Predicted climate change alters the indirect effect of predators on an ecosystem process

Abstract

Changes in rainfall predicted to occur with global climate change will likely alter rates of leaf-litter decomposition through direct effects on primary decomposers. In a field experiment replicated at two sites, we show that altered rainfall may also change how cascading trophic interactions initiated by arthropod predators in the leaf litter indirectly influence litter decomposition. On the drier site there was no interaction between rainfall and the indirect effect of predators on decomposition. In contrast, on the moister site spiders accelerated the disappearance rate of deciduous leaf litter under low rainfall, but had no, or possibly a negative, indirect effect under high rainfall. Thus, changes resulting from the more intense hydrological cycle expected to occur with climate change will likely influence how predators indirectly affect an essential ecosystem process.detrital food web ͉ litter decomposition ͉ rainfall ͉ spiders ͉ trophic cascade C limate-change models predict a more intense hydrological cycle with both increases in rainfall and increased length and severity of droughts (1, 2). Changes in rainfall will likely affect ecosystem processes such as primary production and nutrient release from decomposing litter caused by direct effects of altered rainfall on plants and primary decomposers, respectively. For example, low moisture can inhibit fungal growth and͞or activity (3, 4). Changes in rainfall may also alter how trophic interactions indirectly influence rates of ecosystem processes. Recent research has shown that climatic changes may have large impacts on how predators indirectly alter net primary production through trophic cascades (reviewed in refs. 5-8). In detritusbased food webs predators have the potential to influence indirectly the amount of leaf litter through trophic interactions that affect rates of decomposition. This chain of interactions is a trophic cascade (9-12) analogous to the classic cascade affecting living plants. In grassland systems litter in cages accessible to large arthropod predators exhibited lower rates of litter disappearance compared with predator-exclusion cages (13,14), although other similar experiments in grasslands revealed a negligible impact of these predators on decomposition rate (15). In a forest-floor system, experimentally reducing spider numbers also accelerated the rate of disappearance of a straw test litter (16). However, a longer-term experiment using natural canopy litter produced an opposite effect, with litter decomposing more rapidly at higher spider densities (12). This extreme variation in the sign of the indirect effect of spiders and other predators on decomposition, from negative through zero to positive, may at least partly reflect differences in abiotic factors between sites and years. The unexpected enhancement of decomposition by spiders in the forest-floor experiment occurred during a period of unusually low rainfall (12), which suggests that large changes in moisture, such as those predicted by climate-change models, may affect ...

Effects of short-term warming on low and high latitude forest ant communities

“…(Folgarait 1998, Petchey et al 1999, Lensing and Wise 2006, Suttle et al 2007, Barton et al 2009, Harmon et al 2009, O'Connor et al 2009, Gilman et al 2010, Traill et al 2010. We found this to be the case at our southern site, where we observed decreases in rates of granivory, seed dispersal, and nectivory.…”

Ecotoxicity of cadmium in a soil collembolan-predatory mite food chain: Can we use the 15N labeled litter addition method to assess soil functional change?

“…Relatively stable F. candida reproduction was observed from 0 to 50 mg Cd kg À1 in our study and the fact that the atom% 15 N of H. aculeifer decreased significantly at a Cd concentration range of 12.5e50 mg Cd kg À1 compared to the control, which reflects the decline of predation on collembolans by the mites at the range, supports our hypothesis. Many data in ecological studies have demonstrated that predators can mediate prey population numbers by changing feeding intensity (Yoshida et al, 2003;Lensing and Wise, 2006). The present study indicates that, compared to the single species test, H. aculeifer showed a higher sensitivity to Cd and the sensitivity of F. candida would decrease in our model food chain test system and this agrees well with our assumption that the predatorprey relationship would influence species sensitivities to soil Cd pollution (Fig.…”

Water availability directly determines per capita consumption at two trophic levels

“…In a community context, Noy-Meir (1973, 1974 postulated that arid regions are limited more by water than energy, such that arid ecosystems may best be represented by conceptual models using water as a currency instead of energy (i.e., a water web; Sabo et al 2008). However, since then, animal community ecologists have done little to investigate water's influence on interactions (but see Preisser and Strong 2004, Lensing and Wise 2006, Spiller and Schoener 2008. Greater interest in the effects of water limitation on animal communities is warranted considering recent work that suggests, at broad geographic scales, both plant and animal species richness patterns are correlated with water variables more than energy, at all but the most northern latitudes globally (Hawkins et al 2003).…”