Microbial Biomass Carbon (MBC)

AUS-TSR-FOR-SMB General High confidence

Benchmark Value

686 mg/kg

Range: 650 to 950 mg/kg

Optimal Range: 650 to 950

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

Contributing Benchmarks

OptimalRange Primary Point Guard Point Guard LowerThreshold Guard OptimalRange Guard

Evidence & Context

The analysis establishes a benchmark for Microbial Biomass Carbon (MBC) in Australian tropical and subtropical production forestry of 686 mg/kg for the 0–10 cm soil layer. This value is derived from a mature, 50-year-old hoop pine plantation and represents a scientifically defensible target for a high-health, stable, and sustainable managed forest ecosystem.

Metric Definition:

Microbial Biomass Carbon (MBC) in the 0–10 cm soil layer of production forestry in Australian tropical and subtropical rainforests

Benchmark Definition:

Benchmark value representing a high-health, stable, and sustainable managed forest ecosystem under production forestry land use.

Justification:

Selected as the most credible and defensible benchmark for best-practice production forestry based on a mature, 50-year-old first-rotation hoop pine plantation, representing a stable system with sustainable production and high functioning.

Sources (1)

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 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

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

View Source

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

Contextual Support Journal

FOREST CARBON MARKETS - Forestry Australia, accessed July 21, 2025

View Source

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

Contextual Support Journal

Sugarcane cultivation altered soil nitrogen cycling microbial processes and decreased nitrogen bioavailability in tropical Australia - ResearchOnline@JCU, accessed July 29, 2025

View Source

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

Direct Evidence Journal

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

View Source

Context

Region Australia
Biome Tropical & Subtropical Rainforests
Land Use Production Forestry
Assessment Conservation Target
Evidence Type TargetCondition

Lifecycle

Status Active
Version 1
Effective From 20 Mar 2026

Notes

Lower Critical Threshold inferred at ~167 mg/kg indicating significant disturbance and functional impairment. Optimal Range approximately 650–950 mg/kg. No evidence for an upper detrimental threshold; higher levels up to natural saturation point are beneficial.

Related Benchmarks

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