Impact of flooding on the water use of semi-arid riparian eucalypts

Abstract

The water use strategy of Eucalyptus largiflorens (F. Muell.) was investigated in response to flooding on the Chowilla Anabranch, a semi-arid floodplain of the Murray River, South Australia. Water use was measured using the heat pulse technique at six sites that varied in flood duration from 0 to 78 days. Soil chloride, plant water potential and surface root mass were also measured. Suppression of tree water use did not occur during flooding regardless of flood length and site health, suggesting that sufficient oxygen had been available to the trees. Increases in tree water use occurred at some sites after the flood because of increases in water availability due to leaching of salt from the soil profile. The soils with a higher clay content incurred little leaching of salts and therefore little change in tree water availability. In contrast, the sites with more sandy soils encountered greater leaching and greater increases in tree water availability. Despite differing soil type responses, all tree communities investigated showed a reduction in tree water stress in the period after flooding. These findings suggest that flooding in this environment improves the health of Eucalyptus largiflorens in the short-term. The implications of these findings are discussed with regard to the management of the Chowilla Anabranch.