Global Spectrum of Vegetation Light-Use Efficiency

Vegetation light-use efficiency (LUE) is a critical parameter of vegetation photosynthesis, but its global variations and the drivers remain poorly understood. Here, we used data from 172 flux tower sites to characterize the global distribution of ecosystem-level LUE spanning various vegetation and climate. The global growing season average LUE was 1.30 +/- 0.55 g C MJ(-1) for 2000-2014. The main factors driving LUE variations included environmental conditions (e.g., temperature), plant traits (e.g., foliar nitrogen concentration and isohydricity) and their interactions, which together accounted for about 76% of the observed global variations in LUE. However, an ensemble of 11 dynamic global vegetation models largely underestimated LUE, and hardly captured the key drivers. Our results highlight that a paradigm shift from vegetation functional type-based scheme to trait-climate spectrum-based scheme is necessary for the next-generation models to accurately simulate the response of vegetation carbon uptake to climate change.