Salinity effects on tree growth, root distribution and transpiration of Casuarina cunninghamiana and Eucalyptus camaldulensis planted on a saline site in tropical north Australia

Abstract

A study was carried out to compare tree response to soil salinity of Casuarina cunninghamiana and Eucalyptus camaldulensis grown on a saline site in tropical north Australia. The site was divided into low- (< 0.6 dS m −1), moderate- (0.6–1.1 dS m −1) and high- (> 1.1 dS m −1) salinity subsites on which seedlings were planted in a randomised complete block design. Tree response was examined with regard to survival, height, DBH (diameter at breast (1.4 m) height), root growth, transpiration rate and plant chemical components at ages 24–36 months. Both species had a similarly high survival rate. Compared with C. cunninghamiana, E. camaldulensis trees were taller with greater DBH at both low and moderate salinity, and transpired more water in both summer and winter. C. cunninghamiana possessed a shallow root system with the bulk of the lateral roots in the upper 12 cm of soil, while E. camaldulensis had a deep root system with the majority of the lateral roots located in the upper 28 cm. C. cunninghamiana appeared to use less water than E. camaldulensis in both summer and winter. It is suggested that although both C. cunninghamiana and E. camaldulensis were salt-tolerant, E. camaldulensis is preferable for reclamation of salt-affected land, particularly when the salinity is moderate or low.