Near-surface remote sensing of spatial and temporal variation in canopy phenology

There is a need to document how plant phenology is responding to global change factors, particularly warming trends. “Near-surface” remote sensing, using radiometric instruments or imaging sensors, has great potential to improve phenological monitoring because automated observations can be made at high temporal frequency. Here we build on previous work and show how inexpensive, networked digital cameras (“webcams”) can be used to document spatial and temporal variation in the spring and autumn phenology of forest canopies. We use two years of imagery from a deciduous, northern hardwood site, and one year of imagery from a coniferous, boreal transition site. A quantitative signal is obtained by splitting images into separate red, green, and blue color channels and calculating the relative brightness of each channel for “regions of interest” within each image. We put the observed phenological signal in context by relating it to seasonal patterns of gross primary productivity, inferred from eddy covariance measurements of surface–atmosphere CO2 exchange. We show that spring increases, and autumn decreases, in canopy greenness can be detected in both deciduous and coniferous stands. In deciduous stands, an autumn red peak is also observed. The timing and rate of spring development and autumn senescence varies across the canopy, with greater variability in autumn than spring. Interannual variation in phenology can be detected both visually and quantitatively; delayed spring onset in 2007 compared to 2006 is related to a prolonged cold spell from day 85 to day 110. This work lays the foundation for regional- to continental-scale camera-based monitoring of phenology at network observatory sites, e.g., National Ecological Observatory Network (NEON) or AmeriFlux

Numerical wave optics and the lensing of gravitational waves by globular clusters

We consider the possible effects of gravitational lensing by globular clusters on gravitational waves from asymmetric neutron stars in our galaxy. In the lensing of gravitational waves, the long wavelength, compared with the usual case of optical lensing, can lead to the geometrical optics approximation being invalid, in which case a wave optical solution is necessary. In general, wave optical solutions can only be obtained numerically. We describe a computational method that is particularly well suited to numerical wave optics. This method enables us to compare the properties of several lens models for globular clusters without ever calling upon the geometrical optics approximation, though that approximation would sometimes have been valid. Finally, we estimate the probability that lensing by a globular cluster will significantly affect the detection, by ground-based laser interferometer detectors such as LIGO, of gravitational waves from an asymmetric neutron star in our galaxy, finding that the probability is insignificantly small.Comment: To appear in: Proceedings of the Eleventh Marcel Grossmann Meetin

Nitrogen cycling, forest canopy reflectance, and emergent properties of ecosystems

In Ollinger et al. (1), we reported that mass-based concentrations of nitrogen in forest canopies (%N) are positively associated with whole-canopy photosynthetic capacity and canopy shortwave albedo in temperate and boreal forests, the latter result stemming from a positive correlation between %N and canopy near infrared (NIR) reflectance. This finding is intriguing because a functional link between %N and NIR reflectance could indicate an influence of nitrogen cycling on surface energy exchange, and could provide a means for estimating %N using broad-band satellite sensors

Femtolens Imaging of a Quasar Central Engine Using a Dwarf Star Telescope

We show that it is possible to image the structure of a distant quasar on scales of $\sim 1\,$AU by constructing a telescope which uses a nearby dwarf star as its ``primary lens'' together with a satellite-borne ``secondary''. The image produced by the primary is magnified by $\sim 10^5$ in one direction but is contracted by 0.5 in the other, and therefore contains highly degenerate one-dimensional information about the two-dimensional source. We discuss various methods for extracting information about the second dimension including ``femtolens interferometry'' where one measures the interference between different parts of the one-dimensional image with each other. Assuming that the satellite could be dispatched to a position along a star-quasar line of sight at a distance $r$ from the Sun, the nearest available dwarf-star primary is likely to be at \sim 15\,\pc\,(r/40\,\rm AU)^{-2}. The secondary should consist of a one-dimensional array of mirrors extending $\sim 700\,$m to achieve 1 AU resolution, or $\sim 100\,$m to achieve 4 AU resolution.Comment: 12 pages including 3 embedded figure

Quantitative Structure–Selectivity Relationships in Enantioselective Catalysis: Past, Present, and Future

The dawn of the 21st century has brought with it a surge of research related to computer-guided approaches to catalyst design. In the past two decades, chemoinformatics, the application of informatics to solve problems in chemistry, has increasingly influenced prediction of activity and mechanistic investigations of organic reactions. The advent of advanced statistical and machine learning methods, as well as dramatic increases in computational speed and memory, has contributed to this emerging field of study. This review summarizes strategies to employ quantitative structure−selectivity relationships (QSSR) in asymmetric catalytic reactions. The coverage is structured by initially introducing the basic features of these methods. Subsequent topics are discussed according to increasing complexity of molecular representations. As the most applied subfield of QSSR in enantioselective catalysis, the application of local parametrization approaches and linear free energy relationships (LFERs) along with multivariate modeling techniques is described first. This section is followed by a description of global parametrization methods, the first of which is continuous chirality measures (CCM) because it is a single parameter derived from the global structure of a molecule. Chirality codes, global, multivariate descriptors, are then introduced followed by molecular interaction fields (MIFs), a global descriptor class that typically has the highest dimensionality. To highlight the current reach of QSSR in enantioselective transformations, a comprehensive collection of examples is presented. When combined with traditional experimental approaches, chemoinformatics holds great promise to predict new catalyst structures, rationalize mechanistic behavior, and profoundly change the way chemists discover and optimize reactions

The role of surface roughness, albedo, and Bowen ratio on ecosystem energy balance in the Eastern United States

Land cover and land use influence surface climate through differences in biophysical surface properties, including partitioning of sensible and latent heat (e.g., Bowen ratio), surface roughness, and albedo. Clusters of closely spaced eddy covariance towers (e.g., \u3c10 \u3ekm) over a variety of land cover and land use types provide a unique opportunity to study the local effects of land cover and land use on surface temperature. We assess contributions albedo, energy redistribution due to differences in surface roughness and energy redistribution due to differences in the Bowen ratio using two eddy covariance tower clusters and the coupled (land-atmosphere) Variable-Resolution Community Earth System Model. Results suggest that surface roughness is the dominant biophysical factor contributing to differences in surface temperature between forested and deforested lands. Surface temperature of open land is cooler (−4.8 °C to −0.05 °C) than forest at night and warmer (+0.16 °C to +8.2 °C) during the day at northern and southern tower clusters throughout the year, consistent with modeled calculations. At annual timescales, the biophysical contributions of albedo and Bowen ratio have a negligible impact on surface temperature, however the higher albedo of snow-covered open land compared to forest leads to cooler winter surface temperatures over open lands (−0.4 °C to −0.8 °C). In both the models and observation, the difference in mid-day surface temperature calculated from the sum of the individual biophysical factors is greater than the difference in surface temperature calculated from radiative temperature and potential temperature. Differences in measured and modeled air temperature at the blending height, assumptions about independence of biophysical factors, and model biases in surface energy fluxes may contribute to daytime biases

Overview of the South Carolina State and River Basin Planning Framework

Economic development, environmental protection, and public health are critical quality-of-life issues that depend on a reliable supply of water. Increased water demand and climate variability (drought) are two major factors that have the potential to limit future water availability in the state of South Carolina. The development of a comprehensive water-resources management plan for the state is vital for ensuring that an adequate and reliable supply of water will be available to sustain all future uses. The South Carolina Department of Natural Resources (SCDNR) is tasked legislatively with developing water planning and policy initiatives in the state and has initiated a long-term process to update the state water plan, last published in 2004. One of the major recommendations in the 2004 plan was to form River Basin Councils (RBCs) in each of the major river basins in the state for the purpose of water planning. In 2014, SCDNR initiated a multiyear process to develop regional water plans that will serve as the foundation for a new state water plan. A central component of the process was the creation of a Planning Process Advisory Committee (PPAC) for the purpose of developing formal guidelines on the formation of RBCs and the development of river basin plans for the eight designated river basins in the state. The PPAC is composed of a diverse group of stakeholders and includes representation from water utilities, energy utilities, trade organizations, academia, conservation groups, agriculture, and the general public. The work of the PPAC culminated in a report, the South Carolina State Water Planning Framework, which was published in October of 2019. The river basin plans will identify current and future water availability issues and describe a management plan to address these issues to ensure that an adequate and reliable supply of water will be available for future generations. The purpose of this paper is to provide a general overview of the state’s river basin planning process

Mosquitofish, Gambusia affinis (Baird and Girard) Production in Extensive Polyculture System

During 1976, mosquitofish, Gambusia affinis Baird and Girard, were reared in combination with food and game fishes in 0.1 ha culture ponds at the University of Arkansas at Pine Bluff fisheries research facility. Mosquitofish production was 218 kg/ha, with 1683 fish per kilogram, in ponds that were also stocked with channel catfish, Ictalurus punctatus Rafinesque, bigmouth buffalo, Ictiobus cyprinellus Valenciennes, grass carp, Ctenopharyngodon idella Valenciennes, and silver carp, Hypophthalmichthys molitrix Valenciennes. In another similar stocked pond, hybrid sunfish fingerlings depressed mosquitofish yield by 79%. No mosquitofish production was obtained in ponds stocked with 250 largemouth bass, Xficropterus salmoides Lacepede, fry per hectare, although fathead minnows, Pimephales promelas Rafinesque, were added to buffer mosquitofish predation. Total fish yields ranged from 414 to 670 kg/ha for the polyculture systems investigated

A statistical approach to finding overlooked genetic associations

<p>Abstract</p> <p>Background</p> <p>Complexity and noise in expression quantitative trait loci (eQTL) studies make it difficult to distinguish potential regulatory relationships among the many interactions. The predominant method of identifying eQTLs finds associations that are significant at a genome-wide level. The vast number of statistical tests carried out on these data make false negatives very likely. Corrections for multiple testing error render genome-wide eQTL techniques unable to detect modest regulatory effects.</p> <p>We propose an alternative method to identify eQTLs that builds on traditional approaches. In contrast to genome-wide techniques, our method determines the significance of an association between an expression trait and a locus with respect to the set of all associations to the expression trait. The use of this specific information facilitates identification of expression traits that have an expression profile that is characterized by a single exceptional association to a locus.</p> <p>Our approach identifies expression traits that have exceptional associations regardless of the genome-wide significance of those associations. This property facilitates the identification of possible false negatives for genome-wide significance. Further, our approach has the property of prioritizing expression traits that are affected by few strong associations. Expression traits identified by this method may warrant additional study because their expression level may be affected by targeting genes near a single locus.</p> <p>Results</p> <p>We demonstrate our method by identifying eQTL hotspots in <it>Plasmodium falciparum </it>(malaria) and <it>Saccharomyces cerevisiae </it>(yeast). We demonstrate the prioritization of traits with few strong genetic effects through Gene Ontology (GO) analysis of Yeast. Our results are strongly consistent with results gathered using genome-wide methods and identify additional hotspots and eQTLs.</p> <p>Conclusions</p> <p>New eQTLs and hotspots found with this method may represent regions of the genome or biological processes that are controlled through few relatively strong genetic interactions. These points of interest warrant experimental investigation.</p