Columns / Discourse / January 28, 2009

The dead of winter

Hello, sports fans! Well, as you can see, we’re up to our butts in winter. This isn’t really the best time to be going outdoors and looking at nature, but that certainly doesn’t stop it from happening. In fact, with the exception of migrating birds, nearly every creature found here during the rest of the year is still here in one form or another, either under or above the blanket of snow. Herbaceous (non-woody) plants might look dead, but not only are their dead bits decomposing and enriching the soil, but in many ways they aren’t even dead. The flowers of annual plants, which live for only one year, have become seeds, which are currently riding out the winter in hopes of germinating come springtime.

Perennials, which re-grow every year, are still present underground in the form of roots and tubers. Insects are, for the most part, in egg or pupa form, their parents having long since died. While the furrowed bark of older trees makes an optimal and easy spot for young insects to winter, egg cases can also be found on outlying twigs, shrub stems, and in fact on almost any exposed plant remains above the snow. Often insects will specialize their egg-laying habits to one plant species.

One especially interesting form of insect wintering involves “galls,” or small round growths on plants, stems and twigs. For example, the larvae of certain species of gall wasps burrow into oak twigs when they hatch and, through a process not quite fully understood, induce the tree to produce a growth in which the larvae survive the winter. They can feed on the interior tissues of the gall while at the same time being protected from most environmental effects. They are not, however, protected from other insect species that know that there are juicy, nourishing grubs inside.

Speaking of trees, let’s talk about those for a while. I think that when people get their pictures taken they should say “trees” instead of “cheese.” Try it next time. Cheese is great and all, but without trees humanity would still be slime on a rock. As far as organisms that endure through the winter go, trees are the most visible and helpful of them all. An old tree is an ecosystem unto itself throughout the year, with or without leaves. Not all broadleaf trees are blessed with gorgeous architecture when their leaves fall, but Knox is chock full of ones that are: the pillar-like tulip tree at the southwest corner of Alumni Hall, the spreading white oak between Post Hall and the quads, the bald cypress between Beta and TKE whose trunk tapers off to a perfect point—ah! Glory. The bald cypress, of which there are two others in front of SMC, is particularly interesting in that it is one of very few conifers that drop their leaves in winter. Its relatives — pines, spruces, firs, hemlocks — can be seen all over campus still wearing their spiny coats, photosynthesizing away while the slow-growing broadleaves lie dormant.

Trees provide a home not only for insect species riding out the winter in relative immobility, but also for highly active mammals such as Knox’s ubiquitous squirrels. These live for the most part in nest-like “dreys,” which can be seen in the upper, outer branches of trees that have lost their leaves. Squirrels spend most of their time searching for nuts and acorns that they buried in the warmer months when such things were abundant. You can trace their spastic activities by following their tracks in the snow. The only times when their tracks are invisible is when there is no snow or, much worse, when the snow is frozen over. In this case, there are only two ways in which campus squirrels can reach the ground: when we break through the ice with our own footprints or when the warm steam tunnels running from building to building melt all of the ice and snow above them.

Thanks to John Hanson Mitchell for writing the book “A Field Guide to Your Own Back Yard,” which provided some information for this column.

Sam Bouman


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