Effects of mixing litter on decomposition under three exposure scenarios

The effect of mixing litter on decomposition has received considerable attention in terrestrial and aquatic (but rarely in both) ecosystems, with a striking lack of consensus in the obtained results. We studied the decomposition of a mixture of poplar and alder in three terrestrial:aquatic exposures to determine (1) if the effect of mixing litter on mass loss, associated decomposers (fungal biomass, sporulation rates, and richness) and detritivores (abundance, biomass, and richness of invertebrate shredders) differs between the stream (fully aquatic exposure) and when litter is exposed to a period of terrestrial exposure prior to immersion and (2) the effect of the mixture across exposure scenarios. The effect of the mixture was additive on mass loss and synergistic on decomposers and detritivores across exposure scenarios. Within scenarios, mass loss and decomposers showed synergistic effects only in the fully aquatic exposure, detritivores showed synergistic effects only when the peri..., The study site and the litter decomposition study are described in detail in Abelho, M. & Descals, E. (2019). Litter movement pathways across terrestrial–aquatic ecosystem boundaries affect litter colonization and decomposition in streams. Functional Ecology, 33, 1785–1797. https://doi.org/10.1111/1365-2435.13356.
Mean deviation between observed values in the mixture and the average of the single species was assessed with the relative mixture effect (RME). Mean deviation between the values of a species in the mixture and that single species was assessed with the relative individual performance (RIP)., Data are provided in an open access spreadsheet (ods)., # **Effects of mixing litter on decomposition under three exposure scenarios**

Data are values of mass loss, ergosterol content, sporulation rates, fungal richness, shredder biomass, abundance, and richness, associated with leaves decomposing in three exposure scenarios to determine the effect of mixing litter (1:1 mixture of *Alnus glutinosa* (L.) Gaertn. and *Populus × canadensis* Moench) on decomposition

**Exposure scenario**. The litterbags were incubated in three terrestrial-aquatic exposure scenarios.

* **0:100** – 0 days terrestrial; 56 days aquatic (stream)
* **25:75** – 14 days terrestrial; followed by 42 days in the stream.
* **50:50** – 28 days terrestrial followed by 28 days in the stream.

**RME.** Relative Mixture Effect: comparison of the values in the mixture with the average of the two single species.

**RIP.** Relative Individual Performance: comparison of a species in the mixture with that species alone.

**n/a.** There are no values because there was not eno...