Monthly Archives: August 2013

The Stump of Happiness

During the past decade, things have been stressful for some of the trees in the boreal forests around Fairbanks. On average, our growing season is getting longer. Data from the Alaska Climate Research Center show that the growing season has increased from 85 to 123 days in the past century. But rainfall has not increased accordingly. In fact, data suggest that we’ve gotten about 11% drier over this same period. It is rather surprising that we have trees at all, given that we live in an Arctic desert, with average annual rainfall today of only about 11 inches. But our growing season is rather short, and therefore transpiration by the trees is brief enough to make that much water suitable for their growth and reproduction before a long period of dormancy each winter. However, coupled with our climatic changes we’ve also had some bad pest infestations. For about the past decade, aspen leaf-miner moths (Phyllocnistis populiella) have run rampant through the region’s trembling aspens (Populus tremuloides). Aspen leaves, normally green, have been silvered each summer for the past several years by the foraging trails within them of leaf miner larvae. These moths had an explosive arrival, population-wise, in the Fairbanks area, expanding rapidly into our area and inundating our rich aspen forests. Researchers at the university have found that this intensive leaf damage does have a negative effect on aspen growth. Oddly, this spring’s unusual weather seems to have knocked them back so much that we’ve enjoyed our normal green aspen leaves all summer. But, just eyeballing things, more trees than seem normal look stressed and are dying. And there also seems to have been an increase in the winds here. A decade or more ago winds were rarer; it was usually calm. Now, when the winds pick up it is not uncommon to hear a tree come crashing down in the forest. The aspens especially seem to have become vulnerable, and they tend to break off just below the ground, as though some form of upper root rot has weakened them intolerably.

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