Bog surface oscillation (mire breathing): A useful measure in raised bog restoration

Oscillation of the peat surface is an important mechanism for hydrological self-regulation in bogs. As the water table rises in the wet season, the peat body expands, raising the bog surface and increasing water storage. With seasonal drying, the water table declines, the peat loses volume, and the bog surface drops, thereby keeping Sphagnum mosses in close contact with the water table. The oscillation of surface elevation in a Pacific coastal temperate raised bog was monitored at multiple sites for 4-12years in 8 different plant communities of both peat-harvested and unharvested sites to determine how bog surface oscillation relates to site conditions. The multiyear averages of bog surface oscillation for the different sites ranged from 2 to 34cm (mean: 10.8cm). In harvested sites, surface oscillation was linked to a larger water level amplitude and a shallower water table. In unharvested sites, a shallow water table was also a strong predictor of surface oscillation, but water level amplitude was negatively correlated to surface oscillation. This discrepancy was attributed to rewetting and regeneration of harvested sites, as well as historic drainage in many of the unharvested sites that reduced the elasticity of the peat. Surface oscillation differed significantly between some of the plant communities, generally between drier and wetter sites. In disturbed bogs, regeneration of a more elastic surface peat can increase the magnitude of peat volume change and bring about the return of self-regulating mechanisms. Bog surface oscillation may be an important metric for assessing the restoration success or storage capacity of raised bogs in similar climatic settings.