Naturespeak A naturalist's view of the world

June 5, 2011

Death of an Acorn

Filed under: Uncategorized — wykes @ 10:35 am

Look up “acorn” on the internet and you’ll likely come up with a whole bunch of company names like “Acorn Group” or “Acorn Investments” etc.  Acorns represent the promise of growth and eventual stability – there is, after all, nothing sturdier than an ancient oak.  The implication is that an acorn represents the sure promise of a sturdy future tree (and, by association, sturdy future investment, life improvement, etc.). Unfortunately, there is a slight problem with that scenario. Nuts are lousy investment packages. 

I was driven into thinking about nut mortality by the huge acorn crop produced by our Dollar Lake trees last fall. It was a record crop and the place was under continual attack from falling nuts throughout October. The ground was carpeted with acorns when we locked the place up for the winter. Many of the surviving nuts are now attempting germination this spring, but I know that none of those within my yard will make it.  My mower is not the only reason for this.

In reality, very few acorns actually make it to treedom even in pristine forest conditions.  The odds against any Red Oak acorn achieving anything beyond nutdom, for instance, are somewhere around 500 to 1.  These poor nuts are under assault from the moment they begin development on the parent tree until germination. The slings and arrows of misfortune continue even after a nut becomes a sapling.

The process of making a Red Oak acorn takes two years (White Oak trees cut corners and get their nut crop onto the ground within one growth season). Assuming a developing nut survives the extremes of  cold, heat, wind, and insects over that time period it will then fall to the ground and suffer further indignities at the hands (or is it the mouths?) of  hungry squirrels, chipmunks, mice, deer, and turkeys. Three species of insect – a weevil, a sap beetle, and a moth – are especially hard on Red Oak acorns. It is estimated that at least 80% of the crop is thus rendered into fecal material or fungal mush.

Ah, but there is safety in numbers. As one research paper put it this “impact is diluted by a heavy acorn crop.” Red Oaks’ like other oak species, will attempt to overcome these bad odds by sheer numbers. Last year was one of those banner “shock and awe” years around our place and it appears that many acorns made it to stage 2 – germination.

After a requisite period of winter dormancy, the nuts split at their narrow end and push out a strong radicle, or root. The root tip automatically directs itself into the ground (in the direction of gravity) and burrows down to establish a tap root. The upper portion of the radicle simultaneously splits and issues a sprout which grows upward (opposite of gravity).  This becomes the stem or trunk. The action up to this point is fueled by the nutmeat (aka cotyledons).

There are now a whole lot of little nut trees (see above and here) with multiple pairs of real leaves in one corner of the yard. I did not mow them down, but left them to their own devices. These new leaves will start the process of photosynthesis that will allow these treelets will wean themselves from their cotyledon source. But – now comes the cruncher- these plants will need around 30% sunlight intensity in order to do their p-thing properly. Due to the shade, these little things will be lucky to get half of that.  In short, they will slowly fade in the shade.

To add insult to injury, I noticed that the local crop of Gypsy moth caterpillars have already started their move on my mini-forest. One delicate little leaf had upon it, a delicate little caterpillar who had chewed a delicate little hole into it (see below). There will be more holes and more leaf-eaters to come before this sprouting event is over.

To be philosophical about this, all acorns – even the successful ones that eventually achieve tree status – must die. You see, in order to become a tree, a nut has to stop being a nut. It must figuratively “die” so that it can live on as a tree. So, in effect, acorns are temporary things no matter how you look at them. Acorn mortality makes you think about such deep things.

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