEH and CEH Sections/Science Areas:	Soils and Land Use (Science Area 2017-)
ISSN:	1726-4170
Additional Information. Not used in RCUK Gateway to Research.:	Open Access paper - full text available via Official URL link.
NORA Subject Terms:	Ecology and Environment Agriculture and Soil Science
Date made live:	18 Jan 2019 11:53 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/522050

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