Abstract

The aim of this project was to analyse the effects of climatic change on plant species diversity and ecosystem functioning. The direct effects of climatic change on plant species diversity were analysed using a species-based probabilistic model (EUROMOVE) that relates the probability of occurrence of ca. 1400 European plant species to climatic variables like the mean temperature of the coldest month, the effective temperature sum, the annual precipitation, the annual potential and actual evapotranspiration, the length of the growing season and the mean growing season temperature. The indirect effects of raised CO2 levels and increased temperatures on ecosystem functioning, and the consequences of these indirect effects for plant diversity, were analysed by combining a mechanistic simulation model (NUCOM) with regression models. NUCOM predicts the effects of environmental changes on dominant plant species composition and ecosystem variables. The predicted ecosystem variables are linked to plant species diversity of subordinate species by regression models using Ellenberg indices for N availability, soil acidity, soil moisture and light intensity. The consequences of climatic change scenarios (IPCC Baseline A, IPCC Stabilisation 450) and N deposition scenarios (reduced, constant) were analysed using these two approaches for Europe (EUROMOVE) and part of the Netherlands (NUCOM). The results showed that the direct effects of climatic change may have a large impact on plant species diversity and distribution. The indirect effects of climatic change on plant diversity appeared minor but effects of changes in soil moisture are not included. Other environmental changes like eutrophication and human impact have a large effect on ecosystem variables and plant species diversity. Reductions in nitrogen emission have a positive effect but take time to become apparent.