@article{shifflett_hazel_guthrie nichols_2016, title={Sub-Soiling and Genotype Selection Improves Populus Productivity Grown on a North Carolina Sandy Soil}, volume={7}, ISSN={1999-4907}, url={http://dx.doi.org/10.3390/f7040074}, DOI={10.3390/f7040074}, abstractNote={This study reports the stem volume of 10 Populus genotypes in a randomized split-plot design with different tillage treatments (disking versus sub-soiling) after two years of growth. Height, diameter at breast height (DBH), stem aboveground volume index, survival, Melampsora rust resistance, leaf area index (LAI), chlorophyll content, and foliar nitrogen concentration (Foliar N) were measured to identify how tillage treatments might alter poplar growth. Stem volume index and LAI were positively correlated and differed significantly among tillage treatments, taxa, and genotypes. Melampsora rust resistance was also positively correlated with volume index, but significant differences were only detected among taxa and genotypes. Foliar N and chlorophyll did not correlate to stem volume for genotypes or tillage treatments. Overall, sub-soiling yielded 37% more estimated volume compared to disking. Within the sub-soiled treatments, four genotypes (140, 176, 185, and 356) had high survival (>80%) and produced substantial stem volume (>32 dm3·tree−1). These findings show that tillage practices do impact poplar stem volumes after two years and that sub-soiling improves productivity for poplar short rotation woody crops on loamy fine-sandy soils.}, number={12}, journal={Forests}, publisher={MDPI AG}, author={Shifflett, Shawn and Hazel, Dennis and Guthrie Nichols, Elizabeth}, year={2016}, month={Mar}, pages={74} }
 @article{sharpe_nichols_2007, title={Use of stable nitrogen isotopes and permeable membrane devices to study what factors influence freshwater mollusk survival in the Conasauaga river}, volume={132}, ISSN={["1573-2959"]}, DOI={10.1007/s10661-006-9533-x}, abstractNote={Recent biological inventory data shows severe declines in freshwater mussel abundance and biodiversity in the Conasauga River Basin in Northwest Georgia, USA. Based on assessments of habitat conditions, mussel populations should be sustainable. We conducted a study of sediment and water quality to evaluate the impact of anthropogenic contamination on mussel populations. Permeable membrane devices (PMD), polar organic chemical integrative samplers (POCIS), conventional water and sediment quality analyses, and stable nitrogen isotope ratio analyses (delta15N) of snails and sediments were used to assess sediment and water quality at target sites throughout the basin. Ambient concentrations of organic contaminants in water were well below any aquatic life criteria; concentrations of some nutrients were detected above aquatic life criteria levels. Most mussel species in the river are endangered or threatened; therefore, snails were collected for delta15N analyses. Mean delta15N values for snails collected at forested upper watershed sites (national forest areas) were significantly lower than delta15N values from snails in agricultural areas. Delta15N values for raw cow manure and manure-treated soil were similar to delta15N values for snails collected in agricultural areas. Dissolved nitrate from water samples had elevated delta15N values similar to the upper range of delta15N values for snails in agricultural areas. Data, particularly stable nitrogen isotope data, indicates that a land use change from national forest land to agriculture alters nitrogen sources to the basin and snails. Implications of nutrient release on freshwater molluscan reproduction, growth, and survival are discussed.}, number={1-3}, journal={ENVIRONMENTAL MONITORING AND ASSESSMENT}, author={Sharpe, Adam J. and Nichols, Elizabeth Guthrie}, year={2007}, month={Sep}, pages={275–295} }
 @article{gregory_shea_guthrie-nichols_2005, title={Impact of vegetation on sedimentary organic matter composition and polycyclic aromatic hydrocarbon attenuation}, volume={39}, ISSN={["1520-5851"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-22344433253&partnerID=MN8TOARS}, DOI={10.1021/es048028o}, abstractNote={Results from natural and engineered phytoremediation systems provide strong evidencethatvegetated soils mitigate polycyclic aromatic hydrocarbon (PAH) contamination. However, the mechanisms by which PAH mitigation occurs and the impact of plant organic matter on PAH attenuation remain unclear. This study assessed the impact of plant organic matter on PAH attenuation in labile and refractory sediments fractions from a petroleum distillate waste pit that has naturally revegetated. Samples were collected in distinct zones of barren and vegetated areas to assess changes to organic matter composition and PAH content as vegetation colonized and became established in the waste pit. Sediments were fractionated into bulk sediment and humin fractions and analyzed for organic matter composition by isotope ratio mass spectrometry (delta (13)C), 13C nuclear magnetic resonance (13C NMR), delta 14C AMS (accelerator mass spectrometry), and percent organic carbon (%TOC). Gas chromatography mass spectrometry (GC/ MS) of lipid extracts of SOM fractions provided data for PAH distribution histograms, compound weathering ratios, and alkylated and nonalkylated PAH concentrations. Inputs of biogenic plant carbon, PAH weathering, and declines in PAH concentrations are most evidentfor vegetated SOM fractions, particularly humin fractions. Sequestered PAH metabolites were also observed in vegetated humin. These results show that plant organic matter does impact PAH attenuation in both labile and refractory fractions of petroleum distillate waste.}, number={14}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Gregory, ST and Shea, D and Guthrie-Nichols, E}, year={2005}, month={Jul}, pages={5285–5292} }
 @article{guthrie-nichols_grasham_kazunga_sangaiah_gold_bortiatynski_salloum_hatcher_2003, title={The effect of aging on pyrene transformation in sediments}, volume={22}, ISSN={["1552-8618"]}, DOI={10.1897/1551-5028(2003)022<0040:TEOAOP>2.0.CO;2}, number={1}, journal={ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY}, author={Guthrie-Nichols, E and Grasham, A and Kazunga, C and Sangaiah, R and Gold, A and Bortiatynski, J and Salloum, M and Hatcher, P}, year={2003}, month={Jan}, pages={40–49} }