Microbial Biomass Carbon (MBC)

AUS-AIF-CON-SMB General Moderate confidence

Benchmark Value

200 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.

Evidence & Context

The MBC values observed in the longest-unflooded sites (>8 years) in the Baldwin et al. (2013) study, which clustered around 100 - 200 mg/kg, represent a system in a deep 'bust' phase.

Metric Definition:

Microbial Biomass Carbon (MBC) concentration in soil indicating the lower critical threshold below which soil biological function is severely compromised.

Benchmark Definition:

This benchmark marks the lower critical threshold of Microbial Biomass Carbon (MBC) below which soil microbial function is severely limited, indicating a degraded state in arid floodplain soils.

Justification:

Based on empirical data from long-unflooded sites representing a dormant microbial state and supported conceptually by dryland ecology research.

Sources (2)

Aridity thresholds of soil microbial metabolic indices along a 3,200 ...

Aridity thresholds of soil microbial metabolic indices along a 3,200 ...

View Source

Provisioning of bioavailable carbon between the wet and dry phases in a semi-arid floodplain

Provisioning of bioavailable carbon between the wet and dry phases in a semi-arid floodplain

View Source

Supporting Sources (12)

Additional references from the underlying research that informed this benchmark.

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

Direct Evidence Journal

Lake Eyre Basin Synthesis Report - Queensland Environment Department, accessed July 19, 2025

View Source

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 | Request PDF - ResearchGate

View Source

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

Contextual Support GreyLiterature

fertile clay soil: Topics by Science.gov

View Source

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

Contextual Support Journal

final repport - Department of Primary Industries, Queensland

View Source

Interpreting Microbial Biomass Carbon | Fact Sheets | soilquality.org.au, accessed August 28, 2025,

Contextual Support GreyLiterature

Interpreting Microbial Biomass Carbon | Fact Sheets | soilquality.org.au

View Source

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

View Source

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

View Source

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

View Source

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

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

View Source

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

View Source

Context

Region Australia
Biome Arid Inland Floodplains & Ephemeral River Systems
Land Use Conservation / Protected Natural Areas
Assessment Pristine Reference
Evidence Type DegradationThreshold

Lifecycle

Status Active
Version 1
Effective From 5 Jun 2026

Notes

Values below this threshold indicate a loss of biological resilience and severely impaired ecosystem function.

Related Benchmarks

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