Norwegian Institute for Nature Research (NINA), FRAM - High North Research Centre for Climate and the Environment, Langnes, PO Box 6606, 9296, Tromsø, Norway.
Department of Ecological Science, VU University Amsterdam, De Boelelaan 1085, 1081 HV, Amsterdam, The Netherlands.
Planta. 2018 Mar;247(3):635-648. doi: 10.1007/s00425-017-2813-6. Epub 2017 Nov 21.
Evergreen plants are more vulnerable than grasses and birch to snow and temperature variability in the sub-Arctic. Most Arctic climate impact studies focus on single factors, such as summer warming, while ecosystems are exposed to changes in all seasons. Through a combination of field and laboratory manipulations, we compared physiological and growth responses of dominant sub-Arctic plant types to midwinter warming events (6 °C for 7 days) in combination with freezing, simulated snow thaw and nitrogen additions. We aimed to identify if different plant types showed consistent physiological, cellular, growth and mortality responses to these abiotic stressors. Evergreen dwarf shrubs and tree seedlings showed higher mortality (40-100%) following extreme winter warming events than Betula pubescens tree seedlings and grasses (0-27%). All species had growth reductions following exposure to - 20 °C, but not all species suffered from - 10 °C irrespective of other treatments. Winter warming followed by - 20 °C resulted in the greatest mortality and was strongest among evergreen plants. Snow removal reduced the biomass for most species and this was exacerbated by subsequent freezing. Nitrogen increased the growth of B. pubescens and grasses, but not the evergreens, and interaction effects with the warming, freezing and snow treatments were minor and few. Physiological activity during the winter warming and freezing treatments was inconsistent with growth and mortality rates across the plants types. However, changes in the membrane fatty acids were associated with reduced mortality of grasses. Sub-Arctic plant communities may become dominated by grasses and deciduous plants if winter snowpack diminishes and plants are exposed to greater temperature variability in the near future.
常绿植物比草和桦树更容易受到亚北极地区雪和温度变化的影响。大多数北极气候影响研究都集中在单一因素上，如夏季变暖，而生态系统则受到所有季节变化的影响。通过野外和实验室的综合处理，我们比较了亚北极地区主要植物类型对仲冬变暖事件（6°C 持续 7 天）的生理和生长反应，同时还模拟了融雪和氮添加。我们的目的是确定不同的植物类型是否对这些非生物胁迫表现出一致的生理、细胞、生长和死亡率反应。与桦树幼苗和草（0-27%）相比，常绿矮灌木和树苗在经历极端冬季变暖事件后死亡率（40-100%）更高。所有物种在暴露于-20°C 后生长都受到抑制，但并非所有物种在不受其他处理影响的情况下都能耐受-10°C。冬季变暖后再经历-20°C，会导致最高的死亡率，而常绿植物受影响最大。除雪会减少大多数物种的生物量，而随后的冻结会使这种情况恶化。氮增加了桦树和草的生长，但不会增加常绿植物的生长，而且与变暖、冻结和融雪处理的相互作用很小。在冬季变暖期和冻结期的生理活动与不同植物类型的生长和死亡率不一致。然而，细胞膜脂肪酸的变化与草类死亡率的降低有关。如果亚北极地区的积雪减少，并且植物在不久的将来暴露在更大的温度变化下，那么植物群落可能会由草类和落叶植物主导。
