Soil microbial activity, mycelial lengths and physiological groups of bacteria in a heavy metal polluted area

The biological effects of heavy metal contamination of coniferous forest soils were studied in the A₀₁/A₀₂ layer around a primary smelter in Northern Sweden. Soil concentrations of 17 elements were determined. Smelter-emitted heavy metals were 5 to 75 times higher in the plot closest to the smelter compared with background levels. Despite emission of sulphur no decrease in pH was found.

Bacteria producing acid from maltose, cellobiose, arabinose or xylose and bacteria hydrolysing starch, pectin, xylan or cellulose decreased 8- to 11-fold due to the soil contamination. Chitin hydrolysers were 5 times less abundant at the most polluted site compared with background levels. Soil respiration rate and urease activity decreased by about a factor of 4, but phosphatase activity and mycelial lengths were unaffected by the soil contamination. Soil bacteria showed a sigmoidal response to the log of metal concentration in the soil and were affected at a lower pollution level than the other biological variables in the study.

A multivariate analysis (partial least squares) showed that soil metal contamination and soil pH were the two environmental factors influencing the soil microorganisms.