Fungal species diversity affects leaf decomposition after drought

The number of studies on the importance of biodiversity in stream ecosystem processes increased in the last years; however, little is still known on its role in scenarios of flow intermittency. In this study, we conducted a microcosm experiment to test the diversity‐insurance hypothesis on microbial decomposing oak leaves exposed to a drought event. Three microbial diversity levels were tested, single species and mixture assemblages of three or eight species of aquatic hyphomycetes. We also evaluated changes in leaf litter quality promoted by leaves desiccation to the shredder Schizopelex festiva . Fungal mixed assemblages resulted in higher decomposition and fungal sporulation rates than single species. This pattern was maintained after drought and decomposition was rapidly reassumed with rehydration. Fungal‐mediated decomposition seems to be more stimulated in the presence of rich (vs. single) fungal assemblages even after desiccation, particularly when species addition occurs at lower levels of richness. Shredder consumption was not affected by leaf desiccation, although feeding rates were consistently higher on leaves conditioned with eight fungal species and likely affected by the identity of the dominant taxa. Bottom‐up effects are expected on the food webs of detritus‐based streams affected by droughts; the intensity of these effects seems to be dependent on the level of decline promoted on decomposers richness by the environmental perturbation.