Early effects of atmospheric ammonia deposition on Calluna vulgaris (L.) hull growing on an ombrotrophic peat bog

This paper reports data from a field study investigating the impacts of elevated ammonia (NH₃) deposition on Calluna vulgaris growing on an ombrotrophic peat bog in S.E. Scotland. Shoot extension, foliar N concentrations, chlorophyll concentration and chlorophyll fluorescence were measured during the second growing season of exposure to a gradient of ammonia concentrations. Results indicate that NH₃ increases growth between 150–200 kg N ha^?1y^?1 cumulative deposition. Foliar N content increased significantly in response to NH₃ cumulative deposition up to 400 kg N ha^?1 y^?1 whereas chlorophyll a content significantly decreased. Measurements of Fv/Fm suggest that although NH₃ exposure altered the growth and reduced chlorophyll a, the efficiency of photosystem II was insensitive to NH₃–N deposition at this stage.