Collaborative Research: The roles of plant roots, mycorrhizal fungi and uptake of deep nitrogen in the permafrost carbon feedback to warming climate

合作研究：植物根、菌根真菌和深层氮吸收在永久冻土碳反馈中对气候变暖的作用

• 批准号: 1504312
• 负责人: Michelle Mack
• 金额: $ 75.44万
• 依托单位: Northern Arizona University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-06-01 至 2021-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1504312&HistoricalAwards=false
• 关键词: Collaborative; Research; roles; plant; roots

NontechnicalRelease of carbon frozen in permafrost (frozen ground) has been identified as one of the strongest and most likely positive feedbacks between the biosphere and the warming climate. Permafrost nitrogen release has the potential to stabilize the response of the carbon cycle to climate warming because it is a negative, within-system feedback. It could confer resilience to ecosystem-atmosphere interactions in a warming Arctic. The research under this award will advance understanding of the arctic system by incorporating this feedback into a terrestrial biosphere model used extensively by the community for forecasting arctic environmental change and its links to the Earth system.The collaborative nature of the project will build partnerships between ecosystem ecologists and molecular biologists, creating new knowledge about the role of plant-fungal mutualisms in Earth system feedback cycles. The project will support career development of two female arctic scientists at the postdoctoral or new faculty level. It will contribute to the training of two graduate students in biogeosciences, ecology, and molecular biology, and provide an authentic field or laboratory research experience for about twenty undergraduate students. The project will contribute to broadening participation of under-represented groups in ecological and environmental sciences.TechnicalAbout 1,700 Pg of organic carbon (C) reside in the permafrost soils and sediments of Arctic and Boreal regions. Because this stock is more than twice the size of the atmospheric C pool, there is considerable interest in understanding how the C balance of permafrost ecosystems will respond to observed and predicted climate warming. As permafrost soils thaw, organic matter that has been cryogenically protected for hundreds to thousands of years is exposed to microbial decomposition and released to the atmosphere as greenhouse gases. One key factor that may strongly influence C balance in these ecosystems is the concurrent release of nitrogen (N), the element most likely to limit plant productivity. Release of N at or after thaw could increase plant N availability, stimulate plant C uptake and offset or balance permafrost C emissions. Although scientists acknowledge the key role N is likely to play in the permafrost C feedback to climate, there have been few empirical studies of the factors that control its fate in warming permafrost ecosystems. The objective of this project is to develop a mechanistic understanding of the role of permafrost N in the C balance of Alaskan tundra landscapes underlain by permafrost soils.The project will focus on plant acquisition of permafrost N because in most N-limited terrestrial ecosystems, plant uptake is the dominant fate of N released by microbial processes. Plants depend on fungal partners to access N beyond the reach of roots, so this research will also focus on plant mycorrhizal status and fungal community composition to elucidate the role fungal symbionts play in plant N acquisition. Finally, other fates of permafrost N will be explored, including stasis and loss. Proposed research will explore three general questions: What is the potential for release of plant-available nitrogen from thawing permafrost soil organic matter; what proportion of N released deep in the soil profile, at the base of the active layer, is acquired by mycorrhizae and plants and what are the key biotic and abiotic factors that control acquisition; and how will permafrost thaw and N release affect net ecosystem carbon balance and net biogeochemical radiative forcing from permafrost thaw at local and regional scales?The research approach includes three elements: observations of plants, fungi and soils across a regional survey of upland tundra ecological landscape units on the North Slope of the Brooks Range, Alaska; occupying intensive research sites in cold and warm moist acidic tundra, where measurements of mycorrhizal fungi and plant N acquisition and N loss will be made within long-term warming experiments and well-characterized natural thaw gradients; and modeling and regional integration with a terrestrial biosphere model specifically developed to simulate C and N dynamics in high latitude systems.

非技术性地释放永久冻土（冻土）中冻结的碳已被认为是生物圈与气候变暖之间最强烈且最有可能的正反馈之一。永久冻土氮释放有可能稳定碳循环对气候变暖的响应，因为它是一种负的系统内反馈。它可以赋予北极变暖时生态系统与大气相互作用的恢复能力。该奖项下的研究将通过将这些反馈纳入陆地生物圈模型来增进对北极系统的了解，该模型被社区广泛使用，用于预测北极环境变化及其与地球系统的联系。该项目的协作性质将在生态系统之间建立伙伴关系生态学家和分子生物学家，创造了关于植物-真菌互利共生在地球系统反馈循环中的作用的新知识。该项目将支持两名博士后或新教师级别的女性北极科学家的职业发展。它将有助于培养两名生物地球科学、生态学和分子生物学研究生，并为大约二十名本科生提供真实的现场或实验室研究经验。该项目将有助于扩大生态和环境科学领域代表性不足的群体的参与。技术大约 1,700 Pg 的有机碳 (C) 存在于北极和北方地区的永久冻土和沉积物中。由于该碳库的大小是大气碳库的两倍多，因此人们对了解永久冻土生态系统的碳平衡如何响应观测和预测的气候变暖产生了很大的兴趣。随着永久冻土的融化，被低温保护了数百年至数千年的有机物暴露于微生物分解中，并以温室气体的形式释放到大气中。可能强烈影响这些生态系统中碳平衡的一个关键因素是氮（N）的同时释放，氮是最有可能限制植物生产力的元素。解冻时或解冻后释放氮可以增加植物氮的利用率，刺激植物吸收碳并抵消或平衡永久冻土碳排放。尽管科学家们承认氮可能在永久冻土碳对气候的反馈中发挥关键作用，但对于控制其在变暖的永久冻土生态系统中的命运的因素却很少进行实证研究。该项目的目标是从机械角度理解永久冻土氮在永久冻土土壤下的阿拉斯加苔原景观碳平衡中的作用。该项目将重点关注植物对永久冻土氮的获取，因为在大多数氮受限的陆地生态系统中，植物会获取永久冻土氮。吸收是微生物过程释放氮的主要命运。植物依靠真菌伙伴来获取根部无法到达的氮，因此这项研究还将重点关注植物菌根状态和真菌群落组成，以阐明真菌共生体在植物氮获取中所起的作用。最后，将探讨永久冻土氮的其他命运，包括停滞和损失。拟议的研究将探讨三个一般性问题：从解冻的永久冻土土壤有机质中释放植物有效氮的潜力有多大？活性层底部土壤剖面深处释放的氮有多少比例被菌根和植物获取，以及控制获取的关键生物和非生物因素是什么；永久冻土融化和氮释放将如何影响当地和区域尺度的净生态系统碳平衡和永久冻土融化带来的净生物地球化学辐射强迫？研究方法包括三个要素：通过高地苔原生态景观区域调查对植物、真菌和土壤进行观察阿拉斯加布鲁克斯山脉北坡的单位；占据寒冷和温暖潮湿的酸性苔原的密集研究地点，将在长期变暖实验和充分表征的自然解冻梯度中测量菌根真菌和植物氮的吸收和损失；使用专门开发用于模拟高纬度系统中的碳和氮动态的陆地生物圈模型进行建模和区域整合。