Effectiveness of artificial watering of a semi-arid saline wetland for managing riparian vegetation health

摘要

Eucalyptus camaldulensis Denh. (River Red Gum) and E. largiflorens F.Muell. (Black Box), the dominant riparian tree species that fringe the wetlands of the lower River Murray in south-eastern Australia, are in severe decline. Artificial watering has been used as an emergency management measure in an effort to save these significant ecological assets. This study quantified the extent of lateral recharge and the tree response to artificial watering in a semi-arid saline floodplain wetland. The extent of the vegetation response was linked to the extent of groundwater freshening from bank recharge, which was controlled by floodplain hydraulic conductivity. A two- to five-fold increase in plant water potential and a three- to six-fold increase in tree water use were observed in the 3 to 4 months after watering. Artificial watering is an effective floodplain management tool to preserve significant ecological assets during periods of low flow. It can be used to manage one-third of E. camaldulensis communities on the Chowilla floodplain that grow within the estimated extent of bank recharge from wetland watering. However, water balance calculations indicate that the water stored as bank recharge would be discharged as evapotranspiration within three years, which means that regular artificial watering is required during periods of low flow to maintain high-value floodplain sites.