Soil pH — Benchmark Detail

Benchmark Value

8.5 pH

Direction: Higher is desirable ↑

Form: Point

Scoring Curve

This curve shows how a field measurement for this indicator would score across all available benchmark forms in this context. The scoring engine uses 3 benchmarks together — the OptimalRange form drives the primary score, while 2 guard(s) constrain the result.

Contributing Benchmarks

OptimalRange Primary Point Guard MaximumOnly Guard

Evidence & Context

The value of pH 8.5 (H₂O), as measured in the study of soil supporting Atriplex vesicaria 41, stands out as the most compelling and defensible benchmark.

Metric Definition:

Soil pH measured in a 1:5 soil:water suspension, representing the acidity or alkalinity of the soil.

Benchmark Definition:

This benchmark represents the natural alkaline soil pH of 8.5 in the Arid Karstic Woodlands & Shrublands, indicating healthy soil conditions supporting key native species.

Justification:

This benchmark is justified by multiple lines of evidence including fundamental chemistry, broad-scale surveys, authoritative reports, and specific field measurements supporting the natural alkaline state of the soil.

Sources (1)

Preview of Soil and Landscape Grid of Australia - esoil.io, accessed July 13, 2025

Soil and Landscape Grid of Australia - esoil.io, accessed July 13, 2025 Government

UPTAKE OF ARSENIC BY NATIVE PLANTS GROWING ON GOLD TAILINGS IN WESTERN AUSTRALIAN RANGELANDS1

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Supporting Sources (6)

Additional references from the underlying research that informed this benchmark.

(PDF) The pH of Australian soils: field results from a national survey - ResearchGate, accessed July 25, 2025,

Contextual Support Journal

Caritat, P. de, & Cooper, M. (2011). The pH of Australian soils: Field results from a national survey. Soil Research, 49, 172-182.

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Arsenic and other elements in saltbush (Atriplex vesicaria) and soils from the goldfields of Western Australia

Direct Evidence Journal

Arsenic and other elements in saltbush (Atriplex vesicaria) and soils from the goldfields of Western Australia

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NVIS Fact sheet MVG 22 – Chenopod shrublands, samphire shrublands and forblands - DCCEEW, accessed July 24, 2025

Contextual Support Journal

A Case for Below-Ground Dispersal? Insights into the Biology, Ecology and Conservation of Blind Cave Spiders in the Genus Troglodiplura (Mygalomorphae: Anamidae) - PubMed Central, accessed July 23, 2025

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Soil Groups of Western Australia - SoilsWest

Contextual Support Journal

Soil Groups of Western Australia - SoilsWest

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Soil organic matter in cropping systems - NSW Department of Primary Industries, accessed July 22, 2025,

Contextual Support Journal

SOIL pH—SOUTH AUSTRALIA

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The pH of Australian soils: field results from a national survey - CSIRO Publishing, accessed July 25, 2025,

Contextual Support Journal

Soil pH Explained - Soil Quality Knowledge Base

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Context

Region Australia
Biome Arid Karstic Woodlands & Shrublands
Land Use Conservation / Protected Natural Areas
Assessment Not Stated
Evidence Type ReferenceCondition

Lifecycle

Status Active
Version 1
Effective From 10 Jun 2026

Notes

This value represents the natural, healthy alkaline state of soils in Australia's Arid Karstic Woodlands & Shrublands, dominated by limestone parent material. It is a direct field measurement from a soil supporting a healthy population of the keystone species Atriplex vesicaria. The ecosystem is defined by its inherent alkalinity, with an optimal range for ecological function identified as pH 8.0 to 8.5 (H₂O). Unlike many other ecosystems, the primary chemical risk is not acidification. The critical detrimental threshold is an upper limit; soil pH values exceeding 8.5 indicate sodicity driven by sodium salts, leading to degraded soil structure and reduced ecosystem function. A pH below the benchmark is not necessarily degraded, but a pH above 8.5 signifies a compromised state. AssessmentContext defaulted to 'Not Stated' because the source document did not state one.

Related Benchmarks

Other benchmarks in the AUS-AKW-CON-SPH family.