Water Resources Research Act Program

Details for Project ID 2010GA233B

Assessing impacts of hemlock demise on a southern Appalachian stream using aquatic macroinvertebrates

Institute: Georgia
Year Established: 2010 Start Date: 2010-03-01 End Date: 2011-02-28
Total Federal Funds: $18,000 Total Non-Federal Funds: $36,000

Principal Investigators: Darold Batzer

Project Summary: Hemlock trees in the north Georgia mountains are being decimated by a severe insect pest, the hemlock wooly adelgid. The demise of hemlocks could dramatically affect the ecology of Appalachian streams in Georgia in three ways: 1) the death of hemlocks could reduce riparian shading, alter temperature and light regimes of streams, and negatively affect biota; 2) biota in streams adjacent to hemlocks treated with imidacloprid insecticide designed to preserve the trees might be negatively affected by those applications; and 3) once the hemlock trees die, a massive influx of woody debris into streams might occur and have long term consequences for stream biota. For this project, I will experimentally assess the relative importance of these impacts using aquatic invertebrates as response organisms. I have randomly selected 21 plots in gravel, cobble riffles of Billingsley Creek, Chattahoochee National Forest, Georgia; 9 plots were located along a reach of stream where hemlock trees are currently being protected by imidacloprid insecticide, and 6 plots each were located in upstream and downstream areas not protected and where trees are dead. Aquatic macro invertebrates will be sampled in October 2009, and April and July 2010. At that point, sets of dead hemlock wood will be added to 11 of the 21 plots (roughly half) at 10 times ambient levels, and then invertebrates will be resampled in October 2010, and April and July 2011. By comparing reaches (with and without live trees, with and without insecticide) and plots (with and without wood), the relative importance of tree loss (shading), insecticide, and wood influx to macroinvertebrates can be assessed. I predict that only wood influx will have a pronounced impact.