Abstract

Abstract. Past efforts to synthesize and quantify the magnitude and change in carbon dioxide (CO2) fluxes in terrestrial ecosystems across the rapidly warming Arctic–boreal zone (ABZ) have provided valuable information but were limited in their geographical and temporal coverage. Furthermore, these efforts have been based on data aggregated over varying time periods, often with only minimal site ancillary data, thus limiting their potential to be used in large-scale carbon budget assessments. To bridge these gaps, we developed a standardized monthly database of Arctic–boreal CO2 fluxes (ABCflux) that aggregates in situ measurements of terrestrial net ecosystem CO2 exchange and its derived partitioned component fluxes: gross primary productivity and ecosystem respiration. The data span from 1989 to 2020 with over 70 supporting variables that describe key site conditions (e.g., vegetation and disturbance type), micrometeorological and environmental measurements (e.g., air and soil temperatures), and flux measurement techniques. Here, we describe these variables, the spatial and temporal distribution of observations, the main strengths and limitations of the database, and the potential research opportunities it enables. In total, ABCflux includes 244 sites and 6309 monthly observations; 136 sites and 2217 monthly observations represent tundra, and 108 sites and 4092 observations represent the boreal biome. The database includes fluxes estimated with chamber (19 % of the monthly observations), snow diffusion (3 %) and eddy covariance (78 %) techniques. The largest number of observations were collected during the climatological summer (June–August; 32 %), and fewer observations were available for autumn (September–October; 25 %), winter (December–February; 18 %), and spring (March–May; 25 %). ABCflux can be used in a wide array of empirical, remote sensing and modeling studies to improve understanding of the regional and temporal variability in CO2 fluxes and to better estimate the terrestrial ABZ CO2 budget. ABCflux is openly and freely available online (Virkkala et al., 2021b, https://doi.org/10.3334/ORNLDAAC/1934).

Highlights

  • The Arctic–boreal zone (ABZ), comprising the northern tundra and boreal biomes, stores approximately half the global soil organic carbon pool (Hugelius et al, 2014; Tarnocai et al, 2009; Mishra et al, 2021)

  • Our goal is to build upon past synthesis efforts and compile a new database of Arctic–boreal CO2 fluxes (ABCflux version 1) that combines eddy covariance, chamber, and diffusion data at monthly timescales with supporting environmental information to help facilitate large-scale assessments of the ABZ carbon cycle

  • This paper provides a general description of the ABCflux database by characterizing the data sources and database structure (Sect. 2), as well as describing the characteristics of the database

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Summary

Introduction

The Arctic–boreal zone (ABZ), comprising the northern tundra and boreal biomes, stores approximately half the global soil organic carbon pool (Hugelius et al, 2014; Tarnocai et al, 2009; Mishra et al, 2021) As indicated by this large carbon reservoir, the ABZ has acted as a carbon sink over the past millennia due to the cold climate and slow decomposition rates (Siewert et al, 2015; Hugelius et al, 2020; Gorham, 1991). Automated and manual chamber techniques measure NEE at fine spatial scales (< 1 m2) and in small-statured ecosystems, common in the tundra, where the chambers can fit over the whole plant community (Järveoja et al, 2018; López-Blanco et al, 2017). The eddy covariance technique has been used globally for over three decades and chamber and diffusion techniques for even longer

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