Acorns Abound!
While working in my garden this autumn, I noticed there were more acorns than in previous fall seasons. The ground was carpeted by oak nuts.
Is this abundance of acorns a harbinger of a severe winter? In fact, it is not. It is a mast year. Mast is a term derived from Old English mæst, which means the fruit of forest shrubs and trees, which are wind-pollinated species.
What are nature’s signs of a mast year? The characteristics are synchronization: simultaneous widespread production of large seed quantities of many trees, and high seed production: a thick ground acorn layer, a single oak tree may drop thousands of acorns.
Why does this phenomenon occur? There are three categories of hypotheses. Economies of scale can be due to predator satiation (a proportion of seeds can escape consumption and lead to new trees) or pollination efficiency (from reproductive synchronization). Both ideas assume that a variable, large reproductive effort is more efficient than a consistent small effort.
Resource matching may relate to the availability of water, carbon, and nutrients (phosphorus and nitrogen).
Proximate drivers, such as weather-related cues like spring frost and summer drought, may influence the critical times for fertilization and fruit maturation.
The bottom line is that mast years can have both positive and negative effects on ecosystems. A mast year may result in an increased population of frugivores (seed-eating mammals and birds) like rats, which can invade fields, or mice, which increase Lyme disease prevalence since these animals are tick hosts. The good news is these rodents eat gypsy moths. A high number of small mammals may boost their predators, kestrels and stoats; deer are more likely to have twin offspring.
Mast years are phenological (periodic events in biological life cycles) events, long-interval but regularly recurring, which contribute to ecosystem dynamics. Have you noticed the abundance of acorns?
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