The functional and structural succession of mesic-grassland soil microbiomes beneath decomposing large herbivore carcasses

Abstract

Plant detritus is abundant in grasslands but decomposes slowly and is relatively nutrient-poor, whereas animal carcasses are labile and nutrient-rich. Recent studies have demonstrated that labile nutrients from carcasses can significantly alter the long-term soil microbial function at an ecosystem scale. However, there is a paucity of knowledge on the functional and structural response and temporal scale of soil microbiomes beneath large herbivore carcasses. This study compared microbiome functions and structures of soil beneath Connochaetes taurinus (hereafter ‘wildebeest’) carcasses at various postmortem intervals of decomposition to matched control samples over 18 months. Microbial functions were compared by their community-level physiological profiles determined by sole-carbon substrate utilisation and structures by metagenomic sequences using 16S rRNA gene markers. Overall metabolism and metabolic diversity remained increased and functionally dissimilar to control soils throughout the experimental period, with successive sole-carbon substrate utilisation observed. Conversely, diversity was initially reduced and structurally dissimilar from the control soil but recovered within the experimental period. The study contributes to the knowledge of carcass decomposition by investigating the long-term soil microbiome dynamics resulting from large herbivore carcasses decomposing in a mesic grassland. Microbial functional succession and ecologically relevant bacterial biomarkers of soil beneath the decomposing carcasses were identified for various postmortem intervals.