Has ammonia fumigation affected enchytraeid worms at Whim Moss

The Whim Moss experimental site was established in 2002, for the UK Natural Environment Research Council’s GANE programme (Global Atmospheric Nitrogen Enrichment). This site enables the study of in situ enhanced N effects (as NH3, NH4 + and NO3 - - N) on a sensitive semi-natural habitat, where N applications are dependent upon suitable meteorological conditions. 3 years (2002-2005) of NH3-N fumigation along a 60 m transect has resulted in an exponential decline in NH3-N concentrations from the NH3-N source to 60 m. On this transect, Calluna and sensitive moss species are now in decline. Below-ground effects were investigated in a short-term* study that focused on Enchytraeid worms (Oligochaeta): Enchytraeids are the dominant indicator species in wet acidic habitats, with key roles in biogeochemical cycling. Results showed that changes to the peat pH and mineral N correlated (p < 0.05) with the decline of NH3-N concentrations down the transect. It was expected that NH3-N fumigation would increase the N content of the litter layer, the main Enchytraeid food source; an improved litter quality would thus increase the Enchytraeid population on the transect. At Whim, 3 acidophilic Enchytraeid species were identified; however Enchytraeid species and total abundance were not affected by NH3-N concentrations, pH or mineral N. Both Enchytraeid abundance and litter N content were similar on the transect and ambient control. It is proposed that 3 years of ammonia fumigation at Whim is not yet long enough for plant matter with an increased N content to become incorporated into the litter layer. Future long-term monitoring, with more systematic sampling, will confirm any N effect on the Enchytraeids.