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

University Of Delaware, Newark DE

Investigators

Abstract

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.