Impact of Simulated Nitrogen Pollution on Heathland Microfauna, Mesofauna and Plants. 2

S 11 Deposition of reactive nitrogen derived from intensive agriculture and industrial processes is a major 12 threat to biodiversity and ecosystem services around the world; however our knowledge of the impacts 13 of nitrogen is restricted to a very limited range of organisms. Here we examine the response of groups 14 of microfauna (testate amoebae), mesofauna (enchytraeid worms) and plants to ammonium nitrate 15 application in the Ruabon heathland long-term experiment. Plant data showed significant differences 16 between treatments, particularly characterised by a loss of bryophytes in nitrogen-treated plots, by 17 contrast enchytraeids showed a non-significant increase in abundance in response to treatment. Testate 18 amoebae showed no significant changes in abundance or inferred biomass but significant changes in 19 community structure with a reduced abundance of Corythion dubium, interpreted as a response to the 20 loss of bryophytes. Our results suggest that simple indices of plant community may have value for 21 bioindication while the bioindication value of testate amoebae and enchytraeids is not clearly 22