Changes in microbial community structure due to chronic trace element concentrations in different sizes of soil aggregates

Studies on the effects of trace elements (TEs) (e.g. Cu, Cd, Zn) on soil microbial communities have provided useful information on the toxicity of TEs to microbes. However, previous studies mainly focused on the effects of TEs on microbial community structure in intact soil, while there are few studies on the impact of TEs on microbial community structure in soil aggregates. In this study, soils previously polluted for 20 years, and now containing low and high TE concentrations derived from, now abandoned, metal smelters were sampled from the surface layer (0–15 cm) of two adjacent Chinese paddy fields. The aim was to determine the effects of TEs on the soil microbial biomass and community structure in different sized soil aggregates. Long-term high TE pollution decreased microbial biomass concentration and species, changed the proportion of bacteria and fungi and decreased the diversity of bacteria in the different sized aggregates. The microbial communities in soil aggregates became clustered with increasing TE concentrations.