PHOSPHORUS IN FOREST ECOSYSTEMS AT BEENAK, VICTORIA

On the deep granitic krasnozem-type soils at Beenak, Victoria [Australia] wet sclerophyll forest dominated by Eucalyptus regnans occurs on S-facing aspects, dry sclerophyll forest dominated by E. sieberi and E. obliqua occurs on N-facing aspects and there are interrupted ribbons of cool temperate rain forest dominated by Nothofagus cunninghamii along the creeks. The total P and extractable P contents of the soil are higher in the wet sclerophyll forest than in the dry sclerophyll forest; the levels in the rain forest soil overlap those in the other 2. The phosphate-adsorption isotherms suggest that the dry sclerophyll forest soils are capable of fixing P more firmly than the wet sclerophyll forest soils. Bioassays with seedlings of E. regnans and E. sieberi indicate that the wet sclerophyll forest soils are far more fertile than the dry sclerophyll forest soils, that there is a major deficiency of P in the latter and that a burning treatment may not correct the deficiency. The standing crop of 27-yr-old stands, estimated after felling selected trees, was slightly less for E. regnans than for E. sieberi. There was more P in the aboveground standing crop, forest floor and fine roots of the former species. The differences in P status are thus reflected at several levels in the ecosystem. The ways in which the 2 types of ecosystem come to differe in P content despite being developed on fairly uniform parent material, are discussed.