Undergrowth and Overgrowth

Article excerpt

Southern Appalachia is a global hot spot for diversity of salamanders, mushrooms, and my specialty, temperate trees. There are more species of trees here than almost anywhere else in Earth's temperate zones. I tell my students in Athens, Georgia, that the fastest way to visit Harvard, or at least to see the hardwoods of Harvaz"d Forest, including sugar maple, yellow birch, and hemlock, is to take a two-hour drive to the Coweeta Long-Term Ecological Research site in Otto, North Carolina. And the very highest elevation forests in the Smoky Mountains are classified as spruce-fir boreal forests. Boreal forests in North Carolina!

Yet I did not get to enjoy those glorious ecosystems during my time as a doctoral student at Duke University in the mid-1990s. Instead I worked in a Piedmont loblolly pine plantation in the center of North [see photograph at center] , which was chock full of ticks, chiggers, and poison ivy. That's where the Duke Free-Air CO9 Enrichment (FACE) experiment was set up. The physicists and engineers in charge wanted a smooth, homogeneous canopy of same-age pines - and the associated more-regular air currents - to better control and study atmospheric carbon dioxide (CO-,) levels.

As a lowly graduate student in a facility full of famous professors, lowly also as one of the shortest ple there and one of the few females, I got to research the "leftover stuff": not the big trees, not the soils, but woody plants growing in the understory that nobody else cared about. Juvenile trees, shrubs, and woody lines including poison ivy - that was me. "Forests of the Future" is how I dignified my subjects. Unfortunately, the white-tailed deer that had surged in the northeastern and central United States over the last half century arrived at the Duke FACE right after I began my study. They ate my dissertation! Millions of dollars for a CO2 experiment, and the deer were winning.

When I finally received permission to cage the deer out of my plots, I found that the understory trees grew roughly 8 percent faster with increased CO-, (which was pumped in by PVC piping), though this strongly depended on the species. Normally slower-growing trees, such as sugar maple and black cherry, were the ones that got a big boost from more CO2; already fastgrowing species such as oaks, pines, sweet gum, and tulip poplar did not show any change in growth. …