Predator/Prey-Interactions Promote Decomposition of Low-Quality Detritus
Predation on detritivores is expected to decelerate detritivore-mediated decomposition processes. In field mesocosms, we studied whether the decomposition of leaf and needle litter of live oak (Quercus virginiana) and loblolly pine (Pinus taeda), respectively, was affected by saltmarsh detritivores (Gastropoda: Littoraria irrorata and Melampus bidentatus) and predacious omnivores (Decapoda: Armases cinereum) and their interactions. Both crabs and snails alone increased decomposition (mass loss) rates of oak litter, while a combination of both resulted in the same mass loss as in animal-free controls, probably due to crabs feeding on snails rather than litter. Neither crabs nor snails alone affected mass loss of pine litter, but a combination of both significantly increased decomposition rates. Irrespective of the litter type, crabs significantly increased mortality of the snails but gained biomass only on pine litter and only when detritivorous snails were present. Our findings suggest that unidirectional facilitation of omnivorous semi-terrestrial crabs by their detritivorous prey (saltmarsh snails) promotes the decomposition of low-quality (pine) litter. On high-quality (oak) litter, by contrast, negative effects of the predator prevail, resulting in a drop of decomposition rates when crabs were present, probably owing to predation on detritivorous snails. Thus, the effects of predator/prey-interactions on decomposition processes are context-dependent and are controlled by resource quality.
KeywordsDecomposition processes Predator/prey-interaction Omnivory Saltmarsh Spatial subsidy
Experiments described herein comply with the current laws of the U.S.A. and were conducted in conformity with the “Guiding principles in the care and use of animals” approved by the Council of the American Physiological Society. AB and CE were financially supported through grants from the Christian-Albrechts-Universität zu Kiel. Franziska Seer, Gregor Putze and Yury Zablotski provided invaluable assistance at all stages of the field work. We thank the U.S. National Science Foundation (OCE06-20959) for financial support. This is contribution number 1017 of the University of Georgia Marine Institute. This work is a contribution of the Georgia Coastal Ecosystems LTER program.
- Abele LG (1992) A review of the grapsid crab genus Sesarma (Crustacea: Decapoda: Grapsidae) in America, with the description of a new genus. Smithsonian Contributions to Zoology, Number 527, Washington, DCGoogle Scholar
- Bless R (1977) Beitrag zur Ernährungsweise ausgewählter Nacktschneckenarten des Naturparks Kottenforst-Ville. Journal of Pest Science 50:1612–4758Google Scholar
- Bradford MA, Jones TH, Bardgett RD, Black HIJ, Boag B, Bonkowski M, Cook R, Eggers T, Gange AC, Grayston SJ, Kandeler E, McCaig AE, Newington JE, Prosser JI, Setälä H, Staddon PL, Tordoff GM, Tscherko D, Lawton JH (2002) Impacts of soil faunal community composition on model grassland ecosystems. Science 298:615–618PubMedCrossRefGoogle Scholar
- Daiber FC (1977) Salt-marsh animals: Distributions related to tidal flooding, salinity and vegetation. In: Chapman VJ (ed) Wet coastal ecosystems. Elsevier, Amsterdam, pp 79–108Google Scholar
- Gonzalez G, Seastedt TR (2001) Soil fauna and plant litter decomposition in tropical and subalpine forests. Ecology 82:955–964Google Scholar
- Schmitz OJ (2004) From mesocosms to the field: the role and value of cage experiments in understanding top-down effects in ecosystems. In: Weisser WW, Siemann E (eds) Insects and Ecosystem Function, Springer Series in Ecological Studies. Springer-Verlag, Berlin, pp 277–302Google Scholar
- Silliman BR, Zieman JC (2001) Top-down control of Spartina alterniflora production by periwinkle grazing in a Virginia salt marsh. Ecology 82:2830–2845Google Scholar
- Thompson LS (1984) Comparison of the diets of the tidal marsh snail, Melampus bidentatus and the amphipod, Orchestia grillus. Nautilus 98:44–53Google Scholar
- Valiela I, Wilson J, Buchsbaum R, Rietsma C, Bryant D, Foreman K, Teal J (1984) Importance of chemical composition of salt marsh litter on decay rates and feeding by detritivores. Bulletin of Marine Science 35:261–269Google Scholar
- Wu X, Duffy EJ, Reich PB, Sun S (2011) A brown-world cascade in the dung decomposer food web of an alpine meadow: effects of predator interactions and warming. Ecological Monographs 81: 313–328Google Scholar
- Zimmer M, Topp W (1997) Does leaf litter quality influence population parameters of the common woodlouse, Porcellio scaber Latr., 1804 (Crustacea: Isopoda)? Biology and Fertility of Soils 24: 435–441Google Scholar