Doctoral Dissertation Research: Inter- and Intra-Storm Variability of Dissolved Organic Carbon and Nitrogen Fluxes from a Mid-Latitude Broadleaved Deciduous Forest Canopy

博士论文研究：中纬度阔叶落叶林冠层溶解有机碳和氮通量的风暴间和风暴内变化

• 批准号: 1003047
• 负责人: Delphis Levia
• 金额: $ 1.2万
• 依托单位: University of Delaware
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-03-15 至 2011-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1003047&HistoricalAwards=false
• 关键词: Doctoral; Dissertation; Research; Inter; Intra

Mid-latitude, deciduous forests have become increasingly important global carbon (C) and nitrogen (N) sinks as human-related emissions from fuels, biomass burning, fertilizer use, and agricultural operations grow and tropical forests are harvested. Many studies have examined C and N storage within forested ecosystems, yet few have characterized the ecohydrological dynamics of dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) derived from canopy sources. No known study has holistically examined the intra-storm variability of all canopy-derived DOC and DON fluxes for mid-latitude deciduous forests, although storm events being a critical period for the mobilization and transport of DOC and DON. Data quantifying the overall fate and transport of DOC and DON from canopy sources with respect to meteorological conditions and catchment characteristics are scant. To fill these data gaps, this doctoral dissertation research project will sample throughfall, stemflow, and litter leachate for two co-dominant tree species of contrasting canopy morphologies at the intra-storm scale and characterize the influence of meteorological conditions and catchment conditions on DOC and DON. Samples also will be analyzed for base cations for use in end-member mixing analyses (EMMA). EMMA will be used to evaluate hydrologic relationships between canopy-derived fluxes, variable source areas (VSA), and streamflow. Previous EMMAs have evaluated the influence of throughfall and litter leachate on streamflow chemistry and VSAs but neglected stemflow. The stemflow of many broadleaved deciduous trees gains preferential access to subsurface lateral flow. Hence, it is likely that the stemflow of certain species may contribute to streamflow and/or VSAs. This study will be the first to evaluate stemflow as an end-member in end-member mixing analysis and the first to monitor all canopy-derived DOC and DON fluxes for a single catchment at the intrastorm scale.Results will be used to review bulk sampling practices and assumptions made by current watershed models that generally disregard the influence of intrastorm variability and stemflow on the hydrology and water quality of forested catchments. If intrastorm variability or stemflow significantly contribute to the chemistry or hydrology of subsurface flux, VSAs, and/or streamflow for forested catchments, then widely-used models for civil engineering and environmental research and design that employ these assumptions will need to be corrected. Current bulk sampling practices also may need to be corrected if intrastorm variability significantly influences biogeochemical processes in forested catchments. Investigation of the intrasystem cycling dynamics of DOC and DON within mid-latitude deciduous forests during discrete storm events nonetheless will inform relevant theory in physical geography and hydrology that seeks to better understand the cycling of water and solutes in forests. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.

随着人类因燃料、生物质燃烧、化肥使用和农业经营造成的排放以及热带森林的砍伐，中纬度落叶林已成为越来越重要的全球碳 (C) 和氮 (N) 汇。 许多研究都研究了森林生态系统内的碳和氮储存，但很少有研究描述来自冠层来源的溶解有机碳（DOC）和溶解有机氮（DON）的生态水文动态。 尽管风暴事件是 DOC 和 DON 动员和运输的关键时期，但尚无已知的研究全面研究了中纬度落叶林所有冠层衍生的 DOC 和 DON 通量的风暴内变化。 就气象条件和流域特征而言，量化冠层源 DOC 和 DON 的总体归宿和迁移的数据很少。 为了填补这些数据空白，本博士论文研究项目将对两种具有对比树冠形态的共同优势树种在风暴内尺度下的径流、茎流和凋落物渗滤液进行采样，并表征气象条件和流域条件对 DOC 和大学教师。 还将分析样品中的碱阳离子，以用于端元混合分析 (EMMA)。 EMMA 将用于评估冠层通量、可变源区 (VSA) 和水流之间的水文关系。 以前的 EMMA 评估了径流和垃圾渗滤液对水流化学和 VSA 的影响，但忽略了茎流。 许多阔叶落叶树的茎流优先进入地下侧流。 因此，某些物种的茎流可能有助于水流和/或 VSA。 这项研究将是第一个在端元混合分析中评估茎流作为端元的研究，也是第一个在暴风雨范围内监测单个集水区所有冠层衍生的 DOC 和 DON 通量的研究。结果将用于审查批量采样当前流域模型所做的实践和假设通常忽略了风暴内变化和茎流对森林流域水文和水质的影响。 如果暴风雨内的变化或茎流对地下通量、VSA 和/或森林集水区水流的化学或水文有显着影响，那么采用这些假设的广泛使用的土木工程和环境研究和设计模型将需要进行修正。 如果暴风雨内的变化显着影响森林流域的生物地球化学过程，则当前的批量采样实践也可能需要纠正。 尽管如此，对中纬度落叶林在离散风暴事件期间 DOC 和 DON 系统内循环动态的研究将为自然地理学和水文学中的相关理论提供信息，从而更好地了解森林中水和溶质的循环。 作为博士论文研究改进奖，该奖项还将为有前途的学生建立强大的独立研究生涯提供支持。