Perera-Castro Alicia V, Nadal Miquel
Department of Botany, Ecology and Plant Physiology, Universidad de La Laguna, La Laguna, Canary Islands, Spain.
Institute of Biology, University of Hohenheim, Stuttgart, Germany.
Physiol Plant. 2025 May-Jun;177(3):e70325. doi: 10.1111/ppl.70325.
Photosynthesis and respiration respond differently to the combined effects of temperature and water status. Quantifying their responses is crucial to predict the carbon balance of Sphagnum peatlands in different scenarios of climate change. A first approach was done for two Sphagnum species inhabiting a boreal peatland in Finland. Gas exchange at different temperatures and moss hydration were measured to model net assimilation using simultaneous measurements of photosynthesis and dark respiration. In addition, measurements of moss surface temperature at different water content were performed in the field, covering natural conditions of sun exposure and air temperature. We also accounted for the interaction effect between moss canopy temperature and air temperature, radiation, and water content. Our model accurately predicted net assimilation and was used to estimate net primary productivity based on meteorological inputs and moss water content. The two Sphagnum species presented optimum temperatures for net CO assimilation around 25°C, with minimum changes at other temperatures. In contrast, dark respiration increased exponentially with temperature, which makes losses of carbon during the night and the duration of dark conditions key determinants in the carbon balance of Sphagnum. The modeled net primary productivity revealed an enhancement of CO fixation under warming conditions (averaged +10°C), concomitant to the expected transformation of peatlands from sink to source of CO. Our model highlighted the importance of respiration restriction in ensuring positive assimilation in Sphagnum. Therefore, day and night temperature oscillation and short night photoperiods are more important than the optimum temperature of photosynthesis for carbon balance.
光合作用和呼吸作用对温度和水分状况的综合影响反应不同。量化它们的反应对于预测不同气候变化情景下泥炭藓泥炭地的碳平衡至关重要。针对芬兰北方泥炭地的两种泥炭藓物种进行了初步研究。测量了不同温度和苔藓水合作用下的气体交换，以通过同时测量光合作用和暗呼吸来模拟净同化作用。此外，在野外测量了不同含水量下苔藓表面温度，涵盖了阳光照射和气温的自然条件。我们还考虑了苔藓冠层温度与气温、辐射和含水量之间的相互作用效应。我们的模型准确地预测了净同化作用，并用于根据气象输入和苔藓含水量估算净初级生产力。这两种泥炭藓物种在约25°C时呈现出净CO同化的最佳温度，在其他温度下变化最小。相比之下，暗呼吸随温度呈指数增加，这使得夜间碳损失和黑暗条件持续时间成为泥炭藓碳平衡的关键决定因素。模拟的净初级生产力显示，在变暖条件下（平均升高10°C）CO固定增强，这与泥炭地从CO汇向源的预期转变相伴。我们的模型强调了呼吸限制在确保泥炭藓中积极同化作用方面的重要性。因此，昼夜温度振荡和短夜光周期对碳平衡而言比光合作用的最佳温度更为重要。
