Fungal:Bacterial Ratio

AUS-TMS-CON-SFB General Moderate confidence

Benchmark Value

1.4 index
Range: 1 to 1.81 index
Thresholds: Lower: 0.99, Upper: —
Optimal Range: 1 to 1.81
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 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 LowerThreshold Guard OptimalRange Guard Point Guard LowerThreshold Guard Point Guard

Evidence & Context

The mean F:B ratio across all fire treatments (unburnt, early biennial, late biennial) was 1.4 10.41 (S.D.), and importantly, the F:B ratio was not significantly affected by the different fire regimes.

Metric Definition:

Ratio of fungal to bacterial biomass in soil, indicating soil ecological status and functional pathways.

Benchmark Definition:

This benchmark represents the typical fungal to bacterial biomass ratio in soil for tropical monsoonal savannas under conservation management in Australia, indicating soil ecological health and functional stability.

Justification:

The selected reference value of 1.4 (unitless) is based on the findings of Blunden et al. (2024), a recent, peer-reviewed study conducted in a tropical savanna ecosystem near Darwin, Northern Territory, Australia. This research involved a long-term (17-year) fire experiment, which measured fungal and bacterial abundance in topsoils (0-10 cm) across different fire regimes, including unburnt control plots, early dry season biennial burns, and late dry season biennial burns. The mean F:B ratio across all treatments was reported as 1.4 10.41 (standard deviation), and critically, the study concluded that the F:B ratio was not significantly altered by these varied fire regimes after 17 years.

Sources (1)

Preview of EFFECTS OF AGRICULTURAL MANAGEMENT ON SOIL CARBON ..., accessed on June 7, 2025
EFFECTS OF AGRICULTURAL MANAGEMENT ON SOIL CARBON ..., accessed on June 7, 2025 Journal

Fire regime impacts on soil microbes, soil organic carbon and ground cover in an Australian tropical savanna - CSIRO PUBLISHING | International Journal of Wildland Fire, accessed on June 7, 2025

View Source

Supporting Sources (1)

Additional references from the underlying research that informed this benchmark.

Preview of Contextual metadata �� Australian Microbiome, accessed on June 7, 2025
Contextual metadata �� Australian Microbiome, accessed on June 7, 2025
Contextual Support GreyLiterature

Contextual metadata �� Australian Microbiome, accessed on June 7, 2025

View Source

Context

  • Region Australia
  • Biome Tropical Monsoonal Savannas
  • Land Use Conservation / Protected Natural Areas
  • Assessment Pristine Reference
  • Evidence Type ReferenceCondition

Lifecycle

  • Status Active
  • Version 1
  • Effective From 24 Mar 2026

Notes

Lower Critical Threshold: No specific numerical threshold is defined for this exact context. However, F:B ratios persistently below 1.0, approaching levels seen in highly disturbed agricultural systems (e.g., <0.5-1.0), could indicate compromised soil health, reduced carbon sequestration potential, and a shift away from mature, stable conditions. Optimal Range: An optimal range for this biome under conservation is likely between 1.0 and 2.0. Upper Detrimental Threshold: No evidence suggests an upper detrimental F:B threshold in natural or conservation-managed tropical savannas. [Migration] Original wider evidence range: 1 – 2 (retained OptimalRange: 1 – 1.81)