Carbon stability in a Scottish lowland raised bog: potential legacy effects of historical land use and implications for global change

Abstract

Peatlands comprise major global stocks of soil organic carbon (SOC). Many degraded peatlands are currently being restored, but little is known to which degree former disturbances leave a ‘legacy’ in such restored peatlands, and subsequently how this impacts their response to global change. Our aims were to investigate if after 20 years of restoration (i) carbon stability may still be affected by the former land use and if (ii) restored bogs are less susceptible to nutrient input but (iii) more sensitive to temperature rise. We sampled the top- and subsoil of a formerly drained, a previously drained and afforested part and an unmanaged control site of a Scottish bog. We incubated peat from each part for determination of potential basal respiration, nutrient limitation and temperature sensitivity (Q10) of aerobic peat degradation. Lowest respiration rates were identified at the afforested site while nutrient addition had no significant effect on topsoil organic matter decomposition at all sites. Q10 values were significantly higher in the topsoil (2.6 ± 0.3 to 2.8 ± 0.2) than in the subsoil. For the subsoil, the drained site (2.0 ± 0.0) showed significantly lower Q10 values than the afforested one (2.6 ± 0.6), while the control site had a Q10 of 2.1 ± 0.0, indicating contrasting temperature sensitivities of potential SOC losses following specific forms of disturbance. Overall, our data indicate that afforestation left a legacy on potential subsoil SOC losses with global warming. Such effects must be considered when integrating restored bogs into global data bases on peatlands' responses to global change.