Understanding of grass genome structure and evolution has been significantly advanced through comparative genomics. The genomes of most cool-season forage and turf grasses, belonging to the Pooideae subfamily of the grasses, remain understudied. Creeping bentgrass (Agrostis stolonifera) is one of the most important cool-season turfgrasses due to its low mowing tolerance and aggressive growth habit. An RFLP genetic map of creeping bentgrass using 229 RFLP markers derived from cereal and creeping bentgrass EST-RFLP probes was constructed for a comparative genome analysis. This genetic map was compared with those of perennial ryegrass, oat, wheat, and rice. Large-scale chromosomal rearrangements between the map of creeping bentgrass and the respective maps of the Triticeae, oat, and rice were observed. However, no evidence of chromosomal rearrangements between the maps of creeping bentgrass and perennial ryegrass was detected, suggesting that these recently domesticated species might be closely related than expected. Further comparative genome analysis of creeping bentgrass was performed with the genome sequences of Brachypodium distachyon using sequences of the above-mentioned RFLP mapped markers and 8,470 publicly available A. stolonifera EST (AgEST) sequences. A total of 24 syntenic blocks were identified between the Agrostis linkage groups and the B. distachyon chromosomes. Orthologous loci of AgESTs (678) were identified in the B. distachyon genome, and these loci can be utilized in further comparative mapping of Pooideae species. Insights from comparative genomics with B. distachyon will be useful for genetic improvement of Agrostis spp. and provide a better understanding of the evolution of the Pooideae species.

Background: Recreating nature in a virtual environment comes with many aspects and challenges. Grass rendering is a part of this area, and both performance and visual results must be taken into consideration. A common optimization approach is through static level-of-detail (LOD), however, a certain visual loss comes with the use of this. Dynamic LOD is an alternative technique and exists in various forms, such as phong tessellation. The thesis will investigate the performance and visual implications of utilizing phong tessellation in grass rendering. Objectives: The main objective is to examine the implications of utilizing phong tessellation in grass rendering in terms of performance and visual results. Different scenarios will be examined, providing an overview while identifying performance and visual patterns of the technique. Methods: An experiment conducted via a DirectX 11 implementation was used to collect all data in scenarios that varied in the number of blades and how the tessellation falloff rate was described. The data collected was the average frame time during a 30-second duration as well were rendered images saved to disk from two points of view. Two reference scenes existed that only used a single LOD of either low- or high-quality grass, while no tessellation was applied. The data of each scenario and scene were compared to one another, and the visual differences were identified using the image difference evaluator FLIP. Results: The results show that different scenarios provide different benefits. Some scenarios contain smaller visual errors, while others perform efficiently. Overall a linear detail-falloff rate both performs well at various blade amounts and produces similar or smaller visual differences to the other scenarios. However, the results also show that the technique does not fit every set of hardware, at least not in demanding scenarios. Conclusions: The findings of this thesis show that the method has the potential to be a valid option in terms of performance and visual quality. It is, however, important to consider the specific use case as it is not applicable in every situation and to consider what hardware the application will run on.

Invasive species are generally regarded as detrimental to native communities because they cause increased competition and community structure alterations. There is therefore a critical need to understand the ecological processes underlying the establishment and spread of invasive species. While most studies to date have focused on the role of competition in species invasions, trophic dynamics may also play a fundamental role in the establishment and spread of non-natives, especially in cases when a non-native species experiences differential predation pressure relative to a native competitor. Herein I explore the potential for differential granivory pressure by a native rodent (Heermann’s kangaroo rat, Dipodomys heermanni arenae) on native shrubs and an invasive plant (Veldt grass, Ehrharta calycina). Veldt grass, a perennial tufted grass native to South Africa and introduced to California in 1929, is highly invasive, and the shift of native coastal dune scrub to a grassland, dominated by Veldt grass, is considered one of the factors that led to the decline of the federally endangered Morro Bay kangaroo rat. However, kangaroo rats are largely graminivores (consume grass seed) and are known to consume invasive grasses and other plants. Differential seed preferences for native and Veldt seed were examined by placing feeding stations containing each seed type in habitats dominated by either native plants or Veldt grass. Each feeding station was monitored using motion-activated game cameras and the amount of each seed type collected by nineteen individually-marked, wild kangaroo rats was documented. These marked kangaroo rats were monitored both in native and Veldt grass habitats, allowing for the testing of habitat origin (Native vs. Veldt), sex (male or female) and seed type on the amount of seed taken. Nine of the kangaroo rats harvested Veldt grass seed. Though females collected more seed than males, there was no difference between the amounts (% of available seed) of Veldt grass and native seed collected. Habitat of origin (i.e., habitats with Veldt grass present or habitats without Veldt grass) had no effect on the amount of seed collected or the type of seed collected. During seed station trials, kangaroo rats were also recorded removing seed heads from naturally occurring Veldt grass stalks, providing clear documentation that Heermann’s kangaroo rats do collect Veldt grass seed. Accompanying laboratory seed preference trials were also conducted to confirm the consumption of Veldt grass seed. These controlled laboratory trials revealed that Heermann’s kangaroo rats will consume Veldt grass seed, although Veldt grass seed was consumed in smaller amounts (g) than millet and sunflower seed, which were presented simultaneously. These findings indicate that non-native Veldt grass may provide an additional or alternative source of seed for kangaroo rats, which could provide a partial explanation for why kangaroo rats are able to survive in monocultures of Veldt grass.

No description available.

No description available.

Microstegium vimineum, or Japanese stilt grass, is an invasive species that readily outcompetes native vegetation and is of poor forage quality for wildlife. This species is widespread throughout the southeastern United States, including North Carolina. Much of this region is privately owned and there is a gap in the literature providing succinct information about the best methods of treatment, timing of treatment, and effects of treatment on native herbaceous plants in this region. In two parts, this study seeks to address this gap by employing treatments that are easily accessible to landowners at different times during the growing season and assessing the effects on the herbaceous plant community post-treatment. Results of this study found that application of glyphosate was the most effective treatment at M. vimineum removal, application of household vinegar was the most effective at increasing post-treatment species richness and diversity, and that seasonality did not play a role in the effectiveness of treatment options. This study will increase landowner knowledge on treating this invasive successfully and choosing a treatment that fosters an understory that meets their management goals.

Competition from hardwood species has long been considered a constraint on longleaf pine (Pinus palustris). However, evidence suggests that hardwood midstories may improve longleaf regeneration on xeric sites. Additionally, overstory retention for red-cockaded woodpecker (Leuconotopicus borealis; RCW) habitat may be inadvertently contributing to regeneration failures. Experimental plots in the North Carolina Sandhills were planted with containerized longleaf seedlings across a gradient of overstory density, and hardwoods were chemically controlled by treating at planting, treating after one year, or left untreated. Seedling survival (percent), growth (mass), and brown spot needle blight (percent infected seedlings; BSNB) were measured after two years. Seedling survival, growth, and BSNB infection rates were inversely related to overstory density. Midstory treatments did not significantly affect seedling survival, growth, or BSNB infection rates. Early results did not show facilitative effects from a hardwood midstory, but indicated overstory densities greater than 12 m2/ha negatively impact longleaf regeneration.

No description available.

No description available.

Organisms respond to changes in their environment using different strategies. Understanding how species deal with changes expected due to ongoing climate change is important for making accurate predictions about their effect on ecosystems. Geothermal areas provide a natural warming laboratory because the species present have been exposed to warming over generations. This study used geothermal areas in Iceland to study plant fitness and phenology in a common garden experiment. Additionally, plants were exposed to a snow manipulation treatment. In the experiment, 794 individuals of Festuca rubra were used; 375 originated from non-heated soil and, of these, 182 were exposed to ambient snowfall and 193 were exposed to snow removal treatment; 419 of the individuals originated from geothermally heated areas and, of those, 226 were exposed to ambient snowfall and 193 to snow removal treatment.  I expected both phenological and fitness differences, such that plants from geothermally heated areas; (1) develop slower, (2) have a lower chance of survival and probability to flower. However, I expected no difference in biomass between plants from geothermally heated soils and non-heated soils. For plants exposed to snow removal treatment I hypothesized the effects on fitness and phenology would depend on the winter condition. Results showed there were no overall differences between plants originating from geothermally heated soils and plants originating from non-heated soils in any of the recorded responses. Snow had an effect on biomass allocation, where plants exposed to ambient snowfall produced a larger proportion of reproductive biomass; there were also tendencies that the reproductive structures were more numerous and had a higher biomass overall. My results suggest F. rubra shows a plastic response to geothermal warming and that snow cover has a positive effect on fitness (reproductive biomass). The study is an important contribution to understanding the ways in which plants cope with changes in temperature and how they are affected by changes in snow regimes.