Abstract

Mature and senescent foliage were sampled from 15 species of Eucalyptus, covering three subgenera, Symphyomyrtus, Monocalyptus and Corymbia, under non-limiting availability of water and nutrients (effluent-irrigated plantation). Concentrations of total phosphorus in mature foliage were relatively high for Eucalyptus (range 1.6–3.1 mg g^–1), inorganic phosphorus accounting for 60–79% of total phosphorus. Foliar concentrations of total and inorganic phosphorus in Monocalyptus were about twice as much as in Symphyomyrtus. Concentrations of nitrogen did not differ amongst subgenera. About 50% of leaf nitrogen was resorbed during senescence. In contrast, about 11–24% of phosphorus was resorbed, of which about 48–77% was derived from hydrolysis of organic phosphorus. There were no significant differences amongst subgenera in resorption of either nitrogen or phosphorus. Despite significant variability in nutritional characteristics within subgenera, we conclude that Monocalyptus has a greater capacity to accumulate foliar phosphorus (as inorganic phosphorus) than Symphyomyrtus, but that Symphyomyrtus has a greater phosphorus-use efficiency (ratio of growth to foliar phosphorus). Foliar inorganic phosphorus appears to be easily manipulated by nutrient amendment whereas nitrogen is highly resistant. Resorption efficiency of phosphorus (proportion of total phosphorus resorbed) is decreased under high availability of soil phosphorus.