Microbial Biomass Carbon (MBC)

AUS-AMR-LVG-SMB General Moderate confidence

Benchmark Value

280 mg/kg
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 13 benchmarks together — the OptimalRange form drives the primary score, while 12 guard(s) constrain the result.

Contributing Benchmarks

OptimalRange Primary Point Guard OptimalRange Guard MinimumOnly Guard Point Guard MinimumOnly Guard OptimalRange Guard Point Guard OptimalRange Guard MinimumOnly Guard Point Guard OptimalRange Guard Point Guard

Evidence & Context

Based on this transparent, evidence-based derivation, the recommended benchmark for Microbial Biomass Carbon is established. This value represents the best-on-offer condition for a high-functioning site under sustainable grazing management within Australia's Arid Mountain Ranges & Uplands biome.

Metric Definition:

Microbial Biomass Carbon (MBC) is the mass of carbon contained within the living soil microbial community, primarily bacteria and fungi, serving as a sensitive bio-indicator of soil health and ecosystem function.

Benchmark Definition:

This benchmark represents a point value for Microbial Biomass Carbon (MBC) in soils under sustainable grazing in Australia's Arid Mountain Ranges & Uplands. It reflects a high-functioning soil microbial community carbon mass derived from best-practice soil organic carbon values and carbon fraction ratios.

Justification:

The benchmark is derived from a best-practice Soil Organic Carbon (SOC) value of 12,600 mg/kg for perennial grass cover in semi-arid rangelands using Australian pasture-derived carbon fraction ratios. Confidence is moderate due to derivation from proxy data rather than direct measurement.

Sources (3)

Preview of Crop and Pasture Science - CSIRO PUBLISHING
Crop and Pasture Science - CSIRO PUBLISHING Journal

Temperature response of soil respiration largely unaltered with experimental warming

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

Managing cattle grazing intensity: effects on soil organic matter and soil nitrogen, accessed July 23, 2025

View Source
Preview of The relationship between soil organic carbon and soil surface characteristics in the semi-arid rangelands of southern Australia
The relationship between soil organic carbon and soil surface characteristics in the semi-arid rangelands of southern Australia Journal

The relationship between soil organic carbon and soil surface characteristics in the semi-arid rangelands of southern Australia

View Source

Supporting Sources (1)

Additional references from the underlying research that informed this benchmark.

Preview of The relationship between soil organic carbon and soil surface ...
The relationship between soil organic carbon and soil surface ...
Direct Evidence Journal

The relationship between soil organic carbon and soil surface characteristics in the semi-arid rangelands of southern Australia | Request PDF - ResearchGate

View Source

Context

  • Region Australia
  • Biome Arid Mountain Ranges & Uplands
  • Land Use Livestock Grazing & Pasture
  • Assessment Not Stated
  • Evidence Type TargetCondition

Lifecycle

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

Notes

Lower Critical Threshold is a functional state of microbial community collapse, not a numeric value. No upper detrimental threshold exists; the upper boundary is a natural saturation point. The benchmark value lies within an optimal functional range under sustainable grazing. AssessmentContext defaulted to 'Not Stated' because the source document did not state one.