Effects of elevated nitrogen and fire on the community structure of soil ammonia-oxidizing bacteria in a California grassland

Abstract

Climate change expected to increase rate of soil nitrogen (N) deposition and wildfire frequency in many regions4

Ammonia-oxidizing bacteria (AOB) catalyze the rate-limiting step in nitrification; N2O (nitrous oxide) is a possible side product1, 7

Studies show elevated nitrogen increases AOB abundance, the rate of nitrification, and increases the proportion of the microbial community in 3a cluster of the AOB phylogenetic tree3, 6, 9

Cluster 3a ammonia-oxidizers thrive in high NH4+ (ammonium) soils, and AOB communities with higher proportions of cluster 3a tend to have higher nitrification rates10

Fire also increases soil NH4+ and NO3+ (nitrate), but does not increase relative abundance of cluster 3a AOB nine months after burning3