Oak masting drivers vary between populations depending on their climatic environments

Area of Science:

• Ecology
• Botany
• Forestry

Background:

• Masting, characterized by large interannual variation in seed production, is prevalent in wind-pollinated trees like oaks (Quercus petraea).
• This phenomenon significantly impacts forest ecosystem dynamics and the epidemiology of certain human diseases.
• Understanding masting mechanisms is crucial, yet data from climatically diverse populations are scarce.

Purpose of the Study:

• To investigate the drivers of masting variation in sessile oak populations across a broad climatic gradient.
• To compare reproductive characteristics and masting mechanisms in contrasting environments.
• To determine the relative importance of flowering effort and fruiting rate in oak masting.

Main Methods:

• An 8-year fine-scale survey of 150 sessile oak trees across 15 populations.
• Individual recording of annual flowering effort, fruiting rate, and fruit production.
• Analysis of masting drivers in relation to climate and flowering synchrony.

Main Results:

• Female flowering effort, not just fruiting rate, is a major driver of masting dynamics in two-thirds of the studied populations.
• Masting drivers differ significantly based on climate: soft-climate populations rely on flowering synchrony, while harsh-climate populations depend on spring weather.
• Flowering synchrony is key in soft climates, whereas spring weather dictates masting intensity in harsh climates.

Conclusions:

• Flowering effort variability is a critical, often overlooked, component of oak masting.
• Climate-specific factors shape diverse masting mechanisms among populations.
• Accurate future predictions of plant reproductive patterns under climate change require accounting for this diversity.