Canopy Structure Exhibits Linear and Nonlinear Links to Biome-Level Maximum Light Use Efficiency

Maximum light use efficiency (ε_max) represents a plant's capacity to convert light into carbon during photosynthesis. Although prior studies have explored ε_max variations between sunlit and shaded leaves or its temporal ties to canopy structure, the spatial relationship between biome-level ε_max (ε_biome) and biome structure remains poorly understood. We analysed data from 320 eddy covariance sites (~855 site-years) with satellite-derived near-infrared reflectance of vegetation (NIRv) and leaf area index (LAI). We introduced NIRvN (NIRv/LAI) to isolate architectural effects from leaf quantity. Site-level ε_max was calculated and aggregated by biome to derive ε_biome. Results show ε_biome rises nonlinearly with NIRv and LAI, saturating at high LAI, with crops and tropical evergreen forests deviating from this trend. Conversely, ε_biome decreases linearly with increasing NIRvN, indicating that biomes with greater NIR scattering efficiency exhibit lower ε_biome. These results enhance understanding of structural influences on carbon uptake across global biomes.