Microbial Biomass Carbon (MBC)

AUS-TDG-LVG-SMB General Moderate confidence

Benchmark Value

No specific value — see range

Range: 150 to 250 mg/kg

Thresholds: Lower: 150, Upper: —

Optimal Range: 150 to 250

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 11 benchmarks together — the OptimalRange form drives the primary score, while 10 guard(s) constrain the result.

Contributing Benchmarks

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

Evidence & Context

Based on these considerations, a lower critical threshold for MBC in Australian Temperate Dry Woodlands & Native Grasslands under grazing is estimated to be in the range of 150-250 mg/kg.

Metric Definition:

Lower critical threshold of Microbial Biomass Carbon (MBC) below which essential soil ecological functions are significantly impaired.

Benchmark Definition:

This benchmark defines the lower critical threshold of microbial biomass carbon in soil, below which soil ecological functions are significantly impaired in Temperate Dry Woodlands & Native Grasslands under grazing.

Justification:

Inferred from multiple lines of evidence including low microbial group biomass, low SOC, and soil acidity effects.

Sources (1)

Preview of Farming systems can affect soil biology, soil pathogens and system resilience (GRDC Update Paper, Pampas Site Data)

Farming systems can affect soil biology, soil pathogens and system resilience (GRDC Update Paper, Pampas Site Data)

Farming systems can affect soil biology, soil pathogens and system resilience (GRDC Update Paper, Pampas Site Data)

Supporting Sources (18)

Additional references from the underlying research that informed this benchmark.

Preview of Assessing the response of soil carbon in Australia to changing inputs and climate using a consistent modelling framework - BG

Assessing the response of soil carbon in Australia to changing inputs and climate using a consistent modelling framework - BG

Contextual Support Journal

Assessing the response of soil carbon in Australia to changing inputs and climate using a consistent modelling framework - BG

Preview of Carbon Pool Dynamic and Soil Microbial Respiration Affected by ...

Carbon Pool Dynamic and Soil Microbial Respiration Affected by ...

Contextual Support Journal

Carbon Pool Dynamic and Soil Microbial Respiration Affected by Land Use Alteration: A Case Study in Humid Subtropical Area - MDPI, accessed July 28, 2025,

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

Preview of Declining soil pH reduces microbial biomass-driven soil multifunctionality - Institute for Environmental Genomics

Declining soil pH reduces microbial biomass-driven soil multifunctionality - Institute for Environmental Genomics

Contextual Support Journal

Declining soil pH reduces microbial biomass-driven soil multifunctionality - Institute for Environmental Genomics

Preview of Do regenerative grazing management practices improve vegetation and soil health in grazed rangelands? Preliminary insights from a space-for-time study in the Great Barrier Reef catchments, Australia - CSIRO Publishing, accessed August 5, 2025,

Do regenerative grazing management practices improve vegetation and soil health in grazed rangelands? Preliminary insights from a space-for-time study in the Great Barrier Reef catchments, Australia - CSIRO Publishing, accessed August 5, 2025,

Contextual Support

Ludwig, J.A., Bastin, G.N., Chewings, V.H., Eager, R.W., and Liedloff, A.C. (2005). Clearing savannas for use as rangelands in Queensland: Altered landscapes and water-erosion processes. Rangeland Journal, 27(2), 135-149.

Preview of Effects of heavy metals on soil microbial biomass carbon - ResearchGate, accessed on June 7, 2025,

Effects of heavy metals on soil microbial biomass carbon - ResearchGate, accessed on June 7, 2025,

Contextual Support Journal

Effects of heavy metals on soil microbial biomass carbon - ResearchGate

Preview of Grazing Impacts on Soil Carbon and Microbial Communities in a Mixed-Grass Ecosystem - USDA ARS

Grazing Impacts on Soil Carbon and Microbial Communities in a Mixed-Grass Ecosystem - USDA ARS

Contextual Support Journal

Grazing Impacts on Soil Carbon and Microbial Communities in a Mixed-Grass Ecosystem - USDA ARS, accessed August 9, 2025

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

Preview of HOW TO MEASURE AND INTERPRET RESULTS IN RELATION TO SOIL ORGANIC CARBON - Grains Research and Development Corporation (GRDC), accessed August 5, 2025,

HOW TO MEASURE AND INTERPRET RESULTS IN RELATION TO SOIL ORGANIC CARBON - Grains Research and Development Corporation (GRDC), accessed August 5, 2025,

Contextual Support GreyLiterature

HOW TO MEASURE AND INTERPRET RESULTS IN RELATION TO SOIL ORGANIC CARBON - Grains Research and Development Corporation (GRDC)

Preview of Impact of Cropping Systems on Macronutrient Distribution and Microbial Biomass in Drought Affected Soils - EGUsphere

Impact of Cropping Systems on Macronutrient Distribution and Microbial Biomass in Drought Affected Soils - EGUsphere

Contextual Support GreyLiterature

GRDC Groundcover Article: National blueprint to standardise soil health across Australian agriculture - The Waite, accessed July 8, 2025

Preview of Impact of Grazing on Soil Carbon and Microbial Biomass in Typical Steppe and Desert Steppe of Inner Mongolia | PLOS One

Impact of Grazing on Soil Carbon and Microbial Biomass in Typical Steppe and Desert Steppe of Inner Mongolia | PLOS One

Contextual Support Journal

Impact of Grazing on Soil Carbon and Microbial Biomass in Typical Steppe and Desert Steppe of Inner Mongolia | PLOS One

Preview of Impacts of Rotational Grazing on Soil Carbon in Native Grass-Based ..., accessed August 5, 2025,

Impacts of Rotational Grazing on Soil Carbon in Native Grass-Based ..., accessed August 5, 2025,

Contextual Support Journal

Impacts of Rotational Grazing on Soil Carbon in Native Grass-Based Pastures in Southern Australia | PLOS One - Research journals

Preview of Impacts of Rotational Grazing on Soil Carbon in Native Grass-Based Pastures in Southern Australia - ResearchGate, accessed August 5, 2025,

Impacts of Rotational Grazing on Soil Carbon in Native Grass-Based Pastures in Southern Australia - ResearchGate, accessed August 5, 2025,

Contextual Support Journal

Grazing management for soil carbon in Australia: A review - ResearchGate

Preview of Removing Grazing Pressure from a Native Pasture Decreases Soil Organic Carbon in Southern New South Wales, Australia - ResearchGate

Removing Grazing Pressure from a Native Pasture Decreases Soil Organic Carbon in Southern New South Wales, Australia - ResearchGate

Contextual Support

Removing Grazing Pressure from a Native Pasture Decreases Soil Organic Carbon in Southern New South Wales, Australia - ResearchGate

Preview of Soil Carbon Pool as Influenced by Soil Microbial Activity—An Overview, accessed on June 7, 2025,

Soil Carbon Pool as Influenced by Soil Microbial Activity—An Overview, accessed on June 7, 2025,

Contextual Support Journal

Soil Carbon Pool as Influenced by Soil Microbial Activity—An Overview

Preview of Soil microbial biomass—what do the numbers really mean? - ResearchGate, accessed August 28, 2025,

Soil microbial biomass—what do the numbers really mean? - ResearchGate, accessed August 28, 2025,

Contextual Support

Soil microbial biomass carbon and CO2? - ResearchGate, accessed July 18, 2025,

Preview of Soil microbial carbon and activity along with land use and geographic gradients

Soil microbial carbon and activity along with land use and geographic gradients

Contextual Support

Soil microbial carbon and activity along with land use and geographic gradients

Preview of Soil quality and health in pasture systems - Holbrook Landcare Network

Soil quality and health in pasture systems - Holbrook Landcare Network

Contextual Support Journal

Soil quality and health in pasture systems - Holbrook Landcare ...

Context

Region Australia
Biome Temperate Dry Woodlands & Native Grasslands
Land Use Livestock Grazing & Pasture
Assessment Pristine Reference
Evidence Type DegradationThreshold

Lifecycle

Status Superseded
Version 1
Effective From 17 Mar 2026
Effective To 17 Mar 2026

Notes

Levels below this range suggest significantly compromised ecological function, especially when combined with other stressors.

Related Benchmarks

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