Displaying items by tag: ornl environmental sciences division

The ForWarn vegetation tracking tool shows areas of red where extreme disturbance to the forest canopy occurred in Western North Carolina, East Tennessee and southern Virginia as a result of Hurricane Helene in late September 2024.  Jitendra Kumar/ORNL, U.S. Dept. of Energy

Information will help timber gleaning, fire-hazard mitigation

Stephanie Seay is a senior science writer and communications specialist at Oak Ridge National Laboratory.

OAK RIDGE — A visualization tool that tracks changes to the nation’s forests in near-real time is helping resource managers pinpoint areas with the most damage from Hurricane Helene in the Southeast.

The ForWarn visualization tool was co-developed by Oak Ridge National Laboratory with the U.S. Forest Service. The tool captures and analyzes satellite imagery to track impacts such as storms, wildfire and pests on forests across the nation. 

When staff with the Forest Service’s Eastern Forest Environmental Threat Assessment Center in Asheville, North Carolina, were unable to work in the immediate aftermath of Helene due to utility outages, the ORNL-hosted ForWarn system continued monitoring the storm’s impact and providing reports. ForWarn indicated areas of severe disturbance to the forest canopy that were later confirmed by aerial photography. 

“ForWarn helps quickly identify areas that may need remediation such as timber harvesting or prescribed burns as piles of felled trees dry out and potentially pose wildfire hazards,” said ORNL’s Jitendra Kumar.

Here is some evidence of tree browning and “flagging” caused by the recent appearance of Brood-10 cicadas earlier this summer.  Courtesy Oak Ridge National Laboratory 

Tree “flagging” is a lingering sign of the 17-year cicadas’ brief time on Earth

(Alexandra DeMarco is an intern in ORNL’s media relations group.)

On the road leading to the U.S. Department of Energy’s Oak Ridge National Laboratory, drivers may notice that many of the green trees lining the entrance to the lab are dappled with brown leaves. At first glance, the sight isn’t extraordinary, as deciduous tree leaves turn hues of oranges and browns before falling to the ground each autumn.

Yet, just weeks past the summer solstice, this phenomenon is out of place and is in fact evidence of another natural occurrence: cicada “flagging.”

This spring, Brood X cicadas emerged from the ground after 17 years and swarmed across the eastern United States, leaving a trail of exoskeletons and echoes of mating calls. Cicadas emerge in such large quantities to withstand predation and successfully maintain their populations, and trees actually play a key role in their life cycle.

A male cicada attracts a female through a mating call, the sound responsible for cicadas’ shrill hum. After the two mate, the female cicada uses a sharp tubular organ called an ovipositor to slit the bark and split the sapwood of young tree branches to deposit her eggs there. These incisions, however, damage a tree’s vascular system and can cause stalks beyond the incision to die and wither, leaving behind twigs with brown leaves that resemble flags dangling from the trees.

The eggs then grow into nymphs that make their way to below ground. An oft-repeated misconception is that they’ll stay dormant for 17 years. Actually, during that time, they go through 5 life stages while feeding on the xylem (tree sap) of roots. This may further weaken saplings that were heavily infested with cicadas.