Contemporary carbon fluxes do not reflect the long-term carbon balance for an Atlantic blanket bog

Abstract

Peatlands are one of the largest terrestrial stores of carbon. Carbon exchange in peatlands is often assessed solely by measurement of contemporary fluxes; however, these fluxes frequently indicate a much stronger sink strength than that measured by the rate of C accumulation in the peat profile over longer timescales. Here we compare profile-based measurements of C accumulation with the published net ecosystem C balance for the largest peatland area in Britain, the Flow Country of northern Scotland. We estimate the long-term rate of C accumulation to be 15.4 g C m −2 yr −1 for a site where a recent eddy covariance study has suggested contemporary C uptake more than six times greater (99.37 g C m −2 yr −1 ). Our estimate is supported by two further long-term C accumulation records from nearby sites which give comparable results. We demonstrate that a strong contemporary C sink strength may not equate to a strong long-term sink and explore reasons for this disparity. We recommend that contemporary C sequestration should be viewed in the context of the long-term ecological drivers, such as fires, ecohydrological feedbacks and the changing quality of litter inputs.

Peatland carbon stocks and burn history: Blanket bog peat core evidence highlights charcoal impacts on peat physical properties and long‐term carbon storage

“…Indeed such discrepancies between flux and stock approaches in determining ecosystem C accumulation rates for peatlands have been highlighted previously by Ratcliffe et al. () and Clay et al. ().…”

“…However, the conclusions reached here are based on a C-stock inventory which could be different compared with using a C-flux approach. Indeed such discrepancies between flux and stock approaches in determining ecosystem C accumulation rates for peatlands have been highlighted previously by Ratcliffe et al (2017) and Clay et al (2010). The major disadvantages of the C-flux approach are that it does not capture long-term incorporation of C as charcoal (Clay et al, 2010), while capturing decomposition from deeper, older layers, which affects the C budget calculations of recent periods, due to the mixed age of the overall decomposition signal.…”

“…(), could explain the observed discrepancies in peatland C sequestration between flux and stock approaches as highlighted by Ratcliffe et al. (). Put simply, while burning causes considerable loss of above‐ground C during combustion, it also transforms otherwise decomposable biomass into charcoal, which is very recalcitrant to decomposition (Leifeld et al., ) and possibly also supresses microbial activity (Lu et al., ).…”

“…Particularly, the evidence in relation to rotational burning as part of grouse moor management is very weak and impacts are often unclear or contradictory (Harper et al, 2018). Moreover, the potential of charcoal to "lock away" C over time, as suggested by Clay et al (2010), could explain the observed discrepancies in peatland C sequestration between flux and stock approaches as highlighted by Ratcliffe et al (2017). Put simply, while burning causes considerable loss of above-ground C during combustion, it also transforms otherwise decomposable biomass into charcoal, which is very recalcitrant to decomposition (Leifeld et al, 2017) and possibly also supresses microbial activity (Lu et al, 2014).…”

Response to: Comment on “Peatland carbon stocks and burn history: Blanket bog peat core evidence highlights charcoal impacts on peat physical properties and long‐term carbon storage” by Evans et al. (Geo: Geography and Environment 2019; e00075)

“…We clearly noted in our paper that there is a known contradiction between peat core and flux derived C accumulation rate estimates (we did provide two references: Clay et al, 2010 andRatcliffe et al, 2017). We clearly noted in our paper that there is a known contradiction between peat core and flux derived C accumulation rate estimates (we did provide two references: Clay et al, 2010 andRatcliffe et al, 2017).…”