Effect of CH4-starvation on atmospheric CH4 oxidizers in taiga and temperate forest soils

The soil organisms that consume atmospheric CH4 in upland ecosystems have not been identified. Whether these organisms benefit from oxidizing atmospheric CH4 or whether CH4 is cooxidized fortuitously is uncertain. We investigated the general nutritional physiology of atmospheric CH4 oxidizers occurring in three forest soils by starving them of CH4 for 1-2 months and monitoring their abilities to consume atmospheric CH4 over time. In two Alaskan taiga forest soils, CH4 starvation caused the atmospheric CH4 oxidizers to lose their ability to consume CH4, indicating that they benefitted from oxidizing atmospheric CH4, possibly requiring it for maintenance and growth. In contrast, the organisms in a temperate hardwood forest soil from Massachusetts maintained their ability to consume atmospheric CH4 despite prolonged CH4 deprivation, suggesting that they either cooxidized CH4 fortuitously, or that they used alternative substrates for maintenance and growth. These results may point to diverse nutritional physiologies among atmospheric CH4 oxidizers. (C) 1998 Elsevier Science Ltd. All rights reserved.