Salamander loss alters litter decomposition dynamics.

Biodiversity loss affects ecosystem functioning. Top down effects of amphibian declines on the trophic food web of the forest floor are poorly understood. Here we quantify and explain the effects of disease-driven loss of salamanders on the dynamics of forest leaf litter. Using paired mesocosms, within a Belgian forest, we tested the effect of fire salamander (Salamandra salamandra) presence on the trophic cascade that results in the decomposition rate of good quality (maple - Acer pseudoplatanus) and poorer quality (oak - Quercus robur) leaf litter, over an 18 month period. The presence of salamanders reduced decomposition rate of Quercus litter up to 20%. This was associated with a significantly higher predation rate on detritivores, which altered the functional composition of the invertebrate community. Functional composition analysis of the litter microbiome showed less bacteria associated with leaf litter degradation on the Quercus litter in the presence of salamanders. Salamanders thus influence ecosystem functions through trophic cascades and promote the retention of the leaf litter fraction in poorer quality litter.