# Generated by scripts/sync_indices.py from Awesome Spectral Indices (MIT).
# DO NOT EDIT BY HAND. Edit overlays (_asi_*.yaml, _folia_*.yaml) and re-run.
# Spec: docs/spec/SPECTRAL_INDICES.md
slug: psri
name: Plant Senescing Reflectance Index
short_name: PSRI
formula: (R - B)/RE2
bands:
- R
- B
- RE2
domain: vegetation
theme: vegetation
concepts: []
rank: 18
display:
  colormap: rdylgn
  range:
  - -0.2
  - 0.5
  reverse: true
pedagogy:
  description: 'Plant Senescing Reflectance Index (Merzlyak 1999). Tracks the

    ratio of carotenoid to chlorophyll content via red, blue, and

    red-edge bands. Rises sharply during leaf senescence as

    chlorophyll degrades faster than carotenoids.

    '
  use_cases:
  - Crop maturity and harvest-readiness monitoring late in the season
  - Deciduous-forest autumn phenology tracking
  - Stress and disease detection that precedes visible leaf yellowing
  limitations:
  - Requires Sentinel-2 / MERIS red-edge band 2 — not computable on Landsat or MODIS
  - Inverted scale from most vegetation indices (high values indicate senescence) — annotate the colormap accordingly
  - Confounded by background soil signal in sparse canopies
  interpretation:
    high: Senescing or yellowing canopy
    mid: Mid-season transition
    low: Healthy green canopy
  authoritative_sources:
  - label: Merzlyak 1999
    url: https://doi.org/10.1034/j.1399-3054.1999.106119.x
  - label: NV5 ENVI — Leaf Pigments
    url: https://www.nv5geospatialsoftware.com/docs/LeafPigments.html
  - label: Index Database · PSRI
    url: https://www.indexdatabase.de/db/i-single.php?id=69
references:
- url: https://doi.org/10.1034/j.1399-3054.1999.106119.x
date_of_addition: '2022-04-08'
contributor: https://github.com/davemlz
platforms:
- Sentinel-2
source:
  authority: awesome-spectral-indices
  commit_sha: 7f28d3fe68af1287f7449faf0685659e73197212
  upstream_id: PSRI
match_tags:
- b
- index
- plant
- r
- re2
- reflectance
- senescing
- vegetation
status: stable