PNNL

Abstract

Maximum light use efficiency (emax) represents a plant's capacity to convert light into carbon during photosynthesis. Although prior studies have explored emax variations between sunlit and shaded leaves or its temporal ties to canopy structure, the spatial relationship between biome-level emax (ebiome) 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 emax was calculated and aggregated by biome to derive ebiome. Results show ebiome rises nonlinearly with NIRv and LAI, saturating at high LAI, with crops and tropical evergreen forests deviating from this trend. Conversely, ebiome decreases linearly with increasing NIRvN, indicating that biomes with greater NIR scattering efficiency exhibit lower ebiome. These results enhance understanding of structural influences on carbon uptake across global biomes.