Doctor Varsha Pathare


Graduated PhD 2018

Thesis Title

Varsha Pathare Grass and herb photosynthesis and productivity in a resource-limited Eucalyptus woodland under elevated atmospheric CO2

Research project

About two-thirds of Australia's native forest is woodland (roughly 82 million hectares), thus making them a characteristic feature of the continent. How will these ecosystems change as atmospheric CO2 concentration rises over the coming decades? A growing body of evidence, based on work in other systems, suggest that the ongoing rise in atmospheric CO2 concentration (eCO2) can dramatically affect species composition, structure and productivity of grasslands and possibly also grassy woodlands. Increases in atmospheric CO2 are expected to stimulate CO2 assimilation rates and drive stomatal closure, both of which are ultimately expected to enhance photosynthetic rates and hence total plant biomass in a seasonally water-limited ecosystem. However, some species may respond to eCO2 more than others, due to differences in plant traits and growth strategies such as photosynthetic type, nutrient acquisition patterns, carbon storage and allocation capabilities, root depth and distribution, life form etc. In addition the responses of species will also depend on other important factors like water and nutrient availability, competition etc. Hence, gaining a better insight into the effects of interaction of eCO2 and other environmental factors on the species responses is essential, since these interactions determine the community composition, structure and productivity.

The overall aim of my research is to elucidate the different eco-physiological responses of species to eCO2 and other interacting environmental factors viz. water availability and competition.  The plants under study include six understorey herbaceous species of the seasonally water limited Cumberland plain woodland forest and belonging to three different functional groups. The key objectives of my research are:

  • To elucidate the role of eCO2 and seasonal water availability in the photosynthetic and biomass responses of the understorey species.
  • To study the effect of eCO2, water availability and competition on the resource use strategies of the understorey species
  • To unravel the role of phenotypic plasticity in the response of the native and invasive herbaceous species to eCO2, water availability and competition.

These objectives will be addressed through a comprehensive set of experiments at the Hawkesbury Eucalyptus Free Air Carbon dioxide Enrichment (EucFACE) experiment site and climate controlled glasshouse settings. Outcomes of this research will help in understanding the effect of climate change factors viz. CO2 and water availability on the responses of understorey species of the native endangered Cumberland plain woodland forest ecosystem.


Jiang M, Medlyn BE, Drake JE, Duursma RA, Anderson IC, Barton CVM, Boer MM, Carrillo Y, Castaneda-Gomez L, Collins L, Crous KY, De Kauwe MG, dos Santos BM, Emmerson KM, Facey SL, Gherlenda AN, Gimeno TE, Hasegawa S, Johnson SN, Kannaste A, Macdonald CA, Mahmud K, Moore BD, Nazaries L, Neilson EHJ, Nielsen UN, Niinemets U, Noh NJ, Ochoa-Hueso R, Pathare VS, Pendall E, Pihlblad J, Pineiro J, Powell JR, Power SA, Reich PB, Renchon AA, Riegler M, Rinnan R, Rymer PD, Salomon RL, Singh BK, Smith B, Tjoelker MG, Walker JKM, Wujeska-Klause A, Yang JY, Zaehle S, Ellsworth DS, (2020) 'The fate of carbon in a mature forest under carbon dioxide enrichment', Nature, vol.580, no.7802, pp 227-231

Pathare VS, Crous KY, Cooke J, Creek D, Ghannoum O, Ellsworth DS, (2017) 'Water availability affects seasonal CO2-induced photosynthetic enhancement in herbaceous species in a periodically dry woodland', Global Change Biology, vol.23, no.12, pp 5164-5178


Professor David Ellsworth and Dr Oula Ghannoum