Seasonal and Spatial Variation of Nitrogen Fixation in the Barrow, Alaska, Tundra

A seasonal study of nitrogen fixation was carried out on the arctic tundra in the vicinity of Barrow, Alaska. Nitrogen fixation rates were measured on tundra cores at selected sites at 10-day intervals throughout the summer. The acetylene reduction technique was the principal tool. Significant nitrogen fixation was found throughout the mid-summer months. Indirect evidence suggests that blue green algae of the genus Nostoc were the principal agents along with lichens of the genus Peltigera since isolated specimens of these reduced acetylene with high efficiency. A survey of nitrogen fixation was also carried out on subarctic alpine tundra in the Alaska Range and at Eagle Summit. Here, legumes and other high plants played a relatively more important role, although blue green algae in the moss layer and lichens once again contributed significantly. From the results, we have concluded that nitrogen fixation is a significant source of nitrogen for tundra.