stomatal frequency, stomata, foliar stomatal frequency, stomatal proxy studies, stomatal density, palaeo-stomatal frequency analysis, Australian evergreens, evergreen trees, proxy indicators, atmospheric, carbon dioxide concentration, carbon dioxide, anthropogenic climate change, climate change, climate changes, CO2,  CO2  emissions, proxy-CO2 indicator species, greenhouse gases, morphological, subambient CO2 gradients, Australia, Southern Hemisphere, Victoria, Acacia melanoxylon, Eucalyptus oblique, Acmena smithi