Net photosynthesis, respiration, and production of the moss Sanionia uncinata on a glacier foreland in the High Arctic, Ny-Ålesund, Svalbard

As part of the study on carbon cycling in a deglaciated area in the High Arctic, Ny-Ålesund, Svalbard (79°N), we examined the effects of abiotic factors on the net photosynthesis and dark respiration rates of the dominant moss Sanionia uncinata (Hedw.) Loeske. The rates of net photosynthesis (Pn) and dark respiration (R) were measured using an open-flow gas exchange system with an infrared gas analyzer in the snow-free season of 2000. High photosynthetic activities were observed only in rainy days or soon after rainfall, when moss water content was high. Under a sufficiently humid condition, Pn determined at near light saturation was almost constant over a wide temperature range from 7 to 23°C, while R increased with temperature with a Q₁₀ value of 3.0. Based on the relationships between abiotic factors and the CO₂ exchange rate, we estimated the net primary production (NPP) of the moss in the snow-free season using the meteorological data obtained over 6 yr (1995-2000). The mean, minimum, and maximum values of NPP for the 6-yr period were 17, 1, and 30 g dry wt. m^-2 snow-free season^-1, respectively. It was suggested that NPP of the moss in this area varied widely between years depending primarily on water availability.