Carbon dioxide dynamics of a restored maritime peatland

Abstract

The restoration of cutaway peatlands provides an opportunity to return the carbon (C) sink function and to examine the influence of climate on peat formation and C accumulation. We studied CO2 exchange dynamics in 2002 and 2003 at a rewetted cutaway peatland located within the temperate maritime climatic zone. Gross photosynthesis (PG), ecosystem respiration (RTOT), and net ecosystem exchange (NEE) were observed in a range of microsites representing a hydroseral succession gradient: Typha latifolia—Phalaris arundinacea, Eriophorum angustifolium—Carex rostrata, and Juncus effusus—Holcus lanatus vegetation communities and areas of bare (unvegetated) peat. Annual rainfall was 26% higher in 2002 and 4% lower in 2003 than the long-term average and influenced water table position at all microsites. Observed instantaneous CO2 fluxes varied temporally and spatially at all microsites. Modelled PG was strongly dependent on irradiation (Photosynthetically Active Radiation) and the Vascular Green Area index (VGA). RTOT was influenced by the soil temperature at 5 cm depth (T5cm) and the water table position. All microsites were net sources of CO2 in both years of the study, and higher losses (with the exception of Juncus/Holcus) were observed in 2003 at all microsites. In general, losses followed the trend Juncus/Holcus > Phalaris > Typha > bare peat > Eriophorum—Carex in 2002 and Phalaris > Juncus—Holcus > Typha > Eriophorum/Carex > bare peat in 2003. Losses ranged from -163 to -651 g CO2 - C·m−2.y−1 in 2002 and -308 to -760 g CO2 - C·m−2.y−1 in 2003. Considerable wintertime losses were observed at all microsites. The results from this study suggest that these peatlands are vulnerable to interannual variations in climatic inputs and that future predictions of climatic change may make restoration of the C sink function in cutaway peatlands in the temperate maritime climatic zone a considerable challenge in the years ahead.