The robustness and restoration of a network of ecological networks

Understanding species' interactions and the robustness of interaction networks to species loss is essential to understand the effects of species' declines and extinctions. In most studies, different types of networks (such as food webs, parasitoid webs, seed dispersal networks, and pollination networks) have been studied separately. We sampled such multiple networks simultaneously in an agroecosystem. We show that the networks varied in their robustness; networks including pollinators appeared to be particularly fragile. We show that, overall, networks did not strongly covary in their robustness, which suggests that ecological restoration (for example, through agri-environment schemes) benefitting one functional group will not inevitably benefit others. Some individual plant species were disproportionately well linked to many other species. This type of information can be used in restoration management, because it identifies the plant taxa that can potentially lead to disproportionate gains in biodiversity

Occupations of State Farmers in Utah

The Future Farmer of America organization had its birth in Utah in 1929. It is a national organization of farm boys, registered in Vocational Agriculture in high school. There are four grades of membership based upon achievement. These are (1) Green Hand, (2) Chapter Farmer, (3) State Farmer, and (4) American Farme

Thermal-hydraulic analysis of innovative fuel configurations for the sodium fast reactor

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2009.Cataloged from PDF version of thesis.Includes bibliographical references (p. 419-429).The sodium fast reactor (SFR) is currently being reconsidered as an instrument for actinide management throughout the world, thanks in part to international programs such as the Generation-IV and especially the Global Nuclear Energy Partnership (GNEP). The success of these programs, in particular the GNEP, is dependent upon the ability of the SFR to manage actinide inventory while remaining economically competitive. In order to achieve these goals, the fuel must be able to operate reliably at high power densities. However, the power density of the fuel is limited by fuel-clad chemical interaction (FCCI) for metallic fuel, cladding thermal and irradiation strain, the fuel melting point, sodium boiling, and to a lesser extent the sodium pressure drop in the fuel channels. Therefore, innovative fuel configurations that reduce clad stresses, sodium pressure drops, and fuel/clad temperatures could be applied to the SFR core to directly improve the performance and economics. Two particular designs of interest that could potentially improve the performance of the SFR core are the internally and externally cooled annular fuel and the bottle-shaped fuel. In order to evaluate the thermal-hydraulic performance of these fuels, the capabilities of the RELAP5-3D code have been expanded to perform subchannel analysis in sodium-cooled fuel assemblies with non-conventional geometries. This expansion was enabled by the use of control variables in the code. When compared to the SUPERENERGY II code, the prediction of core outlet temperature agreed within 2%. In addition, the RELAP5-3D subchannel model was applied to the ORNL 19-pin test, and it was found that the code could predict the measured outlet temperature distribution with a maximum error of -8%.(cont.) As an application of this subchannel model, duct ribs were explored as a means of reducing core outlet temperature peaking within the fuel assemblies. The performance of the annular and bottle-shaped fuel was also investigated using this subchannel model. The annular fuel configurations are best suited for low conversion ratio cores. The magnitude of the power uprate enabled by metal annular fuel in the CR = 0.25 cores is 20%, and is limited by the FCCI constraint during a hypothetical flow blockage of the inner-annular channel due to the small diameters of the inner-annular flow channel (3.6 mm). On the other hand, a complete blockage of the hottest inner-annular flow channel in the oxide fuel case results in sodium boiling, which renders the annular oxide fuel concept unacceptable for use in a SFR. The bottle-shaped fuel configurations are best suited for high conversion ratio cores. In the CR = 0.71 cores, the bottle-shaped fuel configuration reduces the overall core pressure drop in the fuel channels by up to 36.3%. The corresponding increase in core height with bottle-shaped fuel is between 15.6% and 18.3%. A full-plant RELAP5-3D model was created to evaluate the transient performance of the base and innovative fuel configurations during station blackout and UTOP transients. The transient analysis confirmed the good thermal-hydraulic performance of the annular and bottle-shaped fuel designs with respect to their respective solid fuel pin cases.by Matthew J Memmott.Ph.D

High Resilience of Seed Dispersal Webs Highlighted by the Experimental Removal of the Dominant Disperser

The pressing need to conserve and restore habitats in the face of ongoing species loss [1, 2] requires a better understanding of what happens to communities when species are lost or reinstated [3, 4]. Theoretical models show that communities are relatively insensitive to species loss [5, 6]; however, they disagree with field manipulations showing a cascade of extinctions [7, 8] and have seldom been tested under field conditions (e.g., [9]). We experimentally removed the most abundant seed-dispersing ant species from seed dispersal networks in a Mediterranean landscape, replicating the experiment in three types of habitat, and then compared these communities to un-manipulated control communities. Removal did not result in large-scale changes in network structure. It revealed extensive structural plasticity of the remaining community, which rearranged itself through rewiring, while maintaining its functionality. The remaining ant species widened their diet breadth in a way that maintained seed dispersal, despite the identity of many interactions changing. The species interaction strength decreased; thus, the importance of each ant species for seed dispersal became more homogeneous, thereby reducing the dependence of seed species on one dominant ant species. Compared to the experimental results, a simulation model that included rewiring considerably overestimated the effect of species loss on network robustness. If community-level species loss models are to be of practical use in ecology or conservation, they need to include behavioral and population responses, and they need to be routinely tested under field conditions; doing this would be to the advantage of both empiricists and theoreticians

Modest enhancements to conventional grassland diversity improve the provision of pollination services

Grassland for livestock production is a major form of land use throughout Europe and its intensive management threatens biodiversity and ecosystem functioning in agricultural landscapes. Modest increases to conventional grassland biodiversity could have considerable positive impacts on the provision of ecosystem services, such as pollination, to surrounding habitats. Using a field-scale experiment in which grassland seed mixes and sward management were manipulated, complemented by surveys on working farms and phytometer experiments, the impact of conventional grassland diversity and management on the functional diversity and ecosystem service provision of pollinator communities were investigated. Increasing plant richness, by the addition of both legumes and forbs, was associated with significant enhancements in the functional diversity of grassland pollinator communities. This was associated with increased temporal stability of flower–visitor interactions at the community level. Visitation networks revealed pasture species Taraxacum sp. (Wigg.) (dandelion) and Cirsium arvense (Scop.) (creeping thistle) to have the highest pollinator visitation frequency and richness. Cichorium intybus (L.) (chichory) was highlighted as an important species having both high pollinator visitation and desirable agronomic properties. Increased sward richness was associated with an increase in the pollination of two phytometer species; Fragaria × ananassa (strawberry) and Silene dioica (red campion), but not Vicia faba (broad bean). Enhanced functional diversity, richness and abundance of the pollinator communities associated with more diverse neighbouring pastures were found to be potential mechanisms for improved pollination. Synthesis and applications. A modest increase in conventional grassland plant diversity with legumes and forbs, achievable with the expertise and resources available to most grassland farmers, could enhance pollinator functional diversity, richness and abundance. Moreover, our results suggest that this could improve pollination services and consequently surrounding crop yields (e.g. strawberry) and wildflower reproduction in agro-ecosystems

Design concepts and processes for public Aboriginal architecture

The authors wrote this paper in an attempt to document and describe how to address the design challenge of a public building which captures and distils Indigenous cultural assumptions, perspectives, connections, and cultural content. Although there is a body of knowledge about Aboriginal vernacular design and meaning, and about related architectural design issues, there is not a good sense of how relevant this collective wisdom is in the context of a public or monumental building. There are also many pitfalls in prescribing something in a domain which is largely uncharted - or indeed of prescribing anything to architects, or on behalf of Aboriginal communities. Questions that are addressed in this paper include:- What might an interested architect want to know about Aboriginal cultures? What are some possible thematic elements and complexes that might lend themselves to architectural form, function and meaning? What are some good and bad examples of previous attempts to design and incorporate Indigenous culture into public buildings? What Aboriginal design issues are most relevant to the design of public architecture

Remote Indigenous housing procurement: a comparative study

This project sought to understand how housing procurement strategies impact on outcomes for Indigenous people in remote settlements. It examined four cases studies where governments have intervened in housing procurement processes and what makes for success in achieving improvements in social, cultural and economic outcomes.James Davidson, Paul Memmott, Carroll Go-Sam and Elizabeth Gran

Rates of species introduction to a remote oceanic island

The introduction of species to areas beyond the limits of their natural distributions has a major homogenizing influence, making previously distinct biotas more similar. The scale of introductions has frequently been commented on, but their rate and spatial pervasiveness have been less well quantified. Here, we report the findings of a detailed study of pterygote insect introductions to Gough Island, one of the most remote and supposedly pristine temperate oceanic islands, and estimate the rate at which introduced species have successfully established. Out of 99 species recorded from Gough Island, 71 are established introductions, the highest proportion documented for any Southern Ocean island. Estimating a total of approximately 233 landings on Gough Island since first human landfall, this equates to one successful establishment for every three to four landings. Generalizations drawn from other areas suggest that this may be only one-tenth of the number of pterygote species that have arrived at the island, implying that most landings may lead to the arrival of at least one alien. These rates of introduction of new species are estimated to be two to three orders of magnitude greater than background levels for Gough Island, an increase comparable to that estimated for global species extinctions (many of which occur on islands) as a consequence of human activities

Method for the Destruction of Endotoxin in Synthetic Spider Silk Proteins

Although synthetic spider silk has impressive potential as a biomaterial, endotoxin contamination of the spider silk proteins is a concern, regardless of the production method. The purpose of this research was to establish a standardized method to either remove or destroy the endotoxins present in synthetic spider silk proteins, such that the endotoxin level was consistently equal to or less than 0.25 EU/mL, the FDA limit for similar implant materials. Although dry heat is generally the preferred method for endotoxin destruction, heating the silk proteins to the necessary temperatures led to compromised mechanical properties in the resultant materials. In light of this, other endotoxin destruction methods were investigated, including caustic rinses and autoclaving. It was found that autoclaving synthetic spider silk protein dopes three times in a row consistently decreased the endotoxin level 10–20 fold, achieving levels at or below the desired level of 0.25 EU/mL. Products made from triple autoclaved silk dopes maintained mechanical properties comparable to products from untreated dopes while still maintaining low endotoxin levels. Triple autoclaving is an effective and scalable method for preparing synthetic spider silk proteins with endotoxin levels sufficiently low for use as biomaterials without compromising the mechanical properties of the materials

Building new houses in remote Indigenous communities

This Research and Policy Bulletin provides details of the key findings and policy implications from the completed AHURI research project Remote Indigenous housing procurement and post-occupancy outcomes - a comparative study.James Davidson, Carroll Go-Sam, Paul Memmott and Elizabeth Gran