Environmental variation drives continental‐scale synchrony of European beech reproduction

Abstract

Spatial synchrony is the tendency of spatially separated populations to display similar temporal fluctuations. Synchrony affects regional ecosystem functioning, but it remains difficult to disentangle its underlying mechanisms. We leveraged regression on distance matrices and geography of synchrony to understand the processes driving synchrony of European beech masting over the European continent. Masting in beech shows distance‐decay, but significant synchrony is maintained at spatial scales of up to 1,500 km. The spatial synchrony of the weather cues that drive interannual variation in reproduction also explains the regional spatial synchrony of masting. Proximity played no apparent role in influencing beech masting synchrony after controlling for synchrony in environmental variation. Synchrony of beech reproduction shows a clear biogeographical pattern, decreasing from the northwest to southeast Europe. Synchrony networks for weather cues resemble networks for beech masting, indicating that the geographical structure of weather synchrony underlies the biogeography of masting synchrony. Our results support the hypothesis that environmental factors, the Moran effect, are key drivers of spatial synchrony in beech seed production at regional scales. The geographical patterns of regional synchronization of masting have implications for regional forest production, gene flow, carbon cycling, disease dynamics, biodiversity, and conservation.

Tree hazards compounded by successive climate extremes after masting in a small endemic tree,Distylium lepidotum, on subtropical islands in Japan

“…The monitoring of carbohydrate reserves should thus be crucial for the early detection of forest die‐offs. Masting in predominant trees is often synchronized on a continental scale (Ascoli et al, 2017 ; Bogdziewicz et al, 2021 ; Vacchiano et al, 2017 ). With respect to masting and plant size, large trees have higher synchrony than small trees (Bogdziewicz, Szymkowiak, et al, 2020 ).…”

“…Many tree species undergo masting phenology for regeneration, and relatively long nonflowering periods may occur in individual trees (e.g., Ascoli et al, 2017 ; Bogdziewicz et al, 2020 , 2021 ; Fernández‐Martínez & Peñuelas, 2011 ; Kelly & Sork, 2002 ; LaMontagne et al, 2020 ; Pearse et al, 2017 ; Vacchiano et al, 2017 ). In masting years, blooming trees pay huge resource costs for massive seed production, requiring nonnegligible investments in stored carbohydrates and nitrogen (Han et al, 2011 , 2014 ; McDowell et al, 2000 ; Miyazaki, 2013 ; Newell, 1991 ).…”

Climate change and plant reproduction: trends and drivers of mast seeding change

“…This scale is relevant for satiating mobile generalist seed predators [14] and has the potential to push and pull ecosystem dynamics at regional scales [62,63]. Theory suggests that regionally correlated weather variation (the Moran effect) is the main driver of synchronized seed production at this spatial scale [12,64].…”

“…Unpacking temporal changes in reproductive synchrony thus requires the study of coupled fluctuations in both weather and seed production over geographical extents ranging from local field studies to continents. Despite the importance of synchrony for plant recruitment and community dynamics, and evidence that spatial synchrony is sensitive to temperature [64], temporal changes in spatial synchrony of seed production are poorly explored.…”

Modes of climate variability bridge proximate and evolutionary mechanisms of masting

“…The spatial coherence of proximate mechanisms of seed production (i.e. the Moran effect) plays a major role in synchronizing plant reproduction over different scales [10,18,54,69]. Synchrony in reproduction occurs when conditions favourable for each reproductive stage, from resource priming to fruit ripening, align not only in time, but also in space [30].…”