Leaf Decomposition in an Intermittent Stream: Channel vs. Riparian Area

Abstract

Litter decomposition in intermittent streams is driven by the biotic compartment and uniquely shaped by abiotic conditions such as flow variability. In this study, we compared microbial-mediated decomposition of three temperate native leaf species (alder, chestnut, and oak) in the channel and riparian area of an intermittent stream. The stream channel presented a total of 8, 49, and 35 days of flow, isolated pools, and dry conditions, respectively, while the riparian area remained emersed. Independently of the species, decomposition rates after 3 months incubation were higher in the stream channel than in the riparian area. Alder and chestnut’s different quality was not translated into distinct fungal biomass, which seems to be related with an earlier fungal colonization and faster decomposition of the former. Leaves incubated in-channel presented higher fungal biomass than in the riparian area. During autumn, even in the absence of water flow, a higher moisture in the stream channel and the presence of isolated pools yielded significantly faster decomposition rates and fungal biomass accrual than in the riparian area. We may expect that, along with the resumption of surface flow, the reestablishment of hydrological connectivity will lead to the lateral and longitudinal transport of dissolved nutrients and organic matter of more (channel) or less (riparia) increased quality, fueling local and downstream communities.

Keywords

• flow variability
• streambed
• riparian
• aquatic hyphomycetes
• litter quality