Abstract
We investigated the temperature dependency of photosynthetic rates for five Sphagnum species: Sphagnum palustre, S. fimbriatum in the Tadewara mire (south-western Japan in a warm-temperate zone) and S. papillosum, S. fuscum, S. fallax in the East Ochiishi mire (north-eastern Japan in a cool-temperate zone) measuring photosynthetic light response within a temperature range between 5 and 40。C. The maximum photosynthetic rate was obtained at T = 35。C for S. palustre, S. fuscum and S. papillosum, and at T = 30。C for S. fimbriatum and S. fallax. Photosynthetic rates of all these species showed a maximum at 300 - 500 μmol·m-2·s-1 of PPFD and it decreased at higher PPFD (>500 μmol·m-2·s-1) under low temperature (5。C - 10。C). These results imply that Sphagnum species are not fully physiologically adapted to low temperature environments, although Sphagnum species distribute mostly in the circumpolar region.
Highlights
Carbon accumulation by peat-forming plants is a great concern for the global carbon cycle [1,2]
We investigated the temperature dependency of photosynthetic rates for five Sphagnum species: Sphagnum palustre, S. fimbriatum in the Tadewara mire and S. papillosum, S. fuscum, S. fallax in the East Ochiishi mire measuring photosynthetic light response within a temperature range between 5 and 40 ̊C
Absolute photosynthetic rates of Sphagnum spp. showed high variance between individual plants, and we presented PPFD-photosynthetic rate response curves by the relative rate (%) per maximum rate within the measurements using the same plant samples (Figure 1)
Summary
Carbon accumulation by peat-forming plants is a great concern for the global carbon cycle [1,2]. Sphagnum plants are major components of vegetation in boreal mires and form thick peat layers containing huge amounts of organic carbon. The growth and primary productivity of Sphagnum spp. have been investigated under different conditions of water deficiency, nutrition, acidity, temperature, UV radiation and atmospheric pollution from pollutants such as ozone or bisulphate. Prior eco-physiological studies of Sphagnum plants clarified that most of the Sphagnum spp. grow well under acidic and poor nutritional conditions [3,4]. Some few species such as S. squarrosum and S. fimbriatum can colonize under calcareous conditions [5] Colonization of these pioneer Sphagnum spp. acidifies the habitat and other species are able to colonize the acidic habitat. The growth responses of Sphagnum plants to various environmental parameters have already been investigated, physiological responses of Sphagnum spp
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