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Differential effects of oxidised and reduced nitrogen on vegetation and soil chemistry of species-rich acidic grasslands

Research output: Contribution to journalJournal article

Published

  • Edu Dorland
  • Carly J. Stevens
  • Cassandre Gaudnik
  • Emmanuel Corcket
  • Suzanne Rotthier
  • Katherine Wotherspoon
  • Mari Jokerud
  • Vigdis Vandvik
  • Merel B. Soons
  • Mariet M. Hefting
  • Per Arild Aarrestad
  • Didier Alard
  • Martin Diekmann
  • Cecilia Duprè
  • Nancy B. Dise
  • David J. G. Gowing
  • Roland Bobbink
Article number1664
Journal publication date09/2013
JournalWater, Air, and Soil Pollution
Journal number9
Volume224
Original languageEnglish

Abstract

Emissions and deposition of ammonia and nitrogen oxides have strongly increased since the 1950s. This has led to significant changes in the nitrogen (N) cycle, vegetation composition and plant diversity in many ecosystems of high conservation value in Europe. As a consequence of different regional pollution levels and of the increased importance of reduced N in the near future, determining the effect of different forms of N is an important task for understanding the consequences of atmospheric N inputs. We have initiated three replicated N addition experiments in species-rich, acidic grasslands spanning a climatic gradient in the Atlantic biogeographic region of Europe in Norway, Wales and France at sites with low levels of pollution. N was added in two doses (0 and 70 kg N ha−1 year−1 above background) and in three forms (oxidised N, reduced N and a 50–50 combination). After 2.5 years of N additions, the effects of these treatments on plant biomass, plant nutritional status, soil pH and soil nutrient availability were determined. Impacts of the N additions were observed within the 2.5-year research period. In some cases, the first signs of differential effects of N form could also be demonstrated. In the French site, for example, grass biomass was significantly increased by the oxidised N treatments but decreased by the reduced N treatments. In the Norwegian site, the reduced N treatments significantly reduced soil pH, whereas oxidised N did not. Effects on nutrient availability were also observed. These experiments will be continued to elucidate the longer term impacts of N deposition on these grasslands.