Ecophysiological mechanisms underpinning resilience to climate change in the Northern Jarrah Forest (Western Australia)

Nathaniel S. Anderson

Southwestern Australia has experienced a consistent warming and drying trend since the 1970s. Alongside changes in mean climate, extreme events such as droughts and heat waves have also increased in frequency and are linked to forest canopy collapse and larger, more severe bushfires. The increasing frequency of drought, heat waves, and wildfires associated with climate change highlight the importance of understanding forest recovery after disturbances. A key area of uncertainty is how climate disturbances such as drought and heatwaves interact with other events such as wildfire. Plant leaves link atmospheric processes to forest water availability, contribute to fine fuel dynamics, and have impacts on bushfire severity through their live foliar moisture content. These make leaves an ideal medium for studying forest recovery from climate change related disturbances. This study investigated the ecophysiological functioning of Eucalyptus marginata in stands of forest recovering from a drought/heatwave in 2010/2011 and the Waroona-Yarloop wildfire in 2016. Pre-dawn leaf water potential, stomatal conductance, chlorophyll fluorescence, change in leaf temperature, specific leaf area, live foliar moisture content, and Huber values provided the basis for comparison between plots affected by the drought/heatwave event, the wildfire, and a combination of these disturbances. Measurements were taken in the summer and winter to provide low and high values (respectively) for ecophysiological functioning. The high probability drought, high severity fire plot had the lowest pre-dawn leaf water potentials, and reduced stomatal conductance. A number of trees adjacent to this plot died or had canopy contractions between the summer and winter measurements. The combination of observed tree death and low pre-dawn leaf water potentials suggests that for E. marginata, the interplay of drought and fire is pushing vulnerable portions of the forest beyond their threshold of survival.

Ecophysiological mechanisms underpinning resilience to climate change in the Northern Jarrah Forest (Western Australia)

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