Near Howland, Maine, a partnership between the University of Maine, USDA Forest Service, and Woods Hole Research Center provides a platform for studies of ecosystem-atmosphere CO2 and energy exchange. Instruments visible on the tower include eddy flux instrumentation for measuring net CO2 and energy exchange [supported by DOE's Office of Science/ Biological and Environmental Research (BER)], a dry deposition and meteorological package for studying air quality (supported by NOAA’s Air Resources Laboratory), and a sun photometer for assessing atmospheric aerosols (supported by NASA's Aerosol Robotic Network). Recent results from this and a nearby companion tower have quantified flux measurement uncertainties needed for data-model fusion efforts under the North American Carbon Program (NACP), and have shown that this 140-year-old coniferous forest remains a strong sink for atmospheric CO2. Researchers operate this site with support from DOE. Credit: J. Lee, University of Maine.