This study investigates the global distribution and ecological roles of archaea in soil. Using barcoded pyrosequencing, the researchers surveyed archaeal and bacterial communities in 146 soils from various ecosystems worldwide. They found that archaea, primarily Crenarchaeota, were present in nearly all soils, with an average relative abundance of 2%. The two dominant phylotypes within the Crenarchaeota group 1.1b clade accounted for over 70% of all archaeal sequences. Soil C:N ratio was the only consistently correlated factor with archaeal abundance, being higher in soils with lower C:N ratios. The study also examined the response of archaea to nitrogen (N) availability in long-term N addition experiments, finding that the abundance of dominant archaeal phylotypes declined with increasing N levels, suggesting competitive interactions with nitrifying bacteria. These findings highlight the importance of considering a broad range of soils and environmental factors when studying the ecology of archaea in soil.This study investigates the global distribution and ecological roles of archaea in soil. Using barcoded pyrosequencing, the researchers surveyed archaeal and bacterial communities in 146 soils from various ecosystems worldwide. They found that archaea, primarily Crenarchaeota, were present in nearly all soils, with an average relative abundance of 2%. The two dominant phylotypes within the Crenarchaeota group 1.1b clade accounted for over 70% of all archaeal sequences. Soil C:N ratio was the only consistently correlated factor with archaeal abundance, being higher in soils with lower C:N ratios. The study also examined the response of archaea to nitrogen (N) availability in long-term N addition experiments, finding that the abundance of dominant archaeal phylotypes declined with increasing N levels, suggesting competitive interactions with nitrifying bacteria. These findings highlight the importance of considering a broad range of soils and environmental factors when studying the ecology of archaea in soil.