Forest Service (FS) research has provided the first estimates on the impact the loss of eastern hemlock will have on the water dynamics of the southern Appalachian mountains. In the June 2007 issue of Ecological Applications, researchers Chelcy Ford and Jim Vose from the FS Southern Research Station (SRS) Coweeta Hydrologic Laboratory present findings on eastern hemlock rates of transpiration (the amount of soil water taken up by trees) from a 2-year study in western North Carolina.
Eastern hemlock, a keystone species in the streamside forests in the southern Appalachian region, is already experiencing widespread decline and mortality and may be decimated by the hemlock woolly adelgid (a tiny nonnative insect) within the next 10 years. As a native evergreen capable of maintaining year-round transpiration rates, eastern hemlock plays an important role in the ecology and hydrology of mountain ecosystems. Hemlocks provide critical habitat for birds and other animals; their shade helps maintain the cool water temperatures required by trout and other aquatic organisms in mountain streams.
No other native evergreen in the southern Appalachians will likely fill the ecohydrological role of eastern hemlock if widespread mortality occurs, says Ford, ecologist with the Otto, NC unit where Vose is project leader. With the loss of this species, we predict changes to streamflow, streamside forest structure, and soil moisture that will have to be addressed by land managers.
Hemlock woolly adelgids attach themselves to the base of the needles of the eastern hemlock, feeding on carbon fixed by the trees, slowing growth and causing the needles to drop. Needle loss causes the crown of the tree to thin and dieback in branches; in a surprisingly short timeusually 5 to 10 yearsthe tree fades away and dies.
To estimate the impact the loss of hemlock will have on the water balance, the researchers measured transpiration rates over a range of t
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Contact: Chelcy Ford
crford@fs.fed.us
828-524-2128
Southern Research Station - USDA Forest Service
9-Jul-2007