Climate drying reduces serotinous seedbanks and threatens persistence in two fire-killed shrubs

Background Mediterranean-type ecosystems (MTEs) are experiencing declining rainfall, increasing temperature, and shifting fire regimes as climate changes. While changes in fire regimes and post-fire recruitment are widely reported, evidence for changing plant demographic rates is limited. Aims We hypothesised increased time to maturity and decreased serotinous seed stores available for post-fire recruitment due to declining rainfall over recent decades for two fire-killed serotinous shrubs of south-east Australian MTEs, Hakea decurrens and Banksia ornata. Methods Fruit and cone production for populations across time since fire chronosequences were measured in the same regions in the 1990s and in 2017. Key results Estimated time to 50% maturity increased from 3–15 years and 6–15 years for H. decurrens and B. ornata, respectively, while estimated canopy seed stores were 90% and 50% lower in 2017 than in the 1990s. Conclusions Delayed reproductive maturity and decreased total seed stores were significantly related to decreasing rainfall received by 2017 populations over their lifetimes (5–17% less than for stands in the 1990s). Implications Shifts in inter-fire rates of seed production and storage, combined with changes to fire regimes and post-fire recruitment conditions due to climate change may already threaten the persistence of some species.