Microbial Biomass Carbon (MBC)

AUS-AMR-FOR-SMB General Low confidence

Benchmark Value

200 mg/kg

Thresholds: Lower: 200, Upper: —

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.

Evidence & Context

A sustained MBC level below 200 mg/kg can be proposed as a critical red flag.

Metric Definition:

Microbial Biomass Carbon (MBC) level below which essential ecosystem functions are significantly compromised.

Benchmark Definition:

This benchmark defines a critical red flag threshold for Microbial Biomass Carbon below which essential ecosystem functions are significantly impaired in the Arid Mountain Ranges & Uplands biome under production forestry.

Justification:

This value is informed by observations in severely degraded agricultural systems, which represent a lower bound of ecological function.

Sources (1)

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

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

Interpreting Microbial Biomass Carbon | Fact Sheets | soilquality.org.au, accessed July 18, 2025,

View Source

Supporting Sources (19)

Additional references from the underlying research that informed this benchmark.

2.2.1 Soil microbial biomass – C, N, and P - ClimEx Handbook

Contextual Support Journal

2.2.1 Soil microbial biomass – C, N, and P - ClimEx Handbook

View Source

Australia's Framework of Criteria and Indicators - DAFF, accessed July 12, 2025,

Contextual Support Government

Soil health and stability monitoring in forests - Natural Resources Commission, accessed July 30, 2025

View Source

Australia's Sustainable Forest Management - DAFF, accessed July 12, 2025,

Contextual Support

Sustainable forest management: the Australian context - DAFF, accessed July 12, 2025,

View Source

Preview of Australian dryland soils are acidic and nutrient-depleted, and have unique microbial communities compared with other drylands - PMC, accessed August 5, 2025,

Australian dryland soils are acidic and nutrient-depleted, and have unique microbial communities compared with other drylands - PMC, accessed August 5, 2025,

Contextual Support Journal

Root Structure and Functioning for Efficient Acquisition of Phosphorus: Matching Morphological and Physiological Traits

View Source

Bulk Density - Measurement | Fact Sheets | soilquality.org.au, accessed August 9, 2025,

Methodology Source Government

Bulk Density - Measurement | Fact Sheets | soilquality.org.au, accessed July 26, 2025,

View Source

CO₂ sink to source: Arid Australia's climate and rainfall driven tipping points

Contextual Support Journal

NVIS Fact sheet MVG 19 – Tussock grasslands, accessed May 19, 2025,

View Source

Preview of Coarse woody debris reduces the rate of moisture loss from surface soils of cleared temperate Australian woodlands - CSIRO Publishing

Coarse woody debris reduces the rate of moisture loss from surface soils of cleared temperate Australian woodlands - CSIRO Publishing

Contextual Support Journal

Coarse woody debris reduces the rate of moisture loss from surface soils of cleared temperate Australian woodlands - CSIRO PUBLISHING | Soil Research, accessed August 28, 2025,

View Source

Global negative effects of nitrogen deposition on soil microbes - PMC, accessed July 25, 2025,

Contextual Support Journal

Biological Mechanisms May Contribute to Soil Carbon Saturation

View Source

Is there any harmful effect of agrochemicals use on soil microorganisms? - ResearchGate

Contextual Support GreyLiterature

Starting / Enhancing Your Regenerative Agriculture Journey, accessed August 13, 2025,

View Source

Land | State of the Environment Report 2011

Contextual Support Journal

Australian dryland soils are acidic and nutrient-depleted, and have unique microbial communities compared with other drylands - PMC, accessed August 28, 2025,

View Source

Microbial Biomass - Qld | Fact Sheets | soilquality.org.au

Contextual Support GreyLiterature

Global negative effects of nitrogen deposition on soil microbes - PMC

View Source

Predicting and regulating soil carbon in a warmer world | TERN Australia, accessed July 6, 2025,

Contextual Support Government

Mapping soil organic carbon fractions for Australia, their stocks, and uncertainty - BG, accessed July 16, 2025,

View Source

Soil condition | NSW State of the Environment

Contextual Support

Soil condition | NSW State of the Environment

View Source

Soil microbial biomass—what do the numbers really mean? - ResearchGate, accessed August 28, 2025,

Contextual Support

Soil microbial biomass carbon and CO2? - ResearchGate, accessed July 18, 2025,

View Source

Preview of Soil microbial biomass, metabolic quotient, and carbon and nitrogen mineralisation in 25-year-old Pinus radiata agroforestry regimes - CSIRO Publishing

Soil microbial biomass, metabolic quotient, and carbon and nitrogen mineralisation in 25-year-old Pinus radiata agroforestry regimes - CSIRO Publishing

Direct Evidence Journal

Soil microbial biomass, metabolic quotient, and carbon and nitrogen mineralisation in 25-year-old Pinus radiata agroforestry regimes - CSIRO Publishing

View Source

Sustainable Forest Management

Contextual Support Journal

Australia's Sustainable Forest Management - DAFF

View Source

Sustainable Forest Management, accessed July 30, 2025,

Contextual Support GreyLiterature

Australia's Voluntary National Contribution to the United Nations Global Forest Goals – 2 April 2019

View Source

The relationship between soil organic carbon and soil surface ...

Contextual Support Journal

Gilgunia Station - Building Landscape resilience you can bank on - Soils For Life, accessed July 28, 2025,

View Source

Understanding and quantifying whole soil-profile organic carbon transfer using an environmental tracer - CSIRO Publishing, accessed August 5, 2025,

Contextual Support Journal

Understanding and quantifying whole soil-profile organic carbon transfer using an environmental tracer - CSIRO Publishing

View Source

Context

Region Australia
Biome Arid Mountain Ranges & Uplands
Land Use Production Forestry
Assessment Degradation Threshold
Evidence Type DegradationThreshold

Lifecycle

Status Active
Version 1
Effective From 19 Mar 2026

Notes

Indicates significant impairment of nutrient cycling and soil structural maintenance.

Related Benchmarks

Other benchmarks in the AUS-AMR-FOR-SMB family.