Decaying Matters

Jonathan Schilling


Biodiversity is the linchpin of conservation, and for good reason. Ecosystems with a richer mix of species experience greater stability, in part because there’s plenty of built-in redundancy. Take one species away and life goes on, more or less. Take too many away and prepare for trouble. But what about areas with an abundance of just a few species?

Case in point: the northern boreal forest, a biome populated by a select group of cold-hardy trees that stretches across vast swaths of Alaska, Canada and Russia. What happens if you remove a single species from an environment where there aren’t that many to begin with?

Jonathan Schilling, an assistant professor of bioproducts and biosystems engineering in the College of Food, Agricultural and Natural Resource Sciences and resident fellow at the Institute on the Environment, is searching for answers with the help of a four-year, $278,000 grant from The Andrew W. Mellon Foundation. Schilling’s Minnesota group and colleagues at the University of Alaska Fairbanks are trying to link observed outcomes of wood decomposition at the very top and bottom of Alaska’s boreal zone to the fungi responsible for it. They want to determine not just the fungi present, but which are the dominant players.

His father was a forester, so Schilling grew up around logging. Early on he noted the lack of a consistent approach to how much wood to leave behind. “I was always wondering, ‘Where’s the science behind all this?’” he says. With pressure growing to find new sources of biomass and no single standard for managing forest residues, his insights could prove critical.

”It’s possible, then, that in a system without much redundancy, small changes among wood-decaying fungi could have a huge impact,” Schilling says. For one thing, different types of fungi decay wood at different rates. Replace a fungus that decays wood slowly with a speedier cousin, and the amount of carbon released could well accelerate.

“Some of these fungi have circumpolar ranges and individuals can be huge,” Schilling says. “Think giant sequoia or blue whale. What happens if a species of boreal wood-degrading fungus disappears? What happens to the carbon cycle? In a low-diversity ecosystem, change could happen on a big scale.”

But where exactly is that tipping point? Even if cutting large areas of forest doesn’t visibly change the composition of the ecosystem, it may be changing the dynamic if the local fungi go defunct.

“If you have a fairly homogeneous system, you could cut down a large area and still preserve diversity,” says Schilling, “but how do you know when it’s too much? When you look at the boreal forest as a carbon reservoir, a change in a single species could have a large impact. Fungi may not seem important, but when you consider the fact that different types of fungi correlate to different rates of decay and different soils generated, that could mean a significant change for our environment.”

Stephanie Xenos is a freelance writer from St. Paul, Minn. She writes a monthly column for Mpls.St.Paul Magazine and has contributed to a number of other publications.