Tundra ecosystem responses to 30 years of experimental and observed changes in climate

苔原生态系统对 30 年实验和观测气候变化的反应

• 批准号: RGPIN-2019-05267
• 负责人: Henry, Gregory
• 金额: $ 2.91万
• 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: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=754789
• 关键词: Tundra; ecosystem; responses; 30; years

Tundra ecosystems have shown strong responses to recent changes in climate. Coordinated distributed experiments such as the International Tundra Experiment (ITEX) have provided critical knowledge on how these systems respond to experimental and observed changes in climate and the response variation across the tundra biome. I established the first set of ITEX studies in 1992 in seven different tundra communities at a High Arctic site on Ellesmere Island and continue to maintain the experiments. Each site has a warming treatment of transparent open-top chambers (OTCs), and in single sites warming is combined with nutrient addition and snow manipulation. Over the next 5 years, I will bring the experiments to an end and use this unique opportunity to measure the response of tundra systems to the termination of the experiments. Graduate students and postdocs will conduct field studies and use the extensive data base from the 30+ years of research at the site to answer questions linking plant traits to community and ecosystem change, to test the ability of tundra plants to adapt to a warming climate and the determine if the long-term manipulations have fundamentally altered the tundra systems. Plants in the warmed plots have consistently shown advanced phenology and increased growth and reproductive effort and success, especially those that flower early. In addition, the composition and abundance has shifted with increased cover of a few dominant species but also greater diversity. However, we have yet to link the responsiveness of the traits to the changes in biodiversity in the plots, and this will lead to better predictions of vegetation change. Students will explore these links using trait data from all of the species measured. These trait-based studies will provide one of the first assessments of temporal variability in plant traits. The warmed plots have been 1-3ºC above the ambient summer temperature for 30 years, and the ambient temperature has also increased by 2ºC since 1992. Students will help determine the trajectory of the differences between experimental and control plots continue after the treatments are removed. In the second year of the study, 50 % of the OTCs will be removed and responses followed over the next three years to examine the "relaxation" of the system to ambient conditions. Responses will be measured at the plant level (e.g., phenology, reproductive effort and success, and photosynthesis); the community level, including changes in composition and abundance; and the ecosystem level, including measurements of nutrient availability and uptake, net ecosystem exchange of CO2, and spectral characteristics of the plots. In the fifth year of the proposed study, we will conduct destructive harvests in the plots to determine changes in above and below-ground biomass (NPP) and plant traits. The bitter sweet end to these experiments will provide continued critical knowledge of tundra ecosystems as they continue to change.

苔原生态系统对最近的气候变化表现出强烈的反应。国际苔原实验（ITEX）等协调分布式实验提供了关于这些系统如何响应实验和观察到的气候变化以及整个苔原生物群落响应变化的关键知识。 1992 年，我在埃尔斯米尔岛高北极地点的七个不同苔原群落中建立了第一套 ITEX 研究，并继续维持这些实验。每个地点都有透明敞顶室（OTC）的加温处理，并且在单个地点加温与营养添加和雪操纵相结合。在接下来的 5 年里，我将结束实验，并利用这个独特的机会来测量苔原系统对实验终止的响应。研究生和博士后将进行实地研究，并利用 30 多年现场研究的广泛数据库来回答将植物性状与群落和生态系统变化联系起来的问题，测试苔原植物适应气候变暖的能力，并确定长期操作是否从根本上改变了苔原系统。温暖地区的植物始终表现出先进的物候学，生长、繁殖努力和成功率增加，尤其是那些早开花的植物。此外，随着少数优势物种覆盖范围的增加以及多样性的增加，其组成和丰度也发生了变化。然而，我们尚未将这些性状的响应与地块中生物多样性的变化联系起来，这将有助于更好地预测植被变化。学生将使用所有测量物种的性状数据来探索这些联系。这些基于性状的研究将提供植物性状时间变异性的首批评估之一。 30 年来，变暖的地块一直比夏季环境温度高出 1-3°C，自 1992 年以来，环境温度也增加了 2°C。学生将帮助确定实验地块和对照地块之间的差异轨迹，在去除处理后继续存在。在研究的第二年，50% 的 OTC 将被移除，并在接下来的三年内进行响应，以检查系统对环境条件的“松弛”情况。反应将在植物层面进行测量（例如物候、繁殖努力和成功以及光合作用）；群落水平，包括组成和丰度的变化；和生态系统水平，包括养分可用性和吸收的测量、二氧化碳的净生态系统交换以及地块的光谱特征。在拟议研究的第五年，我们将在地块中进行破坏性收获，以确定地上和地下生物量（NPP）和植物性状的变化。随着苔原生态系统的不断变化，这些实验的苦涩甜蜜的结局将为它们提供持续的关键知识。