Carbon budgets of two contrasting degraded peatland sites following 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 contrasts 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. The ex-milled peatland was ‘companion planted’ with Eriophorum species and Sphagnum , after drainage-blocking measures. The carbon balance was highly dependent on plant age and condition, with a high CO ₂ e uptake when plants were vigorously growing (year 1: -22.4 t CO _2e ha ^− 1 yr ^− 1 ), and high emission when plants were mature and in various stages of senescence (year 2: 26.1 and year 3: 16.4 t CO _2e ha ^− 1 yr ^− 1 ). Bare peat controls had a mean emission of 6.21 ± 1.68 t CO _2e 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 CO _2e ha ^− 1 yr ^− 1 ) compared to a neighboring grazed pasture control (31.7 ± 10.3 t CO _2e ha ^− 1 yr ^− 1 ) (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. Conversion of grazed pasture to wetter farming crops, such as Sphagnum , is likely to deliver immediate carbon benefits.