Atmospheric CO2 sequestration in restored mined peatlands

This study comparing the net ecosystem CO2 exchange in natural, restored, and naturally regenerated peatlands assesses the significance of peatland restoration as a global biotic offset under the Kyoto Protocol. Maximum gross photosynthesis (GPmax) at the restored peatland (-17.5 g CO2 m-2 d-1) was more than two times that at lawns in the natural peatland (-8.2 g CO2 m-2 d-1) and almost three times that of the naturally regenerated peatland (-6.5 g CO2 m-2 d-1). However, GPmax at hummock sites (-18.1 g CO2 m-2 d-1) in the natural peatland exceeded that of the restored peatland. Total rainfall during the study period was ~75% of the 30-year mean and these drier conditions resulted in all sites being a net source of atmospheric CO2 during the summer. From May 5 to August 23, 1998 respiration followed the trend: mined (398 g C m-2) > restored (169 g C m-2) > natural (138 g C m-2) peatland. While restoration did not return the net carbon sink function, it resulted in a significant decrease in the source of atmospheric CO2 (229 g C m-2) over the summer season. Approximately 70% of this decrease was due to the increase in gross ecosystem production, while the remaining 30% was due to a decrease in total respiration. The presence of Sphagnum mosses at the naturally regenerated peatland also resulted in a ~45% decrease in total respiration (soil and plants), indicating that an increase in volumetric soil moisture content during restoration has the potential to lower soil respiration at abandoned mined peatlands. Considering the area of drained and mined peatlands globally, peatland restoration on abandoned mined peatlands has the potential to represent an important biotic offset through enhanced carbon sequestration.