Nature – Zhan et al. (2025): Reduced water loss rather than increased photosynthesis controls CO₂-enhanced water-use efficiency
Weiwei Zhan, Xu Lian, Jiangong Liu, Jisu Han, Yu Huang, Hao Yang, Chunhui Zhan, Alexander J. Winkler and Pierre Gentine, IN: Nature Ecology & Evolution, https://doi.org/10.1038/s41559-025-02761-0
Numerous leaf-level experiments suggest that plant intrinsic water-use efficiency (iWUE) increases under elevated CO₂ because of reduced stomatal conductance and enhanced photosynthesis. However, it remains elusive whether this response can be extrapolated to the ecosystem scale, because confounding factors and compensating feedbacks are often involved in ecosystem iWUE variations. Here the authors develop a machine learning-based framework to disentangle the ecosystem-scale CO₂ effects on iWUE and its two components, canopy conductance (Gc) and gross primary productivity (GPP), based on global networks of long-term eddy covariance observations.