Facing unpleasant changes in aftermath of hemlock die off

As if the death of hemlock trees across the Southern Appalachians wasn’t bad enough already, forest researchers believe the loss of hemlocks will alter the carbon cycle of forests.

An exotic insect known as the hemlock wooly adelgid has a death grip on hemlocks throughout the mountains. The giant hemlocks are an anchor tree species in the ecosystem and their loss could have severe ripple effects, from species that depend on them to the cool, moist microclimates found under their dense evergreen branches.

Forest service researchers at the Coweeta Hydrological Laboratory in Macon County now believe the die-off of hemlocks will also have a detrimental effect on hydrology and carbon cycle.

“The study marks the first time that scientists have tracked the short-term effects hemlock woolly adelgid infestations are having on the forest carbon cycle,” said Chelcy Ford, an ecologist with the Southern Research Station who was involved in the research.

Researchers tracked changes in the carbon cycle of infected hemlock stands over a 3-year period. Scientists measured components of the forest carbon cycle — including tree growth, leaf litter and fine root biomass, and soil respiration — finding a decline of 20 percent or more for some of the variables in just three years.

Another piece of news emerging from the research is that hemlocks are dying far more rapidly than initially feared. A total loss of the tree is expected with the next decade.

Researchers noted that other tree species are quick to occupy the space given up by their dying hemlock neighbors.

“We’ll continue to monitor this, but it’s still too early to predict just how different these forests will look 50 or 100 years from now,” Ford said.

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