During his PhD studies, Jonas Trepel investigated how large herbivores shape vegetation structure and plant diversity under accelerating global change. Using remote-sensing analyses, he examined changes in vegetation structure across southern Africa and found that increases in woody plants are widespread and strongly linked to atmospheric nitrogen deposition, while large herbivores at high densities can modestly slow increases in woody cover. Moreover, using observational and experimental field studies, he tested the effect of large herbivores on plant diversity and found that - across ten savanna reserves and six long-term exclosures - herbivores consistently increased plant species richness, especially for herbaceous species.

These findings improve our understanding of large herbivores as ecosystem engineers and highlight their importance for biodiversity conservation and restoration strategies in a rapidly changing world

The PhD study was completed at the Center for Ecological Dynamics in a Novel Biosphere (ECONOVO), Section for Ecoinformatics and Biodiversity, Department of Biology, Faculty of Natural Sciences, Aarhus University.

This summary was prepared by the PhD student.

Time: Friday, 20 March 2026 at 9:00 a.m.
Place: Building 1532, Auditorium G1, Aarhus University, Ny Munkegade 118 , 8000 Aarhus C. 
It will be possible to view the exam online. To receive a link please contact: jonas.trepel@bio.au.dk
Title of PhD thesis: Ecological Dynamics in a Novel Biosphere: Large Herbivores as Drivers of Vegetation Structure and Plant Diversity
Contact information: Jonas Trepel, e-mail: jonas.trepel@bio.au.dk, tel.: +45 4271 6115
Members of the assessment committee:

• Professor Sally Archibald, School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, South Africa
• Professor Anu Eskelinen, Global Change and Biotic Interactions Ecology, University of Oulu, Finland
• Associate Professor Alejandro Ordonez (chair), Department of Biology, Aarhus University, Denmark

Main supervisor:
Associate Professor Robert Buitenwerf, Department of Biology, Aarhus University, Denmark
Co-supervisors:
Associate Professor Elizabeth le Roux,  Department of Biology, Aarhus University, Denmark
Professor Jens-Christian Svenning, Department of Biology, Aarhus University, Denmark
Language: The PhD dissertation will be defended in English

The defense is public.
The PhD thesis is available for reading at the Graduate School of Natural Sciences/GSNS, Ny Munkegade 120, building 1521, 8000 Aarhus C