Lasting Effects of Different Scaled Mass Mortality Events on Soil Microbial Communities

Death is a natural process present in all ecosystems; however, mass mortality events are instances of larger than average numbers of animals dying in a relatively short period of time. These events are increasing in frequency and magnitude, and the effects of mass mortalities - especially their long-term effects - are understudied. To better understand the long-term effects of mass mortalities in terrestrial ecosystems, we conducted experimental mass mortality events to determine if key ecosystem properties remained affected after 4 years. The experiment crossed three types of input treatments (control, carrion, and nutrient additive) with scavenger access (open plots versus fenced plots). To evaluate how increasing carrion biomass affected the ecosystem, sites were randomly assigned biomass (25, 59, 182, 363, 726 kg total (20m² plots)). Biomasses consisted of feral swine carcasses or the equivalent amount of N, phosphorus, and K nutrients. After 4 years, we found that while soil N did not differ among treatments, soil K and Ca significantly increased with biomass. Microbial communities significantly differed at the 182 kg biomass treatments compared to others and indicated significant effects between carrion and nutrient additive treatments. These results demonstrate that large die-offs, such as mass mortality events, can have long-lasting effects on soil composition through increased soil nutrients and alter soil microbial community (i.e., reduced Bacilliaceae, etc.). These long-lasting impacts can permanently alter the soil community, which can lead to cascading bottom-up effects that can alter the entire ecosystem structure.