The response of grass, forb, and shrub seeds to the subalpine environment during the fall and under winter snow and under laboratory conditions at 20/28 C was observed for 3 consecutive years at an elevation of about 3000m on the Wasatch Plateau in central Utah. Seeds in nylon sleeves were planted under 2 cm of soil before snowfall. Under snow plantings were made directly on the soil surface and under 2 cm of soil. The seeds planted before snowfall were removed each year on four occasions: when under snow plantings were made, after snow depth exceeded 130 cm (deep snow), just before spring snowmelt, and 10 or more days following snowmelt when soils had warmed. Seeds planted under snow or under snow and soil were removed on two occasions: after snow depth exceeded 130 cm and just before the snow melted in the spring. Environmental conditions which produced seed germination varied with species, origin of species, age of seed, and temperature. Fifty-four of the 60 species planted in September under 2 cm of soil before snowfall had some seed germinated when examined just before the snow melted in the spring. Fifty of the same species planted after winter snow covered the ground in November also had some seed germination just before the snow melted in the spring. Seed germination at the near 0 C temperatures on the soil surface under snow was usually similar to the comparable seed lots also placed under 2 cm of soil. Germinability of the grasses, forbs, and shrubs studied was placed in three broad classifications: (1) Little or no seed dormancy with germination at low and warm temperatures. Seeds germinated soon after harvest at temperatures near 0 C and also in the laboratory at 20/28 C. Examples are Agropyron desertorum, A. intermedium, Chrysothamnus viscidiflorus, and Lupinus alpestris. (2) Little or no seed dormancy with germination only at warm temperatures. Seeds did not germinate at the low temperatures present in the subalpine zone during the fall and winter but germinated readily in the laboratory at 20/28 C. Examples are Aquilegia caerulea , Potentilla gracilis var. pulcherrima, Rudbeckia occidentalis, and Valeriana edulis. (3) Dormancy at seed harvest. Germination was usually increased by near 0 C temperatures, by aging, and by other environmental conditions present under deep snow. Examples are Agropyron trachycaulum, Delphinium barbeyi, Madia glomerata, and Ribes cereum var. inebrians.

I studied the ecological factors related to declining forest forb communities in the Lower Peninsula of Michigan during 2007 and 2008. Data on forb demography, fecundity, and deer herbivory rates were collected for endemic forbs given deer density and site-specific environmental factors. Investigations into endemic forbs were conducted at the population-, community-, and landscape-levels to detect overarching trends. Diverse and abundant forb communities were principally found in areas with available water and rich soil organic matter and were not affected by sympatric vegetation competition, canopy density, or deer densities. Deer densities were highest in lowland conifer stands, vegetated open lands, and heterogeneous landscapes, but herbivory was driven by population-level processes including the selection of specific forb species at the time of seed production. At the landscape level, soil conditions and human influence were major factors affecting the distribution of endemic forb communities. Soil conditions exhibited a non-linear, but generally positive relationship with forb diversity, and human influence negatively affected site diversity. Soil conditions and road densities were used to develop a spatial model identifying a gradient of priority-conservation areas across the study area. Conservation agencies interested in similar vegetation communities should consider anthropogenic factors, nutrient cycling, and local environmental conditions when conducting ecological research and identifying forb conservation areas.

In southern Africa, disturbance contributes to the heterogeneity of grassland and savanna ecosystems. Fire and grazing act as the primary disturbances in these systems, and interactions between the two are common. As such, an understanding of the relationship between fire and grazing is essential for the conservation of biotic diversity and the production of high-quality forage for game and livestock. Frequent fires followed by concentrated grazing have been shown to facilitate patches of short, palatable grasses ("grazing lawns") within grassland and savanna landscapes. The effects of grazing lawn management on other aspects of biodiversity have received little attention. Forbs (non-graminoid, herbaceous plants) are an important component of grassland ecosystems, but how they respond to disturbance is largely unknown. This study compared changes in forb communities on and off of firebreaks (an extreme example of a grazing lawn) in a high altitude mesic grassland. Native herbivore biomass was significantly higher on firebreaks than in the surrounding lightly grazed matrix and the firebreaks, while more compacted, did not show significant signs of degradation. There were no significant differences in forb abundance or richness between annually burned and intermittently burned plots, and there was no species turnover associated with the annually burned, heavily grazed treatment. Speciesspecific differences in functional traits on annually burned and intermittently burned plots were likely a function of light limitation, as mammalian palatability scores were nominal. Ultimately, ten years of intensive fire and grazing have had minimal impact on forb communities in a high altitude mesic grassland. The results indicate that in this type of Highveld grassland, heavily grazed and annually burned patches are not detrimental to the forb community and clearly enhance habitat diversity for grazers.

The Great Basin is North America's largest desert, encompassing 135 million acres. Grazing and other anthropogenic activities in the Great Basin have put heavy demands on the landscape over the last 150 years. Heavily grazed areas lack diversity which allows the spread of exotic weed species. Cheatgrass (Bromus tectorum L [Poaceae]) has invaded and shortened fire frequency intervals from historic 30—100 years to as few as three to five years. Post-fire reseeding of native species is requisite for restoration of highly invaded ecosystems thus, preventing complete conversion to exotic weeds. Most native shrubs and grasses are available for restoration projects, but native forbs are largely unavailable or expensive. This situation led to the creation of The Great Basin Native Plant Selection and Increase Project (GBNPSIP). In 2000 this project was initiated as a joint effort between the Bureau of Land Management, Forest Service Research, and the Utah Division of Wildlife Resources in an effort to make native seed more available and less expensive for landscape scale restoration projects. To meet restoration goals the GBNPSIP project promotes cultivation of native species to increase seed supplies. This research focuses on overcoming seed dormancy issues that have hindered cultivation through scarification and evaluating germination, establishment, and seed production in a cultural setting of four lupine species: hairy big leaf lupine, (Lupinus prunophilus M.E. Jones [Fabaceae]); silky lupine, (L. sericeus Pursh); silvery lupine, (L. argenteus Pursh); and longspur lupine, (L. arbustus Dougl. ex Lind) five scarification treatments were evaluated sulphuric acid and mechanical treatments significantly improved germination on three of the four species tested. All other treatments were unpredictable and not significant. No treatments significantly improved germination of L. arbustus and three of the five treatments significantly decreased seed germination from the control. Results demonstrate that scarification method, and exposure interval, differ in effectively increasing % germination among species. Germination, establishment, and seed production were evaluated using two planting methods for each species. Broadcast plots (covered) were covered with N-Sulate fabric™ and 5 cm (2 in) of sawdust. Control plots (uncovered) were drilled and left untreated. Germination was significantly improved for all four lupine species under treatment conditions. Lupinus prunophilus and L. sericeus exhibited the greatest improvement in germination when covered. Germination of L. argenteus and L. arbustus were also significantly improved (p<0.0001 and p=0.004, respectively) by the covered treatment. Higher germination in the covered treatment was mirrored in establishment for every species except L. arbustus. There is an advantage of using the covered treatment, but low yields make cultivation unprofitable.

Master of Science / Department of Biology / David C. Hartnett / The effects of bison activities on forb diversity and cover have been well-established, but less is known about how forb life history is altered by bison-mediated habitat changes. This study had three main objectives: 1) to evaluate the hypothesis that release from aboveground competition with grasses may contribute to the increased cover and diversity of forbs in prairie grazed by bison relative to ungrazed prairie, 2) to determine whether differences in forb reproductive effort between grazed and ungrazed habitats were size-dependent, and 3) to look for evidence of a trade-off between allocation to vegetative and sexual reproduction. The growth, biomass allocation, and sexual reproduction of six common unpalatable perennial species were measured and compared between bison-grazed and ungrazed tallgrass prairie burned at 2-year intervals: Ambrosia psilostachya, Artemisia ludoviciana, Baptisia australis, Psoralidium tenuiflorum, Solidago canadensis, and Vernonia baldwinii. Vegetative reproduction was also measured for B. australis¸ S. canadensis, and V. baldwinii. Light availability, canopy density and height, and percent cover of neighboring plants were measured in each studied individual’s immediate neighborhood and compared between habitats to establish the possibility of differing aboveground competition. Aboveground competition may be lower in bison-grazed habitats, as evidenced by differences in habitat characteristics and plant performance found in this study. In bison-present habitats, sexual reproduction was elevated for all six species and average plant size was greater for all species except A. psilostachya. Vegetative reproduction was not clearly different between habitats for all three species examined. Sexual reproduction increased with size for all species, and the relationship differed significantly between habitats for all species except A. psilostachya. Allocation to vegetative reproduction was not generally related to aboveground biomass, nor was there a clear trade-off between allocation to vegetative and sexual reproduction. The results of this study provide evidence that release from aboveground competition with grasses promotes the growth and sexual reproduction of the studied species of forb, and that differences in sexual reproduction are not entirely size-dependent. Patterns in allocation to vegetative reproduction were less clear and were not clearly tied to sexual reproductive allocation.

Causes and consequences of woody encroachment into grass dominated systems have been widely studied, however functional mechanisms which promote encroachment are largely unknown. Many expansive woody species are shrubs with rhizobial or actinorhizal N-fixing symbiotic associations. Morella cerifera L. (Myricaceae) is an actinorhizal N-fixing shrub which rapidly expands into grasslands on the barrier islands off the coast of Virginia, USA. The objective of this research was to determine physiological drivers of woody encroachment resulting in increased woody cover of M. cerifera on Southeastern, US barrier islands. Variations in physiology and resource use efficiencies (RUE) of M. cerifera and co-occurring shrubs were determined, and edaphic characteristics beneath shrub thicket canopies and in open areas were quantified as indications of resource availability. Analysis of dune vegetation and soils showed severe freshwater limitation and reduced plant height of dune forbs suggesting dunes represent an upper elevational boundary for M. cerifera distribution. Soil N availability was higher beneath shrubs compared to open areas, and both physiology and isotope effects showed facilitation of the non-fixing shrub, Baccharis halimifolia, by M. cerifera which may lead to increased rates of woody encroachment as B. halimifolia colonizes expanding thicket edges. Morella cerifera and other N-fixers had higher %refixation within stems which resulted in higher carbon use efficiency (CUE) and water use efficiency of N-fixing shrubs compared to non-fixers. Results of an N-fertilization experiment suggest B. halimifolia has higher dependence on and demand for soil nutrients compared to M. cerifera. Morella cerifera showed no signs of resource deficiency or reduced physiological capacity even at 0 ppm total Nsoil. Morella cerifera transitioned from utilizing solely fixation derived N to soil N as N concentrations increased providing another mechanism leading to increased CUE and, indirectly, overall RUE. In summary greater RUE, lower resource demand, and greater resource availability for M. cerifera compared to co-occurring shrubs may result from symbiotic root associations with bacteria and fungi. While expansion of M. cerifera thickets is limited to lower elevational interdunal depressions, expansion may continue and result in increased rates of woody encroachment through facilitation of co-occurring shrubs.

Intensive agricultural systems have had several ecological effects on the surrounding ecosystem, including contributing to widespread pollinator declines. In order to help supplement bee communities and potentially improve crop production, we set out to study annual forb plantings adjacent to dry bean crops to determine the pollinator response to both plantings and any potential effects on dry bean yield. We found that annual forb plantings provided continual floral resources throughout the sampling period, which can support bees and their pollination services in agroecosystems. We also found cross-pollination had no effect on dry bean yield in Carrington and a negative effect in Hettinger, which could be due to methodological issues. While we did not observe a yield increase in dry bean production, the addition of annual forb plantings in agroecosystems could help support the local bee community, and potentially encourage pollination services in other crops that do benefit from insect pollination.

Les assemblages à base de fixations montées avec interférence et prétension sont largement utilisés dans le domaine de la construction aéronautique, notamment dans les zones structurales fortement chargées et soumises à des sollicitations de fatigue. Les performances de ces assemblages sont sensibles à de nombreux paramètres liés à la géométrie et aux matériaux mis en jeu. Pour optimiser la qualité de ces liaisons et atteindre les gains de durée de vie attendus, il est important de disposer de modèles à la fois rapides et fiables qui permettent, dès la phase de conception, d’évaluer l’influence des paramètres d’entrée sur les efforts caractéristiques de l’assemblage. Les travaux s’attachent, dans un premier temps, en s’appuyant sur une modélisation par éléments finis très détaillée du processus d’assemblage, à bien identifier les phénomènes mécaniques les plus caractéristiques des liaisons étudiées. Une approche analytique de premier niveau est ensuite développée. Elle conduit à un modèle d’estimation des efforts et de contraintes présentes dans les pièces assemblées qui produit des résultats très voisins de ceux obtenus avec le modèle de référence. Un modèle numérique dédié,basé sur des éléments finis axisymétriques et codé sous Matlab, est ensuite proposé. Il est apte à évaluer l’influence des variations des paramètres le long de l’interface entre les pièces tout en considérant les effets de bords. Une étude expérimentale basée sur une instrumentation de l’assemblage avec des fibres optiques à réseaux de Bragg est présentée. Les corrélations entre les résultats expérimentaux et ceux issus des modélisations sont très satisfaisantes / Assemblies based on interference fit fastener and preload are widely used in the fieldof aircraft construction, especially on structures heavily loaded and subjected to fatigue stresses.The performances of these assemblies are sensitive to many parameters related to the geometry and to the constitutive materials. To improve the quality of these assemblies and achieve the assembled parts. This simple model produces results very similar to those obtained with thereference model. A dedicated numerical model, based on axisymmetric finite elements and developed using Matlab code, is also proposed. It is able to evaluate the influence of parameter variations along the interface between the parts while considering the side effects. An experimental study based on an assembly instrumented with Fiber Bragg Gratings is presented.The correlations between the experimental results and those from the models are very satisfactory lifetime gains expected, it is important to use, from the early design phase, fast and reliable models in order to evaluate the influence of input parameters on the most significant efforts that take place around the fastener. In a preliminary phase, the work focuses on clearly identifyingthe mechanical phenomena characterizing the behavior of the mechanical connections understudy, using a very detailed finite element reference model of the assembly process. An analytical approach is then developed. It leads to a first level model for estimating loads and stresses in the assembled parts. This simple model produces results very similar to those obtained with the reference model. A dedicated numerical model, based on axisymmetric finite elements and developed using Matlab code, is also proposed. It is able to evaluate the influence of parameter variations along the interface between the parts while considering the side effects. An experimental study based on an assembly instrumented with Fiber Bragg Gratings is presented.The correlations between the experimental results and those from the models are very satisfactory

The harsh environmental and poor economic conditions of the Bolivian Altiplano require intervention to assist many of those that live there to become economically self-sufficient. We attempted to find introduced dry season reserve forage grasses that could produce enough biomass to be useful as feed for livestock, and that could also produce enough seed to distribute to farmers. While some of the grasses produced reasonable amounts of biomass, none produced seed in quantities that would be even close to being economically viable. The most likely cause of this is that the timing of resources that the grasses need to flower is very different between Bolivia and the areas from which the grasses originally came. We concluded that either the conditions under which the grasses are grown would need to be changed (i.e., earlier irrigation), or pre-adapted native species should be used. Native forbs are a critical component of any natural ecosystem, and thus should be included in wildland restoration projects. However, because the seed is currently collected by hand from the wild, it is very expensive, and this limits the ability of land managers to utilize it. A possible solution to this dilemma is for growers to commercially produce the seed and thus drive down the cost. In such a situation, it would be necessary to use herbicides to control competing weeds. We analyzed the effects of 5 herbicides on 7 species of native Utah forbs at 3 growth stages to learn which herbicides could safely be used on the test plants. We found that the plants' reaction the herbicides is largely species- and growth-stage specific.