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Craig Guyer 5.31.16
No full textThis interview with Dr. Craig Guyer was conducted by Robert Gitzen and Patricia Hartman on May 31, 2016, as part of the Cultural History of Alabama Wildlife Project. The interview consists of an audio file and transcript. In the interview, Dr. Guyer recounts his career as a herpetologist and professor of Biological Sciences at Auburn University. Subjects include his research in Conecuh National Forest, including the 2010 Eastern indigo snake reintroduction; observed changes in local wildlife populations since his arrival in 1987; longleaf pine ecology and conservation; and local attitudes toward wildlife
Century-long increasing trend and variability of dissolved organic carbon export from the Mississippi River basin driven by natural and anthropogenic forcing
Get PDFThere has been considerable debate as to how natural forcing and anthropogenic activities alter the timing and magnitude of the delivery of dissolved organic carbon (DOC) to the coastal ocean, which has ramifications for the ocean carbon budget, land-ocean interactions, and coastal life. Here we present an analysis of DOC export from the Mississippi River to the Gulf of Mexico during 1901-2010 as influenced by changes in climate, land use and management practices, atmospheric CO2, and nitrogen deposition, through the integration of observational data with a coupled hydrologic/biogeochemical land model. Model simulations show that DOC export in the 2000s increased more than 40% since the 1900s. For the recent three decades (1981-2010), however, our simulated DOC export did not show a significant increasing trend, which is consistent with observations by U.S. Geological Survey. Our factorial analyses suggest that land use and land cover change, including land management practices (LMPs: i.e., fertilization, irrigation, tillage, etc.), were the dominant contributors to the century-scale trend of rising total riverine DOC export, followed by changes in atmospheric CO2, nitrogen deposition, and climate. Decadal and interannual variations of DOC export were largely attributed to year-to-year climatic variability and extreme flooding events, which have been exacerbated by human activity. LMPs show incremental contributions to DOC increase since the 1960s, indicating the importance of sustainable agricultural practices in coping with future environmental changes such as extreme flooding events. Compared to the observational-based estimate, the modeled DOC export was 20% higher, while DOC concentrations were slightly lower. Further refinements in model structure and input data sets should enable reductions in uncertainties in our prediction of century-long trends in DOC.PublishedYe
Kinetic Alfven waves in three-dimensional magnetic reconnection
Get PDFAlfvenic waves are believed to be fundamentally important in magnetic reconnection. Kinetic dynamics of particles can break the Alfven speed limit in the evolution and propagation of perturbations during reconnection. In this paper, the generation and signatures of kinetic Alfven waves (KAWs) associated with magnetic reconnection in a current sheet is investigated using a three-dimensional (3-D) hybrid code under a zero or finite guide field. In order to understand the wave structures in the general cases of multiple X line reconnection, cases with a single X line of various lengths are examined. The KAWs are identified using the wave dispersion relation, electromagnetic polarization relations, as well as spectral analysis. In the cases in which the X line is so long to extend through the entire simulation domain in the current direction, quasi 2-D configurations of reconnection are developed behind a leading flux/plasma bulge. KAWs with perpendicular wave number k(i)approximate to 1 (with (i) being the ion Larmor radius) are found throughout the transient plasma bulge region and propagate outward along magnetic field lines with a slightly super-Alfvenic velocity. These KAWs are generated from the X line and coexist with the whistler structure of the ion diffusion region under a small guide field. In the cases in which the X line has a finite length 2 approximate to 10d(i), with being the half length of the X line and d(i) the ion inertial length, the KAWs originated from the X line are of 3-D nature. Under a finite guide field, KAWs propagate along the oblique magnetic field lines into the unperturbed regions in the current direction, carrying parallel electric field and Poynting fluxes. The critical X line length for the generation of 3-D-like structures is found to be 2(c)30d(i). The structure, propagation, energy, spectrum, and damping of the KAWs are examined. Dependence of the structure of KAWs on the guide field is also investigated.PublishedYe
Methane emissions from global rice fields: Magnitude, spatiotemporal patterns, and environmental controls
Get PDFGiven the importance of the potential positive feedback between methane (CH4) emissions and climate change, it is critical to accurately estimate the magnitude and spatiotemporal patterns of CH4 emissions from global rice fields and better understand the underlying determinants governing the emissions. Here we used a coupled biogeochemical model in combination with satellite-derived contemporary inundation area to quantify the magnitude and spatiotemporal variation of CH4 emissions from global rice fields and attribute the environmental controls of CH4 emissions during 1901-2010. Our study estimated that CH4 emissions from global rice fields varied from 18.3 +/- 0.1 Tg CH4/yr (Avg. +/- 1 SD) under intermittent irrigation to 38.8 +/- 1.0 Tg CH4/yr under continuous flooding in the 2000s, indicating that the magnitude of CH4 emissions from global rice fields is largely dependent on different water schemes. Over the past 110 years, our simulated results showed that global CH4 emissions from rice cultivation increased by 85%. The expansion of rice fields was the dominant factor for the increasing trends of CH4 emissions, followed by elevated CO2 concentration, and nitrogen fertilizer use. On the contrary, climate variability had reduced the cumulative CH4 emissions for most of the years over the study period. Our results imply that CH4 emissions from global rice fields could be reduced through optimizing irrigation practices. Therefore, the future magnitude of CH4 emissions from rice fields will be determined by the human demand for rice production as well as the implementation of optimized water management practices.PublishedYe
Increased light-use efficiency in northern terrestrial ecosystems indicated by CO2 and greening observations
Get PDFObservations show an increasing amplitude in the seasonal cycle of CO2 (ASC) north of 45 degrees N of 56 +/- 9.8% over the last 50 years and an increase in vegetation greenness of 7.5-15% in high northern latitudes since the 1980s. However, the causes of these changes remain uncertain. Historical simulations from terrestrial biosphere models in the Multiscale Synthesis and Terrestrial Model Intercomparison Project are compared to the ASC and greenness observations, using the TM3 atmospheric transport model to translate surface fluxes into CO2 concentrations. We find that the modeled change in ASC is too small but the mean greening trend is generally captured. Modeled increases in greenness are primarily driven by warming, whereas ASC changes are primarily driven by increasing CO2. We suggest that increases in ecosystem-scale light use efficiency (LUE) have contributed to the observed ASC increase but are underestimated by current models. We highlight potential mechanisms that could increase modeled LUE.PublishedYe
Proton velocity ring-driven instabilities in the inner magnetosphere: Linear theory and particle-in-cell simulations
Get PDFLinear dispersion theory and electromagnetic particle-in-cell (PIC) simulations are used to investigate linear growth and nonlinear saturation of the proton velocity ring-driven instabilities, namely, ion Bernstein instability and Alfven-cyclotron instability, which lead to fast magnetosonic waves and electromagnetic ion cyclotron waves in the inner magnetosphere, respectively. The proton velocity distribution is assumed to consist of 10% of a ring distribution and 90% of a low-temperature Maxwellian background. Here two cases with ring speeds v(r)/v(A)=1 and 2 (v(A) is the Alfven speed) are examined in detail. For the two cases, linear theory predicts that the maximum growth rate (m) of the Bernstein instability is 0.16(p) and 0.19(p), respectively, and (m) of the Alfven-cyclotron instability is 0.045(p) and 0.15(p), respectively, where (p) is the proton cyclotron frequency. Two-dimensional PIC simulations are carried out for the two cases to examine the instability development and the corresponding evolution of the particle distributions. Initially, Bernstein waves develop and saturate with strong electrostatic fluctuations. Subsequently, electromagnetic Alfven-cyclotron waves grow and saturate. Despite their smaller growth rate, the saturation levels of the Alfven-cyclotron waves for both cases are larger than those of the Bernstein waves. Resonant interactions with the Bernstein waves lead to scattering of ring protons predominantly along the perpendicular velocity component (toward both decreasing and, at a lesser extent, increasing speeds) without substantial change of either the parallel temperature or the temperature anisotropy. Consequently, the Alfven-cyclotron instability can still grow. Furthermore, the free energy resulting from the pitch angle scattering by the Alfven-cyclotron waves is larger than the free energy resulting from the perpendicular energy scattering, thereby leading to the larger saturation level of the Alfven-cyclotron waves.Publishe
Library Alphabet Soup: Tips and Resources When the Item in Hand is Not Written in the Latin Alphabet
Get PDFIt is not uncommon for both academic and public librarians to have items, especially gift books, that are in another language that they have either to evaluate for addition to the collection or to catalog. Quite often, librarians seek the help of a colleague who knows the language. But what does one do when there is not such a person available? If the language uses the Latin alphabet, a quick WorldCat search will often do the trick for finding the basic bibliographic data and for learning at least something of its aboutness. But what if the language uses another alphabet or writing system? What if you cannot even identify the language initially? In this session, participants will be presented with tips and resources to help identify common languages that do not use the same alphabet and hopefully to help locate enough data to identify the publication and see if it is in WorldCat.unpublishedN
Reptile Embryos Lack the Opportunity to Thermoregulate by Moving within the Egg
Get PDFHistorically, egg-bound reptile embryos were thought to passively thermoconform to the nest environment. However, recent observations of thermal taxis by embryos of multiple reptile species have led to the widely discussed hypothesis that embryos behaviorally thermoregulate. Because temperature affects development, such thermoregulation could allow embryos to control their fate far more than historically assumed. We assessed the opportunity for embryos to behaviorally thermoregulate in nature by examining thermal gradients within natural nests and eggs of the common snapping turtle (Chelydra serpentina; which displays embryonic thermal taxis) and by simulating thermal gradients within nests across a range of nest depths, egg sizes, and soil types. We observed little spatial thermal variation within nests, and thermal gradients were poorly transferred to eggs. Furthermore, thermal gradients sufficiently large and constant for behavioral thermoregulation were not predicted to occur in our simulations. Gradients of biologically relevant magnitude have limited global occurrence and reverse direction twice daily when they do exist, which is substantially faster than embryos can shift position within the egg. Our results imply that reptile embryos will rarely, if ever, have the opportunity to behaviorally thermoregulate by moving within the egg. We suggest that embryonic thermal taxis instead represents a play behavior, which may be adaptive or selectively neutral, and results from the mechanisms for behavioral thermoregulation in free-living stages coming online prior to hatching.PublishedYe
Screening Pinus taeda (loblolly pine) families for physical and mechanical properties using vibrational spectroscopy
Get PDFIn a bid to control the loblolly pine decline complex, stakeholders are using the selection and deployment of genetically superior families that are disease tolerant. It is vital that we do not compromise other important properties while breeding for disease tolerance. In this preliminary study, near infrared spectroscopy was utilized in conjunction with data collected via conventional methods to develop partial least squares regression models that were used to rapidly predict the basic density, stiffness and ultimate strength of 14 genetically superior loblolly pine families that have been selectively bred to be disease tolerant. Calibration and independent validation data were from southern pines acquired from a commercial sawmill. Seven or eight latent variables were used in model development. The coefficients of determination of the predictive models were more promising for MOE (0.58) and MOR (0.42)
Economic Alignment
No full textThis essay presents an overview of the economic issues that define, promote, or inhibit effective national and international programs for preserving digital cultural heritage materials. Specifically, it presents and discusses multi-institutional approaches to identifying effective and economically sustainable policies in managed digital information environments, citing current digital preservation initiatives in North America and Europe. The essay will also address related issues, including: service/user relationships, roles and responsibilities throughout the various communities, the choice of suitable business models, and cost analyses as essential components of defining economically sustainable approaches to preservation. In keeping with the aims of the Aligning National Approaches to Digital Preservation conference, the essay concludes by considering what a blueprint for success in this area might look like and offering specific recommendations to that end.PublishedYe