Estes J.A.,University of California at Santa Cruz |
Terborgh J.,Duke University |
Brashares J.S.,University of California at Berkeley |
Power M.E.,University of California at Berkeley |
And 23 more authors.
Science | Year: 2011
Until recently, large apex consumers were ubiquitous across the globe and had been for millions of years. The loss of these animals may be humankind's most pervasive influence on nature. Although such losses are widely viewed as an ethical and aesthetic problem, recent research reveals extensive cascading effects of their disappearance in marine, terrestrial, and freshwater ecosystems worldwide. This empirical work supports long-standing theory about the role of top-down forcing in ecosystems but also highlights the unanticipated impacts of trophic cascades on processes as diverse as the dynamics of disease, wildfire, carbon sequestration, invasive species, and biogeochemical cycles. These findings emphasize the urgent need for interdisciplinary research to forecast the effects of trophic downgrading on process, function, and resilience in global ecosystems.
Lyly M.,University of Turku |
Klemola T.,University of Turku |
Koivisto E.,University of Turku |
Huitu O.,Finnish Forest Research Institute |
And 3 more authors.
Oecologia | Year: 2014
The negative impacts of mammalian herbivores on plants have been studied quite extensively, but typically with only a single herbivore species at a time. We conducted a novel comparison of the browsing effects of voles, hares and cervids upon the growth and survival of boreal tree seedlings. This was done by excluding varying assemblages of these key mammalian herbivores from silver birch, Scots pine and Norway spruce seedlings for 3 years. We hypothesised that the pooled impacts of the herbivores would be greater than that of any individual group, while the cervids would be the group with the strongest impact. Growth of birch seedlings advanced when cervids were excluded whereas growth of seedlings accessible to cervids was hindered. Survival of all seedlings was lowest when they were accessible to voles and voles plus hares, whereas cervids seemed not to influence seedling survival. Our results show that the impact of herbivores upon woody plants can be potent in the boreal forests, but the mechanism and strength of this link depends on the tree and herbivore species in question. Risk of abated stand regeneration appears highest for the deciduous birch, though there is need for seedling protection also in coniferous stands. The clear cervid-mediated growth limitation of birch also indicates potential for a trophic cascade effect by mammalian top predators, currently returning to boreal ecosystems. © 2013 Springer-Verlag Berlin Heidelberg.
Virtanen R.,University of Oulu |
Grytnes J.-A.,University of Bergen |
Lenoir J.,University of Picardie Jules Verne |
Lenoir J.,University of Aarhus |
And 5 more authors.
Ecography | Year: 2013
Productivity has long been argued to be a major driver of species richness patterns. In the present study we test alternative productivity-diversity hypotheses using vegetation data from the vast Eurasian tundra. The productivity-species pool hypothesis predicts positive relationships at both fine and coarse grain sizes, whereas the productivity-interaction hypothesis predicts unimodal patterns at fine grain size, and monotonic positive patterns at coarse grain size. We furthermore expect to find flatter positive (productivity-species pool hypothesis) or more strongly negative (productivity-interaction hypothesis) relationships for lichens and bryophytes than for vascular plants, because as a group, lichens and bryophytes are better adapted to extreme arctic conditions and more vulnerable to competition for light than the taller-growing vascular plants. The normalised difference vegetation index (NDVI) was used as a proxy of productivity. The generally unimodal productivity-diversity patterns were most consistent with the productivity-interaction hypothesis. There was a general trend of decreasing species richness from moderately to maximally productive tundra, in agreement with an increasing importance of competitive interactions. High richness of vascular plants and lichens occurred in moderately low productive tundra areas, whereas that of bryophytes occurred in the least productive tundra habitats covered by this study. The fine and coarse grain richness trends were surprisingly uniform and no variation in beta diversity along the productivity gradient was seen for vascular plants or bryophytes. However, lichen beta diversity varied along the productivity gradient, probably reflecting their sensitivity to habitat conditions and biotic interactions. Overall, the results show evidence that productivity-diversity gradients exist in tundra and that these appear to be largely driven by competitive interactions. Our results also imply that climate warming-driven increases in productivity will strongly affect arctic plant diversity patterns. © 2012 The Authors.
Lenoir J.,University of Aarhus |
Virtanen R.,University of Oulu |
Oksanen J.,University of Oulu |
Oksanen L.,University of Turku |
And 4 more authors.
Global Ecology and Biogeography | Year: 2012
Aim The role of dispersal in structuring biodiversity across spatial scales is controversial. If dispersal controls regional and local community assembly, it should also affect the degree of spatial species turnover as well as the extent to which regional communities are represented in local communities. Here we provide the first integrated assessment of relationships between dispersal ability and local-to-regional spatial aspects of species diversity across a large geographical area. Location Northern Eurasia. Methods Using a cross-scale analysis covering local (0.64m 2) to continental (the Eurasian Arctic biome) scales, we compared slope parameters of the dissimilarity-to-distance relationship in species composition and the local-to-regional relationship in species richness among three plant-like groups that differ in dispersal ability: lichens with the highest dispersal ability; mosses and moss allies with intermediate dispersal ability; and seed plants with the lowest dispersal ability. Results Diversity patterns generally differed between the three groups according to their dispersal ability, even after controlling for niche-based processes. Increasing dispersal ability is linked to decreasing spatial species turnover and an increasing ratio of local to regional species richness. All comparisons supported our expectations, except for the slope of the local-to-regional relationship in species richness for mosses and moss allies which was not significantly steeper than that of seed plants. Main conclusions The negative link between dispersal ability and spatial species turnover and the corresponding positive link between dispersal ability and the ratio of local-to-regional species richness support the idea that dispersal affects community structure and diversity patterns across spatial scales. © 2011 Blackwell Publishing Ltd.
Strand J.E.T.,Finnmark University College |
Davidsen J.G.,University of Tromsø |
Jorgensen E.H.,University of Tromsø |
Rikardsen A.H.,University of Tromsø |
Rikardsen A.H.,Norwegian Institute for Nature Research
Environmental Biology of Fishes | Year: 2011
Two groups of migrating wild Atlantic salmon (Salmo salar) smolts caught within a 1 week interval in the River Alta, northern Norway, were tagged with acoustic transmitters and measured for gill Na +, K + -ATPase activity in order to compare their smolt status with timing of sea entry. The first group of smolts had low levels of gill Na +, K + -ATPase activity and resided in the lower part of the river twice as long as the second group that had high levels of gill Na +, K + -ATPase activity. This indicates that early migrating smolts may not be completely physiologically adapted for salt water and delay their sea entry, thereby also synchronizing their seaward migration with the later migrating smolts. © 2010 The Author(s).
Huru H.L.,Finnmark University College |
Lychagin V.V.,University of Tromsø
Journal of Geometry and Physics | Year: 2013
Quantizations of actions of finite abelian groups G are explicitly described by elements in the tensor square of the group algebra of G. Over algebraically closed fields of characteristic 0 these are in one to one correspondence with the second cohomology group of the dual of G. With certain adjustments this result is applied to group actions over any field of characteristic 0. In particular we consider the quantizations of Galois extensions, which are quantized by "deforming" the multiplication. For the splitting fields of products of quadratic polynomials this produces quantized Galois extensions that all are Clifford type algebras. © 2013 Elsevier B.V.
Jobling M.,University of Tromsø |
Leknes O.,Finnmark University College
Aquaculture International | Year: 2010
The influence of feed oils on fatty acid compositions of cod liver oils was examined to investigate how fatty acid profiles are modified, and to provide estimates of feed oil compositions needed to give liver oils meeting production guidelines [3-11% 18:2n-6, 7-16% 20:5n-3 (EPA) and 6-18% 22:6n-3 (DHA)]. Attention was directed to examination of cod liver oil contents of n-6 and n-3 fatty acids, the essential fatty acids. Data, mostly taken from published work, were subjected to regression analysis to investigate the relationships between the percentages of fatty acids (18:2n-6, total n-6 fatty acids, 18:3n-3, 20:5n-3, 22:6n-3 and total n-3 fatty acids) in feed oils and their percentages in liver oils. There were highly significant relationships between feed oil and liver oil percentages for all fatty acids examined: Liver oil 18:2n-6 (%) = 0. 787 Feed oil 18:2n-6 (%) + 1. 329; (n = 21; R2 = 0. 957) Liver oil total n-6 Fatty acids (%) = 0. 831 Feed oil total n-6 Fatty acids (%) + 0. 536; (n = 21; R2 = 0. 957) Liver oil 18:3n-3 (%) = 0. 814 Feed oil 18:3n-3 (%) + 0. 022; (n = 21; R2 = 0. 985) Liver oil 20:5n-3 (%) = 0. 762 Feed oil 20:5n-3 (%) + 1. 163; (n = 21; R2 = 0. 875) Liver oil 22:6n-3 (%) = 0. 785 Feed oil 22:6n-3 (%) + 1. 393; (n = 21; R2 = 0. 831) Liver oil total n-3 Fatty acids (%) = 0. 770 Feed oil total n-3 Fatty acids (%) + 2. 558; (n = 21; R2 = 0. 851) Feed oil percentages of 18:2n-6, 20:5n-3 (EPA) and 22:6n-3 (DHA) required to produce liver oils that comply with guidelines were estimated to be 2. 5-12. 5% for 18:2n-6, 8-19. 5% for 20:5n-3 and 6-21% for 22:6n-3. Given the fatty acid compositions of commercial feed oils it is unrealistic to expect that liver oils with highly unsaturated n-3 fatty acids percentages at the high end of the recommended range (15-18% for both 20:5n-3 and 22:6:n-6) can be produced from farmed cod, but it should be possible to obtain liver oils that fulfil fatty acid composition criteria without the need to manufacture feeds that have fatty acid compositions that deviate markedly from those in current use. As an alternative to using feeds with constant fatty acid compositions throughout production, finisher feeds could be used to manipulate fatty acid compositions of liver oils, but the economics of using this feeding strategy needs to be examined before commercial implementation can be recommended. © 2008 Springer Science+Business Media B.V.
Esjeholm B.-T.,Finnmark University College |
Bungum B.,Norwegian University of Science and Technology
International Journal of Technology and Design Education | Year: 2013
The teacher plays an important role in the Technology and Design (T&D) classroom in terms of guiding students in their design process. By using concepts developed within engineering philosophy along with a framework for teacher-student interactions the design process in a T&D classroom is classified. The material shows that four of six predefined categories of design knowledge and three of seven predefined classes of activity are present in the material. Findings suggest that two categories of design knowledge, fundamental design concepts and practical considerations, are particularly significant in the students' work. The teacher's influence with respect to particularly the first of these categories is crucial for the students' design process. Direct trial is found as the students' dominating activity for solving the technological challenges. The results indicate that it is beneficial for students to be introduced to an operational principle before they can be innovative and develop their own design configuration when they establish their fundamental design concept. Curriculum developers, designers of teaching materials as well as teachers should take into account the students' need of sufficient time to explore their design configuration. © 2012 Springer Science+Business Media B.V.
Chen X.,Shanghai Ocean University |
Lindkvist K.B.,Finnmark University College
WIT Transactions on Engineering Sciences | Year: 2014
This study explores the differences in environmental disclosure (ED) of firms across China and Norway by using a content analysis index. Results indicate: (1) a positive association between environmental performance (EP) and the level of discretionary (ED. (2) The level of discretionary ED in Norway is higher than in China. (3) The influence of restrict regulations in Chinese stock exchange market is not significant to ED behaviors of good EP firms, but are significant to poor environmental performers. Copy; 2014 WIT Press.
Viken A.,Finnmark University College
Polar Record | Year: 2011
The tourism industry, research activities, and governing institutions are often seen as three very different, independent, and partly antagonistic activities and sectors - tourism as pure profit-pursuing, research as indifferent to business, and governing as controlling both. In this paper, it is argued that this is not the case on Svalbard, where a symbiotic relationship exists between the three sectors. Tourism to the islands emerged in the wake of the exploration of the Arctic in the late 1800s, but for a long period tourism rates were low, mostly due to a strict environmental regime supported by researchers in the natural sciences as well as the government. However, tourism has increased over the past 20 years, partly due to changes in the relationships between the tourism industry, researchers, and governing bodies. The involvement of research in different types of governance and its influence on tourism development will be demonstrated using theories of modern governance as points of departure for an analysis of the current situation; how tourism has provided governors with activities to govern and researchers with a rationale for comprehensive research activity. This case study shows how a symbiosis between tourism, research, and governance can be seen to emerge. Copyright © 2010 Cambridge University Press.