Forest Biology Center

How does drought affect tree reproduction? In our new study published in Proceedings of the National Academy of Sciences (PNAS), led by Jakub Szymkowiak, we show a surprising result: European beech continues to produce seeds even during severe drought.

We analysed 221 long-term time series of European beech reproduction across Europe, comprising 5,362 annual population-level observations. The analysis separated drought exposure during flowering and pollination in spring, seed maturation in summer, and potential effects carried over to reproduction in the following year.

After accounting for the temperature cues that trigger mast reproduction, we found that summer drought did not reduce seed production. Dry spring conditions were actually associated with higher seed output, likely because dry weather improves airborne pollen dispersal and pollination efficiency. We also found no evidence that summer drought suppressed reproduction in the following year.
We then focused on three exceptional European droughts: 2003, 2018, and 2022. Even at the sites experiencing the strongest water deficits, seed production was not lower than expected. Once beech trees are committed to reproduction, they appear to maintain seed production even under extreme short-term water stress.

This creates an important contrast in how trees respond to drought. The same drought events that suppress tree growth and increase mortality can leave reproductive output largely intact. Different components of tree demography can therefore respond very differently to the same climatic stress, with consequences for how we predict forest regeneration, turnover, and resilience under a warmer and drier climate.

The finding should not be interpreted as broad resilience of beech reproduction to climate change. Climate warming can disrupt masting dynamics, while drought may still affect seed viability, seedling establishment, and survival. Understanding how seed production connects to successful recruitment is therefore the next major challenge.

Read the full paper here!

How birds learn that specific sounds are cues of a threat, such as predator vocalizations or heterospecific alarm calls? A new study led by Jakub Szymkowiak and published in Behavioral Ecology and Sociobiology reveals that birds can learn to recognize novel, previously unfamiliar sounds (samples of punk rock songs) as acoustic risk cues socially, by associating them with conspecific alarm calls. Moreover, social learning is threat-sensitive, with naïve individuals acquiring anti-predator responses to novel sounds depending on the strength of the anti-predator responses of conspecifics to these sounds.

The study provides experimental evidence that even though during the breeding season individual birds occupy distinct territories that are spaced apart each other, they are still inter-connected via information sharing and, at the population level, form a kind of “information network”. In such networks, novel anti-predator responses can be socially acquired and transmitted among the individuals across territory borders. Under natural conditions, the threat-sensitive social transmission likely allows individuals to minimize the costs of incorrectly associating neutral sounds as cues of a threat when learning via indirect risk cues.

Such social transmission of risk recognition among territorial conspecifics can have important eco-evolutionary consequences. Traditionally, co-occurring conspecifics have been considered as putative competitors and the negative impacts of competitive interactions on individuals’ fitness and higher order ecological phenomena have been emphasized. However, the results of this study show that apart from being competitors, conspecifics are also the repositories of vital, fitness-enhancing information, which they can transfer to other individuals.

Read the full paper here: https://doi.org/10.1007/s00265-026-03751-3

Seeds start forest renewal, allowing forests to regenerate, expand and adapt to changing conditions. But our new study, published in Nature Climate Change, shows that climate change may be weakening tree fecundity in Europe’s trees.

We analysed 34 years of Polish forest seed-harvest records, covering 40,530 annual observations from 438 forest districts between 1988 and 2021. The dataset included five major forest-forming species: European beech, silver fir, Scots pine, pedunculate oak and sessile oak.

These long-term records are particularly valuable because they report sorted seed lots. In other words, they reflect seeds that pass quality control, with empty, damaged or infested seeds largely removed. This means the data provide insight into viable seed production, not just the total number of seeds produced.

The results were striking. Viable seed production declined across all studied taxa: by around 65% in oaks, 64% in Scots pine, 44% in silver fir and 32% in European beech.

One important challenge was that seed harvest records reflect both biological seed availability and ‘human’ demand for seeds. Foresters collect seed when they are needed, and demand for seed also declined over time. To address this, we accounted for seed collection effort in our analyses. Even after doing so, the decline in viable seed production remained, suggesting that the pattern cannot solely be explained by people collecting fewer seeds.

Summer warming emerged as the strongest driver of the decline. Across species, hotter summers were linked to lower viable seed output. Spring temperatures and growing-season moisture also affected reproduction, but they explained less of the long-term decline than summer warming.

We also found that climate effects differed among local populations. A warm or dry year could have different consequences depending on the long-term climate of a site. This points to a possible role for local adaptation or acclimation.

A second line of evidence of fecundity decline came from the MASTREE+ database, an independent open-access dataset of plant reproduction. For the same period and species, we found declines in masting: the boom-and-bust pattern of seed production that many trees rely on to produce viable seeds.

Our findings suggest that climate change is reducing the reproductive capacity of important European forest trees. This has direct implications for forest regeneration and seed supply. If viable seed crops continue to decline, nurseries may face shortages of provenance-appropriate seed, and forests may have less capacity to recover after disturbance.

The next step is to connect these fecundity trends with long-term regeneration data. Are declining seed crops already translating into fewer young trees, or are other ecological processes of greater influence?

Read the paper here:
https://rdcu.be/figE9

Foest J.J., Szymkowiak J., Dyderski M.K., Kelly D., Kunstler G., Jastrzębowski S., Bogdziewicz M. 2026. Forest fecundity declines as climate shifts. Nature Climate Change.

How do trees balance the number and quality of seeds during mast years? In our new paper in New Phytologist, led by Kasia Kondrat, we tested this question in European beech using data from 2,792 trees across 123 populations. Contrary to the expectation that producing more seeds should reduce investment per seed, high-seeding years produced heavier seeds. However, seed chemistry changed: protein content declined with increasing seed production, while lipid content increased. We also found that seed mass and protein content were lowest toward the climatic margins of the species’ range. Read the paper here!

This paper is a product of the European Beech Reproduction Network, a collaborative initiative coordinated by our lab to monitor beech reproduction across Europe using a standardized, lightweight field protocol. The network was established to understand how seed production, pollination, seed predation, tree size, and climate interact across the species’ range. This study shows the value of coordinated continental-scale sampling for answering questions that cannot be addressed from single sites or regions alone.

We are continuing to expand the network and welcome new collaborators with access to European beech populations! Please, get in touch if interested.

European Beech Reproduction Network – Forest Biology Center

Sebastian joined our team in January 2026, working on the climate change biology of trees reproduction, which will include climate gradients in fecundity, seed traits, local adaptations, and more. Stay tuned for outcomes!
Godspeed Sebastian 🙂

In a new study published in Proceedings of the National Academy of Sciences, we show that in temperate European forests, years of seed failure are more strongly synchronized over space than mast years with high seed production. Using 36 years of data from over 400 sites and seven dominant tree species, we demonstrate that regional coherence in tree reproduction is driven primarily by synchronized seed scarcity, not abundance. Among-species synchrony was largely local, suggesting that forest diversity buffers food webs against continent-scale boom–bust dynamics. Our findings highlight the ecological importance of widespread reproductive failure and have implications for wildlife dynamics, forest regeneration, and seed sourcing under climate change. Read the paper here!

Reproduction is essential for forests to recover from disturbance and adapt to climate change, yet it is often overlooked in climate impact assessments. Our new study, published in Ecology Letters, shows that climate warming has likely already reduced the natural year-to-year variation in seed production of European beech (‘masting’), with declines of up to ~54% under current conditions. Looking ahead, these losses could become even more severe, reaching up to ~83% under moderate future warming scenarios. This matters because strong fluctuations in seed production help trees pollinate successfully and overwhelm seed predators, ensuring enough viable seeds are produced. Importantly, the strongest effects are expected at the colder edges of the species’ range. Thus, contrary to common assumptions, cooler regions and high elevations appear to offer no safe haven: reduced seed production is likely to limit forest regeneration, species movement, and long-term forest resilience as the climate continues to warm.
Read the paper here!

Our new study, published in Oikos, shows how flexible pollinator communities sustain reproduction in the mast-seeding tree Sorbus aucuparia. Despite large year-to-year swings in flowering intensity, pollination efficiency remained high, driven by dynamic shifts in pollinator composition. Bumblebees dominated during abundant flowering, while solitary bees became proportionally more important when flowers were scarce. These results reveal that pollinator life histories and network flexibility buffer animal-pollinated trees from pollination failure, helping explain why strong masting can evolve even in insect-pollinated species.
👉 Read the paper in Oikos.

The press release associated with the paper!

Global study reveals how weather drives plant reproduction—and how climate change may disrupt it.

A major new study published in Nature Communications has uncovered the global patterns linking weather and reproduction in perennial plants. The research, led by Valentin Journé and Michał Bogdziewicz from Adam Mickiewicz University in Poznań, analyzed long-term seed production records from 746 populations of 331 species across all vegetated continents.
The team found that temperature is the dominant cue for triggering reproduction, although its influence weakens in the wettest and driest climates.

Plants often reproduce in pulses—years of mass seed production followed by years of scarcity—a phenomenon known as masting. By examining decades of data, the researchers showed that in temperate and boreal zones, plants usually produce more seeds after warm years, while in tropical forests, reproduction peaks after unusually cool periods. This striking contrast means that global warming could amplify reproductive failures in the tropics, while making reproduction more regular—but less synchronized—in temperate forests.
“Our analysis shows that the same climatic force can have opposite effects in different parts of the world,” says Valentin Journé, lead author. “Tropical forests, which rely on rare cool spells to trigger flowering, may face widespread declines in reproduction as these events become even rarer.”

The study also found that plant species that show the most extreme seed production cycles—such as oaks, beeches, or some conifers—are the most sensitive to temperature fluctuations. “These hypersensitive species synchronize reproduction over vast areas,” explains Michał Bogdziewicz. “That makes them particularly vulnerable: even small shifts in temperature patterns can disrupt this synchrony and weaken the benefits of masting, like pollination success and predator satiation.”

The researchers warn that such disruptions could cascade through ecosystems. Many animals—from rodents to birds and large herbivores—depend on masting events for food, and reduced seed years may slow forest regeneration. “Masting shapes how forests feed and renew themselves,” adds Jessie Foest, co-author of the study. “Understanding its climatic drivers helps us foresee where ecosystems are most at risk under ongoing warming.”
By providing the first global test of long-standing ecological theories, the study offers a framework for predicting how plant reproduction will respond to changing climates. As Bogdziewicz summarizes, “We are finally able to see the big picture—how weather links the lives of plants around the world, and how those links are now being tested by climate change.”

Journé V., Kelly D., Hacket-Pain A., Pearse I., Szymkowiak J., Foest J., Kondrat K., Oberklammer I. Pesendorfer M., Satake A., Bogdziewicz M. (2025) Weather drivers of reproductive variability in perennial plants and their implications for climate change risks. Nature Communications, https://doi.org/10.1038/s41467-025-64300-6

Over new study, based on 39-year of ecological monitoring in Maine, USA,  analyzed white-footed mice (Peromyscus leucopus) abundance and associated forest and climatic data. We found that mouse abundance increased by ~67 % and average weight by ~15 % during the study period. These trends were driven primarily by rising acorn production — a result of both forest maturation (larger oak trees producing more seeds) and warmer spring temperatures. Mice that were heavier also showed higher survival probabilities. Our findings underline how long-term shifts in resource availability—mediated by forest growth and climate change—can cascade through ecosystems by altering consumer population dynamics and traits. Read the full paper here: https://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2656.70114