Understanding forest tree responses to climate warming and heatwaves is important for predicting changes in tree species diversity, forest C uptake, and vegetation–climate interactions. Yet, tree species differences in heatwave tolerance and their plasticity to growth temperature remain poorly understood. In this study, populations of four Eucalyptus species, two with large range sizes and two with comparatively small range sizes, were grown under two temperature treatments (cool and warm) before being exposed to an equivalent experimental heatwave. We tested whether the species with large and small range sizes differed in heatwave tolerance, and whether trees grown under warmer temperatures were more tolerant of heatwave conditions than trees grown under cooler temperatures. Visible heatwave damage was more common and severe in the species with small rather than large range sizes. In general, species that showed less tissue damage maintained higher stomatal conductance, lower leaf temperatures, larger increases in isoprene emissions, and less photosynthetic inhibition than species that showed more damage. Species exhibiting more severe visible damage had larger increases in heat shock proteins (HSPs) and respiratory thermotolerance (T max ). Thus, across species, increases in HSPs and T max were positively correlated, but inversely related to increases in isoprene emissions. Integration of leaf gas-exchange, isoprene emissions, proteomics, and respiratory thermotolerance measurements provided new insight into mechanisms underlying variability in tree species heatwave tolerance. Importantly, warm-grown seedlings were, surprisingly, more susceptible to heatwave damage than cool-grown seedlings, which could be associated with reduced enzyme concentrations in leaves. We conclude that species with restricted range sizes, along with trees growing under climate warming, may be more vulnerable to heatwaves of the future.
Bibliographical noteFunding Information:
Australian Research Council, Grant/Award Number: DP140103415; Australian Science Industry Endowment Fund, Grant/Award Number: RP04–122; Hawkesbury Institute for the Environment, Western Sydney University
The authors have no conflicts of interest to declare. This research was supported by the Australian Research Council (Discovery, DP140103415), the Science Industry Endowment Fund (SIEF project code RP04–122), and Hawkesbury Institute for the Environment, Western Sydney University. We thank Danielle Creek for assistance with leaf water potential measurements.
© 2019 John Wiley & Sons Ltd
- heat shock proteins (HSPs)
- heat stress
- thermal acclimation