Fluxes of carbon dioxide (CO2) to and from vegetation can be significant on a regional scale. It is therefore important to understand biogenic CO2 fluxes in order to quantify local carbon budgets. However, these fluxes are often difficult to estimate in urban emission studies. This work uses the Solar Induced Fluorescence (SIF) for Modelling Urban biogenic Fluxes (SMUrF) model and the Urban Vegetation Photosynthesis and Respiration Model (UrbanVPRM) to estimate biogenic CO2 fluxes in and around the Greater Toronto and Hamilton Area, the most populous region in Canada. We have made several modifications to both vegetation models to improve the agreement with eddy-covariance flux towers in the region and improve estimates over urban areas. In our presentation, we will describe these improvements and our application of these modified models. In particular, we investigate biogenic CO2 fluxes in the Greenbelt of Ontario; a region surrounding the Greater Toronto and Hamilton Area designed to protect the region's croplands and natural landscape from urban sprawl. We find that this region absorbs significant amounts of CO2 annually and the recently proposed changes to the Greenbelt will result in reduced sequestration by the Greenbelt. We also investigate the amount of CO2 absorbed by vegetation estimated by SMUrF and UrbanVPRM in the city of Toronto, Canada. Lastly, we compare the results from this study to anthropogenic CO2 emission inventories. This work will help constrain biogenic fluxes for use in urban emission studies and may help to inform policy makers and city planners on how vegetation in and around the city affects CO2 concentrations, and thus carbon budgets.

Terrestrial vegetation is known to be an important sink for carbon dioxide (CO2). However, fluxes to and from vegetation are often not accounted for when studying anthropogenic CO2 emissions in urban areas. This project seeks to quantify urban biogenic fluxes in the Greater Toronto and Hamilton Area located in Southern Ontario, Canada. Toronto is Canada’s most populated city but also has a large amount of green-space, covering approximately 13 % of the city. In addition, vegetation is not evenly distributed throughout the region. We therefore expect biogenic fluxes to play an important role in the spatial patterns of CO2 concentrations and the overall local carbon budget. In order to fully understand biogenic fluxes they can be partitioned into the amount of CO2 sequestered via photosynthesis, gross primary productivity (GPP), and the amount respired by vegetation, ecosystem respiration (Reco). Solar induced chlorophyll fluorescence (SIF) measured from space has been shown to be a valuable proxy for photosynthesis and thus can be used to estimate GPP. Vegetation models, including the Urban Vegetation Photosynthesis and Respiration Model (UrbanVPRM) and the SIF for Modelling Urban biogenic Fluxes (SMUrF) model, have also been used to estimate both GPP and Reco In this study we compare modelled and SIF-derived biogenic CO2 fluxes at a 500 m by 500 m resolution, to ground-based flux tower measurements in Southern Ontario to determine how well these methods estimate biogenic CO2 fluxes. This study works towards determining the importance of biogenic fluxes in the Greater Toronto and Hamilton Area. Furthermore, the results of this work may inform policy makers and city planners on how urban vegetation affects CO2 concentrations and patterns within cities.