Data from: 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 period of terrestrial was shorter than the period of
aquatic exposure, and when the period of terrestrial was equal to the
period of aquatic exposure the effect of the mixture was additive on mass
loss, decomposers, and detritivores. The species-specific effects also
differed among exposure scenarios. Alder affected poplar only when there
was a period of terrestrial exposure, with increased sporulation rates and
fungal richness in exposure 25:75, and increased mass loss in exposure
50:50. Poplar affected alder only under fully aquatic exposure, with
increased mass loss. In conclusion, the synergistic effects of the mixture
changed with a period of terrestrial exposure prior to immersion. These
results provide a cross-boundary perspective on the effect of mixing
litter, showing a legacy effect of exposure to terrestrial decomposition
on the fate of plant litter in aquatic ecosystems and highlighting the
importance of assessing the effect of mixing litter on the associated
biota and not only on mass loss.