Nuts and Masting
When I think of the oak-hickory forest,
I think of nuts. Acorns and hickory nuts are a very important
food source for most animals that live in this forest type since the
nuts are large and full of nutrients. Critters like turkeys can
eat whole acorns and grind them up with rocks in their gizzards.
Nearby, squirrels perch on logs and nibble away the outer casings of
the acorns, leaving the debris in a heap below their favorite perch,
then chew up the tasty interior. Native Americans ate a lot of
acorns too, although they processed them by pounding and boiling them
to remove the bitter-tasting tannins.
To
anthropomorphize wildly, oaks and hickories get riled up when they
spend so much of their energy making nuts that just get gobbled down by
Blue Jays and squirrels. Sure, both species like to cache nuts,
hiding a few underground for later snacking, but these critters also
have pretty good memories and tend to go back and eat up the nuts they
have hidden. Luckily, oaks and hickories are even wilier and over
centuries they came up with a strategy known as masting.
Most years,
oaks produce a few nuts --- not too many, but enough to keep the
squirrels, Blue Jays, and turkeys alive. Since these animals
determine how many offspring to produce based on how well nourished
they are, acorn predator populations stay steady, never growing past
the point where the few nuts dropped by the oaks can sustain
them. Then one year, every single oak in an area somehow teams up
and decides this will be the big year, the mast year. Like a
Thanksgiving dinner, the oaks produce so many nuts that the squirrels
eat until their bellies nearly pop. Every animal in the forest
gorges during mast years and hides nuts for the winter, but there are
just too many nuts to use them all. Hundreds or thousands of
leftover nuts litter the forest floor, rolling underfoot, and then
sprouting to grow into oak trees. During mast years, I can almost
hear the oak trees snickering. “Take that, you squirrels!” they
seem to be saying. “We fooled you!”
Hickories,
beeches, and white pines all go through mast years as well, although
their years do not tend to coincide with the oaks’ mast years. In
fact, saying that all oaks mast during the same year is an
oversimplification --- there are actually two main types of oaks that
mast on different schedules. The white oak group contains White
Oak and Chestnut Oak, as well as a few other species, all of which have
rounded leaf lobes with no pointy bits. The red oak group
contains Red Oak, Black Oak, Pin Oak, and Scarlet Oak, all of which
have long points at the end of each leaf’s lobes. These two
groups of oaks seem to speak different languages, with the red oak
group masting in one year and the white oak group masting in another.
Scientists are
still trying to decipher how a group of oaks decides whether to mast in
a certain year. Most likely, oaks respond to weather conditions
like summer droughts and spring frosts, combined with an inherent
tendency not to produce a big crop of acorns every year. However,
I have always wondered if their decision to mast might be a bit more
complicated. In the last couple of decades, scientists have
started turning up startling examples of plant to plant
communication. In one example, an alder tree bitten by an insect
emitted chemicals that alerted the neighboring trees that ravenous
insects were in town. The neighboring trees then produced nasty
chemicals in their own leaves that kept the insects from
nibbling. If trees can “talk” and warn their neighbors to scare
insects away, who is to say that they cannot actually “talk” about
whether now would be a good time to mast?
As I walk down
the Marlene Path, I like to imagine the oaks chattering away above my
head. “So, Jimmy, how are you feeling this year? Ready to
make some nuts?” “Sure, Joe. Those pesky squirrels are
giving me headaches. Let’s stick it to them!”
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