Effects of Ungulate Herbivores on Temperate Forest Understory Vegetation—Implications From a Large‐Scale Wildlife Exclosure Experiment in Central Europe

ABSTRACT Question Ungulates play a key role in influencing understory vegetation and ecosystem dynamics in temperate forests. However, how soil conditions modulate ungulate effects on understory communities remains insufficiently understood. Location Central and Southern Germany. Methods We used a time series of paired ungulate exclosures (fenced) and control plots (unfenced) to assess the influence of ungulates on the cover, species richness, and composition of forest understory communities at acidic and alkaline sites. We sampled epigeous bryophytes and vascular plants in 248 paired fenced and unfenced plots between 2016 and 2023, evaluating the data using multivariate analyses. Results We detected significant temporal changes in understory communities and differences between fenced and unfenced plots with distinct responses across vegetation layers and soil types. When ungulates were excluded by fencing, the herb layer initially showed increased cover, likely reflecting rapid release from herbivory that stimulated plant growth. Over time, however, herb layer cover declined, indicating that competitive interactions among plants became more important. In the shrub layer, both cover and species richness increased rapidly and significantly following fencing at both acidic and alkaline sites. In contrast, in unfenced plots, increases in shrub cover and species richness occurred more slowly and to a lesser extent over the same period. Species richness of the herb layer was not affected by fencing at alkaline sites, but declined at acidic sites. Cover but not species richness of the moss layer was higher in ungulate exclosures at both site categories beginning in the fourth year of observation. While no significant differences in understory species composition were detected between fenced and unfenced plots in any year, floristic differentiation over time occurred exclusively at acidic sites. Conclusions Ungulates influence forest understory communities differently under acidic and alkaline soil conditions, underscoring the importance of accounting for edaphic context in long‐term studies of ungulate–vegetation interactions. Our findings suggest that forest management can shape understory vegetation trajectories by incorporating ungulate impacts, particularly at acidic sites.