Microbial Biomass Carbon (MBC)

AUS-ASC-LVG-SMB General Moderate confidence

Benchmark Value

No specific value — see range
Range: 300 to 1200 µg MBC/g soil
Optimal Range: 300 to 1200
Direction: Higher is desirable ↑
Form: OptimalRange

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 4 benchmarks together — the OptimalRange form drives the primary score, while 3 guard(s) constrain the result.

Contributing Benchmarks

OptimalRange Primary MinimumOnly Guard OptimalRange Guard MinimumOnly Guard

Evidence & Context

For Australian alpine and subalpine mineral soils (0-10 cm) under best-practice management demonstrating high environmental health, a reference MBC range of approximately 300 µg MBC/g soil (representing the lower end of moderate health) to 1200 µg MBC/g soil (indicative of high health, approaching the Austrian benchmark) appears defensible.

Metric Definition:

Microbial Biomass Carbon (MBC) in soil, measured in micrograms of microbial carbon per gram of soil at 0-10 cm depth.

Benchmark Definition:

This benchmark defines the healthy range of Microbial Biomass Carbon in Australian alpine and subalpine mineral soils under sustainable grazing, indicating good soil microbial activity and environmental health.

Justification:

The range is derived from synthesis of international alpine data, Australian grazing system data, and soil organic carbon percentages, representing a scientifically defensible reference for healthy alpine/subalpine pastures.

Sources (2)

Preview of Microbial Biomass - Qld | Fact Sheets | soilquality.org.au
Microbial Biomass - Qld | Fact Sheets | soilquality.org.au GreyLiterature

Global negative effects of nitrogen deposition on soil microbes - PMC, accessed July 31, 2025

View Source
Preview of www.zobodat.at, accessed on June 5, 2025
www.zobodat.at, accessed on June 5, 2025

www.zobodat.at

View Source

Supporting Sources (9)

Additional references from the underlying research that informed this benchmark.

Preview of Carbon Cycling in Sub-alpine Ecosystems
Carbon Cycling in Sub-alpine Ecosystems
Contextual Support GreyLiterature

The composition of organic phosphorus in soils of the Snowy Mountains region of south-eastern Australia - Semantic Scholar

View Source
Preview of Crop and Pasture Science - CSIRO PUBLISHING
Crop and Pasture Science - CSIRO PUBLISHING
Contextual Support Journal

Temperature response of soil respiration largely unaltered with experimental warming

View Source
Preview of Fire Effects on Soils and Restoration Strategies - National Academic Digital Library of Ethiopia, accessed May 10, 2026
Fire Effects on Soils and Restoration Strategies - National Academic Digital Library of Ethiopia, accessed May 10, 2026
Contextual Support Journal

Grover, S.E., et al. (2023). Nitrogen dynamics in alpine soils of south-eastern Australia. Soil Research, 61(6), 560-568. 1

View Source
Preview of Grazing Regulates Changes in Soil Microbial Communities in Plant-Soil Systems - MDPI
Grazing Regulates Changes in Soil Microbial Communities in Plant-Soil Systems - MDPI
Contextual Support Journal

Drought decreases incorporation of recent plant photosynthate into soil food webs regardless of their trophic complexity - PMC, accessed May 10, 2026

View Source
Preview of Impacts of Agricultural Management Practices on Soil Health - NCBI, accessed May 11, 2025
Impacts of Agricultural Management Practices on Soil Health - NCBI, accessed May 11, 2025
Contextual Support

Impacts of Agricultural Management Practices on Soil Health - NCBI, accessed August 28, 2025

View Source
Preview of Local Land Services
Local Land Services
Contextual Support Government

Microbial Biomass Carbon - 0 - 10cm | Victoria | Examine ...

View Source
Preview of Management-intensive Grazing (MiG) impacts on soil biological health - Semantic Scholar, accessed May 10, 2026
Management-intensive Grazing (MiG) impacts on soil biological health - Semantic Scholar, accessed May 10, 2026
Direct Evidence Journal

Management-intensive Grazing (MiG) impacts on soil biological health - Semantic Scholar, accessed May 10, 2026

View Source
Preview of Microbe Biomass in Relation to Organic Carbon and Clay in Soil - MDPI, accessed August 28, 2025,
Microbe Biomass in Relation to Organic Carbon and Clay in Soil - MDPI, accessed August 28, 2025,
Contextual Support Journal

Forest Soil Microbiomes: A Review of Key Research from 2003 to 2023 - MDPI

View Source
Preview of openresearch-repository.anu.edu.au, accessed on May 31, 2025
openresearch-repository.anu.edu.au, accessed on May 31, 2025
Contextual Support Journal

openresearch-repository.anu.edu.au, accessed on May 31, 2025,

View Source

Context

  • Region Australia
  • Biome Alpine and Subalpine Complex
  • Land Use Livestock Grazing & Pasture
  • Assessment Conservation Target
  • Evidence Type ReferenceCondition

Lifecycle

  • Status Active
  • Version 1
  • Effective From 3 Jun 2026

Notes

No upper detrimental threshold — higher values are always better up to natural saturation. This range reflects the dynamic equilibrium of microbial activity under sustainable grazing, with values below 200-300 µg MBC/g soil indicating potential degradation and values above 1200 µg MBC/g soil approaching high-functioning European benchmarks.

Related Benchmarks

Other benchmarks in the AUS-ASC-LVG-SMB family.

300 µg MBC/g soil Moderate
Livestock Grazing & Pasture · Conservation Target
MinimumOnly Active v1