Methods for restoring restiad raised bogs in North Island, New Zealand

Restoration of restiad bogs dominated by Sporadanthus ferrugineus and Empodisma minus (family Restionaceae) in New Zealand is a priority because they are highly threatened ecosystems. Experimental trials at a cut-over bog showed vegetation recovery was most successful when it emulated the major phases of restiad bog development (accelerated succession). Treatments included water table, peat cultivation techniques, nutrients and seed additions. The best results were achieved with raised ‘islands’ of milled peat seeded with early successional heath shrubs, which reached 100% vegetation cover in 2 years. Research has now extended to restoring the ecosystem at two sites on the margins of former extensive raised bogs. The sites have relatively high nutrient levels probably because they are minerotrophic wetlands and influenced by adjoining agricultural practices. Two experimental trials were established in September 2006. They involved combinations of substrate (milled peat, control), 2 year old plants (Sporadanthus, with and without Empodisma, control), and a weed/non weed management regime. After 5 months and an unusually wet summer season, plants in all treatments were growing well, with new basal shoots up to 30 cm for Sporadanthus and 25 cm for Empodisma. Restoration success is being evaluated using the New Zealand wetland condition index, based on 5 indicators known to degrade wetland condition (changes in hydrology, physicochemistry, intactness, animal impacts and plant cover). The sites currently score 8 and 10 out of 25 and the 10-year aim is 16 and 17 respectively, i.e., a significant increase in wetland condition.