Figure 2. Long-term observations of ozone and PPFD at Borden Research Station.

(a) Four-year seasonal average of ozone concentrations measured at different heights in the canopy (key indicates the averaged months of the year with interquartile ranges); (b) PPFD above the canopy (33 m) and near the surface (1.5 m) during 2013; (c) fraction of above canopy PPFD transmitted to the ground during 2013.