Soil pH — Benchmark Detail

Benchmark Value

No specific value — see range

Range: 5 to 6.5 pH

Optimal Range: 5 to 6.5

Direction: Higher 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 analysis concludes that an optimal pH range for these ecosystems is between 5.0 and 6.5.

Metric Definition:

Soil pH measured in topsoil (0-10 cm) using a 1:5 soil-to-water suspension method.

Benchmark Definition:

Optimal soil pH range supporting highest ecological function and biodiversity in Australian tropical rainforests.

Justification:

Derived from multi-site field study of undisturbed rainforest ecosystems including Daintree National Park, supported by multiple lines of evidence including nutrient availability principles and ecological studies.

Sources (1)

Soil and plant nutrient concentrations across a tropical forest-sclerophyll vegetation boundary in north-eastern Australia Journal

Soil and plant nutrient concentrations across a tropical forest-sclerophyll vegetation boundary in north-eastern Australia

View Source

Supporting Sources (2)

Additional references from the underlying research that informed this benchmark.

ASC - VERTOSOLS - Soil Science Australia

Contextual Support

What are the optimum nutrient targets for pastures? - Soil Health Knowledgebase

View Source

Preview of Offord, C. A., & Meagher, P. F. (2014). Light and soil pH have a combined effect on the growth and morphology of the critically endangered Wollemi pine (Wollemia nobilis). AoB Plants, 6, plu011.

Offord, C. A., & Meagher, P. F. (2014). Light and soil pH have a combined effect on the growth and morphology of the critically endangered Wollemi pine (Wollemia nobilis). AoB Plants, 6, plu011.

Contextual Support Journal

Growing up or growing out? How soil pH and light affect seedling growth of a relictual rainforest tree | AoB PLANTS | Oxford Academic, accessed July 20, 2025,

View Source

Context

Region Australia
Biome Tropical & Subtropical Rainforests
Land Use Conservation / Protected Natural Areas
Assessment Pristine Reference
Vegetation Forest
Evidence Type ReferenceCondition

Lifecycle

Status Active
Version 1
Effective From 8 Jun 2026

Notes

Values below pH 5.0 can induce aluminium toxicity stress; values above pH 7.5 indicate a degraded state with nutrient imbalances and nitrogen loss.

Related Benchmarks

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