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Recent research conducted throughout the Northern California Current (NCC) on the ecology of Pacific salmon (Oncorhynchus spp.) indicates that variable ocean conditions affect the community composition ...
Citation Citation
- Title:
- Trophically transmitted parasites as ecosystem indicators : relationships among parasite community structure, juvenile salmon diet composition, and ocean conditions
- Author:
- Losee, James P.
Recent research conducted throughout the Northern California Current (NCC) on the ecology of Pacific salmon (Oncorhynchus spp.) indicates that variable ocean conditions affect the community composition of zooplankton in the nearshore environment which, in turn, can affect the quality of prey for fish, sea birds and mammals. Interannual variability in the quality and composition of the copepod community in the NCC during early marine residency of some Pacific salmon populations is related to survival to adulthood. However, copepods make up a small portion of the diet of coho and Chinook salmon, and the mechanistic linkages between ocean climate, zooplankton composition and salmon prey remain unclear. Parasite analysis provides a supplement to traditional diet analysis that can describe the foraging history of a host species. Coho salmon (O. kisutch) and Chinook salmon (O. tshawytscha) serve as hosts to an array of marine parasites acquired through consumption of infected intermediate hosts such as copepods, euphausiids, and planktivorous fishes. Causing little or no harm to their salmon host, the presence of trophically transmitted parasites provides information on the dietary history of their salmonid host beyond the 24 hours associated with traditional diet analysis. This study (1) examined differences in feeding behavior of coho and Chinook salmon during their early marine residency using both stomach and parasite community analyses and (2) tested the hypothesis that variability in ocean circulation patterns (measured through the Pacific Decadal Oscillation, sea surface temperature (SST) and Bakun's upwelling index) and copepod species composition are related to variability in the community structure of trophically transmitted marine parasites found in juvenile salmon. I compared the abundance and species composition of parasites recovered from juvenile Columbia River coho and upper Columbia River summer and fall Chinook salmon captured off the coast of Washington from 2002 to 2009. I also compared interannual variability in parasite assemblages to physical and biological indices of ocean conditions. Coho and Chinook salmon consumed similar prey taxa; however, the species richness and abundance of trophically transmitted parasites indicated that Chinook salmon consumed a greater diversity and abundance of infected prey. In addition, differences in the abundance of fish in the diet and Anisakis simplex, a parasitic nematode known to infect salmon through fish consumption, suggest that Chinook salmon consistently consumed more fish prey than coho. In contrast, coho appeared to consume more euphausiids as indicated by stomach content analysis and increased abundance of the euphausiid parasite, Rhadinorhynchus trachuri. Shifts in the parasite community composition of both coho and Chinook salmon were related to interannual variability in SST and the biomass of southern-origin copepods (r > 0.7, P < 0.05). The acanthocephalan R. trachuri and a tetraphyllid cestode were associated with "warm" SSTs and greater biomass of lipid-poor, subtropical copepods while the nematode A. simplex was more abundant in years of "cold" SST and a relatively low biomass of subtropical copepods. These results provide novel insight into differences in the diet of Columbia River coho and Chinook salmon and illustrate linkages between ocean climate, zooplankton community composition and salmon diet during early marine residency.
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1562. [Article] Conserving energy by environmentally acceptable practices in maintaining and procuring transmission poles for long service ; August 1987
This seventh annual report outlines our continued progress on each of six objectives. Improved fumigants: We continue to evaluate previously established field tests, which inlicate that chioropicrin continues ...Citation Citation
- Title:
- Conserving energy by environmentally acceptable practices in maintaining and procuring transmission poles for long service ; August 1987
- Author:
- Morrell, Jeffrey J., Oregon State University. Dept. of Forest Products, Corden, M. E. (Malcolm E.)
This seventh annual report outlines our continued progress on each of six objectives. Improved fumigants: We continue to evaluate previously established field tests, which inlicate that chioropicrin continues to protect Douglas-fir poles after 17 years and piling after 12 years. Vorlex treated poles are being gradually recolonized by decay fungi, while the Vapam treated poles appear to have little resistance to decay fungi. The latter poles were retreated last summer and will be used to determine the effectiveness of fumigant retreatment. Solid methylisothiocyanate (NIT) continues to protect Douglasfir poles, although the 20 percent NIT treatment has experienced slightly higher levels of colonization after 9 years. Additional tests to evaluate the effectiveness of gelatin encapsulated MIT or chioropicrin indicate that both chemicals continue to remain effective. In addition, there now appears to be little difference between the levels of control exhibited following addition of varying amounts of water to the poles along with gelatin encapsulated NIT. Closed tube bioassays indicate the chioropicrin remains at fungitoxic levels after 17 years, while no volatile fungitoxins appear to be present in Vapam or Vorlex treated wood. The evaluation of untreated Douglas-fir posts treated with NIT, chloropicrin, or Vapam indicate that fumigants can not ccatletely protect untreated wood in ground contact unless there is sane other type of preservative treated barrier present. Although the NIT treatment provided the best protection, all of the posts experienced some surface decay and termite attack after 10 years. These results appear similar to those found with more recent tests of posts treated with various coLthinations of preservative containing wraps and fuinigants. Evaluation of Mylone and tridipain, two solid chemicals that degrade to produce NIT, initcates that NIT production and fungal control are enhanced by the addition of basic pH buffers; however, only the pH 12 buffer resulted in rapid fungal control. These results Jnitcate that the rate of fumigant release can be tailored to control specific decay problems. We have also investigated the decomposition of Vapam in wood. As previously reported, there are over 14 potential deccmposition products from this chemical. This past year we developed methods for assaying these chemicals, evaluated the long-term stability of each, and prepared test blocks for evaluating decc*,osjtion in wood. In addition, we have studied the migration of volatile compounds from Vapam and NIT treated blocks under controlled aeration. After 5,000 hours, detectable levesis of NIT, carbon disulfide, and carbon oxysulfide are still present in air surrounding the Douglas-fir blocks. These tests indicate that low levels of volatile chemicals are continuously eninitted from fumigant treated wood. While this poses little difficulty for utility poles, it may pose some hazard for wood in closed spaces. Evaluations will continue until the emission levels decline below detectable limits. In addition to Vapam deccmposition studies, we have also evaluated the decoxrosition, movement and fungitoxicity of NIT under a variety of environmental conditions. In general, wet wood held less NIT, but the degree of control produced was more rapid. These results suggest that dry wood will act as a reseivoir of NIT, which will be released as moisture enters and swells the wood. This effect may provide an excellent long-term decay control strategy. The information from these studies will be used to develop more 111 ecific recaimrndations for fumigant treatment. Cedar Saood Decay Control: This past year we reestablished the field test of promising nei pentachiorophenol replacements, incorporating 26 chemicals into these tests. These saitles will be evaluated after 1 and 2 years to determine efficacy. In addition to the field test, we evaluated 13 new formulations or cinations of formulations in our laboratory screening tests. A nuner of chemicals including Isothiazolone, Amical 48 and a nurrer of quaternary aimnonium compounds appear promising and have been included in the field test. Bolt Hole Decay Prevention: Test established 5 years ago to determine the effectiveness of sprays, liquids or pastes applied to field drilled bolts holes indicate that airanonium bifluoride, Boracol 40, and 10% penta provided greater protection than Polybor or Patox washers. In addition, no evidence of corrosion was associated with any of the treatments. Fumigant treatments below the bolt holes continue to eliminate decay fungi, although samples removed from further down the pole indicate an incoIr)1ete distribution of MIT. These tests will be reevaluated this coming year. Detecting Early Decay and Estimating Residual Strength: We continue to evaluate the use of fluorescent coupled lectins and infra-red spectroscopy for detecting fungi in wood and early decay under controlled laboratory conditions. We have also continued evaluation of longitudinal compression (L) as a measure of ultite wood strength using a series of 27 Ldgepole pine posts. While the dense knot clusters interferred with the analysis, LCS, in combination with other parameters, was a reasonably good predictor of bending strength. These tests will continue with more uniform material. iv In addition to tests of LCS, we have evaluated the ability of small scal e tests to determine the strength of various wood pole connectors. Out results were in close agreement with those obtained using full scale tests aii illustrate the value of using small r1 e tests to develop strength information. Initiation of Decay in Air-Seasoning Douglas-fir: We continue to evaluate the data developed in the air-seasoning st1wies. This past year we began to develop information on the effects of various colony sizes on wood strength. This data will help us assign strength values to the colony size data we ha developed frau the air-seasoning study. At present, only Peniophora spp. has been tested, but . carbonica, P. placenta, and Haematostereum sanguinolentuin will also be included. Evaluation of the teinperatures required to eliminate fungi from Douglas-f ir poles also continue. We have ccatpleted 9 test charges which indicate that the penta treatmants involving a Boulton-seasoning cycle result in a ixre than adequate heating of the wood, while steam treants associated with amnniacal copper arsenate are nre variable. We feel that longer heating periods are required for poles greater than 12 inches in diamater, but that the current 6 hour steam period will result in heating of the center to 67 C for over 1 hour in smaller poles. Microfungi in Douglas-fir Poles: We continue to evaluate the effects of nticrofungi on properties of fumigant treated Douglas-fir poles. These tests indicate that prior colonization of fumigant treated wood by Scytalidium or Trichoderma species resulted in lower weight losses by P. placenta and . carbonica. Evaluation of a Cellon treated Douglas-fir laminated beam indicated that V severe penta depletion was associated with virtually all of the surface decay present. This beam had only been in service for 12 years in an extremely dry climate arxl it is unclear why the decay was so rapid.
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1563. [Article] Survival Assessment, Inactivation Kinetics Models, and Farm-to-Table Quantitative Risk Analysis of Food Pathogens
About 48 million cases of Foodborne illnesses (FBIs) are estimated to occur every year in the US. These are diseases caused by contamination of foods with bacteria, viruses, protozoa, parasites and toxic ...Citation Citation
- Title:
- Survival Assessment, Inactivation Kinetics Models, and Farm-to-Table Quantitative Risk Analysis of Food Pathogens
- Author:
- Deng, Kai
About 48 million cases of Foodborne illnesses (FBIs) are estimated to occur every year in the US. These are diseases caused by contamination of foods with bacteria, viruses, protozoa, parasites and toxic chemicals. Clostridium difficile infections (CDIs) are an important health-care and community associated problem. Since C. difficile spores have been frequently isolates from meat product, this pathogen should be considered an emerging food pathogen. Low temperature and reduced water activity (a[subscript w]) are commonly used methods to preserve meats and meat products. Chapter 3 covers studies on the viability of C. difficile spores during 4 months at -80°C, -20°C, refrigeration (4°C) and room temperature (20°C), and after ten freeze-thaw cycles (10 cycles). Two epidemic strains, R20291 (PCR ribotype 027, human isolate) and M120 (PCR ribotype 078, animal isolate), were used in this published study. At 20°C and -80°C, the spore viability of both strains declined with storage time. The viability of M120 spores also declined during storage at 4°C and 20°C. Although no significant changes were observed in the viability of R20291 spores stored at 4°C, their significant viability increase when stored at 20°C is most remarkable and raises food safety concerns. Finally, the viability of both strains decreased when subjected to ten freeze-thaw cycles. In summary, this study provides evidence that C. difficile spores can survive the room and low temperature conditions found in food processing, storage and distribution. Chapter 4 covers studies on the aw effect on the viability of C. difficile spores stored at room temperature. In addition to the spores of the strains previously described, spores of a food isolate strain, C. difficile DK1 (unidentified ribotype), were included in this study. The viability of their spores during 3 months at room temperature in phosphate buffer saline (PBS) at a[subscript w] of ~1.00, 0.82 and 0.72, and in commercial samples of beef jerky with a[subscript w] 0.82 and 0.72 was investigated. Spores of the strains M120 and DK1 showed a ~1 decimal reduction after 3 months in PBS kept at room temperature, while no significant changes in spore viability were observed in the reduced a[subscript w] beef jerky. The steady and significant 2 decimal increase in the viability of R20291 spores in PBS and ~1 decimal increase in the beef jerky during the 3-month storage raises again food safety concerns. This study provides evidence that beef jerky enhanced spore survival and viability during room temperature storage. Furthermore, it suggests that R20291 spores lost superdormancy but the mechanism involved remains to be determined. Changes in the surface hydrophobicity of C. difficile spores have been reported to be associated with the loss of the exosporium and an increase in their viability. In this study, the R20291 spore viability increase during room temperature storage was not associated with a change in surface hydrophobicity. Chapter 5 covers the determination and modeling of the thermal resistance of spores of the C. difficile strains M120 and DK1. They were treated at 70, 75, 80 and 85°C in PBS buffer and at 80°C in sterile ground beef. Linear 1.5 and 0.8 decimal reductions for strains M120 and DK1, respectively, were observed in PBS after 60 min at 70°C. At higher temperatures, non-linear inactivation reached 3.2 and 1.6 decimal reductions in 32 min at 75°C, and 3.1 and 2.9 decimal reductions in 24 min at 80°C, respectively. During come-up time to 85°C, a 1.1 decimal reduction was observed for M120 but none for DK1. Spores of M120 and DK1 strains in ground beef showed a 1.6 and 1.4 decimal ¬reductions, respectively, after 24 min at 80°C, i.e., a much lower value than in PBS. The modified Gompertz model for nonlinear microbial activation fitted the spore inactivation in PBS data better than the Weibull model yielding smaller maximum inactivation levels (A), faster maximum inactivation rates (μ[subscript max]), and shorter lag times (λ) for strain M120 than DK1. This study confirmed the high resistance of C. difficile spores suggesting the need to lower their presence in animal meat products. Chapter 6 focuses on the development of a model for the microbial inactivation achieved by a novel food processing technology, high pressure carbon dioxide (HPCD). The non-linear survival curves for the microbial inactivation by HPCD depend on the processing temperature and CO₂ pressure. In this study, the nonlinear inactivation of Escherichia coli CGMCC1.90 in apple juice by HPCD treatments was best described using a modified Gompertz primary model and the secondary models for its parameters b(T,P)=14.21+0.011P-0.67T+0.0085T² and c(T,P)= -0.10 +0.0023P+0.0037T (T and P in °C and MPa). Monte Carlo simulations were used to incorporate the variability and uncertainty of the parameter b and c estimates, which were then used to predict microbial inactivation values for a given time, temperature and CO₂ pressure combination and desired confidence boundary. The model predicts that HPCD processes can meet 5 decimal reduction at 95% confidence but at relative long apple juice processing times, i.e., 35-124 min treatments in the experimental temperature and pressure range of 32-42°C and 10-30 MPa, respectively. Risk assessments of food microbial safety have become a valuable tool to understand, analyze and control microbial risks. They address the pathogen source, load reduction by processing, and pathogen survival during storage and distribution in a quantitative manner. Chapter 7 describes a Monte Carlo based quantitative microbial risk assessment tool developed for the consumption of raw oysters potentially contaminated with the pathogen Vibrio vulnificus. It predicted that depuration at 15°C for 47 and 16 h would reduce the risk of oysters harvested during the warm (Jun-Aug) and transition seasons (Apr-May, Oct-Nov), respectively, to an acceptable level. Furthermore, the model predicted that the consumption of untreated raw oysters harvested during the cold season (Dec-Mar) can be considered an acceptable and very low risk. Moreover, the model can be adjusted by an individual processor to reflect the conditions at their specific location. This study demonstrated that Monte Carlo based models are an effective approach to use in quantitative risk management when considering the variability of multiple farm-to-table factors.
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1564. [Article] The optimal allocation of watershed conservation funding : a case study of the John Day River Basin, Oregon
This study determines the optimal allocation of watershed conservation funds in the John Day River Basin, Oregon. Fund managers can use a variety of targeting schemes to allocate their limited resources. ...Citation Citation
- Title:
- The optimal allocation of watershed conservation funding : a case study of the John Day River Basin, Oregon
- Author:
- Skelton, Katharine
This study determines the optimal allocation of watershed conservation funds in the John Day River Basin, Oregon. Fund managers can use a variety of targeting schemes to allocate their limited resources. Depending on which targeting criteria is used, they may or may not be achieving the maximum environmental benefits per dollar expended, a policy goal that is increasingly being adopted for conservation programs. Previous studies have provided the theory behind this optimal allocation of funds, but none, to the researcher's knowledge, have attempted a case study to illustrate the optimal allocation of funds as well as the misallocations that could result. Watershed conservation policies are very important, especially here in the Pacific Northwest where salmonid populations are endangered. As stream temperatures are lowered, salmonid recruitment increases. Improvements in riparian vegetation provide stream shade and bank stability. Shade decreases stream temperatures by preventing solar radiation from reaching the stream, while bank stability allows streams to become narrower and deeper, with more vegetative overhang. Narrower streams have less surface area to come in contact with solar radiation and vegetative overhang provides additional shade. A simultaneous equation system was used to estimate stream temperature and fish recruitment models for the thirteen streams studied, classified into three environmental attribute clusters. Fish recruitment models were developed for rainbow trout, Chinook salmon and speckled dace. Marginal values for rainbow trout and Chinook salmon from previous studies were used to calculate the total marginal benefits to society from increasing cold-water salmonid species. The analytical models were the basis for determining the optimal fund allocation, after considering the cumulative, indirect and correlated benefits derived from improving riparian vegetation conditions. Policy managers and previous studies have failed to consider these additional environmental benefits, particularly jointly produced benefits. Two scenarios were determined for the optimal fund allocation, based on the riparian conditions of the surveyed stream reaches. The riparian conditions are reported using a vegetative use index from one (the worst conditions) to four (the best conditions). Under the first scenario, which assumes a full range of riparian conditions, Granite Creek should receive funding priority with $51,756 in marginal social benefits received from improving the streamside vegetative use rating from one to four, for one mile of stream. Deerdorff Creek and Reynolds Creek would be the next two streams to receive funding, respectively, both for a vegetative use improvement from one to two. The second scenario assumes that only vegetative conditions in the surveyed segments exist in the stream. Under these circumstances, only six of the thirteen streams would even be considered for funding, with Granite Creek again receiving priority. Improving the vegetative use rating in Granite Creek from three to four, for one stream mile, will produce $9355 in marginal social benefits. Murderer's Creek and Camp Creek would be the next streams to receive funding for a vegetative use improvement from three to four and one to two, respectively. In addition to determining the optimal fund allocation, discussion is included about the policy implications that would result from ignoring the cumulative, indirect and correlated benefits. For the fund misallocation discussion Granite Creek was assumed to be the stream that should be given funding priority for an improvement from three to four only, with Murderer's Creek and Camp Creek receiving funds second and third, respectively. If an on-site, physical criterion is used as the targeting criteria, such as stream temperatures or the riparian vegetation conditions, then the cumulative benefits will be ignored. Two possible misallocations could result when the cumulative effects are ignored. First, streams with very high temperatures may receive funding, even if improvements in the vegetative use index will not lower temperatures enough so that salmonids can survive. Second, streams that have temperatures below the optimal range for salmonids, but have poor riparian vegetation may be funded. Improving streamside vegetation in those streams would be a misallocation of funds. Targeting based on the highest stream temperature criteria would only consider the direct benefits received from improving streamside vegetation. Under a temperature- based targeting criteria, Alder Creek would be the first stream funded with Mountain and Murderer's Creek following. If we assume only two streams could be funded, then there will be a loss of almost all marginal benefits per stream mile. If the change in the stream temperatures is used as the targeting criteria, and indirect benefits are ignored, then Camp Creek would receive funding priority, with Mountain Creek, Granite Creek and Murderer's Creek following. If it is again assumed that only two streams could be funded, this targeting scheme would result in an approximate loss to society of up to 87 percent in marginal benefits, per stream mile Additionally, all of the indirect benefits need to be taken into consideration in order to optimally allocate funds. If Chinook salmon are ignored, and rainbow trout are the only cold-water species taken into account, then society will forgo around 50 percent of marginal social benefits, per stream mile. This is if we assume two streams are funded, and the South Fork is the second stream to receive funds, rather than Murderer's Creek. Granite Creek would still receive funding priority. Finally, correlated benefits, or warm-water species, need to be considered. In this study ignoring the warm-water species would not effect fund allocation, as a marginal social value for speckled dace was not found. Even if we assume the speckled dace is a proxy for warm-water sport fish, such as bass, and the correlated benefits are taken into consideration, funding priority would still be given to Granite Creek. However, under the same assumptions, if the correlated benefits are ignored in Camp Creek, then society will misallocate funds and lose a small portion of marginal social benefits per stream mile. This study points towards small, high elevation streams being given funding priority. Granite Creek should be the first stream to receive funds in the John Day River basin, when funds are optimally allocated. However, if not all of the environmental benefits are taken into consideration, different streams may be targeted. When a temperature-based targeting scheme is used, Alder Creek would be given funding priority, even though no marginal social benefits would be derived. If the change in stream temperatures is used, Camp Creek will receive funds, with a large loss to society in marginal benefits. If not all of the indirect benefits are considered, the South Fork will be funded over Murderer's Creek, and only half of the possible marginal benefits will be received. Finally, when correlated benefits were ignored, the fund allocation in this study was not affected. However, fund managers still have to consider the tradeoffs involved between warm and cold-water adapted fish species. This is especially true if warm-water sport fish or endangered species are the jointly produced benefits. Failing to include all of the environmental benefits that are produced when conservation programs are initiated will lead policy managers to target the wrong streams or basins, and misallocate funds. In addition, using the wrong criteria to prioritize watersheds will also lead managers to misallocate funds. Funds should be allocated so that the total value of environmental benefits is maximized, and not the total amount of resources saved.
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Climate change and anthropogenic effects have vastly reduced Westslope Cutthroat Trout (Oncorhynchus clarki lewisi, WCT) habitat throughout their range, including the Colville National Forest in northeastern ...
Citation Citation
- Title:
- Understanding the Importance of Intermittently Fragmented Stream Habitat for Isolated Westslope Cutthroat Trout (<i>Oncorhynchus clarki lewisi</i>) in the Colville National Forest, Washington
- Author:
- Carpenter, Forrest Michael
- Year:
- 2016
Climate change and anthropogenic effects have vastly reduced Westslope Cutthroat Trout (Oncorhynchus clarki lewisi, WCT) habitat throughout their range, including the Colville National Forest in northeastern Washington where this study was conducted. Many native salmonid populations have declined in abundance since the early 1900s due to a variety of climate- and human-driven forces. Westslope Cutthroat Trout are especially sensitive to habitat loss or degradation and to climate change. Together, climate change, habitat degradation, and non-native salmonid invasions are contributing to increasingly fragmented WCT populations. Ongoing and predicted future warming trends are expected to further fragment these populations and isolate them in headwater stream reaches, with populations in the spatial margins of their distributions facing greater risk. Native salmonid populations are often separated or isolated by natural or artificial upstream migration barriers (i.e., waterfalls, culverts, etc.). Prior to continuing conservation and management actions targeting WCT, it is imperative to understand habitat requirements of this keystone species in fragmented areas. Field survey data were collected in the summer of 2015 on channel geomorphic characteristics and WCT presence/absence in 26 streams located in the Colville National Forest. A clear spatial separation was observed between Eastern Brook Trout (Salvenius fontinalis, EBT) and WCT above four culvert road crossings and the habitat in both of these areas was compared statistically to identify explicit differences. This dataset was also analyzed using logistic regression modeling to determine the best habitat predictors of the presence of isolated WCT populations existing upstream of these crossing. In general, stream habitat in the Middle and South Forks of Mill Creek had low large substrate, high fine sediments, and exhibited pool-riffle channel morphology. Pool habitat supporting isolated WCT was significantly smaller, in terms of volume and surface area, than pool habitat supporting sympatric populations of WCT and EBT, largely due to the headwater nature of channel units supporting isolated WCT populations. Additionally, due to the extreme drought conditions during 2015, stream flow was substantially diminished in the study area causing these reaches to be highly fragmented and largely disconnected from the rest of the stream channel. Fine sediments were generally higher in headwater reaches supporting isolated WCT, including in pools and riffles, which was unexpected, mainly because they exist above sediment delivery points in the longitudinal extent of the system. Logistic regression analysis indicated that the presence of isolated WCT populations was primarily positively associated with an increase in large wood and boulders, and negatively associated with increasing gravel, bedrock, habitat unit length, depth, and width (Significant x2, R2=0.174, misclassification rate = 14.9%, α=0.05). The final model correctly predicted 37.5% of isolated WCT presence observations and 96.5% of the WCT/EBT presence observations significantly better than by chance alone (k=0.81). This model, in fact, may be useful in identifying limited habitat due to the fragmented nature of the channel units supporting IWCT. Large wood and boulders were positively correlated to WCT presence, likely because both are important in the formation of pools and cascades. Channel unit length, width, depth, active channel width as well as gravel and bedrock substrates, were all negatively associated with WCT presence. This suggests that isolated WCT are primarily associated with small headwater cascades with complex shelter, which may provide greater thermal and predation refuge compared to shallow glide or large pool habitats. Future model analysis should include additional habitat variables such as water temperature, stream gradient, and species interactions to strengthen the prediction of Westslope Cutthroat Trout presence. Overall, I concluded that differences in stream habitat above and below blocking culverts are not driving Westslope Cutthroat Trout distributions in the study area due to confounding factors such as the presence of problematic barriers and small sample size. I also conclude that future conservation and management decisions specific to WCT should prioritize complex cascade habitat in headwater stream reaches because of the type and quantity of habitat they may provide, especially during severe drought or low flow conditions.
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1566. [Article] Nanoparticle-assisted diffusion brazing of metal microchannel arrays : nanoparticle synthesis, deposition, and characterization
Microchannel process technology (MPT) offers several advantages to the field of nanomanufacturing: 1) improved process control over very short time intervals owing to shorter diffusional distances; and ...Citation Citation
- Title:
- Nanoparticle-assisted diffusion brazing of metal microchannel arrays : nanoparticle synthesis, deposition, and characterization
- Author:
- Eluri, Ravindranadh T.
Microchannel process technology (MPT) offers several advantages to the field of nanomanufacturing: 1) improved process control over very short time intervals owing to shorter diffusional distances; and 2) reduced reactor size due to high surface area to volume ratios and enhanced heat and mass transfer. The objective of this thesis was to consider how nanomaterials, produced in part using MPT, could be used to solve problems associated with the fabrication of MPT devices. Specifically, many MPT devices are produced using transient liquid-phase brazing involving an electroplated interlayer consisting of a brazing alloy designed for melting temperature suppression. Unfortunately, these alloys can form brittle secondary phases which significantly reduce bond strength. In contrast, prior efforts have shown that it is possible to leverage the size-dependent properties of nanomaterials to suppress brazing temperatures. In this prior work, thin films of off-the-shelf elemental nanoparticles were used as interlayers yielding joints with improved mechanical properties. In the present investigation, efforts have been made to characterize the synthesis and deposition of various elemental nanoparticle suspensions for use in the transient liquid-phase brazing of aluminum and stainless steel. Advances were used to demonstrate the nanoparticle-assisted diffusion brazing of a microchannel array. In the first section, a silver nanoparticle (AgNP) interlayer was produced for the diffusion brazing of heat exchanger aluminum. Efforts are made to examine the effect of braze filler particle size (~5 nm and ~50 nm) and processing parameters (heating rate: 5ºC/min and 25ºC/min; brazing temperature: 550ºC and 570ºC) on thin coupons of diffusion-brazed 3003 Al. A tensile strength of 69.7 MPa was achieved for a sample brazed at 570°C for 30 min under 1 MPa with an interlayer thickness of approximately 7 μm. Further suppression of the brazing temperature to 500ºC was achieved by sputtering a 1 µm thick layer of Cu before depositing a 5 nm thick film of AgNPs resulting in a lap shear strength of 45.3±0.2 MPa. In the middle section of this thesis, several techniques are investigated for the synthesis of sub 10 nm diameter nickel nanoparticles (NiNPs) to be used in the diffusion brazing of 316L stainless steel. The average NiNP size was varied from 9.2 nm to 3.9 nm based on the synthesis technique, solvent and reducing agent used. Conventional wet-chemical synthesis using NiCl₂.6H₂O in ethylene glycol (solvent) and N₂H₄.H₂O (reducing agent) resulted in the formation of 5.4 ± 0.9 nm NiNPs. Continuous flow synthesis using a microchannel T-mixer (barrel diameter of 521µm) and a 10 second residence time of reactants in a bath temperature of 130ºC resulted in a particle size of with 5.3 ± 1 nm. To make the synthesis safer and less energy intense, microwave heating was used along with less toxic Ni(CH₃CO₂)₂·4H₂O (nickel salt), propylene glycol (solvent) and NaPH₂O₂ (reducing agent) yielding 3.9 ± 0.8 nm diameter NiNPs. For the final section, nickel nanoparticles were synthesized using NiCl₂.6H₂O (nickel salt), de-ionized water (solvent), NaBH₄ (co-reducing agent), N₂H₄.H₂O (reducing agent) and polyvinylpyrolidone (capping agent) yielding 4.2 ± 0.6 nm NiNP. Several deposition techniques were investigated for controlling film thickness and uniformity in the diffusion brazing of 316L stainless steel (SS). Using in-house prepared NiNP and automated dispensing, a hermetic joint up to 70 psi (tested pressure) was obtained in 316L SS substrates under brazing conditions of 800ºC, 2 MPa and 30 min. Throughout the course of this thesis, techniques used for characterizing nanoparticles, films and joints included FT-IR, XRD, SEM, TEM, HRTEM, EDS, EPMA, DSC, mass spectrometry, and lap-shear testing.
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1567. [Article] The influence of prescribed fire on the rare endemic plant Delphinium pavonaceum (Peacock larkspur)
In the wetland prairie of William L. Finley National Wildlife Refuge (FNWR) in western Oregon, we investigated the response of Delphinium pavonaceum Ewan (peacock larkspur, Ranunculaceae), an endangered ...Citation Citation
- Title:
- The influence of prescribed fire on the rare endemic plant Delphinium pavonaceum (Peacock larkspur)
- Author:
- McKernan, Brie-Anne
In the wetland prairie of William L. Finley National Wildlife Refuge (FNWR) in western Oregon, we investigated the response of Delphinium pavonaceum Ewan (peacock larkspur, Ranunculaceae), an endangered perennial forb, to four unreplicated dormant season fire regimes of 0, 2, 4, or 10 fires that were applied over a 12-year period. Additionally, an unexpected removal of woody plants by refuge staff within some portions of our control area offered an unplanned opportunity for study. In 2002 we measured the density and vigor of reproductive plants, and performed seed germination trials. In 2003 we repeated previous field measurements, sampled immature plant density, and recorded observations of the insects visiting D. pavonaceum in burned and unburned habitats. We hypothesized that this rare endemic species and its insect visitors would respond positively to prescribed burning or the removal of woody species. Low seedling density was found in the unburned and hand-removal areas, likely due to interference from litter and/or taller, shading plants. We also found low seedling density in sites burned the previous year, implying that fire consumes or damages unprotected seeds in the litter layer or exposed on the soil surface. Seedling density was greater in a site burned three seasons previously, suggesting that fire ultimately leads to the enhancement of seedling density following the replenishment of the seed bank. The largest density of recruits was detected in a subunit recently returned to fire management in 1999, and also burned in 2002 following our first field season. However, the other, more-frequently burned sites did not exhibit an increased density of recruits, possibly due to a reduction of the seed bank following repeated bums, and increased intraspecific competition with mature plants. The elevated density of seedlings and recruits we observed in some burned areas may lead to population growth, as we observed a greater density of reproductive plants in the two most-frequently burned subunits during both years of study. Our results also suggest that fewer plants enter summer dormancy in burned areas, and that increases in flowering plant density may decline after 3 years. Plants in the burned and hand-removal sites were shorter, likely resulting from water stress following the removal of shading plants and litter. Additionally, plants in unburned areas might have experienced greater stem elongation due to competition with tall and dense vegetation. Plants in the burned and hand-removal areas were generally similar to the unburned control site for flower and fruit production, fruit set, seed production and seed mass. However, plants in the burned and hand-removal areas produced more flowers per centimeter of height, indicating that they allocated more energy to reproduction than plants in the unburned area. We suggest that the decreased productivity we observed in some vigor traits is not problematic to D. pavonaceum conservation goals and may be ameliorated after 3 years. Bombus ca1ifornicus, B. appositus, and several large moths were the only insects we observed visiting D. pavonaceum during the two years of this study. We did not detect a difference in bumblebee abundance between a frequently burned and unburned study plot during the peak flowering time of D. pavonaceum. However, our small sample size requires that this result be cautiously interpreted and further studied, as it is possible that our visitation data would change appreciably with a broader range of observations. Our results indicate that the current FNWR fire management plan is not in conflict with D. pavonaceum conservation. The choice of fire-return interval seems to influence D. pavonaceum populations and plant vigor, but because the fire-schedule at FNWR was altered in 1997, our ability to recommend an appropriate fire-regime for this species is limited. Although not directly investigated, we suggest that annual fires, when applied for more than five consecutive years, might lead to population declines for this species because fire appears to consume the seed bank and reduce seedling density. If annual fires are returned to FNWR, the potential for this undesirable result should be investigated for at least 10 years by population monitoring.
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It is uncertain how predicted changes in climate will impact vegetation responses and plant species’ distributions because the physiological mechanisms underlying thresholds for damage are not well understood, ...
Citation Citation
- Title:
- Approaches for Characterizing Plant Physiological Responses to Environmental Stress
- Author:
- Marias, Danielle E.
It is uncertain how predicted changes in climate will impact vegetation responses and plant species’ distributions because the physiological mechanisms underlying thresholds for damage are not well understood, and responses to stress vary by functional type and developmental stage. Thus, it is crucial to investigate physiological responses to heat and drought stress on multiple species, populations, and growth stages with diverse approaches. In this dissertation, I employ a suite of physiological and modeling methods to inform our knowledge of plant physiological responses to environmental stress in Coffea arabica saplings, Pseudotsuga mensizeii (PSME) and Pinus ponderosa (PIPO) seedlings, and old-growth PIPO. In Chapter 2, I evaluate the effect of leaf age and methodology on the thermotolerance or heat tolerance of C. arabica leaf discs using chlorophyll fluorescence and electrolyte leakage methods. I found that mature leaves were more heat tolerant than expanding leaves, longer time between temperature exposure and measurement yielded more accurate thermotolerance assessments, and photochemistry was more heat-sensitive than cell membranes. To complement the second chapter investigating heat stress responses on detached leaf discs, Chapter 3 examines the effect of leaf age and heat stress duration (45 min or 90 min) on whole-plant physiological responses and capacity to recover in C. arabica by monitoring chlorophyll fluorescence (F[subscript V]/F[subscript M]), gas exchange, and foliar non-structural carbohydrate (NSC) dynamics in situ in response to a simulated heat wave (49°C) in a growth chamber. I found that the 90 min treatment resulted in greater photosynthetic damage and slower recovery than the 45 min treatment, expanding leaves recovered more slowly than in mature leaves, and both heat treatments inhibited flowering. A leaf energy balance model demonstrated that heat stress would be exacerbated by drought-induced stomatal closure. Heat treatment duration significantly impacted NSC dynamics that were closely related to reproduction and repair. Because seedling establishment governs species’ distributions, and because seedlings are particularly threatened by high temperatures at the soil surface, in Chapter 4 I examined the thermotolerance and heat stress responses of PIPO and PSME seedling populations from contrasting climates. Unexpectedly, I found that PSME was more heat tolerant the PIPO. I also monitored physiological recovery after exposure to a simulated heat wave (45°C) by measuring photosynthesis, F[subscript V]/F[subscript M], foliar NSC, and carbon stable isotope ratios (proxy for intrinsic water use efficiency, iWUE). Heat stress responses were consistent with phenotypic plasticity and reflected the conditions under which the plants were grown, while iWUE, a measure of potential drought resistance, was consistent with ecotypic differentiation and the climates from which the seedlings originated. To investigate responses to environmental stress on larger temporal and spatial scales without the challenges of making repeated physiological measurements on old-growth trees, in Chapter 5 I used long-term trajectories of tree-ring growth and carbon and oxygen isotopes of tree-ring cellulose (δ¹³Ccell, and δ¹⁸Ocell) to successfully predict the stand characteristics of two sets (upland, riparian) of old-growth PIPO using the Physiological Principles in Predicting Growth (3-PG) model, the δ¹³Ccell submodel, and a δ¹⁸Ocell submodel added by me. The expanded model helped to explain physiological drivers underlying the different tree-ring growth, δ¹³Ccell, and δ¹⁸Ocell trajectories measured at the upland and riparian sites. The combination of both δ¹⁸O and δ¹³Ccell submodels provided a useful and novel way to constrain 3-PG. This dissertation demonstrates an innovative strategy of applying diverse approaches to understand the physiological mechanisms behind vegetation responses to environmental stress.
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1569. [Article] A 37,000-year record of paleomagnetic and environmental magnetic variability from Burial Lake, Arctic Alaska
Burial Lake sediments from the Noatak Basin in the northwest Brooks Range of Arctic Alaska (68.43°N, 159.17°W, 21.5 m water depth) provide the oldest continuous lacustrine record of paleo-environmental ...Citation Citation
- Title:
- A 37,000-year record of paleomagnetic and environmental magnetic variability from Burial Lake, Arctic Alaska
- Author:
- Dorfman, Jason Michael
Burial Lake sediments from the Noatak Basin in the northwest Brooks Range of Arctic Alaska (68.43°N, 159.17°W, 21.5 m water depth) provide the oldest continuous lacustrine record of paleo-environmental change and paleomagnetic secular variation (PSV) in eastern Beringia. A precise radiocarbon chronology, determined through accelerator mass spectrometry (AMS) allows us to independently constrain the region's climatic and geomagnetic evolution over the last ~37,000 years. Progressive alternating field (AF) demagnetization of u-channel samples and additionally acquired physical, geochemical, and rock-magnetic datasets, reveal three distinct lithologic subunits associated with the last glacial period (37.2 - 19.4 ka), the deglacial transition (19.4 - 9.8 ka), and the Holocene (9.8 ka - present). Rock magnetic variability suggests changes in sediment provenance associated with the transition from glacial to interglacial conditions. This is interpreted to result from a variable flux of aeolian derived sediment, and is supported by complimentary internal proxy data from Burial Lake. Other regional paleoclimate data, various glacial chronologies for the Brooks Range, and a relative sea level reconstruction facilitate a discussion of possible local, widespread, and far-field sources of dust, and the time-dependency of potential forcing mechanisms governing its production, availability, transport, and deposition. Results indicate an overall reduction in dust input from the glacial period to the Holocene that is largely attributed to increases in terrestrial and aquatic productivity, warming, and moisture availability, which limited widespread landscape deflation and production of dust. Subaerial continental shelves may have provided significant far-field sources of dust to interior Alaska during the glacial period, that were shut off by sea level inundation following the Last Glacial Maximum (LGM; 19 - 26.5 ka), further contributing to diminishing dust emissions. While glacial activity in the Brooks Range may provide local revenue of dust, activation of those deposits and timing of deposition in Burial Lake often appears to be more directly linked with general aridity, lack of vegetative cover, and increased windiness, rather than glacial advances or retreats. Despite this lithologic complexity, we isolate a stable, single-component characteristic remanent magnetization, carried predominately by low-coercivity (titano)magnetite in the pseudo single-domain (PSD) to multi-domain (MD) magnetic grain size range. We reconstruct directional paleomagnetic secular variation (PSV) over the full length of the record, and relative paleointensity (RPI) for the last ~14,700 years, which are consistent with available regional PSV records and continuous spherical harmonic model outputs. We observe only small deviations from geocentric axial dipole (GAD) predictions during the Holocene, while larger amplitude directional features are prevalent before 10 ka, and inclinations lay significantly shallower than GAD. While this may be related to lithology and the sediment magnetic acquisition process, regional records (including those derived from lava flows) indicate similar Holocene-Pleistocene discrepancies. Following on the "eccentric dipole" hypothesis, subdued secular variation and GAD-like behavior in the Pacific appears confined to the Holocene high-intensity state, showing greater variability as Pleistocene field strength diminishes, and/or the dipole axis is shifted away from the Pacific hemisphere. Long period trends in PSV from in the Alaskan Arctic are also similar in character to far-field sites (e.g., Hawaii and Siberia), suggesting large-scale coherent core-fluid flow regimes, expressed over surface geographical extents >5,000 km, and spanning Holocene-Pleistocene time intervals. The well-dated Burial Lake record fills a significant data gap in the growing Holocene paleomagnetic database, while allowing us to extend our understanding of PSV beyond the Holocene and into the Pleistocene, and continue the development of regional stratigraphic dating curves.
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1570. [Article] Sedimentation, economic enrichment and evaluation of heavy mineral concentrations on the southern Oregon continental margin
Heavy minerals can contain potentially economic amounts of metals as both matrix and trace constituents. Such minerals appear as unconsolidated black sands on the continental shelf off southwest Oregon ...Citation Citation
- Title:
- Sedimentation, economic enrichment and evaluation of heavy mineral concentrations on the southern Oregon continental margin
- Author:
- Bowman, Kenneth Charles Jr
Heavy minerals can contain potentially economic amounts of metals as both matrix and trace constituents. Such minerals appear as unconsolidated black sands on the continental shelf off southwest Oregon and along the Oregon coast. Two diverse energies are considered in this investigation. Environmental energy of the depositional regimen, Part I; energy involved in crystallization of transition metals from a magma, Part III. In Part II, an analytical scheme for the evaluation of opaque oxides is proposed, and an examination of the results as applied to two samples is presented. Part I The unconsolidated black sands on the Oregon continental margin have been profoundly affected by tectonic uplift aid by cyclic erosive transgression and regression. Progressive enrichment in heavy minerals from the Klamath Mountains has apparently occurred during each glacio-eustatic regression of the Pleistocene seas, each regression a period of intensified erosion and sediment transport. Subsequent erosive transgressions selectively sort and redistribute these heavy minerals into paralic beach and nearshore deposits. Uplift of the coast and shelf implies that the heavy minerals were reworked during the Holocene transgression into concentrations of greater extent and higher ore tenor than relict deposits of earlier transgressions in upraised Pleistocene terraces. Extrapolation of ore reserve values from the terraces by "Mirror Image" concepts might seriously underestimate the potential of offshore deposits. Offshore heavy mineral concentrations should be coincident with observed submarine terraces. Part II An analytic scheme was developed to investigate opaque oxides in two samples; one from the Pleistocene terraces; the other from near the present shelf edge. Analyses involving X-ray diffraction techniques, atomic absorption and neutron activation established the mineralogy and elemental distribution in magnetically separated diagnostic splits. Chrome spinel, ilmenite and magnetite comprise the opaque oxide fraction in both samples. Correlation studies of these analyses suggest: (1) Chromium is a matrix metal of chrome spinel and is diadochic into magnetite. (2) Iron appears in all opaque oxides and in increasing amounts with increasing magnetic susceptibility. (3) Titanium is a matrix metal in ilmenite, and diadochic into chrome spinel and magnetite. (4) Nickel and ruthenium are diadochic into and correlated to the spinel structure; i.e. to chrome spinel and magnetite. (5) Osmium appears to be correlated to chromium. (6) Zinc is limited to spinel in these samples. Part III Goldschmidt's and Ringwood's criteria for diadochy often fail to explain the distribution of the transition metals because crystal field effects are not considered. Favored d[superscript n] configurations, e.g. octahedrally coordinated, low spin d⁶ cations in the spinel minerals, result in shortened interatomic distance and significantly strengthened cation-ligand bonds, possibly affecting the distribution of such metal cations. The octahedral site preference energy parameter (OSPE) has been used to explain distributional behavior of the first (3d) transition series metals. OSPE calculations for four low spin d⁶ cations - Co(III), Ru(II), Rh(III), and Pt(IV) - give significantly high values for this parameter. High OSPE valued transition metal cations possibly form stable proto-mineral oxide complexes in the magma which persist through crystallization. These associations predetermine the enrichment of transition metals in oxide minerals and act as nuclei during cooling and solidification. Subduction of oxidized and hydrolyzed near-surface rocks down a Benioff zone provides progressively higher Eh in the magma, a variety of cation oxidation states, and water for sepentinization of ultramafic rocks. The distribution of the platinum metals in a strongly reducing magma environment should be different than in the oxidizing magma proposed for the Klamath ultramafics. The OSPE parameter offers an explanation for the observed distribution of platinum group metals in spinel minerals from this investigation, in chromites from Uralian dunitic massifs and the Stillwater complex; and of iridium from the Great Lake Doleritic Sheet, Tasmania. Chrome spinel from Oregon had twice the concentration of ruthenium, and one-third the amount of osmium as similar Uralian chromite deposits. The first significant concentration of ruthenium in magnetite is herein reported recommending continued research into the platinum metal distribution in southwest Oregon.