Microbial Biomass Carbon (MBC)

AUS-TGP-CON-SMB General Moderate confidence

Benchmark Value

160 mg/kg

Direction: Higher is desirable ↑

Form: MinimumOnly

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 MinimumOnly Guard Point Guard

Evidence & Context

A decline of over 70% relative to the best-on-offer benchmark of 536 mg/kg can serve as a quantifiable "red flag." This would correspond to an MBC level below approximately 160 mg/kg.

Metric Definition:

Lower critical threshold for Microbial Biomass Carbon (MBC) indicating severe depletion and ecosystem dysfunction.

Benchmark Definition:

This benchmark defines a lower critical threshold for Microbial Biomass Carbon (MBC) below which soil biological function is severely impaired, indicating significant ecological dysfunction in Temperate Grassy Woodlands & Plains under conservation management.

Justification:

Based on quantitative insight from a North Queensland eucalypt woodland study showing MBC levels in degrading sites were only 15–27% of control sites, indicating severe ecological impairment.

Sources (1)

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 Journal

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

View Source

Supporting Sources (3)

Additional references from the underlying research that informed this benchmark.

A global analysis of soil microbial biomass carbon, nitrogen and phosphorus in terrestrial ecosystems

Direct Evidence Journal

A global analysis of soil microbial biomass carbon, nitrogen and phosphorus in terrestrial ecosystems

View Source

Microbial biomass and microbial biodiversity in some soils from New South Wales, Australia - CSIRO PUBLISHING | Soil Research

Contextual Support Journal

Microbial biomass and microbial biodiversity in some soils from New South Wales, Australia - CSIRO PUBLISHING | Soil Research, accessed August 12, 2025

View Source

Preview of Restoring ecological function in temperate grassy woodlands: Manipulating soil nutrients, exotic annuals and native perennial grasses through carbon supplements and spring burns | Request PDF - ResearchGate, accessed May 12, 2025

Restoring ecological function in temperate grassy woodlands: Manipulating soil nutrients, exotic annuals and native perennial grasses through carbon supplements and spring burns | Request PDF - ResearchGate, accessed May 12, 2025

Direct Evidence GreyLiterature

Increasing and declining native species in urban remnant grasslands respond differently to nitrogen addition and disturbance

View Source

Context

Region Australia
Biome Temperate Grassy Woodlands & Plains
Land Use Conservation / Protected Natural Areas
Assessment Conservation Target
Evidence Type DegradationThreshold

Lifecycle

Status Active
Version 1
Effective From 3 Jun 2026

Notes

Represents a state of significant ecological dysfunction driven by severe lack of labile carbon inputs due to clearing, cultivation, or overgrazing. Nutrient cycling compromised, poor soil structure, low resilience.

Related Benchmarks

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