Habitat Relationships of Breeding Birds in Bottomland Hardwood Forests of the Altamaha River, Georgia

Bottomland hardwood forests (bottomlands) dominate most of the river floodplains and lowlands of the southeastern United States. These vanishing and often degraded forests provide habitat for at least seventy species of breeding birds. However, little is known about habitat associations of breeding birds, specifically within mature, closed-canopy bottomlands. It is often assumed that once bottomlands become mature, closed-canopy forests, that they are essentially identical from the perspective of breeding birds. To test this assumption, I examined habitat associations of the overall breeding bird community as well as ten priority species within the little-studied mature bottomlands of the Altamaha River, Georgia. In 2007 and 2008, I conducted point-counts for breeding birds and quantified habitat characteristics at 54 stations. I detected 33 species of birds breeding at stations, 19 of which were Neotropical Migratory bird species. I found that the overall density of breeding birds, the density of breeding Neotropical species, as well as the Avian Conservation Score of stations did not closely track habitat variation within mature bottomlands. However, I found that some individual breeding species were sensitive to habitat variation within mature bottomlands. Yellow-throated vireo (Vireo flavifrons) and Hooded Warbler (Wilsonia citrina) preferred slightly less canopy cover within mature bottomlands, whereas White-eyed vireo (Vireo griseus) preferred more. Kentucky Warbler (Oporonus formosus) preferred stations with less variability in tree diameter and more shrubs. My study illustrates the significance of the Altamaha River bottomlands for the conservation of a diverse assemblage of breeding birds, including numerous Neotropical migratory species of regional conservation concern. My study also suggests that beyond allowing flooding and tree fall to occur naturally, management of mature Altamaha River bottomlands for diversity in the breeding bird community may be achieved with little active management. However, single-tree or group-selection harvests may be beneficial to a few important breeding Neotropical migratory bird species

Organic matter composition of sediments and the history of eutrophication and anoxia in the mesohaline Chesapeake Bay

To evaluate the effects of anthropogenic alteration of the Chesapeake Bay (CB) watershed since European settlement, the historical progression of eutrophication and anoxia in the mesohaline region of CB was reconstructed. Lipid biomarker and carbon and nitrogen stable isotopic and elemental composition of CB surficial sediments were examined seasonally in order to identify the present sources of organic matter to CB sediments and the processes controlling their distribution. Temporal variability in surficial sediment composition could be linked to seasonal changes in phytoplankton community composition and biomass while spatial variation was dominated by the delivery of alloclithonous versus autochthonous sources of organic matter. Three cores (3 to 4.5 m in length) collected from the mesohaline region of Chesapeake Bay were dated using a combination of tools including 210Pb and 137Cs radioisotopes, anthropogenic Pb and pollen indices. Enrichments in the carbon and nitrogen isotopic signature of sediments of all three cores deposited between 1790 and 1915 indicated enhanced primary productivity and nitrogen recycling, respectively. at the same time, increases in the flux of total organic carbon (TOC) and episodic enrichments (relative to TOC) of algal and bacterially-derived lipid biomarker compounds signaled a change in the sources of OM to the sediments. More extreme change occurred after the 1915\u27s with further isotopic enrichments, a 1.5 to 2.5-fold increase in TOC deposition and 2 to 5-fold enrichments in algal and bacterially-derived lipid biomarker compounds. No change in the contribution of terrestrially-derived OM was indicated in any of the cores. Changes in sulfur speciation identified the initial occurrence of anoxia/hypoxia in 1790 at the deepest site (26 m) and in 1929 at a 15 m depth site. An examination of both qualitative evidence and quantitative models of degradation indicates that diagenesis cannot account for the observed increases in the total amount and labile quality of OM deposited during the 19th and 20th century in CB. Using diagenetic models, it is estimated that both algal and bacterial production has increased by 100 to 200% relative to pre-Colonial times with a temporal progression similar to the history of anthropogenic alteration of the watershed

Reply to Scahill: Behavioral outcome measures in autism.

Comment on: Sulforaphane treatment of autism spectrum disorder (ASD). [Proc Natl Acad Sci U S A. 2014] Uncommon use of common measures in sulforaphane trial. [Proc Natl Acad Sci U S A. 2015

Charge Offset Stability in Si Single Electron Devices with Al Gates

We report on the charge offset drift (time stability) in Si single electron devices (SEDs) defined with aluminum (Al) gates. The size of the charge offset drift (0.15 $e$) is intermediate between that of Al/AlO$_x$/Al tunnel junctions (greater than 1 $e$) and Si SEDs defined with Si gates (0.01 $e$). This range of values suggests that defects in the AlO$_x$ are the main cause of the charge offset drift instability

Associations of occupational attributes and excessive drinking

Numerous work-related drinking mechanisms have been posited and, oftentimes, examined in isolation. We combined data from over 100 occupational attributes into several factors and tested the association of these factors with measures of alcohol use. We used the NLSY79 2006 wave, a U.S. representative sample of 6,426 workers ages 41 to 49 and the 2006 Occupational Information Network database (O*NET), a nationally representative sample of nearly 1,000 occupations. We conducted exploratory factor analysis on 119 occupational attributes and found three independent workplace characteristics – physical demands, job autonomy, and social engagement - explained the majority of the variation. We then tested the association of these composite attributes with three drinking measures, before and after adjusting for gender, race/ethnicity, and a measure of human capital using count data models. We then stratified by gender and repeated our analyses. Men working in occupations with a one standard deviation higher level of physical demand (e.g. construction) reported a higher number of heavy drinking occasions (+20%,

Lipid biomarker composition of particulate organic matter in the lower Chesapeake Bay : a final data report

In this report we present results from a sampling program designed to characterize the abundance, sources, and composition of particulate organic matter (POM) in the lower Chesapeake Bay. To meet these objectives, we used measurements of bulk parameters (total suspended solids, chlorophylls, particulate carbon and nitrogen concentrations) combined with information on the concentration of two classes of lipid biomarker compounds (fatty acids and sterols). In addition to providing baseline information on the sources and composition of POM important to the lower Bay, the study addressed spatial and temporal variations in organic matter quality. This was accomplished using an experimental design which incorporated seasonal samplings to investigate temporal variability. Spatial variability was examined by comparison of sites located at the mouths of two tributaries (York and Rappahannock Rivers) to two sites located in the Bay mainstem. A further goal of the research project was to improve our understanding of the role of biological and physical processes in controlling the distribution and quality of organic matter. This information can then be used to understand how POM composition changes spatially and temporally in this region of the CB and to provide important insights regarding the nutritional value of the POM to consumer organisms