DEGLACIATION HISTORY INFERRED FROM STABLE ISOTOPE COMPOSITION OF TUNDRA VEGETATION AT NY-ÅLESUND, SVALBARD, NORWAY

Due to global warming, a worldwide phenomenon of glacier retreat has been occurring constantly and rapidly. As a consequence, the exposed land provides a snapshot of temporal change after deglaciation. The compositional variation of vegetation according to glacier retreat was expected to reflect soil development and primary succession. We collected vegetation samples along age gradient of exposure on a glacier foreland at Ny-Alesund, Svalbard, Norway (79°N). We grouped them into three vegetation types, vascular plants, mosses, and lichens, and assessed the carbon and nitrogen variability of the samples. Overall δ¹³C and δ¹⁵N values of collected samples ranged widely from –31.7 to –24.1‰ and from –6.3 to +9.2‰, respectively, and a clear distinction was observed between vascular plants and lichens. They also differed in carbon and nitrogen tissue concentrations, both of which were higher in vascular plants. Mosses generally showed intermediate values. While within-group variation among vascular plants was mostly species-controlled owing to their mycorrhizal status, the composition of mosses differed for each individual. It suggests environmental factors such as soil condition, microclimate, and occasionally, animal excrements, play a greater role in mosses. The analytical data of the collected samples revealed some corresponding patterns to the deglaciation history, which in turn, may affect the ground formation process in the future. Our study site, Ny-Alesund, is a rare settlement in the Northern Hemisphere where human impact is considered minimal. It should be noted that comparison with vegetation samples taken from a pristine area 25 km distant showed that mosses and lichens around the Ny-Alesund scientific research area are significantly more enriched in nitrogen. Given that mosses and lichens are sensitive bioindicators for nitrogen deposition, the high abundance of N may imply that local N pollution by human activities had actually affected vegetation on deglaciated area near the Ny-Alesund village. Further investigation on spatial distribution of tissue N and nitrogen isotope signature is required to verify this hypothesis.