Characterization of the forest humus microbial community in a heavy metal polluted area

Various parameters of the soil microbial community may be used in soil quality evaluation and environmental risk assessment. The objectives of this study were to assess the effects of different environmental factors on the characteristics of forest humus microbial communities, and to test which environmental factors most affect the gross microbial indices and physiological profiles of these communities. Samples were taken at 71 plots located in a heavily polluted area of the Krakowsko-Czgstochowska upland in southern Poland. The samples were analyzed for pH in KCl (pH(KCl)), organic C (Cordi total N (N-t) and S (S-t), and for total and soluble Zn, Pb and Cd concentrations. The considered microbial parameters included basal respiration (BAS), microbial biomass (C-mic), C-mic-to-C-org ratio, and community-level physiological profiles (CLPPs) studied using BIOLOG (R) Ecoplates. Multiple regression analysis was used to estimate the effects of humus properties on the microbial parameters. It indicated that St and C-org-to-Nt ratio were the most important factors positively affecting C-mic (beta = 0.15 and 0.11, respectively) and BAS (beta = 0.13 and 0.08, respectively). The c(mic)-to-c(org) ratio was related positively to St (beta = 0.12) but negatively to N-t (beta = -0.08). The effects of pH(KCl), and heavy metals on the gross microbial indices were significant but less important. The most important effect on microbial activity on BIOLOG (R) plates and CLPPs was from pH(KCl). The other significant variables included S-t, C-org-to-N-t and interactions of heavy metals with pH(KCl), It was concluded that C-mic, C-mic-to-C-org and BAS might be good indicators of the general status of soil microbial communities, but their use in studying heavy metal effects may entail difficulties in separating the effects of other factors. The sensitivity of the BIOLOG (R) test to pHKCl suggests that it may be useful for studying the effects of acidification or liming on soil microbial communities. The significant effect of the interactions between heavy metals and other variables on physiological profiles indicated that high heavy metal content affects the metabolic functions of soil microbial populations. (c) 2005 Elsevier Ltd. All rights reserved.