9527919 Norton Nitrogen is the element most frequently limiting to plant growth. Yet, excess use of fertilizers can lead to local excesses of nitrogen which have negative environmental impacts. Nitrification is a key process in the nitrogen cycle resulting in N loss from ecosystems, eutrophication of surface and ground water and the production of atmospherically active trace gases. The bacteria responsible for the first step in nitrification are known as ammonia oxidizing bacteria. Basic ecological aspects of soil ammonia oxidizing bacteria remain poorly characterized, at least partially because the existing methods for examination of these bacteria in the environment are difficult to use. This study will develop new methods for the characterization of the quantity and diversity of these important soil bacteria based on the genetic material which encodes a key enzyme of ammonia oxidation. These methods will be applied to examine the soil ammonia oxidizing bacteria in a dryland wheat agricultural system and in a western montane forest site.
