Diversity of arbuscular mycorrhizal fungus populations in heavy-metal-contaminated soils

High concentrations of heavy metals have been shown to adversely affect the size, diversity, and activity of microbial populations in soil, The aim of this work was to determine how the diversity of arbuscular mycorrhizal (AM ) fungi is affected by the addition of sewage-amended sludge containing hea vy metals in a long-term experiment. Due to the reduced number of indigenou s AM fungal (AMF) propagules in the experimental soils, several host plants with different life cycles were used to multiply indigenous fungi. Six AMF ecotypes were found in the experimental soils, showing consistent differen ces with regard to their tolerance to the presence of heavy metals. AMF eco types ranged from very sensitive to the presence of metals to relatively to lerant to high rates of heavy metals in soil, Total AMF spore numbers decre ased with increasing amounts of heavy metals in the soil, However, species richness and diversity as measured by the Shannon-Wiener index increased in soils receiving intermediate rates of sludge contamination but decreased i n soils receiving the highest rate of heavy-metal-contaminated sludge, Rela tive densities of most AMF species were also significantly influenced by so il treatments, Host plant species exerted a selective influence on AMF popu lation size and diversity, We conclude based on the results of this study t hat size and diversity of AMF populations were modified in metal-polluted s oils, even in those with metal concentrations that were below the upper lim its accepted by the European Union for agricultural soils.