Riparian forests are structured and maintained by their hydrology, and woody perennials ensure their longevity in these dynamic habitats by adjusting allocations to growth, survival and reproduction in response to the disturbance regime. However, growth and regeneration responses of woody vegetation to water dynamics are complex and require further investigation to inform restoration planning and counter global wetland forest degradation.
To yield insights into the regeneration ecology of three riparian keystone species, 298 individuals of Eucalyptus camphora, Melaleuca squarrosa and Leptospermum lanigerum were surveyed randomly across a flooding gradient in an area of 1.7 km2 within the Yellingbo Nature Conservation Reserve, Australia. Characteristics of growth shape (DBH, height, number of stems, inclination), and evidence of vegetative (epicormic growth) and sexual reproduction (buds, flowers, cones) were recorded. A hydrological model built in TUFLOW enabled the identification of local flooding history for each tree and examination of the impact of flooding regime on tree architecture, condition and reproduction (mode and intensity).
Extended periods of inundation compromise plant growth and result in individuals with a higher tendency to multi-stemmed growth and stem-leaning, while dryer locations favour taller individuals and single-stemmed growth. In general, trees experiencing frequent inundation displayed increased resprouting whereas indicators of sexual reproduction were more even across the hydrologic gradient.
These findings highlight the central role of the hydrological regime in determining tree growth architecture and therefore shaping wetland forest structure. Hence, restoring and maintaining appropriate flooding regimes is imperative to sustaining ecosystem integrity and function such as habitat provision.