Microbial Biomass Carbon (MBC)

AUS-AMR-FOR-SMB General Moderate confidence

Benchmark Value

630 mg/kg

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 3 benchmarks together — the OptimalRange form drives the primary score, while 2 guard(s) constrain the result.

Contributing Benchmarks

OptimalRange Primary Point Guard MinimumOnly Guard

Evidence & Context

The derived benchmark for the topsoil (0–10 cm) is 630 mg/kg.

Metric Definition:

Microbial Biomass Carbon (MBC) is the measure of the carbon contained within the living soil microorganisms including bacteria, fungi, archaea, and protozoa.

Benchmark Definition:

This benchmark represents a scientifically defensible reference level of Microbial Biomass Carbon in topsoil (0–10 cm) for sustainable Production Forestry in Australia's Arid Mountain Ranges & Uplands, reflecting a healthy, biologically active soil system under regional climatic and edaphic constraints.

Justification:

The benchmark is derived using a proxy-based methodology from an analogue ecosystem's Soil Organic Carbon value and a standard conversion factor for Australian soils, reflecting climatic and edaphic constraints.

Sources (4)

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

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

Effects of Nitrogen Addition and Precipitation Reduction on Microbial and Soil Nutrient Imbalances in a Temperate Forest Ecosystem

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, GreyLiterature

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

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

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

Global negative effects of nitrogen deposition on soil microbes - PMC, accessed July 31, 2025

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

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

The relationship between soil organic carbon and soil surface characteristics in the semi-arid rangelands of southern Australia | Request PDF - ResearchGate

Supporting Sources (16)

Additional references from the underlying research that informed this benchmark.

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

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, accessed July 31, 2025

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

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

Contextual Support Journal

Australia's Framework of Criteria and Indicators - DAFF, accessed July 30, 2025,

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

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

Contextual Support

Sustainable forest management: the Australian context - DAFF

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

How should we manage our soils to increase soil carbon?, accessed May 10, 2026

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

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

Methodology Source Government

Soil compaction - practical considerations - Forest Research, accessed August 9, 2025

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

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

Contextual Support Government

Learning More About Ephemeral Creeks | Flow-MER

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, accessed July 30, 2025

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

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

Contextual Support GreyLiterature

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

Preview of Land | State of the Environment Report 2011

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

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

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

Preview of Soil condition | NSW State of the Environment

Soil condition | NSW State of the Environment

Contextual Support

Soil condition | NSW State of the Environment

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

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

Contextual Support GreyLiterature

Responses of soil labile organic carbon stocks and the carbon pool management index to different vegetation restoration types in the Danxia landform region of southwest China - PMC - PubMed Central

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, accessed July 31, 2025

Preview of Sustainable Forest Management

Sustainable Forest Management

Contextual Support Journal

Australia's Sustainable Forest Management - DAFF, accessed July 31, 2025

Preview of Sustainable Forest Management, accessed July 30, 2025,

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

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

Context

Region Australia
Biome Arid Mountain Ranges & Uplands
Land Use Production Forestry
Assessment Conservation Target
Evidence Type ReferenceCondition

Lifecycle

Status Active
Version 1
Effective From 4 Jun 2026

Notes

Lower Critical Threshold: 200 mg/kg. No upper detrimental threshold — higher values are always better up to natural saturation. The benchmark represents a state of high environmental health and biological activity.