Carbon Fluxes of Contrasting Degraded Peatland Pilot Sites During Early-stage Restoration: Ex-milled Bare Peat and Grazed Grassland Conversion.

The recovery of degraded peatlands can make significant contributions to reducing greenhouse gas emissions and climate warming. This study examines restoration techniques on shallow ex-milled peatland and intensively grazed pasture on deeper peat, both subject to prior drainage. Carbon greenhouse gases (GHGs) were monitored for 3 years following restoration treatment. After drainage-blocking measures, the ex-milled peatland was 'companion planted' with Eriophorum species and Sphagnum. The carbon balance was highly dependent on plant age and condition, with a high CO2 equivalent (CO2e) uptake when plants were vigorously growing (year 1: -22.4 ± 32.9 t CO2e ha-1 yr-1), and high emission when plants were mature and in various stages of senescence (year 2: 26.1 ± 26.4 and year 3: 16.4 ± 9.7 t CO2e ha-1 yr-1). Bare peat controls had a mean emission of 6.21 ± 1.68 t CO2e ha-1 yr-1 over the study period. At the other site, the grazed pasture was stripped, the bare surface planted with Sphagnum plugs, and irrigation was intensively managed via bunding, ditches, and automatic water pumping. Carbon GHG emissions were significantly reduced on this 'carbon farm' (2.77 ± 0.95 t CO2e ha-1 yr-1) compared to a neighbouring drained, grazed pasture control (31.7 ± 10.3 t CO2e ha-1 yr-1) over the study period (mean ± SD throughout). It appears clear that the cyclical nature of Eriophorum plant growth may only deliver carbon benefits on shallow peat over the long term if groundwater levels can be adequately supported and if climatic conditions are favourable. Conversion of grazed pasture to wetter farming crops, such as Sphagnum, can potentially deliver immediate carbon benefits, although, in this pilot, any potential loss of CO2e due to degraded topsoil removal, creation of bunds and irrigation ditches was not accounted for.