Riparian forests shape trophic interactions in detrital stream food webs

Abstract

AbstractFreshwater and terrestrial biodiversity is linked through resource flows. For example, subsidies from the riparian vegetation form the base of food webs in small streams. Despite the key role of detritivores in these food webs, consequences of altered resource availability and riparian vegetation type on their trophic strategies are largely unknown. Therefore, we experimentally tested direct and indirect effects of riparian vegetation type on trophic interactions and dietary imbalances of detritivores. We used stoichiometric and isotopic differences between consumers and resources as functional measures of trophic link strength. Our results show that the lack – compared to the presence – of riparian forests directly affected both stoichiometric and isotopic differences in detrital food webs, yet with diverging patterns between resources and consumers, ultimately leading to aquatic-terrestrial decoupling. Consequently, our findings demonstrate that riparian forests are essential for aquatic food webs by influencing both organisms and interactions networks.