Microbial Biomass Carbon (MBC)

AUS-AIF-FOR-SMB General Low confidence

Benchmark Value

220 mg/kg
Range: 32 to 220 mg/kg
Thresholds: Lower: 32, Upper: —
Optimal Range: 32 to 220
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 derived benchmark for a high-health state is 220 mg/kg.

Metric Definition:

Microbial Biomass Carbon (MBC) is a measure of the carbon contained within the living component of soil organic matter (SOM), predominantly comprising bacteria and fungi.

Benchmark Definition:

Microbial Biomass Carbon (MBC) represents the carbon in living soil organisms, mainly bacteria and fungi, indicating soil health in arid floodplain production forestry systems. A high-health benchmark is set at 220 mg/kg, reflecting sustainable forestry and floodplain productivity.

Justification:

The benchmark is derived from an evidence-based floor from restored semi-arid systems (~97 mg/kg) and adjusted upwards for floodplain productivity and sustainable forestry practices. Confidence is low due to derivation from extrapolation rather than direct measurement.

Sources (1)

Preview of Enhancing soil organic carbon, particulate organic carbon and microbial biomass in semi-arid rangeland using pasture enclosures
Enhancing soil organic carbon, particulate organic carbon and microbial biomass in semi-arid rangeland using pasture enclosures

Enhancing soil organic carbon, particulate organic carbon and microbial biomass in semi-arid rangeland using pasture enclosures

View Source

Supporting Sources (29)

Additional references from the underlying research that informed this benchmark.

Preview of A scenario calculator for effects of grazing land management on carbon stocks in Australian rangelands | Request PDF - ResearchGate, accessed August 3, 2025
A scenario calculator for effects of grazing land management on carbon stocks in Australian rangelands | Request PDF - ResearchGate, accessed August 3, 2025
Contextual Support Journal

Topsoil microbial biomass carbon pool and the microbial quotient under distinct land-use types across China, accessed July 20, 2025

View Source
Preview of ARID LANDS OF AUSTRALIA - Open Research Repository
ARID LANDS OF AUSTRALIA - Open Research Repository
Contextual Support Journal

ARID LANDS OF AUSTRALIA - Open Research Repository

View Source
Preview of ARID LANDS OF AUSTRALIA - Open Research Repository, accessed July 15, 2025,
ARID LANDS OF AUSTRALIA - Open Research Repository, accessed July 15, 2025,
Contextual Support Journal

ARID LANDS OF AUSTRALIA - ANU Open Research, accessed July 22, 2025

View Source
Preview of Arid Landscapes: Assessment of Street Tree Performance at Roxby ...
Arid Landscapes: Assessment of Street Tree Performance at Roxby ...
Contextual Support GreyLiterature

Arid Landscapes: Assessment of Street Tree Performance at Roxby Downs - Treenet

View Source
Preview of Australian National Soil Archive - CSIRO
Australian National Soil Archive - CSIRO
Contextual Support Government

Categories - soil carbon - CSIRO Data Access Portal

View Source
Preview of Carbon farming - Wikipedia
Carbon farming - Wikipedia
Contextual Support GreyLiterature

Carbon farming - Wikipedia

View Source
Preview of Description | Environment, land and water - Queensland Government
Description | Environment, land and water - Queensland Government
Contextual Support Journal

Soil Carbon Saturation: What Do We Really Know? - PMC - PubMed Central, accessed August 28, 2025,

View Source
Preview of Drivers and trends of global soil microbial carbon over two decades - PMC
Drivers and trends of global soil microbial carbon over two decades - PMC
Contextual Support Journal

Drivers and trends of global soil microbial carbon over two decades - PMC

View Source
Preview of Ecosystem Processes – Environmental Data Collection Methods - TERN Australia
Ecosystem Processes – Environmental Data Collection Methods - TERN Australia
Contextual Support Government

TERN Surveillance monitoring program: Soil vis-NIR spectral library with accompanying soil measurement data for 367 specimens - CSIRO Data Access Portal, accessed July 17, 2025,

View Source
Preview of Estimating the attainable soil organic carbon deficit in the soil fine fraction to inform feasible storage targets and de-risk carbon farming decisions - CSIRO PUBLISHING | Soil Research
Estimating the attainable soil organic carbon deficit in the soil fine fraction to inform feasible storage targets and de-risk carbon farming decisions - CSIRO PUBLISHING | Soil Research
Contextual Support Government

3- Build and maintain soil nutrients to improve soil fertility and health in all pasture zones

View Source
Preview of Forests and climate change mitigation in Australia - J-Stage
Forests and climate change mitigation in Australia - J-Stage
Contextual Support Journal

Forests and climate change mitigation in Australia - J-Stage

View Source
Preview of Impact of agricultural land use on distribution of microbial biomass and activity within soil aggregates - ResearchGate
Impact of agricultural land use on distribution of microbial biomass and activity within soil aggregates - ResearchGate
Contextual Support Journal

Plant responses to livestock grazing frequency in an Australian temperate grassland, accessed August 8, 2025,

View Source
Preview of Impact of Management Practices on Soil Organic Carbon Content and Microbial Diversity Under Semi-Arid Conditions - MDPI, accessed July 27, 2025,
Impact of Management Practices on Soil Organic Carbon Content and Microbial Diversity Under Semi-Arid Conditions - MDPI, accessed July 27, 2025,
Contextual Support Journal

Full article: Plant functional traits and soil microbial biomass in different vegetation zones on the Loess Plateau - Taylor & Francis Online

View Source
Preview of Increased microbial growth, biomass, and turnover drive soil organic carbon accumulation at higher plant diversity - PMC - PubMed Central
Increased microbial growth, biomass, and turnover drive soil organic carbon accumulation at higher plant diversity - PMC - PubMed Central
Contextual Support Journal

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

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 Limitations of soil microbial biomass carbon as an indicator of soil pollution in the field
Limitations of soil microbial biomass carbon as an indicator of soil pollution in the field
Contextual Support Journal

The Long-Term Effect of Biochar on Soil Microbial Abundance, Activity and Community Structure Is Overwritten by Land Management - Frontiers

View Source
Preview of Limitations of soil microbial biomass carbon as an indicator of soil pollution in the field
Limitations of soil microbial biomass carbon as an indicator of soil pollution in the field
Contextual Support Journal

Limitations of soil microbial biomass carbon as an indicator of soil pollution in the field

View Source
Preview of Microbe Biomass in Relation to Organic Carbon and Clay in Soil - MDPI, accessed August 28, 2025,
Microbe Biomass in Relation to Organic Carbon and Clay in Soil - MDPI, accessed August 28, 2025,
Contextual Support Journal

Trends in Microbial Community Composition and Function by Soil Depth - PMC

View Source
Preview of Microbial Biomass and Activity in Salt Affected Soils under Arid Conditions - ResearchGate
Microbial Biomass and Activity in Salt Affected Soils under Arid Conditions - ResearchGate
Contextual Support Journal

Microbial Biomass and Activity in Salt Affected Soils under Arid Conditions - ResearchGate

View Source
Preview of Microbial Biomass Carbon - NSW | Fact Sheets | soilquality.org.au, accessed August 5, 2025,
Microbial Biomass Carbon - NSW | Fact Sheets | soilquality.org.au, accessed August 5, 2025,
Contextual Support GreyLiterature

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

View Source
Preview of Recovery of surface soil properties of ecological interest after sheep ..., accessed July 20, 2025
Recovery of surface soil properties of ecological interest after sheep ..., accessed July 20, 2025
Contextual Support Journal

Microbial Biomass and Rhizosphere Soil Properties in Response to Heavy Metal-Contaminated Flooding - MDPI

View Source
Preview of Response of respiration and nutrient availability to drying and ... - BG
Response of respiration and nutrient availability to drying and ... - BG
Contextual Support Journal

Soil water and stable isotopes in the unsaturated zone profile � field observations and analysis | Request PDF - ResearchGate

View Source
Preview of Seed germination requirements of an Australian semi-arid floodplain Acacia species, Acacia stenophylla - CSIRO Publishing
Seed germination requirements of an Australian semi-arid floodplain Acacia species, Acacia stenophylla - CSIRO Publishing
Contextual Support Journal

Seed germination requirements of an Australian semi-arid floodplain Acacia species, Acacia stenophylla - CSIRO Publishing

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 Sources of organic carbon supporting the food web of an arid zone floodplain river - Griffith Research Online
Sources of organic carbon supporting the food web of an arid zone floodplain river - Griffith Research Online
Contextual Support Journal

Sources of organic carbon supporting the food web of an arid zone floodplain river - Griffith Research Online

View Source
Preview of Summary of the collections of arid soils from Australia. - ResearchGate
Summary of the collections of arid soils from Australia. - ResearchGate
Contextual Support GreyLiterature

Rehabilitation of Semiarid Landscapes in Australia. I. Restoring Productive Soil Patches | Request PDF - ResearchGate, accessed August 3, 2025

View Source
Preview of Survey of soil chemical properties across a landscape in the Namib Desert - ResearchGate
Survey of soil chemical properties across a landscape in the Namib Desert - ResearchGate
Contextual Support Journal

Survey of soil chemical properties across a landscape in the Namib Desert - ResearchGate

View Source
Preview of The Biogeography of Soil Bacteria in Australia Exhibits Greater Resistance to Climate Change Than Fungi - PubMed Central
The Biogeography of Soil Bacteria in Australia Exhibits Greater Resistance to Climate Change Than Fungi - PubMed Central
Contextual Support Journal

The Biogeography of Soil Bacteria in Australia Exhibits Greater Resistance to Climate Change Than Fungi - PubMed Central

View Source
Preview of The implications of brief floodplain inundation ... - CSIRO Publishing, accessed July 20, 2025
The implications of brief floodplain inundation ... - CSIRO Publishing, accessed July 20, 2025
Contextual Support Journal

The implications of brief floodplain inundation for local and landscape-scale ecosystem function in an intermittent Australian river - CSIRO Publishing

View Source

Context

  • Region Australia
  • Biome Arid Inland Floodplains & Ephemeral River Systems
  • Land Use Production Forestry
  • Assessment Pristine Reference
  • Evidence Type ReferenceCondition

Lifecycle

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

Notes

Lower Critical Threshold: 32 mg/kg. No upper detrimental threshold — higher values are always better up to natural saturation. The optimal range is dynamic depending on soil capacity and management.

Related Benchmarks

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

32 mg/kg Moderate
Production Forestry · Pristine Reference
LowerThreshold Active v1