Carbon Isotope Discrimination in Diverging Growth Forms of Saxifraga oppositifolia in Different Successional Stages in a High Arctic Glacier Foreland
Atsushi Kume, Yukiko S. Bekku, Yuko T. Hanba, Hiroshi Kanda
We investigated carbon isotope discrimination of two morphs of Saxifraga oppositifolia and other plant species in a glacier foreland in the High Arctic at Ny-Ålesund, Svalbard, Norway. At this site, soil conditions vary considerably along with the progress of primary succession within a small area. We compared growth forms and δ13C values, which reflect long-term leaf gas exchange characteristics, of plants growing in different successional stages with different soil conditions. Even though the soil mass water content (water mass/dry mass) increased from 10% to 140% with the progress of succession, the water and nitrogen content of the soil had negligible effects on the δ13C values of the observed species. The δ13C values were determined mainly by species and growth forms. We compared two morphs of S. oppositifolia, the prostrate form (P-form) and the cushion form (C-form), on the same riverbank in the glacier foreland. Regardless of the successional stage, the δ13C values of the C-form were about 2‰ more negative than those of the P-form. The ground cover area per plant mass (GA) of the C-form was less than 30% that of the P-form, and the product of GA and stomatal conductance appears to be an important factor in the relationship between transpiration and photosynthesis of a whole plant. We suggest that the relationship between GA and the root mass fraction is a crucial factor affecting the water utilization in high arctic environments. We also examined the relationship between life form and water utilization for other phototrophs, including lichens, mosses, narrow-leaved grasses, perennials, and shrubs.