Nitrosomonas europaea-like bacteria detected as the dominant β-subclass Proteobacteria ammonia oxidisers in reference and limed acid forest soils

Net nitrification in intact soil cores and the community of ammonia-oxidising bacteria were studied in acid Norway spruce (Picea abies (L.) Karst) and sessile oak (Quercus petraea (Matt. Lieb.)) soils (Haute Ardenne, east Belgium) 18 months after treatment with 5 t ha−1 dolomite lime. Liming caused a significant increase in nitrification in the upper soil layers (0.15 m) of both stands. DGGE (denaturing gradient gel electrophoresis) profiling after β-subclass ammonia oxidiser-specific polymerase chain reaction (PCR), combined with hybridisation and sequencing of excised DGGE bands revealed a dominance of Nitrosomonas europaea-like sequences, independent of soil horizon, tree species and lime treatment. A minority Nitrosospira-like population was detected, which showed affinity to nitrosospiras previously detected in acid soil. These results contrast with several reports suggesting a dominance of Nitrosospira-like organisms among ammonia oxidiser communities in acid soils.