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FRAN ALEXANDER: The mighty oaks

Huge collection of animals rely on these big trees by Fran Alexander | June 8, 2021 at 1:00 a.m.

We assume they'll always be there, that they'll stand by us through thick and thin, that they're the definition of strength. However, this year's freezing weather shocked our mighty companions, the oaks, knocking back the male flowers (catkins) that earlier had been busily spreading pollen. The tiny female flowers tucked among the first tender leaves also froze. Now that new leaves have regrown, those sub-zero moments are a passing memory for humans. The trees, however, have taken body blows.

After that last freeze, it was time to read Doug Tallamy's newest book, "The Nature of Oaks." He is also the author of, "Bringing Nature Home," which should be required reading for landowners and city planners. That book explains clearly why invasive plants really mess up ecosystems. Bradford (Callery) pear trees and honeysuckle bushes are local invasive examples. Oaks, however, are natives.

Globally there are approximately 600 species of oaks and 90 live in North America. Tallamy says during its "impressive life span, a single tree will drop up to 3 million acorns and serve as a lifeline for countless creatures." Acorns are critical high protein and carb food for turkeys and many ducks, and are food for dozens of bird species from titmice to towhees to crows to quail.

Oaks seem to understand diversity. Since their flowers are more likely to produce acorns if pollinated by other oaks in their vicinity, apparently they frown on inbreeding. They also provide shelter and nursery platforms for a multiplicity of critters, each of which plays an ecosystem role for the tree.

Some woodpeckers stash acorns in holes they've drilled for the next winter's dining, and the author gives much praise to blue jays. "Oaks and jays are thought to have hit if off right at the start," Tallamy writes, explaining that this species buries one acorn at a time over a wide territory, possibly distributing up to 4,500 each fall. Since jays probably only remember about a fourth of their hiding places, their aerial acorn transport has made it possible for oaks to spread faster around the earth than any other tree species.

The mammals that feed on acorns range from black bears to chipmunks, squirrels to deer, raccoons to rodents and almost every other mammal in between. (Hogs come to mind.) But the book is especially attentive to the insects that inhabit, feed and reproduce on oaks probably because Tallamy is a professor and chair of the Department of Entomology and Wildlife Ecology at the University of Delaware. His main research goals have been to "better understand the many ways insects interact with plants and how such interactions determine the diversity of animal communities."

Boom and bust acorn years directly affect every organism dependent on oaks, from the microscopic ones underground up to those nibblers on the topmost leaves. Apparently in some years oaks allocate their available energy to growth and other years more to reproduction. It will be important to understand how those in Northwest Arkansas will handle this year's lost acorn crop and depleted reserves that they had to use to re-leaf after the freeze. They possibly will have to override reproduction for a while to build up their strength again. If the climate shifts, these kinds of changes will play out in the local web of life.

Birds are highly dependent on caterpillars. Tallamy was shocked to find that some caterpillar species overwinter in bark nooks or sit still pretending to be twigs to avoid detection. In below freezing temps, "they rely on glycerin, the same chemical that we use to make car antifreeze, to keep their cells from bursting." Because grain is not enough for some birds, they need trees that support the caterpillar stages so they can survive the winters and to feed hatchlings in the spring. Tallamy reminds us, "...most of our bird species cannot reproduce without a ready supply of insects," and "...when we reduce the amount of plants in any given place, we reduce the diversity and abundance of insects."

About this keystone plant, the ecologist says, "No other tree genus supports so much life." As an example, research has found (so far) that "511 species of moths and butterflies develop on oaks, nearly 100 more species than their closest competitors," and he adds, "oaks are top life-support trees in 84% of the counties in North America."

Humans are part of the plants/bugs/birds/beasts/etc. eco cycle. We have a lot to learn from oaks about keeping all of that in balance.

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Freeze report

To see the May 2021 report on Northwest Arkansas’ freeze event, visit the Arkansas Department of Agriculture at agriculture.arkansas.gov/forestry, select “Forest Health,” then choose “Forest Health Monitoring Reports” from the left side of the page.

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