I arbetet studerades volymtillväxt hos några försök med lärk och deras hybrider i Siljansfors försökspark (SLU). Mätningar gjordes hösten 2021 på ett lärkförsök, anlagt våren 2015. Syftet var att för första gången i Sverige testa och jämföra på en och samma lokal produktionspotentialen hos japansk (Larix kaempferi), europeisk (Larix decidua) och rysk lärk (Larix sukaczewii), samt korsningar mellan dessa i relation till tall (Pinus sylvestris), gran (Picea abies) och contorta (Pinus contorta). Jämförelser gjordes också med mätningar på två tidigare försök på samma försökspark anlagda 1963 och 1965 bestående av rysk- och europeisk lärk, tall, gran, vårtbjörk och glasbjörk, dock inga hybrider. Resultatet från jämförelserna i försök 9297 från 2015 visar att europeisk lärk har den största volymutvecklingen mellan 2015 och 2021.

Today's arid and semi-arid zones of the Mediterranean are affected by desertification, resulting from various factors, including climatic variations and human activities such as overcultivation, overgrazing and deforestation. Afforestation programs are one of the most effective means in preventing desertification. For many years Libya has had afforestation programs in order to restore degraded land and in response to rapid desert encroachment in the north east of Libya, in the area called the Jabal Akhdar (Green Mountain), which has been investigated in this study. The purpose of this research was to investigate the relative roles of exotic compared to native tree species in preventing desertification and enhancing degraded land restoration in the Jabal Akhdar. The effect of environmental factors on exotic compared to native tree species have been assessed by observations on growth and reproductive success of the species, including variables of stocking rate, trunk diameter, tree height, crown diameter, tree coverage, natural mortality, felling and seedling regeneration, as well as calculated variables, derived from these measurements. The effects of methods and age of afforestation on the promotion of biological diversity have been investigated using the Shannon-Wiener diversity index. The effects of tree species on soil depth have also been investigated. Multivariate statistical analyses of site, species and environmental data, using both cluster analyses and factor analyses have been performed, with the aim of determining what is influencing the species, crops or differentiating between the sites, based on soil depth, angle of slope, altitude, rainfall and air temperature values. Pinus halepensis showed success in its growth and regeneration, particularly at higher altitudes and steeper slopes. Cupressus sempervirens was successful in growth and regeneration in the mountains. The exotic Eucalyptus gomphocephala was very successful in its growth, but did not regenerate well, while the exotic Acacia cyanophylla trees had a failure of both growth and regeneration. E. gomphocephala species appeared to favour relativley the flatter (non-mountain) sites, while A. Cyanophylla appeared to favour relativly the mountain sites. All the species responded positively to greater rainfall and deep soil, but they differed in where they were most likely to be successful. Environmental factors such as climate, terrain and soil are the main determinants of species distribution in the study area, in addition to their impact on the growth of the main trees. There appeared not to be any relationship between biodiversity and whether the main trees were native or exotic, and only P. halepensis showed any negative effect on the abundance of shrubs. There was greater diversity of trees and shrubs generally at the younger sites than the old sites. The present study emphasises the current mismanagement of planted forests, particularly with overgrazing contributing to desertification, through preventing tree growth and eliminating most sapling regeneration. This study concludes by making recommendations for more effective choice of tree species to plant, and for subsequent management to improve afforestation programmes in the Jabal Akhdar area. / The Libyan Higher Education Ministry

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No description available.

No description available.

Islands are hotspots of plant endemism and are particularly vulnerable to the establishment (naturalization) of alien plant species. Naturalized species richness on islands depends on several biogeographical and socioeconomic factors, but especially on remoteness. One potential explanation for this is that the phylogenetically imbalanced composition of native floras on remote islands leaves unoccupied niche space for alien species to colonize. Here, we tested whether the species richness of naturalized seed plants on 249 islands worldwide is related to the phylogenetic composition of their native floras. To this end, we calculated standardized effect size (ses) accounting for species richness for three phylogenetic assemblage metrics (Faith’s phylogenetic diversity (PD), PDses; mean pairwise distance (MPD), MPDses; and mean nearest taxon distance (MNTD), MNTDses) based on a phylogeny of 42 135 native island plant species and related them to naturalized species richness. As covariates in generalized linear mixed models, we included native species richness and biogeographical, climatic and socioeconomic island characteristics known to affect naturalized species richness. Our analysis showed an increase in naturalized species richness with increasing phylogenetic clustering of the native assemblages (i.e. native species more closely related than expected by chance), most prominently with MPDses. This effect, however, was smaller than the influence of native species richness and biogeographical factors, e.g. remoteness. Further, the effect of native phylogenetic structure (MPDses) on naturalized species richness was stronger for smaller islands, but this pattern was not consistent across all phylogenetic assemblage metrics. This finding suggests that the phylogenetic composition of native island floras may affect naturalized species richness, particularly on small islands where species are more likely to co-occur locally. Overall, we conclude that the composition of native island assemblages affects their susceptibility to plant naturalizations in addition to other socioeconomic and biogeographical factors, and should be considered when assessing invasion risks on islands.

Invasive Pflanzenarten, die sich durch hohe Vermehrungsratem und breite Umwelttoleranz auszeichnen, verdrängen oft einheimische Flora, was zu einem Verlust an biologischer Vielfalt und zu wirtschaftlichen Kosten führt. Aufgrund des zunehmenden globalen Handels und des Klimawandels wird erwartet, dass sich die Dynamik biologischer Invasionen in Zukunft intensivieren wird. In Deutschland nimmt die Zahl der invasiven oder potenziell invasiven Pflanzenarten zu, deren Ausbreitung erhebliche ökologische Schäden verursacht. Ziel dieser Arbeit ist die Entwicklung prädiktiver Habitatmodelle, welche sowohl klimatische und andere abiotische Faktoren als auch Habitattypen als Umweltvariablen integrieren. Die Habitattypen wurden aus einer fernerkundlichen Klassifikation des Zielgebiets unter Verwendung von MODIS-Oberflächenreflexionsdaten und einem Ensemble von drei Machine-Learning-Algorithmen abgeleitet. Dabei wurden naturnahe Gebiete anhand ihrer spektralen Ähnlichkeit mit Natura-2000-Lebensraumtypen einer von 18 Klassen zugeordnet. Die Klassifizierung ermöglichte es, quantitative Informationen über die räumliche Verteilung von Lebensräumen zu gewinnen und zwischen Störungsereignissen und graduellen Verschiebungen der Habitatzusammensetzung zu unterscheiden. Im Anschluss wurden Artverbreitungsmodelle für 46 invasive Pflanzenarten entwickelt, um potenziell geeignete Lebensräume unter gegenwärtigen und zukünftigen klimatischen Bedingungen mithilfe zweier Machine-Learning-Algorithmen zu ermitteln. Als Prädiktorvariablen wurden insgesamt 18 Umweltfaktoren verwendet, darunter Bodentyp, Höhe, Landnutzung, Habitattyp, Verkehrsinfrastruktur, Temperatur und Niederschlag. Die Modelle legen nahe, dass die Mehrheit der Arten ihren potenziell geeigneten Lebensraum noch nicht besetzt hat. Unter zukünftigen Klimabedingungen ist für die meisten Arten eine Zunahme der Habitateignung zu erwarten. Dabei üben Klimafaktoren, Bodentyp und Verkehrsinfrastruktur den größten relativen Einfluss auf die Artverbreitung aus. Der Habitattyp ist lediglich für eine geringe Zahl von Arten von Bedeutung, was darauf hindeutet, dass es nur begrenzt möglich ist, interspezifische Konkurrenz oder nicht näher spezifizierte biotische Interaktionen in diesem Maßstab zu berücksichtigen. Monitoring-Systeme stellen das kosteneffizienteste Mittel zur Verhinderung der Ausbreitung invasiver Arten dar und sind somit ein entscheidendes Element für deren Management. Auf Basis der Ergebnisse dieser Arbeit wurde eine öffentlich zugängliche Monitoring-Website entwickelt, IPS Monitor, welche digitale Webkarten sowie Pflanzensteckbriefe beinhaltet. / Invasive plant species, characterised by high reproductive capacity and broad environmental tolerance, often outcompete native flora, leading to biodiversity loss and economic costs. Due to increasing global trade and climate change, the dynamics of biological invasions are expected to increase in the future. In Germany, the number of invasive or potentially invasive plant species is increasing, causing significant damage due to their aggressive spread and ecological threats. This thesis aims to develop predictive habitat models that integrate climatic and other abiotic factors as well as habitat types as environmental variables. Habitat types were derived from a remote sensing classification of the target area using MODIS surface reflectance data and an ensemble of three machine learning algorithms, assigning natural areas to one of 18 classes based on their similarity to Natura 2000 habitat types. The classification framework was able to provide quantitative information on the spatial distribution of habitats and differentiate between disturbance events and gradual shifts in ecosystem composition. Large-scale species distribution models of 46 invasive plant species were then developed to identify the potentially suitable habitat under present and future climatic conditions using two machine learning techniques. A total of 18 environmental variables were used as predictor variables, including soil type, altitude, land use, habitat type, transport infrastructure, temperature and precipitation. The models indicate that the majority of species have not yet occupied their potentially suitable habitat. An increase in habitat suitability under predicted climatic conditions is implied for most species, with climate factors, soil type and transport infrastructure having the greatest relative influence on habitat suitability. Habitat type is only relevant for few species, indicating a limited ability to map interspecific competition or unspecified biotic interactions at this spatial scale. As the most cost-effective means of preventing the spread of invasive species, monitoring systems represent a crucial element in their management and enable early detection and rapid response mechanisms. Therefore, a publicly accessible monitoring tool, IPS Monitor, including digital web maps and plant fact sheets has been developed from the results of this thesis.

Les écosystèmes herbacés méditerranéens, caractérisés par une importante biodiversité, ont subi de considérables changements d‟usage. Désormais, leur conservation est devenue insuffisante au regard de l‟augmentation des dommages causés par les activités humaines. La restauration écologique apparaît donc comme un outil approprié pour participer à leur préservation. Des recherches préalables sur les différents compartiments de l‟écosystème ainsi que sur les facteurs responsables de l‟assemblage de leurs communautés avant et après dégradations sont donc nécessaires afin de mettre en place des méthodes de restauration adaptées à ces écosystèmes. Ainsi, en utilisant comme modèle biologique les Coussouls de Crau et leurs friches post-culturales (Bouches-du-Rhône, France), représentatif de nombreux écosystèmes steppiques méditerranéens, nous avons choisi de déterminer et d‟étudier les principaux filtres potentiellement responsables de l‟organisation de cette communauté végétale. Le pâturage ovin, les changements trophiques du sol, les phénomènes de compétition et la capacité de reproduction et/ou de dispersion des espèces, identifiés lors d‟une première étude sur la régénération de la steppe, ont ainsi été étudiés dans trois expérimentations différentes. Deux protocoles de restauration écologique in situ (transfert de foins et semis d‟espèces structurantes) et un protocole d‟expérimentation ex-situ testant les interactions d‟une sélection d‟espèces de la steppe ont permis de réaliser ces recherches. Nos principaux résultats montrent que les filtres de reproduction/dispersion, le niveau trophique du sol, la compétition et le régime de perturbations récurrentes lié au pâturage ovin ont un rôle déterminant dans les changements de la composition et de la structure de la communauté et ils expliquent ainsi en partie le ralentissement de sa dynamique successionnelle vers la steppe de référence. Nous avons également pu démontrer que ces filtres interagissaient entre eux. Au niveau de la recherche appliquée, les protocoles testés favorisent le retour de la végétation steppique, néanmoins la composition des parcelles restaurées reste toujours très différente de l‟écosystème de référence à très court terme (deux à trois années après la restauration). Cela démontre que même si nous comprenons mieux aujourd‟hui les facteurs expliquant l‟organisation de cette communauté, il est cependant toujours difficile de la restaurer dans son intégralité car il n‟est pas aisé de manipuler et de trouver un équilibre entre l‟action de ces différents facteurs. Il est donc désormais plus que nécessaire de poursuivre ces recherches fondamentales et appliquées notamment au niveau des processus de maturation et de structuration des vieilles communautés végétales herbacées. / Mediterranean herbaceous ecosystems which are characterized by a high biodiversity have been submitted to a lot of changes in use. Their conservation is not sufficient enough and ecological restoration seems to be an adapted solution to improve conservation efforts as it can mitigate damages induced by human activities. To develop restoration methods adapted to these ecosystems, preliminary researches on the different communities composing an ecosystem and the filters which are responsible for community assemblage before and after disturbance are necessary. Representative of numerous Mediterranean steppe ecosystems, the “Coussouls de Crau” and their ex-arable-fields (Bouches-du-Rhône, France) are the biological models used to identify and study the principal filters potentially responsible for organizing the plant communities. Sheep grazing, trophic changes, competition and reproduction and /or species dispersal, were identified in a first study on steppe regeneration; these filters were then the core of the following three research experiments. We carried out two in-situ restoration protocols (hay transfer and sowing foundation species) and one ex-situ experiment testing interactions between a selection of steppe species. The main results show that reproduction, seed dispersal, soil trophic level, competition, extensive sheep grazing are filters which have a determinant role in structuring the communities, in determining plant composition and partly in explaining the slow dynamics towards the reference steppe. Also, we show that filters interact between them. For applied restoration, the tested methods promote steppe vegetation come back, but in the short term (two or three years after restoration), the composition of restored areas remains different to the reference ecosystem. Even if we understand better the different factors which explain community organization, these results demonstrate that it is difficult to restore it integrally because it is not easy to manipulate and find an equilibrium between the different filters actions. Now it is necessary to continue these fundamental and applied researches, in particular on the maturation and structure of the old herbaceous plant communities.

Many regional and local factors can influence the distribution of native and exotic species in ecological communities. I examined the regional- and local-scale determinants of native and exotic vascular plant species richness and composition in a highly fragmented oak savanna ecosystem on southeastern Vancouver Island. In sharp contrast to most reported results, I found a negative relationship between native and exotic richness at the regional scale, and no relationship at the local scale. Two extrinsic factors, surrounding road density and climate, best explained the regional-scale relationship by each affecting natives and exotics in opposite ways. Road density and climate were also the dominant predictors of native and exotic composition at the regional scale. Patterns in the patch occupancy of individual species confirmed the importance of these factors but I found that low surrounding road densities and cool, wet conditions predicted the presence of many natives and the absence of many exotics. Environmental factors explained variation in richness and composition at the local scale, but these factors were different for natives and exotics. My results suggest that natives and exotics respond to roads and climate in fundamentally different ways. Roads increase both exotic propagule pressure and disturbance, which may facilitate exotic invasion. In contrast, disturbance from roads may increase the likelihood of local extinction for particular natives. Differing climatic preferences within the native and exotic species pools may also partially explain the observed patterns. There was no evidence that native diversity directly affects exotic diversity (or vice versa). Surprisingly, I found that connectivity was not an important predictor of richness or composition despite the high degree of habitat fragmentation in this ecosystem.

Over the last 3 decades, freshwater aquaculture has become one of the most important food industries. However the constant introduction of a reduced number of very successful species for aquaculture has been identified as one of the main activities related to the alarming decline of fish biodiversity worldwide. This issue has raised awareness amongst the scientific community, governmental authorities and the general public towards freshwater fish biodiversity. This new awareness has promoted the development of “green” markets and environmentally friendly strategies, aiming for a reliable production of protein sources. The development of native species aquaculture has been presented as a strong alternative for sustainable aquaculture and the protection of biodiversity. However, it seems clear that unplanned native species aquaculture developments can be as detrimental on local biodiversity as the introduction of exotic fish, if not more dangerous. Therefore, the advantages and disadvantages of native species aquaculture have to be clearly analysed before any aquaculture development. This study aimed to establish a philosophical background regarding the use of native fish species in aquaculture in contrast to the introduction of exotic species that may compete for a similar niche as food in local markets. The main ecological impacts that exotic fish species may have on natives, such as competition, predation, and hybridization were discussed. In addition, a well planned native species Aquaculture Strategy for the Protection of Biodiversity was produced, at catchment level, within a Geographic Information System (GIS). For the development of the native species aquaculture strategy in central Mexico, four species of Atherinids (Chirostoma estor, C. Jordani, C. promelas and Atherinella balsana) and two species of native Ictalurids (Ictalurus balsanus and Ictalurus dugesii) were included in this study. These six species are relatively new to aquaculture and they were selected on the basis of their importance in local fisheries and markets in their native basins of the Lerma-Santiago and Balsas rivers. Both of these basins are of great importance in central Mexico, not only because of their biodiversity but also because of their high human population densities and socio-economic status. The use of Geographic Information Systems was a fundamental factor in the development of the native species aquaculture strategy at catchment level, consisting of site suitability models (SSM) for each species in their corresponding native catchments. Overall, SSM identified 13,916 km2 and 11,178 km2 highly suitable for aquaculture of the studied Atherinids and Ictalurids respectively, based on Water, Soil and Terrain, Infrastructure and Risk sub-models. A set of predictive species distribution models (PSDM), which related ecological characteristics for each studied species with relevant environmental and topographic parameters into a GIS, were also produced. Such models were developed for the establishment of potential natural ranges of distribution for each species, as well as their potential to become exotic in new environments, as a potential for invasion model (PI). Based on a partial verification, both PSDM and PI models produced results that were satisfactorily consistent with the known distribution of each modelled species. The combination of SSM and PSDM produced an Aquaculture Strategy for the Protection of Biodiversity model (ASPB) which identified the most environmentally friendly suitable areas for aquaculture sites. In contrast, the combination of the SSM with PI models into an ASPB model identified the site suitability potential for non-native species that are genetically close to native ones, in an attempt to reduce the known impacts that exotic species have on local biodiversity. In this way the ASPB model identified 7,651 km2 suitable for aquaculture of I. balsanus in its native Balsas basin and 15,633 km¬2 suitable for aquaculture of the non-native I. dugesii. ASPB models were produced for all the studied species. The final results were used to produce a set of guidelines for the development of sustainable aquaculture of native species at catchment level that cover genetic and ecological implications, as well as a well planned decision making tool produced in a GIS.