Microbial Biomass Carbon (MBC)

AUS-TGP-LVG-SMB General Moderate confidence

Benchmark Value

No specific value — see range

Range: 450 to 900 mg/kg

Thresholds: Lower: 350, Upper: —

Optimal Range: 450 to 900

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

Contributing Benchmarks

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

Evidence & Context

Best-Practice Benchmark: The reference value for Microbial Biomass Carbon representing a high state of ecological health is determined to be in the range of 450 – 900 mg/kg.

Metric Definition:

Microbial Biomass Carbon (MBC) in the topsoil (0–10 cm) representing a high state of ecological health achievable within a managed agricultural landscape.

Benchmark Definition:

This benchmark represents the range of Microbial Biomass Carbon in soils of temperate grassy woodlands and plains under livestock grazing, indicating a biologically active and healthy soil with high organic matter turnover.

Justification:

The benchmark is a derived range based on a synthesis of SOC data from well-managed temperate pastures and established MBC:SOC ratios, reflecting a high state of ecological health.

Sources (1)

Soil carbon stocks under different pastures and pasture management in the higher rainfall areas of south-eastern Australia Journal

Soil carbon stocks under different pastures and pasture management in the higher rainfall areas of south-eastern Australia

View Source

Supporting Sources (6)

Additional references from the underlying research that informed this benchmark.

A global meta-analysis of livestock grazing impacts on soil ...

Meta Analysis Journal

Regenerative opportunities for building soil biological resilience – a ...

View Source

Interpreting Microbial Biomass Carbon | Fact Sheets | soilquality.org.au, accessed August 28, 2025,

Direct Evidence GreyLiterature

Interpreting Microbial Biomass Carbon | Fact Sheets | soilquality.org.au

View Source

Journal on Protected Mountain Areas Research and Management

Direct Evidence Journal

Development of a new piosphere in arid chenopod shrubland grazed by sheep. I. Changes to the soil surface. - ResearchGate

View Source

Microbe Biomass in Relation to Organic Carbon and Clay in Soil - MDPI, accessed August 28, 2025,

Contextual Support Journal

Forest Soil Microbiomes: A Review of Key Research from 2003 to 2023 - MDPI

View Source

Predicting and regulating soil carbon in a warmer world | TERN Australia, accessed August 28, 2025,

Contextual Support Government

Fact Sheets Soil Organic Carbon Storage in the Western Avon Basin - WA

View Source

Regenerative opportunities for building soil biological resilience – a ..., accessed May 11, 2025

Direct Evidence GreyLiterature

Regenerative opportunities for building soil biological resilience – a case study in the low-rainfall zone in Southern Australia - GRDC

View Source

Context

Region Australia
Biome Temperate Grassy Woodlands & Plains
Land Use Livestock Grazing & Pasture
Assessment Not Stated
Evidence Type ReferenceCondition

Lifecycle

Status Active
Version 1
Effective From 3 Jun 2026

Notes

Lower Critical Threshold: 350 mg/kg. No upper detrimental threshold — higher values are always better up to natural saturation. The range reflects a well-managed, resilient grazing system. AssessmentContext defaulted to 'Not Stated' because the source document did not state one.

Related Benchmarks

Other benchmarks in the AUS-TGP-LVG-SMB family.