Peatland restoration: controls on sediment production and reductions in carbon and pollutant export

Abstract

Peatlands are an important store of soil carbon, and play a vital role in global carbon cycling, and when located in close proximity to urban and industrial areas, can also act as sinks of atmospherically deposited heavy metals. Large areas of the UK's blanket peat are significantly degraded and actively eroding which negatively impacts carbon and pollutant storage. The restoration of eroding UK peatlands is a major conservation concern, and over the last decade measures have been taken to try to control erosion and restore large areas of degraded peat. This study utilizes a sediment source fingerprinting approach to assess the effect of restoration practices on sediment production, and carbon and pollutant export in the Peak District National Park, southern Pennines (UK). Suspended sediment was collected using time integrated mass flux samplers (TIMS), deployed across three field areas which represent the surface conditions exhibited through an erosion-restoration cycle: (i) intact; (ii) actively eroding; and (iii) recently re-vegetated. Anthropogenic pollutants stored near the peat's surface have allowed material mobilized by sheet erosion to be distinguished from sediment eroded from gully walls. Re-vegetation of eroding gully systems is most effective at stabilizing interfluve surfaces, switching the locus of sediment production from contaminated surface peat to relatively 'clean' gully walls. The stabilization of eroding surfaces reduces particulate organic carbon (POC) and lead (Pb) fluxes by two orders of magnitude, to levels comparable with those of an intact peatland, thus maintaining this important carbon and pollutant store. The re-vegetation of gully floors also plays a key role in decoupling eroding surfaces from the fluvial system, and further reducing the flux of material. These findings indicate that the restoration practices have been effective over a relatively short timescale, and will help target and refine future restoration initiatives.

The impact of ditch blocking on fluvial carbon export from a UK blanket bog

“…POC fluxes were spatially and temporally variable, but high concentrations generally coincided with low or flows so did not contribute substantively to export. In areas of active peat erosion, there is strong evidence that POC export can be reduced by restoring hydrological function and vegetation cover (Shuttleworth, Evans, Hutchinson, & Rothwell, ; Worrall et al, ). However, no ditches were observed to be actively eroding at the start of our study, and although weir pools construction could have triggered a flush of POC release, this was not evident in the data.…”

The effective oxidation state of a peatland

“…However, at least one POM sample did show signs of that POM included vegetation, which is readily explained if a component of runoff in a peat catchment comes across the soil surface and entrains litter material. Shuttleworth et al [] have shown that the relative contribution of surface and gully wall peat to POM depends on the level of vegetation cover.…”

High fluvial export of dissolved organic nitrogen from a peatland catchment with elevated inorganic nitrogen deposition

“…Varying degrees of degradation including vegetation loss, widespread gullying, high sediment and DOC losses, etc. Rothwell et al, 2008a;Allott et al, 2009;Shuttleworth et al, 2014), have been reported in the headwaters of the Kinder plateau. Approximately 22% of the Kinder plateau (United Utilities, 2011) and~13% (52 ha) of the Kinder River catchment is bare and eroding peat.…”