Competition for light and nitrogen among grassland species: a simulation analysis

1. A plant competition model to analyse the competition among perennial gra ssland species was developed. It was used to find out whether complex peren nial competition processes could be simulated accurately on the basis of ec ophysiological principles; what crucial parameters and processes determine succession; and how spatial heterogeneity affects interspecies competition for light and nitrogen. 2. Simulation results were compared with results of a 2-year replacement ex periment involving Holcus lanatus, Anthoxanthum odoratum and Festuca ovina. Sensitivity analyses were performed to evaluate the importance of processe s and parameters. 3. The model's sensitivity to plant height, specific leaf area and turnover and the large interspecific differences indicated that these were key dete rminants of competition between species. Festuca's low shoot turnover enabl ed it to survive the winter better and gave it an advantage in spring; this resulted in an unexpected recovery after winter in the second year. 4. Spatially explicit simulations showed that species patchiness reduced co mpetitive asymmetry, especially under nutrient-poor conditions. 5. The model's ability to simulate complex perennial competition processes as observed in the experiment indicates its potential for analysing vegetat ion processes related to succession.