Influence of Terrestrial Molluscs on Litter Decomposition and Nutrient Release in a Hawaiian Rain Forest

Abstract

The roles of terrestrial molluscs in many important ecosystem processes are largely unknown, particularly in tropical forests. It has been suggested from studies in temperate forests that snails/slugs contribute to litter decomposition directly (by their own metabolism) and/or indirectly (by habitat modification enhancing micro‐arthropod or microbial activity). Forty‐two mesocosms were established at seven Hawaiian rain forest sites to examine the role of the five most abundant snail/slug species: the native Succinea cepulla, and the non‐native Arion intermedius, Deroceras laeve, Oxychilus alliarius, and Limax maximus. Controls had no snails/slugs. To assess the contribution of each mollusc species separately, decomposition experiments were conducted in mesocosms containing litter bags and manipulated field densities of the mollusc species. Presence of molluscs increased litter decomposition rates, which were strongly correlated with mollusc biomass. While rates of release of some nutrients (C, K, Mg, and Mn) differed among treatments, multivariate analyses indicated that the different mollusc species influenced nutrient release in a similar way. No increases in smaller invertebrate abundances were observed in treatments containing molluscs, indicating that molluscs do not facilitate smaller invertebrate recruitment and probably influence these ecosystem processes primarily by microbe facilitation. If a major functional role of terrestrial molluscs is to facilitate microbial growth, then maintaining adequate mollusc biomass may be essential for maintaining healthy functioning ecosystems.

Synopsis of Central Andean Orthalicoid land snails (Gastropoda, Stylommatophora), excluding Bulimulidae

“…From the data presented it may be clear that the ecology of nearly all species listed in this paper is still hardly known or very poorly understood. Meyer III et al (2013) have shown that terrestrial gastropods can play a major role in litter decomposition in tropical habitats and the presence of gastropods increased litter decomposition rates; the highest decomposition rates were those with the greatest gastropod biomass. Furthermore, although there were differences in the rates of release of some nutrients among treatments, the different gastropod species appeared to influence nutrient release in a similar way.…”

Linking Biomass Productivity to Genotype-Specific Nutrient Cycling Strategies in Mature Hybrid Poplars Planted Along an Environmental Gradient

“…Litterbags (20 cm × 12.5 cm) were prepared with polyethylene screen of 1 mm mesh size in order to minimise loss of litter fragments [55]. On each litter bag, eight larger round openings (d = 5 mm) were made, with a punch, on both faces of the litterbags to facilitate access of micro-and macro-arthropods, soil molluscs (snails and slugs) and juvenile Lumbricus species [53,56,57]. Litterbags were filled with a precisely weighed quantity of air-dried litter (approximately 3 g, or 8 to 15 leaves, depending on the poplar clone).…”

Habitat augmentation drives secondary invasion: an experimental approach to determine the mechanism of invasion success

“…Leaf litter is a key habitat and food resource for these ground‐dwelling detritivores, which play a key functional role in nutrient cycling through litter consumption and promotion of microbial growth (Meyer et al. ). Bultman and Uetz () demonstrated through leaf litter manipulation experiments that litter depth increased structural complexity that was important for supporting high abundances of litter‐dwelling spiders.…”

“…The finding that snails are promoted by increased leaf litter was not surprising as higher snail abundance is commonly found in higher amounts of litter (Aubry et al 2005, Liew et al 2010, de Chavez and de Lara 2011, including on Christmas Island . Leaf litter is a key habitat and food resource for these ground-dwelling detritivores, which play a key functional role in nutrient cycling through litter consumption and promotion of microbial growth (Meyer et al 2013). Bultman and Uetz (1982) demonstrated through leaf litter manipulation experiments that litter depth increased structural complexity that was important for supporting high abundances of litter-dwelling spiders.…”