Ozone impacts on tropical forest productivity 

<p>Tropospheric ozone (O₃) reduces plant productivity by entering leaves, generating reactive oxygen species and causing oxidative stress which in turn increases respiration, decreases photosynthesis, plant growth, biomass accumulation, and consequently reduces the land carbon sink. Tropical forests are potentially most vulnerable to future O₃ scenarios given their high productivity, generally high stomatal conductance and environmental conditions conducive to O₃ uptake (eg precursor emissions during biomass burning).</p> <p>Here we present the first comprehensive set of measurements of O₃ effects on plant physiology and biomass accumulation in tropical forests. We exposed twelve tropical tree species to elevated O₃ concentrations in Open Top Chambers (OTCs) based at the James Cook University O₃ experimental facility in Cairns, Australia, from which we generate O₃ dose-response functions for each species. We test the importance of Leaf Mass per unit Area (LMA) as an indicator of O₃ sensitivity.</p> <p>We use these relationships to parameterize the global land-surface model JULES, and apply the model over the pan-tropical region using contemporary near-surface O₃ concentration fields. For the first time we quantify the impact of O₃ on contemporary tropical productivity.</p>