Forest Biology Center

New paper in Ecology shows that reproductive performance of Wood Warblers – small, ground-nesting songbirds – is much lower in years following mast seeding than in years preceded by mast failures, as mast seeding indirectly increases predation pressure on Wood Warbler nests. Moreover, matrix population models revealed that regional variation in mast seeding frequency is a possible explanation for divergent population trends of Wood Warblers in different regions of Europe. The paper can be found here: https://doi.org/10.1002/ecy.4227

New paper in Nature Communications takes 517 plant species and links their interannual variation of seed production with functional traits. While interannual variation in seed production is highest in temperate and boreal zones, our analysis controlling for environment and phylogeny indicates that masting is more frequent in species that invest in tissue longevity.

There is a write-up on that paper in the Nature blog, and the paper is here.

Phenology, corresponding to the study of periodic events, plays an important role in fitness and species distribution because it determines when a species grows and reproduces. Here, F. Jean et al. compiled a dataset of leaf phenology observations for European Beech and Silver fir. The data has been recorded at the tree level, from bud development to leaf unfolding date, along the Mont-Ventoux, a mountain in the South of France. 

A new paper in Methods and Ecology Evolution rediscovers CVk, a CV-based metric that has some interesting features making it worth looking at in masting studies. These include the reduced sample size needed to discover trends, especially worthy one given the logistical challenges of long-term seed production monitoring and the scarcity of such data.

In June 2023, the Forest Biology Center organized a conference at Gułtowy Palace (near Poznań).
We had a great time discussing science, exchanging ideas, planning papers, and networking.
Now, we are in the process of writing a perspective paper that will gather the work we accomplished during the meeting. Stay tuned!

Last month our lab member, Kasia Kondrat defended her master’s thesis on Drivers of intraspecific variation in fecundity in rowan. This study investigated the factors influencing fecundity using a 22-year fruit-count dataset from 167 individual trees. Findings highlighted diameter at breast height (DBH) as the best size proxy for standardizing fecundity, and light availability played a major role in rowan’s fecundity. Congratulations Kasia!

Masting not only enhances plant reproductive efficiency and fitness but also influences entire food webs. However, quantifying the year-to-year variability in masting has been a subject of intense debate. The commonly used coefficient of variation falls short in accounting for the serial dependence and the presence of zeros in individual-level datasets, limiting its suitability for phenotypic selection, heritability, and climate change studies. To overcome these limitations, our three case studies introduce volatility and periodicity as novel metrics that capture both high and low-frequency variance, even in the presence of zeros. By examining multiple plant species, including Sorbus aucuparia, Pinus pinea, Quercus robur, Quercus pubescens, and Fagus sylvatica, we demonstrate how these new metrics greatly enhance ecological interpretations and pave the way for significant advancements in the analysis of long-term, individual-plant datasets.

Understanding the timing of masting is crucial for successful management and conservation efforts in ecosystems dominated by masting species. That’s why understanding the mechanisms behind masting and developing forecasting tools for seed production is urgently needed. In our recent New Phytologist paper we evaluated the predictive capabilities of three models—foreMast, ΔT, and a sequential model—in forecasting seed production in trees. By utilizing a comprehensive pan-European dataset of Fagus sylvatica seed production, we tested these model’s abilities to recreate past seed production dynamics, and identified dimensions that work well and gaps. One key finding from our study is the influence of high-quality data on prior seed production on the model’s predictive power. Incorporating good-quality data enhances models’ predictive power. This underscores the importance of implementing effective methods to monitor seed production, as they may serve as the foundation for developing accurate forecasting tools. While our models exhibit moderate success in predicting seed production dynamics, they are better at forecasting crop failures rather than bumper crops. The factors that reduce seed production are better understood compared to those responsible for large reproductive events. We acknowledge these challenges and present a roadmap to drive the discipline forward and encourage further advancements in mast forecasting.

Climate change continues to reshape our natural ecosystems, and its impact on tree populations is a topic of great concern. Our recent study investigating the response of European beech (Fagus sylvatica) to climate warming has uncovered intriguing insights into the complex relationship between tree reproduction, climate change, and forest dynamics.

The Masting Breakdown Phenomenon: One significant consequence of climate warming is the disruption of masting, the periodic synchronous production of large seed crops by trees. Masting breakdown occurs when warming reduces the synchrony and interannual variability of seed production, leading to a decline in viable seed production over time.

The Role of Tree Size: Our study further reveals that tree size plays a crucial role in mediating the effects of masting breakdown. While smaller trees experience increased seed predation over time, larger individuals suffer a disproportionate decrease in pollination efficiency. As a result, the ability of trees to produce viable seeds, declines across all size classes, with the greatest impact observed in large trees. This reversal of the correlation between tree size and viable seed production represents a potential for a significant shift in the dynamics of forest regeneration.

Implications for Forest Dynamics: The implications of these findings extend beyond individual trees to broader forest dynamics. The decline in viable seed production has consequences for the stand- and biogeographical-level processes of forest regeneration. Forests may struggle to maintain their populations if the declining seed production trend continues, leading to decreased resilience and potential shifts in species composition.

Management Strategies for Forest Resilience: Understanding the relationship between tree reproduction and climate change allows us to explore management options that can enhance forest resilience in the face of a warming climate. The study suggests that focusing on strategies to mitigate seed predation in small trees and improve pollination efficiency in larger trees could help counteract the adverse effects of masting breakdown. Implementing targeted interventions to support reproduction across all size classes may be crucial for safeguarding forest viability and maintaining the diversity of our ecosystems.

Conclusion: As climate change progresses, it is imperative to deepen our understanding of how trees respond to these environmental shifts. Our study on European beech offers valuable insights into the complex interplay between climate warming, tree reproduction, and forest dynamics. By recognizing the impact of masting breakdown and the role of tree size, we can develop effective management strategies to promote forest resilience in a changing world. Protecting our forests is not only crucial for the survival of tree populations but also essential for maintaining the countless benefits they provide to our planet and society.