Doctor Yan-Shih Lin
Graduated PhD 2012
How will Eucalyptus tree species respond to global climate change?: [CO2] responses and seasonal temperature adjustment
Plants must tolerate temperature fluctuations on a yearly basis in order to function efficiently. However, due to greenhouse gases increasing, surface temperatures are warming and more extreme temperatures are expected in the future, which may dramatically alter current species distribution. It is hypothesised that species originally from warmer regions and more likely to be exposure to a wide range of temperatures show higher photosynthetic temperature optima or high temperature tolerance than species from cooler regions. This hypothesis was tested using leaf gas exchange and chlorophyll a fluorescence measurements of six Eucalyptus species at the Hawkesbury Forest Experiment (HFE) site. Temperature responses of six species were investigated in a common environment. Measurements for each species at three temperature levels (18, 25 and 32°C in winter and 25, 32 and 36°C in spring and summer) were used to evaluate temperature responses. There were clear seasonal temperature adjustment responses among six species. Particularly, E. dunnii from a geographically narrow and cooler region of Qld. had a lower temperature optimum for photosynthesis than other five species.
The interaction between atmospheric [CO2] levels and temperature responses were investigated using leaf gas exchange and chlorophyll a fluorescence measurements of Eucalyptus saligna in the whole tree chamber experiment at the HFE. Measurements for each species at three temperature levels (25, 32 and 36°C in spring and summer) along with photosynthesis models were used to evaluate temperature responses. The dataset suggests that there was less sensitivity to high temperature in terms of photosynthetic parameters in elevated CO2 (Vcmax and Jmax) than those under ambient [CO2] treatment.
Research Project Supervisor
Professor David Ellsworth
Duursma RA, Barton CVM, Lin Y-S, Medlyn BE, Eamus D, Tissue DT, Ellsworth DS, McMurtrie RE, (2014) 'The peaked response of transpiration rate to vapour pressure deficit in field conditions can be explained by the temperature optimum of photosynthesis', Agricultural and Forest Meteorology, vol.189-190, pp 2-10
Crous KY, Quentin AG, Lin Y-S, Medlyn BE, Williams DG, Barton CVM, Ellsworth DS, (2013) 'Photosynthesis of temperate Eucalyptus globulus trees outside their native range has limited adjustment to elevated CO2 and climate warming', Global Change Biology, vol.19, no.12, pp 3790-3807
Héroult A, Lin Y-S, Bourne A, Medlyn BE, Ellsworth DS, (2013) 'Optimal stomatal conductance in relation to photosynthesis in climatically contrasting Eucalyptus species under drought', Plant, Cell and Environment, vol.36, no.2, pp 262-274
Lin YS, Medlyn BE, Ellsworth DS, (2012) 'Temperature responses of leaf net photosynthesis: the role of component processes', Tree Physiology, vol.32, no.2, pp 219-231