Available phosphorus forms in forest soils and their possible ecological significance

For a range of northern N.S.W. forest soils typical of Australian east coast forests, both inorganic and organic P have been determined on sequential soil extracts. Organic P was present in each extract, and in most extracts was a high proportion of the total P, regardless of soil type. Using the sum of the P concentrations in the most neutral extracts as an index of available P, the organic component ranged from 352 to 88% of the total available P. Soil parent material appeared to exert the strongest influence on both soil total P and on the proportion of organic P/total P which ranged from 26% to 81%. The results have been discussed in relation to soluble organic P and its availability in forest ecosystems. The soil organic P results have been discussed in relation to P availability and supply within the forest ecosystem.