Soil-foraging animals alter the composition and co-occurrence of microbial communities in a desert shrubland

Abstract

Animals that modify their physical environment by foraging in the soil can have dramatic effects on ecosystem functions and processes. We compared bacterial and fungal communities in the foraging pits created by bilbies and burrowing bettongs with undisturbed surface soils dominated by biocrusts. Bacterial communities were characterized by Actinobacteria and Alphaproteobacteria, and fungal communities by Lecanoromycetes and Archaeosporomycetes. The composition of bacterial or fungal communities was not observed to vary between loamy or sandy soils. There were no differences in richness of either bacterial or fungal operational taxonomic units (OTUs) in the soil of young or old foraging pits, or undisturbed soils. Although the bacterial assemblage did not vary among the three microsites, the composition of fungi in undisturbed soils was significantly different from that in old or young foraging pits. Network analysis indicated that a greater number of correlations between bacterial OTUs occurred in undisturbed soils and old pits, whereas a greater number of correlations between fungal OTUs occurred in undisturbed soils. Our study suggests that digging by soil-disturbing animals is likely to create successional shifts in soil microbial and fungal communities, leading to functional shifts associated with the decomposition of organic matter and the fixation of nitrogen. Given the primacy of organic matter decomposition in arid and semi-arid environments, the loss of native soil-foraging animals is likely to impair the ability of these systems to maintain key ecosystem processes such as the mineralization of nitrogen and the breakdown of organic matter, and to recover from disturbance.

Mammalian engineers drive soil microbial communities and ecosystem functions across a disturbance gradient

“…This reduced modularity was associated with decreases in the clustering coefficient, density and centralization of the resulting network (Eldridge et al . ). Modularity in network structures reflects both the capacity of the community to respond to short‐term (reactive) and long‐term (resilience) perturbations.…”

“…This depth is to the average depth of rabbit or echidna foraging pits (Eldridge et al . ) and represents a procedural control. Approximately 5 g of soil was collected from all microsites using a sterilized spatula.…”

“…In order to reduce any confounding effect that different pit age (Eldridge et al . , ) or pit size might have on microbial community composition or soil enzyme concentrations, we collected all soil samples from pits of a similar age, about six months old. We have been monitoring foraging pits at the Scotia Sanctuary quarterly for more than three years and can estimate pit age roughly by measuring attributes such as the mass of litter trapped organic matter, pit shape and the presence of loose surface material around the pit margins (Eldridge et al .…”

“…), its effects on soil microbial communities and therefore function are poorly known (though see Eldridge et al . ). Differences in effects between echidnas and rabbits could be due to the structural differences between their foraging pits.…”

“…; Eldridge et al . ) and microbial community structure (e.g. Bardgett & van der Putten ; Maestre et al .…”