Ecosystem consequences of mass mortality events

Death is a natural phenomenon that plays an important role in nutrient cycling. However, mass mortality events (MMEs), which involve the sudden death of many individuals, may differ for several reasons. First, MMEs produce larger amounts of carrion and therefore the large amounts of nutrients may have stronger bottom-up effects. Second, an MME may generate strong top-down effects because the functional role associated with the dead organisms becomes less common in the ecosystem. While MMEs are increasing in frequency, it is unknown how these combined effects alter the ecosystem. Therefore, we are studying MMEs in a 2 by 3 factorial design crossing two biomasses (~ 30 kg single carcass or ~ 360 kg MME per 10 m² plot) and three functional group manipulations (open control plots or fencing that excluded either herbivores or scavengers). Our experiment is evaluating the community- and ecosystem-level effects of these treatment combinations. Initial results have demonstrated a strong effect of carcass biomass (MME) on soil properties, including elevated nitrogen concentration for over one year. Compared to single carcass treatments, MMEs attracted a similar composition of necrophagous insects, but at higher abundances and for a longer period of time. Ongoing analyses are evaluating other community effects including both above and belowground arthropod communities to provide new insights on the effects of MMEs.