The significance of organic carbon and nutrient export from peatland-dominated landscapes subject to disturbance

Abstract

Abstract. The terrestrial-aquatic interface is a crucial environment in which to consider the fate of exported terrestrial carbon in the aquatic system. To a large extent the fate of dissolved organic carbon (DOC) may be controlled by nutrient availability. However, peat-dominated headwater catchments are normally considered of low nutrient status and thus there is little data on the interaction of DOC and nutrients. Here we present nutrient and DOC data exported from two UK catchments, both dominated by peat headwaters, but of differing land-use. Glen Dye is a moorland with no trees; Whitelee has partially forested peats and peaty podzols, and is now undergoing development to host Europe's largest on-shore windfarm, the Whitelee Windfarm. There are significant linear relationships between DOC and soluble reactive phosphorus and nitrate concentrations in the drainage waters, but inter-catchment differences exist. Changes in the pattern of nutrient and carbon export in Whitelee suggest that disturbance of peatlands soils can impact the receiving water and that nutrient export does not increase in a stoichiometric manner that will promote increase in biomass. As such the changes are more likely to cause increased aquatic respiration, and thus lead to higher dissolved CO2 concentrations (and therefore CO2 efflux). Hence disturbance of terrestrial carbon stores may also impact the gaseous carbon cycle. Confirming the source of carbon and nutrients in these study sites is not possible. However, nearby 14C measurements are in keeping with other published literature values from similar sites which show C in DOM exported from peatlands is predominantly modern, and thus supports an interpretation that nutrients, additional to carbon, are derived from shallow soils. Estimates of organic carbon loss from Whitelee catchments to the drainage waters suggest a system where losses are approaching likely sequestration rates. We suggest such sequestration assessment should inform the decision-making tools required prior to development of terrestrial carbon stores.

Hydrogeological challenges in a low-carbon economy

“…This is consistent with the findings of chemical and isotopic studies of peatland drainage waters (e.g. Waldron et al 2009), which have revealed that, although disturbed peatlands do release more dissolved and suspended organic carbon to downstream catchments than undisturbed ones, the scale of carbon loss is a lot more modest than was originally feared. However, as the site studied by Waldron et al (2009) had only recently been disturbed, that finding may not transfer to sites subject to longer periods of disturbance.…”

“…Waldron et al 2009), which have revealed that, although disturbed peatlands do release more dissolved and suspended organic carbon to downstream catchments than undisturbed ones, the scale of carbon loss is a lot more modest than was originally feared. However, as the site studied by Waldron et al (2009) had only recently been disturbed, that finding may not transfer to sites subject to longer periods of disturbance. Thus further research is needed, on a wider range of sites and over longer time scales, to determine whether such conclusions are indeed generally valid for upland peat ecosystems affected by wind turbine developments.…”

“…This relates to the potential for installation of upland wind farms to disturb the hydrology of peatland ecosystems (e.g. Waldron et al 2009). These peatlands often overlie low-permeability strata (bedrock and/or drift deposits, notably glacial till) and as such have tended to be neglected by much of the hydrogeological profession.…”

Peatlands and the carbon cycle: from local processes to global implications – a synthesis

“…In addition, DOC impacts water quality in terms of color, taste, safety, and aesthetic value, as well as altering the acid-base and metal complexation characteristics of soil water and stream water. Together with the C losses considerable nutrient export may occur as well, potentially increasing impacts on aquatic diversity downstream (Waldron et al, 2008). DOC accumulates in peat pore waters and is flushed out by water movement, with concentrations often greatest following periods of warm, dry conditions when DOC has had time to accumulate.…”

“…Many temperate peatlands have been drained for commercial exploitation such as agriculture, forestry or more recently windmill farming (Waldron et al, 2008). This has resulted in profound effects on peatland biogeochemistry, Gorham (1995), (B).…”