Soil carbon mineralisation responses to alterations of microbial diversity and soil structure

Soil organisms are of fundamental importance for many soil functions, such as organic matter decomposition, nutrient cycling and energy flow. Most research suggests that soil microbial communities are functionally redundant, meaning that there is little relationship between microbial diversity and soil functions. However, the activity of biological communities is known to be affected by their physical environment. Here, the effects of changes in microbial diversity and soil structure on organic C (OC) mineralisation were investigated. Sterile soil samples that had been subjected to different physical perturbations were inoculated with microbial communities with different levels of diversity. The samples were incubated for a period of 127 days and the mineralisation of native and added (C-13-labelled substrates, fructose and vanillin) OC was measured. It was hypothesised that the magnitude of the effect of changes in soil structure on OC mineralisation would increase as diversity decreased. The diversity treatment had a small but significant effect on the mineralisation of SOC and of the added substrates. The soil structure treatment had a significant effect only on the mineralisation of the added substrate C. There was no interaction between diversity and soil structure treatments, indicating that the relationship between diversity and OC decomposition was not dependent on the soil physical environment.