Sphagnum farming: the promised land for peat bog species?

Sphagnum farming is a promising approach towards sustainability in growing media production for horticulture. In this study we focus on the additional value of Sphagnum farming sites as a surrogate habitat for threatened peat bog fauna. The highly diverse arthropod groups of spiders and harvestmen were used as bioindicators to track changes in species assemblages over the first 3 years of Sphagnum farming on a site in northwestern Germany. The results were compared with simultaneously studied reference habitats of nearby bog grasslands and degraded peat bog remnants. Spider communities changed rapidly from assemblages dominated by disturbance specialists (pioneer species) in the year of artificial Sphagnum establishment to diverse assemblages with large proportions of peatland generalists in the following years. Conservation value based on rarity, Red List status, disturbance tolerance and peatland association of individual species was in the later stage of Sphagnum farming as high as in the seminatural reference sites. Species quality index as derived from rarity scores was particularly high in the first year of succession due to the occurrence of some rare disturbance specialists. Despite the fact that each succession stage has its own conservation value, we advocate long rotation cycles in Sphagnum farming to allow establishment of slowly colonizing peatland specialists. We generally recommend the establishment of Sphagnum farms on degraded peatland, as creation of this artificial habitat promotes landscape and species diversity and provides refuges for endangered species of peatland and ephemeral habitats.