- Nature Nearby is written by Naturalist Valerie Blaine, who is nuts about trees. She is also the nature programs manager for the Forest Preserve District of Kane County. You may reach her at firstname.lastname@example.org.
Acorns bounce like ping-pong balls on the sidewalk. Hickory nuts plop onto the ground, and walnuts fall with a thud. It’s enough to make you want to wear a helmet! Do you think Chicken Little was right – perhaps the sky IS falling?
The sky is not falling, but thousands of nuts are. The barrage of friendly fire is due to a phenomenon called masting. “Mast” refers to tree fruit. Hard mast comprises hard-coated nuts of all kinds, such as walnuts, hickory nuts, beechnuts, and acorns. Soft mast includes dry seeds without hard husks. Maple seeds (those fun “helicopters”) are examples of soft mast.
It’s a banner year for hard mast. Oaks are particularly prolific, and hickory nut production is way up. Squirrels, unconcerned with falling acorn bombs, are going nuts. Mice are up to their ears in nuts, and deer delight in the abundance of this high-calorie food. In short, wildlife is enjoying a windfall.
Why are there so many nuts this year? What will next fall be like?
The first part of the explanation has to do with energy budgets. Trees either pour all their energy into flowers and fruit, or invest everything in growth.
As for next year? The answer is, “Who knows?” There is no predictable schedule for masting, so it’s anyone’s guess about the next year’s crop. Although this year’s investment has been in the food production, in 2018 it may all be directed to growth.
The production of mast is an all-or-nothing proposal. Prodigality one year contrasts with austerity the next. This means that in an “off” year when there is little mast, it’s slim pickings for wildlife, with nary a nut on the ground. Animals have to scramble to find other things to eat. In a mast year, though, there’s so much food that the critters can’t possibly eat it all. They stuff themselves silly until they can’t eat another bite. Many nuts are left uneaten, and an uneaten nut is a tree-to-be.
This feast-or-famine phenomenon has a scientific explanation. In ecology lingo, it’s called a starvation-satiation regime. Walter Koenig and Johannes Knops explained in their article, “The Mystery of Masting in Trees” (American Scientist Jy-Ag 2005) that the unpredictable boom-and-bust of masting is a way of faking out the enemy — in this case, herbaceous predators.
Lean years, with little to no nut production, force animals to diversify their diets. Like mom always said, don’t be a picky eater — eat what’s on your plate! If acorns aren’t on the menu, you’ll have to develop a more cosmopolitan palate. Thus squirrels will eat lots of things, like fungi, berries, leaves, buds and bird seed.
Forest ecologists have proposed various cause and effect scenarios to explain and predict mast fruiting. Weather may be a cue for a mast year, but other factors certainly contribute. Researchers are still investigating the complex triggers for the production of mast crops.
Another puzzling aspect of masting is that trees across a large geographical area synchronize their fruit production. How does an oak tree in St. Charles “know” that it’s supposed to crank out acorns this year in conjunction with oak trees in, say, Elgin or Big Rock?
The answer is somewhat elusive. Scientists suggest chemical signaling, but that theory doesn’t necessarily hold up for today’s fragmented forests. Trees are too far apart — separated by miles of shopping malls, highways and houses. How can they send signals to each other in these disparate woodlands? Synchrony is a masting puzzle that researchers are trying to solve.
Regardless of the unanswered questions, we do know that masting affects the forest community and beyond. Koenig and Knopps call this a trophic cascade. There’s a ripple effect from the little guys (herbivores) to the big guys (carnivores) and everyone in between.
Consider, for example, the following scenario: It’s a mast year, and mice are fat and happy. Deer, too, relish the extra helpings of acorns. The well-nourished mice and deer produce a lot of offspring, resulting in a mini population boom.
Enter the tick. These eight-legged ectoparasites are particularly fond of mice and deer, and they benefit from the increased population of blood-bearing mammals. A portion of the tick population carries Lyme disease, and as the numbers of mice and deer increase, the number of ticks increases, and the probability of ticks transmitting the disease increases. A mast year may therefore have the effect of increasing the occurrence of Lyme disease in a particular area.
There is a positive side to trophic cascade from mast crops. Humans have benefited from bumper crops in centuries past, when nuts and the animals that eat nuts, were food staples. And, from an owl or a coyote’s point of view, an abundant crop of nuts leads to an abundant population of rodents, and this means fine dining for these top predators.
Oaks, hickories, and walnut trees are providing a cornucopia of forest fruit this year. As these trees unload their mast, rest assured that the sky is not falling. The bounty will be relished by wildlife. And the nuts that get left behind hold the promise of the forest’s future.
Harvest of The Acorn Moon
Celebrate the bounty of fall! Join us at our annual “Harvest of the Acorn Moon” festival from 1 p.m. to 4 p.m. Sunday, Oct. 8, at Oakhurst Forest Preserve in Aurora. We’ll have various nature crafts including pumpkin painting, plus outdoor games, folk music, and guided hikes. All ages are welcome to attend this family festival. Harvest of the Acorn Moon has free admission. There is a nominal fee for crafts and refreshments. For information, call 630-444-3190 or email email@example.com.
Valerie Blaine leads guided hikes and tree identification programs throughout the year! You may contact her with questions or comment by email. firstname.lastname@example.org.
SOURCE: Forest Preserve District of Kane County