LAI
Leaf Area Index. A dimensionless measure of the total one-sided area of leaf tissue per unit ground surface area. It characterizes plant canopy structure and is used for predicting photosynthesis, evapotranspiration, and crop yield.
Overview
Leaf Area Index (LAI) is a dimensionless biophysical parameter defined as total one-sided leaf area per unit ground area (m²/m²). Unlike spectral indices computed from band ratios, LAI is a physical property measured in the field or estimated from remote sensing. It is a critical input for carbon assimilation, evapotranspiration, and crop yield models.
How It Works
LAI can be measured directly (destructive leaf harvesting) or indirectly using optical instruments like the LI-COR LAI-2200 that estimate LAI from light transmission through the canopy. For satellite estimation, LAI is derived from vegetation indices (NDVI, EVI) or through radiative transfer model inversion (e.g., PROSAIL). Global products include MODIS MOD15A2H and Copernicus Global Land Service.
Key Facts
- Typical values: grasslands 1–3, crops 2–6, deciduous forests 4–8, tropical forests 6–9+.
- One of 50 Essential Climate Variables (ECVs) defined by WMO/GCOS.
- MODIS MOD15A2H provides 8-day, 500 m global LAI product since 2000.
- Can be estimated from NDVI, EVI, or radiative transfer model inversion.
Applications
Carbon Cycle Modeling
LAI controls canopy photosynthesis rates — required for GPP and net ecosystem exchange estimates.
Crop Yield Estimation
Tracking LAI through growing season helps predict yield and optimize management timing.
Evapotranspiration Estimation
Key parameter in energy balance models such as SEBAL and METRIC.
Limitations & Considerations
Satellite-derived LAI saturates above approximately 4–5 when based on NDVI. Different products can disagree significantly. Ground validation is sparse in remote regions. Does not capture leaf orientation or vertical foliage distribution.
History & Background
Introduced by plant ecologist Joji Watson in 1947. Operational satellite products began with MODIS in 1999 (MOD15). Recognized as an Essential Climate Variable by GCOS.
Analyze LAI data with LYRASENSE
Use our agentic notebook environment to work with satellite data and compute indices like LAI — no setup required.