Dryland soil salinity and seasonal effects on leaf and xylem sap ecophysiological characteristics of native plant species

Abstract

The objective of this 3-year study was to investigate the relationships between soil salinity and ecophysiological responses of C3 and C4 native plant species around Lake Altham and Lake Coyrecup (both are salt lakes in Western Australia), and to evaluate their potential for use in the remediation of salt-affected soils. Three shrubs (Atriplex vesicaria, Tecticornia lepidosperma and T. indica) that grew in highly saline soil of average Na concentration greater than 300 mM had higher leaf δ13C and δ15N ratios. These species also had higher Na-to-K and Na-to-Ca ratios in both their leaves and stem xylem sap, indicating that these species accumulate high amounts of sodium in their tissues. In contrast, tree species Eucalyptus loxophleba, Casuarina obesa and Acacia acuminata grew in soil of average Na concentration of less than 100 mM and had lower values of δ15N, δ13C, Na content, and Na-to-K ratio in their leaves. These species also had lower xylem Na-to-K and Na-to-Ca ratios. Seasonal effects were observed in leaf total N content, leaf Na, xylem sap Na-to-K ratio and xylem sap Na-to-Ca ratio. Strong and significant positive correlations (r > 0.75; P < 0.01) were observed between soil Na concentration and ecophysiological responses, such as leaf Na contents, leaf δ15N, xylem sap Na, xylem Na-to-K ratio and xylem Na-to-Ca ratio. Overall, Atr. vesicaria, T. lepidosperma, T. indica and Santalum acuminatum are good candidates for remediation of highly saline soils.