Use this plant measurement when samples, dry- or fresh-mass basis, image threshold, geometry, instrument calibration, and treatment timing follow one consistent protocol.

Gap pixels

An integer count greater than or equal to 0, expressed in pixels.

Total pixels

An integer count greater than or equal to 1, expressed in pixels.

The implementation follows this calculation rule: Compute canopy gap fraction as a percentage of sky-visible pixels over total hemispherical image pixels.^[1]

Gap fraction

The calculated gap fraction in %.

Pigment proxies, canopy metrics, tissue density, and leakage indices are method-dependent. Species, developmental stage, hydration, illumination, extraction efficiency, sensor angle, and environmental conditions can confound comparisons. Ratios and percentages become unstable when their denominator is small, uncertain, or defined differently between samples.

Pair the proxy with calibrated chemical analysis, destructive biomass sampling, or repeated field measurements where practical. Report environmental conditions and whether values use fresh mass, dry mass, area, or volume.

• Canopy Cover %

  Compute canopy cover as canopy area divided by total plot area times 100.

• Canopy Height Difference

  Derive canopy height by subtracting the ground elevation from the maximum surface elevation of a canopy height model.

• Canopy Bulk Density

  Compute canopy bulk density in kilograms per cubic metre as the canopy fuel mass divided by the canopy volume.