Fluvial organic carbon fluxes from oil palm plantations on tropical peatland

Cook, S., Whelan, M. J., Evans, C. D., Gauci, V., Peacock, M., Garnett, M. H. , Kho, L. K., Teh, Y. A. and Page, S. E. (2018) Fluvial organic carbon fluxes from oil palm plantations on tropical peatland. Biogeosciences, 15(24), pp. 7435-7450. (doi: 10.5194/bg-15-7435-2018)

Abstract

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: Articles
• Additional Information: This work was supported by the Natural Environment Research Council (NERC; grant: X402NE53), the Malaysian Oil Palm Board (grant: R010913000) and the AXA Research Fund. We are grateful to the University of Aberdeen, the University of St. Andrews, Sarawak Oil Palms Berhad for additional financial support.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Garnett, Dr Mark
• Authors: Cook, S., Whelan, M. J., Evans, C. D., Gauci, V., Peacock, M., Garnett, M. H., Kho, L. K., Teh, Y. A., and Page, S. E.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• Journal Name: Biogeosciences
• Publisher: Copernicus Publications
• ISSN: 1726-4170
• ISSN (Online): 1726-4189
• Copyright Holders: Copyright © 2018 The Authors
• First Published: First published in Biogeosciences 15(24):7435-7450
• Publisher Policy: Reproduced under a Creative Commons License