Microbial Biomass Carbon (MBC)

AUS-AKW-LVG-SMB General Moderate confidence

Benchmark Value

150 mg/kg
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 4 benchmarks together — the OptimalRange form drives the primary score, while 3 guard(s) constrain the result.

Contributing Benchmarks

OptimalRange Primary MinimumOnly Guard OptimalRange Guard MinimumOnly Guard

Evidence & Context

Lower Critical Threshold: < 150 mg C/kg. Values below this threshold indicate significant impairment of soil biological function and serve as a red flag for ecosystem stress or degradation.

Metric Definition:

Microbial Biomass Carbon (MBC)

Benchmark Definition:

This benchmark sets the minimum microbial biomass carbon level below which soil biological function is significantly impaired, indicating ecosystem stress in arid karstic woodlands and shrublands under conservation-focused grazing.

Justification:

Derived from data showing MBC levels of 100-150 mg/kg in managed but sub-optimal agricultural systems in similar climates and lower values in severely degraded systems.

Sources (7)

Preview of Characterization of Microbial Carbon Metabolism in Karst Soils from Citrus Orchards and Analysis of Its Environmental Drivers - MDPI
Characterization of Microbial Carbon Metabolism in Karst Soils from Citrus Orchards and Analysis of Its Environmental Drivers - MDPI Journal

Characterization of Microbial Carbon Metabolism in Karst Soils from Citrus Orchards and Analysis of Its Environmental Drivers - MDPI

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, GreyLiterature

www.soilquality.org.au

View Source
Preview of Microbial biomass carbon and some soil properties as influenced by long-term sodic-water irrigation, gypsum, and organic amendments - CSIRO Publishing
Microbial biomass carbon and some soil properties as influenced by long-term sodic-water irrigation, gypsum, and organic amendments - CSIRO Publishing Journal

Microbial biomass carbon and some soil properties as influenced by long-term sodic-water irrigation, gypsum, and organic amendments - CSIRO Publishing

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, Journal

Synthesis of Australian Rangeland SOC Data from CSIRO, Peer-Reviewed Literature, and Government Reports

View Source
Preview of Soil carbon sequestration in rangelands: A critical review of the impacts of major management strategies - ResearchGate, accessed August 5, 2025,
Soil carbon sequestration in rangelands: A critical review of the impacts of major management strategies - ResearchGate, accessed August 5, 2025, GreyLiterature

Soil carbon sequestration in rangelands: A critical review of the impacts of major management strategies - ResearchGate, accessed July 23, 2025

View Source
Preview of Soil Microbial Biomass Carbon and Nitrogen in Himalayan Rangeland of Eastern Nepal: A Comparison between Grazed and Non-grazed Rangelands - ResearchGate
Soil Microbial Biomass Carbon and Nitrogen in Himalayan Rangeland of Eastern Nepal: A Comparison between Grazed and Non-grazed Rangelands - ResearchGate Journal

Soil Microbial Biomass Carbon and Nitrogen in Himalayan Rangeland of Eastern Nepal: A Comparison between Grazed and Non-grazed Rangelands - ResearchGate

View Source
Preview of Soil microbial biomass—Interpretation and consideration for soil monitoring - ResearchGate, accessed August 5, 2025,
Soil microbial biomass—Interpretation and consideration for soil monitoring - ResearchGate, accessed August 5, 2025, Journal

Soil microbial biomass—Interpretation and consideration for soil monitoring - ResearchGate

View Source

Context

  • Region Australia
  • Biome Arid Karstic Woodlands & Shrublands
  • Land Use Livestock Grazing & Pasture
  • Assessment Conservation Target
  • Vegetation Woodland
  • Evidence Type DegradationThreshold

Lifecycle

  • Status Active
  • Version 1
  • Effective From 4 Jun 2026

Notes

Values below this threshold indicate significant impairment of soil biological function.

Related Benchmarks

Other benchmarks in the AUS-AKW-LVG-SMB family.

— mg/kg Moderate
Livestock Grazing & Pasture · Conservation Target · Woodland
OptimalRange Active v1