Metals affect soil bacterial and fungal functional diversity differently

Heavy metals can cause a decrease in the taxonomic diversity of soil communities. Because of functional redundancy, it remains unclear to what extent different functions performed by the soil microbial communities may be affected by pollution. We studied the impact of metal contamination on soil bacterial and fungal functional diversity, active microbial biomass, and soil respiration rate. Soil samples were collected from 39 sites along three forest and five meadow pollution transects near an abandoned Pb/Zn smelter in Avonmouth (UK) and Ni smelter in Clydach (UK), in a Cu mining and smelting region near Glogów (Poland), and in a Zn/Pb mining and smelting region near Olkusz (Poland). Biolog GN2 and SFN2 plates were used to study the bacterial and fungal functional diversity, which subsequently was expressed as Shannon's diversity index (H'). The active microbial biomass was measured as substrate-induced respiration. We found that the bacterial functional diversity significantly decreased, whereas the fungal functional diversity slightly increased, with increasing metal concentration. We also observed a slight negative effect of metal pollution on the active microbial biomass. No relationship was found between metal contamination and total soil respiration rate. This suggests a higher sensitivity of bacterial functional diversity as an indicator for the effects of metal pollution compared with overall soil respiration. All microbial parameters were affected by nutrient concentrations and/or soil pH.