Aim: Leaf inputs from riparian vegetation and its decomposition play a key role in energy and nutrients transfer in many stream ecosystems. Instream leaf-litter decomposition is mainly driven by leaf traits. Therefore, understanding and predicting leaf traits variation with current environmental changes and its putative effects on stream food webs is a critical challenge. Most studies have focused on the assumed higher interspecific leaf traits variability, with little research addressing an intraspecific perspective.

Location: Andalusia, Spain

Methods: We assessed the relative effects of climate and soil on the intraspecific variability in leaf traits of four common woody riparian species in permanent low-order Mediterranean streams along a wide aridity gradient. We used a space-for-time substitution approach to predict leaf traits changes and consequences for stream food webs in a future climate change scenario.

Results: We found that climate had a major influence on intraspecific variability of leaf traits, but with opposite patterns depending on plant functional type. Results indicated that leaf quality—linked to palatability and decomposability—of Alnus glutinosa, Salix atrocinerea and Rubus ulmifolius (deciduous/semideciduous) will decrease with the forecasted aridification, whereas that of the evergreen Nerium oleander will increase.

Main conclusions: Our findings suggest a decrease of intraspecific leaf-quality in riparian deciduous species with global warming in a relatively short term, which, in a longer term, may add to the forecasted dieback of deciduous species in riparian corridors of temperate climate zones. These forecasted changes have the potential to significantly impair ecosystem functioning of Mediterranean mountain streams currently under deciduous gallery forests.