Toward a comprehensive understanding of seed masting: What do we need to complete the puzzle?
Seed masting (intermittent and synchronized seed production by a plant population) interests many researchers in plant ecology and silviculture. Several mechanistic hypotheses have been proposed to explain its patterns and causes both deductively (i.e., theoretically) and inductively (i.e., analyzing field data on plant reproduction, climatic data, and nutritional status). From the latter perspective, diverse findings have been presented in diverse fora, including this symposium. Clearly, effort is needed to integrate these findings in pursuit of a comprehensive understanding of masting that is consistent with theory.
Higher temperatures or drought in the previous year are often proposed as proximate causes of masting. Recently, a ΔT model highlighted the predictive power of temperature differences between summers 1 and 2 years prior to masting, although the underlying mechanism was unclear. Meanwhile, nutritional conditions (e.g., levels of nitrogen, phosphorous) in the soil or wood can also influence masting. Here, I attempt to integrate these diverse findings into a single framework. Using the resource-budget model and predator satiation hypothesis as a basis, I argue that three pieces are necessary to complete the masting puzzle (taxon-specific flowering processes, ecosystem nutrient cycling, and the population of pre-dispersal predators) and that the diverse findings of the past reflect differences in the relative roles of these three pieces.