Background/Question/Methods Global warming and atmospheric nitrogen deposition are expected to influence ecosystem net primary production substantially over the next century.  Numerous studies have characterized plant responses to these global change factors at the level of experimental plots in the field. In these experiments, however, it can be difficult to distinguish between direct effects of the treatments on plant productivity and species composition and indirect effects mediated through changes in herbivory or detritivory.  We examined the extent to which litter consumption by a detritivorous land snail, Cepaea nemoralis, is altered by warming and nitrogen addition, either directly through changes in local microclimate, or indirectly through changes in litter tissue quality, in the context of a climate change experiment conducted in a temperate old field.  We addressed the former using mollusc exclosures located within the experimental plots, and the latter using cafeteria-style feeding experiments on plant litter collected from the plots monthly.
Results/Conclusions

In all plots, litter mass outside of snail exclosures was significantly lower than litter mass inside the exclosures.  No significant differences were observed when rates of litter removal were compared among treatments.  There were no significant effects of litter quality on snail feeding preferences early in the summer, although litter from warmed plots was preferred over litter from ambient temperature plots in August   In addition consumption of litter from ambient plots was significantly higher than consumption of litter from nitrogen addition plots.  Overall, our results reveal that the snail detritivory varies in response to the experimental treatments.  The resulting variation in litter layer thickness may influence plant productivity and species composition through changes in ground level shading, microclimate, and the physical obstruction of new shoots.