Informing environmental flow management of the Hattah Lakes floodplain plant community with multi-species modelling approaches

Demonstrating the effectiveness of environmental watering to maintain ecosystem health is becoming increasingly important, particularly in semiarid floodplain ecosystems. We evaluated the effects of a large-scale environmental flow event on a semi-arid floodplain lakeside plant assemblage for meeting the management goal of increasing water-dependent taxa and functional groups. We developed a multi-taxon Bayesian hierarchical model to describe temporal and small-scale spatial patterns in taxonomic occurrences. We then examined community summary metrics to evaluate patterns for the entire floodplain lakes system, the scale most relevant to management. Overall, in a system dominated by terrestrial dry plant taxa, 52.9% of terrestrial damp plant taxa showed a short-term increase in occurrence in response to the environmental flow, which translated into similar responses in some functional groups. However, nearly half of the plant taxa that increased then demonstrated a decline by 18-months after the flow event. Our community summary metrics captured these general results; however, they were disproportionately influenced by a few abundant plant taxa. These results highlight the advantages of multi-taxon models for interpreting flow responses and developing effective environmental flow management strategies, because they can be used to summarize community responses, while preserving important taxon-specific information. In semi-arid systems, where river regulation and climate change have reduced the frequency of flood events, the ability to deliver environmental flows during protracted periods of drought may be a policy option to restore or maintain the natural floodplain vegetation assemblage and prevents the transition to dryland taxa