Limnetica 39

Ecological stoichiometry has been defined as the study of the balance of chemical elements in ecological interactions. This approach was initially aimed at understanding the causes and consequences of elemental imbalances in nature, from molecular to ecosystem levels. Despite the theoretically wide applicability of this conceptual framework, most ecological stoichiometry studies have been restricted to the plant – herbivore interface and these studies have only rarely explored consequences of elemental imbalances at the community and ecosystem scales.

Detritus-based ecosystems can be defined as ecosystems receiving most of their energy inputs under the form of detritus, i.e. dead organic matter. This detritus are generally dominated by dead plant material, which most often correspond to strongly nutrient-depleted organic matter. Stoichiometric imbalances are thus expected to be particularly exacerbated in this kind of ecosystems. Mainly fueled by allochthonous detritus (e.g. dead wood, leaf litter), forested headwater streams represent typical detritus-based ecosystems, but also well-suited ecosystem models for understanding the consequences of elemental imbalances in nature.

In this paper, after summarizing the main concepts of ecological stoichiometry and the stoichiometric peculiarities of detritus-based ecosystems, I will present, based on a selection of literature examples, a list of stoichiometric questions that have been investigated in forested headwater stream ecosystems in the past few years. I will finally present a non-exhaustive list of research perspectives that should deserve, in my opinion, particular attention for improving our understanding of the consequences of elemental imbalances in detritus-based ecosystems.