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Effects of dry and wet N deposition on vegetation and biogeochemistry of an ombrotrophic bog

By Elleke van Zetten, Irene de Lange, Lucy J. Sheppard, Ian D. Leith, Alan Crossley, Leon van den Berg and Jan Roelofs

Abstract

It has repeatedly been shown that increased nitrogen (N) deposition results in dramatic\ud shifts in vegetation composition. The sources of N-deposition vary from agriculture\ud (mainly NH3 and NH4) to industry and traffic (mainly NOx).\ud Effects of these different N forms on the vegetation and biogeochemistry of an\ud ombrotrophic peat bog, Whim Moss (~15km southwest of Edinburgh), have been\ud investigated since April 2002, by employing an automate N manipulation system. This\ud field experiment, uniquely, offers the possibility to investigate the effects of the different N\ud forms at the same site and at application rates and deposition scenarios simulating\ud natural variation in rainfall. Within the manipulation system there are two N manipulations:\ud Dry, where gaseous NH3 is released over a 60 m transect at concentrations that simulate\ud a 100,000 bird poultry unit (0.4-200 μg m-3), and Wet, as soluble nitrate or ammonium,\ud covering the full range of UK wet N-deposition (8 – 64 kg N ha-1yr-1).\ud The effects of dry N deposition on the vegetation and biogeochemistry at different\ud distances from the NH3 source have been analysed. In the wet N deposition experiment, 5\ud treatments were followed, ranging from 8-64 kg N ha-1yr-1 and differing in N form as either\ud oxidised or reduced N.\ud Samples of soil water were obtained using mini-rhizon samplers and were tested for pH,\ud NH4, NO3, P and base cations. Young (1 year old) shoots of Calluna vulgaris L. (Hull),\ud Erica tetralix L. and Sphagnum capillifolium Ehrh. (Hedw.) were harvested and tested for\ud chlorophyll concentrations, aminoacids and P and base cation concentrations in acid\ud digests.\ud The preliminary results show differences between treatment N forms and N doses and\ud along the NH3 gradient. In this presentation we will focus on the plant responses to the\ud changes in the biochemistry.\ud CAPER Conferenc

Topics: Atmospheric Sciences
Publisher: Centre for Ecology and Hydrology
Year: 2006
OAI identifier: oai:nora.nerc.ac.uk:8327

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