Restoration of lowland raised bogs damaged by peat extraction : with particular emphasis on Sphagnum regeneration
1. Revegetation trends in abandoned peat workings indicate that peat cuttings are generally too dry for spontaneous re-establishment of raised bog vegetation. The latter was restricted to small flooded peat pits which had recolonised 'hydroserally' to support floating rafts of bog vegetation. 2. The water storage capacity of cut-over bog surfaces is low compared with undisturbed bog and blocking drains in a peat field at Thorne Moors, S. Yorks, was insufficient to prevent water-table instability. Experiments suggest this may severely inhibit Sphagnum growth. Lagoons may increase water storage on a bog surface and facilitate development of raised bog vegetation as floating rafts. This 'hydroseral' approach may be necessary to restore raised bog vegetation to some areas. 3. Hydrochemical conditions of cut-over sites may differ significantly from undisturbed bogs with implications for Sphagnum growth. Water samples from a peat field at Thorne Moors were comparatively acidic and contained comparatively high concentrations of most major ions (particularly NH4 and SO4), except phosphorus. Moderate nutrient enrichment is unlikely to adversely affect Sphagnum and additions of phosphorus to flooded peat pits significantly increased its growth. In solution culture, low pH (3.0-3.5) was sub-optimal for Sphagnum growth, but the use of CaCO3 to reduce acidity in the field had a toxic effect. 4. Sphagnum recolonisation may be limited by availability of propagules in cut-over areas. Experiments indicate that deliberate re-introduction encourages Sphagnum raft development, which is pioneered by aquatic species that regenerate more prolifically from fragments than intact gametophytes. Sphagnum rafts are encouraged in shallow water (< 5 0cm) and pools of small area. Numerous management options exist physically and chemically assisting raft development.