Doctor Diana Backes


Graduated PhD 2023

Thesis Title

The biogeography of plant heat tolerance and vulnerability to heatwaves

Research Project

Urban environments experience pronounced heating compared to rural areas which has been described as the “urban heat island effect” (UHI).  Urban plantings can mitigate this UHI-effect, but in order for this strategy to work we must find plants that can cope with the increased heat and also can deal with harsh growing conditions in cities. These suboptimal growing conditions not only pose problems for growth, but further increases the heat stress on plants.  To be able to select plant species which can survive and thrive in urban ecosystem, it is important to understand how individual species traits can affect the ability to acclimate and survive heat conditions.

In this work I measure thermal tolerance for 24 native tree and shrub species of Australia to determine the traits leading to their resistance to intense heatwaves. Thermal tolerance will be assessed according to the temperature-dependent increase in chlorophyll a fluorescence, to estimate their critical threshold (Tcrit). Additionally, typical leaf traits like LMA and thickness will be collected to determine a possible link between the Tcrit and leaf traits. I will examine native ranges to determine if the climate of origin has a role in conferring higher Tcrit in horticultural plants, and also determine if Tcrit increases during heatwaves. I will also test a range of different heat intensities and frequencies to validate if a higher Tcrit also means a higher thermal tolerance.

This work will further the understanding of plants thermal tolerance and thus will enable selection of the right species to mitigate the UHI and prepare cities for a future climate.


Gauthey A, Backes D, Balland J, Alam I, Maher DT, Cernusak LA, Duke NC, Medlyn BE, Tissue DT, Choat B, (2022) 'The Role of Hydraulic Failure in a Massive Mangrove Die-Off Event', Frontiers in Plant Science, vol.13, Article no.822136

Marchin RM, Backes D, Ossola A, Leishman MR, Tjoelker MG, Ellsworth DS, (2022) 'Extreme heat increases stomatal conductance and drought-induced mortality risk in vulnerable plant species', Global Change Biology, vol.28, no.3, pp 1133-1146


Prof. Mark Tjoelker, Dr. Paul Rymer, Dr. Kristine Crous, Prof. Michelle Leishman, Prof. David Ellsworth