Ammonia oxidizer populations vary with nitrogen cycling across a tropical montane mean annual temperature gradient

Functional gene approaches have been used to better understand the roles of microbes in driving forest soil nitrogen (N) cycling rates and bioavailability. Ammonia oxidation is a rate limiting step in nitrification, and is a key area for understanding environmental constraints on N availability in forests. We studied how increasing temperature affects the role of ammonia oxidizing archaea (AOA) and bacteria (AOB) in soil N cycling and availability by using a highly constrained natural mean annual temperature (MAT) elevation gradient in a tropical montane wet forest. We found that net nitrate (NO3- ) bioavailability is positively related to MAT (r2 = 0.79, P = 0.0033), and AOA DNA abundance is positively related to both NO3- availability (r2 = 0.34, P = 0.0071) and MAT (r2 = 0.34, P