Pine beetles changing water supply, too
October 3, 2010
CASPER, Wyo. – Mountain pine beetles are a well-known danger to Rocky Mountain forests. New research shows the pests are making changes to the water supply and soil, too.
The University of Wyoming is looking to establish the impact of the pine beetles epidemic on mountain snowpack.
Brent Ewers, an associate professor of botany, is researching the effect of beetle kills in Medicine Bow National Forest.
He tells the Casper Star-Tribune that as the beetles kill pine trees and the trees lose their needles, snowpack rises. But once the trees fall, he says, snowpack lessens because of wind and lack of shade.
“You get a little enhancement at first, when they’re dying, and then lose a lot more after,” Ewers said.
When the trees are dead, they will also stop bringing water into their systems. That leads to more moisture in the soil and then, initially, more in streams.
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High-flowing streams cause erosion, worsened because trees and needles no longer exist to break the flow of water.
Ewers has also found that nitrogen rates in the soil go up when trees die because trees absorb nitrogen. Again, he pointed out the difference between the short-term and long-term effects of beetle kills.
“If all you care about is increased water in reservoirs, we will probably see more from the outbreak, but it won’t be as high quality because of erosion and nitrogen and won’t last forever,” Ewers told the newspaper.
UW researchers are also looking at how the tree kills affect carbon levels in the soil.
Elise Pendall, an associate professor of ecosystem ecology, is studying the possible emissions of carbon from dying trees.
She says her research shows that carbon emissions are staying roughly the same within the first two years of the attack.
Some scientists worried there would be a pulse of carbon from wood and roots decomposing. But Pendall’s research may show that as roots die, carbon emissions from the soil decrease. This means it’s possible that while there is decomposition, the carbon output is offset by the decrease of emissions from the soil.
Pendall pointed out that lodgepole pines are also not the only form of vegetation on a mountainside. And less competition can mean the surviving lodgepole pines as well as other trees grow better and faster.
Just as a commercial forester would thin trees, the outbreak can cause other trees to grow more quickly, she said.
Dan Tinker, a UW associate professor in botany, said the mountainsides aren’t going to become wastelands. Each stand of trees he’s sampled in the Medicine Bow National Forest has some amount of regeneration.
“I think the big finding is going to be that there are still going to be quite a few trees left,” he said.