Demographic consequences of heterogeneity in conspecific density dependence among mast fruiting tropical trees

The role of conspecific density dependence (CDD) in the maintenance of
species richness is a central focus of tropical forest ecology. However,
tests of CDD often ignore the integrated effects of CDD over multiple
life-stages and their long-term impacts on population demography. We
combined a 10-year time series of seed production, seedling recruitment
and sapling and tree demography of three dominant Southeast Asian tree
species that adopt a mast fruiting phenology. We used these data to
construct individual-based models that examine the effects of CDD on
population growth rates (λ) across life-history stages. Recruitment was
driven by positive CDD for all species, supporting the predator satiation
hypothesis, while negative CDD affected seedling and sapling growth of two
species, significantly reducing λ. This negative CDD on juvenile growth
overshadowed the positive CDD of recruitment, suggesting the cumulative
effects of CDD during seedling and sapling development has greater
importance than the positive CDD during infrequent masting events.
Overall, CDD varied between positive and negative across life-history
stages for all species, suggesting that assessments of CDD on transitions
between just two stages (e.g. seeds-seedlings or juveniles-mature trees)
likely misrepresents the importance of CDD on population growth and
stability.