Differential effects of oxidised and reduced nitrogen on vegetation and soil chemistry of species-rich acidic grasslands
2013
Dorland, Edu | Stevens, Carly J. | Gaudnik, Cassandre | Corcket, Emmanuel | Rotthier, Suzanne | Wotherspoon, Katherine | Jokerud, Mari | Vandvik, Vigdis | Soons, Merel B. | Hefting, Mariet M. | Aarrestad, Per Arild | Alard, Didier | Diekmann, Martin | Dupre, Cecilia | Dise, Nancy B. | Gowing, David J. G. | Bobbink, Roland | Research Institute | Lancaster Environment Centre ; Lancaster University | Biodiversité, Gènes & Communautés (BioGeCo) ; Institut National de la Recherche Agronomique (INRA)-Université de Bordeaux (UB) | Nature Conservation and Plant Ecology Group ; Wageningen University and Research [Wageningen] (WUR) | Open University | University of Bergen (UiB) | Universiteit Utrecht / Utrecht University [Utrecht] | Norwegian Institute for Nature Research (NINA) | University of Bremen | School of Science and the Environment ; Manchester Metropolitan University (MMU) | Radboud University [Nijmegen]
International audience
Afficher plus [+] Moins [-]anglais. 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.
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