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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

The sensitivity of breeding songbirds to changes in seasonal timing is linked to population change but cannot be directly attributed to the effects of trophic asynchrony on productivity

Abstract A consequence of climate change has been an advance in the timing of seasonal events. Differences in the rate of advance between trophic levels may result in predators becoming mismatched with prey availability, reducing fitness and potentially driving population declines. Such “trophic asynchrony” is hypothesized to have contributed to recent population declines of long‐distance migratory birds in particular. Using spatially extensive survey data from 1983 to 2010 to estimate variation in spring phenology from 280 plant and insect species and the egg‐laying phenology of 21 British songbird species, we explored the effects of trophic asynchrony on avian population trends and potential underlying demographic mechanisms. Species which advanced their laying dates least over the last three decades, and were therefore at greatest risk of asynchrony, exhibited the most negative population trends. We expressed asynchrony as the annual variation in bird phenology relative to spring phenology, and related asynchrony to annual avian productivity. In warmer springs, birds were more asynchronous, but productivity was only marginally reduced; long‐distance migrants, short‐distance migrants and resident bird species all exhibited effects of similar magnitude. Long‐term population, but not productivity, declines were greatest among those species whose annual productivity was most greatly reduced by asynchrony. This suggests that population change is not mechanistically driven by the negative effects of asynchrony on productivity. The apparent effects of asynchrony on population trends are therefore either more likely to be strongly expressed via other demographic pathways, or alternatively, are a surrogate for species' sensitivity to other environmental pressures which are the ultimate cause of decline.

Franks, Samantha E.↗
DOE OSTI2016

Integrating copper toxicity and climate change to understand extinction risk to two species of pond‐breeding anurans

Abstract Chemical contamination is often suggested as an important contributing factor to amphibian population declines, but direct links are rarely reported. Population modeling provides a quantitative method to integrate toxicity data with demographic data to understand the long‐term effects of contaminants on population persistence. In this study we use laboratory‐derived embryo and larval toxicity data for two anuran species to investigate the potential for toxicity to contribute to population declines. We use the southern toad ( Anaxyrus terrestris ) and the southern leopard frog ( Lithobates sphenocephalus ) as model species to investigate copper (Cu) toxicity. We use matrix models to project populations through time and quantify extinction risk (the probability of quasi‐extinction in 35 yr). Life‐history parameters for toads and frogs were obtained from previously published literature or unpublished data from a long‐term (>35 yr) data set. In addition to Cu toxicity, we investigate the role of climate change on amphibian populations by including the probability of early pond drying that results in catastrophic reproductive failure ( CRF , i.e., complete mortality of all larval individuals). Our models indicate that CRF is an important parameter for both species as both were unable to persist when CRF probability was >50% for toads or 40% for frogs. Copper toxicity alone did not result in significant effects on extinction risk unless toxicity was very high (>50% reduction in survival parameters). For toads, Cu toxicity and high probability of CRF both resulted in high extinction risk but no synergistic (or greater than additive) effects between the two stressors occurred. For leopard frogs, in the absence of CRF survival was high even under Cu toxicity, but with CRF Cu toxicity increased extinction risk. Our analyses highlight the importance of considering multiple stressors as well as species differences in response to those stressors. Our models were consistently most sensitive to juvenile and adult survival, further suggesting the importance of terrestrial stages to population persistence. Future models will incorporate multiple wetlands with different combinations of stressors to understand if our results for a single wetland result in a population sink within the landscape.

Weir, Scott M.↗
DOE OSTI2015

Technical Comparative Analysis of "Best of Breed" Turnkey Si-Based Processes and Equipment, to be Used to Produce a Combined Multi-entity Research and Development Technology Roadmap for Thick and Thin Silicon PV

A side-by-side analysis was done on then currently available technology, along with roadmaps to push each particular option forward. Variations in turnkey line processes can and do result in finished solar device performance. Together with variations in starting material quality, the result is a distribution of efficiencies. Forensic analysis and characterization of each crystalline Si based technology will determine the most promising approach with respect to cost, efficiency and reliability. Forensic analysis will also shed light on the causes of binning variations. Si solar cells were forensically analyzed from each turn key supplier using a host of techniques

14 SOLAR ENERGY↗
DOE OSTI2019

A Novel Poplar Biomass Germplasm Resource for Functional Genomics and Breeding

Interspecific hybridization is the most effective method for producing poplar clones for commercial applications, including biomass production. Previous research has shown that commercial F1 hybrids frequently exhibit dosage variation, i.e. variation in the number of pieces or entire chromosomes, and that these variants can have novel or more extreme phenotypes compared to their parents, that can be desirable for biomass production. Poplar is a convenient system for studying and exploiting gene dosage because germplasm can very easily be propagated vegetatively, via cuttings, for research and production, and advanced genome-enabled tools can be directly employed on the actual feedstock. In the previous funding cycle, we had produced and characterized a population of interspecific hybrids carrying insertions and deletions, which together, tile the entire genome with dosage variation. In this funding cycle, we completed the development of this unique resource for the research community and started using the germplasm to investigate the role of gene dosage in poplar hybrid performance, and to identify chromosomal regions and genes that contribute to poplar bioenergy traits. Our specific goals were to: i) maintain and finish the characterization of this resource ii) investigate the phenotypic effects of dosage change iii) exploit the indel germplasm for functional genomics.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2020

A novel poplar biomass germplasm resource for functional genomics and breeding. Final report addendum

In this report, we report and update activities associated with co-PI Groover. This report is an addendum to the full report detailing genomic objectives associated with the project, submitted by PI Luca Comai and co-PI Isabelle Henry. The Groover lab is leading the efforts to produce and replicate poplar irradiation and control hybrids genotypes, and phenotype the hybrids. These efforts are coordinated with Comai and Henry to ensure the most promising hybrids are included for field and greenhouse-based studies, and to link the genomic and phenotypic analyses.

09 BIOMASS FUELS↗