Geomorphic controls on fluvial carbon exports and emissions from upland swamps in eastern Australia

Kirsten Cowley; Arun Looman; Damien T Maher; Kirstie Fryirs

doi:10.1016/j.scitotenv.2017.08.133

Geomorphic controls on fluvial carbon exports and emissions from upland swamps in eastern Australia

Sci Total Environ. 2018 Mar 15:618:765-776. doi: 10.1016/j.scitotenv.2017.08.133. Epub 2017 Oct 16.

Authors

Kirsten Cowley¹, Arun Looman², Damien T Maher³, Kirstie Fryirs⁴

Affiliations

¹ Department of Environmental Sciences, Macquarie University, North Ryde, NSW 2109, Australia. Electronic address: kirsten.cowley@mq.edu.au.
² School of Environment, Science and Engineering, Southern Cross University, PO Box 157, Lismore, NSW 2480, Australia.
³ Southern Cross Geoscience, Southern Cross University, Lismore, New South Wales 2480, Australia; National Marine Science Centre, School of Environment, Science and Engineering, Southern Cross University, Coffs Harbour, NSW, Australia.
⁴ Department of Environmental Sciences, Macquarie University, North Ryde, NSW 2109, Australia.

PMID: 29046232
DOI: 10.1016/j.scitotenv.2017.08.133

Abstract

Temperate Highland Peat Swamps on Sandstone (THPSS) are upland wetlands, similar to fens in the Northern Hemisphere and are found at the headwaters of low-order streams on the plateaus of Eastern Australia. They are classified as endangered ecological communities under State and National legislation. Previous works have identified particular geomorphic characteristics that are important to carbon storage in these low energy sediment accumulation zones. Changes in the geomorphic structure of THPSS, such as channelisation, may have profound implications for carbon storage. To assess the effect of channelisation on carbon budgets in these ecosystems it is essential to identify and quantify differences in carbon export, emissions and stocks of carbon of intact swamps and those that have become channelised. We undertook seasonal sampling of the perched swamp aquifers and surface waters of two intact swamps and two channelised fills in the Blue Mountains of New South Wales, Australia, to investigate differences in carbon exports and emissions between the two swamp types. We found that channelised fills' mean CO₂ emissions were almost four times higher than intact swamps with mean CH₄ emissions up to five times higher. Annual fluvial carbon exports for channelised fills were up to 18 times that of intact swamps. Channelised fill exports and emissions can represent up to 2% of the total swamp carbon stocks per annum which is 40 times higher than the intact swamps. This work clearly demonstrates that changes in geomorphic structure brought about by incision and channelisation results in profound changes to the carbon storage function of THPSS.

Keywords: Anthropogenic modification; Carbon budget; Carbon dioxide; Carbon export; Greenhouse gases; Methane; Peatland; Wetland.