Impact of extreme heatwaves and life-history traits on seed germination responses in Cumberland Plain Woodland native plant species

Abstract

Context The Cumberland Plain Woodland (CPW) is a threatened ecological community that is expected to experience heatwaves of increasing intensity and frequency into the future. Given the central role that temperature plays in regulating seed germination, understanding the impacts of such heatwaves on key germination attributes is vital to identify potential impacts on plant community structure. Aims To determine the impacts of increased heatwave intensity and frequency treatments on seed germination within and across 15 native species of the CPW. We also examined the influence of interspecific variation in life-history traits on germination responses. Methods Seeds were exposed to seven heatwave treatments of increasing intensity and frequency. Life-history trait data were also collected for each species’ dormancy type, fire response traits, life form and seed mass. Key results There was evidence within the study species of a significant effect of heatwave treatment. Germination duration was prolonged for the two most extreme simulated heatwave events. Life-history traits could not explain germination responses after heatwave treatments, however, larger seeded species had quicker germination onset and shorter periods of germination over small-seeded species; and trees had lower proportions of germination than any other life form. Conclusions Increases in heatwave intensity and frequency have an impact on seed germination responses in native species of the CPW. Life-history traits could not explain germination responses across species along the heatwave gradient. Implications Projected increases in heatwave intensity and frequency are likely to impact seed germination, and thus community composition, in species from the CPW.