Survival and Growth of Seedlings of Three Sclerophyll Species at High Levels of Phosphorus and Nitrogen

Abstract

Seedlings of Banksia serrata, Acacia suaveolens and Eucalyptus pilularis were grown in sand culture for 3-4 months at four levels of phosphorus (0, 5, 50, and 100 ppm) and three of nitrogen (0, 25 and 250 ppm) applied gradually in all combinations. B.serrata died at high phosphorus-high nitrogen levels, A.suaveolens died with high phosphorus irrespective of the nitrogen level, and E. pilularis did not survive high phosphorus or high nitrogen levels. There were differences between species in their growth responses to increasing levels of phosphorus and nitrogen. Dry weights of seedlings were greatest at P₅N₂₅ for B.serrata, at P₅N₂₅₀ for A.suaveolens, and at P₅N₂₅₀ for E.pilularis. Shoot phosphorus concentrations greater than 1% were directly associated with 'toxicity' and death of A.suaveolens seedlings only, and not of the other two species.

The species differ in the weights and nutrient contents of their seeds, and this is discussed in relation to the different responses obtained. Growth of sclerophyll species on areas subject to disturbance (e.g. sand-mining) will be determined in large part by the levels of phosphorus and nitrogen applied and the rate at which nutrients are leached from the rooting zone.