Detection of irradiation induced changes on the activity and diversity of soil microbial communities: The effect of soil type

Our aim was to measure the effects of irradiation treatments on soil communities from three different soils. Undisturbed soil cores from three temperate sites (deciduous and coniferous woodland and grassland) were irradiated to give cumulative doses from 0–160 Gy. Cores were incubated at 15C and three cores from each treatment sampled after <1, 3 and 8 d. Soil fungi and heterotrophic bacteria were enumerated and the activity and functional diversity of soil microbial communities assessed in terms of their potential to utilise a range of C-sources. Although no significant treatment effects were observed in the numbers of cultivable fungi or fast growing heterotrophic bacteria, the numbers of cultivable Pseudomonas spp. declined in all three soils after irradiation at 80 and 160 Gy. Microbial communities from the coniferous forest soil also showed a dramatic decrease in the metabolic activity and number of substrates utilised by after irradiation at 160 Gy. Gamma irradiation had a greater affect on microbial communities in the two organic forest soils as compared to the mineral grassland soil, this could be related to variations in the physico-chemical shielding properties and in the indigenous communities in terms of radio-resistant species.