Five differently developed soils aged 6, 35, 80, 150, and >5000 years with the same bedrock and the same (current) climate conditions were chosen to assess abiotic and enzymatic properties as well as methanogenic and methanotrophic activities. Most abiotic properties (dry weight, pH, soil organic matter, and ammonium content), enzyme activities (dehydrogenase [DH] activity, ammonification [AM] rate, dimethylsulfoxide reduction), and potential methane oxidation (PoMO) per gram of dry weight (DW) increased with soil age. In contrast, potential methane production (PoMP) as well as the nitrate content per gram of DW and most enzymatic properties per gram of soil organic matter (SOM) did not increase with soil age but reached its maximum in the middle-aged soils (80–150 years). Our results show that (i) microbial activity does not consequently increase with SOM content/soil age; (ii) methane production can be measured in undeveloped soils, whereas methane oxidation is more restricted to fully developed soils; and (iii) certain soil modifications (change in water content, ammonium addition) could influence potential methane production/oxidation. When considering the concurrent release of raw soil because of the melting of perpetual ice, these data could help to better understand and assess the consequences of global change.