Soil pH — Benchmark Detail

Benchmark Value

5 pH

Thresholds: Lower: 5, Upper: —

Direction: Higher is desirable ↑

Form: LowerThreshold

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 8 benchmarks together — the OptimalRange form drives the primary score, while 7 guard(s) constrain the result.

Contributing Benchmarks

OptimalRange Primary Point Guard MinimumOnly Guard OptimalRange Guard OptimalRange Guard LowerThreshold Guard UpperThreshold Guard OptimalRange Guard

Evidence & Context

Therefore, the Lower Critical Threshold for maintaining essential ecological function and preventing a shift into a persistent degraded state in this biome is defined as pH(CaCl2) 5.0.

Metric Definition:

Soil pH measured in a slurry of soil and 0.01 M calcium chloride (pHCaCl2)

Benchmark Definition:

This benchmark defines the lower critical soil pH threshold below which essential ecological functions are compromised due to aluminium toxicity in Temperate Grassy Woodlands.

Justification:

The point at which soluble aluminium begins to reach toxic concentrations—around pHCaCl2 5.0—represents a fundamental tipping point for ecosystem function. Below this value, the soil environment becomes actively hostile to many key native species.

Sources (1)

Preview of (PDF) Temperate Woodland Conservation and Management. - ResearchGate

(PDF) Temperate Woodland Conservation and Management. - ResearchGate GreyLiterature

(PDF) Determining reference conditions for management and ..., accessed August 11, 2025,

View Source

Supporting Sources (10)

Additional references from the underlying research that informed this benchmark.

(PDF) Determining reference conditions for management and ..., accessed August 5, 2025,

Contextual Support

(PDF) Impacts of tree invasion on floristic composition of subtropical grasslands on the Bunya Mountains, Australia - ResearchGate, accessed May 19, 2025

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

Contextual Support Journal

Soil pH | Environment, land and water - Queensland Government, accessed August 28, 2025,

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Agriculture Victoria. (2024). Soil acidity.

Contextual Support

Soil acidity | Soil | Farm management - Agriculture Victoria, accessed August 28, 2025

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Australia's forests – overview - DAFF

Contextual Support

AUSTRALIA'S STATE OF THE FORESTS REPORT - DAFF, accessed August 28, 2025,

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Growing with Acid Soils - ecobotanica, accessed August 11, 2025,

Contextual Support

Growing with Acid Soils - ecobotanica, accessed August 11, 2025,

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Preview of Identifying ecological barriers to restoration in temperate grassy woodlands: soil changes associated with different degradation states - ResearchGate, accessed August 5, 2025,

Identifying ecological barriers to restoration in temperate grassy woodlands: soil changes associated with different degradation states - ResearchGate, accessed August 5, 2025,

Contextual Support Journal

(PDF) Identifying ecological barriers to restoration in temperate grassy woodlands: soil changes associated with different degradation states - ResearchGate, accessed August 4, 2025,

View Source

Soil condition 2024 | NSW State of the Environment, accessed July 7, 2025,

Contextual Support Government

Soil pH | Environment, land and water - Queensland Government, accessed August 11, 2025,

View Source

Soil nutrient critical limits | MBFP | More Beef from Pastures - MLA, accessed May 13, 2025,

Contextual Support GreyLiterature

Understanding soil tests for pastures | Soil | Farm management ..., accessed July 17, 2025,

View Source

Soil pH - Wikipedia, accessed July 25, 2025,

Contextual Support GreyLiterature

Soil pH - Wikipedia, accessed August 11, 2025,

View Source

Soil Research - CSIRO PUBLISHING, accessed July 16, 2025,

Contextual Support Journal

Soil Research - CSIRO PUBLISHING, accessed August 11, 2025,

View Source

Context

Region Australia
Biome Temperate Grassy Woodlands & Plains
Land Use Conservation / Protected Natural Areas
Assessment Conservation Target
Vegetation Woodland
Evidence Type DegradationThreshold

Lifecycle

Status Active
Version 1
Effective From 24 Mar 2026

Notes

Below this level, soil becomes significantly compromised due to aluminium toxicity, which acts as a powerful ecological filter, preventing the growth of many key native species and locking the ecosystem in a degraded state. No upper detrimental threshold — higher values are always better up to natural saturation.

Related Benchmarks

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