Masting synchrony in northern hardwood forests: super‐producers govern population fruit production

Abstract

Summary Trees commonly reproduce via masting cycles, which involves synchronized inter‐annual variability in fruit crop size. A few individuals in a population will commonly produce much more fruit than others. If these trees produce fruit more frequently, as indicated by a lower inter‐annual variability in fruit production, they may dominate fruit production over time. By measuring fruit production of 1635 individuals of 10 temperate tree species across 4 years in northern lower Michigan, we estimated the inter‐annual variability and synchrony in each species. We compared fruit production estimates with measurements of tree size, soil nutrient availability and neighbourhood crowding to investigate the source of inter‐individual variation in number of fruit produced. We found that trees’ fruit production increased with tree size. The trees that accounted for the largest proportion of total fruit production had lower inter‐annual variability and higher synchrony in fruit production. These ‘super‐producer’ trees tended to have high nutrient availability and few neighbouring trees, but there were no effects of nutrient availability or neighbourhood crowding on fruit production in the population as a whole. Synthesis. Masting is a population‐level phenomenon, and is typically studied at this level. However, when we apply individual tree observations of fruit production to this phenomenon, it reveals super‐producers which produce fruit more consistently than the rest of the population. By reducing inter‐annual variability in fruit production, but increasing synchrony and making large numbers of fruit, super‐producers may be able to reap the benefits of masting while governing population fruit production over time.

Foodwebs based on unreliable foundations: spatiotemporal masting merged with consumer movement, storage, and diet

“…, Milleron et al. , Minor and Kobe ) is critical not only for useful estimates and predictions of mast supply. It also governs the space–time variance in the canopy and, through dispersal, provides the foundation for ground foragers.…”

“…). There are sometimes direct counts from the canopy (LaDeau and Clark ) or from the ground (Minor and Kobe ). When available, observed fecundity enters as a seed, fruit, or cone count , the fraction of the fruit‐bearing canopy observed , and the standard error assigned to the canopy fraction .…”

“…, Moran and Clark , Milleron et al. , Minor and Kobe ). Environmental predictors together with tree‐level random effects allow for the large differences between individuals.…”

Fruit production is influenced by tree size and size‐asymmetric crowding in a wet tropical forest

“…Tree size determined reproductive output in all species. Smaller trees were unable to reproduce until they reached a species‐specific size threshold (Figure ; Minor & Kobe, ; Thomas, ; Wright et al, ) which was directly related to species maximum size. Our study provided a rare opportunity to confirm that a simple relationship ( D thres = ½ D max ) from Barro Colorado Island, Panama (Visser et al, ), holds true at La Selva, Costa Rica (Figure ).…”

“…After reaching maturity, larger trees are likely to produce more fruit (Greene & Johnson, ; Snook, Cámara‐Cabrales, & Kelty, ), possibly due to greater access to resources (Carbone et al, ; Han, Kabeya, Iio, & Kakubari, ). However, even among large, potentially reproductive individuals of the same species, reproduction is unequal, with most of the fruit being produced by a few individuals (González‐Martínez et al, , Herrera & Jovani, ; Minor & Kobe, ; Moran & Clark, ). This variation among individuals indicates that there are additional factors influencing fruit production in trees.…”