Inside the lysimeters, ash application had a negative effect on soil microbial biomasses as calculated per dry mass of the soil: bacterial biomass in the lysimeters with both 1 mm and 45 μm mesh, and fungal biomass in the lysimeters with 45 μm mesh decreased due to ash-treatment. However, when expressed in relation to the organic matter content of the soil, microbial biomasses were unaffected by the ash-treatment. Ash-treatment had no effect on fungal-to-bacterial ratio inside the lysimeters. Outside the lysimeters, ash changed neither the microbial biomasses nor fungal-to-bacterial ratio compared to the ash-free plots.
Ash-treatment had a clear effect on the structure of the microbial community in the lysimeters. The factor scores of the first PCA-axis of PLFA composition differed clearly between the ash-free and ash-treated lysimeters at each sampling (see above). At the October 1998 sampling also the factor scores of the second PCA-axis were separated with respect to ash-treatment. The substrate utilisation potential of the bacterial community was also affected by the ash-treatment, which was indicated by the difference between the factor scores of the first PCA-axis of the ash-free and ash-treated mesocosms in the October 1998 and June 1999 samplings. In the soils outside the lysimeters, ash-treatment had no influence on the structure of the soil microbial communities.