Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 114-125). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 114-125). Also available on the Internet.

This thesis quantifies aspects of shade tolerance in tree seedlings of species native to the Caledonian pinewood ecosystems of Glen Affric (Highland Region, Inverness-shire). Growth, allocation and morphological responses of 15 species to irradiance under simulated forest canopy light were investigated in a nursery-based shade house experiment. The same responses of four of the 15 species (Ilex aquifolium, Alnus glutinosa, Sorbus aucuparia and Betula pubescens) to different developmental stages of Pinus sylvestris woodland were investigated in the field. The spatial and temporal growth responses of naturally regenerating S. aucuparia seedlings to shade and gap microhabitats were also studied. Data from the shade house experiment enabled further detailed exploration of the relationship between relative growth rates (RGR) and irradiance and potential cross-overs of ranks of growth in high and low light conditions.

Magistro darbe tiriama pušynų atvejinių kirtimų įtaka medynų žemutinių ardų augalijos formavimuisi. Darbo objektas: Tyrimo objektas – pomiškis, žolinė augmenija ir samanos neplynose pušynų kirtavietėse. Darbo tikslas: Ištirti pomiškio, žolinės ir samanų dangos formavimosi ypatumus pušynų atvejinių kirtimų kirtavietėse. Darbo metodai: Pušynuose, kuriuose buvo atlikti atvejiniai kirtimai buvo parinkti 4 pastovūs bareliai. Trijuose bareliuose atvejiniai kirtimai buvo vykdyti 2007 metais, o viename tyrimų barelyje – 2005 metais. Visuose bareliuose augavietės tipas buvo Nbl. Pomiškis, žolinė ir samanų danga buvo įvertinta 20 m ilgio ir 1 m pločio transektose. Pomiškis skaičiuotas nurodant rūšį ir skaičių. Samanų, žolinės augmenijos projekcinis padengimas įvertintas procentais. Darbo rezultatai: Vidutinis paprastosios pušies daigų kiekis 1 m2 antrais metais po atvejinių kirtimų sumažėjo, o karpotojo beržo daigų kiekis 1 m2 iš esmės nepasikeitė. Kai kuriose kirtavietėse antrais metais po kirtimų atsirado paprastosios eglės daigų. Kirtavietėse rastos 29 skirtingos žolių rūšys. Daugeliu atvejų antrais metais po atvejinių kirtimų kirtavietėse žolių rūšių skaičius padidėjo. Žolinės dangos vidutinis projekcinis padengimas antrais metais po atliktų atvejinių kirtimų ženkliai padidėjo. Daugiausiai vidutinis projekcinis padengimas praėjus metams po atvejinių kirtimų padidėjo kirtaviečių augalų – miškinio ir smiltyninio lendrūnų. Viso rastos 4 samanų rūšys. Vidutinis projekcinis samanų... [toliau žr. visą tekstą] / The object of the study: Undergrowth, herbs and moss in pinewoods after shelterwood cuttings. The aim of the study: The main goal of this research was to find out influence of shelterwood cuttings on herbs, moss and seedlings in pinewoods. Methods: The research areas were established in 2007 year shelterwood cutting and in 2005 year shelterwood cutting of pinewood. Saplings, herbs and moss were counted in transect which was 20 meters length and 1 meter width. There were indicated saplings species and number. Average cover projection of herbs and moss was evaluated by percent. The results: The average the number of pine’s saplings decreased in one square meter in shelter wood cuttings of second year. The average the number of birch saplings didn’t change in one square meter in essence on the following year after shelterwood cuttings. In some shelterwood cuttings were found spruce’s saplings on second year. There were 29 different species of herbs in shelterwood cuttings. In most cases the number of herbs species increased on following year. Average cover projection of herbs signally increased on the following year after shelterwood cuttings. There were founded 4 species of moss. Moss average cover projection didn’t change in essence on the following year after shelterwood cuttings.

Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves 130-145). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references (leaves 130-145). Also available on the Internet.

Dans ce projet, nous nous sommes intéressés à l’invasion du nématode du pin, Bursaphelenchus xylophilus, un ver microscopique responsable de la maladie du dépérissement du pin et causant la perte de millions d’arbres annuellement à travers le monde. Notre objectif global était d’affiner nos connaissances sur ce cas d’invasion et particulièrement d’établir l’histoire d’invasion des populations européennes. Nous avons analysé la diversité génétique neutre d’échantillons de populations naturelles de nématode du pin de l’aire native et de différentes zones envahies à l’aide de méthodes de génétique des populations. Ces analyses ont essentiellement mis en évidence que (i) l’aire native du nématode du pin est fortement structurée à fines échelles spatiales et présente une diversité génétique faible à modérée, suggérant un rôle important de la dérive génétique, non compensée par la dispersion, (ii) les populations européennes présentent une diversité génétique extrêmement faible, suggérant un seul évènement d’introduction en Europe, et que (iii) l’Amérique du Nord est la source la plus probable des populations envahissantes européennes, non le Japon et la Chine. Ce projet souligne l’intérêt que les nématologistes et les généticiens des populations ont à collaborer. La génétique des populations a en effet permis de clarifier l’histoire de l’invasion des populations européennes et ce modèle nématode, du fait de son cycle de vie complexe résultant en un cas extrême de faible diversité génétique, a permis de s’interroger sur des méthodes et analyses couramment utilisées en génétique des populations. / In this project, we were interested in the invasion of the pinewood nematode, Bursaphelenchus xylophilus, a microscopic worm responsible for the pine wilt disease and causing the annual loss of millions of trees worldwide. Our global objective was to improve our knowledge on this case of invasion and particularly to clarify the invasion history of European populations. After developing the microsatellite markers needed for our study, we analysed the genetic diversity of samples of natural populations from both the native area and invaded areas thanks to population genetics methods. These analyses revealed that (i) the native area is strongly genetically structured at fine scales and displays a low to moderate genetic diversity, suggesting an important role of the genetic drift, not compensated by dispersal, (ii) the European populations exhibit an extremely low genetic diversity, indicating a unique event of introduction in Europe and (iii) North America is the most probable source of European populations compared to China and Japan. This project is finally a good example of the benefits of collaboration between nematologists and population geneticists. Population genetics allowed to clarify the invasion history of European populations and this “nematode” model, because of its complex life cycle resulting in an extreme case of low genetic diversity, provided the opportunity to question methodologies in population genetics that are routinely used.

As a natural composite material, wood exhibits complex structural char-acteristics and diverse behavior under compression and tensile forces. Itsanisotropic nature results in mechanical properties that vary depending onthe load direction along its longitudinal, tangential, and radial grains. An im-portant property of anisotropic materials is the modulus of elasticity, whichrelates stress to strain and demonstrates directional variations.This study focuses on investigating the mechanical properties of pinewood,particularly stiffness, and deformation, in the longitudinal direction duringcompression, taking into account the effect of the sample size. The digitalimage correlation (DIC) method is utilized to measure deformation, an op-tical technique that involves tracking motion in DIC patterns. Wood, beinga renewable and natural composite resource, has been widely used as a con-struction material and for various other purposes for centuries. Its physicaland mechanical properties encompass a broad spectrum influenced by factorssuch as species, moisture content, density, and temperature.This research aims to analyze the size-dependent effects on deformation andstiffness in pine wood samples using the DIC method. Initially, three sam-ple sizes were compared, namely 10 × 10 × 10mm3, 20 × 20 × 20mm3, and25 × 25 × 100mm3 these were selected based on Afshar (2022) and Walley& Rogers (2022). However, the sample size of 20 × 20 × 20mm3 producedinsufficient results due to equipment limitations to test them under sufficientload. Among the remaining sample groups, nine specimens from each groupwere tested and compared in terms of stiffness and deformation. The exper-imental results did not provide statistically significant data supporting thepresence of a noticeable size effect between the dimensions of the samples10 × 10 × 10mm3 and 25 × 25 × 100mm3. / Trä är ett förnybart och naturligt kompositmaterial och har i århundradenanvänts som byggmaterial och för olika ändamål. Dess fysikaliska och mekaniskaegenskaper omfattar ett brett spektrum som påverkas av faktorer som fuk-thalt, densitet och temperatur. Trä som ett naturligt kompositmaterial ochdess komplexa strukturella egenskaper visar varierande beteende vid tryckoch dragkrafter. Träets anisotropa natur gör att dess mekaniska egenskapervarierar beroende på belastningsriktning, längs dess längd, tangential ellerradial riktning. För anisotropa material är elasticitetsmodulen en viktig egen-skap som varierar längs de olika riktningarna. Vilket är ett samband mellanspänning och deformationen och visar riktningsvariationer.Den här studien syftar till att undersöka de mekaniska egenskaper hos furu.Den här studien undersöker storleks-effekt i materialet furus styvhet och de-formationen längs fiberriktning (längd) vid kompression med hjälp av DigitalImage Correlation (DIC). Metoden DIC är en optisk teknik som mäter de-formationen hos material med hjälp av spårningsmönster på materialet.För att se storleks effekten hos trä jämfördes initiellt tre provstorlekar, näm-ligen 10 × 10 × 10mm3, 20 × 20 × 20mm3, och 25 × 25 × 100mm3 dessa provs-torlekar valdes baserat på Afshar (2022) och Walley & Rogers (2022). Dockproducerade provstorleken 20 × 20 × 20mm3 otillräckliga resultat på grundav begränsningar i utrustningen för att testa dem under tillräcklig belast-ning. Bland de återstående provgrupperna testades och jämfördes nio provfrån varje grupp när det gäller styvhet och deformation. De experimentellaresultaten gav inte statistiskt signifikanta data som stödjer förekomsten aven märkbar storlekseffekt mellan dimensionerna hos proven 10 × 10 × 10mm3och 25 × 25 × 100mm3.