Microbial Biomass Carbon (MBC)

AUS-TGP-FOR-SMB General Moderate confidence

Benchmark Value

700 mg/kg
Thresholds: Lower: 700, 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. 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

Therefore, a loss of more than 50% of the MBC from the native reference benchmark likely represents a transition into a functionally degraded state. This would correspond to an MBC value below approximately 700 mg/kg.

Metric Definition:

Microbial Biomass Carbon (MBC) is the quantitative measure of the carbon mass contained within living soil microorganisms.

Benchmark Definition:

This benchmark defines a functional degradation threshold for Microbial Biomass Carbon, below which key soil ecosystem processes are impaired in temperate grassy woodlands under production forestry.

Justification:

A functional threshold below which key ecosystem processes are impaired is inferred from evidence showing >50% loss from native reference value corresponds to functional degradation.

Sources (1)

Preview of A meta-analysis of soil microbial biomass responses to forest disturbances - PMC
A meta-analysis of soil microbial biomass responses to forest disturbances - PMC Journal

A meta-analysis of soil microbial biomass responses to forest disturbances - PMC

View Source

Supporting Sources (24)

Additional references from the underlying research that informed this benchmark.

Preview of A meta-analysis of soil microbial biomass responses to forest disturbances - PMC, accessed August 28, 2025,
A meta-analysis of soil microbial biomass responses to forest disturbances - PMC, accessed August 28, 2025,
Contextual Support Journal

Selective logging impacts on soil microbial communities and functioning in Bornean tropical forest - Frontiers

View Source
Preview of A review on effective soil health bio-indicators for ecosystem restoration and sustainability, accessed August 5, 2025,
A review on effective soil health bio-indicators for ecosystem restoration and sustainability, accessed August 5, 2025,
Contextual Support Journal

Seasonal variations in soil characteristics control microbial respiration and carbon use under tree plantations in the middle gangetic region - PMC - PubMed Central, accessed July 28, 2025

View Source
Preview of Age and Species of Eucalyptus Plantations Affect Soil Microbial ...
Age and Species of Eucalyptus Plantations Affect Soil Microbial ...
Contextual Support Journal

Contrasting Soil pH Effects on Fungal and Bacterial Growth Suggest Functional Redundancy in Carbon Mineralization - PMC, accessed July 21, 2025

View Source
Preview of Australia's Framework of Criteria and Indicators - DAFF
Australia's Framework of Criteria and Indicators - DAFF
Contextual Support Journal

Australia's Framework of Criteria and Indicators - DAFF

View Source
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 Government

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

View Source
Preview of ECOLOGICALLY SUSTAINABLE FOREST MANAGEMENT - Forestry Australia, accessed August 10, 2025,
ECOLOGICALLY SUSTAINABLE FOREST MANAGEMENT - Forestry Australia, accessed August 10, 2025,
Contextual Support Journal

guidelines for sustainable forestry on private lands ... - ResearchGate, accessed July 31, 2025

View Source
Preview of Effects of Forest Types and Environmental Factors on Soil Microbial Biomass in a Coastal Sand Dune of Subtropical China - Journal of Resources and Ecology
Effects of Forest Types and Environmental Factors on Soil Microbial Biomass in a Coastal Sand Dune of Subtropical China - Journal of Resources and Ecology
Contextual Support Journal

Fungi to bacteria ratio: Historical misinterpretations and potential implications | Request PDF, accessed July 12, 2025,

View Source
Preview of Interpreting Microbial Biomass Carbon | Fact Sheets | soilquality.org ...
Interpreting Microbial Biomass Carbon | Fact Sheets | soilquality.org ...
Contextual Support Government

Microbial Biomass Carbon - NSW | Fact Sheets | soilquality.org.au

View Source
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,
Contextual Support Government

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

View Source
Preview of Microbial Biomass | Fact Sheets | soilquality.org.au
Microbial Biomass | Fact Sheets | soilquality.org.au
Contextual Support Government

Soil temperature, microbial biomass and enzyme activity are the critical factors affecting soil respiration in different soil layers in Ziwuling Mountains, China

View Source
Preview of Microbiological Indicators for Assessing the Effects of Agricultural Practices on Soil Health: A Review - MDPI, accessed on June 5, 2025
Microbiological Indicators for Assessing the Effects of Agricultural Practices on Soil Health: A Review - MDPI, accessed on June 5, 2025
Contextual Support Journal

Microbiological Indicators for Assessing the Effects of Agricultural Practices on Soil Health: A Review - MDPI, accessed August 13, 2025,

View Source
Preview of Restoration of eucalypt grassy woodland: effects of experimental interventions on ground-layer vegetation - CSIRO PUBLISHING | Australian Journal of Botany, accessed August 12, 2025,
Restoration of eucalypt grassy woodland: effects of experimental interventions on ground-layer vegetation - CSIRO PUBLISHING | Australian Journal of Botany, accessed August 12, 2025,
Contextual Support Journal

Full article: Making soil carbon credits work for climate change mitigation

View Source
Preview of Reviews of High Priority Species for Woody Biomass Crops in Lower Rainfall Southern Australia - Enviro Data SA
Reviews of High Priority Species for Woody Biomass Crops in Lower Rainfall Southern Australia - Enviro Data SA
Contextual Support Journal

Southeast Australia Temperate Forests | One Earth

View Source
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

View Source
Preview of Soil carbon sequestration in rangelands a critical review of the impacts of major management strategies - CSIRO Publishing, accessed August 5, 2025,
Soil carbon sequestration in rangelands a critical review of the impacts of major management strategies - CSIRO Publishing, accessed August 5, 2025,
Contextual Support

Soil carbon sequestration in rangelands a critical review of the impacts of major management strategies - CSIRO Publishing, accessed May 13, 2025,

View Source
Preview of Soil Carbon Sequestration Potential: A review for Australian ... - MLA
Soil Carbon Sequestration Potential: A review for Australian ... - MLA
Contextual Support Journal

Soil Carbon Sequestration Potential: A review for Australian ... - MLA

View Source
Preview of Soil carbon, nutrient, and microbial interactions in a phosphorus limited ecosystem exposed to elevated CO2 Johanna Pihlblad - Research Profiles and Repository - Western Sydney University
Soil carbon, nutrient, and microbial interactions in a phosphorus limited ecosystem exposed to elevated CO2 Johanna Pihlblad - Research Profiles and Repository - Western Sydney University
Contextual Support Journal

Soil carbon, nutrient, and microbial interactions in a phosphorus limited ecosystem exposed to elevated CO2 Johanna Pihlblad - Research Profiles and Repository - Western Sydney University

View Source
Preview of Soil microbial biomass carbon and nitrogen in forest ecosystems of Northeast China: a comparison between natural secondary forest and larch plantation | Journal of Plant Ecology | Oxford Academic
Soil microbial biomass carbon and nitrogen in forest ecosystems of Northeast China: a comparison between natural secondary forest and larch plantation | Journal of Plant Ecology | Oxford Academic
Contextual Support

Soil microbial biomass carbon and nitrogen in forest ecosystems of Northeast China: a comparison between natural secondary forest and larch plantation | Journal of Plant Ecology | Oxford Academic

View Source
Preview of Soil microbial biomass carbon and nitrogen in forest ecosystems of Northeast China: a comparison between natural secondary forest and larch plantation | Journal of Plant Ecology | Oxford Academic, accessed August 28, 2025,
Soil microbial biomass carbon and nitrogen in forest ecosystems of Northeast China: a comparison between natural secondary forest and larch plantation | Journal of Plant Ecology | Oxford Academic, accessed August 28, 2025,
Contextual Support Journal

Forests and Decarbonization – Roles of Natural and Planted Forests - Frontiers

View Source
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

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

View Source
Preview of Soil microbial biomass, activity and community composition in adjacent native and plantation forests of subtropical Australia | Request PDF - ResearchGate
Soil microbial biomass, activity and community composition in adjacent native and plantation forests of subtropical Australia | Request PDF - ResearchGate
Contextual Support Journal

Soil water characteristics of a red chromosol and brown vertosol and ..., accessed May 19, 2025,

View Source
Preview of Soil temperature, microbial biomass and enzyme activity are the critical factors affecting soil respiration in different soil layers in Ziwuling Mountains, China - PMC, accessed August 5, 2025,
Soil temperature, microbial biomass and enzyme activity are the critical factors affecting soil respiration in different soil layers in Ziwuling Mountains, China - PMC, accessed August 5, 2025,
Contextual Support Journal

Forest Soil Bacteria: Diversity, Involvement in Ecosystem Processes, and Response to Global Change - PubMed Central

View Source
Preview of Srivastava, S. C., & Singh, J. S. (1989). Effect of cultivation on microbial biomass C and N of a dry tropical forest soil. Biology and Fertility of Soils, 8(4), 343-348.
Srivastava, S. C., & Singh, J. S. (1989). Effect of cultivation on microbial biomass C and N of a dry tropical forest soil. Biology and Fertility of Soils, 8(4), 343-348.
Contextual Support Journal

Top 6 Sustainable Forest Management Techniques, accessed July 19, 2025,

View Source
Preview of Woodlands - DCCEEW, accessed August 5, 2025,
Woodlands - DCCEEW, accessed August 5, 2025,
Contextual Support

Woodlands - DCCEEW, accessed May 19, 2025

View Source

Context

  • Region Australia
  • Biome Temperate Grassy Woodlands & Plains
  • Land Use Production Forestry
  • Assessment Pristine Reference
  • Evidence Type DegradationThreshold

Lifecycle

  • Status Active
  • Version 1
  • Effective From 20 Mar 2026

Notes

This threshold is inferred rather than directly measured, based on proportional loss of MBC relative to total SOC loss in agricultural conversion. ConsistencyResolver applied 2026-03-23 00:16 UTC: UpperThreshold 700 → (check: MaxBelowPointValue, rationale: Removing the UpperThreshold value as the threshold is a lower limit, not an upper limit.) ConsistencyResolver applied 2026-03-23 00:16 UTC: LowerThreshold → 700 (check: MaxBelowPointValue, rationale: The Notes state that 700 mg/kg is a lower critical threshold below which soil function is impaired, indicating this is a MinimumOnly threshold. Moving the value from UpperThreshold to LowerThreshold will auto-correct the form to MinimumOnly and resolve the contradiction.) [Auto-corrected BenchmarkForm: MaximumOnly → MinimumOnly]

Related Benchmarks

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

1409 mg/kg Moderate
Production Forestry · Pristine Reference
Point Active v1