Soil pH

AUS-TMI-FOR-SPH General Moderate confidence

Benchmark Value

4.5 pH
Direction: Higher is desirable ↑
Form: MinimumOnly

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 13 benchmarks together — the OptimalRange form drives the primary score, while 12 guard(s) constrain the result.

Contributing Benchmarks

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

Evidence & Context

Conditions below pH 4.5 represent a state of significant ecosystem degradation and compromised long-term health.

Metric Definition:

Soil pH

Benchmark Definition:

The minimum soil pH threshold below which significant ecosystem degradation and compromised long-term health occur.

Justification:

Below this threshold, the concentration of soluble aluminum ions (Al3+) increases sharply. This is directly toxic to the fine roots of many plants, inhibiting nutrient and water uptake and stunting growth.

Sources (1)

Preview of What Soil is Best for Kentia palm Growth? - PictureThis, accessed July 30, 2025,
What Soil is Best for Kentia palm Growth? - PictureThis, accessed July 30, 2025, GreyLiterature

Pedogenic Threshold in Acidity Explains Context-Dependent Tree Species Effects on Soil Carbon - Frontiers, accessed July 30, 2025

View Source

Supporting Sources (46)

Additional references from the underlying research that informed this benchmark.

Preview of (PDF) Surprising Relationships Between Soil pH and Microbial Biomass and Activity in a Northern Hardwood Forest - ResearchGate, accessed July 30, 2025,
(PDF) Surprising Relationships Between Soil pH and Microbial Biomass and Activity in a Northern Hardwood Forest - ResearchGate, accessed July 30, 2025,
Contextual Support

(PDF) Surprising Relationships Between Soil pH and Microbial Biomass and Activity in a Northern Hardwood Forest - ResearchGate, accessed July 30, 2025

View Source
Preview of AGRICULTURAL AUDIT & LAND USE CAPABILITY ASSESSMENT ..., accessed July 30, 2025,
AGRICULTURAL AUDIT & LAND USE CAPABILITY ASSESSMENT ..., accessed July 30, 2025,
Contextual Support Journal

VEGETATION 0}' LORD HOWE ISLAND - Botanic Gardens of Sydney

View Source
Preview of Are acid soils truly chemically degraded? - ResearchGate, accessed July 30, 2025,
Are acid soils truly chemically degraded? - ResearchGate, accessed July 30, 2025,
Contextual Support

Soil pH | Environment, land and water - Queensland Government, accessed July 30, 2025

View Source
Preview of Chapter 20 ~ Causes and Consequences of Acidification of Forest Soils, accessed July 30, 2025,
Chapter 20 ~ Causes and Consequences of Acidification of Forest Soils, accessed July 30, 2025,
Contextual Support Direct Evidence GreyLiterature

Chapter 20 ~ Causes and Consequences of Acidification of Forest Soils, accessed July 30, 2025,

View Source
Preview of Christmas and Cocos Islands tropical forests - Wikipedia, accessed July 30, 2025,
Christmas and Cocos Islands tropical forests - Wikipedia, accessed July 30, 2025,
Contextual Support GreyLiterature

Flora of the Cocos (Keeling) Islands - Wikipedia, accessed July 30, 2025

View Source
Preview of Christmas Island Mine site to Forest Rehabilitation program review - Department of Infrastructure, Transport, Regional Development and Communications, accessed July 30, 2025,
Christmas Island Mine site to Forest Rehabilitation program review - Department of Infrastructure, Transport, Regional Development and Communications, accessed July 30, 2025,
Contextual Support Journal

Christmas Island Mine site to Forest Rehabilitation program review - Department of Infrastructure, Transport, Regional Development and Communications, accessed July 30, 2025

View Source
Preview of Christmas Island National Park - DCCEEW, accessed July 30, 2025,
Christmas Island National Park - DCCEEW, accessed July 30, 2025,
Contextual Support Journal

Christmas Island National Park - DCCEEW, accessed August 2, 2025

View Source
Preview of Christmas Island Yellow Crazy Ant Control Program - DCCEEW, accessed July 30, 2025,
Christmas Island Yellow Crazy Ant Control Program - DCCEEW, accessed July 30, 2025,
Contextual Support Journal

Christmas Island Yellow Crazy Ant Control Program - DCCEEW

View Source
Preview of Cocos (Keeling) Islands - New World Encyclopedia, accessed July 30, 2025, )_Islands
Cocos (Keeling) Islands - New World Encyclopedia, accessed July 30, 2025, )_Islands
Contextual Support GreyLiterature

The Buzz of the Saw: Utilising Norfolk Island's unique icon, accessed July 30, 2025

View Source
Preview of Cocos nucifera (coconut) | CABI Compendium, accessed July 30, 2025,
Cocos nucifera (coconut) | CABI Compendium, accessed July 30, 2025,
Contextual Support Irrelevant

Cocos nucifera (coconut) | CABI Compendium, accessed July 30, 2025,

View Source
Preview of Cocos nucifera L. - Forest Service, accessed July 30, 2025, ).pdf
Cocos nucifera L. - Forest Service, accessed July 30, 2025, ).pdf
Contextual Support

Norfolk Island Pine Production Guide - Mid-Florida Research and Education Center, accessed July 30, 2025

View Source
Preview of Constraints to Tree Growth Imposed by Urban Soil Alkalinity | Arboriculture & Urban Forestry, accessed July 30, 2025,
Constraints to Tree Growth Imposed by Urban Soil Alkalinity | Arboriculture & Urban Forestry, accessed July 30, 2025,
Contextual Support Journal

Constraints to Tree Growth Imposed by Urban Soil Alkalinity | Arboriculture & Urban Forestry, accessed July 30, 2025,

View Source
Preview of Ecological speciation in sympatric palms: 2. Pre‐ and post‐zygotic isolation - PMC, accessed July 30, 2025,
Ecological speciation in sympatric palms: 2. Pre‐ and post‐zygotic isolation - PMC, accessed July 30, 2025,
Contextual Support Irrelevant Journal

Floristics and structure of the mossy cloud forest - of Mt ... - Ian Hutton, accessed July 30, 2025

View Source
Preview of Effects of soil pH on the growth, soil nutrient composition, and rhizosphere microbiome of Ageratina adenophora - PMC - PubMed Central, accessed July 30, 2025,
Effects of soil pH on the growth, soil nutrient composition, and rhizosphere microbiome of Ageratina adenophora - PMC - PubMed Central, accessed July 30, 2025,
Contextual Support Journal

Do regenerative grazing management practices improve vegetation ...

View Source
Preview of Factors influencing decline in soil pH in Hawaiian Eucalyptus and Albizia plantations, accessed July 30, 2025,
Factors influencing decline in soil pH in Hawaiian Eucalyptus and Albizia plantations, accessed July 30, 2025,
Contextual Support

Factors influencing decline in soil pH in Hawaiian Eucalyptus and Albizia plantations, accessed July 30, 2025,

View Source
Preview of Flora of the Cocos (Keeling) Islands - Wikipedia, accessed July 30, 2025, )_Islands
Flora of the Cocos (Keeling) Islands - Wikipedia, accessed July 30, 2025, )_Islands
Contextual Support

Flora of the Cocos (Keeling) Islands - Wikipedia, accessed July 30, 2025, )_Islands

View Source
Preview of Floristics and structure of the mossy cloud forest of Mt Gower summit, Lord Howe Island
Floristics and structure of the mossy cloud forest of Mt Gower summit, Lord Howe Island
Direct Evidence Journal

Floristics and structure of the mossy cloud forest of Mt Gower summit, Lord Howe Island

View Source
Preview of Geology - Lord Howe Island Museum, accessed July 30, 2025,
Geology - Lord Howe Island Museum, accessed July 30, 2025,
Contextual Support GreyLiterature

Flora - K'gari (Fraser Island) Defenders Organisation

View Source
Preview of Geology - Norfolk Island Flora & Fauna Society, accessed July 30, 2025,
Geology - Norfolk Island Flora & Fauna Society, accessed July 30, 2025,
Contextual Support GreyLiterature

Geology - Norfolk Island Flora & Fauna Society, accessed July 30, 2025,

View Source
Preview of Geology | Lord Howe Island Australia, accessed July 30, 2025,
Geology | Lord Howe Island Australia, accessed July 30, 2025,
Contextual Support Irrelevant

Geology | Lord Howe Island Australia, accessed July 30, 2025,

View Source
Preview of Geology | Norfolk Island National Park | Parks Australia, accessed July 30, 2025,
Geology | Norfolk Island National Park | Parks Australia, accessed July 30, 2025,
Contextual Support Government

AGRICULTURAL AUDIT & LAND USE CAPABILITY ASSESSMENT ..., accessed July 30, 2025

View Source
Preview of Geology and Geography - Lord Howe Island, accessed July 30, 2025,
Geology and Geography - Lord Howe Island, accessed July 30, 2025,
Contextual Support GreyLiterature

Geology | Lord Howe Island Australia, accessed July 30, 2025

View Source
Preview of Global Trajectories of Forest Soil Acidification: A Scientometric Synthesis of Drivers, Impacts and Sustainable Solutions - MDPI, accessed July 30, 2025,
Global Trajectories of Forest Soil Acidification: A Scientometric Synthesis of Drivers, Impacts and Sustainable Solutions - MDPI, accessed July 30, 2025,
Contextual Support Journal

SOIL CHEMICAL PROPERTIES AND FOREST FLOOR NUTRIENTS UNDER REPEATED PRESCRIBED- BURNING IN - Scion, accessed July 20, 2025,

View Source
Preview of Grow The Glorious Norfolk Island Pine In Your Garden - Sequoia Valley Farms, accessed July 30, 2025,
Grow The Glorious Norfolk Island Pine In Your Garden - Sequoia Valley Farms, accessed July 30, 2025,
Contextual Support Irrelevant

Grow The Glorious Norfolk Island Pine In Your Garden - Sequoia Valley Farms, accessed July 30, 2025,

View Source
Preview of How to Grow and Care for Kentia Palm - MyDomaine, accessed July 30, 2025,
How to Grow and Care for Kentia Palm - MyDomaine, accessed July 30, 2025,
Contextual Support GreyLiterature

How to Grow and Care for Kentia Palm - MyDomaine, accessed July 30, 2025

View Source
Preview of How to Grow and Care for Norfolk island pine - PictureThis, accessed July 30, 2025,
How to Grow and Care for Norfolk island pine - PictureThis, accessed July 30, 2025,
Contextual Support GreyLiterature

Grow The Glorious Norfolk Island Pine In Your Garden - Sequoia Valley Farms, accessed July 30, 2025

View Source
Preview of How to Plant, Grow, and Care for Norfolk Island Pine - Planet Natural, accessed July 30, 2025,
How to Plant, Grow, and Care for Norfolk Island Pine - Planet Natural, accessed July 30, 2025,
Contextual Support Irrelevant

How to Plant, Grow, and Care for Norfolk Island Pine - Planet Natural, accessed July 30, 2025,

View Source
Preview of Incredible Great Barrier Reef Islands For Your Holiday - Visitor's Guide - Queensland, accessed July 30, 2025,
Incredible Great Barrier Reef Islands For Your Holiday - Visitor's Guide - Queensland, accessed July 30, 2025,
Contextual Support Irrelevant

Incredible Great Barrier Reef Islands For Your Holiday - Visitor's Guide - Queensland, accessed August 2, 2025

View Source
Preview of Kentia Palm (Howea forsteriana) - Care Guide and Plant Information - Healthy Houseplants, accessed July 30, 2025,
Kentia Palm (Howea forsteriana) - Care Guide and Plant Information - Healthy Houseplants, accessed July 30, 2025,
Contextual Support Irrelevant GreyLiterature

What Soil is Best for Kentia palm Growth? - PictureThis, accessed July 30, 2025

View Source
Preview of Lord Howe Island - Wikipedia, accessed July 30, 2025,
Lord Howe Island - Wikipedia, accessed July 30, 2025,
Contextual Support GreyLiterature

Lord Howe Island - Wikipedia

View Source
Preview of Lord Howe Island Subtropical Forests | One Earth, accessed July 30, 2025,
Lord Howe Island Subtropical Forests | One Earth, accessed July 30, 2025,
Contextual Support Irrelevant GreyLiterature

Safeguarding Lord Howe Island World Heritage Area - Local Land Services

View Source
Preview of Norfolk Island - Wikipedia, accessed July 30, 2025,
Norfolk Island - Wikipedia, accessed July 30, 2025,
Contextual Support Irrelevant

Norfolk Island - Wikipedia

View Source
Preview of Norfolk Island pine - Araucaria heterophylla - NZ Farm Forestry Association, accessed July 30, 2025,
Norfolk Island pine - Araucaria heterophylla - NZ Farm Forestry Association, accessed July 30, 2025,
Contextual Support GreyLiterature

Geology and Geography - Lord Howe Island, accessed July 30, 2025

View Source
Preview of Norfolk Island Pine care: Tips for growing araucaria indoors - Growcycle, accessed July 30, 2025,
Norfolk Island Pine care: Tips for growing araucaria indoors - Growcycle, accessed July 30, 2025,
Contextual Support Irrelevant

How to Grow and Care for Norfolk Island pine - PictureThis, accessed July 30, 2025

View Source
Preview of Norfolk Island Pine: Plant Care & Growing Guide - The Spruce, accessed July 30, 2025,
Norfolk Island Pine: Plant Care & Growing Guide - The Spruce, accessed July 30, 2025,
Contextual Support Irrelevant

How to Plant, Grow, and Care for Norfolk Island Pine - Planet Natural, accessed July 30, 2025

View Source
Preview of Norfolk Island Subtropical Forests | One Earth, accessed July 30, 2025,
Norfolk Island Subtropical Forests | One Earth, accessed July 30, 2025,
Contextual Support Irrelevant

Conservation | Norfolk Island National Park | Parks Australia, accessed August 2, 2025

View Source
Preview of Norfolk Island Water Resource Assessment, accessed July 30, 2025,
Norfolk Island Water Resource Assessment, accessed July 30, 2025,
Contextual Support Journal

Climate-Affected Australian Tropical Montane Cloud Forest Plants: Metabolomic Profiles, Isolated Phytochemicals, and Bioactivities - PubMed Central

View Source
Preview of On Soil and Speciation - In Defense of Plants, accessed July 30, 2025,
On Soil and Speciation - In Defense of Plants, accessed July 30, 2025,
Contextual Support Journal

Ecological speciation in sympatric palms: 5. Evidence for pleiotropic speciation genes using gene knockout and high-throughput phenotyping - Oxford Academic, accessed July 30, 2025

View Source
Preview of Pedogenic Threshold in Acidity Explains Context-Dependent Tree Species Effects on Soil Carbon - Frontiers, accessed July 30, 2025,
Pedogenic Threshold in Acidity Explains Context-Dependent Tree Species Effects on Soil Carbon - Frontiers, accessed July 30, 2025,
Contextual Support Irrelevant

Chapter 20 ~ Causes and Consequences of Acidification of Forest Soils, accessed July 30, 2025

View Source
Preview of Plants - Cocos Keeling Islands, accessed July 30, 2025,
Plants - Cocos Keeling Islands, accessed July 30, 2025,
Contextual Support GreyLiterature

Plants - Cocos Keeling Islands, accessed July 30, 2025,

View Source
Preview of Red Crab Migration — Christmas Island, accessed July 30, 2025,
Red Crab Migration — Christmas Island, accessed July 30, 2025,
Contextual Support GreyLiterature

Christmas Island Yellow Crazy Ant Control Program - DCCEEW, accessed July 30, 2025

View Source
Preview of Responses to controlled release potassium fertilisers in agriculture following phosphate mining - CSIRO PUBLISHING | Soil Research, accessed July 30, 2025,
Responses to controlled release potassium fertilisers in agriculture following phosphate mining - CSIRO PUBLISHING | Soil Research, accessed July 30, 2025,
Contextual Support Journal

Cocos nucifera L. - Forest Service, accessed July 30, 2025

View Source
Preview of Soil pH | Environment, land and water - Queensland Government, accessed July 30, 2025,
Soil pH | Environment, land and water - Queensland Government, accessed July 30, 2025,
Contextual Support Government

Australian dryland soils are acidic and nutrient‐depleted, and have unique microbial communities compared with other drylands - Arid Ecology Lab

View Source
Preview of The Buzz of the Saw: Utilising Norfolk Island's unique icon, accessed July 30, 2025,
The Buzz of the Saw: Utilising Norfolk Island's unique icon, accessed July 30, 2025,
Contextual Support GreyLiterature

The Buzz of the Saw: Utilising Norfolk Island's unique icon, accessed July 30, 2025,

View Source
Preview of The future role of the National Park Forestry Zone in a ... - DCCEEW, accessed July 30, 2025,
The future role of the National Park Forestry Zone in a ... - DCCEEW, accessed July 30, 2025,
Contextual Support Journal

Norfolk Island Native Plants

View Source
Preview of Torres Strait Islands, accessed July 30, 2025,
Torres Strait Islands, accessed July 30, 2025,
Contextual Support Journal

Plants - Cocos Keeling Islands, accessed July 30, 2025

View Source

Context

  • Region Australia
  • Biome Tropical & Subtropical Maritime Islands
  • Land Use Production Forestry
  • Assessment Not Stated
  • Evidence Type DegradationThreshold

Lifecycle

  • Status Active
  • Version 1
  • Effective From 28 May 2026

Notes

A soil pH below 5.0 indicates increasing stress. AssessmentContext defaulted to 'Not Stated' because the source document did not state one.

Related Benchmarks

Other benchmarks in the AUS-TMI-FOR-SPH family.

— pH Moderate
Production Forestry · Not Stated
OptimalRange Active v1
7.5 pH Moderate
Production Forestry · Not Stated
MaximumOnly Active v1