Soil pH
Benchmark Value
Scoring Curve
This curve shows how a field measurement for this indicator would score across all available benchmark forms in this context.
Evidence & Context
"As the pH (in CaCl2) falls below 4.2, P ions will precipitate with Al and Fe and will adsorb onto Al and Fe oxides, which become increasingly soluble as the soil becomes more acidic (Hinsinger 2001; Hazelton and Murphy 2007)."
Topsoil pH threshold in calcium chloride extract below which phosphorus precipitation with iron and aluminum restricts biological availability.
Degradation threshold below which severe acidification impairs phosphorus availability and native plant recruitment.
Identifies a precise chemical boundary in highly weathered Australian soils where severe acidification triggers nutrient lockup, posing a persistent ecological barrier to woodland recovery.
Sources (1)
Fitzgerald, J. K. (2007). The Soil of Abandoned Farmland, Cumberland Plain Woodland and Restored Areas. PhD Thesis, Western Sydney University.
View SourceSupporting Sources (5)
Additional references from the underlying research that informed this benchmark.
Eldridge, D. J., Benham, M., Singh, B. K., & Delgado-Baquerizo, M. (2021). Ecosystem Properties in Urban Areas Vary with Habitat Type and Settlement Age. Plant and Soil, 462, 115–128.
View SourceMac Nally, R., McIntyre, S., & Bennett, A. F. (2014). Coarse Woody Debris Carbon Pools in Biologically Diverse Grassy Woodlands of Southeastern Australia. Journal of Environmental Quality, 43(6), 2055–2064.
View SourceMallen-Cooper, M., Nakagawa, S., & Eldridge, D. J. (2019). Foraging Pits of a Reintroduced Ecosystem Engineer, the Eastern Bettong, Have Divergent Effects on Soil Chemistry in Sub-humid Temperate Woodland. PLOS ONE, 14(8), e0220953.
View SourceProber, S. M., & Lunt, I. D. (2009). Restoration of Themeda australis Swards Suppresses Soil Nitrate and Enhances Ecological Resistance to Invasion by Exotic Annuals. Biological Invasions, 11(2), 171–181.
View SourceHasegawa, S., Crous, K. Y., & Macdonald, C. A. (2015). Elevated Carbon Dioxide Increases Soil Nitrogen and Phosphorus Availability in a Phosphorus-Limited Eucalyptus Woodland. Global Change Biology, 21(11), 4165–4177.
View Source