I am a plant ecologist who investigates the response of plants and plant communities to environmental changes and their possible evolutionary consequences. My research deals with profound floristic changes during periods of mass extinction, deglaciation and global warming which can be of a catastrophic, step-wise or gradual nature. In order to understand what is happening on different temporal and spatial scales, the work strongly relies on a combination of palynology and paleobotany
Since the mid-nineties, I have studied several aspects of the end-Permian biotic crisis, ranging from ultrastructure of spore walls to paleoecology or extinction dynamics. In this interdisciplinary enterprise palynology, paleobotany, paleontology, stratigraphy, and biogeochemistry were used to obtain a high-resolution view of the sequence of events during ecosystem collapse and subsequent recovery. Currently, I am involved in a research project on the end-Permian crisis in South-Africa
At present, I am working on the taxonomy and phylogeny of more derived Late Paleozoic conifers and their communities, and the impact of prolonged climate change on their evolution. This work is based on very well preserved fossils of exceptional floras from Early Permian Texas. Other research lines include testing climate-controlled endemism of vertebrates in equatorial Pangea (with Chris Sidor and Neil Tabor). Since 2002, I have been a member of the Paleobiology Database Paleobotany Working Group. This is a team of paleobotanists working on data of fossil plant assemblages, stored in the web-accessible Paleobiology Database. The entered data allows us to better quantify changes in diversity and composition of floras throughout the history of life on land.