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: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=715165
• 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.

冻土带生态系统对最近的气候变化表现出强烈的反应。协调的分布式实验，如国际冻土带实验，提供了关于这些系统如何对实验和观察到的气候变化以及整个冻土带生物群的响应变化作出反应的关键知识。1992年，我在埃尔斯米尔岛一个北极高地的七个不同苔原群落中建立了第一套ITEX研究，并继续进行实验。每个地点都有透明开顶室(OTC)的升温处理，在单个地点，升温与养分添加和积雪处理相结合。在接下来的5年里，我将结束这些实验，并利用这个独特的机会来测量冻土带系统对实验终止的反应。研究生和博士后将进行实地研究，并使用现场30多年研究的广泛数据库来回答将植物特征与群落和生态系统变化联系起来的问题，测试冻土带植物适应气候变暖的能力，并确定长期的操作是否从根本上改变了冻土带系统。 温暖地块的植物一直表现出更高的物候期，生长和繁殖努力和成功的增加，特别是那些开花较早的植物。此外，组成和丰度发生了变化，少数优势物种的盖度增加了，但多样性也更大了。然而，我们还没有将这些特征的响应与地块中生物多样性的变化联系起来，这将导致对植被变化的更好预测。学生们将使用所有被测量物种的特征数据来探索这些联系。这些基于特性的研究将提供对植物特性时间变异性的第一批评估之一。 30年来，温暖的地块一直比夏季环境温度高出1-3摄氏度，自1992年以来，环境温度也上升了2摄氏度。学生们将帮助确定实验区和控制区之间的差异轨迹，在移除处理后继续进行。在研究的第二年，将拆除50%的OTC，并在未来三年跟踪回应，以检查系统对周围环境条件的“放松”情况。将在植物层面(例如，物候、繁殖努力和成功以及光合作用)、群落层面，包括组成和丰度的变化；以及生态系统层面，包括测量养分的可获得性和吸收、二氧化碳的净生态系统交换，以及地块的光谱特征来衡量响应。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。随着冻土带生态系统的不断变化，这些实验的苦涩甜蜜结局将提供对它们的持续批判性知识。