Greater nitrogen and/or phosphorus availability in

Authors: Nanette J Madan Lewis J Deacon Clare H Robinson

Publish Date: 2006/10/12

Volume: 30, Issue: 5, Pages: 559-

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Abstract

Enhanced nitrogen N deposition at high latitudes is a circumpolar phenomenon Low soil phosphorus P however may limit vegetation responses to increased N inputs From 2000 to 2002 the effects of N at 0 05 a rate occurring in Greenland and Iceland and 5 equivalent to deposition in areas of Europe g N m−2 a−1 and P 01 g m−2 a−1 treatments on plant species’ cover and diversity were determined at a polar semidesert site ambient deposition c 01 g N m−2 a−1 in Svalbard 79°N The largest response was to combined 5 g N plus 1 g P m−2 a−1 where cover of Saxifraga oppositifolia increased c fourfold density of Salix polaris leaves c ninefold seedlings of several ‘new’ species Draba oxycarpa Saxifraga caespitosa Sagina nivalis were established and ‘immigration’ of Bryum arcticum and ‘extinction’ of Schistidium apocarpum were observed There were fewer less pronounced effects on the plant community at 05 g N m−2 a−1 Low P availability did indeed appear to restrict vegetation response to N There was a trend for plant species’ richness and diversity to increase with 1 g P m−2 a−1 at 0 and 05 g N m−2 a−1 but not at 5 g N m−2 Plant species showed individualistic responses so that generalisation by functional type was not possible Such increased colonisation by moss species of bare soil and greater densities of previously unrecorded angiosperm seedlings are not usually observed in more closed subarctic tundra as a response to N and P additions These changes are likely to influence significantly nutrient cycles whole system carbon budgets and surface energy and water balancesThis work was funded by the Global Atmospheric Nitrogen Enrichment thematic programme of the Natural Environment Research Council NERC We are grateful to Philip Saunders funded by an Undergraduate Bursary from the British Mycological Society and to Janie PryceMiller for help in the field It is a pleasure to thank NERC for the use of their Arctic Research Station in NyÅlesund Mr N I Cox for logistical support and Professor John F Farrar for help with the measurements of chlorophyll content We thank John Birks for identifying specimens of B arcticum and the kind comments of Peter D Moore and two anonymous reviewers improved earlier drafts of this manuscript

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