Antibiotics and temperature interact to disrupt soil communities and nutrient cycling

Soils contain immense diversity and support terrestrial ecosystem functions, but they face both anthropogenic and environmental stressors. While many studies have examined the influence of individual stressors on soils, how these perturbations will interact to shape soil communities and their ability to cycle nutrients is far less resolved. Here, we hypothesized that when soils experience multiple stressors their ability to maintain connected and stable communities is disrupted, leading to shifts in C and N pools. To test this, we maintained soils across three temperatures representative of seasonal variability (15, 20 and 30 °C) and introduced high or low doses of the common livestock antibiotic Monensin. We monitored respiration and examined changes to microbial communities through amplicon sequencing and network analyses. We also examined soil C and N pools to understand how temperature and antibiotics shape ecosystem function. We found that antibiotics and rising soil temperatures interacted to disrupt bacterial assemblages and network structure, allowing for a rise in fungal dominance and change in soil nutrient stoichiometry. Antibiotics alone decreased bacterial diversity, abundance, total extractable N, and microbial carbon use efficiency, while increasing bioavailable C. Higher temperatures independently homogenized fungal community composition, decreased dissolved organic C and increased soil respiration rates. These results emphasize that as soils encounter multiple stressors, ecosystem efficiency, stability and resilience may be diminished.