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Biogeochemical Modeling Of The Response Of Forest Watersheds In The Northeastern U.S. To Future Climate Change, Afshin Pourmokhtarian

Dissertations - ALL

In this dissertation I assessed the potential hydrochemical responses of future climate change conditions on forested watersheds in the northeastern U.S. using climate projections from several atmosphere ocean general circulation models (AOGCMs) under different carbon dioxide (CO2) emissions scenarios. The impacts of changing climate on terrestrial ecosystems have been assessed by observational, gradient, laboratory and field studies; however, state-of-the-art biogeochemical models provide an excellent tool to investigate climatic perturbations to these complex ecosystems. The overarching goal of this dissertation was to apply a fully integrated coupled hydrological and biogeochemical model (PnET-BGC) to evaluate the effects of climate change and increasing …

Soil Mercury And Its Response To Atmospheric Mercury Deposition Across The Northeastern United States, Xue Yu, Charles T. Driscoll, Richard A. F. Warby, Mario Montesdeoca, Chris E. Johnson

Civil and Environmental Engineering

Terrestrial soil is a large reservoir of atmospherically deposited mercury (Hg). However, few studies have evaluated the accumulation of Hg in terrestrial ecosystems in the northeastern United States, a region which is sensitive to atmospheric Hg deposition. We characterized Hg and organic matter in soil profiles from 139 sampling sites for five subregions across the northeastern United States and estimated atmospheric Hg deposition to these sites by combining numerical modeling with experimental data from the literature. We did not observe any significant relationships between current net atmospheric Hg deposition and soil Hg concentrations or pools, even though soils are a …

Compositional Characterization Of Soil Organic Matter And Hot-Water Extractable Organic Matter In Organic Horizons Using A Molecular Mixing Model, Ankit Balaria, Chris E. Johnson

Civil and Environmental Engineering

Purpose Microbial decomposition of soil organic matter (SOM) is generally believed to be heterogeneous, resulting in the preferential loss of labile compounds such as carbohydrates and proteins and the accumulation of recalcitrant compounds such as lipids and lignin. However, these fractions are difficult to measure directly in soils. We examined patterns in the biomolecular composition of SOM and hot-water-extractable organic matter (HWEOM) by using a molecular mixing model (MMM) to estimate the content of carbohydrates, protein, lipids, and lignin.

Materials and methods Organic-horizon soils from Spodosols at the Hubbard Brook Experimental Forest in New Hampshire, USA were analyzed for this …

A 13c Nmr Study Of Decomposing Logging Residues In An Australian Hoop Pine Plantation, Chris E. Johnson, Timothy J. Blumfield, Sue Boyd, Zhihong Xu

Civil and Environmental Engineering

Purpose Residue retention is important for nutrient and water economy in sub-tropical plantation forests. We examined decomposing hoop pine (Araucaria cunninghamii Ait. Ex D. Don) residues – foliage, branches and stem wood – to determine the changes in structural chemistry that occur during decomposition.

Materials and methods Residues were incubated in situ using 0.05-m² microplots. We used solid-state ¹³C nuclear magnetic resonance (NMR) spectroscopy to determine the structural composition of harvest residues in the first 24 months of decomposition.

Results and discussion The spectral data for branch and stem residues were generally similar to one another and …

Soil Chemistry Response To Wollastonite (Casio3) Addition At Hubbard Brook, Chris E. Johnson

Civil and Environmental Engineering

No abstract provided.

Mercury Concentrations In Tropical Resident And Migrant Songbirds On Hispaniola, Jason M. Townsend, Christopher C. Rimmer, Charles T. Driscoll, Kent P. Mcfarland, Eduardo E. Inigo-Elias

Civil and Environmental Engineering

Despite growing concerns over mercury (Hg) exposure to humans and wildlife on a global scale, little is known about Hg bioaccumulation in the New World tropics. From 2005 to 2011, we monitored Hg concentrations in blood of nine avian species occupying a geographic range of tropical wet broadleaf sites on the island of Hispaniola, including eight passerines (two Nearctic- Neotropical migrant and six resident species) and one top order predatory accipiter. Invertivorous songbirds were further differentiated by foraging guild, with six species of groundforagers and two species of foliage-gleaners. Blood Hg concentrations were orders of magnitude higher in birds sampled …