Is there a link between deep‐sea biodiversity and ecosystem function?     

Daniel Leduc  Ashley A. Rowden  Conrad A. Pilditch  Elizabeth W. Maas  P. Keith Probert 《Marine Ecology》2013,34(3):334-344

Studying the diversity‐ecosystem function relationship in the deep sea is of primary importance in the face of biodiversity loss and for our understanding of how the deep sea functions. Results from the first study of diversity‐ecosystem function relationships in the deep sea (Danovaro et al. 2008; Current Biology, 18, 1–8) are unexpected and show an exponential relationship between deep‐sea nematode diversity and ecosystem function and efficiency, although this relationship appears largely restricted to relatively low diversities [ES(51) <25]. Here, we investigate the relationship between nematode diversity and several independent measures/proxies of ecosystem function (sediment community oxygen consumption, bacterial biomass, bacterial extracellular enzyme activity) and efficiency (ratio of bacterial/nematode carbon to organic C content of the sediment) on the New Zealand continental slope. Nematode diversity at our study sites was relatively high [ES(51) = 30–42], and there was no relationship between species/functional diversity and ecosystem function/efficiency after accounting for the effects of water depth and food availability. Our results are consistent with a breakdown of the exponential diversity‐function relationship at high levels of diversity, which may be due to increased competition or greater functional redundancy. Future studies need to take into account as many environmental factors and as wide a range of diversities as possible to provide further insights into the diversity‐ecosystem function relationship in the largest ecosystem on Earth.  相似文献   

Applicability of Individual Transferable Quotas (ITQs) in Japanese fisheries: A comparison of rights-based fisheries management in Iceland, Japan, and United States   总被引：1，自引：0，他引：1  

Nobuyuki YagiMichael L. Clark  Lee G. AndersonRagnar Arnason  Rebecca Metzner 《Marine Policy》2012,36(1):241-245

ITQs have not yet been introduced by the Government of Japan. In coastal areas, fishery cooperative associations have traditionally played an important role in managing fisheries through self-imposed rules and peer-monitoring systems. Recently, however, the economic competitiveness of Japanese fisheries in the international market is being questioned. In this paper, a detailed examination of the pros and cons of the current system in Japan is compared to the current fishery management measures of Iceland and the United States, where attaining economically or biologically efficient outcomes may be prioritized in making fisheries management decisions. For many coastal fisheries in Japan, maintaining a management scheme in which stakeholders play an active role in determining fisheries measures seems more relevant if their priority is to maintain the stability of coastal communities and equity of stakeholders. Intensive dialog among stakeholders would be necessary to identify shared objectives of their fishery operations and to make decisions to establish specific steps toward the goal of increasing economic efficiency, environmental sustainability, or stability of communities and equity of stakeholders.  相似文献   

Playing Lotto with Rotto? Tourism,the environment and gambling with the ethos of a Western Australian island     

Rebecca Jackson 《The Australian geographer》2008,39(4):495-519

Rottnest Island is a popular holiday destination offshore from Perth, the capital city of Western Australia. Rottnest (or Rotto) attracts approximately 500 000 visitors annually. The island is managed by a statutory government authority, the Rottnest Island Authority (RIA), for the purposes of providing recreation and holiday facilities and services, and protecting its natural and cultural values. While there are advantages in management by one body, there appears to be a conflict in managing both the tourism business and the environment, largely as a result of funding issues. While further tourism development would boost the RIA's self-funded operating budget, increased pressures may compromise the island environment and the Rottnest ethos, which revolves around a relaxed and casual social ambiance. The RIA aims to develop Rottnest as a model for sustainability, but are dilemmas surrounding economic sustainability potentially risking the island's environmental and social sustainability? This paper concludes that in the pursuit of economic returns from tourism, Rottnest Island's environmental and social values face an uncertain future.  相似文献   

Saigon from the diaspora   总被引：1，自引：1，他引：0  

Ashley Carruthers 《Singapore journal of tropical geography》2008,29(1):68-86

In the wake of reform in Vietnam and the end of the cold war, overseas Vietnamese are returning to their former homeland in increasing numbers. For most of the first generation in the diaspora, memories of wartime Saigon are now being augmented by a touristic experience of contemporary Saigon/Ho Chi Minh City. This essay asks how the co-presence of these differently spatialized and temporalized ways of knowing the city affects the production and consumption of images of Saigon in overseas Vietnamese communities in the West. Based on media ethnography carried out in Vietnamese households in Sydney, the paper argues that changes in the way Saigon is represented in overseas Vietnamese popular culture reflect a shift in the larger politics of diasporic identity. While narratives of exile and refugeehood remain potent forms of affective (if not instrumental) politics in overseas Vietnamese contexts, transnational forms of consciousness and identification are beginning to enter into diasporic public culture, albeit in a highly contested way.  相似文献   

Spatiotemporal analysis of residential flood exposure in the Atlanta,Georgia metropolitan area     

Ferguson  Alex P.  Ashley  Walker S. 《Natural Hazards》2017,87(2):989-1016

Natural Hazards - This research examines changes in residential built-environment flood exposure within the current boundaries of the Atlanta, Georgia metropolitan statistical area, by estimating...  相似文献   

The influence of solar‐induced thermal stresses on the mechanical weathering of rocks in humid mid‐latitudes          下载免费PDF全文

Jennifer Aldred  Martha Cary Eppes  Kimberly Aquino  Rebecca Deal  Jacob Garbini  Suraj Swami  Alea Tuttle  George Xanthos 《地球表面变化过程与地形》2016,41(5):603-614

The role of solar‐induced thermal stresses in the mechanical breakdown of rock in humid‐temperate climates has remained relatively unexplored. In contrast, numerous studies have demonstrated that cracks in rocks found in more arid mid‐latitude locations exhibit preferred northeast orientations that are interpreted to be a consequence of insolation‐related cracking. Here we hypothesize that similar insolation‐related mechanisms may be efficacious in humid temperate climates, possibly in conjunction with other mechanical weathering processes. To test this hypothesis, we collected rock and crack data from a total of 310 rocks at a forested field site in North Carolina (99 rocks, 266 cracks) and at forested and unforested field sites in Pennsylvania (211 rocks, 664 cracks) in the eastern United States. We find that overall, measured cracks exhibit statistically preferred strike orientations (47° ± 16), as well as dip angles (52° ± 24°), that are similar in most respects to comparable datasets from mid‐latitude deserts. There is less variance in strike orientations for larger cracks suggesting that cracks with certain orientations are preferentially propagated through time. We propose that diurnally repeating geometries of solar‐related stresses result in propagation of those cracks whose orientations are favorably oriented with respect to those stresses. We hypothesize that the result is an oriented rock heterogeneity that acts as a zone of weakness much like bedding or foliation that can, in turn, be exploited by other weathering processes. Observed crack orientations vary somewhat by location, consistent with this hypothesis given the different latitude and solar exposure of the field sites. Crack densities vary between field sites and are generally higher on north‐facing boulder‐faces and in forested sites, suggesting that moisture‐availability also plays a role in dictating cracking rates. These data provide evidence that solar‐induced thermal stresses facilitate mechanical weathering in environments where other processes are also likely at play. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Undocumented Students’ Narratives of Liminal Citizenship: High Aspirations,Exclusion, and “In-Between” Identities     

Rebecca Maria Torres  Melissa Wicks-Asbun 《The Professional geographer》2013,65(2):195-204

This study illustrates how national immigration policy relegates undocumented immigrant children to spaces of liminal citizenship, which shape their aspirations for higher education. Recognizing the power of migrant narratives, and the importance of privileging youths’ voices through children's geographies, we present the narratives of undocumented high school students from several rural North Carolina communities. Despite various barriers facing undocumented students, most have high academic aspirations. Students construct new forms of citizenship, legitimating their claims to higher education access through their achievement. Their liminal status, however, contributes to the formation of conflicted, “in-between” identities.  相似文献   

The 300‐Well Groundwater Monitoring Program for Southern Los Angeles County Was an NGWA Ground Water Protection Award Winner in 2011     

Rebecca Vandermeulen 《Ground Water Monitoring & Remediation》2013,33(1):37-39

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Kinematic dynamo action in a sphere: Effects of periodic time-dependent flows on solutions with axial dipole symmetry     

Ashley P. Willis  David Gubbins 《地球物理与天体物理流体动力学》2013,107(6):537-554

Choosing a simple class of flows, with characteristics that may be present in the Earth's core, we study the ability to generate a magnetic field when the flow is permitted to oscillate periodically in time. The flow characteristics are parameterised by D, representing a differential rotation, M, a meridional circulation, and C, a component characterising convective rolls. The dynamo action of all solutions with fixed parameters (steady flows) is known from earlier studies. Dynamo action is sensitive to these flow parameters and fails spectacularly for much of the parameter space where magnetic flux is concentrated into small regions, leading to high diffusion. In addition, steady flows generate only steady or regularly reversing oscillatory fields and cannot therefore reproduce irregular geomagnetic-type reversal behaviour. Oscillations of the flow are introduced by varying the flow parameters in time, defining a closed orbit in the space ( D,?M ). When the frequency of the oscillation is small, the net growth rate of the magnetic field over one period approaches the average of the growth rates for steady flows along the orbit. At increased frequency time-dependence appears to smooth out flux concentrations, often enhancing dynamo action. Dynamo action can be impaired, however, when flux concentrations of opposite signs occur close together as smoothing destroys the flux by cancellation. It is possible to produce geomagnetic-type reversals by making the orbit stray into a region where the steady flows generate oscillatory fields. In this case, however, dynamo action was not found to be enhanced by the time-dependence. A novel approach is being taken to solve the time-dependent eigenvalue problem where, by combining Floquet theory with a matrix-free Krylov-subspace method, we can avoid large memory requirements for storing the matrix required by the standard approach.  相似文献   

Lakes and Community: The Importance of Natural Landscapes in Social Research     

Richelle Winkler  Rebecca L. Schewe  David Matarrita-Cascante 《社会与自然资源》2013,26(2):158-175

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