Impact of gully erosion on carbon sequestration in blanket peatlands

Abstract

Over 50% of UK soil carbon is stored in peatland systems and 75% of these peatlands are upland blanket bog. The upland blanket bogs of the UK have suffered severe erosion over the last millennium so that they are widely dissected by gully systems. Gully erosion entails primary removal of particulate carbon from the peatland system but also has secondary effects in that it enhances drainage and lowers water tables, potentially enhancing decomposition of surface peats. This paper exploits recent high resolution mapping of the gully erosion on the Bleaklow Plateau in the southern Pennines and existing data on peat growth rates in the area to assess the impact of gully erosion on peatland carbon balance and the relative importance of primary and secondary impacts of gullying on carbon sequestration. The results indicate that gully erosion during the last millennium has shifted the Bleaklow Plateau from being a net sink of carbon (-20. ). The relative importance of gullying impacts can be expressed as follows: particulate organic carbon (POC) flux > change in gully net ecosystem exchange >> loss of gully margin carbon sequestration. The implication of these findings is that the magnitude of the potentially reversible impacts of gully erosion (reduced carbon fixation due to vegetation loss and ongoing erosional loss of POC) far exceed the effects associated with irreversible morphological change (enhanced peat decomposition in gully margin locations). KEY WORDS: Blanket peat · Gully erosion · Carbon balance · Carbon sequestration Resale or republication not permitted without written consent of the publisher Contribution to CR Special 24 'Climate change and the British Uplands'

Climate change and the British Uplands: evidence for decision-making

“…The loss of POC into rivers in eroding systems may be higher than previously thought (Billett et al 2010). Evans & Lindsay (2010) highlight the POC losses from gully erosion and decomposition of surface peats. The upland blanket bogs of the UK have suffered severe erosion due to land use and extensive drainage in recent centuries and in some regions they are widely dissected by gully systems.…”

“…These areas may become more suitable for agriculture as the climate becomes warmer, which would increase pressures from land management, although this has not been assessed in this Special. Excessive burning, overgrazing and drainage can lead to loss of vegetation cover and rapid erosion of peat, sometimes resulting in deep and extensive gully erosion (Billett et al 2010, Evans & Lindsay 2010, Smith et al 2010b, Yallop et al 2010. Climate change may exacerbate erosion where vegetation cover is already reduced e.g.…”

Restoration effects on water table depths and CO2 fluxes from climatically marginal blanket bog

“…In association with this, large losses of particulate organic carbon in upland catchments (e.g. Evans and Lindsay 2010b) have resulted in significant reductions in the water storage volumes of upland reservoirs (e.g. Yeloff et al 2005) through sediment deposition.…”

Model inter-comparison between statistical and dynamic model assessments of the long-term stability of blanket peat in Great Britain (1940–2099)

“…A full carbon budget for this has not yet been calculated, although long-term monitoring is underway. More site details can be found in Evans et al (2006) and Billett et al (2010 (Tallis 1994) suggest that most pristine sites are a net C sink with a mean rate of + 20.3 g C m -2 yr -1 (Evans & Lindsay 2010b, this Special) with other estimates varying between + 70 to +102 g C m -2 yr -1 (Billett et al 2010). The sites are described in more detail in Daniels et al (2008).…”