Doctoral Dissertation Research: Synoptic Climatological Approaches to Assessing Subcanopy Hydrologic and Nutrient Fluxes in a Temperate Deciduous Forest

这个博士论文研究项目将集中在不同降水制度下，水和化学物质通过森林冠层的流动。北美和中美洲的温带落叶林面积超过2.8亿公顷，通过水和养分的循环提供重要的生态系统服务。在风暴期间，水穿过森林冠层，与植被交换营养物质和污染物，并将化学变化的降水沉积到森林地面。风暴的特征，如强度、持续时间和强度，以及森林冠层的结构参数，对这种水的数量和质量都有重要的控制作用，但是，由于气候变化而改变的降水制度如何影响这些特征在很大程度上是不确定的。该项目将使人们更好地了解通过水文途径在森林冠层内的营养物质和污染物的循环，而水文途径最终是由中大西洋地区一个实地地点的大气环流和降水模式控制的。该博士生将把天气气候学与温带森林中的水和溶质通量联系起来。气象特征每隔5分钟监测一次。这些实时地面观测将补充一个长期天气日历，该日历将用于对该区域经历的常见天气模式进行分类。在暴风雨期间，两种树皮厚度和冠层几何形状不同的树种每隔5分钟用自动倾倒桶测量降水分为透雨（被冠层拦截的水继续落在森林地面上）和茎流（被冠层拦截的水，沿树干漏斗流下，直接沉积到树的底部），以便了解异质性中降水的不同响应森林的树冠。降雨、雨水和茎流样本将在风暴事件发生后收集，并分析重要的营养物质，如溶解的有机碳、钙、镁、钾和钠，以及阴离子，如硝酸盐和硫酸盐，它们可以形成酸雨。该项目将综合天气气候学和天气模式分析技术，为估算森林冠层的水文和养分通量提供新的方法。这项研究将展示如何使用大尺度大气环流模式的天气分析来估计地表环境条件，从而减少对昂贵的、精细尺度的实地观测的需求。本研究编制的数据集将用于重建具有相似组成的中大西洋森林的历史营养收支，并可能预测气候引起的降水制度变化导致的森林水文和营养收支的变化。更透彻地了解森林生态系统中水、营养物质和污染物的运动将提高管理能力和减缓气候变化的努力。作为博士论文研究改进奖，该奖项还将提供支持，使有前途的学生建立一个强大的独立研究生涯。

This doctoral dissertation research project will focus on the flow of water and chemicals through forest canopies under different precipitation regimes. Deciduous temperate forests comprise over 280 million hectares in North and Central America and provide vital ecosystem services through the cycling of water and nutrients. During storm events, water moves through the forest canopy and exchanges nutrients and pollutants with vegetation and deposits the chemically altered precipitation to the forest floor. Both storm characteristics, such as intensity, duration, and magnitude, and the structural parameters of forest canopies have a significant control on the quantity and quality of such water, but how these may be influenced by altered precipitation regimes as a result of changing climates is largely uncertain. This project will yield a better understanding of the cycling of nutrients and pollutants within a forest canopy through hydrologic pathways that are ultimately controlled by atmospheric circulation and precipitation patterns at a field site in the Mid-Atlantic region. The doctoral student will link synoptic climatology with water and solute flux in temperate forests. Meteorological characteristics will be monitored at 5-minute intervals. These real-time ground observations will complement a long-term synoptic calendar, which will be developed to categorize common weather patterns experienced in the region. The partitioning of precipitation into throughfall (water intercepted by the canopy that continues to fall to the forest floor) and stemflow (water that is intercepted by the canopy and funneled down the tree trunk and deposited directly to the base of the tree) will be measured by automated tipping buckets at 5-minute intervals during storm events for two tree species of varying bark thickness and canopy geometry in order to understand the varying responses of precipitation in a heterogeneous forest canopy. Precipitation, throughfall, and stemflow samples will be collected after storm events and analyzed for important nutrients, such as dissolved organic carbon, calcium, magnesium, potassium, and sodium, and for anions, such as nitrates and sulfates, which can form acid rain. This project will provide new methodologies for estimating hydrologic and nutrient fluxes in forest canopies by integrating techniques of synoptic climatology and weather pattern analysis. This study will demonstrate how synoptic analysis of large-scale atmospheric circulation patterns may be used to estimate surface environmental conditions, thus reducing the demand for costly, fine-scale field observations. The dataset compiled in this study will be used to reconstruct a historical nutrient budget of Mid-Atlantic forests of similar composition and potentially forecast changes in forest hydrologic and nutrient budgets as a result of climate-induced changes to precipitation regimes. A more thorough understanding of the movement of water, nutrients, and pollutants in forest ecosystems will improve management capabilities and climate change mitigation efforts. 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.