Now showing items 1-14 of 14

• #### Anatomical And Mechanical Characteristics Of Woods Used To Manufacture Bassoons

The purpose of this dissertation was three-fold -- 1) to determine if anatomical characteristics and mechanical characteristics derived from tapping (the act of striking an object lightly) can be used to more accurately describe bassoon resonant wood than the characters in use now, 2) to determine if any Alaska hardwoods can be used to construct bassoons, and 3) to produce lists of potential North American hardwoods and resonant bassoon wood characters. The bassoon resonant woods (Acer spp., Dalbergia melanoxylon, and Pyrus spp.) were compared to a known non-resonant bassoon wood (Juglans nigra). Vessel length and width, fiber length, and axial parenchyma width were measured in sectioned and macerated wood slides, along with the ratios of crystalline cellulose, lignin, pectin, and other aromatics in the cell wall. Partial frequencies created from tapping specimens on each longitudinal face were measured from melodic and peak partial spectrograms, as well as the spectrum obtained from the beginning of the sound. MANOVA and univariate ANOVA showed the resonant woods were significantly different from the non-resonant Juglans nigra using the characters measured. These characters were then used to compare two Alaska hardwoods (Alnus rubra and Betula neoalaskana) to the temperate resonant woods (Acer spp. and Pyrus spp.) and the non-resonant Juglans nigra using k-means clustering, MANOVA, and univariate ANOVA. Both Alaska hardwoods grouped with the non-resonant Juglans nigra. Lastly a list of potential North American hardwoods to be checked anatomically was compiled, as well as a list of characters that combine those used now as well as characters found in this study.
• #### Arctic Alaskan Shrub Growth, Distribution, And Relationships To Landscape Processes And Climate During The 20Th Century

The primary change underway in the tundra of Arctic Alaska is the increase in air temperature and expansion of deciduous shrubs since 1980. I explored relationships between shrub expansion and relevant ecosystem properties such as climate, soil characteristics, erosion, and herbivory. Alnus viridis ssp. fruticosa (Siberian alder) shrubs located along streams, rock outcrops, or other features with active disturbance regimes showed a positive correlation between growth ring widths and March through July air temperature. Climate-growth relationships were much weaker for alder in adjacent tussock tundra. Additionally, tussock tundra sites had different vegetation composition, shallower thaw, lower mean annual ground temperature, lower mean growing season temperature, higher soil moisture, more carbon in mineral soil, and higher C:N values in shrub leaves than nearby non-tussock alder. Growth rings and site characteristics imply that preexisting soil conditions predispose alder shrubs growing in non-tussock tundra to respond rapidly to warming. Analysis of temporal series of aerial photography from 1950 and 2000 and of Landsat imagery from 1986 and 2009 showed an increase in percent cover of shrubs, primarily in riparian areas. This increase in shrubs is contemporaneous with a decline in peak discharge events from the Kuparuk River and a lengthening of the growing season since 1980, both of which may have caused the decline in sediment deposition observed in 3 of 4 lake sediment cores dated with lead and cesium isotopes. Both alder shrub growth and erosion are particularly sensitive to runoff dynamics during the snowmelt and green-up period, and these dynamics are affected by spring temperatures. Ptarmigan, moose, and hares forage heavily on shrubs protruding above the deepening snow during the late-winter, and selective browsing on willow vs. alder is likely influencing shrub community composition. The increase in shrubs during the 20th century may represent additional habitat for these herbivores, and herbivore-mediated changes in shrub architecture may have important implications for how shrubs trap snow and ultimately affect surface energy balance. Evidence from this thesis indicates shrub growth and cover have increased in response to persistent warming, particularly in areas where the organic layer is thinner and active layer deeper.
• #### Biochemistry of diatom photosynthetic membranes and pigment-protein complexes

Diatoms are an ecologically important group of algae in both marine and freshwater systems, but in spite of their significance little is known about the structure of their photosynthetic apparatus. This is due in part to the lack of a highly purified, oxygen-evolving thylakoid membrane preparation. Since thylakoid membranes purified from diatoms using methods developed for green plants did not evolve oxygen, a new procedure was developed for use with diatoms. An oxygen-evolving thylakoid membrane preparation is crucial for the study of photosynthetic pigment-protein complexes from these algae because the stability of the Photosystem I (PS I) and Photosystem II reaction centers was shown to be greatly reduced in thylakoid preparations that did not retain electron transport activity. As a result of the instability of PS I in some thylakoid preparations, a novel chlorophyll-binding complex was isolated that contained only the PsaA polypeptide. The isolation of this complex should prove useful in elucidating the structure of the PS I reaction center in all plants. Immunological and N-terminal protein sequencing methods were used to identify several photosynthetic proteins in the purified thylakoid preparation. These results provided evidence for posttranslational modification of two light-harvesting polypeptides (LHCPs) as well as of the PsaB subunit of the PS I reaction center core. Posttranslational modification of LHCPs and/or of PsaB has not been observed in green plants. In contrast to green plants, PS I in diatoms has been shown to be located in the inner thylakoid membranes. It was hypothesized that proteolytic processing of the C-terminus of PsaB in diatoms may be necessary for the PS I holocomplex to be present in the inner membranes, and that this processing may be responsible for the instability of PS I in purified diatom thylakoids. The existence of a functional, highly purified, and extensively characterized thylakoid preparation from diatoms will promote our understanding of the photosynthetic apparatus in these algae.
• #### Biocomplexity Of Nonsorted Circles In The Low Arctic, Alaska

The vegetation and soils in many arctic tundra regions are influenced by the distribution of nonsorted circles, unique patterned-ground features that dot the well-vegetated tundra landscape. They are flat to dome-shaped, bare soil patches 0.5 to 3 m across and lack a border of stones. Localized soil disturbance due to cryogenic processes creates unusual micro-environments with unique plant communities, slow soil development and deep active layers. The contrast between barren nonsorted circles and the well-vegetated stable tundra provides an ideal opportunity to examine the complex linkages among vegetation, soil and disturbance through cryogenic processes, offering insight into how the tundra system operates. The central goal of this thesis is to understand the complex linkages of the nonsorted-circle system along a natural climate gradient on the North Slope in the Alaskan arctic tundra at different scales, ranging from plot level to regional changes. This thesis examines the interactions among vegetation, soil and cryogenic regime by treating the nonsorted circles within the stable tundra as a single complex system. The thesis presents a formal description and analysis of the plant communities on and off nonsorted circles along the climatic gradient using Braun-Blanquet classification approach. The thesis also studies the physical effects of vegetation, soil organic mat and snow cover on the microclimate of nonsorted circles and the stable tundra along the same climate gradient. The influence of vegetation on cryogenic processes is examined experimentally by manipulating the plant canopy on nonsorted circles. When compared to the stable tundra, nonsorted circles have minimal vegetation cover, resulting in warm soil temperatures and deep thaw depths in summer and allowing for increased ice-lens formation during freeze-up. The resulting frost heave and needle-ice formation at the soil surface maintain the bare surfaces of the circles through soil disturbance. Cryogenic processes dominate the system at the northern sites, while the warmer climate towards the south allows for thick vegetation mats on and off the nonsorted circles, suppressing cryogenic processes. The strength of the interactions among vegetation, soil and cryogenic regime may change under a warming arctic climate, possibly leading to the local disappearance of nonsorted circles.
• #### Biotic Pest Damage Of Green Alder (Alnus Fruticosa ): Susceptibility To A Stem Disease (Valsa Melanodiscus) And Functional Changes Following Insect Herbivory

Since the late 1990s, researchers have been predicting that a warming climate will lead to higher levels of plant disease damage. This appears to be the current trend in the boreal region; however, the level of complexity inherent to plant-pest interactions makes it difficult to make predictions across plant-pest systems. This study focuses on a boreal shrub in Alaska, Alnus fruticosa, which is currently a host to several insect and fungal pest species that are either already at epidemic status or have recently achieved epidemic status on other Alnus species in Alaska. Against the backdrop of a warming boreal forest, the overall aim of my study was to evaluate the response of A. fruticosa to two types of pest damage: the stem canker disease Valsa melanodiscus (anamorph Cytospora umbrina) and defoliation damage from insect leaf chewers. Our results indicate that, despite pest-related damage to the sapwood or leaf area, alders have physiological mechanisms in place to maintain homeostasis or recovery following disease damage. At the leaf-level, alders adjusted photosynthesis and stomatal conductance to cope with disease, despite decreased water transport and down-regulated light-response. At the ramet level, alders coordinated rates of water loss, hydraulic conductance, and maintenance leaf water balance following partial defoliation. These physiological host responses are not part of classical disease triangles, yet these types of host responses are likely to affect disease outcome in certain plant-pest systems and could potentially determine the trajectory of disease development.
• #### Establishment of native plants on disturbed sites in arctic Alaska

Roads, camps and other structures associated with the Trans-Alaska Pipeline were placed on gravel pads to protect underlying permafrost. Gravel was mined from floodplains, resulting in loss of riparian wildlife habitat. Revegetation of abandoned pads using non-native grasses has been unsuccessful. Native plants might be more persistent and contribute to replacing lost habitat. The naturally-occurring pioneer community on gravel pads consists mainly of willows Salix alaxensis and S. glauca, fireweed Epilobium latifolium, horsetails Equisetum arvense and legumes in the genera Astragalus, Oxytropis and Hedysarum, all species of riparian gravel bars. Ten years after abandonment mean total cover of native species on 16 gravel pads was only 2.7% and mean number of species per site was 4.4. Distance from riparian seed sources explained 25% and 40% of variation in cover and diversity respectively. Legumes were more restricted to sites near the river than were fireweed and willows. In the laboratory, no germination of S. alaxensis occurred at water potentials $< -0.2$ MPa, which probably occur often on gravel pads. In the field, germination was increased by watering or by a rough surface which provided moister microsites. Growth of seedlings was limited by the supply of mineral nutrients. Survival was high and not limited by availability of water or nutrients. In the laboratory, few legume seeds germinated at water potentials $< -0.5$ MPa. In the field, germination was higher on a rough surface which provided moister microsites. Greenhouse experiments indicated that symbiotically-fixed nitrogen contributed significantly to the growth of legume seedlings, especially when availability of mineral N was low. Rhizobia-free legume seedlings transplanted to a gravel pad developed nodules whether or not they were inoculated with rhizobia, but total weight and nodule weight tended to be higher in inoculated seedlings. Some native plants, primarily riparian species, are capable of establishing and growing on abandoned gravel pads. The low cover and diversity of naturally-colonized sites are attributed to (1) limited dispersal from riparian seed sources, (2) lack of water for germination, and (3) lack of nutrients to support growth. Both willows and legumes have promise for use in restoration.
• #### Experimental And Theoretical Studies Of The Pollination Ecology Of Gynodioecy

Gynodioecy, a breeding system with females and hermaphrodites, is the most common dimorphic system in plants and found in more species than all other polymorphic systems combined. One unresolved question in gynodioecy evolution is how dramatic sex ratio variation (0-100% female) is maintained among populations. To address this gap, I used complementary empirical and theoretical approaches to ellucidate pollinators' role in the evolution and maintenance of gynodioecy and variation in gynodioecious sex ratios. I conducted two field studies restricting the types of pollinators available to artificial populations of Silene vulgaris. The first study contrasted pollination by pollen collectors, strongly favoring hermaphrodites, with nectar collectors that readily visit both sexes. Hermaphrodites' relative fitness was greatest in the context of pollen collectors whereas females had dramatically higher relative fitness in the context of nectar collectors, demonstrating pollinators' potential to restrict or facilitate gynodioecy. The second study measured fitness in artificial populations of S. vulgaris with either pollen or nectar collecting pollinators in the context of a large natural population, providing access to more pollen sources and more pollinators. Female relative fitness was constant across pollination contexts, unlike in the previous study, as an abundance of pollinators and pollen sources diminished the differences in pollination contexts arising from pollinator bias. On the theoretical front, I developed mathematical models that describe female and hermaphrodite fitness in terms of pollinator abundance and behavior. Then, a single locus nuclear model of gynodioecious sex ratio evolution was used to describe equilibrium female frequency as well as the conditions permitting gynodioecy in terms of pollinator behavior. As in the field studies, I found that pollinators' influence could range from subtle to dramatic. More specifically, under realistic parameter values, where pollinators prefer hermaphrodites to females, incorporation of pollination ecology generally reduces female frequency, and the conditions for the evolution of gynodioecy become more stringent than if pollination processes were ignored. Together, these studies bolster the surprisingly overlooked idea that evolution of gynodioecious populations is directly influenced by pollinator context.
• #### From Forest To Tundra: Historical Biogeography, Floristic Diversity And Nucleotide Variation In Balsam Poplar

The North America boreal forest extends across more than 10� of latitude from central Labrador to interior Alaska. Periods of major climate fluctuations, including glacial and interglacial cycles, drove major migrations in the Quaternary history of the boreal forest. Beringia, the unglaciated region between the Lena and Mackenzie rivers, is recognized as an important refugium for arctic plants during the last ice age, but its role for boreal trees remains controversial. The paleobotanical record indicates Populus balsamifera (balsam poplar) survived within Beringia during the last glacial. My research employed an interdisciplinary approach, combining techniques in the fields of ecology, evolution and population genetics, to reconstruct the late Quaternary migration history of balsam poplar and to describe and classify balsam poplar plant communities in the Alaskan Arctic. Chapter 1 describes the motivation for the research. Chapter 2 addresses whether a demographically-detectable population of balsam poplar was present within Beringia during the most recent ice age. I found that patterns of variation in chloroplast DNA are most consistent with the presence of a single population of balsam poplar south of the continental ice sheets through the Late Quaternary. Chapter 3 is an analysis of floristic diversity in balsam poplar communities across the Arctic Slope, Interior Alaska and the Yukon Territory and asks whether one balsam poplar-associated plant community spans the arctic and boreal regions, or if these communities differ. I found that arctic communities are dominated by arctic-alpine taxa, whereas boreal communities are dominated by boreal taxa. A strong linkage between climate and the occurrence of balsam poplar also was observed on the Arctic Slope. Chapter 4 is a study of nucleotide diversity in three nuclear loci across the range of balsam poplar. This was the first study to document geographic structure in genetic variation within the species. It also showed that diversity in three North American poplars (P. balsamifera, P. deltoides and P. trichocarpa) was substantially less than that of three Eurasian poplars (P. alba, P. nigra and P. tremula). Chapter 5 summarizes the research and points toward future research directions.
• #### Production of vascular aquatic plants in wetlands of Alaska: A comparative study

I examined the effects of climate and hydrology on aboveground biomass of macrophytes in wetlands across Alaska by investigating the effects of latitude, July mean air temperature, lake type (open, periodically inundated, and closed), hydrology, and water and sediment chemistry on emergent and submersed vascular plant biomass to determine environmental variables that influenced wetland plant growth. I sampled aboveground biomass of macrophytes in four wetland complexes within Alaska: Kenai and Tetlin National Wildlife Refuges, Minto Flats State Game Refuge, and the Arctic Coastal Plain near Prudhoe Bay, Alaska. In addition to peak aboveground biomass, I also collected water and sediment samples from each lake that were analyzed for water temperature, color, alkalinity, turbidity, pH, orthophosphate, $\rm NO\sb3/NO\sb2$-N, NH$\sb4\sp+$, and total sediment C, N, and P. I found a quadratic relationship between emergent plant biomass and latitude. Minto, the second most northern site, had the greatest plant biomass, Prudhoe Bay, the most northern site had the least, and Kenai and Tetlin had moderate levels of biomass. I found a positive linear relationship between emergent plant biomass and July mean temperature, suggesting that on-site summer condition is important in predicting biomass. Submersed plant biomass was better related to alkalinity, turbidity and sediment P than to latitude, which suggests that climate is not as important in predicting submersed plant biomass as it is in predicting emergent plant biomass. Emergent plant biomass differed spatially and temporally, while submersed plant biomass showed no distinct patterns in variation across the landscape and with changes in hydrologic input. Many water and sediment chemistry variables differed among lake types and between flood regimes. Emergent plant biomass was associated with changes in water level as well as changes in water. Plant species composition differed among lake types and tended to change with flood regime as well. A separate suite of species occupied closed lakes, while open and periodically inundated lakes tended to contain more similar plant species. Both climate and hydrology appear to have a significant impact on emergent and submersed plant biomass and species composition in wetlands of Alaska. These spatial and temporal differences have direct influences on secondary producers living in wetlands of Alaska.
• #### Quantifying Variability In The Alaskan Black Spruce Ecosystem: Linking Vegetation, Carbon, And Fire History

The boreal forest is the largest terrestrial ecosystem in North America, one of the least disturbed by humans, and most disturbed by fire. This combination makes it an ideal system to explore the environmental controls over species composition, the relative importance of abiotic factors and floristic composition in governing ecosystem processes, and the importance of legacy effects at a large regional spatial scale. In the boreal region of interior Alaska, Picea mariana (black spruce) is the predominant tree species and spans a wide range of habitats, including north-facing slopes with permafrost, lowland bogs, and high dry ridge-tops. This research uses a combination of site description and analysis from both locally near Fairbanks (54) and across a large region and number of sites (146) to answer questions about the regional variability and biodiversity of the black spruce forest type. Based on the relationships between species composition and environmental factors, topography and elevation were the most important gradients explaining species composition locally in the Fairbanks region, and mineral soil pH was the overriding environmental gradient across interior Alaska. To describe the floristic variability, I separated the black spruce forest type into three floristically-based community types and five community subtypes. Variability in ecosystem properties among black spruce stands was as large as that documented previously among all forest types in the central interior of Alaska. The variability in plant community composition was at least as effective as environmental or abiotic factors and stand characteristics as a predictor of soil C pools in the black spruce forest type of interior Alaska. The variability in species composition at the community subtype-level was related to a combination of environmental factors and fire history. Together, these results provide a foundation for future work in black spruce ecosystems of interior Alaska, and contribute to our understanding of the regional variability and biodiversity of the black spruce forest type.* *This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation). The CD requires the following system requirements: Adobe Acrobat.
• #### Systematics and biogeography of the arctic and boreal species of Primula

Four sections of the genus Primula are represented in northern North America: Aleuritia, Armerina, Crystallophlomis, and Cuneifolia. In this dissertation I discuss anatomical, morphological, cytological, ecological, and reproductive characters for thirteen species, and demonstrate coherence of sectional groups through cluster analysis and ordination. In Primula, distyly and homostyly play critical roles in systematics and biogeography. It is generally assumed that distylous individuals are almost completely outcrossed, and homostyles are capable of selfing. In the taxa examined here, distyly exists at the diploid and tetraploid levels while homostyly is seen in both diploids and higher polyploids. I suggest that distyly breaks down with selection for reproductive assurance in environments where pollinators are unreliable, or following hybridization in conjunction with polyploidy. While most northern Primula species are homostylous, several examples of distylous taxa demonstrate that this can be a successful breeding system in higher latitudes. In homostyles, self-compatibility and the proximity of reproductive organs assures a high degree of selfing; however, most northern homostylous taxa also exhibit attributes which suggest facultative outcrossing is common. In North America, evolution in Primula has been strongly influenced by Quaternary events leading to isolation, migration, and secondary contact of gene pools, in association with the breakdown of distyly to homostyly. The success of homostylous taxa is at least partially due to their ability to self-fertilize coupled with the availability of areas to colonize when Pleistocene ice retreated. The phytogeographic affinities, cytology, and reproductive shifts of Primula make it a useful model for processes occurring in the Alaskan flora. The steppes and mountains of Asia have been important source areas, and migration has taken place along mountains, rivers, island arcs, and coastlines. Speciation in the genus has been aided by hybridization, polyploidy, and reproductive diversity.