Global ETD Search

11	Vegetation changes on Swedish mires : Effects of raised temperature and increased nitrogen and sulphur influx Gunnarsson, Urban January 2000 (has links) Since the start of the industrialisation, the deposition of nitrogen and sulphur and the atmospheric concentrations of greenhouse gases have increased. The main objectives of this study were to find how these changes in climate and deposition can change the vegetation of mire ecosystems and the growth of Sphagnumspecies. Two main approaches were applied: re-investigated of two mires previously investigated 40-50 years ago and experiment manipulations. The plant species diversity had decreased on one of the two re-investigated mires (Skattlösbergs Stormosse; central Sweden), but the total number of species was unchanged on the other (Åkhultmyren; southern Sweden). On Skattlösbergs Stormosse, an acidification was found in the high pH areas, coinciding with reduction in rich fen species. At Åkhultmyren, there was a similar reduction in pH, but the changes in the plant composition also indicated increased nutrient levels and a drier mire surface. Therwere large changes in species composition on Åkhultmyren. For instance Scheuchzeria palustris had disappeared from the investigated area. Further, the cover of Scots pine (Pinusylvestris) had increased, which can be explained by a changed ground-water table regime. Monitoring of pines growing on a bog over a ten-year period showed that pines growing higher above the ground-war table had higher survival than lower-growing pines. Experimental addition of nitrogen during 3-4 years reduced Sphagnum growth in bogs and poor fens repressenting a wide range of ambient nitrogen deposition. A changed interspecific competitive relation was found between S. lindbergand S. balticum when increasing nitrogen influx, but the competitive relations between two hummock-growing species pairs did not change in a three-year nitrogen fertilization study. Sulphur additiodid not affect the production or length increment in S. balticum. An increased temperature reduced Sphagnum growth, but there were no indications of altered competitive relationshipbetween hummock and hollow inhabiting Sphagnum species in a four-year experiment. Developmental biology Acidification growth long-term studies mires nitrogen species richness Sphagnum succession sulphur temperature Utvecklingsbiologi Developmental biology Utvecklingsbiologi
12	L'impact à court et à long terme du programme MIRES sur la persévérance scolaire et la qualité de l'apprentissage des protégés Smith, Sharon 18 April 2018 (has links) Les programmes de mentorat sont des moyens d'intervention privilégiés pouvant être offerts à des clientèles variées provenant de milieux éducatifs différents. De nombreuses études leur attribuent des retombées très positives pour les participants, comme de meilleurs résultats scolaires, une plus grande motivation et une plus grande persévérance scolaire. La présente étude vise à évaluer l'impact à court et à long terme du Programme MIRES (Mentorat pour l'Intégration et la Réussite des Étudiants en Sciences) sur la persévérance scolaire des protégés et sur leurs attitudes et comportements scolaires. Destiné aux étudiant de première année au collégial dans un programme de sciences et technologies, le Programme MIRES vise à contribuer à la création de la relève scientifique et à favoriser la persévérance et la réussite scolaires des participants. Deux hypothèses ont été posées dans ce mémoire. La première stipule que les participants au Programme MIRES seront plus persévérants dans leur programme d'étude que leurs pairs du groupe contrôle. La seconde stipule que les protégés du Programme MIRES afficheront, à la fin de l'intervention, de meilleures attitudes et comportements scolaires que leurs pairs du groupe contrôle. Ces hypothèses ont été testées à partir d'un devis expérimental prétest/post-test avec groupes de comparaison équivalents. Le groupe expérimental et contrôle étaient respectivement formés de 251 et 246 participants, tous étudiants dans un programme de S&T au collégial. Quatre temps de mesure ont été prévus. Le premier temps de mesure eut lieu avant l'exposition au programme, les deux temps subséquents eurent lieu pendant l'exposition au programme et le dernier temps se tint un an après la fin du programme. Les attitudes et les comportements scolaires des protégés ont été évalués par le Test de réactions et d'adaptation au collégial (TRAC) complété par les participants. Des analyses de variance à mesures répétées ont été effectuées pour chacune des dimensions du TRAC sélectionnées. La persévérance des participants fut mesurée à partir de données institutionnelles. Les résultats indiquent que le Programme MIRES a eu un effet significatif sur la persévérance scolaire des participants. Étonnamment, il n'a pas eu d'impact sur les attitudes et les comportements scolaires des participants. Ces résultats sont discutés à la lumière de l'orientation du Programme MIRES et d'autres facteurs ayant pu jouer un rôle de modérateur dans les analyses effectuées. LB 5.5 UL 2011 S659 MIRES (Programme) Persévérance aux études Étudiants du collégial -- Attitudes
13	L'impact d'un programme de mentorat (MIRES) sur l'ajustement au collégial, le profil décisionnel et la culture scientifique des étudiants en mathématiques, sciences et technologies au collégial Godin, Fanny 16 April 2018 (has links) Un nombre important d'étudiants cheminant en sciences ou dans l'un des programmes de technique physique ou technique biologique au collégial ne terminent pas leurs études dans ces domaines ou abandonnent complètement leurs études. Ce mémoire évalue l'impact d'un programme formel de mentorat par les pairs (MIRES) sur l'ajustement au collégial, le profil décisionnel et la culture scientifique des étudiants en mathématique, sciences et technologie au collégial. Les fondements de ce programme reposent sur deux champs de connaissances soient celui des facteurs explicatifs du décrochage en sciences et celui des pratiques efficientes en mentorat. Un devis expérimental avec groupe contrôle équivalent permet d'évaluer l'impact du programme d'une durée d'une année scolaire. Les résultats montrent que les protégés perçoivent un ajustement social et institutionnel de meilleure qualité, sont davantage certains de leur choix carrière et ont une culture scientifique de meilleure qualité que les jeunes du groupe contrôle. LB 5.5 UL 2009 G585 MIRES (Programme)
14	What has happened on Swedish mires? The effects of drainage on vegetation changes over recent decades Ljungqvist, Anna January 2022 (has links) As they are not only the home of many threatened species, but also one of the main actors in the global carbon cycle, peatlands are highly valuable ecosystems. Human disturbance, in particular drainage for forestry and agriculture, has substantially changed the state of the world’s peatlands and will continue to do so. Lowering the water table by drainage has many hydrological and biological effects, including an increased growth of trees and shrubs as well as reduced growth of the key peat moss genus Sphagnum, leading to peat degradation and release of carbon dioxide. The effects of drainage are sometimes used as predictions for how peatlands will respond to climate change, and undrained mires are thus expected to become more like drained ones in the future. The accuracy of that assumption has, to my knowledge, not been tested on a large scale. Here, I use data from two Swedish national monitoring programs to analyze how the vegetation on drained and undrained mires has changed in recent decades. The results showed an increased tree growth but a decreased establishment of new trees on both drained and undrained mires, implying that contrary to common belief there is no current large-scale afforestation of open mires in Sweden. Sphagnum had, surprisingly, increased on both drained and undrained mires, while other functional groups showed varying results. The tree growth rate was faster on drained mires, but in most other analyses the response to time did not differ depending on drainage regime. Thereby, this study found limited support for the hypothesis that undrained mires are becoming more like drained mires with climate change. peatlands mires bogs fens sweden vegetation plant ecology time trend data nfi nils climate change global warming mosses sphagnum afforestation trees wetland presence coverage drainage ditch Ecology Ekologi
15	Multispectral imaging of Sphagnum canopies: measuring the spectral response of three indicator species to a fluctuating water table at Burns Bog Elves, Andrew 02 May 2022 (has links) Northern Canadian peatlands contain vast deposits of carbon. It is with growing urgency that we seek a better understanding of their assimilative capacity. Assimilative capacity and peat accumulation in raised bogs are linked to primary productivity of resident Sphagnum species. Understanding moisture-mediated photosynthesis of Sphagnum spp. is central to understanding peat production rates. The relationship between depth to water table fluctuation and spectral reflectance of Sphagnum moss was investigated using multispectral imaging at a recovering raised bog on the southwest coast of British Columbia, Canada. Burns Bog is a temperate oceanic ombrotrophic bog. Three ecohydrological indicator species of moss were chosen for monitoring: S. capillifolium, S. papillosum, and S. cuspidatum. Three spectral vegetation indices (SVIs) were used to characterize Sphagnum productivity: the normalized difference vegetation index 660, the chlorophyll index, and the photochemical reflectance index. In terms of spectral sensitivity and the appropriateness of SVIs to species and field setting, we found better performance for the normalized difference vegetation index 660 in the discrimination of moisture mediated species-specific reflectance signals. The role that spatiotemporal scale and spectral mixing can have on reflectance signal fidelity was tested. We were specifically interested in the relationship between changes in the local water table and Sphagnum reflectance response, and whether shifting between close spatial scales can affect the statistical strength of this relationship. We found a loss of statistical significance when shifting from the species-specific cm2 scale to the spectrally mixed dm2 scale. This spatiospectral uncoupling of the moisture mediated reflectance signal has implications for the accuracy and reliability of upscaling from plot based measurements. In terms of species-specific moisture mediated reflectance signals, we were able to effectively discriminate between the three indicator species of Sphagnum along the hummock-to-hollow gradient. We were also able to confirm Sphagnum productivity and growth outside of the vascular growing season, establishing clear patterns of reflectance correlated with changes in the local moisture regime. The strongest relationships for moisture mediated Sphagnum productivity were found in the hummock forming species S. capillifolium. Each indicator Sphagnum spp. of peat has distinct functional traits adapted to its preferred position along the ecohydrological gradient. We also discovered moisture mediated and species-specific reflectance phenologies. These phenospectral characteristics of Sphagnum can inform future monitoring work, including the creation of a regionally specific phenospectral library. It’s recommended that further close scale multispectral monitoring be carried out incorporating more species of moss, as well as invasive and upland species of concern. Pervasive vascular reflectance bias in remote sensing products has implications for the reliability of peatland modelling. Avoiding vascular bias, targeted spectral monitoring of Sphagnum indicator species provides a more reliable measure for the modelling of peatland productivity and carbon assimilation estimates. / Graduate peatland peatland restoration peatland monitoring peatland modelling peat peat moss multispectral multispectral imaging multicamera array multitemporal multiple linear regression linear mixed effects Sphagnum sphagna Sphagnum capillifolium Sphagnum papillosum Sphagnum cuspidatum spatiospectral uncoupling near-sensing remote sensing phenospectral phenology phenologies phenospectral bias phenospectral libraries carbon assimilation carbon dioxide carbon dynamics carbon emissions carbon geographies carbon mineralization carbon sequestration carbon source carbon sink carbon storage irrecoverable carbon climate forcing methane Ecological Restoration restoration ecology ecohydrology ecohydrological restoration hydrology ecohydrological gradients ecological integrity reflectance nature based solutions ombrotrophic moss raised peatland mires mires photochemical reflectance index normalized difference vegetation index chlorophyll index climate change climate forcing climate envelope climatope nonvascular vascular bias plant functional type plant functional types structure equation models spectral vegetation indices hummock hollow acrotelm catotelm diplotelmic biocrusts organic soil periodicity moisture deficit senescence rejuvenescence productivity photosynthesis light use efficiency photosynthetic function photosynthetically active radiation water table hydrology rewetting depth to water table landscape change landscape degradation peat subsidence Burns Bog

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