Howland Forest 25-year dataset - Multi-decadal carbon cycle measurements indicate resistance to external drivers of change at the Howland Forest AmeriFlux site

The Howland Forest, located in central Maine, is an unmanaged, mixed-age forest characterized by canopy trees aged 100-200 years. Eddy flux measurements have been collected at this site since 1996. The forest was first inventoried by NASA in 1989. This data publication contains data files used to produce the figures for a publication that looked at how multi-decadal carbon cycle measurements indicated resistance to external drivers of change at the Howland Forest AmeriFlux site. Data include 1) half-hourly data obtained by eddy covariance measurements (1/1/1996 – 12/31/2020) with missing values filled via routines in the R package “Reddyproc” and used to estimate annual and monthly net ecosystem production (NEP = -net ecosystem exchange), gross primary production (GPP), and ecosystem respiration (Reco); 2) remeasurements of individual tree diameters in 44 inventory plots surrounding the tower (2001-2017); 3) diameter reconstruction of cored trees on an inventory “megaplot” adjacent to the tower (1989-2015); 4) interpolated soil respiration measurements obtained from manual and automated soil respiration systems (1996-2016); 5) other measurements of carbon flows or stores in the Howland forest including litterfall (1998-2018) and woody respiration; 6) repeated measurements of the leaf area index (LAI) from 1998-2020, and phenology of the forest canopy (1990-2020); and 7) other measurements of forest growth conditions including nutrient deposition (2000-2019), weighted ozone concentration (1995-2018), and atmospheric CO₂ concentration (2012-2020).The purpose of this study was to determine if the forest is a net carbon source or sink and how this might change in the future.For more information about this study and these data see Hollinger et al. (2021). These data were published on 06/07/2021. On 03/04/2024, minor metadata updates were made.