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The influence of forest management on occurence of microhabitats that are important for forest biodiversity
Heřmánková, Valentýna ; Hofmeister, Jan (advisor) ; Kozák, Daniel (referee)
A large part of the declining forest biodiversity (saproxylic insects, birds, fungi, bryophytes, lichens etc.) is linked to microhabitats that occur on structures typical of old-growth forests and are relatively rare in managed forests. In recent decades, alternative, more close-to- nature management practices have been slowly gaining ground, but their impact on microhabitats, and thus their potential value for forest biodiversity, has not yet been assessed. Therefore, I made a comparison of the occurrence and quality of microhabitats in 4 forest plots (8,3 to 42,5 ha) representing different forest management methods (traditional clearcutting management, alternative selective management and forest reservation at the time of data collection 65 years without intervention) in the natural conditions of the Central Bohemia. In the plots, using the adopted methodologies, I conducted an inventory of the presence of microhabitats on living trees and an inventory of deadwood and their assessment. The highest abundance and quality of microhabitats and deadwood were in the nature reserve, which at the same time completely exhausted the gamma diversity of all plots studied. The occurrence of microhabitats in clearcut and selective management forests was comparable and mostly low. The positive factors...
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Adaptations of orchid roots to epiphytism
Ungrová, Anna ; Ponert, Jan (advisor) ; Soukup, Aleš (referee)
The evolutionary success of orchids is to a large extent driven by the ability to colonize epiphytic habitats. This ability is based on a number of adaptations at different levels, and the adaptive features of aerial roots can play a key role because the roots are practically the only organ providing water and nutrient uptake. The main aim of this work is to review available information about roots of epiphytic orchids (Orchidaceae), especially their adaptations to the epiphytic way of life. The roots of epiphytes must deal with a periodic lack of water and nutrients, often in conjunction with high irradiation. The roots of epiphytic orchids adapt to these conditions on many levels. Rhizodermis forms a velamen capable to retain water and nutrients and protecting roots against environmental conditions including UV radiation. Root cortex contains chloroplasts, which can perform photosynthesis at least in some orchid species. Exodermis is well differentiated with thick secondary cell walls and acts as a selective barrier for the transport of substances with the use of passage and aeration cells. The function of some adaptive structures is still unclear, for example, tilosomes could regulate transpiration. Epiphytism evolved multiple times in orchids, and some root adaptations therefore originated...
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Adaptations of orchid roots to epiphytism
Ungrová, Anna ; Ponert, Jan (advisor) ; Soukup, Aleš (referee)
The evolutionary success of orchids is to a large extent driven by the ability to colonize epiphytic habitats. This ability is based on a number of adaptations at different levels, and the adaptive features of aerial roots can play a key role because the roots are practically the only organ providing water and nutrient uptake. The main aim of this work is to review available information about roots of epiphytic orchids (Orchidaceae), especially their adaptations to the epiphytic way of life. The roots of epiphytes must deal with a periodic lack of water and nutrients, often in conjunction with high irradiation. The roots of epiphytic orchids adapt to these conditions on many levels. Rhizodermis forms a velamen capable to retain water and nutrients and protecting roots against environmental conditions including UV radiation. Root cortex contains chloroplasts, which can perform photosynthesis at least in some orchid species. Exodermis is well differentiated with thick secondary cell walls and acts as a selective barrier for the transport of substances with the use of passage and aeration cells. The function of some adaptive structures is still unclear, for example, tilosomes could regulate transpiration. Epiphytism evolved multiple times in orchids, and some root adaptations therefore originated...
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Comparison of ecological requierements of the epiphytic species within Orthotrichaceae family
Franková, Hana ; Plášek, Vítězslav (advisor) ; Hejda, Martin (referee) ; Marková, Ivana (referee)
The thesis is a part of an ongoing research on taxonomy, ecology, and the distribution of epiphytic bryophytes particularly within the Orthotrichaceae family, based on collected bryofloristic records. The database now contains 6500 records. I have analysed interspecific differences in habitat preferences between species, namely their associations with particular phorophytes, pH of phorophyte bark, altitude, and the position on the phorophyte. Individual species differed in their occurrence according to altitude, phorophyte, and pH, though altitude was the most important factor. All analysed species have been shown to represent obligate epiphytes. Some species reveal a tendency to occur preferrentially on northern or western side of the phorophyte, but this tendency is not by any means universal. I discuss these findings in the context of the knowledge of species autecology and current changes in their distribution.
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