Does Plethodon cinereus Affect Leaf Litter Decomposition and Invertebrate Abundances in Mixed Oak Forest?

Abstract

Although investigators have determined that some anurans can influence nutrient availability in terrestrial systems, ecological interactions among salamanders, invertebrates, and leaf litter decomposition in the detrital ecosystem are poorly understood. We examined the effects of the Eastern Red-Backed Salamander (Plethodon cinereus) on leaf litter decomposition rates and invertebrate populations in the mixed oak forests of southwestern Virginia from May 2006 to June 2008. We constructed 12 in situ mesocosms with 0, 1.0, or 2.0 P. cinereus/m2 (4.0 P. cinereus/m2 in year 2). We quantified decomposition rates of leaf litter and numbers of invertebrates with litter bags that were removed from mesocosms monthly throughout the experiment. Further, we assessed what taxa of invertebrates were preyed upon by salamanders with gastric lavage. Across our 2-year experiment, we were unable to detect an effect of salamander abundance on rates of leaf litter decomposition, numbers of broad invertebrate taxonomic groupings, or functional guilds of invertebrates. Stomach analysis confirmed that salamanders were euryphagic, but they consumed more herbivores than detritivores or predators. Although we are unclear why these results conflict with earlier work indicating that salamanders can influence invertebrates and leaf litter decomposition, variability of canopy trees or microclimate may have contributed to a lack of control of invertebrate populations or litter decomposition by salamanders in the complex mixed-oak forests of the Appalachian Mountains.