The trophic role of a forest salamander: impacts on invertebrates, leaf litter retention, and the humification process

Abstract

Abstract. Woodland (Plethodontid) salamanders are the most abundant vertebrates in North American forests, functioning as predators on invertebrates and prey for higher trophic levels. We investigated the role of Ensatina (Ensatina eschscholtzii ) in regulating invertebrate numbers and leaf litter retention in a northern California forest. Our objective was to examine how salamander predation on invertebrates affects leaf litter retention and the amount available for soil-building and carbon capture at the litter-soil interface. We used field enclosures to quantify the effects of Ensatina on invertebrates and litter retention over two wet seasons, using moisture as a covariate. In the first year Ensatina reduced Coleoptera (beetles) and Diptera (flies) larvae .2 mm, adult Coleoptera, Collembola (springtails), and Formicidae (ants), and increased Oribatid mites, larvae ,2 mm (Diptera and Coleoptera), Diplopoda (millipedes), and Aranaea (spiders) ,2 mm by reducing their competitors and predators. A single Ensatina in a 1.5m 2 enclosure increased litter retention by 13.3% 6 3.6% (mean 6 SE) compared to controls, facilitating the capture of 200 kg/ha of carbon. At a similar density range-wide this would equate to 72.3 metric tons/yr of carbon in one season potentially sequestered in forest soil rather than entering the atmosphere. In the second year invertebrate densities doubled in response to early rains such that while salamanders reduced the numbers of the same taxa, effect sizes were lower compared to year one, producing biological effects that failed to achieve statistical significance. However, three taxa did significantly increase in year two (Annelida [worms], Psocoptera [barklice], and Chelonethida [pseudoscorpions]). Litter retention in year two was greater on treatment plots by 5.6% 6 4.6%; however, high variability across plots precluded statistical significance. Ensatina suppressed some invertebrate taxa, released others, increased leaf litter retention, and facilitated greater carbon capture in both years; however, the strength of the effects were modulated by the bottom-up effects of the timing and amount of precipitation in year two.

Too wet for frogs: changes in a tropical leaf litter community coincide with La Niña

“…Terrestrial leaf litter amphibians are important predators in the leaf litter environment and play a crucial role in nutrient cycling, energy flow, and carbon storage of forest ecosystems (Davic andWelsh 2004, Best andWelsh 2014). Their importance stems from high population densities and efficiency at converting invertebrate biomass to vertebrate biomass (Best and Welsh 2014).…”

“…Their importance stems from high population densities and efficiency at converting invertebrate biomass to vertebrate biomass (Best and Welsh 2014). Moisture is a key factor regulating leaf litter predator-prey dynamics (Walton 2013), and variable rainfall has been shown to alter the invertebrate prey base of leaf litter amphibians (Levings and Windsor 1984).…”

“…Moisture is a key factor regulating leaf litter predator-prey dynamics (Walton 2013), and variable rainfall has been shown to alter the invertebrate prey base of leaf litter amphibians (Levings and Windsor 1984). Most of the work on leaf litter amphibian ecology comes from temperate forests (Davic and Welsh 2004), but tropical species also are expected to be ecologically important and sensitive to rainfall variability (Best andWelsh 2014, Ryan et al 2014).…”

Predicted Changes in Climatic Niche and Climate Refugia of Conservation Priority Salamander Species in the Northeastern United States

“…Because of their exceptionally abundant biomass, amphibians are known to greatly influence nutrient cycling [3][4][5] and leaf-litter food webs [2]. Furthermore, salamanders are important for structuring invertebrate communities in primary stream [5,6] and forested [7,8] environments, sequestering forest carbon stocks [8], and providing a significant and nutritious prey source for other predators [3].…”

Potential change in the distribution of an abundant and wide-ranging forest salamander in a context of climate change

“…Many studies have revealed the importance of salamanders in food webs and their contribution to nutrient cycling (Walton et al 2006, Best andWelsh 2014) and carbon sequestration (Best and Welsh 2014). Given their physiological requirements, they are generally very sensitive to habitat disturbance (deMaynadier and Hunter 1995).…”