Biotic and abiotic variables influencing plant litter breakdown in streams: a global study

Abstract

Plant litter breakdown is a key ecological process in terrestrial and freshwater ecosystems. Streams and rivers, in particular, contribute substantially to global carbon fluxes. However, there is little information available on the relative roles of different drivers of plant litter breakdown in fresh waters, particularly at large scales. We present a global-scale study of litter breakdown in streams to compare the roles of biotic, climatic and other environmental factors on breakdown rates. We conducted an experiment in 24 streams encompassing latitudes from 47.88 N to 42.88 S, using litter mixtures of local species differing in quality and phylogenetic diversity (PD), and alder (Alnus glutinosa) to control for variation in litter traits. Our models revealed that breakdown of alder was driven by climate, with some influence of pH, whereas variation in breakdown of litter mixtures was explained mainly by litter quality and PD. Effects of litter quality and PD and stream pH were more positive at higher temperatures, indicating that different mechanisms may operate at different latitudes. These results reflect global variability caused by multiple factors, but unexplained variance points to the need for expanded global-scale comparisons.

Warming weakens facilitative interactions between decomposers and detritivores, and modifies freshwater ecosystem functioning

“…Effects of climate changes on organisms indirectly alter ecosystem functioning, such as detritus processing and nutrient cycling (Boyero et al., ; Dossena et al., ; Greig et al., ; Hart & Gotelli, ; Petchey et al., ; Vanni, ). The role of macro‐ and microorganisms in these processes, as well as their interactions, is critical in aquatic ecosystems (Gessner, Chauvet, & Dobson, ).…”

Cellulose Dynamics during Foliar Litter Decomposition in an Alpine Forest Meta-Ecosystem

“…Litter decomposition is a complex biological process that is strongly affected by litter initial quality (i.e., litter chemical traits) [2]. The important role of litter quality for the process of litter decomposition has long been recognized [8], and was recently found to be much more significant than we previously thought both in terrestrial [10,11] and aquatic [34] ecosystems. The degradation of cellulose in decomposing litter is usually thought to be mainly driven by numerous species of microorganisms, including both bacteria and fungi, which rely on extracellular enzymes either secreted into their immediate surroundings or located on the cell surface [2].…”

“…Ecosystem pH typically reflects basic lithology and background biogeochemistry [17], its effect on cellulose degradation in decomposing litter appeared to be consistent in all the investigated individual ecosystems. In addition, nutrient availability in the environment was also an important moderator of cellulose degradation, as it is directly related to the community and activity of microorganisms that degrade cellulose during litter decomposition [34,43]. However, the relative importance for different nutrients varied depending on litter species and ecosystem type.…”

“…Some common drivers, both biotic and abiotic factors, on litter C and N loss [39] have been found across different ecosystem types. Still, to develop common models across aquatic and terrestrial ecosystem or even within one ecosystem type at a broad spatial scale is still challenging, as local-scale environmental factors appear to be much more significant for litter decomposition process than we previously thought [12,34]. For instance, although we found that the concentrations of P and lignin were the dominant litter chemical traits affecting cellulose degradation regardless of ecosystem type, cellulose degradation rate for a specific litter species varied significantly among different ecosystems and decomposition periods, indicating the importance of environmental factors for this process.…”

“…While a large amount of research has investigated the effects of climate and litter quality on litter decomposition in terrestrial ecosystems [2,16] or in aquatic ecosystems [15,34] independently, only few studies [39,40] have investigated this process in a common litter decomposition framework, e.g., in a forest meta-ecosystem. Some common drivers, both biotic and abiotic factors, on litter C and N loss [39] have been found across different ecosystem types.…”