A multiple-lines-of-evidence approach for prioritising environmental watering of wetland and floodplain trees

Long-lived vegetation is a key attribute of lowland river floodplains; yet dieback is increasingly being reported globally, with prior studies identifying salinity, drought and altered flow regimes as key stressors. In the Murray-Darling Basin (Australia), many floodplain/wetland areas have management strategies that aim to maintain the condition of floodplain tree communities. Environmental water delivery is a key tool used to achieve such outcomes. Currently, one of the primary tools for determining the need for environmental water delivery is a qualitative visual assessment of tree crown condition. To advance to more quantitative assessment and understanding of tree condition, we present a suite of techniques ranging from low-cost, rapid visual assessment of tree crown condition to laboratory analysis of components of soil condition and in situ measurement of tree physiology. The aim is to address a number of key knowledge gaps on how to use the linkages between soil water availability <-> tree physiology <-> tree visual condition to quantitatively inform environmental water delivery decisions to meet management objectives. We have developed a multiple-lines-of-evidence management assessment framework that presents a pathway to enable managers to improve prioritisation management actions. Furthermore, increased confidence in predicted outcomes should assist water holders and floodplain managers to optimise timing and maximise the benefits of environmental watering. Application of outcomes of this research will increase the efficiency of environmental water use.