The combined effect of diffuse radiation and leaf wetness on functional traits and transpiration efficiency on a cloud forest species.

This article investigates the combined effects of low radiation and leaf wetness—conditions typical of foggy environments—on the cloud forest species *Myrica faya* Wilbur, native to subtropical laurisilva forests. Through controlled experiments and process-based simulations, the study found that low radiation combined with leaf wetness significantly increases leaf stomatal conductance and specific leaf area (SLA), driven primarily by leaf size changes, while minimum leaf conductance (g_min) showed no clear response. Simulations demonstrated that transpiration efficiency (TE), defined as the ratio of photosynthesis to transpiration, increases exponentially as canopy wetness rises, due to transpiration approaching zero while photosynthesis remains positive. These findings provide integrated insights into how fog influences the physiological functioning of *M. faya* and potentially other cloud forest species under varying radiation and humidity conditions.