Forecasting seed production in perennial plants: identifying challenges and charting a path forward

Abstract

Interannual variability of seed production, known as masting, has far-reaching ecological impacts including effects on forest regeneration and the population dynamics of seed consumers. Because the relative timing of management and conservation efforts in ecosystems dominated by masting species often determines their success, there is a need to study masting mechanisms and develop forecasting tools for seed production. Here, we aim to establish seed production forecasting as a new branch of the discipline. We evaluate the predictive capabilities of three models -foreMast, DT, and a sequential modeldesigned to predict seed production in trees using a pan-European dataset of Fagus sylvatica seed production. The models are moderately successful in recreating seed production dynamics. The availability of high-quality data on prior seed production improved the sequential model's predictive power, suggesting that effective seed production monitoring methods are crucial for creating forecasting tools. In terms of extreme events, the models are better at predicting crop failures than bumper crops, likely because the factors preventing seed production are better understood than the processes leading to large reproductive events. We summarize the current challenges and provide a roadmap to help advance the discipline and encourage the further development of mast forecasting.

Positive spatial and temporal density‐dependence drive early reproductive economy‐of‐scale effects of masting in a European old‐growth forest community

“…While predator satiation only works in combination with a certain degree of predator starvation (Zwolak et al, 2022), pollen limitation is likely insensitive to flowering efficiency in the previous year (Norton & Kelly, 1988), other than due to indirect effects mediated by individual resource limitation (Abe et al, 2016;Pesendorfer & Koenig, 2016). As evidence is increasing that species and populations vary in the mechanisms by which masting emerges from the interactions between internal resource dynamics and external (synchronizing) mechanisms (Bogdziewicz et al, 2017;Nussbaumer et al, 2018), a general framework which captures the sequential thresholds that have to be surpassed to achieve synchronized, temporally variable seed production in plant populations would be essential (Beck et al, 2024;Journé et al, 2023;Pesendorfer et al, 2021). This framework could also provide the necessary foundation to advance our understanding of selection pressures, as well F I G U R E 6 Spatially density-dependent seed predation of Fagus sylvatica.…”

Widespread breakdown in masting in European beech due to rising summer temperatures

“…It is an increasingly economically important forest‐forming species and one of the most diversely used trees in Europe (Houston Durrant et al., 2016). Reproduction in beech populations is driven by a series of weather effects on the sequential processes of bud initiation (floral transition) in the year before reproduction, flowering and pollination in spring, and fructification throughout the summer until seed drop in autumn (Journé et al., 2023). The dominant cue for seed production, that is, summer temperature, is spatially conserved, suggesting that flower initiation occurs at the same time throughout the range (Journé et al., 2024).…”

“…In beech, weather affects seed production throughout the reproductive trajectory from flower initiation to seedfall (Journé et al., 2023). Unlike oak, however, where cues vary between populations (Fleurot et al., 2023), seed production in beech is predominantly driven by June–July temperature anomalies throughout its range (Bogdziewicz et al., 2021; Drobyshev et al., 2010; Journé et al., 2023, 2024; Vacchiano et al., 2017). The timing of this dominant temperature cue is exceptionally stable across geographical and climatic space (Bogdziewicz, Journé et al., 2023).…”

“…Weather cues are deviations from baseline conditions (e.g., temperature and precipitation anomalies in summer and spring) that lead to years of high reproductive output (Bogdziewicz, 2022;Espelta et al, 2008;Kelly et al, 2013;Koenig et al, 2016;Vacchiano et al, 2017). In beech, weather affects seed production throughout the reproductive trajectory from flower initiation to seedfall (Journé et al, 2023). Unlike oak, however, where cues vary between populations (Fleurot et al, 2023), seed production in beech is predominantly driven by June-July temperature anomalies throughout its range (Bogdziewicz et al, 2021;Drobyshev et al, 2010;Journé et al, 2023Journé et al, , 2024Vacchiano et al, 2017).…”

How to measure mast seeding?

“…Perennial plants frequently exhibit large seed crop production in sporadic years, a behavior referred to as mast seeding (Kelly, 1994; Pesendorfer et al ., 2021). This leads to significant fluctuations in food availability that cascade through food webs and can impact plant growth, nutrient cycling, animal migrations, and human disease risk (Clark et al ., 2019; Lauder et al ., 2019; Zuckerberg et al ., 2020; Bregnard et al ., 2021; Journe et al ., 2023). Mast seeding has several key characteristics including interannual variation, synchrony among individuals, temporal autocorrelation, and quasi‐periodicity (Koenig et al ., 2003; Crone et al ., 2011; Schermer et al ., 2020).…”