Collaborative Research: Environmental and biological controls on carbon uptake phenology in permafrost affected boreal forests

合作研究：对受永久冻土影响的北方森林碳吸收物候的环境和生物控制

• 批准号: 2022889
• 负责人: Jennifer Watts
• 金额: $ 47.32万
• 依托单位: Woodwell Climate Research Center, Inc.
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-09-01 至 2024-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2022889&HistoricalAwards=false
• 关键词: Collaborative; Research; Environmental; biological; controls

Rapid warming in boreal forests has driven diverse ecosystem changes in recent decades, including permafrost thaw, longer non-frozen seasons, and warmer summers. The impact of these changes on the carbon balance of boreal forests remains highly uncertain. A growing body of evidence indicates that boreal forests are shifting toward being a net carbon dioxide source due to increases in soil respiration. To offset this loss of carbon, ecosystems rely on sustained vegetation uptake and accumulation of carbon through plant photosynthesis. However, it is unclear how environmental conditions, particularly moisture and temperature, affect the timing, duration and magnitude of photosynthetic carbon uptake (i.e., photosynthetic phenology) across boreal plant functional types. To address these important knowledge gaps, this study focuses on a leaf-to-watershed analysis at the Caribou-Poker Creek (BONA) Watershed in Alaska. Specifically, the study seeks to answer the question, “What are the environmental and biological controls of photosynthetic phenology in permafrost-affected boreal forests?” This research will provide training to undergraduate and graduate students in field and laboratory research practices. The project will also partner with science educators within the PolarTREC program to develop informational StoryMaps, educational videos, and learning activities to raise public awareness of the important ecosystem services that boreal forests provide to society. This study will use a novel approach that incorporates high-frequency observations of solar-induced chlorophyll fluorescence (SIF) as an indicator of vegetation gross primary productivity (GPP), and L-band microwave backscattering intensity as an indicator of canopy water content. These measurements will be complemented by a suite of observations including leaf and ecosystem gas exchange, and environmental measurements (e.g., soil temperature, soil moisture, water flow velocity) along a soil-to-vegetation continuum. The observation will be used to identify the key functional relationships between GPP and environmental conditions occurring at the stand and watershed levels through statistical analyses (e.g., multivariate adaptive regression splines). Newly gained insight will be used to optimize a data and process-model integration framework using the remote-sensing driven CARbon Data Model (CARDAMOM) and to extend from the BONA watershed to the boreal forests of Alaska and northwestern Canada. The CARDAMOM framework will allow us to: (1) obtain new, observation-constrained, regional estimates of GPP; (2) assess the regional sensitivity of boreal carbon dioxide uptake under various climate scenarios; and (3) identify the sink potential and trajectory of GPP in boreal forests, given the state of climate warming, a lengthening growing season, and changes in soil water conditions. The study results will be an important step forward in reducing uncertainty in GPP budget estimates for boreal forests, and will help set priorities for future model improvements. This project is co-funded by the OPP Arctic Natural Sciences Program and DEB Ecosystem Science Program.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

北方森林的快速变暖驱动了近几十年来的潜水员生态系统的变化，包括永久冻结，较长的非冷冻季节和夏季温暖的夏季。这些变化对北方森林碳平衡的影响仍然高度不确定。越来越多的证据表明，由于土壤呼吸的增加，北方森林正在转变为二氧化碳源。为了抵消这种碳的损失，生态系统依赖于通过植物光合作用的持续植被吸收和碳积累。然而，尚不清楚环境条件，尤其是水分和温度如何影响北极植物功能类型的光合碳吸收的时间，持续时间和幅度。为了解决这些重要的知识差距，本研究的重点是在阿拉斯加的Caribou-Poker Creek（Bona）分水岭进行叶到胜利分析。具体而言，该研究试图回答以下问题：“在受到长期影响的北方森林中，光合作用的环境和生物学控制是什么？”这项研究将为领域和实验室研究实践的本科生和研究生提供培训。该项目还将在PolarTrec计划中与科学教育合作，以开发信息故事图，教育视频和学习活动，以提高公众对北方森林为社会提供的重要生态系统服务的认识。这项研究将使用一种新型方法，该方法融合了太阳能诱导的叶绿素荧光（SIF）的高频观察，作为植被总生产率（GPP）的指标，以及L波段微波后散射强度作为冠层水含量的指示。这些测量将通过一系列观测值来完成，包括叶子和生态系统气体交换以及沿土壤到蔬菜连续体的环境测量（例如土壤温度，土壤水分，水流速度）。该观察结果将用于确定通过统计分析（例如，多变量自适应回归花样本），通过统计分析在架子和流域水平上发生的GPP与环境条件之间的关键功能关系。新获得的洞察力将用于使用遥感驱动的碳数据模型（Cardamom）来优化数据和过程模型集成框架，并从Bona Patershed延伸到阿拉斯加和加拿大西北部的北方森林。豆蔻框架将使我们能够：（1）获得GPP的新的，观察约束的区域估计； （2）评估在各种气候场景下北方二氧化碳吸收的区域敏感性； （3）鉴于气候变暖的状态，延长的生长季节以及土壤水状况的变化，确定了北方森林中GPP的下沉潜力和轨迹。研究结果将是减少北方森林GPP预算估算的不确定性的重要一步，并将有助于为未来的模型改进设定优先级。该项目由OPP北极自然科学计划和DEB生态系统科学计划共同资助。该奖项反映了NSF的法定任务，并使用基金会的知识分子优点和更广泛的影响审查标准，认为通过评估被认为是珍贵的支持。