Abrupt reproductive responses to weather and shifting climatic signals across thermal contexts in trees

Jessie Josepha Foest , Emilie Fleurot, Maria Bogdańska, Jakub Szymkowiak, Michał Bogdziewicz

Large inter-annual variation in tree seed production is widespread and closely linked to weather. Yet, we know little about the shape of these relationships, their dependence on resources, or their spatial consistency. We fitted boosted regression trees (eight species; 6,491 population-level observations; 352 sites), using prior seeding as proxy for resource status. Predictive performance ranged from rCV = 0.33 to 0.72, yet climatic signals emerged in most species. Non-linear responses to weather were common, often showing sharp transitions over narrow climatic ranges. Prior seeding was influential and frequently modified weather responses, with species ranging from predominantly climatically controlled to strongly resource-dependent. Leading predictors generally remained influential across sites within species, but their strength or relative importance shifted along a gradient from warmer, less thermally variable to colder, more variable sites. Consequently, small climatic shifts may coincide with large changes in reproduction, with the magnitude depending on prior seeding and climatic context.