Researchers Seek a Sneak Peek Into the Future of Forests
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.
For both ants and trees, the researchers have been able to identify key features of the species that succeed with warming and those that fail; in general, what they see in the chambers matches what is going on in urban heat islands across the country – as well as ecological changes stemming from temperature changes in the Southeast over the past hundred years. The researchers also learned that the impact of climate change appears to be very different in regions such as North Carolina versus cooler regions such as Massachusetts. This indicates that, at least for the species the team has studied so far, increases in temperature are likely to have a bigger ecological impact in areas that were warmer to begin with.
So Much More to Learn
Now, thanks to support from Interior’s Southeast Climate Science Center, the team has reached out to scholars from around the world to help them study the full suite of organisms present in each chamber. And dozens of researchers have answered the call.
“As we got closer to the end-date for the warming chamber site, we invited a slew of scientists interested in diversity questions to work on collecting samples from the chambers,” says Lauren Nichols, an NCSU researcher who has worked on the project from the beginning. “Collectively, it should give us a good overview of how shifts in temperature may change a forest – from the microbial level up.”
Already, researchers from nine universities are also looking at different aspects of soil core samples to see how microbial communities have changed over time at different temperatures.
“And because samples of plants, soils and insects are being saved and curated like museum specimens, the samples can and will be studied by people not yet involved in the project,” says Rob Dunn, a professor of biology at NCSU and one of the primary investigators on the warming chambers project.
This will allow people from all walks of life, including formal researchers, to engage in studying the forests of the future for many years to come. “When it is all said and done, these chambers may be not only the biggest warming experiment in a forest yet, but also the most intensive and collaborative study of any patch of forest,” Dunn says. Dunn’s research partners are Nate Sanders of the University of Copenhagen, Aaron Ellison of Harvard Forest and Nick Gotelli of the University of Vermont.
“We’ll be seeing discoveries come out of this work for years to come,” ant researcher Penick says. And, says Dunn, “We hope to still see new collaborators signing up to help us to study the experiment, because even as the chambers come down we are saving everything we can, from dirt to leaves that in the future others can study what we fail to pay attention to now. The more people that help us to see, the more light we will shine on the warmer future, a future that is coming whether or not we spend the time trying to understand.”
