Physiological and Ecological Tolerances of Eucalyptus Incrassata and E. Socialis to Edaphic Factors

The relative distribution of the mallee eucalypts E. incrassata and E. socialis seems to be controlled by slight soil differences, with E. incrassata usually on soils both lower in nutrients and with a higher water-supplying capacity. Seedling monocultures in soils naturally supporting either species or both showed that the two species had closely comparable physiological tolerance to a wide range of macronutrients. In mixed cultures, F. incrassata had a competitive advantage in all soils at optimal water levels, but this was greatly reduced in a drought treatment. E. socialis seems to have superior drought avoidance related to higher root: shoot ratio and possibly to slower growth in competition. Drought susceptibility is shown to be positively correlated with soil fertility. E. incrassata may succumb to drought on the dry, fertile soils carrying E. socialis, whereas E. socialis may be out-competed by E. incrassata on wetter, less fertile sites.