Canopy Vitality Index (CVI)

Definition

The Canopy Vitality Index (CVI) is a dimensionless composite, scaled 0–100, expressing the aggregate physiological health of a defined canopy unit (a bench, a sphere cluster, or a greenhouse cell) at a point in time. It is computed by CHLORA from four independently measured sub-signals — spectral greenness, photosystem-II efficiency, hydraulic turgor, and stomatal gas exchange — each normalized to a per-cultivar reference and combined by a fixed weighting. A CVI of 100 denotes a canopy at its cultivar-specific physiological optimum; 0 denotes total collapse.

Why it matters

CVI is the single number the Directorate reads first. Because it fuses four orthogonal signals, it detects decline earlier and with fewer false alarms than any one sensor: a drop in turgor that has not yet shown in greenness, or a fluorescence dip that precedes visible senescence, both pull the index down before a single-channel alarm would fire. It is the governing input for cultivation cadence, dispatch prioritization, and the facility headline on the Operations Dashboard.

Formula

CVI is a weighted blend of four normalized sub-indices. Each raw signal is first mapped to a 0–1 sub-index against its cultivar reference band, then combined and scaled to 0–100:

CVI = 100 · ( w_n·N + w_f·F + w_t·T + w_g·G )

where, with Σw = 1.00 :
  w_n = 0.35   N = NDVI sub-index            (VC-MET-002)
  w_f = 0.30   F = Fv/Fm sub-index           (VC-MET-003)
  w_t = 0.20   T = stem-turgor sub-index     (VC-MET-006)
  w_g = 0.15   G = stomatal-conductance idx  (VC-MET-004)

Sub-index normalization (clamped to [0,1]):
  N = clamp( (NDVI − 0.45) / (0.85 − 0.45) )
  F = clamp( (FvFm − 0.60) / (0.83 − 0.60) )
  T = clamp( (turgor − 100) / (240 − 100) )
  G = clamp( (g_sw − 0.04) / (0.40 − 0.04) )

  clamp(x) = max(0, min(1, x))

Stress override:  if any sub-index < 0.20 for ≥ 3 consecutive
samples, CVI is capped at 79 (forced into WARN) regardless of the
weighted blend, so a single collapsing channel cannot be masked.

Inputs

Units & Scale

CVI is dimensionless, expressed on a 0–100 scale to one decimal place. It is not additive across canopy units; aggregate (facility) CVI is the biomass-weighted mean of constituent unit indices, never a simple average. Reported alongside a 7-day trend and a confidence flag that degrades if any contributing sensor channel is stale (> 3 missed samples).

Sampling & Source

• Recomputed every 5 minutes by CHLORA from the latest valid sub-signals.
• NDVI sourced from the Spectral Canopy Array (multispectral pass, 15-min cadence, forward-filled between passes).
• Fv/Fm, turgor, and conductance sourced from the PhytoSense Mesh.
• Stale-input handling: any channel older than 15 min is excluded and its weight redistributed proportionally; confidence flag set to DEGRADED.

Thresholds

Recent Trend

Facility-aggregate CVI, biomass-weighted, last 14 sampling roll-ups:

Interpretation Guidance

Related Metrics

Related SOPs

• SOP Library — controlled cultivation & response procedures.
• Canopy decline triage on WARN/CRIT — see Operations SOP set in the SOP Library.
• Monitoring & alarm escalation — Monitoring Systems.