Faktory ovlivňující invazivnost v rodě Impatiens (netýkavka): interakce vlastností druhů, kompetice a podmínek prostředí

Cílem předkládané disertační práce bylo určit, které faktory ovlivňují invazivnost v rodě Impa- tiens (netýkavka). Netýkavky jsou velmi atraktivní rostliny; některé zdomácněly mimo původní areál výskytu, zatímco jiné ne, přestože byly často pěstovány. Pokud pátráme po vlastnostech, které podporují invazivnost, je výhodné srovnávat druhy jednoho rodu, tzv. kongenery. Díky blízké příbuznosti jsou jejich vlastnosti a způsob rozšiřování méně ovlivněny fylogenezí, než při srovnání nepříbuzných druhů či dokonce celých flór. Srovnání kongenerů umožňuje přesnější určení vlastností, které invazní druhy zvýhodňují oproti druhům domácím, a zároveň přesnější rozpoznání druhů s invazním potenciálem. Intenzita kompetice mezi původními a in- vazními druhy závisí na míře překryvu jejich nik. Invazní druhy jsou obvykle vysoce kompeti- tivní v širokém rozsahu podmínek prostředí, zatímco domácí druhy často mají užší ekologické optimum. Výsledek kompetice se navíc může v různých fázích životního cyklu lišit a závisí na míře dominance (vyjádřené např. pokryvností), což bývá zřídka zohledněno. Rozšíření invaz- ního druhu v nepůvodním areálu také ovlivňují místní podmínky prostředí, způsoby a rychlost šíření. Mnoho invazních druhů proto zdomácnělo podél vodotečí, které poskytují celou řadu příhodných mikrostanovišť, na nichž je...The aim of this thesis was to identify factors that contribute to invasiveness of species in the genus Impatiens. This genus is horticulturally attractive and includes several species that are known to have naturalized outside their native ranges, while others did not escape, in spite of being frequently cultivated. When looking for traits associated with invasiveness, it is useful to focus on congeneric species. Their traits and dispersal modes are less influenced by phylogeny, than when comparing unrelated species or even complete floras. This helps to account for traits that favour invasive species over native ones and thus identify potential invaders more precisely. A superior invader performance is attributed to a competitive advantage over native species that can lead in extreme case to competitive exclusion of the latter. Invasive and native species com- pete only if their niches overlap and the strength of competition depends on niche similarity. Importantly, invasive species are considered to be able to maintain their high competitiveness over a wide range of environmental conditions, while native ones often have narrower environ- mental optima. Lastly, competitive outcome can vary over life stages and depends on the degree of species dominance, which is rarely taken into account. Spread and...Katedra ekologieDepartment of EcologyPřírodovědecká fakultaFaculty of Scienc

Low-temperature magnetism of alabandite : Crucial role of surface oxidation

Manganese(II) monosulphide crystallizes into three different polymorphs (alpha-, beta-, and gamma-MnS). Out of these, alpha-MnS, also known as mineral alabandite, is considered the most stable and is widespread in terrestrial materials as well as in extraterrestrial objects such as meteorites. In this study, a low-temperature antiferromagnetic state of alpha-MnS was investigated using macroscopic magnetic measurements as induced and remanent field-cooled (FC) and zero-field-cooled (ZFC) magnetizations and magnetic hysteresis. Both natural alabandite and synthetic samples show (i) Néel temperatures in a narrow temperature range around 153 K and (ii) a rapid increase of the magnetization around 40 K. An anomalous magnetic behavior taking place at about 40 K was previously ascribed to the magnetic transition from a high-temperature antiferromagnetic to a low-temperature ferromagnetic state documented for non-stoichiometric alpha-MnS slightly enriched in manganese. However, our detailed microscopic observations and, in particular, oxidation experiments indicate that the anomalous magnetic behavior around 40 K is caused by a presence of oxide layer of ferrimagnetic hausmannite (Mn3O4) on the surface of alpha-MnS rather than being an intrinsic property of nearly stoichiometric alpha-MnS.Peer reviewe

Úlohy a účast v FO v minulém desetiletí

Cílem příspěvku je shrnout výstupy několika diplomových a bakalářských prací, jež se v posledních letech věnovaly vlastnostem úloh zadávaných v posledních přibližně deseti ročnících Fyzikální olympiády (FO) a také účasti v okresních a krajských kolech některých kategorií soutěže. Účast v celostátních kolech je pak znázorněna ve vztahu ke geografickým údajům systému GIS.The aim of the paper is to summarize the results of several master and bachelor theses that have been devoted in recent years to the characteristics of the problems given in the last ten or so years of the Physics Olympiad (FO), as well as to the participation in the district and regional rounds of some categories of the competition. The participation in the national rounds is then illustrated in relation to GIS geographic data

Distinguishing between Shock-darkening and Space-weathering Trends in Ordinary Chondrite Reflectance Spectra

Peer reviewe

Density, porosity, mineralogy, and internal structure of cosmic dust and alteration of its properties during high velocity atmospheric entry

X-ray microtomography (XMT), X-ray diffraction (XRD) and magnetic hysteresis measurements were used to determine micrometeorite internal structure, mineralogy, crystallography, and physical properties at ~μm resolution. The study samples include unmelted, partially melted (scoriaceous) and completely melted (cosmic spherules) micrometeorites. This variety not only allows comparison of the mineralogy and porosity of these three micrometeorite types, but also reveals changes in meteoroid properties during atmospheric entry at various velocities. At low entry velocities, meteoroids do not melt, and their physical properties do not change. The porosity of unmelted micrometeorites varies considerably (0-12%) with one friable example having porosity around 50%. At higher velocities, the range of meteoroid porosity narrows, but average porosity increases (to 16-27%) due to volatile evaporation and partial melting (scoriaceous phase). Metal distribution seems to be mostly unaffected at this stage. At even higher entry velocities, complete melting follows the scoriaceous phase. Complete melting is accompanied by metal oxidation and redistribution, loss of porosity (1 ± 1%), and narrowing of the bulk (3.2 ± 0.5 g/cm3) and grain (3.3 ± 0.5 g/cm3) density range. Melted cosmic spherules with a barred olivine structure show an oriented crystallographic structure, whereas other subtypes do not.Peer reviewe

Factors associated with invasiveness in the genus Impatiens: interaction of species traits, competition and environment

The aim of this thesis was to identify factors that contribute to invasiveness of species in the genus Impatiens. This genus is horticulturally attractive and includes several species that are known to have naturalized outside their native ranges, while others did not escape, in spite of being frequently cultivated. When looking for traits associated with invasiveness, it is useful to focus on congeneric species. Their traits and dispersal modes are less influenced by phylogeny, than when comparing unrelated species or even complete floras. This helps to account for traits that favour invasive species over native ones and thus identify potential invaders more precisely. A superior invader performance is attributed to a competitive advantage over native species that can lead in extreme case to competitive exclusion of the latter. Invasive and native species com- pete only if their niches overlap and the strength of competition depends on niche similarity. Importantly, invasive species are considered to be able to maintain their high competitiveness over a wide range of environmental conditions, while native ones often have narrower environ- mental optima. Lastly, competitive outcome can vary over life stages and depends on the degree of species dominance, which is rarely taken into account. Spread and..

Habitat requirements and competition between native and invasive Impatiens species

Three of Impatiens species are widespread in the Czech republic, one is native, two of them invasive. Because all species occur in relatively similar habitats, the question is, whether the invasive species can negatively affect the native species, or even the original can can be displaced. The aim of the thesis was: (i) to compare habitat requirments of the Impatiens species, (ii) to determine if the coexistence of species is possible, (iii) to assess the impact of invasive species to the original species. The investigation was carried out using two sets of permanent plots in 5 localities. In the first set with a total of 84 plots (combinations of occurrence of the three species) site characteristics as tree cover, soil humidity, slope and bare land cover were directly measured and nutrient, light, humidity and soil reaction characteristic assessed using Ellenberg indicator values. The second set contained a total of 45 plots with one of the native-invasive congener pair being removed and the intact controls. Number, cover and height of the plants were assesed. The key enviromental factors determining distribution of the species were soil moisture for I. noli-tangere and I. parviflora, and tree cover for I. glandulifera and I. parviflora. Ellenberg indicator values had poor explanation value;..

Application of fluidized layer of granular material in water treatment

Chemical treatment is the most often method used in water treatment in the Czech republic. It is based on dosage of destabilisation reagent into raw water, formation of separable aggregates and their separation by sand filtration. Waterworks optimalisation is predominantly carried out by change of the chemical parameters, typically by change of destabilisation reagent dose. Physical parameters in water treatment like the magnitude of the velocity gradient and period of its duration are undervalued commonly, although they have crucial effect on quality of the aggregates. Character of the aggregates (size, density, compactness) influence their separability. This study aims at evaluation of influence of the magnitude of the velocity gradient on quality of suspension formed. Infuence of stirring intensity was performed on the pilot plant situated in the Želivka waterworks, which is fed from Švihov reservoir. The pilot plant worked at two modes: 1) slow stirring by perforated baffles and 2) fast stirring by fluidised layer of granular material. Fast stirring was either aggregational (served only as stirring element), or separational (separation of aggregates proceed already in the fluidised layer) Infuence of the magnitude of velocity gradient was evaluated by aggregation test. Seperation effectivity..

Characteristics of selected Impatiens species important for their dynamics in the field

Ústav pro životní prostředíInstitute for Environmental StudiesFaculty of SciencePřírodovědecká fakult

Application of fluidized layer of granular material in water treatment

Chemical treatment is the most often method used in water treatment in the Czech republic. It is based on dosage of destabilisation reagent into raw water, formation of separable aggregates and their separation by sand filtration. Waterworks optimalisation is predominantly carried out by change of the chemical parameters, typically by change of destabilisation reagent dose. Physical parameters in water treatment like the magnitude of the velocity gradient and period of its duration are undervalued commonly, although they have crucial effect on quality of the aggregates. Character of the aggregates (size, density, compactness) influence their separability. This study aims at evaluation of influence of the magnitude of the velocity gradient on quality of suspension formed. Infuence of stirring intensity was performed on the pilot plant situated in the Želivka waterworks, which is fed from Švihov reservoir. The pilot plant worked at two modes: 1) slow stirring by perforated baffles and 2) fast stirring by fluidised layer of granular material. Fast stirring was either aggregational (served only as stirring element), or separational (separation of aggregates proceed already in the fluidised layer) Infuence of the magnitude of velocity gradient was evaluated by aggregation test. Seperation effectivity..