In May 2015, scores of scientists from dozens of research institutions descended on a patch of forest in central North Carolina, taking samples of everything from ants and mites to other microbes – samples they hope will offer a glimpse into the future of forest ecosystems.
This flurry of data collection represents the largest and most robust warming experiment conducted in a forest ecosystem. The project is supported by the U.S. Geological Survey and the Department of the Interior’s Southeast Climate Science Center, based at North Carolina State University (NCSU).
The heart of the experiment is a collection of so-called warming chambers – a dozen octagonal rooms, 5 meters in diameter, scattered throughout Duke Forest, across Durham, Orange, and Alamance counties in NC. The rooms had neither roofs nor floors, and were ringed with clear, plastic ductwork that pumped warm air into each chamber. Three of the chambers were kept at the same temperature as the surrounding forest. The other nine chambers were warmer, with internal temperatures that ranged from 1.5° Celsius (~35° Fahrenheit) to 5.5° Celsius (~ 42° Fahrenheit) higher than the ambient temperature. The North Carolina warming chambers had been running since January 2010 until they were taken down in May 2015 and have a sister site in Massachusetts’s Harvard Forest with a similar collection of warming chambers.
Insects, Trees, and Soils Respond
“We know that ants are an important part of forest ecosystems, and we found that warming has a significant impact on ant diversity in forests,” says Clint Penick, a postdoctoral researcher at NCSU who works at the site. “Some ant species populations decline dramatically, while other ant populations grow. One ant that fared poorly at higher temperatures is the winnow ant (Aphaenogaster rudis) – a common ant in eastern U.S. forests that plays a crucial role in seed dispersal. A species of acrobat ant, on the other hand, is becoming much more common.” Others still, such as the invasive needle ant, seem to thrive regardless of the temperature.