Eight Mile Lake Research Watershed, Carbon in Permafrost Experimental Heating Research (CiPEHR): Half-hourly growing season, chamber-based, CO2 flux data, 2009-2018

FIELD: Carbon dioxide fluxes (net ecosystem carbon exchange, NEE) were measured from May through September using 24 automated dynamics flux chambers, located at the CiPEHR project. Carbon dioxide concentrations were measured using a LiCOR-820 infrared gas analyzer and data were stored to a Campbell Scientific CR1000 data logger. Detailed information on the flux system and data processing can be found in Natali et al. 2011 (GCB). The 24 flux chambers were rotated weekly between 66 experimental plots (48 CiPEHR plots and, since 2011, 18 DryPEHR plots located within the CiPEHR footprint). LAB: Data were filtered to remove erroneous fluxes due to equipment failure or environmental conditions. Gaps in NEE were filled using parameters obtained by regressing measured NEE against PAR through a non-rectangular hyperbola (RStudio, using nlsLM from minpacklm package). Ecosystem respiration (Reco) was measured based on night-time NEE values (PAR<5umol/m2/s) and Reco was modeled using an exponential relationship with soil temperature (5cm depth in 2009, 10cm thereafter)(RStudio, using nls base function). Gross primary productivity (GPP) was estimated as the difference between NEE and Reco. Additive half-hourly NEE values represent the daily carbon exchange by the tundra ecosystem where negative values are net source of carbon and positive are net sinks. Environmental variable used for gap-filling can be found in CiPEHR meteorological data and soil moisture/temperature data files posted to BNZ LTER.