Inundation history shapes tree condition, mortality, and structural dynamics in black box (Eucalyptus largiflorens) woodlands on a regulated floodplain

Floodplain forests and woodlands worldwide are increasingly threatened by altered hydrological regimes, where changes in inundation timing, frequency, duration, and extent degrade ecosystem function and resilience. Understanding how long-term inundation history influences the condition, structure, and regeneration of floodplain woodland is essential for effective management. To address this knowledge gap, this study examined relationships between inundation history, tree condition, mortality, stand structure, and regeneration in black box ( Eucalyptus largiflorens , IUCN Vulnerable) woodlands across the Lower Murrumbidgee floodplain in the Murray-Darling Basin, Australia. Inundation metrics derived from long-term remote sensing data were related to field measurements using Bayesian modelling approaches. Tree condition and mortality were closely associated with inundation history, with more frequent recent inundation events linked to improved canopy condition and infrequent inundation associated with increased mortality risk. Stand structure responses included increased tree density and greater stem diameter variability at more frequently inundated sites, indicating episodic recruitment and multi-cohort stand development. Mean tree size was only weakly related to inundation history. Regeneration was poor, patchy, and weakly related to inundation metrics, suggesting recruitment is influenced by local conditions and seedling survival. These findings indicate that floodplain woodland responses operate over contrasting temporal scales, with canopy condition reflecting recent inundation, while mortality and stand structure reflect long-term inundation history. Black box woodland condition and persistence are supported by inundation regimes that more closely reflect historical flow conditions through periodic flooding and the avoidance of prolonged dry phases.