Physiological responses to nitrogen and sulphur addition and raised temperature in <Emphasis Type="Italic">Sphagnum balticum</Emphasis> |
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Authors: | Gustaf Granath Magdalena M Wiedermann Joachim Strengbom |
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Institution: | 1.Department of Plant Ecology, Evolutionary Biology Centre,Uppsala University,Uppsala,Sweden;2.Department of Ecology and Environmental Science,Ume? University,Ume?,Sweden;3.Department of Ecology,Swedish University of Agricultural Sciences,Uppsala,Sweden |
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Abstract: | Sphagnum, the main genus which forms boreal peat, is strongly affected by N and S deposition and raised temperature, but the physiological
mechanisms behind the responses are largely unknown. We measured maximum photosynthetic rate (NPmax), maximum efficiency of photosystem II variable fluorescence (F
v)/maximum fluorescence yield (F
m)] and concentrations of N, C, chlorophyll and carotenoids as responses to N and S addition and increased temperature in Sphagnum balticum (a widespread species in the northern peatlands) in a 12-year factorial experiment. NPmax did not differ between control (0.2 g N m−2 year−1) and high N (3.0 g N m−2 year−1), but was higher in the mid N treatment (1.5 g N m−2 year−1). N, C, carotenoids and chlorophyll concentration increased in shoot apices after N addition. F
v/F
m did not differ between N treatments. Increased temperature (+3.6°C) had a small negative effect on N concentration, but had
no significant effect on NPmax or F
v/F
m. Addition of 2 g S m−2 year−1 showed a weak negative effect on NPmax and F
v/F
m. Our results suggest a unimodal response of NPmax to N addition and tissue N concentration in S. balticum, with an optimum N concentration for photosynthetic rate of ~13 mg N g−1. In conclusion, high S deposition may reduce photosynthetic capacity in Sphagnum, but the negative effects may be relaxed under high N availability. We suggest that previously reported negative effects
on Sphagnum productivity under high N deposition are not related to negative effects on the photosynthetic apparatus, but differences
in optimum N concentration among Sphagnum species may affect their competitive ability under different N deposition regimes. |
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Keywords: | Chlorophyll fluorescence Nutrient deposition Peatlands Photosynthesis Photosynthetic nitrogen-use efficiency |
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