Photosynthetic Responses of Three Dominant Plants in a High Arctic Tundra Ecosystem: A Measurement Test Using a Portable Photosynthesis System and an Improved Chamber
関川, 清広村岡, 裕由
20 , 2017-03-01
The atmospheric concentration of CO2 is exceeding 400 ppm (V/V) in recent years. The global warming by increasing CO2 concentration affects on ecosystems negatively. Our objective in this study is to clarify characteristics of leaves and their photosynthetic responses to increasing CO2 concentration of vascular plant species in a high Arctic tundra ecosystem. In summer of 2014, we measured the photosynthetic responses to ambient CO2 of three dominant species, Saxifraga oppositifolia, Salix polaris, and Dryas octopetala in the high Arctic tundra, near Ny-?lesund, in the northwestern area of Spitsbergen, Svalbard, Norway. We obtained similar results to Muraoka et al. (2008) for photosynthetic light response curves and leaf nitrogen contents (leaf N, %), based on leaf dry mass. The maximum photosynthetic rate of S. polaris was the highest and one of S. oppositifolia was the lowest. The photosynthetic CO2 response curve for S. polaris was the highest and they for S. oppositifolia and D. octopetala were similar. The leaf N for S. polaris was the highest and for S. oppositifolia was the lowest. As results, photosynthetic nitrogen use efficiency (PNUE) for D. octopetala was the highest and for S. oppositifolia was the lowest. The ratio of photosynthetic rates at 800 ppm of ambient CO2 concentration (Ca800) to those at Ca400 was the highest for S. oppositifolia, and the lowest for S. polaris. It is suggested that herbaceous plant species more respond to increasing ambient CO2 concentration than woody species.