Manipulation of Leaf Litter Stoichiometry

A common approach in trophic ecology is to manipulate the elemental composition of food resources to examine imbalances between the elemental requirements and resource composition of consumers. Primarily applied for three decades to plant-herbivore interactions, the approach has recently been extended to leaf litter and shredders in both laboratory and field experiments. The method presented in this chapter details the steps to produce food resources for shredders that differ in their elemental stoichiometry and thus in their nutritional quality. The approach takes advantage of the capacity of fungi and bacteria associated with decomposing litter to immobilise dissolved nutrients, due to the not strictly homeostatic elemental composition of these microbes. Variation in elemental stoichiometry is achieved by exposing leaf litter colonised by microbes to controlled short pulses of dissolved nutrients at elevated concentrations. Within 3 days, this results in up to fourfold differences in C:P ratios of otherwise similar leaf litter. Application of the method has shown that high nutrient concentrations of leaf litter consumed by shredders can have counterintuitive effects, such as increased vulnerability to parasite infection or metal pollution.