<p> Although dawn and dusk periods comprise a relatively small part of the day, their importance as key ecological transition periods has been recognized for some time. Previous marine investigations into this transition have focused on tropical locations and have mostly been qualitative in nature. This project focused on the dusk period in sub-tropical reef fish communities off the coasts of North and South Carolina. High-definition underwater video was collected in 2013 and 2014 at a variety of sites featuring natural live-bottom habitat. Independent samples (43 videos) were obtained on 17 sampling dates. Fishes were tallied by time relative to sunset (TRTS) in an effort to identify temporal abundance patterns and categorize taxa by temporal niche. Sufficient data were collected for statistical analysis of 27 taxa, representing 15 families. Analyses explored whether there was a relationship between time and abundance. Of the taxa analyzed, ten showed no temporal pattern during the dusk period, seven showed abundance peaks during dusk, and ten showed declines in abundance during dusk. Patterns were not always consistent within families. In particular, the Serranidae and Sparidae families featured a variety of patterns. Uncommon species and ephemeral behavioral events were also noted and described.</p>

<p> High-spatial resolution measurements of vegetation structure are needed for improving understanding of ecosystem carbon, water and nutrient dynamics, the response of ecosystems to a changing climate, and for biodiversity mapping and conservation, among many research areas. Our ability to make such measurements has been greatly enhanced by continuing developments in remote sensing technology&mdash;allowing researchers the ability to measure numerous forest traits at varying spatial and temporal scales and over large spatial extents with minimal to no field work, which is costly for large spatial areas or logistically difficult in some locations. Despite these advances, there remain several research challenges related to the methods by which three-dimensional (3D) and spectral datasets are joined (remote sensing fusion) and the availability and portability of systems for frequent data collections at small scale sampling locations. Recent advances in the areas of computer vision structure from motion (SFM) and consumer unmanned aerial systems (UAS) offer the potential to address these challenges by enabling repeatable measurements of vegetation structural and spectral traits at the scale of individual trees. However, the potential advances offered by computer vision remote sensing also present unique challenges and questions that need to be addressed before this approach can be used to improve understanding of forest ecosystems. For computer vision remote sensing to be a valuable tool for studying forests, bounding information about the characteristics of the data produced by the system will help researchers understand and interpret results in the context of the forest being studied and of other remote sensing techniques. This research advances understanding of how forest canopy and tree 3D structure and color are accurately measured by a relatively low-cost and portable computer vision personal remote sensing system: 'Ecosynth'. Recommendations are made for optimal conditions under which forest structure measurements should be obtained with UAS-SFM remote sensing. Ultimately remote sensing of vegetation by computer vision offers the potential to provide an 'ecologist's eye view', capturing not only canopy 3D and spectral properties, but also seeing the trees in the forest and the leaves on the trees.</p>

No description available.

<p> Stocking of trout into naturally fishless water bodies in the mountains of western North America has reduced populations of many native species in those systems, with benthic aquatic invertebrates being particularly impacted. Although bats are known consumers of emergent aquatic insects, almost no studies have focused on how changes to these prey populations at lakes subsequent to trout stocking could affect them. This study assessed bat activity, foraging activity, and foraging rate at nine feature-matched pairs of stocked and unstocked high elevation lakes in the central Sierra Nevada mountains in an effort to determine which provide higher quality foraging habitat for bats. Bats in the 25 kHz and 50 kHz echolocation call categories showed little to no behavioral change between lakes with trout and lakes without. In contrast, bats in the 40 kHz group had higher levels of activity at stocked lakes, which may indicate that at those lakes bats are consuming numerous small insects. If this is the case, it could represent a cost to those bats due to the lower energetic return of small prey items compared to the preferred prey species. </p>

<p> Wildlife management is challenged with addressing human resource needs while simultaneously conserving wildlife populations. Conflicts between humans and wildlife have increased across Northern countries with the expansion of human communities and environmental changes. Lack of information exists about reasons for such occurrences. This study explores adaptive capacity and resilience in coupled human-wildlife systems through the analysis of social and ecological factors contributing to perceptions of negative and positive human-bear (<i> Ursus</i> spp.) encounters. I first developed a theory to evaluate human perceptions and behaviors during human-wildlife encounters. Secondly I adopted an interdisciplinary framework to analyze human-bear encounters in urbanizing regions of south Sakhalin Island, Russian Far-East, and southcentral Alaska, USA. These case studies facilitate an analysis of perception development across spatial and social scales while incorporating approaches of both social and ecological sciences. Hunting, tourism and overall anthropogenic impacts are central to bear management, whereas cultural and social interests are perceived to not be considered in bear management decision-making across study regions. In Alaska, political interests are prevalent in bear management, whereas on Sakhalin, economic interests, including illegal animal trade and poaching prevail. Across study regions the perception of an encounter with a bear was dependent on the socio-economic situation of the individual having the encounter. The higher a person's socio-economic status was, the higher was their probability to perceive bear encounters as positive. Further, spatial and social scales across which perceptions vary are identified. Scales include urban-non-urban areas, wildland-urban interfaces, and a recreation-subsistence interest divide. Outside of urban areas, people's interests in recreation versus subsistence affect their perceptions toward bear encounters. Subsistence collectors of fish, game or plants are more likely to have negative encounters. Within urban areas, increased experience with encountering bears and length of residency are associated with positive encounters, whereas closeness to residences while not in sheltered environments increases negative encounters. These findings constitute spatial and social barriers and benefits to individualistic perception formation during human-bear encounters. Their identification advances resilience in researched human-wildlife systems and helps us to understand the adaptive capacities within these communities. The successful spatially-explicit integration of social and ecological variables promotes the opportunities for integrating human dimensions in wildlife management.</p>

<p> Chinook salmon (<i>Oncorhynchus tshawytscha</i>) are critical to subsistence and commerce in the Yukon River basin, but several recent years of low abundance have forced devastating fishery closures and raised urgent questions about causes of the decline. The Chena River subpopulation in interior Alaska has experienced a decline similar to that of the broader population. To evaluate possible factors affecting Chena River Chinook salmon productivity, I analyzed both population data and the behavior of individual fish during the summer they spend as fry drift feeding in the river. Using a stereo pair of high definition video cameras, I recorded the fine-scale behavior of schools of juvenile Chinook salmon associated with woody debris along the margins of the Chena River. I developed a software program called VidSync that recorded 3-D measurements with sub-millimeter accuracy and provided a streamlined workflow for the measurement of several thousand 3-D points of behavioral data (Chapter 1). Juvenile Chinook salmon spent 91% of their foraging attempts investigating and rejecting debris rather than capturing prey, which affects their energy intake rate and makes foraging attempt rate an unreliable indicator of foraging success (Chapter 2). Even though Chinook salmon were schooling, some were highly territorial within their 3-D school configurations, and many others maintained exclusive space-use behaviors consistent with the population regulatory effects of territoriality observed in other salmonids (Chapter 3). Finally, a twenty-year population time series from the Chena River and neighboring Salcha River contained evidence for negative density dependence and a strong negative effect of sustained high summer stream discharge on productivity (Chapter 4). The observed territoriality may explain the population's density dependence, and the effect of debris on foraging efficiency represents one of many potential mechanisms behind the negative effect of high stream discharge. In combination, these findings contribute to a statistically and mechanistically plausible explanation for the recent decline in Chena River Chinook salmon. If they are, in fact, major causes of the decline (other causes cannot be ruled out), then we can be tentatively hopeful that the population may be experiencing a natural lull in abundance from which a recovery is possible. </p>

<p> I estimated patterns of shorebird abundance and species diversity in the Colorado River Delta and Upper Gulf of California wetlands in order to determine the relative contribution of intertidal wetlands and non-tidal anthropogenic wetlands to support shorebird habitat use. Species richness varied from 15 to 26 species among sites and 29 species were detected across sites. Density during the peak migration month was higher at the anthropogenic wetland Cienega de Santa Clara (mean = 168 ind/ha, 95% C.I. 29-367), and the intertidal Golfo de Santa Clara (mean = 153 ind/ha, 95% C.I. 17-323). Anthropogenic wetlands (playa and lagoons) supported high abundance of shorebirds along with intertidal wetlands in the Colorado River Delta (mudflats). In contrast, intertidal wetlands farther south on the Sonoran Coast presented lower abundance but higher diversity of shorebird, likely as a result of the higher diversity of habitats (rocky shore, sandy beach, estuary). I modeled water management scenarios for the Cienega in order to determine the response of the dominant vegetation (southern cattail, <i>Typha domingensis</i> Pers.) and the area of the outflow pool below the marsh to different scenarios of water management. The model indicates that if the inflow rate is reduced below the current 4-5 m³ s^-1 the vegetated area of the Cienega that supports habitat for marsh birds would decrease in proportion, as would the area of the outflow pool in the Santa Clara Slough identified previously as shorebird habitat. Increases in salinity will also reduce the vegetated area due to the low salt tolerance of <i>T. domingensis</i>. In winter about 90% of inflow water exits the Cienega into the Santa Clara Slough due to low evapotranspiration contributing to inundate areas that are used by wintering and migrating shorebirds. Lastly, I explored the feasibility of using Vegetation Indices (NDVI and EVI) to model Yuma Clapper Rail detections in the Cienega de Santa Clara as well as the effects of adding other habitat variables and the presence of fire events in the performance of linear models based on NDVI. Both NDVI and EVI were positively related to the Yuma Clapper Rail detections. The relationship was weak to moderate, but significant (P &lt; 0.001), which suggests other factors besides the vegetation condition play an important role in the bird distribution pattern. A model including all the variability among years was a better predictor of the rails detected per transect, than models for fire and non-fire years. We did not find a significant effect from adding habitat features (water % or vegetation %), and we recommend to include variables at both microhabitat level and landscape level, relevant before and during the breeding season in order to increase the explanatory power of models.</p>

<p>Over the past five to ten years, public interest in nuclear energy, decommissioning, and waste management and stewardship has increased, leading to a renewed interest in radioecology (Kuhne 2012), or the study of the relationships between ionizing radiation and the environment (Whicker and Shultz 1982a). Several groups supporting collaborative radioecological research have recently been established, including the European Radioecology ALLIANCE in 2009 (Hinton et al. 2013), the Strategy for Allied Radioecology (STAR) network in 2011 (Kuhne 2012), and the National Center for Radioecology (NCoRE) in the United States in 2011 (Kuhne 2012). The earthquake, tsunami, and subsequent nuclear accident at Fukushima in March of 2011 further emphasized the importance of radioecology in providing timely and technically sound information (such as the transport and fate of radionuclides, potential doses and risks, etc.) for decision making in emergency response as well as in clean up and recovery (Kuhne 2012; Hinton et al. 2013) for both humans and their environment. Although the original and primary aims of the ICRP radiation protection recommendations have been to prevent deterministic effects and minimize stochastic effects to human beings from radiation exposure, the protection framework has recently been extended to include protecting the environment from harmful effects of radiation as well (ICRP 2007, 2008b, 2009). Radioecology is an interdisciplinary science that encompasses a wide array of topics, including, among others, radiation transport, effects, risk assessment, and remediation (Whicker and Shultz 1982a; Hinton et al. 2013). I consider two topics from different areas of radioecology in this dissertation: radionuclide uptake and dosimetry as well as an assessment of a technique for potential use in remediation. Part 1 outlines the development of empirical and computational models for prediction of activity concentration and subsequent radiation dose, respectively, in relevant rainbow trout (Oncorhynchus mykiss) organs for selected radionuclides. Radiation dose rates to biota are typically approximated utilizing dose conversion factors (DCF), which are values for absorbed dose rate per activity concentration in the body or organ (i.e. mGy d-1 per Bq g-1). The current methodology employed by both the International Commission on Radiological Protection (ICRP) and within the Environmental Risks from Ionizing Radiation in the Environment (ERICA) Integrated Approach for calculating dose conversion coefficients is to use Monte Carlo modeling of a homogenously distributed radionuclide within an ellipsoidal phantom chosen to represent a particular organism. However, more accurate estimates can be made based on specific absorbed fractions and activity concentrations. The first study in Part 1 examines the effects of lake tropic structure on the uptake of iodine-131 (131I) in rainbow trout and considers a simple computational model for the estimation of resulting radiation dose. Iodine-131 is a major component of the atmospheric releases following reactor accidents, and the passage of 131I through food chains from grass to human thyroids has been extensively studied. By comparison, the fate and effects of 131I deposition onto lakes and other aquatic systems has been less studied. In this study we reanalyze 1960s data from experimental releases of 131I into two small lakes and compare the effects of differences in lake trophic structures on 131I accumulation in fish. The largest concentrations in the thyroids of trout (Oncorhynchus mykiss) may occur from 8 to 32 days post initial release. DCFs for trout for whole body as well as thyroid were computed using Monte Carlo modeling with an anatomically-appropriate model of trout thyroid structure. Activity concentration data was used in conjunction with the calculated DCFs to estimate dose rates and ultimately determine cumulative radiation dose (Gy) to the thyroids after 32 days. The estimated cumulative thyroid doses at 32 days post-release ranged from 6 mGy to 18 mGy per 1 Bq mL-1 of initial 131I in the water, depending upon fish size. The subsequent studies in Part 1 seek to develop and compare different, increasingly detailed anatomical phantoms for O. mykiss for the purpose of estimating organ radiation dose and dose rates from 131I uptake and from molybdenum-99 (99Mo) uptake. Model comparison and refinement is important to the process of determining both dose rates and dose effects, and we develop and compare three models for O. mykiss: a simplistic geometry considering a single organ, a more specific geometry employing anatomically relevant organ size and location, and voxel reconstruction of internal anatomy obtained from CT imaging (referred to as CSUTROUT). Dose Conversion Factors (DCFs) for whole body as well as selected organs of O. mykiss were computed using Monte Carlo modeling, and combined with the empirical models for predicting activity concentration, to estimate dose rates and ultimately determine cumulative radiation dose (?Gy) to selected organs after several half-lives of either 131I or 99Mo. The different computational models provided similar results, especially for organs that were both the source and target of radiation (less than 30% difference between estimated doses). Although CSUTROUT was the most anatomically realistic phantom, it required much more resource dedication to develop than did the stylized phantom for similar results. Additionally, the stylized phantom can be scaled to represent trout sizes whereas CSUTROUT cannot be. There may be instances where a detailed phantom such as CSUTROUT is appropriate, as it will provide the most accurate radiation dose and dose rate information, but generally, the stylized phantom appears to be the best choice for an ideal balance between accuracy and resource requirements. Part 2 considers the use of reflectance spectroscopy as a remediation tool through its potential to determine plant stress from metal contaminants. Reflectance spectroscopy is a rapid and non-destructive analytical technique that may be used for assessing plant stress and has potential applications for use in remediation. Changes in reflectance such as that due to metal stress may occur before damage is visible, and existing studies have shown that metal stress does cause changes in plant reflectance. The studies in Part 2 further investigate the potential use of reflectance spectroscopy as a method for assessing metal stress in plants. In the first study, Arabidopsis thaliana plants were treated twice weekly in a laboratory setting with varying levels (0 mM, 0.5 mM, or 5 mM) of cesium chloride (CsCl) solution, and reflectance spectra were collected every week for three weeks using an ASD FieldSpec Pro spectroradiometer with both a contact probe and a field of view probe at 36.8 and 66.7 cm above the plant. As metal stress is known to mimic drought stress, plants were harvested each week after spectra collection for determination of relative water content and chlorophyll content. A visual assessment of the plants was also conducted using point observations on a uniform grid of 81 points. Two-way ANOVAs were performed on selected vegetation indices (VI) to determine the significance of the effects of treatment level and length of treatment. Linear regression was used to relate the most appropriate vegetation indices to the aforementioned endpoints and to compare results provided by the three different spectra collection techniques. One-way ANOVAs were performed on selected VI at each time point to determine which, if any, indices offered a significant prediction of the overall extent of Cs toxicity. Of the 14 vegetation indices considered, the two most significant were the slope at the red edge position (SREP) and the ratio of reflectance at 950 nm to the reflectance at 750 nm (R950/R750). Contact probe readings and field of view readings differed significantly. Field of view measurements were generally consistent at each height. The second study investigated the potential use of reflectance spectroscopy as a method for assessing metal stress across four different species of plants, namely Arabidopsis thaliana, Helianthus annuus, Brassica napus var. rapa, and Zea mays. The purpose of this study was to determine whether a quantifiable relationship exists between reflectance spectra and lithium (Li) contamination in each species of plant considered, and if such a relationship exists similarly across species. Reflectance spectra were collected every week for three weeks using an ASD FieldSpec Pro Spectroradiometer with a contact probe and a field of view probe for plants treated twice weekly in a laboratory setting with 0 mM or 15 mM of lithium chloride (LiCl) solution. Plants were harvested each week immediately after spectra collection for determination of relative water content and chlorophyll content. Linear regression was used to relate the most appropriate vegetation indices (determined by the Pearson correlation coefficient) to the aforementioned endpoints and to compare results provided by the different spectra collection techniques. Two-way ANOVAs were performed on 12 selected vegetation indices (VI) for each species individually to determine the significance of the effects of treatment level and length of treatment on a species basis. Balanced ANOVAs were conducted across all species to determine significance of treatment, time, and species. LiCl effects and corresponding reflectance shifts were significant for A. thaliana, but Z. mays and H. annuus showed little response to LiCl at the treatment level considered in this study, with no significant differences in relative water content or chlorophyll content by treatment level. B. rapa reflectance spectra responded similarly to Li exposure as Z. mays, but B. rapa did have significant differences in relative water content by treatment level. All species demonstrated a potential stimulatory effect of LiCl, with at least one week of increased reflectance in the near-IR. Different VI proved to be the best predictor of endpoint values for each species, with only SIPI and the ratio of reflectance at 1390 nm to the reflectance at 1454 nm (R1390/R1454) common between species. The most significant VI considering all species together was SIPI, although A. thaliana effects dominate this result. VI determined separately by CP and FOV were occasionally well-related, but this relationship was inconsistent between species, further supporting the conclusion in the previous study that CP and FOV are not interchangeable. These techniques should either be used as compliments or independently, depending on the application.

<p> Abstract not available.</p>

<p> Recent research has revealed a trend of decreasing pollinator abundance and diversity in regions throughout the world. This highlights the need to understand factors influencing patterns in bee community structure and the drivers of bee diversity and abundance patterns. My dissertation uses several methods to determine factors structuring bee communities with regards to diversity and abundance. I selected 10 sites in different regions of the Central Valley of California that differ with regards to land use and floral diversity. Bee communities at each site were sampled for diversity, abundance, and bee-floral host relationships. </p><p> Sampling bee communities is often done using only bee bowls because netting is time consuming and prone to sampler bias. In chapter one the methods used in this study were detailed and the use of bee bowls and netting in capturing a representative sample of the bee community were compared using the S&oslash;rensen's similarity index and the Bray-Curtis dissimilarity index. It was determined that sampling using one method alone would miss approximately 40% of the species richness of the community. Further, there were biases in using bee bowls and nets; the bee bowls sampled certain species more than nets and vice versa. This chapter provides evidence that to adequately sample a bee community both bee bowls and netting must be used. </p><p> Chapter two focuses on bee biodiversity and the correlation between bee species richness and plant diversity. Patterns of diversity in bee communities of the Central Valley indicate that the family Apidae was more speciose than other families. However, on a species level, those from the family Halictidae far exceeded species from Apidae in abundance. This could have reflected a sampling bias given that pan traps tend to sample individual bees from Halictidae more than Apidae. Chapter two also focused on temporal variability. There was considerable temporal variability in the abundance of one of the more abundant species, <i>Lasioglossum incompletum.</i> This highlighted the need for studies of longer duration in order to account for natural stochasticity in bee populations. Several different diversity indices were used to assess the biodiversity of the different study locations; Putah Creek sites were found to be more diverse than the San Joaquin sites. A correlation analysis was used to determine that a positive relationship between plant diversity and bee species richness did exist for 2005 but not 2006. This indicated that plant diversity may be one of the factors driving bee species richness and community structure. </p><p> Another factor possibly accounting for variation in bee species richness and abundance is land use. Chapter three used non-metric multidimensional scaling and generalized linear mixed effects model to test for associations between differences in land use patterns and bee species richness and abundance. While there was no direct association between these factors, the ordination did show that the Putah Creek sites, San Joaquin sites, and Cosumnes sites clustered together. Therefore, sites that shared similar land-use patterns were related along a gradient. These cluster patterns were used to group the study locations for the other analyses performed in this project. The Putah Creek sites were characterized by agriculture and urban land use whereas, San Joaquin was semi-natural and Cosumnes Preserve was semi-natural and agricultural. </p><p> Chapter four is an analysis of the pollinator networks of Putah Creek, San Joaquin, and the Cosumnes Preserve. Pollination webs, matrices, and gplots were used to visualize the networks, while network and species-level indices were used to assess asymmetry, specialization versus generalization, and connectance. It was determined through these analyses that the connectance of the network decreased with increasing species richness and the complexity and composition of the network varied between the three regions of the Central Valley. Further, the San Joaquin Refuge sites, which were characterized as seminatural land use, contained a higher number of oligolectic species than other sites dominated by agricultural and urban land use. </p><p> The focus of this project was to use different methods to determine drivers of bee species diversity and abundance in different bee communities of the Central Valley of California. Three conclusions can be drawn from the analyses presented; 1) Given temporal variability in bee populations, studies of longer duration must be conducted to determine factors affecting bee community structure from that of natural population variability, 2) Floral diversity is positively correlated with bee species diversity and abundance but it is not the only factor influencing bee community structure. and 3) Land use change may be a factor influencing bee-plant networks but studies that compare networks across space and time are needed to determine the nature of this relationship. </p>