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  • 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.
81

Benthic macroinvertebrate and bryophyte assemblages in boreal springs: diversity, spatial patterns and conservation

Ilmonen, J. (Jari) 06 April 2009 (has links)
Abstract In this thesis, I studied the patterns in the assemblage composition as well as the biogeography and ecology of spring macroinvertebrates and bryophytes in Finland. My main objectives were to assess the importance environmental variables to macroinvertebrate and bryophyte assemblage composition in springs at the level of multiple spatial scales. In addition, I assessed the importance of springs in the boreal mire landscape, and sought the ecological and environmental determinants of a key species in boreal springs. In a large-scale study, I also examined the concordance between macroinvertebrates and bryophytes across boreal ecoregions, and assessed how macroinvertebrate assemblage variation corresponds to terrestrially-based ecoregions. Locally, spring macroinvertebrate assemblage structure displays high variation between different kinds of mesohabitats within springs, highlighting the importance of careful sampling of all habitat types in spring surveys. Helocrenes and other aquatic-terrestrial ecotone habitats harbour the highest species diversity and most spring-dependent species among spring habitat types. Further, spring-influenced mire patches were shown to have distinct cranefly assemblages in the mire landscape and to harbour higher cranefly diversity than mire types with lower trophic status, emphasising the importance of springs for mire biodiversity. Regionally, a red-listed spring-dependent caddisfly species appeared to be a surrogate for a high spring conservation value, indicating high overall species diversity and the occurrence of additional red-listed species. On a large geographical scale, intersecting the boreal ecoregions, a pattern of gradual change of benthic macroinvertebrate assemblage composition from south to north was detected, largely corresponding to terrestrially-derived ecoregions. However, the physical attributes of springs also need to be taken into account in bioassessment studies. Macroinvertebrate assemblage variation also correlated with physical habitat-scale variables, but not with changes in water chemistry. In contrast, spring bryophyte assemblages showed a distinct response to variation in water chemistry, but not to variation in physical habitat characteristics. Bryophytes and insect assemblages were concordant with each other on the large geographical scale, although the concordance was rather weak. Because of their different kind of responses to the physical and chemical variables, insects and bryophytes of springs are poor surrogates for each other in boreal springs.
82

Lipidomic Analysis of Various Developmental Stages of Physcomitrium patens

Gautam, Deepshila 01 December 2021 (has links)
Lipids maintain fluidity of the cell membrane during the lifetime of all organisms. The moss Physcomitrium patens, an early land plant, enters reproductive phase under cold (15°C) conditions relative to its gametophytes (22°C). Thus, we hypothesized that their lipid content and composition would be distinct. Using ESI-MS/MS, we showed that the content and acyl composition of 11 lipid classes varied during development. Galactolipids were abundant in gametophytes but insignificant in sporophytes; among phospholipids, phosphatidylcholine was predominant in both phases. Although, sporophytes contained around five-fold less lipids than the gametophyte, their phosphatidic acid content, which accumulates during stress, was 18-fold higher. Furthermore, comparative analyses of lipidomes revealed that the 38C and 40C acyl species are abundant in the moss and mouse, which are mostly absent in vascular plants. The occurrence of long-chain, highly unsaturated lipids perhaps contribute to membrane stability that was necessary for the evolution of early land plants.
83

The Phylogeny of Land Plants: A Cladistic Analysis Based on Male Gametogenesis

Garbary, David J., Renzaglia, Karen S., Duckett, Jeffrey G. 01 September 1993 (has links)
A cladistic analysis was carried out to resolve phylogenetic pattern among bryophytes and other land plants. The analysis used 22 taxa of land plants and 90 characters relating to male gametogenesis. Coleochaete or Chara/Nitella were the outgroups in various analyses using HENNIG86, PAUP, and MacClade, and the land plant phylogeny was unchanged regardless of outgroup utilized. The most parsimonious cladograms from HENNIG86 (7 trees) have treelengths of 243 (C.I. = 0.58, R.I. = 0.82). Bryophytes are monophyletic as are hornworts, liverworts, and mosses, with hornworts identified as the sister group of a liverwort/moss assemblage. In vascular plants, lycophytes are polyphyletic and Selaginella is close to the bryophytes. Lycopodium is the sister group of the remaining vascular plants (minus Selaginella). Longer treelengths (over 250) are required to produce tree topologies in which either lycophytes are monophyletic or to reconstruct the paraphyletic bryophyte phylogeny of recent authors. This analysis challenges existing concepts of bryophyte phylogeny based on more classical data and interpretations, and provides new insight into land plant evolution.
84

Bryophyte and macrolichen diversity of the Purdiaea nutans forest in southern Ecuador and its relationship to soil, climate and vegetation structure / Bryophyte and macrolichen diversity of the Purdiaea nutans forest in southern Ecuador and its relationship to soil, climate and vegetation structure

Mandl, Nicole 31 October 2007 (has links)
No description available.
85

Mosses as mediators of climate change : implications for tree seedling establishment in the tundra

Lett, Signe January 2017 (has links)
Alpine and arctic tree line expansion depends on the establishment of tree seedlings above the current tree line, which is expected to occur with climate warming. However, tree lines often fail to respond to higher temperatures. Other environmental factors are therefore likely important for tree seedling establishment. Above the tree line, establishing seedlings encounter existing vegetation such as bryophytes, which often dominate in arctic and alpine tundra. Bryophytes modify their environment in various ways and may mediate climate change effects on establishing tree seedlings, and with that tree line expansion. The aim of this thesis was to understand if and how the environment, in particular bryophytes, mediates the impact of climate change on tree seedling establishment at the alpine and arctic tree line. This was explored by reviewing literature on tree seedling establishment at alpine and arctic tree lines globally. In addition, tree seedling survival and growth of Betula pubescens and Pinus sylvestris were assessed experimentally. Here, individuals were planted into mono-specific mats of different bryophytes species and exposed to warming and different precipitation regimes. The literature review revealed that besides from temperature, tree seedling establishment is affected by a wide range of abiotic and biotic factors including water, snow, nutrients, light, disturbance and surrounding vegetation. Furthermore the review revealed that for example vegetation can change tree seedling responses to climate change. The experiments showed that especially tree seedling survival was adversely affected by the presence of bryophytes and that the impacts of bryophytes were larger than those of the climate treatments. Seedling growth, on the other hand, was not hampered by the presence of bryophytes, which is in line with earlier findings that seedling survival, growth and seed germination do not respond similarly to changes in environmental conditions. Moreover, we found several indications that vegetation above the tree line, including bryophytes, mediated tree seedling responses to warming and precipitation or snow cover. This thesis shows that temperature alone should not be used to predict future tree seedling establishment above the alpine and arctic tree line and that extrapolations from climate envelope models could strongly over or under estimate tree line responses to warming. This underlines the value of multi-factorial studies for understanding the interplay between warming and other environmental factors and their effects on tree seedling establishment across current tree lines.
86

Mosses as mediators of climate change : implications for tree seedling establishment in the tundra

Lett, Signe January 2017 (has links)
Alpine and arctic tree line expansion depends on the establishment of tree seedlings above the current tree line, which is expected to occur with climate warming. However, tree lines often fail to respond to higher temperatures. Other environmental factors are therefore likely important for tree seedling establishment. Above the tree line, establishing seedlings encounter existing vegetation such as bryophytes, which often dominate in arctic and alpine tundra. Bryophytes modify their environment in various ways and may mediate climate change effects on establishing tree seedlings, and with that tree line expansion. The aim of this thesis was to understand if and how the environment, in particular bryophytes, mediates the impact of climate change on tree seedling establishment at the alpine and arctic tree line. This was explored by reviewing literature on tree seedling establishment at alpine and arctic tree lines globally. In addition, tree seedling survival and growth of Betula pubescens and Pinus sylvestris were assessed experimentally. Here, individuals were planted into mono-specific mats of different bryophytes species and exposed to warming and different precipitation regimes. The literature review revealed that besides from temperature, tree seedling establishment is affected by a wide range of abiotic and biotic factors including water, snow, nutrients, light, disturbance and surrounding vegetation. Furthermore the review revealed that for example vegetation can change tree seedling responses to climate change. The experiments showed that especially tree seedling survival was adversely affected by the presence of bryophytes and that the impacts of bryophytes were larger than those of the climate treatments. Seedling growth, on the other hand, was not hampered by the presence of bryophytes, which is in line with earlier findings that seedling survival, growth and seed germination do not respond similarly to changes in environmental conditions. Moreover, we found several indications that vegetation above the tree line, including bryophytes, mediated tree seedling responses to warming and precipitation or snow cover. This thesis shows that temperature alone should not be used to predict future tree seedling establishment above the alpine and arctic tree line and that extrapolations from climate envelope models could strongly over or under estimate tree line responses to warming. This underlines the value of multi-factorial studies for understanding the interplay between warming and other environmental factors and their effects on tree seedling establishment across current tree lines.
87

Studený důl jako exkurzní prostor žáků 1. stupně ZŠ / Studený důl in primary school field-instruction

Matějková, Hana January 2012 (has links)
(Abstract) My thesis explores the use of the Studeny dul site for learning purposes, namely biology and fundaments of civic and natural science, on the primary school level. My study aims at examining a field trip on the primary school level, and at attracting students' attention to the marginalized group of bryophytes. To meet these objectives, I have designed four field trips that focus on observation of transformations within natural world depending on the changes specific to the four seasons. While engaging with the natural environment, students perform practical tasks and exercises that aim at deepening of their knowledge acquired previously in the classroom. Students of a primary school in Plzen participated in field trips within a span of one school year. My primary objectives consisted of strengthening students' positive relationship with nature, and of understanding of the relationship between the human and nature.
88

Log-diversity and abundance of dead wood dependent bracket fungi and bryophytes, a comparison between spruce woodland key habitats and adjacent production forests in Östergötland, Sweden.

Lundgren Lodetti, Mathilda January 2019 (has links)
Dead wood in forests are essential habitat for a wide range of fungal, insects, lichens and bryophyte species. The main threat to dead wood dependent species is lack of substrate, which aggravates their ability to reach and colonize a new substrate. Inventories of woodland key habitats (WKHs) is a method to map forests with high biological value in Sweden, and these areas may benefit dead wood dependent species. The aim of this study was to compare spruce dominated WKHs with adjacent production spruce forests (APFs), regarding (1) log diversity, (2) log characteristics and (3) abundance of selected species on logs. The study was conducted in Östergötland County in Sweden, seven spruce WKHs (≥ 60% spruce) and seven APFs of three different types (two clear-cuts, two dominated by trees < 20 cm and three dominated by trees > 20 cm) were investigated. Data of eight wood dependent species (three bryophytes and five bracket fungi), log diversity, six log characteristics and two environmental factors were collected. In a total area of 4.27 ha, 210 logs (105 logs in WKH and APF each) were studied and the results show that there were significantly higher amount of coarse logs, distribution area of species, number of logs/ha, diameter, decay class and humidity inside WKHs compared with APFs. The total distribution area of species was approximately 85% larger in WKHs. Bark cover was slightly less in WKHs and sun exposure was significantly higher and humidity was lower in clear-cuts. According to the current study, WKHs are important for conservation of wood depending species due to the higher amount and diversity of coarse dead wood. Furthermore, it is necessary to put aside larger amount of coarse dead wood inside production forests, together with changed logging techniques to increase the suitable substrate for dead wood dependent species.
89

Biologie, ekologie a charakteristiky invaze druhu Campylopus introflexus v České Republice / Biology, ecology and invasion characteristics of Campylopus introflexus in the Czech Republic

Mikulášková, Eva January 2012 (has links)
A B S T R A C T Ecological and economic impact of invasive plants to natural ecosystems is the subject of many studies; however, invasive bryophytes have been stud- ied only marginally. Campylopus introflexus (Hedw.) Brid. is one of the most strongly invasive bryophyte species in Europe. The species appears to be native in the Southern Hemisphere. In Europe, it was collected for the first time in the British Isles in 1941. The moss has expanded eastward and the first collection in the Czech Republic is dated to 1988. This thesis found that more than 70 localities were known known in the Czech Republic in 2006, and more than 100 localities became known by 2011. It has been further demonstrated that the Czech Republic was colonized repeatedly by generative spores and all populations have a unique genetic composition. Genetic variation of the populations is low, the genetic diver- sity of populations within the Czech Republic is not correlated with their geographic position or with any of the monitored environmental variables. At a fine scale within particular localities, the species disperses by vege- tative diaspores, while it uses generative spores for spreading over longer distances. In Central Europe, C. introflexus prefers open coniferous forests, especially plantations of either spruce or pine. It colonizes...
90

Biodiversity along a gradient of modification : plant invertebrates and reptile diversity in mid-altitude tall tussock (Chionochloa rigida) grasslands, eastern Central Otago, New Zealand

Dixon, Katherine Marguerite, n/a January 2005 (has links)
This thesis set out to examine the soils, plants, lichens, invertebrates and common skinks along a gradient of habitat modification. This gradient was represented by ten study sites, of varying management histories, in a mid altitude tall tussock (Chionochloa spp.) grassland in eastern Central Otago. One extreme of the gradient was represented by intact tall tussock plants with a high density of inter tussock vegetation. The other extreme was represented by intensively managed exotic pasture. Native plants, invertebrates and reptiles were present along the entire gradient of modification and there was a clear threshold in the diversity of native plants along the gradient. This threshold was reached after the management practice of ploughing was applied to a site. Sites that had not been ploughed were found to be similar in their native plant diversity, and all unploughed sites had significantly higher native plant diversity than unploughed sites. There was considerable variation in the abundance of individual plant and Coleoptera species along the modification gradient. The most intensively modified sites had the lowest plant diversity, the lowest abundance and diversity of Orthoptera, as well as the lowest abundance of common skinks. Sites with low levels of modification contained a higher abundance of common skinks, and, native forbs, lichens and bryophytes than the more intensively modified sites. With regard to individual plant and Coleoptera species recorded, there were generally not clear thresholds for their presence and absence along the modification gradient. Rather, there was a gradual turnover for most species along the gradient such that the plant and Coleoptera community at opposing ends of the gradient had less species in common sites of similar modification levels. A high proportion of the Coleoptera species observed were present in all sites, suggesting that disturbance has selected for an adaptive generalist life trait, and that the species remaining comprise the resilient portion of the Coleoptera fauna. The relationship between Coleoptera communities and the gradient of modification was scale dependent, with the strongest relationship being observed at the largest scale measured. The hypothesis that faunal diversity and abundance would be best predicted by the structural diversity of the vegetation rather than by plant species diversity was tested. Structural diversity was strongly correlated (p < 0.01) with Coleoptera diversity, and Coleoptera abundance whereas plant species diversity was not. However, plant species diversity was a stronger correlate of common skink abundance than plant structural diversity. The structural diversity of the vegetation has the potential to be measured remotely and could be a correlate for faunal diversity and abundance when undertaking landscape scale studies. This thesis demonstrates that native biota exists within the agricultural environment of the mid-altitude tall tussock (Chionochloa rigida) grasslands of eastern Central Otago despite intensive modification in some areas. The findings suggest that it is possible to integrate the objectives of agriculture and the conservation of some faunal groups especially for the more resilient species. However, this study also indicates that relatively unmodified sites are valuable reservoirs of biodiversity in the mid altitude zone and it is recommended that the limited number of lightly modified sites that remain in the mid altitude zone be conserved.

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