Tower- and chamber-based greenhouse gas flux measurements from Howland Forest, Maine (2012-2018)

Carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) are the greenhouse gases largely responsible for anthropogenic climate change. Natural plant and microbial metabolic processes play a major role in the global atmospheric budget of each. We have been studying ecosystem-atmosphere trace gas exchange at a sub-boreal forest in the northeastern United States for over two decades. Historically our emphasis was on turbulent fluxes of CO₂ and water vapor. In 2012 we embarked on an expanded campaign to also measure CH₄ and N₂O. Here we present continuous tower-based measurements of the ecosystem-atmosphere exchange of CO₂ and CH₄, recorded over the period 2012-2018 and reported at a 30-minute time step. Additionally, we describe a five-year (2012-2016) dataset of chamber-based measurements of soil fluxes of CO₂, CH₄, and N₂O (2013-2016 only), conducted each year from May to November. These data can be used for process studies, for biogeochemical and land surface model validation and benchmarking, and for regional-to-global upscaling and budgeting analyses.