Do wolves increase temperate forest tree diversity?

Large carnivores, such as wolves, can indirectly influence vegetation by preying on herbivores and releasing plants from herbivory. This predation may trigger a cascading effect that alters vegetation structure, ecosystem functioning, and ultimately, biodiversity. While much research on carnivore-induced trophic cascades has focused on individual prey or tree species, the consequences for entire woody plant communities remain to be explored. Recent advances have highlighted the importance of using a plant functional traits framework to understand how herbivory shapes woody plant communities. This approach shifts the focus from individual plant species to the morphological and physiological traits that determine how woody species cope with herbivory. Despite these insights, the cascading effects of large carnivores on woody species trait diversity remain largely unexplored in temperate Europe, in addition to the effects of resource availability (e.g. water, light) and climate (e.g. seasonality). This project aims to fill this gap by investigating if and how predation by a large carnivore, the wolf, by seasonally affecting the ungulate prey community may affect the diversity and distribution of woody plants and their traits in Białowieża Forest. We hypothesize that wolves shape the seasonal foraging behavior of their ungulate prey, leading to cascading effects on the composition and functional trait diversity of regenerating tree communities.

The study addresses four questions:

1. How does wolf space-use pattern affect spatial patterns of ungulate browsing, and how does it differ between seasons?
2. What is the ungulate browsing intensity and diet in relation to patterns of wolf space-use and how does it differ between seasons?
3. What are the predominant plant trait syndromes in tree regeneration in relation to patterns of ungulate browsing?
4. To what extent does the distribution of trait syndromes in temperate woody-plant community vary with spatial patterns in ungulate browsing, and thus indirectly driven by wolf risk?

To answer these questions, we will use a combination of modern research techniques:

• Camera traps to monitor the distribution and behaviors of wolves and ungulates.
• DNA analysis of ungulate feaces to determine their diets.
• Field measurements of tree traits, such as height, leaf characteristics, and chemical composition.

We will collect data across different areas of the forest where wolf and ungulate activity is well-documented. We will also consider factors like soil quality, light availability, and the seasons, as these can influence both predator-prey interactions and tree growth.

Why is this important?

Traditionally, European forests have been viewed as being shaped mostly by rainfall, temperature, and soil conditions. However, recent research suggests that large predators and herbivores have always played a significant role in these ecosystems. Understanding these relationships can give us new insights into how forests work and how we can manage them effectively.

This research is especially relevant today for two reasons:

• Rising ungulate populations can lead to over-browsing, causing biodiversity loss and conflicts with agriculture and forestry.
• The return of large carnivores like wolves to many parts of Europe may help balance these ecosystems, but we need to understand how this works.

By studying Białowieża Forest, we hope to uncover the mechanisms behind species diversity in this unique ecosystem. These findings will not only help us protect Białowieża but will also provide lessons for managing other temperate forests across Europe and beyond.

Our work will ultimately help people understand the critical roles that wolves and other large mammals play in keeping forests diverse. This knowledge can guide conservation efforts and help balance the needs of wildlife, forests, and human activities.