Microbial Biomass Carbon (MBC)

AUS-AIF-CON-SMB General Moderate confidence

Benchmark Value

No specific value — see range
Range: 400 to 700 mg/kg
Thresholds: Lower: 200, Upper: —
Optimal Range: 400 to 700
Direction: Higher is desirable ↑
Form: OptimalRange

Scoring Curve

Scoring curve unavailable

The scoring engine could not generate a curve for this benchmark context. The primary form is CompositeFramework, but the benchmark data may be missing required fields (e.g., optimal range bounds for an OptimalRange benchmark). This is typically a data quality issue in the benchmark pipeline.

Contributing Benchmarks

CompositeFramework Primary Point Guard LowerThreshold Guard Point Guard Point Guard OptimalRange Guard LowerThreshold Guard Point Guard OptimalRange Guard OptimalRange Guard

Evidence & Context

The reference value represents the peak functional state ('boom' phase) observed in recently inundated floodplain soils (0-10 cm depth) of a semi-arid Australian river system.

Metric Definition:

Microbial Biomass Carbon (MBC) represents the mass of carbon contained within the living component of soil organic matter—primarily bacteria and fungi.

Benchmark Definition:

Microbial Biomass Carbon (MBC) is the mass of carbon in living soil microorganisms, primarily bacteria and fungi, reflecting the peak functional state in semi-arid floodplain soils during natural flood-pulse dynamics.

Justification:

The benchmark is derived from direct, quantitative field measurements of MBC in a highly relevant ecosystem: a semi-arid Australian floodplain, capturing the pulse-driven dynamics central to the biome's function.

Sources (1)

Preview of (PDF) Provisioning of bioavailable carbon between the wet and dry ...
(PDF) Provisioning of bioavailable carbon between the wet and dry ... Journal

Lake Eyre Basin Synthesis Report - Queensland Environment Department, accessed July 22, 2025

View Source

Supporting Sources (12)

Additional references from the underlying research that informed this benchmark.

Preview of ALLOCHTHONOUS CARBON LOADS AND POTENTIAL ... - La Trobe, accessed July 22, 2025,
ALLOCHTHONOUS CARBON LOADS AND POTENTIAL ... - La Trobe, accessed July 22, 2025,
Contextual Support Journal

Australian dryland soils are acidic and nutrient-depleted, and have unique microbial communities compared with other drylands - PMC, accessed July 22, 2025

View Source
Preview of Aridity thresholds of soil microbial metabolic indices along a 3,200 ...
Aridity thresholds of soil microbial metabolic indices along a 3,200 ...
Contextual Support

Aridity thresholds of soil microbial metabolic indices along a 3,200 ..., accessed July 22, 2025,

View Source
Preview of fertile clay soil: Topics by Science.gov, accessed July 22, 2025,
fertile clay soil: Topics by Science.gov, accessed July 22, 2025,
Contextual Support GreyLiterature

fertile clay soil: Topics by Science.gov, accessed July 22, 2025,

View Source
Preview of final repport - Department of Primary Industries, Queensland, accessed July 22, 2025,
final repport - Department of Primary Industries, Queensland, accessed July 22, 2025,
Contextual Support Journal

final repport - Department of Primary Industries, Queensland, accessed July 22, 2025,

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 Lake Eyre Basin Rivers Assessment Implementation Plan Project - ResearchGate, accessed July 22, 2025,
Lake Eyre Basin Rivers Assessment Implementation Plan Project - ResearchGate, accessed July 22, 2025,
Contextual Support

Cycling of phosphorus in grazing systems - NSW Department of Primary Industries, accessed July 17, 2025,

View Source
Preview of Lake Eyre Basin: its rivers and catchments. Strategic Plan. - DCCEEW, accessed July 21, 2025,
Lake Eyre Basin: its rivers and catchments. Strategic Plan. - DCCEEW, accessed July 21, 2025,
Contextual Support Journal

Lake Eyre Basin: its rivers and catchments. Strategic Plan. - DCCEEW, accessed July 22, 2025,

View Source
Preview of Protected Areas: Buffering nature against climate change - PreventionWeb.net, accessed July 21, 2025,
Protected Areas: Buffering nature against climate change - PreventionWeb.net, accessed July 21, 2025,
Contextual Support Journal

Protected Areas: Buffering nature against climate change - PreventionWeb.net, accessed July 22, 2025

View Source
Preview of Response of Soil Microbial Communities in Extreme Arid Deserts to Different Long-Term Management Methods - MDPI, accessed July 22, 2025,
Response of Soil Microbial Communities in Extreme Arid Deserts to Different Long-Term Management Methods - MDPI, accessed July 22, 2025,
Contextual Support Journal

Response of Soil Microbial Communities in Extreme Arid Deserts to Different Long-Term Management Methods - MDPI, accessed July 22, 2025,

View Source
Preview of Sources of organic carbon supporting the food web of an arid zone floodplain river | Request PDF - ResearchGate, accessed July 22, 2025,
Sources of organic carbon supporting the food web of an arid zone floodplain river | Request PDF - ResearchGate, accessed July 22, 2025,
Contextual Support Journal

Sources of organic carbon supporting the food web of an arid zone floodplain river | Request PDF - ResearchGate, accessed July 22, 2025,

View Source
Preview of The relevance of wetland conservation in arid regions: A re-examination of vanishing communities in the American Southwest | Request PDF - ResearchGate, accessed July 22, 2025,
The relevance of wetland conservation in arid regions: A re-examination of vanishing communities in the American Southwest | Request PDF - ResearchGate, accessed July 22, 2025,
Contextual Support Journal

The relevance of wetland conservation in arid regions: A re-examination of vanishing communities in the American Southwest | Request PDF - ResearchGate, accessed July 22, 2025,

View Source
Preview of Wetlands Strategy for South Australia - Department for Environment and Water, accessed July 22, 2025,
Wetlands Strategy for South Australia - Department for Environment and Water, accessed July 22, 2025,
Contextual Support Journal

Wetlands Strategy for South Australia - Department for Environment and Water, accessed July 22, 2025,

View Source

Context

  • Region Australia
  • Biome Arid Inland Floodplains & Ephemeral River Systems
  • Land Use Conservation / Protected Natural Areas
  • Assessment Conservation Target
  • Evidence Type ReferenceCondition

Lifecycle

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

Notes

Lower Critical Threshold: 200 mg/kg. No upper detrimental threshold — higher values are always better up to natural saturation. The benchmark reflects the peak functional state during the 'boom' phase after flooding. RangeFixup applied 2026-03-21 22:21 UTC: LowerBound: 400 → 200; OptimalRangeLow: 200 → 400 [Migration] Original wider evidence range: 200 – 700 (retained OptimalRange: 400 – 700)

Related Benchmarks

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

200 mg/kg Moderate
Conservation / Protected Natural Areas · Conservation Target
LowerThreshold Active v1