Summary Ammonia oxidation in marine and estuarine sediments plays a pivotal role in the cycling and removal of nitrogen. Recent reports have shown that the newly discovered ammonia‐oxidizing archaea can be both abundant and diverse in aquatic and terrestrial ecosystems. In this study, we examined the abundance and diversity of ammonia‐oxidizing archaea (AOA) and betaproteobacteria (β‐AOB) across physicochemical gradients in Sa...

The dynamics and demography of roots were followed for 5 years that spanned wet and drought periods in native, semiarid shortgrass steppe grassland exposed to ambient and elevated atmospheric CO 2 treatments. Elevated compared with ambient CO 2 concentrations resulted in greater root‐length growth (+52%), root‐length losses (+37%), and total pool sizes (+41%). The greater standing pool of roots under elevated compared with amb...

Summary Six open‐top chambers were installed on the shortgrass steppe in north‐eastern Colorado, USA from late March until mid‐October in 1997 and 1998 to evaluate how this grassland will be affected by rising atmospheric CO 2 . Three chambers were maintained at current CO 2 concentration (ambient treatment), three at twice ambient CO 2 , or approximately 720 μmol mol −1 (elevated treatment), and three nonchambered plots serve...