Soil phosphorus fractionation and nutrient dynamics along the Cooloola coastal dune chronosequence, southern Queensland, Australia

Publication date: November 2015
Source:Geoderma, Volumes 257–258
Author(s): C.R. Chen , E.Q. Hou , L.M. Condron , G. Bacon , M. Esfandbod , J. Olley , B.L. Turner
The amounts and forms of soil phosphorus (P) follow predictable patterns during long-term pedogenesis, but have rarely been examined along subtropical chronosequences. We quantified changes in soil nutrient stocks, foliar nutrient concentrations, and the chemical forms of soil P along the Cooloola chronosequence, a series of coastal dunes spanning ca. 500,000years of pedogenesis in subtropical Queensland. The total P stock in the upper 30cm of the soil profile declined continuously with soil age, from 229–237kgha⁻¹ on the youngest soils (40years old) to 24–28kgha⁻¹ on the oldest soils (195–>460ka). In contrast, total carbon (C) and nitrogen (N) stocks increased initially along the chronosequence and then declined in the oldest soils. As a consequence, soil N:P ratios increased continually throughout the sequence, from ≤4 on the youngest soils to 27–30 on the oldest soils. This indication of increasing biological P stress and ultimately P limitation was further supported by a decline in foliar P concentrations and increasing foliar N:P ratios of two common plant genera along the chronosequence. Sequential P fractionation revealed that although all forms of P declined during pedogenesis, young soils contained low concentrations of primary mineral P and relatively high concentrations of occluded P associated with secondary minerals, suggesting that the parent sand originated from strongly-weathered continental soils. We conclude that the Cooloola chronosequence is an important example of long-term ecosystem development under a subtropical climate, although the pre-weathered nature of the parent sand indicates that the sequence represents a modification of the Walker and Syers model of P transformations during pedogenesis.