For more than 5 years, we have been performing eddy covariance measurements on an extensive green roof in Berlin to investigate the energy balance of the green roof as well as the CO2 exchange. Our results on CO2 uptake were recently published in JGR Biogeosciences (open access - https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020JG005879
Konopka, J., Heusinger, J. and Weber, S., 2021. Extensive Urban Green Roof Shows Consistent Annual Net Uptake of Carbon as Documented by 5 Years of Eddy-Covariance Flux Measurements. Journal of Geophysical Research: Biogeosciences, 126(2): e2020JG005879.