In most temperate coniferous forests, the vast majority of vascular plant species richness can be found in the understory layer. While the large-scale conversion of forests to plantations has made it increasingly important to understand how understory . . .

Russian Peak, at an elevation of 8200 feet, is situ­ated in the Salmon Mountains, a north-south trending range centrally located within the Klamath Region of northwest­ern California. The Salmon Mountains are drained by the Scott River on the east and . . .

Harbor seals have been listed as a species likely to benefit from new Marine Protected Areas (MPAs) in California as part of the Marine Life Protection Act. Whereas seals may experience direct and indirect effects from these MPAs as a whole, the impac . . .

Five species of western gooseberries (Ribes: Grossulariaceae) hybridize to varying degrees in northwestern California and southwestern Oregon. Pollinator surveys and hand-pollination experiments were conducted to identify reproductive barriers between . . .

Disturbances such as wildfire play a major role in the diversity, structure, and composition of plant communities, however, little is known about the differential impacts of fire across landscapes that vary in characteristics such as soil nutrients an . . .

Spotted fever group (SFG) rickettsiae have been shown to cause many human and animal diseases. SRG rickettsial phylotypes G021 and G022 were recently detected in Ixodes pacificus ticks from Napa and California using quantitative real time polymerase c . . .

The dominant plant in Humboldt Bay salt marshes is Spartina densiflora, a species of cordgrass apparently introduced from South America. At several salt marshes and restoration sites around Humboldt Bay, distribution of this plant has increased signif . . .

Numerous studies have analyzed the effect of habitat fragmentation on plant pollinators and herbivores. These studies describe the decrease in pollinator services and seed set in small and isolated patches due to pollinator preference for large, conti . . .

The genus Ribes displays extensive floral diversity. The pollinator shift model suggests that such diversity is an outcome of species shifting to specialize on new pollinators. To test this model, I surveyed the flower visitors of 14 Ribes species at . . .

For over a century, increases in the abundance of woody plant species in savannas have been occurring worldwide, and this woody plant encroachment directly threatens the existence of savanna ecosystems. Savannas are known for their striking compositio . . .

The disease chytridiomycosis has caused population declines in hundreds of amphibian species worldwide, and is caused by the pathogenic fungus Batrachochytrium dendrobatidis (Bd). One promising method to combat the disease is to augment the amphibian’ . . .

Studying the impacts on a community following the introduction of an exotic species is of increasing importance in the field of marine science. Recent investigations of marine biological invasion have primarily focused on studying the negative interac . . .

Humboldt Bay, in far northern California receives a large amount of sediment, predominantly silts and clays from the surrounding watersheds at an estimated 62,532 metric tons/yr. (Barrett 2004). Fine grained sediments such as silts and clays have a hi . . .

Populations of flying squirrels occupying oak and oak-pine forests of the Mesoamerican highlands represent the least studied and most poorly known members of the genus Glaucomys. Traditionally, these Mesoamerican populations have been considered to be . . .

Increased suspended sediment inputs to streams as a result of human activities and disturbance have been identified as a principle source of stream impairment. Allochthonous energy inputs to riverine food webs, in the form of terrestrial leaf litter, . . .

The Great Gray Owl (Strix nebulosa) is listed as a State of California endangered species due to their low population of approximately 100 individuals. Annual surveys and long-term monitoring efforts are frequently conducted to determine the status of . . .

Genetic structure and diversity of populations can impact the productivity and resilience of ecosystems. In Humboldt Bay, California (USA) eelgrass (Zostera marina) is the dominant marine plant at low intertidal and shallow subtidal elevations where i . . .

Napa County is located within a global biodiversity hotspot, and is one of ten localized areas in California that contain the highest numbers of native and endemic plant species. Conservation of rare taxa is an important issue and the research present . . .

Bat migration ecology is an important, yet understudied facet of natural history and conservation. We know little about the movement patterns of migrating bats and the physiological demands that bats experience in preparation for and during migration. . . .

The southern distribution of the northern red-legged frog (Rana aurora) extends only into the three most northern coastal counties of California and seems to be restricted to the coastal belt. Because of recent declines in the population and destructi . . .

In forests native pathogens accelerate tree decline, increase stand structural heterogeneity, and alter tree community composition. In northern California, white fir (Abies concolor var. lowiana) and Douglas-fir (Pseudotsuga menziesii var. menziesii) . . .

Riffle sections of eight streams in northern California were sampled for aquatic insects using a kick net. Eleven chemical and physical stream parameters were measured at each riffle sampled. Biological data was analyzed using Simpsons diversity index . . .

The North East Pacific coastline is a diversity hotspot for many marine organisms, including seaweeds, which live in complex habitats influenced by tectonics, glaciation, and ocean circulation. This is the first study to thoroughly survey population g . . .

Over the past several years, ecologists have begun to recognize that the role played by positive plant-plant interactions, specifically facilitation, in communities is under appreciated. Despite this recognition, little is known about how these positi . . .

As populations of a species decline, an understanding of habitat use and regional variation in population health can aid in focusing conservation efforts. Western Pond Turtle (Actinemys marmorata) populations have declined throughout much of their ran . . .

Point count and species-specific surveys are widely used to infer avian abundance and species richness. However, advancements in bioacoustic technology enable automated survey alternatives that can expand the landscape coverage with equivalent personn . . .

Although many studies have investigated the effect of invasive plants on native plant species, few studies have considered their effect on pollination success. Since invasive plants potentially compete with native plants for pollinator services, the f . . .

Forest stands occurring on coastal dunes along the western margin of Humboldt Bay, California are isolated fragments of a regional forest type that stretches discontinuously along the Pacific Coast from northern California to Alaska. I used aerial pho . . .

Marine fouling communities contain a plethora of sessile colonial invertebrates. These invertebrates come in many different shapes which occupy space and compete for resources in different ways. It has been theorized that these organisms be placed int . . .

Ultramafic parent materials in northern California and southwestern Oregon have given rise to one of the largest serpentine regions in the world. This area is dominated by sparse, fire-prone coniferous forests and shrublands which are apparently highl . . .

Due to the many misconceptions about science and the general lack of scientific literacy in our society, there is a need to better distribute accurate, comprehensible scientific ideas in an engaging way. Science education films can be powerful tools i . . .

The Oregon spotted frog (Rana pretiosa), endemic to the Pacific Northwest, was once considered widespread in complex, warm water wetlands. Over 70% of historic populations are thought to be extirpated with range-wide habitat loss exceeding 90%. Using . . .

Bees (Hymenoptera) represent one of the primary pollinators in most natural and managed ecosystems world-wide. Current concerns for a global decline in bee populations emphasize the need to better understand the factors that shape bee communities. Alt . . .

Understanding the effects of biotic and abiotic pressures on commercially important marine species is crucial to their successful management. The red abalone (Haliotis rufescensis) is a commercially important mollusc, whose shell surface is frequently . . .

This work is a taxonomic study of nine species in the ectomycorrhizal fungal family Boletaceae (Basidiomycota) from Neotropical rainforests of Guyana, in northeastern South America. Morphospecies collections from the following genera were studied: Tyl . . .

Diaulula sandiegensis (Cooper, 1862), a northern Pacific nudibranch, has considerable phenotypic variation in dorsal spotting pattern throughout its range. Experiments were conducted to test the possibility that D. sandiegensis is a complex of unrecog . . .

Spotted Fever Group (SFG) Rickettsiae are important zoonoses affecting both people and dogs. Rocky Mountain spotted fever (RMSF) caused by Rickettsia rickettsii, is the most well-known zoonotic SFG; historically in California cases were identified fro . . .

Predictions of low genetic variation and low levels of inbreeding depression in small plant populations were tested on Astragalus agnicidus, a species with only one known population. Loss of alleles through drift and increased inbreeding (followed by . . .

In 1992 the rapidly developing demand for taxol led to consideration of a possible Pacific yew harvest in northwestern California. Deer browsing has prevented regeneration of Canada yew in some areas. Knowing that deer populations have been high in th . . .

Desert water courses are topographically distinct features with periodic flooding, which are floristically rich and structurally complex. This study was undertaken to determine if plant species and vegetation types change along desert water courses as . . .

Nearly all animals are able to detect forms of chemical stimuli. In amphibians, chemoreceptive capabilities are used in a wide variety of contexts, including the detection of predators, conspecifics, and food. The focus of this project was the use of . . .

Boiling Springs Lake is a pristine, oligotrophic, acidic hot spring in Lassen Volcanic National Park. In 2008, 25 isolates from BSL were tested for resistance to 14 different antimicrobial compounds or a sub-set of the 14 antimicrobial agents. All iso . . .

Eight species of the ectomycorrhizal (ECM) genus Sarcodon (Bankeraceae, Thelephorales, Basidiomycota) are described as new to science. Sarcodon quercophilus, and Sarcodon umbilicatus are described from Quercus (Fagaceae) cloud forests within the Maya . . .

Habitat fragmentation can have negative effects throughout an ecosystem, but its impact is dependent on the spatial scale at which community members respond to the environment. Because solitary bees are central-place foragers, their access to floral r . . .

Oct4 is a POU class V transcription factor that functions to maintain the pluripotent state of embryonic stem cells by activating or repressing the transcription of hundreds of target genes (Boyer et al. 2005). Aberrant expression of Oct4 has been rep . . .

Determining the factors that shape arthropod communities has a long history in ecology. I examined the direct and indirect effects of nitrogen availability on plant productivity and plant community composition to assess their effects on arthropod comm . . .

Many turtle species require aquatic and terrestrial habitats during different times in their life history for foraging, mating, nesting, estivation and overwintering. The status of many turtle populations depends directly on the condition of both envi . . .

This study examined changes in Sequoia sempervirens foliage along gradients of height and light availability. In tall trees (108-113 m), shoot morphology and physiology were analyzed at the base of the live crown, the mid-crown, and treetop. Both ligh . . .

The South Fork Trinity River is an undammed river in Northern California that drains a watershed with a long history of varied anthropogenic uses including mining, logging, cattle grazing, and associated road construction. These activities modify ripa . . .

In this study, I examined the effects of FMRFamide on the isolated crop-gizzard of the earthworm, Lumbricus terrestris. The peptide induced contractions of both the longitudinal and circular muscles of the crop-gizzard at concentrations examined (10-9 . . .

The relationship between eelgrass bed characteristics and animal use is important in better understanding what the optimal habitat features are for specific taxa. The focus of this study was to look at structural and geographical aspects of eelgrass h . . .

Different loci within a multigene family often experience unique evolutionary pressures; this phenomenon is often observed in proteins involved in reproduction. Chemical communication using secreted proteinaceous pheromones is critical for reproductiv . . .

A total of 17 transgenic strains of Caenorhabditis elegans were evaluated for use as bioindicators for the presence of toxins in an environmental sample. Every strain used had Green Fluorescent Protein (GFP) production driven by the promoter region of . . .

The tallest tree species, coast redwood (Sequoia sempervirens), provides an ideal model for investigating both the adaptations allowing maximum height growth in plants and the factors that limit it. Within the crowns of tall redwoods there exists broa . . .

A number of isolated high temperature, low pH geothermal sites exist in Lassen Volcanic National Park (LVNP) and Hawai’i Volcanoes National Park (HVNP) that allow for the growth of thermoacidophilic microbial communities. Horizontal gene transfer (HGT . . .

This study examined how pollinator visitation and local neighborhood density may affect pollen limitation (PL) of reproductive success for Vancouveria chrysantha Greene (Berberidaceae), a rare plant, strictly endemic to serpentine substrates in northw . . .

A great effort has been made in the last few decades to restore and preserve coastal dunes in northwest California. The restoration effort has largely focused on removal of invasive plants, with little study on how invasive plant removal affects nativ . . .

Lithobates catesbeianus (American bullfrogs) are not native to states west of the Rocky Mountains. Since their introduction to California, they have been implicated in the decline of amphibian species. On California’s north coast, bullfrogs may be cau . . .

The following research addresses the question: does color vision occur in animals that can only see rudimentary images? Since the morphological and neurological requirements of color vision are minimal relative to those necessary for image formation, . . .

Boiling Springs Lake (BSL) is a 52˚C, pH 2, iron and sulfur-rich thermal feature in Lassen National Volcanic Park (California, USA). Previous community composition studies of small subunit rRNA and RuBisCo genes revealed an abundance of phylotypes clo . . .

Plecoptera (stoneflies) were collected during the spring emergence in the Willow Creek basin, Humboldt County, California. Both adults and nymphs were collected using qualitative methods. Water chemistry, substrate size, and riparian vegetation were u . . .

Nonpathogenic bacterial endosymbionts have been shown to contribute to their arthropod hosts’ fitness by supplying them with essential vitamins and amino acids. Little is known about the nutritional basis for the symbiotic relationship of endosymbiont . . .

Many conservation strategies for bats focus on supporting or enhancing their roosting and foraging needs. With increasing urbanization and loss of natural habitat, many species have adapted to roost in anthropogenic structures, resulting in increased . . .

Mytilus californianus beds along the wave-exposed coast of the eastern North Pacific Ocean serve as an important habitat, harboring a high diversity of species due to their colonizable hard surfaces as well as through the creation of microhabitats wit . . .

Habitat modeling techniques are widely used to determine where species occur on the landscape and what habitat or environmental factors influence their presence. These techniques are particularly useful for rattlesnakes, which have life history traits . . .

Humboldt Bay contains two populations of eelgrass; Zostera marina L., a sparse population in North Bay and a significantly denser population in South Bay. No study has attempted to determine the cause of this density difference despite the importance . . .

A population of Eumetopias jubatus and Zalophus californianus was studied during the summers of 1983 and 1984 on the coast of Humboldt County. The population of E. jubatus and Z. californianus peaked during June and August. Z. californianus numbers pe . . .

To obtain the most complete understanding of a species’ life history requirements, one must know what habitat characteristics and resources are critical to each life history stage. Rana boylii are known to associate with various stream habitats throug . . .

Coastal shrublands of Humboldt and Del Norte Counties, California were classified and described based on data from 140 plots sampled at 46 sites. Twinspan was used to separate plots into groups. Indicator species analysis was used to determine which s . . .

I describe the spatial and temporal distribution, abundance and habitat use of Steller sea lions (Eumetopias jubatus) in northern California between 2006 and 2011 obtained through shore and at-sea surveys and by tracking branded individuals. Understan . . .

The flowers of the California pitcher plant, Darlingtonia californica, are unusual and have been the subject of much speculation. Despite the efforts of several workers, the pollination ecology of this plant, including the identities of pollinators, r . . .

Coastal ecosystems are under intense pressure from anthropogenic and environmental factors in California. Human development, pollution and climate change continue to degrade coastal habitats. Marine predators such as marine mammals that depend on near . . .

Bioassessment utilizes biological assemblages to assess ecological condition in disturbed areas. The most popular quantitative evaluation of biological health in streams involves an Index of Biotic Integrity (IBI) for benthic macroinvertebrates (BMIs) . . .

Variation at mitochondrial D-loop sequences and microsatellite loci were studied in three sub-populations of recently introduced red foxes (Vulpes vulpes) in California. Red foxes were introduced separately in northern and southern California near the . . .

Bumble bees (Bombus: Apidae) can maximize foraging efficiency in a resource-patchy environment by visiting mainly rewarding flowers and avoiding those that are either empty or less rewarding. This study investigated how bumble bees avoid unrewarding f . . .

Analyzing DNA sequence data from multiple unlinked loci in a coalescent framework is a powerful means for assessing the genetic isolation of populations by estimating population divergence times and gene flow since divergence. This approach was used t . . .

The hoary bat is a migratory, foliage-roosting bat with a mostly solitary roosting habit. Little is known about the social interactions of this species, but as a solitary roosting bat, most interactions between conspecifics are thought to involve mati . . .

Populations of Rana aurora Baird and Girard (red-legged frog) and Rana catesbeiana Shaw (Bullfrog) were studied at Freshwater Lagoon from December 1990 through January 1991. Significant differences in habitat-use between species were confirmed using l . . .

A geographic information system allows for the ability to predict potential distributions of spreading non-native species by identifying suitable, unoccupied habitat. Zostera japonica (Asch. and Grabn.), a non-native seagrass from the subtropical west . . .

The Crescent City wastewater treatment facility services a small community on the northern coast of California, where treated wastewater is discharged into a rocky intertidal community. A biological assessment of the habitat was conducted to determine . . .

A growing body of literature supports the position that both natural habitat surrounding farms and high flowering crop diversity helps insure farms against pollination shortfalls and an overreliance on European honeybees. I assessed the importance of . . .

Various aspects of the ecology and natural history of Darlingtonia californica Torrey 1853, populations in northern California were studied as they relate to the species' reproductive biology. Experimental investigations of the breeding system to esti . . .

Floristic studies are especially timely since habitat loss is increasing dramatically. From the conservation perspective, it is imperative to document the distribution of plant species in areas that are floristically rich. For this study, I conducted . . .

Tetrapods began the water-to-land transition during the Devonian period, approximately 400 million years ago. To succeed in this new environment the sensory systems of the early terrestrial explorers underwent specific adaptations. A similar challenge . . .

My thesis is an inventory of invertebrate species found in the low region of a Humboldt Bay salt marsh during four seasons, from July 1999 to April 2000. Invertebrates are an integral part of the salt marsh, contributing to detritus breakdown and food . . .

The tropical monodominant tree Dicymbe corymbosa, vegetatively regenerates via epicormic shoots and roots, resulting in multi-stemmed trees with stabilizing pseudotrunks and root mounds. In two 1-ha forest plots on the Guiana Shield, we quantified the . . .

The Lassics lupine (Lupinus constancei T.W. Nelson & J.P. Nelson) is a rare herb of limited distribution, with fewer than 400 reproductive individuals restricted to a single square kilometer in the Lassics Geological and Botanical Area of the Six Rive . . .

Eight owl species of special concern occur in the Sierra Nevada: California Spotted Owl (Strix occidentalis occidentalis), Northern Spotted Owl (Strix occidentalis caurina), Long-eared Owl (Asio otus), Burrowing Owl (Athene cunicularia), Great Gray Ow . . .

Eleven vegetation types occurring within two communities have been described for the lakeshore habitat of the Sky Lakes area. The shrub-dominated community has two closely related heath shrub types. The herb-dominated community comprises a diversity o . . .

Tricostate mosses and associated bryophilous fungi from the early Two novel fossil mosses (Tricosta plicata gen. et sp. nov. and Krassiloviella limbelloides gen. et sp. nov.) and several fungal morphotypes associated with one of these mosses are descr . . .

This study explores nectar production in Scrophularia californica, a native California herbaceous perennial. I conducted a series of field experiments to determine whether S. californica can replenish nectar in response to extractions, whether the rat . . .

Hauling site fidelity, movement patterns, and the proportion of harbor seals hauling out were examined for one year by radiotagging 12 seals in the Klamath River, California. Hauling site fidelity was highest during the spring and summer months, with . . .