Photosynthetic characteristics and biomass distribution of the dominant vascular plant species in a high Arctic tundra ecosystem, Ny-Alesund, Svalbard: implications for their role in ecosystem carbon gain.

Studies on terrestrial ecosystems in the high Arctic region have focused on the response of these ecosystems to global environmental change and their carbon sequestration capacity in relation to ecosystem function. We report here our study of the photosynthetic characteristics and biomass distribution of the dominant vascular plant species, Salix polaris, Dryas octopetala and Saxifraga oppositifolia, in the high Arctic tundra ecosystem at Ny-Alesund, Svalbard (78.5 degrees N, 11.5 degrees E). We also estimated net primary production (NPP) along both the successional gradient created by the proglacial chronosequence and the topographical gradient. The light-saturated photosynthesis rate (A (max)) differed among the species, with approximately 124.1 nmol CO(2) g(-1)leaf s(-1) for Sal. polaris, 57.8 for D. octopetala and 24.4 for Sax. oppositifolia, and was highly correlated with the leaf nitrogen (N) content for all three species. The photosynthetic N use efficiency was the highest in Sal. polaris and lowest in Sax. oppositifolia. Distributions of Sal. polaris and D. octopetala were restricted to the area where soil nutrient availability was high, while Sax. oppositifolia was able to establish at the front of a glacier, where nutrient availability is low, but tended to be dominated by other vascular plants in high nutrient areas. The NPP reflected the photosynthetic capacity and biomass distribution in that it increased with the successional status; the contribution of Sal. polaris reached as high as 12-fold that of Sax. oppositifolia.