Global Patterns of Plant Litter Decomposition in Streams

Understanding ecological patterns and processes at the global scale is becoming increasingly important in view of the rapid pace of environmental change and consequent impacts on ecosystems. This chapter reviews current knowledge about how plant litter decomposition—a key stream ecosystem process—and its major biotic and abiotic drivers vary globally along geographic gradients. The evidence available suggests that thermal regime is the main factor influencing microbial decomposition rate, which tends to increase with temperature. The presence or absence of litter-consuming detritivores is a major determinant of overall decomposition rate, the scarcity of these invertebrates being a common pattern in tropical streams. However, relating detritivore-mediated decomposition rates to environmental factors is complex, because of the interplay between detritivore abundance, body size distribution, diversity and community composition, as well as plant litter traits and diversity, all of which are influenced by climate, geology and biogeography. Meta-analyses and a growing number of coordinated large-scale studies have greatly enhanced our understanding of geographical variation of litter decomposition in streams, and have enabled first projections of how climate warming and a range of other aspects of global environmental change will affect the process.