A causal trait model for explaining foliar water uptake capacity

Questions

Plants largely vary in their capacity for foliar water uptake (FWU), that is, the capacity to increase leaf water content by directly absorbing water from leaf-wetting events. Climate change will reduce leaf wetting and increase drought events. Therefore, we need a better understanding of the underlying traits and mechanisms that facilitate FWU.

Location

Seasonally dry tropical montane grasslands in Brazil (Campos de Altitude).

Methods

We measured FWU and leaf traits related to wettability, surface conductance, water potential and water storage on up to 55 plant species. By using Direct Acyclic Graph theory and Bayesian modelling, we tested how those leaf traits affect FWU.

Results

We found that stomatal conductance largely explained interspecific variation in FWU, which was also favoured in species with hydrophilic leaves, high cuticular conductance, more negative leaf water potentials, low dry-matter content, isohydric behaviour, and more elastic cell walls.

Conclusions

Due to the existence of trade-offs, not all species exhibit an optimal combination of traits that favours FWU. Instead, co-occurring species have achieved a similar capacity for FWU through distinct trait combinations. Consequently, species engaged in FWU may exhibit differential vulnerabilities to climate change as they can cope with drought using other strategies beside FWU.