Soil pH — Benchmark Detail - Nature Index

Benchmark Value

No specific value — see range

Range: 4.5 to 5.5 pH

Optimal Range: 4.5 to 5.5

Direction: Lower is desirable ↓

Form: OptimalRange

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 15 benchmarks together — the OptimalRange form drives the primary score, while 14 guard(s) constrain the result.

Contributing Benchmarks

OptimalRange Primary OptimalRange Guard MaximumOnly Guard MaximumOnly Guard OptimalRange Guard MinimumOnly Guard MaximumOnly Guard MinimumOnly Guard MaximumOnly Guard OptimalRange Guard Point Guard MinimumOnly Guard MaximumOnly Guard OptimalRange Guard MinimumOnly Guard

Evidence & Context

The proposed reference value is an observed range of pH 4.5 – 5.5 (1:5 soil:water suspension), with a strong central tendency indicating that many healthy alpine communities and soil types average around pH 4.7 – 5.2 (1:5 soil:water suspension).

Metric Definition:

Soil pH measured in a 1:5 soil:water suspension, representing the acidity or alkalinity of the soil in Australian alpine and subalpine protected natural areas.

Benchmark Definition:

This benchmark defines the natural soil pH range for healthy alpine and subalpine soils in protected areas of Australia, measured by the 1:5 soil:water suspension method.

Justification:

This benchmark is based on multiple peer-reviewed studies and government reports showing consistent acidic pH values in undisturbed or well-managed alpine ecosystems, with a clearly specified measurement method.

Sources (1)

Preview of An introduction to the soils of the Australian Alps

An introduction to the soils of the Australian Alps Journal

Impacts of Road Disturbance on Soil Properties and on Exotic Plant ...

Supporting Sources (18)

Additional references from the underlying research that informed this benchmark.

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

(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.

Preview of Application of the Soil Security Concept to Two Contrasting Soil Landscape Systems—Implications for Soil Capability and Sustainable Land Management - MDPI

Application of the Soil Security Concept to Two Contrasting Soil Landscape Systems—Implications for Soil Capability and Sustainable Land Management - MDPI

Contextual Support Journal

Arctic, Antarctic, and Alpine Research. (2005). Recovery of Alpine Vegetation from Grazing and Drought. 8

Preview of Australian Government / ALA. (2023). Conservation actions for Australian alpine and sub-alpine peatlands. 25

Australian Government / ALA. (2023). Conservation actions for Australian alpine and sub-alpine peatlands. 25

Contextual Support Journal

Australian Government / ALA. (2023). Conservation actions for Australian alpine and sub-alpine peatlands. 25

Preview of Australian Journal of Ecology. (2006). Vegetation of an alkaline pan - acidic peat mosaic in the Hardwood River Valley, Tasmania. 17

Australian Journal of Ecology. (2006). Vegetation of an alkaline pan - acidic peat mosaic in the Hardwood River Valley, Tasmania. 17

Contextual Support Government

Australian Journal of Ecology. (2006). Vegetation of an alkaline pan - acidic peat mosaic in the Hardwood River Valley, Tasmania. 17

Preview of Biogeosciences. (2025). Alkalinisation significantly disrupts peatland functioning. 16

Biogeosciences. (2025). Alkalinisation significantly disrupts peatland functioning. 16

Contextual Support Journal

Australian Alps National Parks. (2013). Soils of the Australian Alps (Fact Sheet). 9

Preview of Climate change impacts on our soils - AdaptNSW

Climate change impacts on our soils - AdaptNSW

Contextual Support Journal

Climate change impacts on our soils - AdaptNSW

Preview of Effects of simulated acidification on soil basic chemical properties (2024/2025)

Effects of simulated acidification on soil basic chemical properties (2024/2025)

Contextual Support Journal

NCBI / PMC. (2024/2025). Effect of simulated acidification on soil basic chemical properties. PMC11994667. 20

Preview of estuaries.dwer.wa.gov.au, accessed May 12, 2025

estuaries.dwer.wa.gov.au, accessed May 12, 2025

Contextual Support Journal

Turner, B. L., et al. (2014). Soil organic phosphorus speciation in Australian alpine and sub-alpine soils. Journal of Soils and Sediments.

Preview of Frontiers in Plant Science. (2013). Aluminum (Al) cation Al3+ is highly rhizotoxic and is a major stress factor to plants on acid soils. 5

Frontiers in Plant Science. (2013). Aluminum (Al) cation Al3+ is highly rhizotoxic and is a major stress factor to plants on acid soils. 5

Contextual Support Journal

Frontiers in Plant Science. (2013). Aluminum (Al) cation Al3+ is highly rhizotoxic and is a major stress factor to plants on acid soils. 5

Preview of Full article: Impacts of Road Disturbance on Soil Properties and on Exotic Plant Occurrence in Subalpine Areas of the Australian Alps - Taylor & Francis Online, accessed May 28, 2025

Full article: Impacts of Road Disturbance on Soil Properties and on Exotic Plant Occurrence in Subalpine Areas of the Australian Alps - Taylor & Francis Online, accessed May 28, 2025

Direct Evidence Journal

www.nrc.nsw.gov.au, accessed on May 27, 2025

Preview of Gully erosion assessment and control guide - Local Land Services, accessed on May 29, 2025,

Gully erosion assessment and control guide - Local Land Services, accessed on May 29, 2025,

Contextual Support Government

www.climatechange.environment.nsw.gov.au

Preview of NCBI / PMC. (2021). Ecosystem index score for the reference, treated and untreated zones in Alpine National Park. PMC8367960. 11

NCBI / PMC. (2021). Ecosystem index score for the reference, treated and untreated zones in Alpine National Park. PMC8367960. 11

Contextual Support GreyLiterature

NCBI / PMC. (2021). Ecosystem index score for the reference, treated and untreated zones in Alpine National Park. PMC8367960. 11

Preview of Pastures and acid soils - NSW Government

Pastures and acid soils - NSW Government

Contextual Support Journal

What do you see and when? What could this indicate? What test can I do to confirm? - MLA

Preview of Scherrer, P., & Pickering, C. M. (2006). Rehabilitation of a Walking Track in Kosciuszko National Park. Arctic, Antarctic, and Alpine Research. 28

Scherrer, P., & Pickering, C. M. (2006). Rehabilitation of a Walking Track in Kosciuszko National Park. Arctic, Antarctic, and Alpine Research. 28

Contextual Support Journal

Freiburg University. (2012). Plant and soil P determine functional attributes of subalpine Australian plants. 13

Preview of Soil and Landscape Grid National Soil Attribute Maps - pH (Water) (3" resolution) - Release 1

Soil and Landscape Grid National Soil Attribute Maps - pH (Water) (3" resolution) - Release 1

Contextual Support Government

CSIRO. (2021). Soil and Landscape Grid National Soil Attribute Maps - pH - CaCl2. 26

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

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,

Preview of theaustralianalpsnationalparks.org, accessed on May 29, 2025,

theaustralianalpsnationalparks.org, accessed on May 29, 2025,

Direct Evidence Journal

Soil Conservation in Alpine Catchments - The Kosciuszko Huts Association, accessed August 17, 2025,

Preview of Victorian Resources Online. Soils of Suggan Buggan/Buchan. 18

Victorian Resources Online. Soils of Suggan Buggan/Buchan. 18

Contextual Support Journal

Victorian Resources Online. Soils of Suggan Buggan/Buchan. 18

Context

Region Australia
Biome Alpine and Subalpine Complex
Land Use Conservation / Protected Natural Areas
Assessment Pristine Reference
Evidence Type ReferenceCondition

Lifecycle

Status Active
Version 1
Effective From 3 Jun 2026

Notes

The range 4.5–5.5 pH reflects natural acidic conditions supporting high environmental health and biodiversity, encompassing mean pH values from key vegetation formations and soil types in protected areas.

Related Benchmarks

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