Large herbivores trigger spatiotemporal changes in forest plant diversity.

Area of Science:

• Ecology
• Forestry
• Wildlife Management

Background:

• Large herbivores influence plant communities, but their impacts in disturbed temperate and boreal forests are complex and debated.
• Understanding herbivore effects is crucial, especially where disturbances like logging interact with grazing pressure.

Purpose of the Study:

• To assess the influence of high white-tailed deer density on plant diversity, composition, and succession in logged boreal forests.
• To differentiate between direct filtering and indirect suppression of dominant plants by deer herbivory.
• To investigate the scale dependency of deer impacts on plant communities across space and time.

Main Methods:

• A long-term, replicated landscape experiment with high deer density in recently logged boreal forests.
• Analysis of spatiotemporal dynamics of understorey plant assemblages, including diversity and composition.
• Evaluation of impacts on different vegetation layers (tree vs. non-tree) and at various spatial scales.

Main Results:

• Deer significantly altered plant community composition and successional trajectories.
• Impacts on plant alpha and beta diversity were strongly dependent on spatial and temporal scales.
• Deer acted as both a direct filter and a suppressor of dominant species, with asymmetric effects on tree and non-tree layers.
• While supporting an ungulate-driven homogenization hypothesis, compositional shifts did not reliably predict beta diversity loss.

Conclusions:

• Long-term studies are essential for understanding nonlinear community dynamics influenced by herbivores.
• Deer herbivory has complex, scale-dependent effects on boreal forest plant communities.
• Management strategies must consider specific community properties and scales of interest due to contrasting diversity trends.