Transpiration and water relations of evergreen shrub species on an artificial landform for mine waste storage versus an adjacent natural site in semi-arid Western Australia

In water-limited environments, transpiration may minimize deep drainage on engineered covers used for hazardous waste disposal. However, comparative studies investigating plant ecophysiology and water use on engineered covers and natural sites are limited. Water use patterns and plant-water relations of evergreen shrubs were monitored in semi-arid Western Australia to (1) investigate the response of plant-water relations and shrub transpiration to soil moisture changes and (2) quantify stand transpiration and its contribution to the water balance. The shrubs showed conservative (<20cmhr-1) but persistent transpiration. Differential response to rainfall pulses was evident among species; sap velocity for Acacia bivenosa and Acacia inaequilatera increased by 20-103% (p<0·05) after rainfall events exceeding 15mm but declined rapidly to pre-storm levels. On the contrary, sap velocity for Acacia pruinocarpa increased by 61% after large pulse (83 and 127mm) associated with cyclonic activity and remained high (10-15cmhr-1) thereafter. These transpiration patterns suggested contrasting rooting patterns among the species. Sap velocity was low (<20mmhr-1) for all species, even when moisture was readily available. Annual shrub transpiration was 65 (engineered cover) and 81mm (natural shrubland), accounting for 16 and 20% of annual rainfall (395mm). Stand characteristics, plant ecophysiology and shrub transpiration were comparable for both sites, demonstrating the importance of using topsoil as a growth medium and seedbank in revegetation. Overall, the study provided insights on ecophysiological behaviour of artificial landforms, and the first empirical evidence suggesting rapid and successful restoration of mined lands can be achieved under semi-arid conditions. © 2013 John Wiley & Sons, Ltd.