Increase In Creeping Vines Changes Southern US Forests

A new study of bottomland hardwood forests in the southeastern United States suggests that the increased growth of vines may change the landscape of these forests. Researchers charting the growth of vines in two forests in South Carolina found up to a 10-fold increase in the number of vines in just two decades. Vines commonly found in both forests include grapevines, trumpet vine, poison ivy and Virginia creeper. Most of the vines use adhesive roots or tendrils to climb trees.
The patterns observed in the south add to a growing number of studies that found similar patterns in temperate and tropical forests, said Bruce Allen, the study's lead author and a recent doctoral graduate of Ohio State University's School of Environment and Natural Resources.

"Collectively, we're talking about an increase of more than 500 vine stems in 27 acres of forest area that we studied," he said. "And all of the growth is within the last 10 to 20 years. Old photographs from the sites indicate there may have been fewer vines historically.

"There are now so many vines that they're starting to change the makeup of the forest," he continued. "It appears that as the number of vines increase, the density of small trees decreases at a fairly uniform rate."

Although the specific reasons for this shift aren't fully understood, Allen and his colleagues say possible mechanisms include increases in carbon dioxide concentrations, which have been shown to increase vine growth more than tree growth.

"Many vines thrive on elevated levels of carbon dioxide," he said. "Several studies suggest that vines like poison ivy benefit more than other plants from higher CO2 levels."...

(I've read that doctors are seeing an increase in poison ivy patients.)