Microbial Biomass Carbon (MBC)

AUS-TSR-FOR-SMB General Moderate confidence

Benchmark Value

167 mg/kg

Direction: Higher is desirable ↑

Form: MinimumOnly

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 9 benchmarks together — the OptimalRange form drives the primary score, while 8 guard(s) constrain the result.

Contributing Benchmarks

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

Evidence & Context

Under certain intensive site preparation treatments, MBC in the 0–10 cm layer dropped to as low as 167 mg/kg.

Metric Definition:

Lower critical threshold of Microbial Biomass Carbon (MBC) in the 0–10 cm soil layer indicating compromised ecosystem function.

Benchmark Definition:

This benchmark represents the critical lower threshold of Microbial Biomass Carbon in tropical and subtropical rainforest production forestry soils, below which soil biological function is severely compromised.

Justification:

Represents a severe decline from native forest baseline and best-practice plantation benchmark, indicating functional impairment.

Sources (1)

Preview of Variation in soil microbial biomass in the dry tropics: impact of land-use change, accessed on June 7, 2025,

Variation in soil microbial biomass in the dry tropics: impact of land-use change, accessed on June 7, 2025, Journal

Soil microbial biomass during the early establishment of hoop pine ...

View Source

Supporting Sources (4)

Additional references from the underlying research that informed this benchmark.

A meta-analysis of soil microbial biomass responses to forest disturbances - PMC, accessed August 28, 2025,

Contextual Support Journal

Selective logging impacts on soil microbial communities and functioning in Bornean tropical forest - Frontiers, accessed August 10, 2025

View Source

ORGANIC CARBON IN FORESTED SANDY SOILS: PROPERTIES, PROCESSES, AND THE IMPACT OF FOREST MANAGEMENT - Scion

Contextual Support Journal

ORGANIC CARBON IN FORESTED SANDY SOILS: PROPERTIES, PROCESSES, AND THE IMPACT OF FOREST MANAGEMENT - Scion, accessed July 19, 2025

View Source

ResearchOnline@JCU - James Cook University, accessed on June 7, 2025

Contextual Support Journal

Variation in soil microbial biomass in the dry tropics: impact of land-use change

View Source

Preview of Soil carbon and nutrient pools, microbial properties and gross nitrogen transformations in adjacent natural forest and hoop pine plantations of subtropical Australia

Soil carbon and nutrient pools, microbial properties and gross nitrogen transformations in adjacent natural forest and hoop pine plantations of subtropical Australia

Direct Evidence Journal

Soil carbon and nutrient pools, microbial properties and gross nitrogen transformations in adjacent natural forest and hoop pine plantations of subtropical Australia

View Source

Context

Region Australia
Biome Tropical & Subtropical Rainforests
Land Use Production Forestry
Assessment Not Stated
Evidence Type DegradationThreshold

Lifecycle

Status Active
Version 1
Effective From 5 Jun 2026

Notes

Inferred from disturbed second-rotation hoop pine plantations under intensive site preparation. No upper detrimental threshold — higher values are always better up to natural saturation. AssessmentContext defaulted to 'Not Stated' because the source document did not state one.

Related Benchmarks

Other benchmarks in the AUS-TSR-FOR-SMB family.