Some Straight Skinny on Soil

I learned I'd been spreading misinformation for about 25 years while attending a potluck dinner a few weeks ago. This article is a public apology to all the people I've misled, and also an attempt to set the record straight.

It all began back when the Institute of Marine Science was a newly established research arm in the University of Alaska, and a distinguished scientist named Mary Belle Allen was recruited for the staff. Dr. Allen's repertoire included studying aquatic microorganisms. She wanted to identify the bacterial populations in lakes in interior Alaska. Soil bacteria often wash into lakes and confuse the situation, so, to do her work properly, Allen needed to know what kinds and what numbers of bacteria inhabited the local soils.

Such tests are standardized and straightforward. Allen hauled equipment and assistants around the countryside to gather samples of soil from forest and field, from under trees and atop rocky ledges. Back in the lab, the samples were put through the customary tests, but they didn't yield the customary results. Many of the samples contained few bacterial cells; some held so few that they could have passed federal standards for sterilized soil.

The chilly soil temperature seemed to be suppressing bacterial growth and reproduction, or so Allen and other scientists speculated. When the story got around, less knowledgeable people jumped to conclusions. Instead of a possible bacteria retardant, cold ground became a sure-fire germ killer. ("Cold?" I said to people during a visit to the temperate zone. "Listen, it's so cold in Fairbanks that the soil's sterilized. I mean, mold doesn't grow in your freezer, right?")

There the matter rested, at least in my mind, for the intervening years---until the dinner party mentioned above. I found myself wandering around the arrayed casseroles in the company of biologist John Bryant. His work links biochemistry and ecology. He's probably best known for work connecting the enormous cyclical swings in arctic hare populations to chemical defenses produced by the plants they eat. So, making small tank, I asked what was new and interesting in research on botanical chemical warfare.

"Some neat stuff," he said. "Keith Van Cleve, Josh Schimel, and Paul Reichardt are working on the breakdown of plant compounds in the soil. Turns out some of the toxic secondary compounds are pretty persistent."

I made mental note to commend Dr. Reichardt, Dean of the College of Natural Sciences, on keeping up with his chemistry research despite administrative loads, and then I felt a little internal warning light come on.

"You mean the chemicals leach out of the fallen leaves and get into the soil? The same chemicals that can make, say, birch and willow inedible for arctic hares?" He nodded, so I blundered on. "And I suppose the toxic compounds can slow the growth of bacteria."

"Sure," he said. "We can get real low bacteria counts in soil, especially if it was a tough year for the plants. During a good year like this one, the trees put more energy into growing and less into chemical defenses so they're closer to garden vegetables in chemical makeup, and you can compost them."

Thus did Dr. Bryant wipe out two myths I absolutely, positively believed about garden-ing in Alaska. The first myth: the soil is so cold bacteria won't grow. The second myth: leaves, clippings, and such take forever to break down because compost heaps don't get warm enough.

Wrong. Low temperatures may slow biological breakdown somewhat, but the real rea-son for slow decomposition and for sterile soil in the Interior seems to be that toxins leach out of our native plants.

I should have known the chill alone wouldn't do it. Maybe bacteria responsible for decomposition don't grow in the freezer, but unwanted life in the refrigerator is another matter. Leave the lettuce drawer for a long weekend, and the Slime That Could Eat Sitka is waiting to crawl out and get you...