• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 5
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 10
  • 10
  • 5
  • 4
  • 3
  • 3
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Comparison of saproxylic beetle assemblages on four different broad-leaved tree species in south-eastern Sweden

Johansson, Helena January 2011 (has links)
Old hollow trees have declined in Europe and many saproxylic (wood-dwelling) beetles dependent on them are threatened. Several studies have been done on old hollow oaks and they have been shown to harbour a species-rich saproxylic beetle fauna. However, other broad-leaved trees might also be important to consider as supporting habitats. The aim of this study was to investigate to what extent saproxylic beetles are tree genus specialists. Pitfall traps and window traps were used to compare the saproxylic beetle fauna in oak, ash, norway maple and small-leaved lime in an area dominated by old oaks. 5,501 specimens of saproxylic beetles were found, belonging to 239 species of which 27 species were red-listed. There were significant differences in the saproxylic species composition between the four tree species, but with large overlaps. The saproxylic species found in oak overlapped to 66 % with norway maple, to 67 % with ash and to 70 % with small-leaved lime. About one third of the species in this study seem to be tree genus specialists. The conclusion is that other broad-leaved trees are important to consider in models as supporting habitats for oaks. However, to be able to save the whole fauna of saproxylic beetles, trees of all different tree species are needed.
2

The study of the broad-leaved forest vegetation in the upper section of Pa-Chang River

Lin, Yi-ying 16 August 2004 (has links)
Pa-Chang River is in Southwestern Taiwan. It originates from Fenchihu, Alishan and flows between Chiayi County and Tainan County. Its total length is 81 kilometer and total basin area is 475 square kilometer. The natural forest communities are mostly in the upper section and fragmentarily spread in the small areas that locate between farms or in complicated topography, e.g. steep slope, area difficult to reach. It is necessary to make inventory and research about these natural forest communities now to gather sufficient vegetation data which will be served as basic reference in the future local environmental management. This study is to investigate and analyze the species composition of broad-leaved forest vegetation in the upper section of Pa-Chang River. The analysis results of the vegetation data by detrended correspondence analysis¡]DCA¡^ and two-way indicator species analysis¡]TWINSPAN¡^classified the sampling plots into four forest types: I. Litsea hypophaea forest type The range of elevation is 743~1003 m. The topographic position is mainly in ridge and upper slope. II. Ficus irisana -Dendrocnide meyeniana forest type The range of elevation is 381~825 m¡CThe topographic position is mainly in lower slope and valley. III. Machilus japonica var. kusanoi -Ficus fistulosa forest type The range of elevation is 764~1229 m¡C IV. Prunus phaeosticta forest type The range of elevation is 1559~1804 m. The topographic position is mainly in upper slope. The study of correlations among environmental gradients and ordination axes indicated that the elevation is the most important environmental factor affecting the vegetation composition and distribution. Topographic position also has obvious influence on vegetation. In addition, the study of population structure shows that regeneration is continuous in present broad-leaved forest, but the forest is also continuously disturbed by artificial activities. The area of natural forest in this area might continuously be decreased, so it is important to gather sufficient vegetation data in time.
3

Ceratocystis and Ophiostoma species infecting wounds on hardwood trees, with particular reference to South Africa

Kamgan Nkuekam, Gilbert 16 July 2008 (has links)
This thesis concerns the study of selected Ceratocystis species and Ophiostoma species infecting wounds on broad-leaved trees, particularly those occurring in Africa. However, two chapters also deal with these fungi from Australia, Norway, Sweden and Austria. The dissertation is comprised of a literature review, followed by four research chapters, addressing the occurrence of Ceratocystis spp. and Ophiostoma spp. in Africa, Australia and Norway. The first chapter of the dissertation is a review of Ceratocystis spp. and Ophiostoma spp. with particular reference to Africa, hardwood tree species and wound infections. The review highlights the importance of wood and trees, especially on the African continent, and discusses the threat of deforestation. This is despite efforts by many African countries to establish forests of non-native tree species to address the demand for wood and wood products on the continent. Reforestation is associated with increased risks of the introduction of pests and pathogens, including species of Ceratocystis and Ophiostoma. The taxonomic history of these two fungal genera is summarized, and the review further focuses on the economically important species in these genera, particularly those infecting hardwood tree species on the African continent. The lack of information regarding Ceratocystis spp. and Ophiostoma spp. on hardwood trees in Africa is thus highlighted. Furthermore, the review summarised the dispersal mechanisms of these pathogens, highlighting dispersal too and infection of wounds. Ceratocystis pirilliformis was described in 2003 and it is the only species in the Ceratocystis fimbriata species complex that has pear-shaped ascomatal bases. This fungus was first described from Australia where Eucalyptus spp. are endemic. It was later reported from South Africa on Eucalyptus grandis trees. Chapter two of this dissertation attempts to address questions regarding the geographic distribution, impact and origin of C. pirilliformis in South Africa. This was in line with the fact that it has been suggested that the fungus is likely native to Australia. To address this question, surveys were conducted in many Eucalyptus planting areas in South Africa and the genetic diversity of the fungus in the country was investigated using microsatellite markers previously developed for C. fimbriata. C. pirilliformis was found in three Eucalyptus-growing areas of South Africa, which has considerably increased the known geographic range of the fungus in South Africa. The gene diversity as well as the genotypic diversity for the fungus was found to be very low in the country and the population is apparently clonal. Results thus support the view that C. pirilliformis was accidentally introduced into South Africa. In chapter three of this dissertation, O. quercus is reported for the first time from wounds on non-native Acacia mearnsii in Uganda. In addition a new Pesotum sp., P. australi prov. nom. is described from wounds on native A. mearnsii in Australia. This fungus resembles other Pesotum anamorphs of Ophiostoma in many ways, especially species of the O. piceae complex. However, it can be distinguished from these species by many morphological traits and also based on phylogenetic inference. The closest phylogenetic neighbor of P. australi prov. nom. is O. quercus. The fact that it was isolated from A. mearnsii in Australia indicates that it is probably a native fungus in that area. In chapter four, two Ceratocystis spp. and one Ophiostoma sp. are described as new to science, from wounds on native broad-leaved tree in South Africa. Three other Ophiostomaspp. are also reported in this study. Until recently, very little research has been done with regard to Ceratocystis spp. and Ophiostoma spp. occurring on native tree species in Africa. However, results presented in this chapter strongly suggest that these fungi are common on native trees in Africa and many other species, including potential pathogens await discovery. Chapter five of the dissertation reports, for the first time, Ophiostoma catonianum, O. pluriannulatum and O. quercus from native broad-leaved trees in Norway. It also reports O. catonianum for the first time from Austria and O. quercus for the first time from Sweden. In the past, very little research has been undertaken to explore the diversity of these fungi on hardwood trees in the Nordic countries or other parts of Europe, where most research has been focused on Ceratocystis spp. and Ophiostoma spp. associated with conifer-infesting bark beetles. This chapter represents a preliminary study with important discoveries. It indicates that these fungi are common on wounds on hardwood trees in Europe and emphasizes the importance of expanding these studies in the Nordic countries, to include more hosts and geographic areas. Such studies will almost certainly reveal more species and possibly new species of Ceratocystis and Ophiostoma. / Dissertation (MSc)--University of Pretoria, 2010. / Microbiology and Plant Pathology / Unrestricted
4

The relative importance of beavers (Castor fiber) and browsers on the recruitment of broad-leaved trees in riparian areas

Karlsson, Matilda January 2019 (has links)
Managed forest landscapes in Sweden are dominated by boreal coniferous forest and are deficient in broad-leaved trees. Both beavers (Castor fiber) and ungulate browsers prefer broad-leaved trees to conifers, and the interaction between multiple herbivores may have a considerable impact on the recruitment of deciduous trees in riparian areas. To evaluate the relative importance of beavers and browsers on tree recruitment, I conducted an inventory of broad-leaved tree species at five beaver sites in Färnebofjärden National Park, Sweden. At each site, five transects were established perpendicular to the shoreline in the riparian zone, resulting in a grid of 35 sample plots at each beaver site. Foraging activity of both beavers and browsers (e.g. ungulates) was concentrated to a narrow band in the riparian zone and there was a decrease in the proportion of beaver-cut and browsed trees further away from the shoreline. Beavers preferred birch (Betula spp.) and grey willow (Salix cinerea) while browsers preferred oak (Quercus robur). Beavers targeted larger trees while browsers targeted seedlings <1 cm in diameter. Old-growth trees of high conservation value, such as aspen (Populus tremula) and birch, are at risk to be cut by beaver, yet long-term protection of broad-leaved stands requires a shift in focus towards strategies that enhance tree recruitment by considering and mitigating pressure from multiple herbivores. / Svenska skogslandskap domineras av boreal barrskog med en brist på lövträd. Både bäver (Castor fiber) och betande klövvilt föredrar lövträd framför barrträd, och interaktionen mellan dessa herbivorer kan ha en betydande påverkan på föryngring av lövträd i strandnära skogar. För att utvärdera den relativa betydelsen av bävrar och betare på trädföryngring så genomförde jag en inventering av lövträdsarter och betestryck vid fem bäverlokaler i Färnebofjärden Nationalpark, Sverige. Vid varje bäverlokal lades fem transekter i rät vinkel mot strandkanten i den strandnära zonen, med provrutor var femte meter längs varje transekt, vilket resulterade i ett nätverk av 35 provrutor vid varje lokal. Både bävrars och betares (dvs. klövvilts) födosökande var begränsat till ett smalt band längs strandkanten, och andelen bävergnagda och betade trädstammar minskade med ökat avstånd från strandkanten. Bäver föredrog björk och gråvide medan betare föredrog ek. Bäver föredrog större träd medan betare föredrog groddplantor <1 cm i diameter. Gamla lövträd som är viktiga att bevara, såsom asp och björk, hotas av bäveraktivitet, men långsiktigt bevarande av lövträdsbestånd kräver ett fokus på strategier som främjar trädföryngring, bland annat genom att beakta och begränsa den sammantagna påverkan av olika herbivorers betning.
5

Modélisation d'un procédé de bûcheronnage mécanisé / Modeling of the Cut-to-Length hardwood harvesting process

Hatton, Benjamin 29 September 2014 (has links)
Dans le cadre du projet ECOMEF visant à éco-concevoir un outil de bûcheronnage pour la mécanisation des peuplements feuillus, les travaux de thèse présentés ici concernent la modélisation du système bois court, et plus particulièrement des opérations d’abattage et de façonnage (ébranchage et billonnage). Des modèles ont été développés afin d’étudier la transmission de l’effort d’entraînement au tronc par les rouleaux ainsi que l’opération d’ébranchage par choc. Parallèlement, différents démonstrateurs ont été réalisés afin de mener un certain nombre d’essais expérimentaux, qui ont permis, d’une part, une meilleure compréhension des phénomènes étudiés, et d’autre part le recalage des modèles théoriques. Enfin, une simulation dynamique multicorps a été mise en place, afin d’étudier plus précisément l’adaptation de différentes architectures cinématiques de châssis articulés aux flexuosités du tronc rencontrées dans les essences feuillues. Celle-ci intègre l’ensemble des modèles analytiques développés et permet une approche globale à travers l’interaction des modèles les uns avec les autres. / The research work presented here and realized within the framework of the ECOMEF project - which aims to develop a harvester head more specifically designed to process and fell broad-leaved trees – focuses on the modeling of the cut-to-length logging process, and particularly on the felling and processing (delimbing and bucking) operations. Several models have been developed in order to study the transmission of the feed force to the trunk or the delimbing process. In the same time, different benches have been designed in order to carry out experimental tests that allow a better understanding of the considered phenomenons as well as the experimental characterization of the models’ parameters. Finally, a multi-body dynamic simulation has been developed, in order to study the adaptation of different kinematic architectures of articulated frames to the crooked trunks specific to broad-leaved trees. This simulation contains each analytic model and allow a global study of the phenomenon by considering the interaction between each model.
6

Effekter av naturvårdsgallring på förekomsten av lunglav på ädellövträd / Effects of conservation thinning on the presence of epiphytic lichen Lobaria pulmonaria on broad leaved deciduous trees

Björkroth, Jennie January 2015 (has links)
Sun-exposed broad leaved deciduous trees have a great species diversity of epiphytic lichens. In Europe, these trees have decreased dramatically in number as wooded pastures have become overgrown with trees and bushes, and broad leaved deciduous stands have been replaced by planted coniferous trees. These are the main reasons for many lichens depending on deciduous trees being red-listed. Epiphytic lichens in overgrown areas could benefit from conservation thinning, but few studies have been performed on how this type of cutting affects the lichens. In a previous study, the presence of red-listed epiphytic lichens in a broad leaved deciduous forest was examined. After the study, thinning of trees and bushes was made. Here we study the effects of this thinning on Lobaria pulmonaria. We tested possible factors that may affect the growth of L. pulmonaria, and if there were any differences in incidence and vitality of the lichen between managed and unmanaged stands. Since Dutch elm disease and ash dieback are well spread in the area, we wanted to see if they also affected the growth of L. pulmonaria. There were no differences in incidence and growth between managed and unmanaged stands. The results were unexpected since other studies show that, for instance, increased sun exposure often has a great effect on the growth of lichens. Many elms and ashes were dead or dying and had a significant negative effect on the change of number of lobes and the lobe surface. The diseases of the trees can thus be assumed to be the greatest cause of why the lichens in the managed stand did not benefit from thinning.
7

Gap disturbance regime and tree replacement pattern in a coastal old-growth evergreen broad-leaved forest, southwestern Japan

YAMAMOTO, Shin-Ichi, 山本, 進一, IKEGAMI, Kohichi, 池上, 康一, TAJIMI, Tohru, 但見, 暢 12 1900 (has links) (PDF)
農林水産研究情報センターで作成したPDFファイルを使用している。
8

Výukové programy s botanickou tématikou pro Bečovskou botanickou zahradu / Botanical educational programs for the Bečovská Botanical Garden

ŠPAKOVÁ, Markéta January 2018 (has links)
This thesis is dedicated to educational programs in Bečov Botanic Garden. The aim of this thesis was to extend the current offer to other botanical themes. Dendrological themes were selected for new educational programs. In total, three new educational programs were created. The first one is dealing with conifers, the second with cones of conifers and the third with broad-leaved species. All new programs include worksheets and methodological instruction for lectures and teachers. Tutorial tools (determination key, scale, educational box) were also created for the cone educational program.
9

Dynamik von Phosphor im Boden und von Nährstoffen im Kronenraum von Buchenwäldern unterschiedlicher Baumartendiversität / Dynamics of phosphorus in soils and of nutrients in canopies of deciduous beech forests differing in tree species diversity

Talkner, Ulrike 24 March 2009 (has links)
No description available.
10

Diversity and tree neighborhood effects on the growth dynamics of European beech and the stand seed bank in temperate broad-leaved forests of variable tree diversity / Diversitäts- und Nachbarschaftseffekte auf die Zuwachsdynamiken von Rotbuche und die Bestandessamenbank in temperaten Laubwäldern unterschiedlicher Baumartendiversität

Mölder, Inga 13 March 2009 (has links)
No description available.

Page generated in 0.0323 seconds