An assessment of soil enrichment by actinorhizal N^2 fixation (delta)15N values in a chronosequence of deglaciation at Glacier Bay, Alaska

The extent of transfer of fixed N between N2-fixing and non-N2-fixing plant species is largely unknown in successional studies. In order to redress this deficiency at a locale intensively studied ecologically, leaf tissue samples were collected from actinorhizal N2-fixing (Alnus, Shepherdia, and Dryas) and two non-N2-fixing (Salix) woody species within research plots located along a chronosequence of deglaciated fjord in Glacier Bay National Park, Alaska. The tissue samples were analyzed for (delta)15N values increased from the most recently deglaciated sites to converge with the temporally more-stable values for the symbiotic N2-fixing species on sites at about 40 years after deglaciation. The lower (delta)15N values for the N2-fixing and non-N2-fixing species indicated that this species is most responsible for accumulation of fixed N in soil at Glacier Bay. This paper is dedicated to the memory of Steven J. Kohls who died prior to publication of this research.