ARCUS | Arctic Research Consortium of the United States

7th Annual ARCUS Award for Arctic Research Excellence


Submitted by   Sandra Rolph
Authors   Sandra G. Rolph, G. H. R. Henry, and C. E. Prescott
Category   Life Science
Title   The Effects of a Nine-Year Climate Warming Experiment on the Nitrogen Economy in High Arctic Tundra
Affiliation   Geography, University of British Columbia, Vancouver, BC, Canada

Abstract

The effects of a ten-year climate warming experiment on the nitrogen (N) economy was studied at five sites along a soil moisture gradient at Alexandra Fiord, Ellesmere Island, Canada (78°53’N, 75°55’W). Open top chambers increased the air and soil temperatures by 2.0 and 1.3°C, respectively, each year. Inrganic N availability, measured using ion exchange membranes (IEMs), was higher in the warmed plots throughout the growing season. Soluble organic N fluxes to the IEMs also increased significantly in the warmed plots at the wet sedge meadow site during peak plant growth. At the same site, microbial inorganic N immobilization was four-times higher in the warmed plots compared to the ambient treatments during the growing season. A reciprocal transplant experiment was conducted to determine if the increase in microbial immobilization was due to warming either directly, by affecting soil N transformations, and/or indirectly, with changes in litter chemistry and soil organic matter quality. A long-term feedback effect on N availability was observed, with significant increases in the litter C:N ratios and changes in species composition at some experimental sites.