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Alida Bundy Johanna J. Heymans Lyne Morissette Claude Savenkoff 《Progress in Oceanography》2009,81(1-4):188
The facts: four Northwest Atlantic ecosystems, three cod stock collapses 15 years ago (plus one severely depleted), seals now top predator in all ecosystems, all had cod as a top predator before collapse, groundfish declines in all areas, forage base increased in most systems. No recovery in any system. Have these ecosystems fundamentally changed? Why? The challenge: compare and contrast these four ecosystems. The answer: using mass balance models, empirical data and a suite of ecosystem indicators, we explore how and why these systems have changed over time. At the ecosystem and community level, we see broad similarities between ecosystems. However, structurally and functionally these systems have shifted to an alternate state, with changes in predator structure, trophic structure and flow. 相似文献
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Thiombiano Alida N El Adlouni Salaheddine St-Hilaire André Ouarda Taha B.M.J El-Jabi Nassir 《Theoretical and Applied Climatology》2017,129(1-2):413-426
Theoretical and Applied Climatology - In this paper, a statistical inference of Southeastern Canada extreme daily precipitation amounts is proposed using a classical nonstationary... 相似文献
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Governors always have some image of what they are governing and why, and of what their role is. These images are often implicit. They are not reflected upon or discussed in the governance process, yet they have real consequences because they are acted upon. Interactive governance theory argues that image formation is an integral part of governance and that images are made as explicit as possible to avoid self-fulfilment. Such a process needs to be interactive and flexible to allow exploration of alternatives to existing governing images for the purpose of enhancing the governability of fisheries systems. In this paper, we contrast the classical image of the governing system (top down decision-making pyramid) and of the human-in-nature system (top down trophic pyramid) with alternative images (roses and inverted pyramid, respectively) and discuss the implication that these different images have on fisheries governance. 相似文献
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Anca Avram Daniela Constantin Daniel Veres Szabolcs Kelemen Igor Obreht Ulrich Hambach Slobodan B. Marković Alida Timar-Gabor 《Boreas: An International Journal of Quaternary Research》2020,49(3):615-633
The loess–palaeosol sequence of Batajnica (Vojvodina region, Serbia) is considered as one of the most complete and thickest terrestrial palaeoclimate archives for the Middle and Late Pleistocene. In order to achieve a numerical chronology for this profile, four sets of ages were obtained on 18 individual samples. Equivalent doses were determined using the SAR protocol on fine (4–11 μm) and coarse (63–90 μm) quartz fractions, as well as on polymineral fine grains by using two elevated temperature infrared stimulation methods, pIRIR290 and pIRIR225. We show that the upper age limit of coarse quartz OSL and polymineral pIRIR290 and pIRIR225 techniques is restricted to the Last Glacial/Interglacial cycle due to the field saturation of the natural signals. Luminescence ages on coarse quartz, pIRIR225 and pIRIR290 polymineral fine grains are in general agreement. Fine quartz ages are systematically lower than the coarse quartz and pIRIR ages, the degree of underestimation increasing with age. Comparison between natural and laboratory dose response curves indicate the age range over which each protocol provides reliable ages. For fine and coarse quartz, the natural and laboratory dose response curves overlap up to ~150 and ~250 Gy, respectively, suggesting that the SAR protocol provides reliable ages up to c. 50 ka on fine quartz and c. 100 ka on coarse quartz. Using the pIRIR225 and pIRIR290 protocols, equivalent doses up to ~400 Gy can be determined, beyond which in the case of the former the natural dose response curve slightly overestimates the laboratory dose response curve. Our results suggest that the choice of the mineral and luminescence technique to be used for dating loess sediments should take into consideration the reported limited reliability. 相似文献
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