Global ETD Search

1	How former arable fields with permanent grazing differ from managed semi-natural pastures in Sweden Galin, Isolde January 2019 (has links) New farming needs and innovations have, over time, led to changes in land use. Arable fields have been turned into pastures and semi-natural pastures into arable fields. Due to the ecological value of continually grazed semi-natural pastures in Sweden the aim of this study is to find out how former arable fields that are permanently grazed differ from semi-natural pastures. In this study I selected appropriate semi-natural pastures from a national monitoring program on seminatural- pastures and meadows. Plots continuously grazed were compared with grazed plots on former arable fields. Pair-wise differences in the Ellenberg indicator values Light (L), Soil moisture (F), soil pH (R) and soil nitrogen (N), vertical coverage of trees, bushes and vegetation, species richness and species composition were tested. Except for species composition there were only small differences between former arable fields that are permanently grazed and semi-natural pastures. That means former arable fields can with time and grazing gain many of the values continuously grazed semi-natural pastures have. grasslands former arable fields species richness species composition semi-natural pastures Ellenberg indicator values Ecology Ekologi
2	Biologie a stanovištní nároky ohroženého druhu stepníka Eresus moravicus (Araneae: Eresidae)v Česku / Biology and habitat requirements of endangered ladybird spider Eresus moravicus (Araneae: Eresidae) in Czechia KREJČÍ, Tomáš January 2012 (has links) The ladybird spider Eresus moravicus is one of our most endangered spiders. It is therefore necessary to know its habitat requirements and have at least basic knowledge of its biology to design an appropriate management to protect sites of its natural occurrence. Phytocenological analysis was made at each site and the outcomes were evaluated based on the Ellenberg´s indicator values. Also slope and exposure, litter layer and the quantity of rubbel were measured on the localities. Individuals were taken from burrows for the measurement of the prosoma length (investigation of the length of the life cycle). Exuviae were collected from the same burrows for measurement of the prosoma length. From these data the number of instars was determined. Prey remains were taken at most of those sites from 5?10 burrows and determined. Offsprings from several maternal burrows were taken, counted and weighted (research of fecundity of females). Weight of offsprings is important also in terms of their dispersion ability. The offsprings ability to balloon was investigated experimentally in laboratory conditions. The ladybird spider Eresus moravicus occurs in warm regions with high intensity of irradiation, mostly on the southern and southwestern slopes. Sites are characterized by poor herbaceous vegetation without trees and shrubs and by a thin layer of humus. Female lives for four years and the male for three years. The number of instars can reach to 13. Beetles (Coleoptera) are the most importent prey, the importent component of food are ants (Formicidae), too. Eresus moravicus has more offsprings than Eresus sandaliatus and Eresus kollari, more eggs in the cocoon than E. kollari and heavier offsprings than E. kollari and E. sandaliatus. In offsprings of E. moravicus and E. kollari pre-ballooning behavior of two types was observed: "tip-toe" behavior and "drop and swing" behavior.
3	Změny vegetace vlhkých luk ve Slavkovském lese / Vegetation changes of wet meadows in Slavkovský les Šimák, Martin January 2018 (has links) This thesis focuses on the changes of vegetation of the wet meadows in Slavkovský Les during past decade. It uses data on vegetation gained from 100 permanent plots. By the analysis of the species composition and diversity it aims to elucidate the changes of the wet meadows over the last ten years. It aims to define, which are declining and which are becoming more common. Applied management should have a great impact on the observed vegetation changes so its effect is studied in the thesis as well. The knowledge of the suitable management should lead to conservation of the local biodiversity. The abiotic environmental factors are important as well as they can influence the species composition. These factors were studied by the application of Ellenberg indicator values on the species present in the study. These changes were compared in time and in a combination of time with a management type. Thus, we should be able to say how the environment has changed in the past decade and whether the type of management has any effect on the changes. Furthermore, the thesis explores whether changes in species composition over time may be explained by species traits. The results indicate that the species diversity and composition have indeed changed during the past decade. Apparently, the higher amount of...
4	Vegetational and landscape level responses to water level fluctuations in Finnish, mid-boreal aapa mire – aro wetland environments Laitinen, J. (Jarmo) 09 September 2008 (has links) Abstract Gradient, which is largely considered to be related to water level in mires, is referred to as a microtopographic mud bottom to carpet to lawn to hummock level gradient or the hummock level to intermediate level (lawn) to flark level gradient. The relationship of this vegetation gradient to various physical water level characteristics was studied. The general classification used in the present summary paper divides the aro vegetation of the inland of Northern Ostrobothnia into two main groups: (a) treeless fen aro vegetation (Juncus supinus, Carex lasiocarpa, Rhynchospora fusca, Molinia caerulea) and (b) heath aro vegetation (Polytrichum commune). The first group (a) was divided into fen aro wetlands with an approximately10 cm peaty layer at most and into aro fens with a peat layer thicker than 10 cm. The treatment of the water level gradient was divided into three main groups. (1) The mean water level correlated with mire surface levels (microtopographic gradient) within mires with slight water level fluctuations and partly within mires with considerable water level fluctuations. (2) Three habitat groups could be distinguished on the basis of the range of water level fluctuation i.e. mires with slight water level fluctuations, mires with considerable water level fluctuations and the aro vegetation with extreme water level fluctuations. (3) The timing of water level fluctuations indicated that there are different types of patterns within aro wetlands, the seasonal pattern being mainly a response to yearly snow melt and the several-year-fluctuation pattern being related to the regional groundwater table fluctuation in mineral soils (heath forests). A link was suggested between the stability of the water regime and peat production in local aapa mire – aro wetland environments. From the point of view of peatland plants the direction of variation from a stable to an unstable water regime in aapa mire – aro wetland environments represents a transition towards more and more harsh ecological conditions, partly forming a gradient through natural disturbance. A qualitative functional model was provided for the mire – aro wetland systems of Northern Ostrobothnia. The model supposes differences in the characteristics of peat between two functional complexes within a mire system. Finally, the model for local mire – aro wetland systems was converted to a general from: diplotelmic (acrotelm) mires were divided into two subtypes (diplotelmic water stabilization mires, diplotelmic water fluctuation mires) and the relationship of those subtypes to percolation mires and seasonal wetlands was considered. Ellenberg indicator values diplotelmic model ecological gradients hydrogenetic mire types mire vegetation peat procuction seasonal wetlands wetland hydrology wetland vegetation classification
5	Investigations in weed biology: studies at the plant, population, and community levels Sosnoskie, Lynn Marie 05 January 2005 (has links) No description available. Agriculture, Agronomy Alliaria petiolata Abutilon theophrasti population biology morphological variation phenological variation genetic variation weeds weed seedbanks community composition diversity glyphosate CDA Indicator values MRPP
6	Adventivní odnožování krátkověkých rostlin v přírodních populacích / Adventitious sprouting of short-lived plants in natural populations MALÍKOVÁ, Lenka January 2011 (has links) Disturbance is one of most important selective factor causing removal of plant biomass. Man-made habitats are characterized by strong and unpredictable disturbances, providing bare soil surface colonized by plants with short life cycle. Populations of the short-lived plants are, however, vulnerable to the strong disturbance removing all stem parts with reserve axillary meristems in the case it occurs before plant flowering and fruiting. Nevertheless, 2 % of annual and 14 % of biennial plants are able to overcome meristem limitation by adventititous sprouting from hypocotyle or/and roots. This thesis is composed of four original studies describing the occurrence of adventitious sprouting in natural populations of 22 monocarpic weeds of Central Europe and one species in Indonesia. The studied phenomenon was analyzed in relation to various environmental factors and plant traits in the field and in experimental conditions.
7	Vegetation succession in old fields at broad landscape scales / Vegetation succession in old fields at broad landscape scales JÍROVÁ, Alena January 2012 (has links) This thesis is focused on succession in old fields in Central Europe. Repeated sampling, analysis of surrounding vegetation and soil measurements were conducted in the Bohemian Karst Landscape protected area. Samples from the Doupovské hory Mountains and the rest of the Czech Republic were added to discover basic principles of old field succession at the larger scale of landscapes.
8	Pression d'herbivorie et dynamique des communautés végétales : influence à court et moyen termes des populations de cervidés sur la diversité des communautés végétales en forêt / Herbivory pressure and vegetation community dynamics : short- and mid-term impacts of deer populations on the diversity of forest vegetation communities Boulanger, Vincent 27 April 2010 (has links) Les cervidés, animaux mobiles et herbivores, peuvent influencer les distributions, assemblages et dynamiques d'espèces végétales. L'objectif de cette thèse est d'évaluer le rôle joué par les cervidés sur la composition, stratification et dynamique de la végétation forestière. Le ré-échantillonnage de relevés couplant composition et abroutissement de la flore, implantés en 1976 en Forêt d'Arc-en-Barrois (52) a permis d'identifier (i) des espèces ligneuses préférées (Cornus sp., Rosa arvensis) ou au contraire évitées par les cervidés qui sélectionnent les espèces arbustives et à bois dense et (ii) le niveau trophique et la pression d'abroutissement comme gradients structurant la végétation et déterminant les dynamiques des espèces et des communautés. Nous analysons plus précisément le rôle des cervidés dans la progression spectaculaire de Cynoglossum germanicum, espèce rare, épizoochore et toxique.A partir d'un réseau national d'enclos/exclos suivis sur 10 ans, nous montrons que les cervidés limitent la croissance des arbustes et des espèces compétitrices, ce qui profite à la richesse spécifique de la strate herbacée. La valeur écologique et patrimoniale des espèces en progression est discutée. A l'aide de données de chasse, nous tentons d'isoler les rôles des différentes espèces d'ongulés dans ces dynamiques.Ces résultats exposent la complexité et la diversité des effets des cervidés sur la végétation forestière. Enfin, ce travail met l'accent sur la nécessité des suivis temporels intégrant toutes les composantes de l'écosystème forestier pour mieux appréhender les changements en cours. / This thesis aims at assessing the impacts of deer on forest vegetation composition, stratification and dynamics.We resampled a network of relevés coupling vegetation and browsing surveys, settled in 1976 in the national forest of Arc-en-Barrois. We identified (i) ligneous species that are either preferred (Cornus sp., Rosa arvensis) or avoided by deer, which tend to select shrubs species with dense wood and (ii) trophic level and browsing pressure as gradients that determine plant communities structures and dynamics. Then, we highlight the roles of deer in the spectacular expansion of Cynoglossum germanicum, a rare, epizoochorous and toxic species. According to a national network of exclosures, monitored for over 10 years, we show that deer limit shrubs and competing species growth, which in turn benefits to the herbaceous species richness probably through an increased light availability. Ecological and patrimonial value of the benefitting species is discussed. Using hunting statistics, we try to isolate the role of the various ungulate species in these dynamics.These results provide evidence for the diversity and complexity of deer impacts on forest vegetation. Finally, we demonstrate the need for long term monitoring programs, including all the forest ecosystem components so that we could better appreciate the forces driving the current changes Forêt Végétation Herbivorie Cerf Chevreuil Ongulés Changements Communautés végétales Espèces ligneuses Étude diachronique Suivi à long terme Ré-échantillonnage Flore Gestion forestière Abroutissement Sélectivité Épizoochorie Perturbations Enclos/exclos Réseau Rénécofor Arc-en-Barrois Plan de chasse Traits de vie Valeurs indicatrices Forest Vegetation Herbivory Red deer Roe deer Ungulates Shifts Vegetation communities Woody species Diachronic study Long-term monitoring Resampling Ground ﬂora Forest management Browsing pressure Selectivity Epizoochory Disturbance Intermediate disturbance hypothesis Enclosure Network Rénécofor Arc-en-Barrois Hunting statistics Plant traits Indicator values

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