Species and ecosystem constraints on greening High Arctic tundra in a changing climate

气候变化下高北极苔原绿化的物种和生态系统限制

• 批准号: RGPIN-2014-05129
• 负责人: Henry, Gregory
• 金额: $ 3.28万
• 依托单位: University of British Columbia
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=632161
• 关键词: Species; ecosystem; constraints; greening; Arctic

Arctic tundra ecosystems are showing responses to the changing climate including a general increase in plant cover, which has been observed at plot and regional scales. This increase in “greenness” is largely due to greater shrub height and cover in southern Arctic areas. These changes in plant composition and abundance will have important consequences for the tundra ecosystems, including changes in wildlife forage and habitat. It will also affect the climate, as the dense leaf canopy will absorb more sunlight and result in further heating of the atmosphere. Plant cover in the High Arctic is much more restricted, with large areas sparsely vegetated. Changes in these systems will depend on successful establishment of new individuals of existing species and from the regional species pool. However, little is known of the reproductive effort and success and establishment of these species, or the potential for establishment of southern ecotypes in more northern High Arctic landscapes. Hence, a major objective of the proposed research is to improve our understanding of the impact of changes in climate (temperature and precipitation regimes and growing season length) on the reproductive effort and success and establishment of high Arctic tundra plant species. We will also test the ability of southern ecotypes to establish, grow and reproduce relative to local ecotypes under experimental climate change.My students and I will use a combination of established and new field experiments in a variety of High Arctic tundra communities at at research site on Ellesmere Island, and growth chamber and greenhouse studies at UBC. In 1992, I established and have maintained a set of passive warming experiments, using open top chambers (OTCs) in six tundra plant communities at a High Arctic lowland oasis. New experiments will be established that combine warming (OTCs), changes in snow cover (snow fences) and additional summer rain to simulate expected changes in temperature and precipitation. Seeds of the common species will be collected at the site and from southern areas of the High Arctic Islands, germinated and seedlings planted into common garden experiments at the research site. The common gardens will have OTCs installed in half the plots. These experiments will allow us to examine differences in traits related to fitness in populations of High Arctic tundra species and determine which species and which ecotypes will be more successful in establishing new populations. Reproductive effort (e.g. flower size, number of flowers and seeds, seed weight) and success (e.g. germination rate) and a set of other traits (e.g. phenology, growth, leaf traits) will be measured on individuals in all experiments. We will continue to measure composition and abundance of plant species using our standardized methods. We will also measure the effect of the experimental treatments on CO2 flux using a portable photosynthesis system. My proposed research will help to determine the potential and constraints for increased plant cover in the High Arctic in response to the rapidly warming climate. We will gain a much better understanding of the ability of common plant species to reproduce and establish under climate change conditions, and whether southern ecotypes can establish in more northern areas as the climate warms. The predicted increase in plant cover of the High Arctic will have important consequences at local, regional and global scales, and my proposed research will provide important contributions to our understanding of these consequences.

北极苔原生态系统正在对气候变化作出反应，包括在地块和区域尺度上观察到的植物覆盖普遍增加。“绿色”的增加主要是由于北极南部地区灌木高度和覆盖率的增加。这些植物组成和丰富度的变化将对苔原生态系统产生重要影响，包括野生动物饲料和栖息地的变化。它也会影响气候，因为浓密的树叶树冠会吸收更多的阳光，导致大气进一步升温。高北极地区的植物覆盖要有限得多，大片地区植被稀疏。这些系统的变化将取决于现有物种和区域物种库中新个体的成功建立。然而，很少有人知道这些物种的繁殖努力和成功和建立，或在更多的北方高北极景观建立南方生态型的潜力。因此，拟议的研究的一个主要目标是提高我们对气候变化（温度和降水制度和生长季节长度）对北极苔原植物物种的繁殖努力和成功建立的影响的理解。我们还将测试在实验性气候变化下，南方生态类型相对于当地生态类型的建立、生长和繁殖能力。我和我的学生将在埃尔斯米尔岛的研究地点，在各种高北极苔原群落中使用既有和新的野外实验相结合的方法，以及在不列颠哥伦比亚大学的生长室和温室研究。1992年，我建立并维持了一套被动变暖实验，在高北极低地绿洲的六个苔原植物群落中使用开顶室（OTCs）。将建立新的实验，结合联合收割机变暖（OTCs），雪覆盖（雪栅栏）和额外的夏季降雨的变化，以模拟预期的温度和降水量的变化。将在研究地点和高北极群岛南部地区收集常见物种的种子，发芽并将幼苗种植到研究地点的共同花园实验中。公共花园将在一半的地块上安装OTC。这些实验将使我们能够研究与高北极苔原物种种群适应性相关的性状差异，并确定哪些物种和哪些生态型在建立新种群方面更成功。在所有实验中，将对个体测量生殖努力（例如花大小、花和种子的数量、种子重量）和成功（例如发芽率）以及一组其他性状（例如物候、生长、叶性状）。我们将继续使用我们的标准化方法测量植物物种的组成和丰富度。我们还将使用便携式光合作用系统测量实验处理对CO2通量的影响。我提出的研究将有助于确定在高北极地区增加植物覆盖的潜力和限制，以应对迅速变暖的气候。我们将更好地了解常见植物物种在气候变化条件下繁殖和建立的能力，以及随着气候变暖，南方生态型是否可以在更多的北方地区建立。预计北极高纬度地区植物覆盖的增加将在地方、区域和全球范围内产生重要影响，我提出的研究将为我们理解这些影响做出重要贡献。