Role of recent climate change on carbon sequestration in peatland systems

This paper provides information on the impact of recent climate change on carbon sequestration in peatland systems in South West England. This is important because peatlands have the potential to sequester and hold large quantities of anthropogenically released CO_2. This paper investigates whether there has been a reduction in the strength of carbon sinks in a valley mire and blanket bog, which occur on the limits of the biogeographical envelop for peatlands in Britain. Past rates of carbon accumulation were calculated from peat depth and the sequential analysis of peat age, bulk density and carbon content from cores taken from valley mire and blanket bog. At the valley mire site contemporary net ecosystem carbon balance (NECB) was calculated by measuring inputs to the peat body, via net primary productivity (NPP), of Sphagna. Losses of C from the peat body were calculated by measuring CH₄, and aquatic carbon, calculated from catchment export of particulate and dissolved organic carbon. The study found similar mean rates of carbon accumulation since 1850 of 11.26 t ± 0.68 t CO₂e ha^-1 yr^-1 (307 g C m^-2 yr^-1) in valley mire and 11.77 t ± 0.88 t CO₂e ha^-1 yr^-1 (321 g C m^-2 yr^-1) in blanket bog. The mean present-day CO₂ sequestration rate for Sphagna on valley mire was calculated to be 9.13 t ± 0.98 t CO₂e ha^-1 yr^-1 (249 g C m^-2 yr^-1). Both past and contemporary rates of CO₂ sequestration were found to be at the maxima of those reported for temperate peatlands. NPP was found to vary according to microform with higher rates of carbon sequestration found in lawn and hummock microforms compared with pools. Our work suggests that recent changes in the climate appear to have had limited impact on the strength of peatland carbon sinks in South West England.