Research topics are focusing on vegetation ecology, vegetation dynamics and vegetation management. My special interest concerns the functioning of plant communities with regard to changes in the landscape and environment, by looking at assembly rules and plant traits. For a better understanding of the ecology and functioning of plant communities, new perspectives have been opened by the rapid developments in computer techniques and the availability of large datasets.
Among his key publications are the National Vegetation Classification of the Netherlands (De Vegetatie van Nederland, five volumes) and several theoretical contributions on phytosociology, landscape ecology and nature conservation. Furthermore, he is co-author of various other books, among which the series Atlases of Plant Communities in The Netherlands and The Diversity of European Vegetation.