| Abstract: | Hand-held mobile computers have the potential to become important communication tools for roaming users. As such, they will also become very personal. They will be used under a wide range of operating conditions, and tight user control will be enforced on issues like power consumption, consistency control, and trust management. Their ability to adapt will be the key to their success. In this paper we outline our notion and use of Quality of Service (QoS) to the design of adaptive software systems for mobile computers. They have been developed in the MobyDick and GDD projects. We do not emphasize on the provision of QoS guarantees. In stead, our notion of QoS is used to convey relevant and timely management information between service users and providers on the correct abstraction level. It structures adaptability management in the hand held machine, and it captures adaptability to changes both stemming from the hosting environment and user commands. As an example of how the architecture works, the importance of adaptivity of security services for personal companions are explained, and we show how our notion of QoS may realize adaptable security services. |
| URI: | http://hdl.handle.net/10037/373 |
| Abstract: | Denne rapport giver en introduction til kvalitative forskningsmetoder, der er velegnede til forskning i komplementær og alternativ behandling. Kvalitative og kvantitative metoder producerer meget forskellige former for kundskaber, som er rettet mod forskellige brugssammenhænge og formål. Vi starter med at forholde os til evidens-baseret viden og beskriver epistemologiske baggrunde for at vælge kvalitative metoder.Vi fortsætter med at give svar på følgende spørgsmål: Hvilke aspekter inden for komplementær og alternativ behandling er mest velegnede at udforske med kvalitative metoder? Derefter beskriver vi det prominente forskningsdesign til gennemførelse af kvalitativ forskning; forskningsprocessen og udvalgte forskningsmetoder: det kvalitative forskningsinterview, fokusgruppe interview og deltagerobservation. Afsluttende giver vi en kort beskrivelse af forskellige kombinationer af kvalitative og kvantitative metoder |
| Description: | The report is a revised version of: Launsø, L. and Rieper, O. (2006) Qualitative research methods in complementary and alternative treatment In: Jianping, L. (ed.) Clinical reseach methodology for evidencebased chinese medicine. Beijing, People's Medical Publishing House in China, pp 171-193 (The book in in chinese) |
| URI: | http://hdl.handle.net/10037/1184 |
| Abstract: | Hva påvirker kvaliteten på saltfisk? Saltfiskens lukt, farge, konsistens og smak bestemmer kvaliteten. Dersom torsken blir dødsstiv samtidig med at saltet strømmer inn i fiskekjøttet, oppnår man et lavere vektutbytte, vann- og saltinnhold på sluttproduktet. Fisken bør derfor saltes etter dødsstivheten for å oppnå et høyt vektutbytte. Ønsker man å minimere proteintapet fra salteprosessen og få en høy lyshet på sluttproduktet, bør fisken derimot saltes før dødsstivheten inntrer. Økt kalsium- og magnesiuminnhold samt lav pH i saltet, gir et hvitere og mer fast ferdigprodukt samt et lavere proteintap fra prosessen. Torskefilet har et høyt innhold av flerumettede fettsyrer, og er derfor spesielt utsatt for harskning og fargeendringer ved salting. Det er påvist at torskens muskel-pH (surhet) etter slakting, har betydning for evnen til å motvirke misfarging av ferdigproduktet i nærvær av kopper. Lav muskel-pH ga større misfarging samt lavere vanninnhold i fullsaltet muskel enn høy muskel-pH før salting. Kopper og jern er metaller som naturlig forekommer i fiskekjøtt, salt og drikkevann. Kopper-ioner framskynder harskning i fullsaltet torsk og gir kraftigere gul misfarging av ferdigproduktet sammenlignet med jern. Enverdig kopper er mer harskningsfremmende enn toverdig kopper. For å unngå harskning, er det vanlig å bruke antioksidanter i framstillingsprosessen. Når mer enn 0.1% natriumaskorbat blir tilsatt saltlaken, forhindrer den kopper i å fremme harskning av torskemuskelen. Antioksidantene sitronsyre og EDTA ble også undersøkt, men kun ved lav konsentrasjon sammen med kopper i saltlaken. EDTA var en effektiv antioksidant, mens sitronsyre derimot fremmet harskning i fullsaltet torsk. Doktorgradsarbeidet ble finansiert av næringsmiddelprogrammet ved Norges forskningsråd i perioden 1997-2001. |
| URI: | http://hdl.handle.net/10037/1819 |
| Abstract: | This thesis addresses negotiation of bindings in QoS aware open systems and in particular how to characterize possible contracts, requirements and capabilities of heterogeneous environments. Our approach is (1) to use trading of policies as the principle for negotiation and (2) the use of declared or rule-based conformance for QoS statements to be used in negotiation and (3) a middleware binding framework supporting negotiable bindings. A policy is an architectural entity which encapsulates a potential QoS contract plus a resource and implementation configuration to enforce the contract. The contract part (profile) consists of an obligation to be matched with requirements and an expectation to be matched with descriptions of the environment. A policy may encapsulate how implementation components and properties of environments are combined to achieve a QoS level. Policy trading is the proposed principle for negotiation. Potential contracts may be orthogonal to interfaces and interface types, and are associated with some trading service. Negotiation is essentially to collect requirements and environment descriptions from participants and match these with policies. We investigate an approach to contract matching based on declared conformance. An important contribution is the development of a declarative expression language for profiles, requirement and environment descriptions used in negotiation at run-time. We propose to define conformance as rule bases. Such rule bases can be compiled to efficient conformance checking code. We propose two composition operators to combine expressions at run-time and develop the foundations of a generic conformance checking algorithm for profile expressions. A prototype binding framework is developed, supporting activation of bindings, pluggable binder and activator components. The framework is extended to support negotiation using policy trading and profile expressions. The approach is validated by examples and proof of concept implementations. A profile model compiler, a policy trader and the binding framework are implemented and applied to example applications. |
| Description: | The trial lecture of the thesis defence is available in Munin at http://hdl.handle.net/10037/2840. |
| URI: | http://hdl.handle.net/10037/1350 |
| Abstract: | Background: In order to maintain both quality and efficiency of health services in a small country with a scattered population, Norway established a monopoly system for 38 highly specialized medical services. The geographical distributions of these services, which are provided by one or two university hospitals only, were analysed. Methods: The counties of residence for 2 711 patients admitted for the first time in 2001 to these 31 monopolies and 7 duopolies were identified. Results: The general tendency observed was that with increasing distance from residential home to monopoly hospitals there was a declining coverage of these health services. The same pattern was found even with regard to explicit diagnoses or treatments such as organ transplantations (except renal transplantations). Duopolies seemed to yield a more even geographical distribution of the services. Conclusion: Monopolies may serve as a useful means for maintaining quality in highly specialized medical services, but seem to have an inherent tendency to do this at the expense of geographical equality. |
| URI: | http://hdl.handle.net/10037/1260 |
| Abstract: | Omorganisering i oppdrettsnæringen har ført til større og mer mekaniserte anlegg med høy slaktekapasitet. I dag kontrolleres normalt restblod i fiskefilet ved visuell inspeksjon. Dette er arbeidskrevende og innebærer subjektive evalueringer som muliggjør høy grad av unøyaktighet. Fargen på fiskemuskelen er også et viktig kriterium når kunder vurderer kvalitet, og disse fargeforandringene skyldes ofte restblod. Oppgaven belyser, i første omgang, de ulike enhetsoperasjonene ved slakting av fisk og hvilke effekter de har på selve utblødningen. I tillegg belyser den muligheten for å bruke en objektiv og hurtig målemetode for restblod i fiskemuskel, som er basert på visuell- og nærinfrarød spektroskopi. Restblod fører til store økonomiske tap for fiskeindustrien som følge av nedklassifisering. Området er lite belyst, og denne oppgaven søker å bidra med ny kunnskap rundt hvilke faktorer som påvirker mengden restblod i fiskemuskel. En kjemisk målemetode ble brukt som referanse og sammenlignet opp mot dagens visuelle inspeksjon samt en visuell- og nærinfrarød (VIS/NIR) spektroskopi metode. Sistnevnte innebærer måling av absorbsjon/refleksjon av lys fra bl.a. fargepigmentet hemoglobin, og metoden benyttes allerede i annen næringsmiddelindustri. Oppgaven viser at mengden blod i fiskemuskel påvirkes av stress før slakting, avlivingsmetoder, kjøling og lagring. Spesielt ble det funnet at bedøving ved bruk av slag før bløgging er optimalt med hensyn til restblod. Bruk av karbondioksid anbefales derimot ikke. VIS/NIR metoden anbefales ikke brukt industrielt, men metoden kan forbedres og automatiseres. Det foreslås å anvende avbildende VIS/NIR spektroskopi for å vurdere restblod i fiskefilet, med spektra fra fiske hemoglobin som referanse. |
| Description: | The papers of this thesis are not available in Munin: 1. Olsen, S.H., Sørensen, N.K., Stormo, S.K. and Elvevoll, E.O.: 'Effect of slaughter methods on blood spotting and residual blood in fillets of Atlantic salmon (Salmo salar)', Aquaculture (2006) 258, 462-469. Available at http://dx.doi.org/10.1016/j.aquaculture.2006.04.047 2. Olsen, S.H., Sørensen, N.K., Larsen, R., Elvevoll, E.O. and Nilsen, H.: 'Impact of pre-slaughter stress on residual blood in fillet portions of farmed Atlantic cod (Gadus morhua) - Measured chemically and by Visible and Near-infrared spectroscopy', Aquaculture (2008) 284, 90-97. Available at http://dx.doi.org/10.1016/j.aquaculture.2008.07.042 3. Olsen, S.H. and Elvevoll, E.O.: 'A pH induced shift in the haemoglobin spectra – A spectrophotometeric comparison of fish (Gadus morhua) and mammalian haemoglobin', Journal of Agriculture and Food Chemistry (2011) 59 (4), pp 1415–1422. Available at http://dx.doi.org/10.1021/jf1036273 |
| URI: | http://hdl.handle.net/10037/3590 |
| Abstract: | Natural transformation is one of three ways for bacteria to acquire genetic material (DNA) horizontally. Several hypotheses exist for why some bacteria have this ability to take up DNA, and what the incoming DNA is used for. These include use of DNA for recombination, repair or as nutrients. This master study focuses on the “food hypothesis”. This hypothesis implies that the exogenous DNA is either used in the synthesis of new DNA and RNA molecules, or broken down to carbon, nitrogen and phosphate to use as energy and in synthesis of new nucleotides. The naturally transformable Acinetobacter baylyi is used as a model organism to test this hypothesis. By removing the comFECB operon from the wild type bacteria a non-transformable strain is produced. Comparisons of growth rates between these two strains in monocultures give the absolute fitness, whereas co-cultures give the relative fitness. If the comFECB operon has evolved as a means to use DNA as food, than the transformable wild type would have a fitness advantage over the non-transformable strain when DNA is the only nutrient in the growth media. Although the addition of DNA to the growth media resulted in increased growth of A. baylyi, this effect was seen in both strains, independently of functional com-genes. This implies that DNA is in fact used as nutrients by this species, but not only by natural transformable bacteria with intact comFECB operons. The experiments done in this thesis do therefore not offer support for the “food hypothesis”. |
| URI: | http://hdl.handle.net/10037/2208 |
| Abstract: | How do Argentina’s found grandchildren experience knowing the truth about their biological origins, and how does this influence their identity? Their identification, restitution and reconstruction of identity has been and will continue to be closely linked to Argentina’s transitional justice process. We need more knowledge about how victims of political violence experience transitional justice measures. Therefore, one of the purposes of this thesis is to contribute to a more profound understanding of what such processes imply for a society and its individuals through the context-specific study of one particular aspect of a transitional justice process. For all of my informants, getting to know the truth about their biological origins has been experienced as what Giddens (1991) refers to as a fateful moment that would change their lives. Each individual has a unique story, yet, I find that the found grandchildren have all gone through three different phases; identification – restitution – reconstruction of identity. I consider the identification and restitution as events limited in time, whereas I view the reconstruction of identity as an ongoing and continuous process in which each person is trying to restore a sense of coherent identity. |
| URI: | http://hdl.handle.net/10037/4351 |
| Abstract: | This paper proposes an external sorting algorithm for large data as an alternative to the widely used merge-sort algorithm. The algorithm we present is an application of the widely known quick-sort algorithm to large sequences of data stored externally on a disk device. The problem with the merge-sort algorithm is not its time complexity but the large amount of time it requires to output its first results. This is a serious problem in the context of pipelined processing, since the operations consuming its result will have to wait all that time before they can start their processing, thus limiting the degree of vertical parallelism achievable by pipelined processing Using quick-sort instead of merge-sort for external sorting in pipelined data processing systems results in an optimization in the order of $log N$ (where N is the size of the data sequence to be sorted) for the entire query pipeline where the sorting operation is involved. |
| URI: | http://hdl.handle.net/10037/370 |
| Abstract: | Cellular quiescence is a state of reversible proliferation arrest that is induced by anti-mitogenic signals. The endogenous cardiac glycoside ouabain is a specific ligand of the ubiquitous sodium pump, Na,K-ATPase, also known to regulate cell growth through unknown signalling pathways. To investigate the role of ouabain/Na,K-ATPase in uncontrolled neuroblastoma growth we used xenografts, flow cytometry, immunostaining, comet assay, real-time PCR, and electrophysiology after various treatment strategies. The ouabain/Na,K-ATPase complex induced quiescence in malignant neuroblastoma. Tumour growth was reduced by >50% when neuroblastoma cells were xenografted into immune-deficient mice that were fed with ouabain. Ouabain-induced S-G2 phase arrest, activated the DNA-damage response (DDR) pathway marker γH2AX, increased the cell cycle regulator p21Waf1/Cip1 and upregulated the quiescence-specific transcription factor hairy and enhancer of split1 (HES1), causing neuroblastoma cells to ultimately enter G0. Cells re-entered the cell cycle and resumed proliferation, without showing DNA damage, when ouabain was removed. Conclusion: These findings demonstrate a novel action of ouabain/Na,K-ATPase as a regulator of quiescence in neuroblastoma, suggesting that ouabain can be used in chemotherapies to suppress tumour growth and/or arrest cells to increase the therapeutic index in combination therapies. |
| URI: | http://hdl.handle.net/10037/4981 |
| Abstract: | The present paper investigates the contexts in which the so-called n-words - the items which are taken to be Negative Polarity Items in Slavic languages - unexpectedly occur without a licensing negation marker on the verb. This particular usage of n-words seems to point towards an ambiguous behaviour of the items in question: in an antimorphic contexts they are NPIs; otherwise they are negative quantifiers with negation having narrow scope w.r.t. the event variable. The paper tries to answer the question why the latter use is restricted to certain adverbials. I argue that the availability of 'logophoric' n-words turns on the issue of what the adverbial PP is predicated of. This intuition is formalized using Higginbothamistic view on l-(exical) syntax, where the nature of $Theta$-identification of the adverbial with the verb is of fundamental importance. The semantic requirement, however, turns out to be insufficient. Hence the syntactic position of the PP on the hierarchy of thematic roles also has to be taken into consideration. The data analysed include adverbials of manner, reason, time, place, direction, resultatives and depictives. |
| Description: | In special issue: Proceedings of SCL 19 |
| URI: | http://hdl.handle.net/10037/269 |
| Abstract: | This paper explores the issue of using marine reserves in combination with quotas as fisheries management tools using a patchy environment model as the biological foundation. The rent generated by fishing on the total population, using optimal quotas as a management tool, is compared to the rent from the fishery when managed with quotas and a marine reserve. This is done under different assumptions regarding the type of dispersal mechanisms between the sub-populations in the different patches and under two different assumptions regarding the harvest function. It is shown that the profitability of reserve creation depends on the migration rate relative to the intrinsic growth rate and the cost / price ratio and that the choice of harvesting function is of particular importance when the costs of fishing are high. |
| URI: | http://hdl.handle.net/10037/915 |
| Abstract: | The thesis is an attempt to arrive at the cartography of the low thematic domain of the clause using data from various argument structure constructions in Polish. It assumes the existence of a universal functional sequence (cf. Cinque (1999)) and the theory of morphology where morphemes are lexically specified to spell out chunks of the universal sequence. Furthermore, functional vocabulary items are flexible in the sense that they can be inserted for different subsets of their lexical specification. Part I deals with Polish conjugation class markers (so-called Themes), where a typology of the latter is proposed: high Themes spell out a superset of the featural hierarchy spelled out by low Themes. Two domains sensitive to the type of Theme are discussed: (i) verbs displaying the reflexive clitic (i.e. reflexive, anticausative, prefix-induced, and Reflexiva Tantum) and (ii) the Impersonal construction in -NO/TO. The conclusion is that bare stem inchoatives (i.e. Polish low Theme stems or inchoatives in causativizing languages) should not be equated with anticausatives. More generally, the notion ’split intransitivity’ should be deconstructed, given a very fine-grained universal sequence. Part II focuses on another type of functional vocabulary items, so-called Event Separators (ES) - morphology occurring in various participial constructions, as well as nominalizations. The main tenet is that the constant negotiation of spell out options between two items with overlapping lexical specification (i.e. Theme and ES) results in a typology of participial or nominalizing constructions. Furthermore, an analysis of Impersonal -NO/TO is advanced, where an analogy to Germanic/Romance Perfect Tense is drawn. The specific algorithm of mapping assumed to hold between the verbal and nominal functional sequence derives semantic restrictions on external arguments (i.e. features on Silverstein’s Hierarchy, e.g. animate, human, pronoun, etc.), as well as different degrees of ’subjecthood’. |
| URI: | http://hdl.handle.net/10037/991 |
| Abstract: | Resymé Introduksjon: Radiofrekvensablasjon har blitt brukt som behandling mot supraventrikulære takykardier ved UNN siden 2004. Metoden går ut på at man via katetre plassert intrakardielt kartlegger utløsende fokus og/eller ledningsbaner som bidrar til å opprettholde arytmien. Ved å applisere radiofrekvensenergi over de ønskede områder kan man destruere substratet for arytmien. Jeg har gått gjennom journaler på pasienter som fikk radiofrekvensablasjonsbehandling i perioden 2004-2006, og vil i denne oppgaven se nærmere på suksess-, residiv og komplikasjonsrater. Metode: Man gikk gjennom journaler til pasienter som har fått behandling for anfallsvis atrieflutter, AV-nodal reentry takykardi og for Wolff-Parkinson White syndrom i perioden. Pasienter som fikk ablasjonsbehandling for andre årsaker ble ekskludert fra undersøkelsen. Man registrerte data som gikk på type arytmi, alder og kjønn, primær suksess ved inngrepet, eventuelt senere residiv, prosedyretid og komplikasjoner. Resultater: Materialet omfatter 150 pasienter som fikk utført ablasjonsbehandling i perioden. Arytmiene fordelte seg med AVNRT 49 % (74/150), atrieflutter 23 % (35/150), manifest WPW 13 % (19/150) og skjult WPW 15 % (22/150). For det totale materialet var suksessraten 92,0 % (138/150), residivraten hos de med primært vellykket resultat var 8,0 % (n = 11), og komplikasjonsraten 4,7 % (n = 7). Menn utgjorde 59 % av pasientmaterialet, gjennomsnittlig alder var 49 ± 15 år. Gjennomsnittlig prosedyretid var 127 ± 43 minutter. For AV-nodal reentry takykardi (n = 74) var primær suksessrate 97,3 % (72/74), med en residivrate på 5,6 % (4/74). For Wolff-Parkinson White syndrom (n = 41) var primær suksessrate 80,5 % (33/41) og residivraten var 3,0 % (1/41). For anfallsvis atrieflutter (n = 35) var primær suksessrate 94,3 % (33/35) og residivrate 18,2 % (6/35). Diskusjon / Konklusjon: Resultatene fra perioden 2004-2006 viser at radiofrekvensablasjon er en effektiv behandling for pasienter med atrieflutter, Wolff-Parkinson White syndrom og AV-nodal reentry takykardi. Det var relativt få alvorlige komplikasjoner til behandlingen. |
| URI: | http://hdl.handle.net/10037/1664 |
| Abstract: | A new scheme for detection of vesicoureteral reflux (VUR) in children has recently been proposed in the literature. The idea is to warm bladder urine via microwave exposure to at least fever temperatures and observe potential urine reflux from the bladder back to the kidney(s) by medical radiometry. As a preliminary step toward realization of this detection device, we present non-invasive temperature monitoring by use of microwave radiometry in adults to observe temperature dynamics in vivo of a water-filled balloon placed within the oral cavity. The relevance of the approach with respect to detection of VUR in children is motivated by comparing the oral cavity and cheek tissue with axial CT images of young children in the bladder region. Both anatomical locations reveal a triple-layered tissue structure consisting of skin–fat–muscle with a total thickness of about 8–10 mm. In order to mimic variations in urine temperature, the target balloon was flushed with water coupled to a heat exchanger, that was moved between water baths of different temperatures, to induce measurable temperature gradients. The applied radiometer has a center frequency of 3.5 GHz and provides a sensitivity (accuracy) of 0.03 °C for a data acquisition time of 2 s. Three different scenarios were tested and included observation through the cheek tissue with and without an intervening water bolus compartment present. In all cases, radiometric readings observed over a time span of 900 s were shown to be highly correlated (R ~ 0.93) with in situ temperatures obtained by fiberoptic probes. |
| URI: | http://hdl.handle.net/10037/5057 |
| Abstract: | Sustainable livelihood means to live with the close harmony without losing ecosystem both in economical, social, environmental and cultural elements. Or other ways we can say live without the degradation of economical, social, environmental and cultural elements of an indigenous group is sustainable livelihood. Radio has the strong role in the sustainable livelihood of indigenous people. Mother language is the most powerful instrument of preserving and developing our tangible and intangible heritage. Promoting the recognition and practice of mother language media, especially radio, has its distinctive role. Radio is the cheapest and easiest, strongest and personal medium that can be useful every moment of a person’s life, though he/she is at works. So the radio has an impact on the indigenous people’s sustainable livelihood. ‘Sal Gittal’ is one of the programme broadcast from Bangladesh Betar, Dhaka for the Garo people. Within last thirty years they have had enormous benefit like lyricists, singers, artists come from them, they could present their language and culture in the national radio, which gives them inspiration to protect and flourish their culture and heritage. On the other hand Rakhaing, has no radio programme of their own. So their language and culture has no significant development, even diminishing day by day. Some of the Rakhaing people are now trying to retrieve their language, culture and heritage. Study findings showed that the Rakhaing feel them excluded from the world; and only a single programme in radio can give them a feeling of being a member of the world. |
| URI: | http://hdl.handle.net/10037/156 |
| Abstract: | Avhandlingen henter sitt tema fra et videreutdanningsstudium i aksjonslæring som Universitetet i Tromsø på oppdrag fra tre svenske kommuner arrangerte for en gruppe svenske lærere. I dette studiet har Furu opptrådt som prosjektleder, lærer, veileder og aksjonsforsker. I aksjonsforskning er det et nært samarbeid mellom forsker og praktikere som kan betegnes som et forskende partnerskap. I avhandlingen skiller man mellom aksjonslæring som planlagt, systematiske endringsarbeid som lærerne og skolelederne gjør i sin skolehverdag og aksjonsforskning som det forskerne foretar seg når de forsker sammen med lærere og skoleledere i skolen. Studiet var lagt opp slik at lærerne skulle arbeide med og gjennomdrøfte problemer hentet fra deres eget praksisfelt. Det viste seg at de gjennom arbeidet med egne problemer tok til å engasjere seg så sterkt at Furu stiller spørsmål om hun har funnet ”en magisk kilde”. Det er dette spørsmålet som danner basis for avhandlingen, og det blir søkt og belyst ved å gjennomgå åtte av studentenes aksjonslæringsprosjekter, ved å intervjue de samme lærerne et år etter avsluttet utdanning, og ved å drøfte de funn som blir gjort i lys av relevant pedagogisk teori. Funnene er analysert i en kognitiv og en emosjonell kategori. I kapitlet med analyse av den kognitive kategorien er forholdet mellom lærerforskning og aksjonslæring drøftet. Funnene indikerer at lærerne har oppnådd en pedagogisk styrking som resultat av sin deltakelse i aksjonslæringsprosessen. Styrkingen var ikke bare var intellektuell, den innebar også utviklingen av et sterkt personlig engasjement. Hvordan skal dette forklares? For å besvare spørsmålet er ulike emosjonsteorier anvendt for å analysere lærernes svar. Som konklusjon på det lærerne har sagt i intervjuene, har Furu tatt i bruk metaforen ”rak lærerrygg” for å uttrykke at aksjonslæring evner å skape autonome og stolte lærere. |
| URI: | http://hdl.handle.net/10037/941 |
| Abstract: | Global change is expected to lead to range shifts of plant species. The ecological mechanisms underpinning these shifts are currently not well understood. Here, we compared ecological responses possibly underlying southern range contraction and northern range expansion of Empetrum nigrum, a key species in northern heathlands, which may be related to global change. We hypothesized a negative response to warming in the ‘south’ (i.e. the Netherlands) and a positive response at the northern range margin (the tundra on Svalbard). Open top chambers (OTCs) were used to simulate global warming. In the ‘south’, OTC warming caused enhanced shoot growth and growth rate, biomass increment, advanced phenology, larger and heavier berries of Empetrum, while its growing season was extended by 75 days. Under OTC warming co-occurring Calluna vulgaris also showed an increased growing season length (by 98 days) as well as increased shoot growth rate and biomass growth, plant cover and height. Still, we found no evidence for increased competitiveness relative to Empetrum. In the ‘north’, Empetrum responded with increased shoot and biomass growth, enhanced berry development and ripening to warming. These responses exceeded those of co-occurring Cassiope tetragona with the exception of its biomass response. The direct and indirect ecological responses found do not readily explain the observed northward retreat of Empetrum at the southern range margin. The direct ecological responses found at its northern range margin are, on the other hand, in line with the increased occurrences of this species on Svalbard. |
| URI: | http://hdl.handle.net/10037/5052 |
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