Since then, HWA has continued to decimate hemlock populations, while other species gradually move in to fill their place. A new study from the U.S. Forest Service Coweeta Hydrological Laboratory in North Carolina more closely reveals some of the effects the replacement of hemlock with other species is having on the southern Appalachian forest — specifically on the hydrologic cycle.
As Brantley says in the U.S. Forest Service publication CompassLive, “In the growing season, transpiration rates will likely rise, leading to lower streamflow in the summer. However, transpiration rates in the winter will be reduced, which could cause increased winter stream discharge.”
Not that streamflow is the only thing that would be affected by hemlock loss along riparian areas. The loss of shade is also causing increased water temperatures, threatening eastern brook trout and other species that live in the cold water. That was a problem in Fridley Gap in George Washington National Forest, Va., for example, where American Forests planted 240 trees in riparian areas to restore cooler water temperatures for the benefit of brook trout.
It remains to be seen what these forests will look like in the future, but by researching what to expect, we can hope to head off some of the negative effects to ecosystems.