Calibrations_Southern

Vegetation in the Southern Hemisphere tends to have a higher proportion of woody dicots that are evergreen compared to vegetation in the Northern Hemisphere. This is because in the Southern Hemisphere most land masses that support woody vegetation lie in lower latitudes. This also means that because evergreens tend to be found in warmer climates they also tend to display leaf characters associated with those warmer temperatures and thus exhibit rather different leaf form/climate relationships. Added to this, Southern Hemisphere land masses tend to be more genetically isolated as evidenced by the endemic floras of Australia and New Zealand. In the case of New Zealand this isolation has given rise to a unique leaf form/climate relationship so, for example, we see no relationship between the presence of marginal teeth and temperature (Yang et al., 2015).

The degree to which the modern Southern Hemisphere relationships between leaf form and climate are relevant to interpreting past climates is time dependant, so great care has to be exercised when choosing a calibration. For example when New Zealand is connected to the bulk of Gondwana, including South America, in the mid Cretaceous New Zealand leaves can be analysed in CLAMP using Physg3brAZ, which is a Northern Hemisphere calibration. This validity fades away over time as New Zealand tracks across ever lower latitudes and even becomes partially submerged in the Oligocene. This means that Northern Hemisphere calibrations may not be the best option for younger Cenozoic fossil assemblages. The new two stage analytical process should help in making such decisions.


	Map of the PhysgSH calibration sites (blue), and global sites (grey).

The published calibration for the southern hemisphere contains the 90 sites shown here.

Calibrations - Southern Hemisphere

Overview

Climate data

Physg3br

Physg3ar

PhysgAsia2

Southern H.

Global

Climate Variable Definitions