Title: Microbial assemblages of Icelandic soils under different revegetation methods

In this study of microbial assemblages of Icelandic soils under different revegetation methods, the objectives were to: (1) identify groups of microorganisms in soils under different revegetation methods, (2) assess the relative abundance of microbial groups in soils under different revegetation methods, and (3) assess the effect of time of revegetation on microbial assemblages. Soil samples were collected at a depth of 0-8 cm systematically along a transect at Geitasandur, Hafnarmelar, Mogilsa and Keldnaholt where different revegetation methods existed. Samples were analysed for microbial groups and relative abundance using the plate count method. Differences in abundance were tested using one-way analysis of variance, the independent samples t-test, Kruskal-Wallis and Mann-Whitney tests. The results showed that Icelandic soils under revegetation contain bacteria, fungi and actinomycetes, with different growth rates and colours. The white and yellow bacteria, and white fungi were widespread, while actinomycetes were only detected in Geitasandur. Slow growing groups were more abundant than fast growing groups. At Geitasandur, bacteria were more abundant in grass, fertilizer, birch and willows, while fungi and actinomycetes were more abundant in grass and fertilizer. At Hafnarmelar, bacteria and fungi were significantly more abundant in alder only than at the untreated site. At Mogilsa, the abundance of bacteria and fungi in birch only was not significantly greater than at the untreated site. At Keldnaholt, there was no significant difference in abundance of fungi and bacteria between grass and fertilizer and lupine only. Unlike bacteria, young revegetation methods had more groups and a higher relative abundance of fungi than old methods.