The Neuse River begins in the Piedmont region of North Carolina, and much of its 275-mile journey to the Atlantic Ocean is through forests that are managed for timber. A new study by U.S. Forest Service researchers evaluates Best Management Practices (BMPs) for silviculture operations to see whether water quality in the Neuse River Basin is protected.
“In the United States, the best quality water comes from forested watersheds, even when forests are managed primarily for timber production,” says Forest Service Southern Research Station (SRS) scientist Johnny Boggs. Boggs is part of the SRS Eastern Forest Environmental Threat Assessment Center, and lead author of a new report that was given to the North Carolina Forest Service and Department of Water Resources, and was also published in the Journal of Forestry.
Researchers have shown that buffers and other BMPs can protect water quality in the Piedmont of Georgia and other states, but there was no information on its effectiveness in the North Carolina Piedmont area.
Boggs and his colleagues measured the amount of sediments and nutrients in small streams located in paired watersheds that drained into the Neuse River to see if concentrations reached levels that would harm aquatic life. The streams were protected by 50-foot forested buffers between the water’s edge and the harvested area. Some trees were selectively removed from the buffer, however, loggers did not construct any roads or skid trails within it. Additionally, loggers spread slash – small branches and debris – over skid trails to help limit soil disturbance. Collectively, these actions and others are called BMPs, and are designed to help protect water quality.
Boggs and his colleagues studied the watersheds for six years after timber harvesting. “We found some changes to streamflow and stream chemistry levels,” says Boggs. Immediately after harvest, there were increased levels of sediments, as some soil in the stream bed was mobilized and deposited downstream, and soils washed into the streams. There were also slight increases in nutrients such as nitrate. However, the changes were not severe enough to harm fish or other aquatic animals.
There were also some unexpected findings. Before the harvest, trees near the stream had been partially shielded from wind by the surrounding forests. After the harvest, these remaining trees were exposed to stronger winds, and during the study, more than one third of them fell down during storms. The largest trees were most susceptible to falling, perhaps due to their weight, shallow rooting depth, and the thin soils often found in some parts of the Piedmont region. Species varied in their resistance to windfall – oaks and hickories blew down most often, while other species such as tulip poplar and sweet gum were more resistant. Keeping tree species that are most resistant to windfall and herbaceous plants can help stabilize the streambank and reduce potential for sedimentation.
“Water quality wasn’t impaired after harvest or after the trees fell,” says Boggs. “Thus, it appears that the management practices are effective in protecting these streams and aquatic species. However, measures should always be taken to prevent windthrow and uprooting of streambanks to ensure that the buffer core functions are not compromised.”
For more information, email Johnny Boggs at firstname.lastname@example.org.