Land cover and latitude affect vegetation phenology determined from solar induced fluorescence across Ontario, Canada

Abstract

• We assess how land cover affects phenology and magnitude of TROPOMI SIF measurements. • SIF magnitude is smaller at high latitudes and differs by land cover. • SIF start of season differs between land cover types. • Annually integrated SIF follows expected patterns of GPP variation. • Assessing phenology from SIF by land cover type allows GPP mapping at 30 m resolution. Land use decisions directly affect the terrestrial carbon balance by changing the quantity and type of vegetation present. However, such consequences are difficult for decisionmakers to account for in environmental impact assessments. Solar induced chlorophyll fluorescence ( SIF ) measured from satellite is strongly related to gross primary productivity of terrestrial vegetation and presents a new source of information from which to assess environmental impacts of land use decisions. We assess the usefulness of SIF measurements in accounting for changes in vegetation primary productivity due to land use change. We use a weighted double logistic regression based on the land cover mixture within SIF measurements from the TROPOspheric Monitoring Instrument (TROPOMI) to separate the phenology of the SIF signal by land cover for the region of Ontario, Canada. We use SIF integrated annually to determine, in relative units, the consequences of land use change on photosynthetic carbon uptake for the study region. Finally, we map GPP at a spatial resolution of 30 m across the province of Ontario using previously reported relationships between SIF and GPP . We find that SIF tracks expected biogeographical patterns of productivity: urban areas exhibit an earlier start of the growing season, lower SIF magnitude and later end of season than natural land cover classes, whereas croplands exhibit a later start of season. Patterns of phenology and SIF magnitude show land cover transitions from Broadleaf Deciduous Forests to croplands or urban environments to have the highest impacts on carbon uptake. Satellite-based SIF measurements are useful in exploring the geographic variation of vegetation productivity and can support inclusion of carbon accounting in environmental assessment at regional scale.