Managing peatland vegetation for drinking water treatment

Abstract

Peatland ecosystem services include drinking water provision, flood mitigation, habitat provision and carbon sequestration. Dissolved organic carbon (DOC) removal is a key treatment process for the supply of potable water downstream from peat-dominated catchments. A transition from peat-forming Sphagnum moss to vascular plants has been observed in peatlands degraded by (a) land management, (b) atmospheric deposition and (c) climate change. Here within we show that the presence of vascular plants with higher annual above-ground biomass production leads to a seasonal addition of labile plant material into the peatland ecosystem as litter recalcitrance is lower. The net effect will be a smaller litter carbon pool due to higher rates of decomposition, and a greater seasonal pattern of DOC flux. Conventional water treatment involving coagulation-flocculation-sedimentation may be impeded by vascular plant-derived DOC. It has been shown that vascular plant-derived DOC is more difficult to remove via these methods than DOC derived from Sphagnum, whilst also being less susceptible to microbial mineralisation before reaching the treatment works. These results provide evidence that practices aimed at re-establishing Sphagnum moss on degraded peatlands could reduce costs and improve efficacy at water treatment works, offering an alternative to ‘end-of-pipe’ solutions through management of ecosystem service provision.

Sources of dissolved organic carbon (DOC) in a mixed land use catchment (Exe, UK)

“…Our comparison of litter carbon stocks between the peatland site at Spooners and the oak woodland at Tarr Steps suggest a similar amount of autumnal litter production. It is worth noting, however, that sampling took place during leaf-fall in the woodland and therefore these results are likely to be an annual maximum, whereas the peatland site has sources of year-round litter production so is likely to be less seasonal in litter quantity and thus DOC flux (Ritson et al, 2016). Our results on extractable DOC, C:N and BDOC of typical UK oak forest vegetation add to the findings of Pinsonneault et al, (2016) who published similar data for peatland vegetation.…”

“…comparable BDOC values to peatland species with some exceptions as in our earlier work we noted Sphagnum Spp. produces DOC which is highly labile with BDOC ~90% (Ritson et al, 2016). These data add to the growing body of work needed to understand the likely fate of DOC from different catchment sources.…”

“…and BDOC of this WEOM. We did not complete this additional analysis for the peatland site as we have already published data concerning C:N, WEOM and BDOC for these species (Ritson et al, 2016).…”

“…Peatland and woodland sites were identified from the catchment survey as adding significantly higher DOC concentrations to the main channel and were therefore investigated further with respect to the sources of DOC in these sub-catchments. Ritson et al 2016 with the data on litter amounts per m 2 which give estimates of litter carbon stocks. These were 527 ± 91 gC m -2 for the peatland site and 364 ± 101 gC m -2 at the forested site with ten replicates at each.…”

“…4 was supplemented with values for peatland species in our previous work (Ritson et al, 2016) We then estimated carbon stocks at the two sites using the %C and bulk density at the two depths The water samples collected at the same time as the vegetation and soil samples are summarised in Table 6.…”