Survival and growth responses of a number of Australian tree species planted on a saline site in tropical north Australia.
Abstract
The survival and growth of 15 species and provenances of Australian trees planted on a saline site in dry tropical Queensland was examined. The species included were one provenance each of Acacia aulacocarpa, Casuarina cristata, C. cunninghamiana, C. equisetifolia, C. glauca, Eucalyptus alba, E. camaldulensis, E. tereticornis, E. tessellaris, Melaleuca bracteata, M. leucadendra [M. leucadendron] and M. quinquenervia, and 3 provenances of A. auriculiformis. The study site was divided between high, moderate and low salinity subsites. A randomized complete block design was used for each subsite. Tree survival and height were measured at 3 and 24 months. Measurements of diameter at breast height, tree crown size, branch number per tree, growth form, fork numbers per tree, and leaf length, width and thickness were conducted at 24 months. Soil salinity was measured at 3, 12 and 24 months. These data were statistically analysed to examine the effect of salinity on tree survival and growth and the differences in response between taxa. The survival and growth varied with salinity and species. Trees grown on the high salinity subsite had the lowest survival and poorest growth rate. C. cunninghamiana, C. glauca and E. camaldulensis achieved the highest survival, fastest growth rate and best growth form. A. aulacocarpa showed the poorest performance. It is suggested that species selection for utilization of saline sites should be made according to salinity, species salt tolerance and management objectives. Plant height and diameter, crown size and branch number are important characteristics which indicate salt tolerance. Those species with an ability to maintain a relatively large crown and a high number of branches when subjected to salinity are most likely to be highly tolerant to salt.