Flood regimes driving vegetation and bird community transitions in semiarid floodplain woodlands

AbstractWater resource development in many parts of the world has resulted in serious reductions in the frequency, extent, and duration with which floodplain woodlands are inundated, resulting in significant habitat change and loss of productivity. Yet few studies have attempted to assess the effects of different flood regimes upon floodplain vegetation and fauna communities together, particularly during the terrestrial phase. We use new space‐for‐time substitution data from south‐eastern Australia to describe the nature of Eucalyptus largiflorens floodplain woodland communities under different flood regimes, from which inferences may be made about the consequences of water management decisions. We explore the hypothesis that differences in flood regime drive dissimilarities in vegetation structure and condition as well as variation in woodland bird abundance. Overall, insufficient flooding was associated with degradation of floodplain woodland condition and structure, as well as shifts in the relative abundance of key woodland bird groups. The results suggest that changes in flooding frequency are associated with significant shifts in site character and ultimately transitions in community composition, even within the same broad vegetation type. Importantly, these transitions are the result of interactions between water availability, vegetation changes, fauna habitat preferences, and interspecific interference competition. In addition, they indicate the influence of altered flood regimes upon terrestrial fauna of floodplain ecosystems rather than just aquatic components—a link that is relatively neglected by both scientists and managers to‐date. Such transitions and links have far‐reaching implications for ecosystem function at multiple scales and for how floodplains are understood, valued, and managed.