Long-term studies of post-fire reproduction in an Australian shrubland and woodland

Abstract

Identifying appropriate fire-return times is critical for management of temperate southern Australia’s fire-prone shrublands and woodlands. The time to first flowering and peak flowering are useful attributes for understanding how species and vegetation will respond to different fire intervals. Using a plant fire-response trait framework, we investigate patterns of reproduction in south-western Australian kwongan and woodland after prescribed fires with a 30-year longitudinal study, with the aim of identifying appropriate fire intervals. Modelling of post-fire flowering responses of species and aggregating responses into plant functional types showed substantial differences in the time after fire to first and peak flowering. Tests of hypotheses of flowering patterns after fire with different fire-response traits showed that (1) resprouters flower sooner than recruits of non-resprouters, (2) serotinous non-resprouters reach first and peak flowering later than do non-resprouters with soil-stored seed, (3) species in taller strata reach first and peak flowering later than those in lower strata and (4) geophytes flower earlier than other resprouters that lose their aboveground biomass in fire. The most fire interval-sensitive non-resprouting serotinous species take 15–20 years in kwongan to reach peak flowering and in Allocasuarina woodland 25–30 years, providing a working hypothesis for minimum fire intervals in the plant communities under investigation. Our study illustrates the value of long-term ecological studies for informing biodiversity management.