Screening Eucalyptus clones for salt tolerance

Agroforestry plantations offer environmentally acceptable strategies for the reuse of saline drainage waters. Tree species suitable for use in such systems must be selected for survival and sustained growth under highly saline conditions. In this screening trial, four clones of Eucalyptus camaldulensis Dehn. (4543, 4544, 4573, and 4590) and one clone of E. rudis Endl. (4501) were grown in greenhouse sand cultures irrigated with sodium sulfate-dominated waters. Solution compositions were prepared to simulate saline drainage waters typically found in the San Joaquin Valley of California, Electrical conductivities of the solutions ranged from 2 to 28 dS.m(-1). Treatments were replicated three times. All plants survived and were harvested after 7 weeks under saline treatment. Plant height was measured weekly and shoot biomass was determined at final harvest. The salinity levels that resulted in a 50% reduction in biomass production (C-50) were 16.4 (4573), 17.1 (4543), 17.7 (4544), 29.0 (4590), and 30.0 dS.m(-1) (4501). Over the range of salinities from 4 to 20 dS.m(-1), clones 4501, 4590, and 4573 generally maintained higher relative growth rates (RGR) than did clones 4544 and 4543. However, at the highest salinity, RGRs of clones 4501, 4544, and 4573 were significantly greater than those of clones 4543 and 4590, Assessed on the basis of biomass production, clones 4501 (E. rudis) and 4590 (E. camaldulensis) showed exceptional potential for use in agroforestry systems where the saline drainage waters are sodium sulfate-dominated.