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The Vallcebre research catchments are located in the south-eastern Pyrenees, in an area of diverse land use and varying levels of degradation, including forested hillslopes, abandoned agricultural terraces and badland areas. Outside the badlands, the hydrological response is controlled by saturation mechanisms. Between September and June the spatial patterns of saturated areas and soil moisture are determined by subsurface flow, modified by the premature saturation of the inner parts of agricultural terraces, and the negative soil moisture anomalies induced by forest patches overgrown in grassland areas. During summer, this behaviour ceases because of soil moisture depletion and badland surfaces are the only hydrologically active areas, producing excess runoff in response to the intense rainstorms. During the beginning and the ending of the wet season, the saturation of active areas shows a hysteretic behaviour that breaks the linearity between the mean water reserve of the basin and the relative saturated area. © 1997 John Wiley & Sons, Ltd. 相似文献
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用碳纤维布改善钢筋混凝土极短柱抗震性能的试验研究 总被引:12,自引:0,他引:12
本文进行了5根钢筋混凝土极短柱(λ=1.0)在周期反复荷载作用下的试验,研究了使用碳纤维布横向包裹钢筋混凝土极短柱以提高其延性这种加固方法的有效性。本文研究了碳纤维布横向包裹钢筋混凝土极短柱的受力特性,分析了碳纤维布抗拉强度对试件抗震性能的影响,并对碳纤维布加固钢筋混凝土极短柱使其延性提高的机理进行了探讨。试验结果表明,横向包裹碳纤维布可显著提高钢筋混凝土极短柱的变形性能。 相似文献
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TB Robinson ME Alexander CA Simon CL Griffiths K Peters S Sibanda 《African Journal of Marine Science》2016,38(1):129-140
Confusion between terms and ambiguities among definitions have long plagued the field of invasion biology. One result is disruption in flow of information from researchers to policy-makers and managers who rely on science to inform regulatory frameworks and management actions. We reviewed the South African marine biology literature to quantify the current usage of terminology describing marine invasions and found a variety of terms in use, few of which are defined when used. In response, we propose standard terminology that aligns with international practice. We then interpreted the Blackburn unified framework for biological invasions within the marine context and used this as a transparent way to apply the standardised terms to an updated list of marine alien species for the country. This resulted in the recognition of 36 alien and 53 invasive species within South Africa. Most notably, follow-up research is required to confirm the status of at least 11 listed species, the majority of which have been recorded only once, or not in the past 25 years. It is hoped that by standardising terminology, marine science in South Africa will better support authorities charged with managing the threat posed by marine alien species. 相似文献
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Conservation surrogates, such as umbrella and flagship species, could help focus South Africa’s limited resources for research and management and enhance the conservation gains from marine protected areas (MPAs). Sharks, rays and chimaeras (Chondrichthyes), which are charismatic and ecologically diverse, are potential umbrella candidates, but tests of the ecological suitability of putative marine umbrella species are lacking. Using baited remote underwater video in and around two MPAs in the Western Cape Province, we assessed the potential of chondrichthyans as an umbrella species-complex by quantifying the relationships and co-occurrence patterns between chondrichthyan abundance and diversity and those of other taxa (primarily teleosts and crustaceans). Sites with abundant chondrichthyans, with catsharks or large sharks (>1 m total length), all had significantly greater abundance and diversity of these other taxa, and associations with species of commercial and conservation interest (e.g. roman Chrysoblephus laticeps). Endemic scyliorhinids (notably dark catshark Haploblepharus pictus) and the broadnose sevengill shark Notorynchus cepedianus also had many strong positive co-occurrences (28% and 21% of interactions, respectively). The puffadder catshark H. edwardsii had the highest centrality of any species, denoting its high connectedness to other taxa. Overall, chondrichthyans, especially the dark and puffadder catsharks and the broadnose sevengill shark, show strong potential as an umbrella species-complex in South Africa. 相似文献