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: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=611458
• 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.

北极冻土带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率普遍增加。绿色度的增加在很大程度上是由于北极南部地区灌木高度和盖度的增加。植物组成和丰度的这些变化将对冻土带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。它还会影响气候，因为茂密的树叶树冠会吸收更多的阳光，导致大气进一步升温。北极高地的植物覆盖范围要有限得多，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，人们对这些物种的繁殖努力、成功和建立的情况知之甚少，也不知道在更北部的北极高地景观中建立南方生态型的潜力。因此，拟议研究的一个主要目标是增进我们对气候变化(温度和降水制度以及生长季节长度)对繁殖努力和成功以及建立北极高原冻土带植物物种的影响的了解。我们还将测试南方生态型在实验气候变化下相对于当地生态型建立、生长和繁殖的能力。 我和我的学生将在埃尔斯米尔岛的研究点和不列颠哥伦比亚省的生长室和温室研究地点，结合在各种北极苔原群落进行的现有和新的实地实验。1992年，我建立并维持了一套被动变暖实验，使用的是北极高地低地绿洲的六个苔原植物群落的开顶室(OTC)。将建立新的实验，结合变暖(OTCs)、积雪覆盖的变化(雪栅栏)和额外的夏季降雨来模拟预期的温度和降水变化。这些常见物种的种子将在研究地点和北极高地群岛南部地区收集，发芽并种植到研究地点的共同花园实验中。普通花园将在一半的地块上安装OTCs。这些实验将使我们能够检验与北极高原苔原物种种群适合度相关的特征差异，并确定哪些物种和哪些生态型将在建立新种群方面更成功。在所有实验中，将对个体的繁殖努力(例如，花的大小、花和种子的数量、种子重量)和成功率(例如，发芽率)和一系列其他特征(例如，物候、生长、叶片特征)进行测量。我们将继续使用我们的标准化方法来测量植物物种的组成和丰度。我们还将使用便携式光合作用系统来测量实验处理对二氧化碳通量的影响。 我提议的研究将有助于确定北极高地植物覆盖率增加的潜力和限制因素，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生存的能力，以及随着气候变暖，南方生态型是否可以在更北部的地区建立。预计北极高海拔地区植物覆盖率的增加将在地方、区域和全球范围内产生重要后果，我提出的研究将为我们理解这些后果做出重要贡献。