Senescence Fraction
VC-MET-011 — the percentage of canopy area classified as senescing or chlorotic, the lagging spectral confirmation that physiological decline has progressed to visible tissue loss.
Definition
Senescence Fraction is the percentage of live-canopy area whose spectral signature has shifted into the senescent/chlorotic class — declining chlorophyll, rising carotenoid and brown-pigment reflectance — as classified per-pixel by the Spectral Canopy Array. Unlike the lower-is-worse vitality channels, this is an increasing-is-worse metric: a rising fraction marks the irreversible end stage of decline that earlier sensors only predicted.
Why it matters
Senescence Fraction is the facility's lagging confirmation signal — it is what turns a CVI forecast into observed tissue loss, and it is the trigger for removal, harvest-forward, or isolation decisions. Because it is largely irreversible, a fast-rising fraction is treated as a high-priority event even when other channels read nominal. CHLORA correlates its spatial pattern against pest and toxin-load maps to distinguish natural maturity from pathological decline.
Formula
S = 100 · (N_senescent / N_canopy) (% canopy) per-pixel classification (Spectral Canopy Array): senescent if PRI < −0.05 AND NDVI < 0.55 green otherwise supporting indices: PRI = (ρ531 − ρ570) / (ρ531 + ρ570) photochemical reflectance also weighs red-edge position shift toward shorter λ N_senescent = senescent-class canopy pixels N_canopy = total live-canopy pixels (excludes structure) smoothing: 3-pass (3-h) moving mean to reject classification flicker. Reported to 0.1 %.
Inputs
| Symbol | Quantity | Reference Band | Source |
|---|---|---|---|
| PRI | Photochemical reflectance index | −0.20 → 0.10 | Spectral Canopy Array |
| NDVI | Greenness (class gate) | 0.45 → 0.90 | Spectral Canopy Array |
| Red-edge | Red-edge inflection position | 700 → 730 nm | Spectral Canopy Array |
| N_canopy | Live-canopy pixel count | per cell | Spectral Canopy Array |
Units & Scale
Percent of live canopy, reported to 0.1%. Aggregated per cell as a pixel fraction, then leaf-area-weighted to a facility value (a true area fraction, never a simple cell average). Confidence degrades when the live-canopy pixel count drops below 60% of the cell (mask uncertainty inflates the fraction) or when illumination normalization residual exceeds 8%.
Sampling & Source
- Classified every 1 hour from Spectral Canopy Array hyperspectral passes.
- Smoothed over a 3-h moving mean to reject classification flicker.
- Spatial pattern cross-referenced against pest and toxin-load maps by CHLORA.
- Stale handling: flagged STALE after 2 missed passes; low-mask cells flagged low-confidence.
Thresholds
OK
Background leaf turnover only. No action.
WARN
Elevated senescence; CHLORA advisory, identify cause.
CRIT
Widespread dieback; auto-dispatch, removal/isolation review.
Recent Trend
Facility leaf-area-weighted senescence fraction, last 14 hours:
Interpretation Guidance
| Fraction Band | Reading | Likely Driver | Action |
|---|---|---|---|
| 0–3 | Baseline | Normal old-leaf turnover | None; reference state. |
| 4–6 | Healthy | Normal range, late phenology | None; normal range. |
| 7–12 | Soft rise | Early stress or natural maturity | Check CVI & NDVI; confirm stage. |
| 13–22 | WARN elevated | Sustained stress or pest onset | Identify cause; cultivation review. |
| > 22 | CRIT dieback | Pathology, toxin event, or collapse | Auto-dispatch; removal/isolation review. |
Related Metrics
Canopy Vitality Index
Lagging confirmation of low CVI.
VC-MET-002NDVI
Greenness gate of the classifier.
VC-MET-012Anthocyanin Reflectance
Co-rising stress pigment signal.
VC-MET-010Leaf Area Index
Falls as senescence rises.
VC-MET-401Containment Integrity Index
Escalation path for acute pathology.
VC-MET-210Toxin Yield Rate
Toxin events drive abrupt senescence.
Related SOPs
- SOP Library — senescence classifier validation & removal procedures.
- Acute-senescence escalation & isolation triage — Operations SOP set in the SOP Library.
- Pest/toxin correlation & alarm escalation — Monitoring Systems.