Tallinn University, School of Natural Sciences and Health, Institute of Ecology, Uus-Sadama 5, 10120 Tallinn, Estonia.
University of Oulu, Department of Ecology and Genetics, P.O.Box 8000, FI-90014 Oulu, Finland; University of Eastern Finland, School of Forest Sciences, P.O. Box 111, FI-80101 Joensuu, Finland.
Sci Total Environ. 2019 Dec 10;695:133867. doi: 10.1016/j.scitotenv.2019.133867. Epub 2019 Aug 10.
Calcareous spring fens are among the rarest and most endangered wetland types worldwide. The majority of these ecosystems can be found at high latitudes, where they are affected by above average rates of climate change. Particularly winter temperatures are increasing, which results in decreased snow cover. As snow provides an insulating layer that protects ecosystems from subzero temperatures, its decrease is likely to induce stress to plants. To investigate the sensitivity of the bryophyte community - key to the functioning of calcareous spring fens - to changing climatic conditions, we studied the annual variation in ecophysiology of two dominant bryophytes: Campylium stellatum and Scorpidium scorpioides. Further, a snow removal experiment was used to simulate the effect of changing winter conditions. In both species, we observed lowest efficiency of photosystem II (Fv/Fm) in spring, indicating physiological stress, and highest chlorophyll-a, -b and carotenoid concentrations in autumn. Snow removal exacerbated physiological stress in bryophytes. Consequently Fv/Fm, pigment concentrations and chlorophyll to carotenoids ratios declined, while chlorophyll-a to -b ratios increased. Moreover, these effects of winter climate change cascaded to the growing season. C. stellatum, a low hummock inhabitor, suffered more from snow removal (annual mean decline in Fv/Fm 7.7% and 30.0% in chlorophyll-a) than S. scorpioides, a hollow species (declines 5.4% and 14.5%, respectively). Taken together, our results indicate that spring fen bryophytes are negatively impacted by winter climate change, as a result of longer frost periods and increased numbers of freeze-thaw cycles in combination with higher light intensity and dehydration.
钙质泉湿地是世界上最稀有和最濒危的湿地类型之一。这些生态系统大多数位于高纬度地区，那里受到气候变化速度高于平均水平的影响。特别是冬季温度在升高，这导致积雪覆盖减少。由于雪提供了一层隔热层，可以保护生态系统免受零下温度的影响，因此其减少可能会给植物带来压力。为了研究对气候变化敏感的苔藓植物群落（钙质泉湿地的关键组成部分），我们研究了两种占优势地位的苔藓植物：星状毛蕊苔和蝎尾蕉的生理生态年度变化。此外，还进行了除雪实验，以模拟冬季条件变化的影响。在这两个物种中，我们观察到春季的光合作用系统 II 效率（Fv/Fm）最低，表明存在生理压力，而秋季的叶绿素-a、-b 和类胡萝卜素浓度最高。除雪加剧了苔藓植物的生理压力。结果，Fv/Fm、色素浓度和叶绿素与类胡萝卜素的比值下降，而叶绿素-a 与 -b 的比值增加。此外，冬季气候变化的这些影响还会延续到生长季节。低丘生种星状毛蕊苔（C. stellatum）比凹叶苔（S. scorpioides）遭受的影响更大，后者是一种凹形物种（Fv/Fm 分别下降 7.7%和 30.0%，叶绿素-a 分别下降 5.4%和 14.5%）。总的来说，我们的结果表明，由于更长的冻结期和更多的冻融循环次数，加上更高的光强度和脱水，冬季气候变化对春季泉湿地苔藓植物产生负面影响。
