Flower and seed biomass, and germination rate of arctic tundra plants in response to long term experimental warming

We provide new information on changes in tundra plant sexual reproduction in response to long-term (12 years) experimental warming in the High Arctic. Open-top chambers (OTCs) were used to increase growing season temperatures by 1-2 °C across a range of vascular plant communities. The warming enhanced reproductive effort and success in most species; shrubs and graminoids appeared to be more responsive than forbs. We found that the measured effects of warming on sexual reproduction were more consistently positive and to a greater degree in polar oasis compared with polar semidesert vascular plant communities. Our findings support predictions that long-term warming in the High Arctic will likely enhance sexual reproduction in tundra plants, which could lead to an increase in plant cover. Greater abundance of vegetation has implications for primary consumers - via increased forage availability, and the global carbon budget - as a function of changes in permafrost and vegetation acting as a carbon sink. Enhanced sexual reproduction in Arctic vascular plants may lead to increased genetic variability of offspring, and consequently improved chances of survival in a changing environment. Our findings also indicate that with future warming, polar oases may play an important role as a seed source to the surrounding polar desert landscape.本研究提供了高北极地区长期（12年）模拟增温下，苔原植物有性生殖变化的全新数据。研究采用开顶式增温箱（Open-top Chambers, OTCs），在多种维管植物群落中将生长季温度提升1-2℃。增温处理提升了多数物种的生殖投入与生殖成功率；灌木与禾草类植物的响应显著强于非禾本草本植物。研究发现，相较于极地半荒漠维管植物群落，极地绿洲群落中增温对有性生殖的促进效应更为持续且强度更高。本研究结果验证了相关预测：高北极地区长期增温或可增强苔原植物的有性生殖能力，进而推动植物盖度提升。植被丰度的增加将对初级消费者产生影响——通过提升可食用饲草的供给量，同时也会作用于全球碳收支——因为永久冻土与植被作为碳汇的功能会随之改变。北极维管植物有性生殖的增强，或会提升后代的遗传变异水平，进而改善其在变化环境中的生存几率。本研究结果同时表明，在未来增温背景下，极地绿洲或可作为周边极地荒漠景观的关键种子源发挥重要作用。