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Quantification of urban biogenic carbon fluxes using bottom-up inventory and satellite-based model

Published

Author(s)

Joy Winbourne, Hrstiana Stoynova, Ian Smith, Conor Gately, Barry Logan, Jaret Reblin, Andrew Reinmann, David W. Allen, Lucy Hutyra

Abstract

Cities across the globe are taking the lead on climate mitigation action with ambitious goals to reduce carbon dioxide (CO2) emissions. The implementation of effective mitigation policies will require accurate measurements to guide policy decisions and monitor their efficacy. The historic assumption that biogenic CO2 fluxes are known, neutral, or negligible introduces biases of unknown magnitude into the measurement and modeling of CO2 emissions from cities. Here we present a comprehensive CO2 inventory of an urban temperate forest and unmanaged grassland that we compare to modeled estimates of biogenic CO2 fluxes using the Urban-Vegetation Photosynthesis and Respiration Model (Urban-VPRM). We place our biogenic flux estimates in the context of local fossil fuel emissions. We find vegetation to be a net carbon sink of -3.00  1.9 Mg C ha-1 yr-1 in the forest site and -4.86  1.2 Mg C ha-1 in the grassland site during the months of June to August. The Urban-VPRM closely approximates our bottom-up estimates of gross ecosystem exchange but overestimates ecosystem respiration highlighting key areas for model improvement. By placing estimates of biogenic fluxes within the context of total regional fluxes (biogenic + anthropogenic) we demonstrate the seasonal and temporal significance of biogenic fluxes. In the summer afternoons, when air is turbulent and well mixed, there is a net uptake of CO2 by biology that offsets 110% of the emissions from anthropogenic sources in the area. Our study highlights the importance of including seasonal dynamics in biogenic fluxes when planning and testing efficacy of greenhouse gas emission reduction polices, and identifies the Urban-VPRM as a powerful tool for generating city-wide and regional scale estimates of biogenic C fluxes when developing CO2 monitoring programs.
Citation
Science of the Total Environment

Keywords

urban carbon balance, forest fragmentation, VPRM, carbon dioxide, emissions

Citation

Winbourne, J. , Stoynova, H. , Smith, I. , Gately, C. , Logan, B. , Reblin, J. , Reinmann, A. , Allen, D. and Hutyra, L. (2022), Quantification of urban biogenic carbon fluxes using bottom-up inventory and satellite-based model, Science of the Total Environment (Accessed September 25, 2023)
Created January 5, 2022, Updated July 19, 2023