The incidence of low phosphorus soils in Australia
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Low phosphorus (P) soils have been described as a widespread characteristic of the Australian continent and associated with sclerophyll leaf traits. In that context we ask: what proportion of the continent is low-P and how much does this vary between regions?
9234 locations sampled for soil total P from the Australian National Site Soil Data Collation were analysed. In order to make some adjustment for uneven spatial sampling we area-weighted the data using subregions from the Interim Bioregionalisation of Australia.
Topsoil total P concentrations ≤100 mg kg−1 were widespread, but not a majority of the continent (estimated 25 %). The western Monsoon Tropics (65 %), southwestern Australia (50 %), and southeast South Australia (38 %) were estimated to have larger fractions of the sampled landscape ≤100 mg kg−1 than eastern Australia (13.5 %), but not a lower range of values. Total P values across the continent included a large fraction (33 %) in the range 101–250 mg kg−1.
Continent-wide soil P levels low enough to favour long leaf lifespans for nutrient conservation and a variety of sclerophyll traits were widespread. It is time to move away from the qualitative dichotomies between low- and high-P that have characterised discussion of Australian vegetation, to a more quantitative view.
KeywordsAustralia Frequency distributions Low phosphorus soils Regions
We thank: State agencies including Department of Land Resource Management, Northern Territory of Australia; Victoria - Department of Economic Development, Jobs, Transport and Resources; New South Wales – Office of Environment and Heritage; Queensland - Department of Science, Information Technology, Innovation and the Arts; and all contributors to the NSSDC for data access. We also thank CSIRO staff including Raphael Viscarra-Rossell, Elisabeth Bui, and Ross Searle for discussions in relation to the SLGA, and Ross Searle for providing the NSSDC data; David Warton (UNSW) for assistance with statistics; Will Cornwell (UNSW) for assistance with R-code for data cleaning, filtering and synthesis; and Ian Wright (MQU) and three anonymous reviewers for providing valuable comments and suggestions. The project was supported by Macquarie University and the Australian Research Council through an Australian Laureate Fellowship to MW. RK was supported by a Postdoctoral Research Fellowship at Macquarie University.
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