T. Pennanen et al., PROLONGED, SIMULATED ACID-RAIN AND HEAVY-METAL DEPOSITION - SEPARATEDAND COMBINED EFFECTS ON FOREST SOIL MICROBIAL COMMUNITY STRUCTURE, FEMS microbiology, ecology, 27(3), 1998, pp. 291-300
The separate and combined effects of moderate levels of acid load and
Cu-Ni deposition on humus (F/H layer) microbial community structure we
re examined six growing seasons after the start of an artificial irrig
ation experiment. A 2(2)-factorial design with acid load (pH 3.1) and
Cu-Ni addition was used. The acid application resulted in acidificatio
n as defined by humus chemistry, including a decrease in the concentra
tion of base cations and an increase in the concentration of H+, Al an
d Fe, leading to a decrease in humus pH from 4.10 to 3.95. The metal a
dditions resulted in a 2-3-fold increase in humus total Cu and Ni conc
entrations. The treatments did not affect the total microbial biomass,
measured by substrate-induced respiration, or the basal respiration r
ate. However, the microbial community structure determined by phosphol
ipid fatty acid (PLFA) analysis showed that the acid load affected the
bacterial part of the community. The relative amount of branched PLFA
s common to Gram-positive bacteria increased with decreasing humus pH,
and the bacterial community was also adapted to more acidic condition
s. The metal addition alone did not cause clear changes in the microbi
al community structure or bacterial tolerance to Cu or Ni. The combine
d acid and metal treatment induced similar changes in the microbial co
mmunity structure as the acid treatment alone. (C) 1998 Federation of
European Microbiological Societies. Published by Elsevier Science B.V.
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