Heathland vegetation as a bio-monitor for nitrogen deposition and source attribution using delta N-15 values

The %N and delta N-15 signals in foliar nitrogen (N) from four heathland species have been monitored in a blanket bog plant community subjected to different experimental inputs of wet and dry N deposition. Interactions with combined additional treatments of phosphorus (P) and potassium (K) were also investigated. Calluna vulgaris, Cladonia portentosa, Sphagnum capillifolium and Hypnum cupressiforme were harvested for N-15 analysis prior to wet and dry treatment applications and again after 16 months field exposure. A significant increase was observed in both %N and delta N-15 values for all plant species in response to both wet and dry treatments whilst PK additions also produced significant decreases in foliar %N and associated delta N-15 values for several of the species sampled. These enrichments in the delta N-15 signals for posttreatment shoot tissue were attributable to the delta N-15 signal in the source application, a finding of potential value in using bio-monitors for assessment of N deposition. (c) 2005 Elsevier Ltd. All rights reserved.