Litter quality and stream physicochemical properties drive global invertebrate effects on instream litter decomposition

Abstract

Plant litter is the major source of energy and nutrients in stream ecosystems and its decomposition is vital for ecosystemnutrient cycling and functioning. Invertebrates are key contributors to instream litter decomposition, yet quantification oftheir effects and drivers at the global scale remains lacking. Here, we systematically synthesized data comprising 2707observations from 141 studies of stream litter decomposition to assess the contribution and drivers of invertebrates tothe decomposition process across the globe. We found that (1) the presence of invertebrates enhanced instream litterdecomposition globally by an average of 74%; (2) initial litter quality and stream water physicochemical properties wereequal drivers of invertebrate effects on litter decomposition, while invertebrate effects on litter decomposition were notaffected by climatic region, mesh size of coarse-mesh bags or mycorrhizal association of plants providing leaf litter;and (3) the contribution of invertebrates to litter decomposition was greatest during the early stages of litter mass loss(0–20%). Our results, besides quantitatively synthesizing the global pattern of invertebrate contribution to instream litterdecomposition, highlight the most significant effects of invertebrates on litter decomposition at early rather than middleor late decomposition stages, providing support for the inclusion of invertebrates in global dynamic models of litterdecomposition in streams to explore mechanisms and impacts of terrestrial, aquatic, and atmospheric carbonfluxes.