San Francisco
PARASITIC fungi are helping to nurse ailing forest ecosystems back to health.
By injecting the fungi into the heartwood of healthy trees, American biologists
hope to recreate habitats for woodpeckers and other creatures that have been
destroyed by decades of 鈥渟alvage logging鈥�.
Sick and dying trees provide shelter for birds, mammals and reptiles. But in
many forests across the US, loggers harvest trees showing the first signs of
fungal infection to produce pulp for paper makers. Although they plant
replacements, these are usually harvested before they start to rot.
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鈥淚n some places there aren鈥檛 any sick trees left,鈥� says Catherine Parks, a
plant pathologist at the Pacific Northwest Research Station in LeGrande, Oregon.
鈥淲e needed something to jump-start the process that creates this habitat.鈥�
In the past, forest managers had tried blasting off the tops of trees with
explosive charges or burning their roots. But animals didn鈥檛 seem to find
artificially damaged trees so attractive, and the trees were so severely
weakened that they could only provide shelter for a few years.
So Parks and her colleagues decided to see if they could accelerate the
natural process of fungal infection in a group of western larch trees in
Oregon鈥檚 Winema Natural Forest. They first established that the heartwood of
western larch trees was normally rotted by the fungi Phellinus pini and
Fomitopsis pinicola. They then took wooden dowels soaked in liquid
cultures of the fungi and inserted them into holes drilled into the centre of
trees.
In an initial trial, the fungi took hold in every one of 60 trees injected
two years ago. Ten are already hosting woodpeckers, which is about twice the
nesting rate seen in blasted trees, says Todd Forbes of the US Forest Service in
Chemult, Oregon, who worked on the trial. And while the fungi eat at the trees鈥�
hearts, they don鈥檛 seem to impede growth鈥攚hich means that the trees should
provide shelter for forest creatures for decades.
Parks argues that the new technique should also appeal to loggers, because
the dowel-infected trees are less likely to fall unexpectedly than those that
have been blasted or burnt. Forest managers are already showing interest, she
says.
Spurred by their success, the researchers have now launched a trial of 5000
trees, including lodgepole pine, ponderosa pine, red cedar and Douglas fir, in
16 forests throughout the western US.