Howland Research Forest is an AmeriFlux core site located in central Maine. The site was established in 1987 through a partnership between the University of Maine and International Paper. Collaborations between the USDA Forest Service, US Department of Energy, NASA, and the University of Maine have maintained an active research program focused on carbon and nutrient cycling. In 2007, the 220-hectare site was purchased and permanently protected by Northeast Wilderness Trust.

The site maintains three eddy flux towers; two towers (the “main” and “west” towers) are located in a mature spruce–hemlock forest approximately 800 meters apart. Howland has the second longest running flux record in the United States, dating back to 1996 (the longest belonging to Harvard Forest). These 20 years of data provide a time series long enough for robust analyses of relationships between CO2 flux and various environmental variables.

The Howland Research Forest is located in the transition zone between the eastern deciduous forest and the boreal forest in eastern North America. A mature multi-aged spruce–hemlock forest comprises approximately 170 of the 220 hectares owned by Northeast Wilderness Trust. The forest is dominated by red spruce (Picea rubens) and eastern hemlock (Tsuga canadensis), consisting of approximately 90% conifer, and 10% deciduous tree species.

Howland Forest location map and long term forest inventory plots