Resilience and adaptive cycles in water-dependent ecosystems: Can panarchy explain trajectories of change among floodplain trees?

Riverine floodplains are complex dynamic environments with pronounced spatial heterogeneity. They are ideal landscapes to test components of resilience thinking. These adaptive ecosystems are disturbed, naturally, through periodic hydrological connections that respond via complex and variable trajectories. The concept of adaptive cycles (panarchy) portray the dynamic response of ecosystems as a cyclic process with four phases: exploitation, conservation, release and reorganisation. We test this concept as an appropriate framework to extend our understanding of dynamic changes in floodplain vegetation in response to flooding history. We use a remotely sensed >30-year NDVI time series for Eucalyptus camaldulensis and E. largiflorens and relate it to flooding frequency within two large floodplain complexes within the Murray-Darling Basin, Australia. Multiple thresholds were identified in all NDVI data sets; the timing of each period between thresholds varies among flooding classes. This reflects a complex response and substantial changes in the duration of floodplain vegetation within each phase of the adaptive cycle. Thus, the character of the adaptive cycle for floodplain vegetation NDVI differs in time and space. This change in the adaptive cycle is suggested as an indicator of a potential flip to another less productive regime state.