The Response of Six Eucalyptus Species and Casuarina obesa to the Combined Effect of Salinity and Waterlogging

Abstract

Seedlings of Eucalyptus camaldulensis, E. comitae-vallis, E. kondininensis, E. lesouefii, E. platycorys, E. spathulata and Casuarina obesa were grown in a glasshouse under non-saline drained, saline drained, non-saline waterlogged, and saline waterlogged conditions for 3 months. Measurements were taken of seedling height, seedling survival and the concentration of Na, K, Ca, Mg and Cl in plant tissues. Production of specialised roots containing aerenchyma in E. camaldulensis and C. obesa enabled these species to tolerate non-saline waterlogged conditions. Saline, but freely drained conditions reduced seedling growth for all species but only E. kondininensis recorded seedling deaths. C. obesa was the species most tolerant of saline waterlogged conditions with no seedling deaths and a lower reduction in growth compared to the Eucalyptus species. Exclusion of Na and Cl, together with the production of specialised roots by C. obesa are suggested as the probable factors relating to the high seedling tolerance in saline waterlogging. The species with highest tolerance to non-saline waterlogging were more tolerant of saline waterlogged conditions. The importance of this result for evaluating trees to be used in the rehabilitation of secondary salinised land in Australia is discussed.