Understanding Factors Contributing to Biospheric CO2 Fluxes in Los Angeles, CA

Urban areas are known hotspots of fossil fuel carbon dioxide (CO₂) emissions, however, the influence of the biosphere on carbon fluxes in urban areas is not well understood and represents a source of uncertainty in urban carbon budgets. Furthermore, the impacts of severe drought on these biospheric fluxes, both from managed lands and unmanaged lands surrounding urban areas, are a source of uncertainty. The Los Angeles basin is a spatially complex urban area with relatively dense measurement capabilities that provides an opportunity to better quantify urban CO₂ emissions estimates and associated uncertainties. Understanding the major factors that influence biospheric and anthropogenic CO₂ fluxes in Los Angeles will help constrain urban carbon emissions estimates, giving a more accurate estimate of the global carbon budget.

We will present measurements from in situ eddy covariance towers located in natural vegetation sites across a climate gradient in southern California, which show differences in CO₂ fluxes, net ecosystem exchange, respiration, evapotranspiration and soil surface temperatures. In this study, we will discuss the flux tower results during drought versus wet periods. In order to broaden the spatial scale of our study, we will also discuss the potential for use of the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) surface reflectance data for detecting and classifying vegetation in urban Los Angeles and the surrounding regions to improve our understanding of the distribution of managed versus unmanaged lands in the Los Angeles basin. Our approach will combine a vegetative/pervious/impervious mask with Multiple Endmember Spectral Mixture Analysis (MESMA) to classify and constrain the distribution of managed vs. unmanaged vegetation in Los Angeles. We will also initial discuss results from the Vegetation Photosynthesis and Respiration Model (VPRM) which will be used to help constrain natural vegetative CO₂ fluxes in Los Angeles. The aim of this study is to improve our understanding of the magnitude and drivers of biospheric CO₂ fluxes and carbon ecosystem dynamics in complex urban areas by combining surface monitor data and remote sensing measurements.