Vines Swamp Southern Forests

| Tue Jul. 17, 2007 8:47 PM EDT

A new study in the southeastern U.S. suggests that increased vine growth is changing bottomland hardwood forests. Researchers from Ohio State University charting the growth of grapevines, trumpet vines, poison ivy, and Virginia creeper in two South Carolina forests found as much as a 10-fold increase in just two decades. As the vines increase, the density of small trees decreases, probably because most vines use adhesive roots or tendrils to climb trees. The reasons for the shift aren't yet understood, but rising CO2 levels may be to blame &mdash since other studies suggest that vines such as poison ivy benefit more than trees from higher CO2 levels. . . Think of that itchy future: the Republican rash. JULIA WHITTY