Microbial Biomass Carbon (MBC)

AUS-TDG-FOR-SMB General Moderate confidence

Benchmark Value

600 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 5 benchmarks together — the Point form drives the primary score, while 4 guard(s) constrain the result.

Contributing Benchmarks

Point Primary Point Guard LowerThreshold Guard Point Guard MinimumOnly Guard

Evidence & Context

The reference value of 600 mg/kg is an indicative target for best-practice Production Forestry in Australian Temperate Dry Woodlands & Native Grasslands (0-10 cm topsoil), aiming for high environmental health.

Metric Definition:

Microbial Biomass Carbon (MBC) is a key indicator of soil health, representing the total carbon held within the cells of living microorganisms, primarily bacteria and fungi, in the soil.

Benchmark Definition:

This benchmark represents an indicative target value for Microbial Biomass Carbon in soils under best-practice Production Forestry in Australian Temperate Dry Woodlands & Native Grasslands, aiming to maintain high soil health and biological activity.

Justification:

This value is inferred due to a lack of direct empirical data for this specific land use and biome under "best-on-offer" sustainable management in Australia. It is based on the upper range of MBC observed in healthy, productive temperate grassland ecosystems and the principle that sustainable forestry should maintain soil health comparable to healthy native systems.

Sources (1)

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Climatic, Edaphic and Biotic Controls over Soil δ13C and δ15N in ... Journal

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Supporting Sources (22)

Additional references from the underlying research that informed this benchmark.

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Adams, M, accessed on June 7, 2025,

Contextual Support Journal

Adams, M, accessed on June 7, 2025,

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An ensemble estimate of Australian soil organic ... - EGUsphere, accessed on June 7, 2025,

Contextual Support Journal

AUSTRALIA'S STATE OF THE FORESTS REPORT - DAFF, accessed March 28, 2026,

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Carbon | Australia state of the environment 2021, accessed on June 7, 2025,

Contextual Support Government

Cotching, W. E. (2012). Carbon stocks in Tasmanian soils. Soil Research, 50(2), 83-90.

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Effect of vegetation type and season on microbial biomass carbon in Central Himalayan forest soils, India - The Commonwealth Scientific and Industrial Research Organisation (CSIRO) - Discovery, accessed on June 7, 2025,

Contextual Support Journal

Effect of vegetation type and season on microbial biomass carbon in Central Himalayan forest soils, India - The Commonwealth Scientific and Industrial Research Organisation (CSIRO) - Discovery, accessed on June 7, 2025,

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Effects of heavy metals on soil microbial biomass carbon - ResearchGate, accessed on June 7, 2025,

Direct Evidence Journal

Effects of heavy metals on soil microbial biomass carbon - ResearchGate

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Effects of Management Practices on Soil Microbial Diversity and ..., accessed on June 7, 2025,

Contextual Support Journal

Effects of Management Practices on Soil Microbial Diversity and ..., accessed on June 7, 2025,

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Contextual Support GreyLiterature

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Grazing-management-for-soil-carbon-in-Australia-A-review.pdf - University of Tasmania, accessed on June 7, 2025,

Contextual Support Journal

www.utas.edu.au

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Heat input determines the response and rapid recovery of post-fire soil microbial biomass - CSIRO PUBLISHING | International Journal of Wildland Fire, accessed on June 7, 2025,

Contextual Support Journal

Heat input determines the response and rapid recovery of post-fire soil microbial biomass - CSIRO PUBLISHING | International Journal of Wildland Fire, accessed on June 7, 2025,

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Impacts of management and changed hydrology on soil microbial communities in a floodplain forest, accessed on June 7, 2025,

Contextual Support Journal

Impacts of management and changed hydrology on soil microbial communities in a floodplain forest, accessed on June 7, 2025,

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Increased microbial growth, biomass, and turnover drive soil organic carbon accumulation at higher plant diversity - PMC - PubMed Central, accessed on June 7, 2025,

Contextual Support Journal

Increased microbial growth, biomass, and turnover drive soil organic carbon accumulation at higher plant diversity - PMC - PubMed Central, accessed on June 7, 2025,

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Contextual Support Journal

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

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

Contextual Support GreyLiterature

Global negative effects of nitrogen deposition on soil microbes - PMC

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Models for the Sustainable Management of Temperate Plantation Forests - ResearchGate, accessed on June 7, 2025,

Contextual Support GreyLiterature

Models for the Sustainable Management of Temperate Plantation Forests - ResearchGate, accessed on June 7, 2025,

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Organic matter characteristics under native forest, long-term pasture, and recent conversion to Eucalyptus plantations in Western Australia: microbial biomass, soil respiration, and permanganate oxidation - CSIRO Publishing, accessed on June 7, 2025,

Contextual Support Journal

Organic matter characteristics under native forest, long-term pasture, and recent conversion to Eucalyptus plantations in Western Australia: microbial biomass, soil respiration, and permanganate oxidation - CSIRO Publishing, accessed on June 7, 2025,

Preview of Seasonal Dynamics of Soil Microbial Biomass C, N and P along an Altitudinal Gradient in Central Himalaya, India - MDPI, accessed August 28, 2025,

Seasonal Dynamics of Soil Microbial Biomass C, N and P along an Altitudinal Gradient in Central Himalaya, India - MDPI, accessed August 28, 2025,

Contextual Support Journal

Fact Sheets Biological Indicators - Soil Quality

Preview of SOIL CARBON CONTENT AND MICROBIAL BIOMASS ACTIVITY OF DIFFERENT FOREST TYPES UNDER SEASONAL VARIATIONS - IJNRD, accessed on June 7, 2025,

SOIL CARBON CONTENT AND MICROBIAL BIOMASS ACTIVITY OF DIFFERENT FOREST TYPES UNDER SEASONAL VARIATIONS - IJNRD, accessed on June 7, 2025,

Contextual Support Journal

SOIL CARBON CONTENT AND MICROBIAL BIOMASS ACTIVITY OF DIFFERENT FOREST TYPES UNDER SEASONAL VARIATIONS - IJNRD, accessed on June 7, 2025,

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Soil Carbon Pool as Influenced by Soil Microbial Activity—An Overview, accessed on June 7, 2025,

Contextual Support Journal

Soil Carbon Pool as Influenced by Soil Microbial Activity—An Overview

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Soil microbiome and biodiversity implications – are we ignoring cost-effective proxies of biodiversity measures? | TERN Australia, accessed on June 7, 2025,

Contextual Support GreyLiterature

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Contextual Support

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Thermal sensitivity of soil microbial carbon use efficiency across forest biomes - PMC, accessed on June 7, 2025,

Contextual Support Journal

Thermal sensitivity of soil microbial carbon use efficiency across forest biomes - PMC, accessed on June 7, 2025,

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Variation in soil microbial biomass in the dry tropics: impact of land-use change, accessed on June 7, 2025,

Contextual Support Journal

Soil microbial biomass during the early establishment of hoop pine ...

Context

Region Australia
Biome Temperate Dry Woodlands & Native Grasslands
Land Use Production Forestry
Assessment Pristine Reference
Evidence Type ReferenceCondition

Lifecycle

Status Active
Version 1
Effective From 17 Mar 2026

Notes

Lower Critical Threshold: Not numerically defined in reviewed literature for this specific context. Conceptually, levels significantly below those of healthy native ecosystems would indicate impaired soil function and unsustainable practices. Optimal Range: Not numerically defined but would reflect MBC levels supporting robust ecosystem functioning and sustained productivity. Upper Detrimental Threshold: No evidence suggests an upper detrimental threshold for MBC itself under best-practice sustainable forestry; more is generally better up to natural saturation points.