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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 1,207 records · Page 67
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Mycorrhiza Better Predict Soil Fungal Community Composition and Function than Aboveground Traits in Temperate Forest Ecosystems

Forests in the northeastern US are experiencing shifts in community composition due to the northward migration of warm-adapted tree species and certain species’ declines (for example, white ash and eastern hemlock) due to invasive insects. Changes in belowground fungal communities and associated functions will inevitably follow. Therefore, we sought to investigate the relative importance of two important tree characteristics—mycorrhizal type [ectomycorrhizal (EcM) or arbuscular mycorrhizal (AM)] and leaf habit (deciduous or evergreen) on soil fungal community composition and organic matter cycling. We sampled soil in the organic and mineral horizons beneath two AM-associated (Fraxinus americana and Thuja occidentalis) and two ECM-associated tree species (Betula alleghaniensis and Tsuga canadensis), with an evergreen and deciduous species in each mycorrhizal group. To characterize fungal communities and organic matter decomposition beneath each tree species, we sequenced the ITS1 region of fungal DNA and measured the potential activity of carbon- and nitrogen-targeting extracellular enzymes. Each tree species harbored distinct fungal communities, supporting the need to consider both mycorrhizal type and leaf habit. However, between tree characteristics, mycorrhizal type better predicted fungal communities. Across fungal guilds, saprotrophic fungi were the most important group in shaping fungal community differences in soils beneath all tree species. The effect of leaf habit on carbon- and nitrogen-targeting hydrolytic enzymes depended on tree mycorrhizal association in the organic horizon, while oxidative enzyme activities were higher beneath EcM-associated trees across both soil horizons and leaf habits.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2010

Negotiating river ecosystems: Impact assessment and conflict mediation in the cases of hydro-power construction

In this paper we discuss how the legitimacy of the impact assessment process is a key issue in conflict mediation in environmental impact assessment. We contrast two EIA cases in hydro-power generation plans made for the Ii River, Finland in different decades, and evaluate how impact assessment in these cases has contributed to the creation, mediation and resolution of conflicts. We focus on the elements of distributional and procedural justice that made the former EIA process more legitimate and consensual and the latter more conflictual. The results indicate that it is crucial for conflict mediation to include all the values and interests of the parties in the goal-setting process and in the definition and assessment of alternatives. The analysis also indicates that procedural justice is the most important to help the people and groups involved to accept the legitimacy of the impact assessment process: how different parties and their values and interests are recognized, and how participation and distribution of power are organized in an impact assessment process. It is confirmed in this article that SIA may act as a mediator or a forum providing a process through which competing knowledge claims, various values and interests can be discussed and linked to the proposed alternatives and interventions.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2016

The effectiveness of the mitigation hierarchy in environmental impact studies on marine ecosystems: A case study in France

While the development of maritime economic activity is increasingly encouraged, the consideration of its impacts constitutes a real challenge. The limitations of the implementation of the mitigation hierarchy have been widely discussed in scientific literature, yet data on marine biodiversity offset practices remains scarce. In this study, we investigated the use of Environmental Impact Assessments (EIAs) as suitable instruments to achieve the No Net Loss objective. Drawing on a French approach developed for the initial assessment of the European Marine Strategy Framework Directive, we examined the pressures and impacts related to various marine development projects and the effectiveness of the mitigation hierarchy in limiting these. An analysis of 55 recent French environmental impact studies showed that only 7% of the proposed measures had the aim of offsetting predicted degradation of sites of remarkable biodiversity. This can be partly explained by the lack of a clear definition of ‘significant impact’, which varies greatly depending on what is impacted, in turn allowing socio-economic activities to benefit more easily from offset. Furthermore, offsetting does not always constitute the final step of the mitigation hierarchy, highlighting the need to reinforce avoidance and reduction steps. Although we acknowledge the role of EIA in mitigating the negative impacts of development projects, synergies with other European marine environmental policies such as the Marine Strategy Framework Directive (MSFD) and the Maritime Spatial Planning directive (MSP) should be developed in order to improve current practices. - Highlights: • Avoidance measures were not well represented in the Environmental Impact Assessments studied. • Few significant residual impacts and measures to offset these were described. • Common biodiversity did not benefit from offset measures. • The equivalency of proposed marine offsets is questionable.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2012

Polychlorinated biphenyls in coastal tropical ecosystems: Distribution, fate and risk assessment

Polychlorinated biphenyls (PCBs) though banned still find use in most developing countries including Ghana. PCB congener residues in sediments in the coastal regions of Ghana were determined. Sediment samples (n=80) were collected between June 2008 and March 2009, extracted by the continuous soxhlet extraction using (1:1) hexane-acetone mixture for 24 h and analyzed with a CP 3800 gas chromatogram equipped with {sup 65}Ni electron capture detector (GC-ECD) and a mixed PCBs standard of the ICES 7 as marker, after clean-up. Validation of the efficiency and precision of the extraction and analytical methods were done by extracting samples spiked with 2 ppm ICES PCB standard and a certified reference material 1941b for marine sediments from NIST, USA, and analyzed alongside the samples. Total PCBs detected in sediments during the dry and wet seasons were, respectively, 127 and 112 {mu}g/kg dry weight (dw), with a mean concentration of 120 {mu}g/kg (dw). The composition of PCB homologues in the sediments were dominated by tri-, penta- and tetra-PCBs. There was no correlation between organic carbon (OC) of the sediments and total PCBs content. Risk assessments conducted on the levels indicated that PCB levels in sediments along the coastal region of Ghana poses no significant health risk to humans.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2012

Enhancing terrestrial ecosystem sciences by integrating empirical-modeling approaches

Field and laboratory experiments and observations, along with models, are foundational approaches to scientific inquiry. Integration of these approaches, however, can be an exceedingly difficult challenge because empiricists and modelers often work in communities separated by cultural differences and communication barriers, reflecting a largely independent evolution of these disciplines. To address this challenge, more than 40 participants gathered for a 3-day workshop to discuss how models can best inform empirical experiments, how data can most effectively inform models, and what strategies can be employed to integrate these two approaches. The workshop was convened with the understanding that such a priori exchange between the empirical and modeling communities can maximize intellectual investments and result in high-quality predictive models and more scientific discovery.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2014

Microbial dormancy improves development and experimental validation of ecosystem model

Climate feedbacks from soils can result from environmental change followed by response of plant and microbial communities, and/or associated changes in nutrient cycling. Explicit consideration of microbial life history traits and functions may be necessary to predict climate feedbacks due to changes in the physiology and community composition of microbes and their associated effect on carbon cycling. Here, we enhanced the Microbial-Enzyme-mediated Decomposition (MEND) model by incorporating microbial dormancy and the ability to track multiple isotopes of carbon. We tested two versions of MEND, i.e., MEND with dormancy and MEND without dormancy, against long-term (270 d) lab incubations of four soils with isotopically-labeled substrates. MEND without dormancy adequately fitted multiple observations (total and 14C respiration, and dissolved organic carbon), but at the cost of significantly underestimating the total microbial biomass. The MEND with dormancy improved estimates of microbial biomass by 20 71% over the MEND without dormancy. We observed large differences for two fitted model parameters, the specific maintenance and growth rates for active microbes, depending on whether dormancy was considered. Together our model extrapolations of the incubation study show that long-term soil incubations with observations in multiple carbon pools are necessary to estimate both decomposition and microbial parameters. These efforts should provide essential support to future field- and global-scale simulations and enable more confident predictions of feedbacks between environmental change and carbon cycling.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2014

Sensitive response of a model of symbiotic ecosystem to seasonal periodic drive

A symbiotic ecosysytem (metapopulation) is studied by means of the stochastic Lotka-Volterra model with generalized Verhulst self-regulation. The effect of variable environment on the carrying capacities of populations is taken into account as an asymmetric dichotomous noise and as a deterministic periodic stimulus. In the framework of the mean-field theory an explicit self-consistency equation for the system in the long-time limit is presented. Also, expressions for the probability distribution and for the moments of the population size are found. In certain cases the mean population size exhibits large oscillations in time, even if the amplitude of the seasonal environmental drive is small. Particularly, it is shown that the occurrence of large oscillations of the mean population size can be controlled by noise parameters (such as amplitude and correlation time) and by the coupling strength of the symbiotic interaction between species.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗