Microbial Biomass Carbon (MBC)

AUS-AIF-LVG-SMB General High confidence

Benchmark Value

1600 mg/kg
Range: 600 to 1600 mg/kg
Optimal Range: 600 to 1600
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 11 benchmarks together — the OptimalRange form drives the primary score, while 10 guard(s) constrain the result.

Evidence & Context

This post-recession value of 1600 mg/kg represents a system operating at its peak functional capacity.

Metric Definition:

Microbial Biomass Carbon (MBC) is a measure of the total carbon held within the living cells of microorganisms, primarily bacteria and fungi, in a given mass of soil.

Benchmark Definition:

This benchmark represents the peak functional state of microbial biomass carbon in Australia's arid inland floodplains under best-practice livestock grazing, indicating a fully functioning and resilient ecosystem.

Justification:

It is the highest field-measured MBC value found in the literature directly situated within the target biome and reflects the system's maximum potential to support a large, thriving microbial community when resources are not limited.

Sources (1)

Preview of Loss of Soil Carbon Associated with a Short-Duration Flood in a Semi-Arid Lowland River Floodplain Forest
Loss of Soil Carbon Associated with a Short-Duration Flood in a Semi-Arid Lowland River Floodplain Forest Journal

Loss of Soil Carbon Associated with a Short-Duration Flood in a Semi-Arid Lowland River Floodplain Forest

View Source

Supporting Sources (2)

Additional references from the underlying research that informed this benchmark.

Preview of grazing impacts on the spatial distribution of soil microbial biomass around tussock grasses in a tropical grassland - Publication : USDA ARS
grazing impacts on the spatial distribution of soil microbial biomass around tussock grasses in a tropical grassland - Publication : USDA ARS
Direct Evidence Journal

Soil microbial community structure is unaltered by grazing intensity and plant species richness in a temperate grassland steppe in northern China - Publication : USDA ARS, accessed July 29, 2025

View Source
Preview of Microbial biomass and microbial biodiversity in some soils from New South Wales, Australia | Request PDF - ResearchGate
Microbial biomass and microbial biodiversity in some soils from New South Wales, Australia | Request PDF - ResearchGate
Contextual Support Journal

Microbial biomass and microbial biodiversity in some soils from New South Wales, Australia | Request PDF - ResearchGate, accessed July 8, 2025

View Source

Context

  • Region Australia
  • Biome Arid Inland Floodplains & Ephemeral River Systems
  • Land Use Livestock Grazing & Pasture
  • Assessment Pristine Reference
  • Evidence Type ReferenceCondition

Lifecycle

  • Status Superseded
  • Version 1
  • Effective From 18 Mar 2026
  • Effective To 19 Mar 2026

Notes

No upper detrimental threshold — higher values are always better up to natural saturation. The optimal range reflects ecosystem capacity to fluctuate between ~600 and 1600+ mg/kg depending on moisture conditions.