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(49-09) Predicting long-term effects of eutrophication and desiccation in undisturbed ecosystems. van Wijnen, Harm*,1, Mulder, Christian1, Bakker, Jan2, 1 RIVM-National Institute for Public Health and the Environment, Bilthoven, The Netherlands2 RUG - Lab. of Plant Ecology, Haren, The Netherlands ABSTRACT- Atmospheric nitrogen deposition in the Netherlands is one of the highest in Europe. It causes an increased accumulation rate of nitrogen in terrestrial ecosystems. As a result, the number of plant species generally decreases, and a few productive plants become dominant. This affects even other trophic levels, like herbivores (bottom-up) and mycoflora (top-down). The high-productive plants are generally less palatable for small herbivores, which causes the disappearance of these animals. Primary producers, like fungi, change both in composition and biomass. These processes have strong effects on the ecosystem. Two case studies in the Netherlands are presented, where effects of eutrophication and desiccation are analysed. The firstcase describes effects on soil processes, plants and herbivores at a coastal mire on the Wadden-island of Schiermonnikoog. A dynamic model was developed to predict long-term nitrogen compartmentation and flow through the investigated salt-marsh system. This model was parameterised using field data from sites, up to more than hundred years old. The second case describes mycoflora fluctuations along a minerotrophic gradient at an inland fen in Dwingeloo. Again, an environmental response model has been developed, this time focusing on the fungal diversity across the investigated mire. The latter model shows a high sensitivity of the mycoflora to water chemistry. Both models were used to predict long term ecosystem changes at several rates of eutrophication. The effects were assessed on three trophic levels. Key words: eutrophication, desiccation, model, ecosystem |
