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Abstract

This study investigates the availability of phosphorus and the forms of bound soil phosphorus present in three rain forest stands in north eastern Queensland. The soil types investigated differed significantly with respect to total soil phosphorus, with fertility decreasing in soils from basaltic to alluvial to granitic origin. At all sites only a small proportion of total phosphorus was available for plant uptake, with most being bound in organic matter and inorganic forms. A pot experiment was set up with Alphitonia petriei which was grown in soil collected from each of the three sites. After four months there was a significant difference in the dry weights, with plants showing stunted growth in the granitic soil collected from the site with the lower available phosphorus concentrations. These plants also had significantly higher root to shoot ratios and lower intracellular concentrations of phosphorus. Root phosphatase activity was greater for plants grown in soil low in available phosphorus.