Fluvial carbon flux from headwater peatland streams: significance of particulate carbon flux

Abstract

The extensive blanket peatlands of the UK uplands account for almost half of total national terrestrial carbon storage. However, much of the blanket peat is severely eroded so that the contemporary role of the peatland system in carbon sequestration is compromised by losses of organic carbon in dissolved (DOC) and particulate (POC) form in the fluvial system. This paper presents the first detailed assessment of dissolved and organic carbon losses from a severely eroded headwater peatland (River Ashop, South Pennines, UK). Total annual fluvial organic carbon losses range from 29–106 Mg C km,‐2 decreasing from the headwaters to the main catchment outlet. In contrast to less eroded systems fluvial organic carbon flux is dominated by POC. POC:DOC ratios decrease from values of 4 in the headwaters to close to unity at the catchment outlet. These results demonstrate the importance of eroding headwater sites as sources of POC to the fluvial system. Comparison with a range of catchment characteristics reveals that drainage density is the best predictor of POC:DOC but there is scatter in the relation in the headwaters. Steep declines in specific POC yield from headwater catchments are consistent with storage of POC within the fluvial system. Key to the significance of fluvial carbon flux in greenhouse gas budgets is understanding the fate of fluvial carbon. Further work on the fate of POC and the role of floodplains in fluvial carbon cycling is urgently required. Copyright © 2012 John Wiley & Sons, Ltd.

Comparison of soil erosion models used to study the Chinese Loess Plateau

“…However, soil systems are facing erosion threats under climate change and intensified land management (Oldeman, 1994, Yang et al, 2003. Soil erosion leads to serious issues, including the reduction of soil depth, soil organic matter and nutrients (Pimentel, 2006), reduced crop yields (Wang et al, 2006), the loss of arable land and biodiversity (Pimentel et al, 1995), exacerbated rural poverty (Meng, 1997), water pollution (Rothwell et al, 2005) and enhancement of terrestrial carbon release (Pawson et al, 2012). Sediment transport and deposition may degrade streams, lakes, reservoirs, and estuaries (Uri, 2001).…”

Sporadic hotspots for physico-chemical retention of aquatic organic carbon: from peatland headwater source to sea

“…The remaining components of fluvial C export are particulate organic carbon (POC) and dissolved inorganic C (DIC) species: bicarbonate (HCO 3 -) carbonate (CO 3 2-) or gaseous CO 2 , depending on pH. Heavily eroded peatlands are significant contributors of POC to rivers and streams, and in degraded environments POC may be the main contributor to fluvial C export (Pawson et al 2012). While dissolved gaseous C sourced from peaty soils is readily lost from the stream system to the atmosphere (Hope et al 2001), the fate of organic forms of fluvial C is more complex and may have a significant climate forcing effect if processes within the water column convert POC and DOC to CO 2 .…”

“…Evidence for POC removal in peat-influenced freshwater systems is limited, with estimates ranging from \5 to[50 % removal obtained from different studies (Dawson et al 2004(Dawson et al , 2012Worrall and Moody 2014). Pawson et al (2012) demonstrated rapid removal of POC and decreasing POC:DOC ratios in headwaters of eroding peatlands, indicating either deposition of POC to bottom sediments or conversion of POC to DOC.…”

Prediction of blanket peat erosion across Great Britain under environmental change

“…There are around 3500 km 2 of eroded blanket peat in the British Isles (Tallis, 1998). Peat erosion impacts water quality leading to high turbidity and heavy metal pollution (Pattinson et al, 1994;Rothwell et al, 2007;Rothwell et al, 2005), disturbed river ecology (Ramchunder et al, 2009), sedimentation of reservoirs (Labadz et al, 1991), and loss of carbon Pawson et al, 2012). There is therefore a large amount of investment aimed at reducing erosion losses from blanket peatlands (Parry et al, 2014).…”