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Hvordan ettervirkningene av en 26 år gammel fin-skala forstyrrelse og lystilgang i skogbunnen påvirker etablering og vekst hos gran, furu, rogn, bjørk og hårfrytle i en granskog i SØ-Norge
No full textForstyrrelser og suksesjoner er en del av den naturlige dynamikken i boreal skog, og skaper store og små, romlige og tidsmessige endringer. Endringene fører til heterogenitet i økosystemene og kan øke artsdiversiteten. Vanlige forstyrrelser i skogen er blant annet stormer som fører til trefall og rotvelt, som igjen fører til åpne glenner med bar jord som legger til rette for etablering av tidlig suksesjonsarter, og åpne glenner i kronedekket som gir ekstra sollys i skogbunnen, noe som kan være avgjørende for spiring og etablering av trær.
Plantene i skogen har ulike etablerings- og revegeteringsstrategier for å fylle de forskjellige nisjene i naturen. Dette har jeg undersøkt nærmere på artsnivå. Derfor har jeg valgt ut fire tre-arter og en sivplante for (1) å finne ut om forskjellig grad av små-skala forstyrrelser påvirker hvordan gran, furu, rogn, bjørk og hårfrytle har etablert seg i skogbunnen 26 år etter forstyrrelsen, og (2) om lystilgangen på skogbunnen påvirker etablering av de nevnte artene.
Jeg samlet inn data på forekomst og mengde for de fem artene fra 75 vegetasjonsruter som ble brukt i et små-skala forstyrrelseseksperiment i 1993. Eksperimentet simulerte en forstyrrelsesgradient, som varierte fra ligge- og brunstgroper laget av rådyr og elg, til eksponert mineraljord etter rotvelt. Jeg målte diffust og direkte lystilgang ved kalkulere ut fra Fisheye-fotografier av kronedekket i de samme rutene. Jeg analyserte dataene med Linear Mixed-Effects models og forenklet modellene til jeg kom frem til den best tilpassede modellen; «minimal adequate model».
Resultatene viste at det var signifikant mer gran og hårfrytle i to av de tre behandlingene med høyest grad av forstyrrelse, enn i de resterende behandlingen. Dette tyder på at gran og hårfrytle krever en forstyrrelse som gir dem tid til å etablere seg på jord fri for strøfall før konkurranse fra lyngplanter og mose inntreffer. Videre viste resultatene at forekomst av rogn avtok signifikant med økende mengde diffust lys. Dette tyder på at rogn, begunstiges av å spire på de mørkere delene av en generelt mørk skogbunn
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
How aftereffects of a 26 year old fine-scale disturbance and light availability on the forest floor affects the establishment and growth of Norway spruce, Scots pine, rowan, downy birch and hairy wood-rush in a spruce forest in SE-Norway
Get PDFForstyrrelser og suksesjoner er en del av den naturlige dynamikken i boreal skog, og skaper store og små, romlige og tidsmessige endringer. Endringene fører til heterogenitet i økosystemene og kan øke artsdiversiteten. Vanlige forstyrrelser i skogen er blant annet stormer som fører til trefall og rotvelt, som igjen fører til åpne glenner med bar jord som legger til rette for etablering av tidlig suksesjonsarter, og åpne glenner i kronedekket som gir ekstra sollys i skogbunnen, noe som kan være avgjørende for spiring og etablering av trær.
Plantene i skogen har ulike etablerings- og revegeteringsstrategier for å fylle de forskjellige nisjene i naturen. Dette har jeg undersøkt nærmere på artsnivå. Derfor har jeg valgt ut fire tre-arter og en sivplante for (1) å finne ut om forskjellig grad av små-skala forstyrrelser påvirker hvordan gran, furu, rogn, bjørk og hårfrytle har etablert seg i skogbunnen 26 år etter forstyrrelsen, og (2) om lystilgangen på skogbunnen påvirker etablering av de nevnte artene.
Jeg samlet inn data på forekomst og mengde for de fem artene fra 75 vegetasjonsruter som ble brukt i et små-skala forstyrrelseseksperiment i 1993. Eksperimentet simulerte en forstyrrelsesgradient, som varierte fra ligge- og brunstgroper laget av rådyr og elg, til eksponert mineraljord etter rotvelt. Jeg målte diffust og direkte lystilgang ved kalkulere ut fra Fisheye-fotografier av kronedekket i de samme rutene. Jeg analyserte dataene med Linear Mixed-Effects models og forenklet modellene til jeg kom frem til den best tilpassede modellen; «minimal adequate model».
Resultatene viste at det var signifikant mer gran og hårfrytle i to av de tre behandlingene med høyest grad av forstyrrelse, enn i de resterende behandlingen. Dette tyder på at gran og hårfrytle krever en forstyrrelse som gir dem tid til å etablere seg på jord fri for strøfall før konkurranse fra lyngplanter og mose inntreffer. Videre viste resultatene at forekomst av rogn avtok signifikant med økende mengde diffust lys. Dette tyder på at rogn, begunstiges av å spire på de mørkere delene av en generelt mørk skogbunn.Disturbances and successions are parts of the natural dynamics of the boreal forest. It creates large and small, spaciotemporal changes. The changes lead to heterogeneity in the ecosystems, which can increase the species diversity. Normal disturbances in the forest may be windstorms that causes trees to uproot, or tree falls, and makes gaps in the forest floor which enables establishment of pioneer species, and gaps in the canopy so that more sunlight reaches the forest floor, which could be crucial for tree seedlings to establish.
The plants of the forest have different strategies of establishment and growth to fill all niches. I have examined four tree-species and a rush (1) to find out if different treatments of fine-scale disturbance are affecting the establishment of Norway spruce, Scots pine, rowan, downy birch and hairy wood-rush 26 years after the disturbance, and (2) if light availability on the forest floor affects the establishment of the same species.
I collected data of frequency for the five species from 75 plots which were used in a fine-scale disturbance experiment in 1993. The experiment simulated a disturbance gradient, spanning from heat and rut hollows made of roe-deer and elk, to exposed mineral soil caused by tree uprooting. I measured the diffuse and direct light availability by calculating it from Fisheye-photographs of the canopy from the same plots. I analysed the data by using Linear Mixed-Effects Models and simplified the model to achieve the best fitted model; “minimal adequate model”.
My results showed that there were significantly more Norway spruce and hairy woodrush in two of the three treatments with the highest degree of disturbance. This suggests that Norway spruce and hairy wood-rush needs a disturbance that gives them time to establish and grow on a litter-free ground before the clonal ingrowth of competing shrubs and mosses reaches inn from the margins. The results showed further that the occurrence of rowan went down significantly as the diffuse light increased. This may suggest that rowan establishment and growth benefits from establishing on the darker parts of the dark forest floor.M-N
Data from: Nest building in titmice Paridae: Selectivity in bryophyte use
No full textIn many bird species, reproductive success is dependent on nest quality. However, detailed data on nest composition are scarce, and quantitative analyses have generally used only rough categories, without species identification. Bryophytes dominate the nests of many passerine bird species, but little is known about whether birds have preferences for certain species. In this study, we determined the bryophyte species composition in nests of blue tits Cyanistes caeruleus and great tits Parus major in a forest near Oslo, Norway. We also sampled the abundance of the bryophyte species in plots on the forest floor surrounding a subset of the great tit nests. Blue tits and great tits both used 15 bryophyte species as nest materials, mainly the same pleurocarpous species but in different proportions. The tits preferred highly branched bryophyte species, i.e. Pleurozium schreberi, Rhytidiadelphus squarrosus and Sanionia uncinata, but avoided common forest-floor bryophyte species that are sparsely branched. Great tits clearly collected bryophyte species selectively. We also found that bryophyte species content in great tit nests in the same nest box in different years was very similar. Our results also indicated that the great tits collected bryophyte nest materials close to their nests, mostly within 5 m, supporting the view that collecting nest materials is costly. We review several hypotheses to explain why the tits prefer certain species of bryophytes as nest materials. These include handling costs and their suitability as structural materials. We recommend field experiments to test specific hypotheses, and to study whether preferences are heritable.All files are txt-files and can be opened in most softwares.The data was collected in a forest nearby Oslo SE Norway and consists of two main types of data (but with derived files): bryophyte species composition of 69 nests of blue- and great tit and data on the bryophyte species composition, sampled in 167 plots, surrounding nine trees with nest boxes. Where the bryophyte species composition of these nests was recorded in two different years. For further details, please read the readme files and the published paper
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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