Reply on RC2

Amy Pickard

doi:10.5194/bg-2021-65-ac5

Abstract

Direct land to atmosphere carbon exchange has been the primary focus in previous studies of peatland disturbance and subsequent restoration. However, loss of carbon via the fluvial pathway is a significant term in peatland carbon budgets and requires consideration to assess the overall impact of restoration measures. This study aimed to determine the effect of peatland land management regime on aquatic carbon concentrations and fluxes in an area within the UK’s largest tract of blanket bog, the Flow Country of N. Scotland. Three sub catchments were selected to represent peatland land management types: non-drained, drained and restoration (achieved through drain blocking and tree-removal). Water samples were collected on a fortnightly basis from September 2008 to August 2010 at six sampling sites, one located upstream and one downstream within each sub catchment. Significant differences in DOC concentrations were observed between the upstream non-drained catchment and the drained catchments, and there was considerable variation in the speciation of aquatic carbon (DOC, DIC, POC, CO2 and CH4) across the monitoring sites. Aquatic carbon fluxes were highest from the drained catchments and lowest from the non-drained catchments at 25.6 and 10.4 g C m−2 yr−1, respectively, with variability between the upstream and downstream sites within each catchment very low. It is clear from both the aquatic carbon concentration and flux data that drainage has had a profound impact on the hydrological and biogeochemical functioning of the peatland. In the restoration catchment, carbon export varied considerably, from 23.3 g C m−2 yr−1 at the upper site to 11.4 g C m−2 yr−1 at the lower site, largely due to differences in runoff generation. As a result of this hydrological variability it is difficult to make definitive conclusions about the impact of restoration on carbon fluxes and further monitoring is needed to corroborate the longer term effects.

Highlights

The ability of peatlands to store and sequester carbon is of major importance both nationally in terms of greenhouse gas (GHG) accounting, and globally in understanding the carbon cycle and potential changes to atmospheric composition
This study provides the first assessment of concentrations of all waterborne carbon species
CH4) in small headwater catchments located in the Flow Country and will provide a reference point for future comparisons of these systems, as they respond over the long-term to management

Summary

Introduction

The ability of peatlands to store and sequester carbon is of major importance both nationally in terms of greenhouse gas (GHG) accounting, and globally in understanding the carbon cycle and potential changes to atmospheric composition. Loss of carbon via the aquatic pathway constitutes a significant term within peatland carbon budgets, in some past studies accounting for between 34% and 51% of uptake from net ecosystem exchange (NEE) (Dinsmore et al, 2010; Nilsson et al, 2008; Roulet et al, 2007). Whilst there is considerable inter-annual variability evident in many of the carbon flux pathways from peatlands (e.g. Dinsmore et al, 2013; Helfter et al, 2015), a significant increasing trend in DOC concentrations has been detected in the majority of monitored surface waters in Europe and North America since the 1980s (Monteith et al, 2007). On the regional scale this trend has largely been attributed to recovery of soils from acid deposition (Evans et al, 2012; Monteith et al, 2007), on the catchment scale, anthropogenic disturbance of peatlands has been identified as a potential contributing factor to the observed DOC increases (Billett et al, 2010; Parry et al, 2014)

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