Leaf litter decomposition in intermittent streams: An Overview

Abstract

Litter decomposition is a key ecosystem process that has been relatively little studied in intermittent rivers. During the dry phase, leaf litter undergoes various modes of processing, whether aquatic, terrestrial, or a combination, resulting in a heterogeneous decomposition process. In isolated pools, adverse conditions and lack of flow limit the activity of aquatic fungi and shredders, reducing decomposition. In exposed sediments, prolonged drought reduces the activity of decomposers, also impacting their community composition. Aquatic shredders decline with water disappearance, while terrestrial invertebrates contribute limitedly to the decomposition process. Microbial decomposition is also reduced, albeit to a lesser extent, emphasizing the prevalence of drought-resistant aquatic fungi. During drought, abiotic processes such as air temperature, solar radiation, and precipitation increase their contribution to decomposition. Overall, the duration of drought and local conditions modulate the reduction in decomposition during the dry phase. Upon the return of flow, decomposition is slower than in permanent rivers, attributed to changes in leaf litter quality and decomposer communities during the dry phase. Understanding the dynamics of organic matter in intermittent rivers, especially during the dry phase and considering all its complexity, is essential to understand the fate of terrestrial organic matter in river networks.