Soil microbial counts in relation to site characteristics at a subantarctic Island

Enumerations of colony-forming units of aerobic bacteria and fungi at Marion Island (46°54'S, 37°45'E) showed that the mire and bog peats investigated possessed greater numbers of microorganisms on a dry soil weight basis than did the slope fernbrake soils but that counts from both sites were similar per unit soil volume. Afjaeldmark soil of an exposed rocky ridge contained very low microbial populations. Manuring by sea-birds and seals caused an increase in levels of soil N and P and in the numbers of bacteria and fungi. Regression analyses indicated that inorganic N and soil pH explained more of the variation in bacterial and fungal counts respectively than all other soil parameters included in the regression. Variation in botanical composition between the sites was examined using multivariate analysis and the resulting pattern compared with the soil microorganism and nutrient levels. This analysis emphasized the importance of manuring influences in elevating NH4-N and bacterial levels in the soil and allowing the occurrence of a vegetation cover dominated by copriphilous species. No correlation occurred between site botanical factors and soil fungi counts.