The phenology of Eucalyptus camaldulensis (Dehnh, 1832) and Eucalyptus coolabah (Blakely & Jacobs, 1934) in the northern Murray–Darling Basin and implications for recruitment on floodplains

Context Published evidence suggests recruitment of floodplain trees is declining in the northern Murray–Darling Basin (MDB) and that this is linked to river flow. Aims We investigated the reproductive phenology of Eucalyptus camaldulensis and Eucalyptus coolabah to better understand tree reproductive cycles and the influence of rainfall and flow on seed production. Methods We surveyed phenological events (bud, flower and fruit production) over 6 years, at nine sites along the Condamine–Balonne River and examined correlations between these events and meteorological parameters. Key results For both species, event timing was consistent across sites and years and event relative abundance scores were different between years. Bud abundance was correlated with rainfall, flooding and warming temperatures and E. coolabah produced additional bud crops after floods. Conclusions The timing of events did not differ significantly from published results for the southern MDB. Rainfall, river flows and flooding in spring resulted in more abundant bud crops in E. camaldulensis and E. coolabah, and subsequently more abundant fruit crops. Fruit dehiscence coincided with summer–autumn flooding, which provides seed for germination. Genetic and physiological factors may also influence the observed pattern. Implications These results will inform water planning in Queensland, Commonwealth Environmental Water Holder watering actions and long-term watering plans in the northern MDB.