Deep-Time Perspectives on Vegetation Ecology: Skjold Søndergaard

The Ecosystems and Biodiversity Programme recently welcomed Skjold Søndergaard, a visiting doctoral student from Aarhus University, to the lab. Skjold’s research focuses on vegetation ecology across Europe, with particular attention to how long-term ecological processes can inform contemporary conservation and restoration. Last week, he presented his work to the Ecosystems Lab in a talk titled ‘Natural vegetation and its drivers: integrating deep-time baselines and multitrophic field evidence.’ Drawing on findings from Denmark and across temperate Europe, the presentation considered how assumptions about natural vegetation influence contemporary restoration approaches.

A central concept in Skjold’s research is biotic integrity, which refers to the degree to which an ecosystem’s species composition, structure, and ecological functioning resemble those of a minimally disturbed system. Biotic integrity is frequently used as a framework for assessing ecosystem condition and guiding restoration objectives. However, defining appropriate reference conditions remains challenging, as most contemporary ecological baselines reflect long histories of human land use. In practice, this creates challenges for researchers and practitioners as they work to establish reference conditions for rewilding and restoration efforts.

In a recent article, Skjold examines the role of megafauna in plant community ecology, a topic that has received limited attention to date. Large herbivores, now largely absent from European landscapes, historically influenced vegetation structure and dynamics through grazing, browsing, and disturbance. When these ecological interactions are not incorporated into analyses, restoration baselines may reflect only a subset of past ecosystem processes. Skjold suggests that definitions of landscape integrity could place greater emphasis on evolutionary and ecological indicators, rather than relying primarily on culturally derived reference states. He is currently working with the Danish government to explore how such indicators might be incorporated into restoration planning and policy.

Empirical findings presented in the talk indicate that many European ecosystems were characterised by semi-open mosaics of woodland and open habitats, rather than by continuous closed-canopy forest. These landscapes supported plant and animal communities associated with relatively light-rich conditions. This evidence contrasts with interpretations that assume dense forest cover as the dominant pre-disturbance state. The mosaic structure identified in this work suggests that open and shaded habitats often co-occurred and that vegetation dynamics operated across a continuum rather than within discrete categories.

Skjold arranged an expedition in 2025 to survey the most intact vegetation of temperate Europe. Here, he is sitting in an old-growth grassland in Transylvania.

This perspective has implications for how vegetation systems are conceptualised and studied. Rather than treating grasslands and forests as separate ecological domains, Skjold proposed considering them within a broader framework of vegetation ecology. Such an approach aligns with the diversity of research within the Ecosystems Lab, where work spans a range of biomes, including African savannahs, the Amazon rainforest, and Oxford’s Wytham Woods. While much of Skjold’s empirical research is based in Denmark, the ecological processes and policy considerations discussed are relevant to the UK context. During his time in Oxford, he aims to exchange ideas on plant community ecology, reforestation, and biodiversity with researchers both within the lab and across the wider Oxford community.

Understanding how large herbivores shape vegetation, especially in temperate forests and grasslands, is central to Skjold's research.