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2281. [Article] A cooperative effort to track Humboldt squid invasions in Oregon
Interannual variability of Humboldt squid (Dosidicus gigas) occurrence in the northern California Current System is largely unknown. In Oregon, the distribution of this versatile predator and what is influencing ...Citation Citation
- Title:
- A cooperative effort to track Humboldt squid invasions in Oregon
- Author:
- Chesney, Tanya A.
Interannual variability of Humboldt squid (Dosidicus gigas) occurrence in the northern California Current System is largely unknown. In Oregon, the distribution of this versatile predator and what is influencing their range expansion from Mexico is poorly understood due to the recent nature of their "invasion" and a lack of monitoring. Humboldt squid are large predators that have the potential to affect ecosystem structure and fisheries because of their high-energy demands and ability to exploit a variety of oceanographic conditions and prey sources. Developing baseline distribution information is a critical first step to assess their potential ecological, social, and economic impacts, and to develop models to predict future range expansion. This study has two main objectives: (1) to document where and when Humboldt squid have been present in Oregon through cooperative fisheries research, and (2) to correlate the sightings with oceanographic conditions using a geographic information system (GIS) and species distribution modeling (SDM). I conducted 54 interviews with local fishermen and aggregated their squid sightings with available fishery-independent survey and fishery-dependent observer data from the National Marine Fisheries Service. I compiled a total of 339 Humboldt squid sightings, reported for the years 2002-2011 from the Oregon coast to 131° west longitude. Correlation analyses were performed for Humboldt squid sightings and sea surface temperature (SST), chlorophyll a content (chla), sea surface height anomalies (SSH), dissolved oxygen at 30 m depth (30 m DO), and sea surface salinity (SSS) using a GIS, nonparametric multiplicative regression (NPMR) habitat modeling, and maximum entropy modeling (Maxent). Results indicate that oceanographic conditions have the potential to influence Humboldt squid occurrence, and in Oregon, sightings vary temporally and spatially. Combining the sightings from fishermen and scientific surveys greatly enhanced the spatial extent of the data. Humboldt squid were most frequently observed between 124.4°W and 125°W in proximity to the shelf-break at the 200 m isobath, with peak sightings (116) recorded in 2009 and the fewest (6) reported in 2003 and 2011. The highest occurrence of Humboldt squid were observed at a SST of 10.5-13.0°C, 0.26-3.0 mg m⁻³ chla content, -4.0-1.0 m SSH anomalies, 32.2-32.8 psu SSS, and at 3-4.5 ml L⁻¹ and 6-7 ml L⁻¹ 30 m depth DO. Maps of estimated likelihood of occurrence generated by NPMR were consistent with overlayed observations from fishermen, which were not used in the model because they were limited to presence-only information. An interdisciplinary approach that incorporates cooperative fisheries research and ecosystem-based management is necessary for monitoring Humboldt squid in Oregon. Traditional methods are insufficient because Humboldt squid are data-poor, highly migratory, and are main predators of many commercially important fisheries in Oregon. Based on my findings, sightings recorded by fishermen covered a much larger area over a longer time frame than the scientific survey and observer data, and excluding their knowledge would have led to a different interpretation of Humboldt squid distribution and environmental tolerances. Although there is uncertainty in the data from potential map bias or misidentification of smaller Humboldt squid, incorporating sightings from fishermen with traditional fisheries research increases the quantity and quality of information. Cooperative monitoring for Humboldt squid could include training in species identification and sea condition reporting in logbooks. Future "invasions" are likely, and more eyes on the water will improve our understanding of the behavior and impacts of Humboldt squid on coastal resources.
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This study delineates and characterizes the distribution of montane meadows in the Willamette National Forest, identifies encroachment patterns in relation to topographic features and proximity to trees ...
Citation Citation
- Title:
- Meadow classification in the Willamette National Forest and conifer encroachment patterns in the Chucksney-Grasshopper meadow complex, Western Cascade Range, Oregon
- Author:
- Dailey, Michele Meadows
This study delineates and characterizes the distribution of montane meadows in the Willamette National Forest, identifies encroachment patterns in relation to topographic features and proximity to trees in the Chucksney-Grasshopper meadow complex, and examines tree species and age distributions in relation to distance from forest edges or isolated tree clusters in the West Middle Prairie meadow. The Willamette National Forest covers approximately 6780 km² and intersects two main physiographic provinces comprised of the Cascade Crest Montane Forests and Subalpine/Alpine regions to the east, and the Western Cascades Montane, Lowland, and Valley regions to the west. Tree species commonly found in the study area include firs, cedar, pine, larch, spruce, and hemlock. Non-forested openings, including meadows, are distributed throughout the study area. Matched Filtering analysis was applied to Landsat ETM+ imagery acquired in September 2002 and combined with ancillary data that delineates stand replacing fire and harvest disturbances that occurred between 1972 and 2004 to create a vegetation classification of the Willamette National Forest that identifies meadows. The meadow classification was then combined with data depicting topographic position, slope, aspect, and elevation. Chi-squared statistics were applied to determine if meadows were significantly concentrated in areas characterized by these physical factors. In the western extent of the Willamette National Forest, meadows are concentrated on steep, south and east facing ridges between 1000 and 2000m in elevation. In the eastern extent of the Willamette National Forest, meadows are concentrated in valleys between 500 and 1000 meters in elevation and occur on both gentle and steep, east and south facing slopes. The vegetation classification provides a consistent and comprehensive dataset of meadow distribution in the Willamette National Forest. The Chucksney-Grasshopper meadow complex is contained by the Chucksney Mountain roadless area and comprised of approximately 8 distinct meadows located 27 kilometers northeast of Oakridge in the Willamette National Forest. The meadows occur on mostly south and east facing steep slopes near the ridgeline, and host varied dry and mesic plant communities. Herbaceous cover for three snapshots in time was classified using aerial photographs taken in 1947, 1972, and 2005 to determine conifer encroachment into the meadows. Chi-squared statistics were applied to determine if encroachment patterns were associated with slope, aspect, or proximity to tree cover. Encroachment occurred significantly closer to existing trees in all meadows suggesting the ameliorating effects of forest create conditions favorable for seedling establishment. Encroachment was also significant on steep, south and east facing slopes in some meadows, but also on gentle, west facing slopes in other meadows indicating a complex interaction of land use history, physical, and biological factors. The encroachment history analysis provides the preliminary framework for a model that can be used to identify meadows at risk for invasion. The West Middle Prairie of the Chucksney-Grasshopper complex, also known as Meadow 4, is a 21 hectare meadow characterized by a dry meadow community at the northern boundary, a mesic forest-meadow mosaic towards the southern boundary, and a rock garden at the western boundary. This meadow underwent mechanical tree removal in 1964 and a prescribed burn in 1996 to thwart conifer invasion. Four transects intersecting burned and unburned areas at the forest edge and through isolated tree clusters were sampled to determine the distribution of tree species and ages relative to their position in the transect. Data imply Pinus contorta invasion was promoted by the 1996 burns and that seedling establishment has occurred progressively from forest edges as well as simultaneously in a band along the forest edge. These findings suggest the prescribed burn was not adequate to control invasion and such management methods should be reviewed in the context of on-going research into alternate eradication measures. This research also supports other work that suggests initial seedling establishment accelerates subsequent seedling establishment and that eradication of early invaders is important for efficient management. This study can inform meadow habitat maintenance and restoration in three ways: it provides and inventory of meadows in the Willamette National Forest, a framework for a tool to predict which meadows are at risk for invasion and therefore are potential targets for action, and finally a report on past maintenance efforts and observation of invasion patterns at a fine scale.
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2283. [Article] Forest-meadow dynamics in the central western Oregon Cascades : topographic, biotic, and environmental change effects
Montane meadows comprise a small area of the predominantly forested landscape of the Oregon Cascade Range. Tree encroachment in the last century in these areas has threatened a loss of biodiversity and ...Citation Citation
- Title:
- Forest-meadow dynamics in the central western Oregon Cascades : topographic, biotic, and environmental change effects
- Author:
- Rice, Janine, M.
Montane meadows comprise a small area of the predominantly forested landscape of the Oregon Cascade Range. Tree encroachment in the last century in these areas has threatened a loss of biodiversity and habitat. Climate change in the coming century may accelerate tree encroachment into meadows, and exacerbate biodiversity loss. Multiple environmental factors of topography, biotic interactions, climate, and disturbance, whose interactions and impacts are unclear, influence forest encroachment into meadows. This dissertation examines these complex interactions and factors in two montane meadow ecosystems at Lookout (44º 22′N, 122º 13′W) of the Western Cascade Range and Bunchgrass (44º 17′N, 121º 57′W) of the High Cascade Range of Oregon. A change detection analysis quantifies how topographic factors and proximity to edge were related to tree encroachment into the two montane meadows of the Cascade Range of Oregon. Areas that have experienced tree encroachment were identified and partitioned by distance to forest edge, aspect, and slope class using historical air photo interpretation over 54 years from 1946, 1967, and 2000 at Lookout and Bunchgrass meadows in the western Cascades of Oregon. Meadow area decreased by more than 1% per year, with a net decrease of 60%, and a net loss of 22 ha at Lookout Meadow and 28 ha at Bunchgrass Meadow from 1946 to 2000. From 72% (Lookout) to 77% (Bunchgrass) of meadow area within 5 m of a forest edge became forest by 2000. Twothirds to three-quarters of meadow area on south and west aspects at both sites converted to forest from 1946 to 2000. Two-thirds of meadow conversion to forest from 1946 to 2000 occurred on slopes <6° at Bunchgrass Meadow, but meadow conversion to forest was more evenly distributed among slope classes at Lookout Meadow. Restoration efforts may need to focus on westerly or southerly aspects in areas < 5 m from the forest edge. The effects of biotic interactions and climate on the spatial patterns of two species (Lodgepole pine and Grand fir) were tested at Bunchgrass Meadow, a 37-ha meadow complex in the High Cascades of Oregon. A spatial analysis was used to quantify spatial patterns of more than 900 saplings and trees of these two species that had established since 1916 in a 0.21 ha early tree succession area. The light- and heat-tolerant species, Lodgepole pine, tended to establish initially and at relatively longer distances from other trees; Lodgepole seedlings avoided establishment within 2 m of >35-yr-old Grand fir. In contrast, the shade-tolerant species, Grand fir, tended to establish subsequently at relatively short distances to other trees, and was closely associated with older trees of both species. Lodgepole pine establishment was associated with warm, dry late summers, while Grand fir establishment was associated with wet springs and cool summers. Tree encroachment was regulated by both climate variability and biotic interactions responding to species’ environmental tolerances. Environmental tolerances influenced the rate of tree species establishment in the meadow, but biotic interactions were more important than exogenous factors, such as climate, in controlling the spatial patterns of encroachment dynamics. The relative contributions of climate change, atmospheric CO2 concentrations, and fire regimes, and their interacting effects on past and future non-forested areas were investigated with a modeling experiment. A generalized ecosystem model, LPJ-GUESS, was used to disentangle the impacts of environmental drivers (increased temperature, increased atmospheric CO2 concentrations, and changing fire frequency) on primary production, biomass, and extent of meadow (non-forest area) at a site representing montane meadow and forests of the western Cascades of Oregon. Model projections based on a moderately high future-warming scenario (4 °C increase from 2000 to 2100) indicated that fire disturbance played the largest role in reducing projected forest area and expanding non-forested areas, while fire suppression had the largest opposite effect. Increased temperature altered species composition to higher temperature-tolerant tree species, but it did not have a significant effect on the projected extent of forest or nonforest areas. Increased atmospheric CO2 concentration increased forest biomass, but it did not significantly change the projected extent of non-forest area. Projected changes in the extent of forest and non-forest areas lagged behind the potential impacts of environmental changes on primary production and biomass. The net effects of potential future environmental factors point to a continued expansion of forests and reduction of non-forested areas if fire suppression is maintained. The use of fire or tree removal may continue to be required to preserve these unique and vital meadow ecosystems of the Oregon Cascades.
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2284. [Article] An ecological study of Diatomovora amoena, an interstitial acoel flatworm, in an estuarine mudflat on the central coast of Oregon
The distribution and abundance of the interstitial acoel turbellarian, Diatomovora amoena Kozloff, 1965 was studied in an estuarine intertidal sand flat in Yaquina Bay, Oregon, from May 1970 through May ...Citation Citation
- Title:
- An ecological study of Diatomovora amoena, an interstitial acoel flatworm, in an estuarine mudflat on the central coast of Oregon
- Author:
- Thum, Alan Bradley
The distribution and abundance of the interstitial acoel turbellarian, Diatomovora amoena Kozloff, 1965 was studied in an estuarine intertidal sand flat in Yaquina Bay, Oregon, from May 1970 through May 1971. Monthly measurements of biological (organics, sulfides, chlorophyll, and carotenoids), pore water (salinity, pH,oxygen, and temperature), and sediment (fine sediment percentage, grain size, sorting, skewness, and kurtosis) factors were made along a transect at four intertidal stations with elevations of -2.0, 0.0, 1. 6, and 3.0 feet, stratified by selection from a curve for tidal exposure, and at two depths (0, 0 cm to 0. 5 cm and 0. 5 cm to 1. 0 cm) of the sediment. Estuarine factors that were monitored continuously included temperature, salinity, tide elevation, and insolation. The interrelationships among these environmental parameters, their roles in the interstitial sediment system, and the hydrology of the groundwater in the beach, were investigated in order to characterize the interstitial environment of the sand flat and to determine the environmental factors limiting the distribution and abundance of D. amoena. Seasonality was indicated in most of the factors measured. The sediment system was strongly reducing during summer and fall as organic production increased. Particle size analyses showed that transport and deposition of fine sediments contributed to the development of reducing conditions. The properties of the interstitial environment of D. amoena were found to be controlled by the level of groundwater, rate of percolation, and degree of mixing within the beach. Density of D. amoena was highest during the fall and early winter, and lowest throughout the winter. Summer production of plant material in the lower intertidal lead to reducing conditions at the sediment surface. Reduction in animal density at the lower two stations was attributed to these reducing conditions, and to the rafting of animals away from the intertidal with the algal mat. Decrease in animal density in the upper two stations was attributed to lethal low temperatures and salinities that occurred during heavy precipitation in the winter and coincided with low tidal exposure. Exclusion of animals from depths greater than 0. 5 cm in the sediment was attributed to lethal levels of sulfide. Tolerance of D. amoena to temperature, salinity, and sulfide was determined experimentally. The 25 combinations of temperature and salinity, and the 12 combinations of temperature and sulfide that were employed were selected on the basis of actual levels measured in the study area. The temperature and salinity survival results were fitted to a response surface which was used to evaluate these factors in limiting animal distribution. Survival of acoels was independent of temperature up to 6 hours of exposure, and strongly temperature-dependent after 24 hours of exposure. Initial mortality was attributed to osmotic stress. Upon exposure to sulfide at 50 μgm S/ml, these animals did not survive beyond 6 hours, demonstrating that sulfide in high concentrations is toxic to D. amoena. At lower concentrations of sulfide (10 μgm S/ml), the acoels were able to live for over 20 hours. Lowering the temperature at both concentrations helped to prolong the lives of the animals. Levels of sulfide similar to those used in the experiment Levels of sulfide similar to those used in the experiment (10 μgm S/0.5 cm³ = 50 μgm S/ml.) were found at the sediment surface in the lower two stations during September, at which time animal density was found to be decreasing. At the upper two stations in September, where the level of sulfide was 3 μgm S/0.5 cm³, the acoel population was found to be increasing, thus bearing out the assumption that population density is, indeed, affected by sulfide. The nature of the interstitial sediment system as a habitat for meiofaunal organisms was explored and the role of the groundwater hydrology, as a buffer against seasonal variation in the estuary, in maintaining this system was examined. A portion of the littoral shore considered in this investigation was conceptualized as a factor model, the principal parts of which were selected for study. The seasonal cycles of the major input factors were found to be relatively stable from year to year, while the timing of these cycles varied. The numerous positive and negative correlations that were found within and between the biological, pore water, and sediment groups of factors indicated the multiplicity of direct and indirect interactions and supported the contention that the tidal flat is a complex interrelated system. Change in one or more of the major factors, such as precipitation, river runoff, sedimentation, or tidal prism, can be expected to have diverse effects on the littoral sediment environment.
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2285. [Article] Variation in the timing of coho salmon (Oncorhynchus kisutch) migration and spawning relative to river discharge and temperature
Coho salmon (Oncorhynchus kisutch) migration and spawning are unique components of the salmon life cycle because they require synchrony of behavior with other individuals as well as with acceptable fluvial ...Citation Citation
- Title:
- Variation in the timing of coho salmon (Oncorhynchus kisutch) migration and spawning relative to river discharge and temperature
- Author:
- LovellFord, Rachel
Coho salmon (Oncorhynchus kisutch) migration and spawning are unique components of the salmon life cycle because they require synchrony of behavior with other individuals as well as with acceptable fluvial conditions. As with other organisms that exhibit group mating behavior, it is likely that environmental cues trigger coho salmon movement to spawning grounds. These cues may also provide usable habitat for migration and spawning. River discharge, temperature, and length of day have long been assumed to be the environmental cues which trigger migration and spawning of coho salmon as coho return within the same season each year to spawn. Hatchery studies have also shown that the timing of reproductive behavior is heritable. If this heritability is determined by the fluvial conditions of the spawning grounds, then a predictable relationship should exist between reproductive behavior and the hydrologic and thermal regimes. Surprisingly, no defensible correlations between discharge thresholds and spawning or migrating activity have been identified for naturally reproducing coho salmon. Thermal, velocity, and depth limitations have been identified for coho salmon, but these values have not been examined in combination or within the context of a hydrologic and thermal regime. This study compares interannual patterns in the timing of coho mid-river migration in the North Umqua (180 km up river from the estuary) and the initiation of spawn timing in the Smith River basins (Oregon) with river discharge and water temperature data to ascertain whether these behaviors are driven by fluvial conditions. Additionally, we used this data to identify the window over which most migration and spawning takes place in our test systems. On the North Umpqua, coho salmon mid-river migration initiated (first 5% of migrants) after summer peak temperatures and following a threshold average daily temperature of 18 C°, but before fall storm events occurred. In most years, approximately 75% of the migrating coho salmon have moved past the Winchester Dam before fall storms initiated and when discharge remained less than the 11 year average for the month of November, more similar to summer than winter flow levels. Additionally, characteristic lengths and numbers of peaks within the distribution of annual migrations were attributable to the generational cohort that the migration belonged to despite the similarity in population size across all years. These patterns in the distribution of generational cohorts suggest an inherited timing response as well as highlight cohorts which may contain diminished sub-populations. The initiation of coho salmon spawning appears limited both by a thermal threshold of 12 C° in all basins, as well as by a minimal discharge threshold, which is unique to each stream. Continued spawning activity occurs as discharge remains elevated from fall levels. It is also notable that there was no statistical difference in the date of the initiation of spawning within each basin in a given year or across years at a given site. Together, these studies highlight the important role that the coho salmon genome plays in reproductive timing as well as the ways that fluvial thresholds limit reproductive behavior in time. Coho have survived because of their genome has been resilient when faced with environmental change. Future work should consider variability in fluvial conditions relative to coho salmon phenotypic plasticity over time. Coho salmon phenotypic plasticity will determine whether the rate of change of the hydrologic and thermal regimes important to coho salmon survival outpaces the coho’s ability to adapt. This study contributed to this future work by establishing baseline relationships between the behavior of a threatened species and measurable environmental thresholds.
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2286. [Article] Larval dispersal in marine fishes: novel methods reveal patterns of self-recruitment and population connectivity
Many marine fish populations are severely declining due to over-fishing, loss of both juvenile and adult habitats, and accelerating environmental degradation. Fisheries management and the implementation ...Citation Citation
- Title:
- Larval dispersal in marine fishes: novel methods reveal patterns of self-recruitment and population connectivity
- Author:
- Christie, Mark R.
Many marine fish populations are severely declining due to over-fishing, loss of both juvenile and adult habitats, and accelerating environmental degradation. Fisheries management and the implementation of marine protected areas (MPAs) and other conservation tools are currently hindered by large gaps in knowledge about larval dispersal and its subsequent effects on population dynamics and regulation. This lack of knowledge is due to the inherent difficulty associated with tracking miniscule marine fish larvae. Population genetics approaches are particularly promising, but current methods have been of limited use for inferring ecologically relevant rates of population connectivity because of the large population sizes and high amounts of gene flow present in most marine species. To address these issues, I developed novel genetic methods of identifying parent-offspring pairs to directly track the origin and settlement of larvae in natural populations. These parentage methods fully account for large numbers of pair-wise comparisons and do not require any demographic assumptions or observational data. Furthermore, these methods can be used when only a small proportion of candidate parents can be sampled, which is often the case in large marine populations. I also employed Bayes’ theorem to take into account the frequencies of shared alleles in putative parent-offspring pairs, which can maximize statistical power when faced with fixed numbers of loci. I accounted for genotyping errors by introducing a quantitative method to determine the number of loci to allow to mismatch based upon study-specific error rates. These novel parentage methods were applied to yellow tang (Zebrasoma flavescens, Acanthuridae) sampled around the Island of Hawai'i (measuring 140 km by 129 km) during the summer of 2006. We identified four parent-offspring pairs, which documented dispersal distances ranging from 15 to 184 kilometers. Two of the parents were located within MPAs and their offspring dispersed to unprotected areas. This observation provided direct evidence that MPAs can successfully seed unprotected sites with larvae that survive to become established juveniles. All four offspring were found to the north of their parents and a detailed oceanographic analysis from relevant time periods demonstrated that passive transport initially explained the documented dispersal patterns. However, passive dispersal could not explain how larvae eventually settled on the same island from which they were spawned, indicating a role for larval behavior interacting with fine-scale oceanographic features. Two findings together suggested that sampled reefs did not contribute equally to successful recruitment: (1) low levels of genetic differentiation among all recruit samples, and (2) the fact that the 4 documented parents occurred at only 2 sites. These findings empirically demonstrated the effectiveness of MPAs as useful conservation and management tools and highlighted the value of identifying both the sources and successful settlement sites of marine larvae. I next examined patterns of larval dispersal in bicolor damselfish (Stegastes partitus, Pomacentridae) collected during the summers of 2004 and 2005 from reefs lining the Exuma Sound, Bahamas (measuring 205 km by 85 km). Parentage analysis directly documented two parent-offspring pairs located within the two northern-most sites, which indicated self-recruitment at these sites. Multivariate analyses of pair-wise relatedness values confirmed that self-recruitment was common at all sampled populations. I also found evidence of “sweepstakes events”, whereby only a small proportion of mature adults contributed to subsequent generations. Independent sweepstakes events were indentified in both space and time, bolstering the direct observations of self-recruitment and suggesting a role for sweepstakes analyses to identify the scale of larval dispersal events. This dissertation provides insights into the patterns of larval dispersal in coral-reef fishes. The coupling of direct (e.g., parentage) and indirect (e.g., assignment methods, sweepstakes analyses) methods in conjunction with continued technological and methodological advances will soon provide large-scale, ecologically relevant, rates of larval exchange. By uncovering the dynamics of these enigmatic processes, the implementation of conservation and management strategies for marine fishes in general will undoubtedly experience greater success.
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2287. [Article] Snag longevity, bird use of cavities, and conifer response across three silvicultural treatments in the Oregon Coast Range
In the interest of meeting multiple forest management goals that include maintenance of wildlife, particularly cavity-nesting birds, uneven-aged silvicultural treatments are used increasingly in the Pacific ...Citation Citation
- Title:
- Snag longevity, bird use of cavities, and conifer response across three silvicultural treatments in the Oregon Coast Range
- Author:
- Walter, Scott T.
In the interest of meeting multiple forest management goals that include maintenance of wildlife, particularly cavity-nesting birds, uneven-aged silvicultural treatments are used increasingly in the Pacific Northwest. However, questions remain regarding the responses of cavity-nesting birds and residual green trees to different harvest intensities and patterns. To study these issues, between 1989 and 1991 the Oregon State University College of Forestry Integrated Research Project (CFIRP) applied 3 silvicultural treatments to 30 mature (85-125 year old) Douglas-fir stands in the Oregon Coast Range. Silvicultural treatments consisted of group-selection cuts (18 stands with 33% of the timber volume extracted from 0.2-0.6 ha patches), two-story regeneration harvests (6 stands with 75% scattered removal of the timber volume resulting in 20-3 0 distributed residual trees/ha), and clearcuts (6 stands that retained 1.2 mature green trees/ha). In addition, 939 conifers 53 cm diameter at breast height [DBH]) were topped to create snags in clustered and scattered arrangements. In the current study, CFIRP stands were utilized to 1) test for differences in cavity-nesting bird use of snags across silvicultural treatments and snag arrangements 10 years after harvest, 2) compare 10 year with 5 year nesting levels, 3) evaluate associations between snag characteristics and cavity nest site location, 4) quantify snag fall, 5) assess silvicultural treatment effects on residual tree growth and condition, and 6) quantify tree mortality. Snags and topped conifers that remain alive were observed for nesting and foraging use during the 2001 breeding season. Eight species of birds nested in created snags and a mean of 5.1 total cavities/snag were found one decade after creation. However, no active nesting was observed in topped trees that remained alive. Higher cavity-nesting bird levels, species richness, and species diversity occurred in open-canopy stands (two-story and clearcut treatments) compared to closed-canopy stands (group-selection treatment). Bird species composition was most similar between two-story and clearcut stands, and least similar between clearcut and group-selections stands. No difference was found in nesting or foraging levels between clustered and scattered snags. Active nests in created snags were most commonly located in the top 25% of bole, cavities on average faced northeast, and created snags with and without dead branches received equal nesting use. Compared with 6 years prior, the mean number of cavities per created snag increased 3.3- to 6-fold, and 4 additional avian species were observed nesting. One topped conifer fell in the decade since creation. Residual green trees (n = 848) were measured for growth and condition from November, 2001 to February, 2002. Across silvicultural treatments, residual green tree basal area, DBH, and height growth, and crown width and crown fullness did not differ among silvicultural treatments 10-12 years following harvest. Overall, 45% of trees experienced greater basal area growth in the decade following harvest than in the decade prior to harvest. Among silvicultural treatments, mean live crown ratio (live crown length/total tree height) of residual trees was significantly greater (0.74) in clearcuts and the percentage of trees with epicormic branching (35%) was significantly higher in two-story stands. Over the last decade residual tree mortality resulted in 134 standing dead trees (snags) and 185 blowdowns. Two-story stands experienced the highest recruitment of snags (0.76 per ha) and blowdowns (1.12 per ha). Results from this study suggest that topped, large conifers provide snags that offer valuable nesting and foraging habitat for cavity-nesting birds during the first decade after treatment, if the tree dies. Snags in both clustered and scattered arrangements appear to receive equal use by cavity-nesting birds. Also, snags created by topping may have the potential to stand for several decades in the Oregon Coast Range. Furthermore, although silvicultural treatments in this study did not appear to affect residual tree basal area growth during the first 10 years after treatment, partial harvests can promote increased diversity in stand structural complexity, which includes longer tree crowns, epicormic branching, and new snag recruitment, that also can benefit cavity-nesting bird populations through increased nesting and foraging opportunities.
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Coral reef ecosystems are the oceanic equivalent of tropical rainforests, in terms of biodiversity. The estimated 1,037,000 square kilometers worldwide of reef provide habitat for over one million species ...
Citation Citation
- Title:
- An evaluation of the likelihood of successful implementation of the long term coral reef monitoring program on the Commonwealth of the Northern Mariana Islands
- Author:
- Kylstra, Pam
Coral reef ecosystems are the oceanic equivalent of tropical rainforests, in terms of biodiversity. The estimated 1,037,000 square kilometers worldwide of reef provide habitat for over one million species of plants and animals (Hinrichsen, 1997). Coral reefs are important to the economy of coastal nations because of the fisheries and tourism industries they support. Reef ecosystems provide a host of important natural services such as storm buffering, a protein source for islanders, breeding and nursery grounds for marine organisms, water filtration and a source of biomedically important products. Coral reef areas also have aesthetic and intrinsic value that is reason enough to protect them. Coral reefs are also among the most endangered ecosystems on Earth. Naturally occurring disturbances are compounded by the impacts of anthropogenic disturbance. Factors that threaten the health of coral reef ecosystems on a global scale include global warming, the continuing increase in coastal populations and associated impacts such as nutrient pollution, sedimentation and runoff, coral mining, ship groundings, overfishing, and recreational overuse. Globally, coastal areas accommodate about 60% of Earth's human population. A significant portion of the population lies within tropical regions. This population pressure subjects coral reef environments to effects of increased competition for coastal resources, increased coastal pollution and problems related to coastal construction. The synergistic effect of stressors has been the irreversible degradation worldwide of 10% of reefs and another 60% in critical condition leaving, only 30% as stable (Wilkinson, 1993). The coral reefs of the Commonwealth of the Northern Mariana Islands (CNMI) are a good example of how the combination of increasing human population and the associated environmental pressure has resulted in degradation of the reef ecosystem. The CNMI has undergone significant change in economic and population growth within the past decade. To accommodate the rapid and continuing development of the tourism industry, numerous golf courses and resort hotels have been constructed on Saipan. The population of Saipan has increased over 30% in the last ten years. Currently, the local/resident population is 60,000 while the visitor population is 750,000 per year. This rapid growth has had serious ecological consequences. Coral roads have been converted to four lane highways and infrastructure such as septic tank systems has not been improved to meet higher demand. More and more development projects have been proposed without adequate consideration of environmental impacts. Conflicts over the use and conservation of marine and watershed resources continue to arise. The continuing decline of reef systems globally and in specific areas like the CNMI, highlights the need for effective methods of assessing change in nearshore ecosystems. This paper explores the ways that coral reef monitoring can provide information about reef health that serves to affect positive changes in management strategies for marine systems. Using a criteria drawn from case study comparisons of ongoing, well established coral monitoring programs and evaluation framework proposed by policy analysts Using criteria drawn from case, the Long Term Marine Monitoring Program (LTMMP) on Saipan, CNMI is evaluated. The evaluation provides insight about coral monitoring plan components that are essential to the effectiveness of coral reef monitoring programs. This report is an outgrowth of an internship the author performed with the CNMI Division of Environmental Quality on the island of Saipan from June to October of 1997. The University of Oregon Micronesia and South Pacific Program and the government of the Commonwealth of the Northern Mariana Islands (CMNI) sponsored the internship project. The objectives of the internship were to assist in field data collection and continuing development of the ongoing Long Term Marine Monitoring Plan (LTMMP) Assist and instruct Marine Monitoring Team (MMT) members in basic computer skills, understanding of data applicability, management, interpretation and analysis, basic biology and resource management techniques as it relates to marine monitoring work Facilitate inter-governmental agency coordination of marine monitoring activities Assess likelihood of success and explore challenges facing Saipan in implementation of the monitoring program This report first describes functions and services provided by coral reefs and an introduction to the stresses and disturbances that compromise the health of reef systems globally. Using examples from case studies of established marine monitoring programs, this report considers how effective monitoring can reveal changes in the reef system over time, enabling conservation measures to be taken. It then turns to the island of Saipan and briefly describes the environmental and socio-economic framework within which the coral reef related provisions of the CNMI coastal management program are considered. This background information is used to evaluate the Long Term Marine Monitoring Plan currently in place on the CNMI. This evaluation provides insight into the challenges to implementation of coral reef monitoring plans and recommendations for improvements in the LTMMP on Saipan.
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2289. [Article] The use of ơ15N and ơ¹³C to analyze food webs and identify source-sink relationships in riparian canopy vegetation of the Oregon Coast Range
In the Coast Range of western Oregon, some natural resource managers are converting red alder-dominated riparian areas to conifers to increase the future source of in-stream large wood for salmonid habitat. ...Citation Citation
- Title:
- The use of ơ15N and ơ¹³C to analyze food webs and identify source-sink relationships in riparian canopy vegetation of the Oregon Coast Range
- Author:
- Scott, Emily E.
In the Coast Range of western Oregon, some natural resource managers are converting red alder-dominated riparian areas to conifers to increase the future source of in-stream large wood for salmonid habitat. However, studies in Alaska have shown red alder-dominated riparian areas support greater invertebrate biomass compared to conifer-dominated areas. In addition, red alder can influence the nutrient dynamics of a site with N-rich litter inputs. Thus, these forest conversions have the potential to change riparian food webs and nutrient dynamics. The objectives of this thesis were to determine the utility of natural abundance stable isotopes of nitrogen and carbon in food web analyses and to describe nutrient dynamics and source-sink relationships in red alder- and Douglasfir- dominated riparian areas of the central Oregon Coast Range. We address three questions in this study: 1) What is the degree and source of δ15N and δ13C variation in foliage of Douglas-fir and red alder? 2) Are Douglas-fir and red alder isotope signatures sufficiently distinct to be used in food web analysis? and 3) Are there differences in nutrient dynamics and source-sink relationships between Douglasfir- and red alder-dominated riparian areas? To address these questions, we sampled foliage, litterfall, forest floor material, and soil from ten Douglas-fir- and red alder-dominated riparian sites as well as foliage from plantation Douglas-fir and red alder for δ15N, δ13C, and nutrient concentrations. Douglas-fir had greater variation in foliage δ15N within a tree crown, within a site, and among sites than red alder. Red alder had consistent foliage at all scales, near 1 .5%o, a value that is characteristic of nitrogen fixing species. Both species had similar levels of variation in foliage δ13C at all scales. Douglas-fir was slightly enriched in '3C compared to red alder suggesting greater water-use efficiency in Douglas-fir. Overall, the difference between δ15N and δ13C of red alder and Douglas-fir at our study sites were, on average, less than 2.O%o. It is unlikely stable isotopes could be used over broad geographic areas as a tool for determining the contributions of Douglas-fir versus red alder to food webs, although site-specific research may be possible where Douglas-fir and red alder demonstrate greater isotopic differences. Douglas-fir and red alder exhibited opposite source-sink relationships with soil for N exchange: Douglas-fir was a sink for soil N whereas red alder served as a N source. Douglas-fir sites had a higher N status and lower soil δ15N along the stream compared to upslope, trends not found at red alder sites. Soil δ15N near streams on Douglas-fir sites was similar to the soil δ15N on red alder sites suggesting that a legacy of past red alder along the stream may have contributed to the N status and soil δ15N gradients on Douglas-fir sites. Soil δ15N and soil δ15N did not indicate a presence of marine N on our sites. δ15N and δ13C of foliage and soil suggested decomposition processes of leaf litter differed between Douglas-fir and red alder, likely due to different lifter chemistries and possible influences on decomposition enzymes. A shift in species composition from red alder-dominated to Douglas-fir-dominated riparian areas would alter source-sink relationships with soil N and litter decomposition processes, although some legacies of soil enrichment in N by red alder would persist.
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2290. [Article] Population genetics of ranid frogs : investigating effective population size and gene flow
This dissertation focuses on the evolutionary forces of genetic drift and gene flow in frog populations. The balance of these two forces and the force of mutation largely determine the amount of neutral ...Citation Citation
- Title:
- Population genetics of ranid frogs : investigating effective population size and gene flow
- Author:
- Phillipsen, Ivan Clayton
This dissertation focuses on the evolutionary forces of genetic drift and gene flow in frog populations. The balance of these two forces and the force of mutation largely determine the amount of neutral genetic variation within populations as well as the degree of genetic similarity among populations. The stochastic evolutionary change caused by genetic drift can be quantified through the use of the effective population size (N[subscript e]) parameter. The effective size of a population is the number of breeding individuals in a conceptual, ideal population that would evolve by genetic drift at the same rate as the real population being studied. How a population responds to mutation, selection, and gene flow depends on N[subscript e], rather than the actual census population size (N). In most natural populations, N[subscript e] is considerably smaller than N. For these reasons, N[subscript e] is a fundamental parameter in basic population genetics theory as well as in applied conservation genetics. The degree of neutral genetic similarity between populations is highly dependent upon gene flow. When gene flow between a pair of populations is low, the populations are likely to become genetically differentiated. Conversely, when gene flow between populations is high, the populations will tend to be more genetically similar. Amphibians are good model organisms for studying genetic drift and gene flow because they tend to exhibit strong population structure at small spatial scales. This is a consequence of their generally small population sizes, natal philopatry, limited dispersal capabilities, and restricted habitat requirements. They are expected to have easily-detectable signatures of spatial genetic structure and genetic drift. Amphibians can be used as models to further our understanding of evolutionary processes and that understanding can be applied to the conservation of amphibians. Equipped with knowledge of what naturally influences genetic drift and gene flow in amphibians, we can apply the principles of population genetics to mitigate the genetic consequences of amphibian declines. In Chapters 2 and 3, I used molecular genetic data from frog populations to investigate N[subscript e] and the related parameter N[subscript b] (the effective number of breeders). Chapter 2 is a study of a single population of the Oregon spotted frog (Rana pretiosa). My aim was to determine where in the life cycle of this species the greatest reduction in N[subscript b] occurs. I used genetic data from microsatellites to estimate N[subscript b] at two different life stages, eggs and metamorphs, and found that estimates of N[subscript b] were similar at both stages. This result suggests that inflated variance in family size due to egg mass mortality is not a primary cause of N[subscript e] reductions relative to N in this species. Chapter 3 is a comparison of N[subscript e] estimates within and among four species of frogs in the family Ranidae: R. pretiosa, R. luteiventris, R. cascadae, and Lithobates pipiens. I obtained N[subscript e] estimates for 90 populations across the four species, using microsatellite data and several different estimators. The first three species and the western populations of L. pipiens have very small effective sizes (< 50). Eastern populations of L. pipiens are much larger, with N[subscript e] estimates in the hundreds and thousands. I also found significant correlations between N[subscript e] estimates and latitude, longitude, or altitude in R. luteiventris and L. pipiens. Chapter 4 is a study of gene flow among populations of the Cascades frog (Rana cascadae) in the Olympic Mountains of Washington. I quantified genetic differentiation among 22 R. cascadae populations with data from microsatellite markers and used a landscape genetics approach to identify environmental features that have strong influences on gene flow in this species. I used a Random Forests statistical procedure to assess which of several structural connectivity models and 15 landscape variables explained the most variation in genetic distances among populations. I found that the best-fitting Random Forests models were based on different structural connectivity models for two datasets: 'within' and 'between' genetic clusters of populations. The landscape variables identified as the most important also differed across the two datasets, suggesting that landscape influences vary across spatial scales. The results presented in this dissertation led to an increased understanding of effective population size in ranid frogs and of the environmental factors that influence population structure in R. cascadae. These studies provide a foundation for further research on the specific factors that influence genetic drift and gene flow in these species.
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Quaking aspen (Populus tremuloides Michx.) is known to be a widely distributed, shade-intolerant and short-lived hardwood found in both seral, even-aged and stable, uneven aged stands. There have been ...
Citation Citation
- Title:
- Influence of silvicultural treatments, overstory, and understory vegetation on quaking aspen (Populus tremuloides) regeneration in southeastern Idaho
- Author:
- Muñoz, Bethany L.
Quaking aspen (Populus tremuloides Michx.) is known to be a widely distributed, shade-intolerant and short-lived hardwood found in both seral, even-aged and stable, uneven aged stands. There have been reports of extensive aspen mortality, crown thinning, and branch dieback across North America that have been linked to the occurrence of severe droughts since 2001-2002. Because of reports of low aspen regeneration across the Intermountain West, as well as predictions of increases in aspen regeneration in the Northeastern US, researchers and land managers have now focused on managing aspen stands under the assumption that there are multiple aspen types. They have focused on improving resilience within quaking aspen stands with changing ecological conditions. For this thesis I focused on a project the Bureau of Land Management (BLM), Pocatello Field Office initiated in part to improve aspen restoration and resilience of stands in Soda Springs, ID. The BLM conducted two mechanical removal treatments: cut and pile, and slash/lop and scatter. In addition several sites were broadcast burned to reduce fuel loads and conifer density, to enhance aspen regeneration and improve aspen stand resilience. According to the Soda Springs Hills Fuels Reduction and Ecosystem Restoration Environmental Assessment (EA), the BLM aimed to meet the objective of 2500 quaking aspen suckers per ha (1000 suckers per ac) within the two years following treatment, an index of treatment adequacy. My primary objective for this thesis was to assess the influence of each silvicultural treatment, including the change in overstory and understory vegetation, on regeneration of aspen. Mean aspen regeneration two growing seasons after treatment was 11,532 suckers/ha on sites that received slash/lop and scatter treatment, followed by broadcast burning. With these high levels of suckering, there were also low densities of residual overstory conifers (≤ 4 trees/ha with a basal area ≤ 2 m²/ha). In comparison, sites that received the cut and pile treatment followed by a broadcast burn had a mean aspen regeneration of 44 suckers/ha, with higher densities of overstory conifers (≥ 32 trees/ha with a basal area ≥ 26 m²/ha). In slash/lop and scatter treatments without burning, sucker densities were as high as 1117 suckers/ha with low densities of conifers (0 trees/ha). In comparison, the site that received the cut and pile treatment without burning had an aspen regeneration of 0 suckers/ha, with a high density of conifers (36 trees/ha with a basal area of 47 m²/ha). Overall, sites with low residual overstory cover of large conifer trees (< 4 trees/ha), regardless of the treatment, had higher sucker densities two growing seasons after treatment (6244 suckers/ha, on average) than those seen in sites with a remnant overstory of >16 trees/ha (29 suckers/ha, on average). Also, sites that were burned, regardless of the mechanical treatment used, had higher sucker densities (11,244 suckers/ha) than those seen in sites that were not burned (576 suckers/ha). When comparing aspen sucker densities to competing understory woody cover following mechanical treatment, aspen sucker density was lowest (411 suckers/ha) on the site where both tree and shrub percent cover were highest (10 and 16%, respectively). Suckering appeared to be positively correlated with grass cover, however, with as high as 1117 suckers/ha growing with a high percentage of grass cover (≥ 26 %), on sites measured for change in understory following mechanical treatment. Results were collected on a small number of sites and thus have limited statistical significance. However, we are confident that observed trends have values for managers. We suggest that transects should continue to be monitored to observe the long-term effects of silvicultural treatments on overstory and understory vegetation, which are likely to be influenced by climate variability and other disturbances into the future.
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The Steller Sea Lion Research Initiative was passed in 2001 to provide funding to help scientists determine causes and solutions for the population crash of Steller sea lions (Eumetopias jubatus). In response ...
Citation Citation
- Title:
- Steller sea lions (Eumetopias jubatus) of Oregon and Northern California: seasonal haulout abundance patterns, movements of marked juveniles, and effects of hot-iron branding on apparent survival of pups at Rogue Reef
- Author:
- Scordino, Jonathan
The Steller Sea Lion Research Initiative was passed in 2001 to provide funding to help scientists determine causes and solutions for the population crash of Steller sea lions (Eumetopias jubatus). In response to need to understand population dynamics of Steller sea lions, NOAA Fisheries has spearheaded a large-scale, range-wide research program. The study involved capturing and hot-iron branding sea lions at rookeries from northern California around the Pacific Rim to Russia to provide individually recognizable animals for studies of behavior and vital rates. I report the results of monitoring pups branded and tagged at Rogue Reef, Oregon and St. George Reef, California to determine movement patterns and the affects of branding on apparent survival of Steller sea lion pups immediately after branding. Counts of Steller sea lion adult female, adult male, juveniles, and pups were collected at haulouts and rookeries of Oregon and northern California from 2002 through 2005. Movement patterns of Steller sea lions were inferred from count data. Adult males were seasonal inhabitants of Oregon and California during the breeding season from May through September before dispersing to northern feeding grounds. Females, juveniles, and pups were dispersed throughout haulouts in Oregon and northern California during all seasons but have seasonally high concentrations at Sea Lion Caves, Oregon in the winter and at the breeding rookeries during the summer breeding season. The high wintertime abundance of females and pups at Sea Lion Caves suggests that it should be considered as critical habitat for Steller sea lions of the eastern stock. Resights of marked sea lions collected between northern California and Alaska between 2001 and 2005 were analyzed to determine juvenile and pup dispersal patterns. Most pups stay close to their natal rookery, although 9 - 22% of individuals each year were observed to disperse further than 500 km. As 1-year olds, the mean maximum dispersal range expanded, which may have been a sign of weaning. Sexually dimorphic patterns in sea lion movements were apparent at 3 years of age as males were observed to disperse farther north than females. The percentage of females observed at their natal rookery increased each year to a maximum of 87% as 4-year-olds. This suggested that sexual maturity occurs at, or close to, 4 years of age for females. Branding provided a useful tool for analyzing movements of Steller sea lions, yet it may have impacts on survival of individuals. Concerns raised by NOAA Fisheries over branding impacts on pup survival were addressed with a study at Rogue Reef in 2005. One-hundred-and-sixty pups captured on 18 July, 2005 were randomly assigned to a treatment of flipper tag only (unbranded pups) or flipper tag and hot-iron branding (branded pups). Aside from the treatment of branding, all pups were handled and treated identically. Over the 73-day course of this study, I found lower apparent survival for branded pups than unbranded pups, with a final apparent survivorships of 0.23 (95% CI 0.01 – 0.48) for branded pups and 0.46 (95% CI 0.15 – 0.77) for unbranded pups. Apparent survivorship includes both mortality and emigration, so differences may be due to differences in emigration rates of the two groups, mortality rates, or both. The scope of inference for this study is only to Rogue Reef in 2005. However, it should provide a good model for future brand evaluation studies at other rookeries and for other pinniped species. Branding is currently the best and only available tool for long-term studies of survival, reproduction rates, and age at sexual maturity which are all critical for demographic models. Nonetheless, researchers should assess the impacts of branding at each rookery, and will need to consider whether knowledge from branding Steller sea lions is worth the potential reduction in pup survival or change in pup emigration behavior observed in this study.
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Pacific Northwest prairies have become significantly reduced in extent, and in the Willamette Valley of Oregon, less than one percent of native upland prairies remain. Many species have been impacted by ...
Citation Citation
- Title:
- Responses of Pacific Northwest prairies to soil nutrient manipulations : implications for restoration of Castilleja levisecta and control of invasive species
- Author:
- Lawrence, Caitlin Elizabeth
Pacific Northwest prairies have become significantly reduced in extent, and in the Willamette Valley of Oregon, less than one percent of native upland prairies remain. Many species have been impacted by this extreme loss of habitat, including Castilleja levisecta (golden paintbrush), a threatened hemiparasitic forb species endemic to the Pacific Northwest. Many of the prairie fragments that remain are poor quality, and face the threat of invasion from non-native species and a loss of biodiversity. These non-native species pose an obstacle to restoration and to the reintroduction of threatened and endangered species. Nutrient enrichment has been shown to promote increased invasion of communities, decrease success of native species, and decrease biodiversity. A way to counter these effects is through carbon addition to the soil which stimulates microbial activity and immobilizes nutrients, making them unavailable to plants. This strategy has potential as a restoration tool to improve conditions for native species, which are often outcompeted under high nutrient conditions. We tested the efficacy of carbon addition for controlling non-native species and restoring C. levisecta in two Willamette Valley prairies. We created treatments of varying nutrient availability and measured the responses of the plant community and of C. levisecta. Experimental plots were established in autumn 2012 with either carbon (sucrose) addition, ambient soil nutrients (controls), or nutrient addition (NPK fertilizer). Nutrient treatments were reapplied throughout the length of the experiment. Crossed with these treatments in a fully factorial design were seeding treatments of C. levisecta and of thirteen other native species, to increase the diversity of the plant community, providing host plants for C. levisecta, a hemiparasitic plant. In the two growing seasons following treatment we conducted plant community surveys and counted and measured seedlings of C. levisecta to determine the effects of the nutrient manipulations and seeding treatments on the community overall and on this threatened plant. Community composition differed significantly between the different nutrient treatments (perMANOVA, p<0.001) at both study sites, and in both years of the experiment. Mean total vascular plant cover was significantly reduced by carbon addition compared to ambient nutrient availability, and increased by nutrient addition. Native grasses were unaffected by nutrient manipulation at either site, whereas non-native grasses were greatly reduced by carbon addition and increased by nutrient addition, compared to ambient soil nutrient availability. Non-native forbs were also greatly reduced by carbon addition, and were also reduced by nutrient addition by the second year of the experiment. Richness of non-native species was more affected by nutrient manipulation than richness of natives, and was either increased or unaffected by nutrient enrichment and decreased by carbon addition. Some non-native species were found to be highly affected by the nutrient manipulation, while others were not, suggesting that carbon addition may be an effective control for only certain non-native species. At both sites, C. levisecta emergence was lower in carbon addition plots compared with controls. In nutrient addition plots, C. levisecta emergence was higher at one site but lower at the other compared with controls, suggesting that nutrient addition may be beneficial only under certain conditions. Additionally, by the second year of the experiment, there was no difference in C. levisecta numbers between the control and nutrient addition plots at one site, and there were fewer in the nutrient addition plots than in controls at the other site. The seeding of additional native species increased community richness but had little effect on diversity and no effect on C. levisecta establishment. Overall, these results suggest that nutrient enrichment can promote the success of non-native species and that carbon addition can be used to counter these effects on a species- and site-specific basis. However, carbon addition did not improve reintroduction success of a threatened plant species, C. levisecta, and the effects of nutrient addition on its success after two years were mixed.
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2294. [Article] The ecology and production dynamics of four black fly species (Diptera:simuliidae) in western Oregon streams
Ecological and production studies of Prosimulium caudatum Shewell, P. dicum Dyar and Shannon, Simulium arcticum Malloch and S. canadense Hearle (Diptera: Simuliidae) were made in 1971 and 1972 in three ...Citation Citation
- Title:
- The ecology and production dynamics of four black fly species (Diptera:simuliidae) in western Oregon streams
- Author:
- Speir, Jon A.
Ecological and production studies of Prosimulium caudatum Shewell, P. dicum Dyar and Shannon, Simulium arcticum Malloch and S. canadense Hearle (Diptera: Simuliidae) were made in 1971 and 1972 in three streams near Corvallis, Oregon. The purpose of the study was to characterize the biology and population dynamics of larvae, and to compare the production of the four species under various spatial and temporal conditions. A total of 54 annual production estimates was derived utilizing 37 stations. In addition, 17 annual drift and 22 emergence (as pupae) determinations were made. Data on the physical and chemical characteristics of the streams, and on larval associates, parasites, predators and food types were obtained at all stations. Laboratory experiments provided data on feeding rates and predator impact. The two Prosimulium species always coexisted, and occurred in all streams. Simulium arcticum and S. canadense were studied in two streams only. All species were univoltine and had egg stage durations exceeding 40 weeks. Prosimulium spp. larvae appeared in mid-February and were on riffles for an average of 10.3 weeks. Simulium arcticum hatching began about six weeks later. Larvae of this species developed in an average of 8.8 weeks. Development of S. canadense began about nine weeks later than for Prosimulium spp. but lasted nearly as long. All four black flies had six larval instars. All larvae were filter feeders, and fed primarily on the suspended materials in the streams. Detritus made up from 65-90% of the diet, with the rest being filamentous algae. Alimentary tract clearing of larvae was usually accomplished in less than one hour. Black fly immatures were associated with about 75 other benthic insect species. Of these, nine were likely important simuliid natural enemies. Fish were minor black fly predators. Gastromermis nematodes occurred in about 3% of all mature simuliid larvae. Annual losses due to drift averaged about 6%. Simuliid drift appeared to be a function of standing crop density. Growth-related crowding may also have been a factor. Effects of diel light conditions, temperature and discharge were minimal. A diel emergence pattern existed for Simulium spp. adults only. The time between emergence and oviposition was likely about 0.5 week for all species. Emergence at most stations was single peaked, and averaged 3. 6 weeks in duration. The sampling universe at each station could be effectively partitioned to exclude areas where larvae did not exist. Thus, the weekly stratified random sampling program provided population estimates with error terms of usually 15% or less. All quantitative data were expressed on a per m² of overall riffle basis (and not on a per m² of habitat basis) to make the study more comparable to other benthic research. Density, biomass and production differences between stations, streams and years were minimal for each species, and therefore were treated as replicates. Initial densities ranged from over 11000 to about 16000 larvae/m². Mortality for aggregates of all species was similar, with about 70% of all losses occurring during the first half of larval life. Growth for all species was generally logistic and averaged over 0.090 gig per day annually. Production, averaged for 1971 and 1972, in g/m² , was: P. caudatum, 2.644; P. dicum, 2.908; S. canadense, 3. 141; and S. arcticum, 3.950. This species ranking also held for initial density, mean density and mean biomass. Biomass and production were almost always closely correlated. Mortality variations had a greater influence on production than did growth rate. Averaged for all species, the mean total mortality due to drift and parasites was 6.2% and 0.5% respectively. An average of 10.7% of colonizing larvae survived to emerge. Predator-caused losses were estimated to provide the 82.6% needed to balance the loss budget. Black fly larvae were the dominant processor of suspended materials in the three streams. On the average, they outnumbered all other primary consumers combined on riffles by a factor of 27. Simuliid larvae functioned as the primary prey reservoir for as many as 20 species of insect carnivores from February through June of both years.
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2295. [Article] Systematics of the salamander genus Dicamptodon strauch (Amphibia:Caudata:Ambystomatidae)
Dicamptodon is the single, extant genus of the ambystomatid subfamily Dicamptodontinae. Two species, D. ensatus (Eschscholtz) and D. copei Nussbaum are recognized. D. ensatus is found in the forested, ...Citation Citation
- Title:
- Systematics of the salamander genus Dicamptodon strauch (Amphibia:Caudata:Ambystomatidae)
- Author:
- Nussbaum, Ronald A.
Dicamptodon is the single, extant genus of the ambystomatid subfamily Dicamptodontinae. Two species, D. ensatus (Eschscholtz) and D. copei Nussbaum are recognized. D. ensatus is found in the forested, mountain regions of northwestern California and western Oregon, in the Willapa Hills and Cascade Mountains of Washington, in extreme southwestern British Columbia, and in the northern and central Rocky Mountains of Idaho. D. copei is found in the Olympic Mountains, Willapa Hills and southwestern Cascades of Washington; and in the vicinity of the Columbia River Gorge in extreme northwestern Oregon. The two species are sympatric in the Columbia River Gorge, southern Willapa Hills, and southwestern Cascades of Washington. The two species differ, among other characters, in blood serum proteins, sensitivity to thyroxine, mode of life history, body size, relative head size, limb length, tail height, tooth number, gill raker number, color, and degree of ossification of skeletal elements. Geographic variation is prominent in D. ensatus. Multivariate analysis of morphometric characters of larval populations discriminates three groups: a Rocky Mountain Group, a Cascade and Oregon Coast Range Group, and a Californian Group. The first two groups seem to be more similar to each other than either is to the Californian Group. The Californian Group can be divided into a southern subgroup and a northern subgroup; and the northern subgroup can be further separated into a coastal subgroup and an interior highlands subgroup. These groups are all more-or-less verified by analysis of color of larvae and adults, and morphometric characters of adults. These groups correspond geographically with major features of topography in the Pacific Northwest. The California Group is confined south of the geologically old and complex Klamath-Siskiyou Mountains. The southern Californian subgroup is found south of the "North Coast Divide", and the northern subgroup is found north of this Divide in an area of northwestern drainage. The interior highlands subgroup of the northern Californian subgroup is found in the higher, summer-dry mountains of northern California where the substrate is complex and of a different origin than the coastal substrate. Strong morphoclines occur across the Klamath-Siskiyou Region into southwestern Oregon. The Rocky Mountain Group is separated from the Cascade and Oregon Coast Range Group by the broad, arid Columbia Plateau. Variation is slight over the relatively small range of D. copei, and what variation exists seems to be a function of geographic distance. The dicamptodontines have been an evolutionarily conservative group confined to the humid temperate, Arcto-Tertiary environments of western North America throughout their Cretaceous and Tertiary history. A remnant of the once wide-spread, ancestral habitat occurs today in the humid fog belt of northwestern California and southwestern Oregon. D. ensatus living in this area today exhibit the most primitive features of all living Dicamptodon. These include: large heads, long limbs and tails, many teeth and gill rakers, propensity to transform, and perhaps the habit of vocalizing as a terrestrial, defensive adaptation. D. copei is viewed as a relatively recent derivitive of an ensatus-like ancestor. This ancestor is believed to have had a propensity for neoteny and body attenuation associated with life in the extreme climatic, physical, and biotic environments imposed by Pleistocene glaciation. Isolation in western Washington during a glacial maximum allowed these tendencies, along with small body size, to be selected for, unhampered by gene flow from outside populations. It is thought that the ensatus-like ancestor of D. copei was more similar to recent northern populations of D. ensatus than to recent Californian populations of D. ensatus. Californian populations were relatively unaffected by Pleistocene climatic extremes, as they passed this period in the milder, ancestral environment of southern, coastal latitudes. During the last glacial maximum, the Rocky Mountain populations were probably continuous with populations on the lower eastern slopes of the Washington Cascades, via a connecting, wet, forested parkland, which existed south of the Cordilleran ice sheet in north-central Washington. This parkland was broken up after the ice retreated, during the Altithermal interval, about 7-4,000 years ago, and it was at this time that the Rocky Mountain Group became isolated. Postglacial readjustments in the ranges of D. copei and D. ensatus account for their current narrow zone of sympatry. Subspecies of D. ensatus and D. copei are not recognized.
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2296. [Article] Spatial Association of Humpback Whales (Megaptera novaeangliae) and their Prey in the Southern Gulf of Maine, USA
Efficient foraging strategies result in a predator spatially overlapping with its prey, foraging in the most profitable patches, and minimizing the time transiting between patches. Previous studies investigating ...Citation Citation
- Title:
- Spatial Association of Humpback Whales (Megaptera novaeangliae) and their Prey in the Southern Gulf of Maine, USA
- Author:
- Kirchner, Theresa
Efficient foraging strategies result in a predator spatially overlapping with its prey, foraging in the most profitable patches, and minimizing the time transiting between patches. Previous studies investigating baleen whale foraging strategies have generally focused on investigating spatial overlap with prey patches, patch profitability or movement within feeding grounds. The present study investigated the fine-scale strategies of movement between individual prey schools and larger prey patches in humpback whales (Megaptera novaeangliae) bubble-feeding on sand lance (Ammodytes spp.) in and around the Stellwagen Bank National Marine Sanctuary, USA. The goal was to investigate the presence of hierarchically nested spatial structures in both sand lance patches and whale bubble-feeding behavior, and to compare the scales and geometry of these patches between predator and prey behavior on each hierarchical scale. Furthermore, the profitability of sand lance schools in feeding areas was investigated. Using animal-borne tag technology to record underwater movement of whales in combination with surface observations of whale behavior, the locations of bubble-feeding events were identified. Concurrent hydroacoustic measurements of the prey distribution in the water column were used to identify the locations and energetic parameters of sand lance schools around tagged whales. First Passage Time analysis was used to determine the spatial scale of individual bubble-feeding events. Based on spatial proximity, feeding events and prey schools were grouped into larger feeding bouts and prey patches to investigate the presence of hierarchically nested scales. Up to three hierarchy levels were found in bubble-feeding behavior of nine whales tagged on six days between 2008 and 2012, and up to five hierarchy levels in the sand lance prey field around the tagged whales. There was a significant positive correlation between the lengths of whale bubble-feeding bouts and the lengths of sand lance patches over three common hierarchy levels. On each hierarchy level, the lengths of whale bubble-feeding bouts were significantly smaller than those of sand lance patches. Mean inter-feeding bout distances were significantly positively correlated with mean inter-prey patch distances over two hierarchy levels. Mean distances between feeding events were similar to the mean distances between prey schools. On larger hierarchy levels, mean inter-bout distances were greater than mean distances among prey patches. Mean school height and density tended to be greater in schools recorded inside than outside of feeding bout areas. The prey field structures found here were likely a result of the specific habitat requirements of sand lance. The results of this study suggest that the tagged whales were able to adapt their foraging movement to the structure of the prey field. By feeding on neighboring schools, whales could minimize the time spent between prey schools. On larger spatial scales, whales did not feed on neighboring prey patches. This could be a result of decreased abilities to find the nearest patch, or because, rather than restricting their foraging movement to neighboring patches, the whales were targeting specific patches. The foraging movement observed in this study led to spatial overlap of the tagged whales with sand lance schools that were characterized by properties rendering them more energetically profitable for bubble-feeding whales. While hierarchically structured foraging movement has been found in other marine predators, this is the first study that demonstrates this kind of foraging mechanism for baleen whales.
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2297. [Article] The influence of biophysical feedbacks and species interactions on grass invasions and coastal dune morphology in the Pacific Northwest, USA
Biological invasions provide a unique opportunity to study the mechanisms that regulate community composition and ecosystem function. Invasive species that are also ecosystem engineers can substantially ...Citation Citation
- Title:
- The influence of biophysical feedbacks and species interactions on grass invasions and coastal dune morphology in the Pacific Northwest, USA
- Author:
- Zarnetske, Phoebe Lehmann, 1979-
Biological invasions provide a unique opportunity to study the mechanisms that regulate community composition and ecosystem function. Invasive species that are also ecosystem engineers can substantially alter physical features in an environment, and this can lead to cascading effects on the biological community. Aquatic-terrestrial interface ecosystems are excellent systems to study the interactions among invasive ecosystem engineers, physical features, and biological communities, because interactions among vegetation, sediment, and fluids within biophysical feedbacks create and modify distinct physical features. Further, these systems provide important ecosystem services including coastal protection afforded by their natural features. In this dissertation, I investigate the interactions and feedbacks among sand-binding beach grass species (a native, Elymus mollis (Trin.), and two non-natives, Ammophila arenaria (L.) Link and A. breviligulata Fernald), sediment supply, and dune shape along the U.S. Pacific Northwest coast. Dunes dominated by A. arenaria tend to be taller and narrower compared to the shorter, wider dunes dominated by A. breviligulata. These patterns suggest an ecological control on dune shape, and thus, coastal vulnerability to overtopping waves. I investigate the causes and consequences of these patterns with experiments, field observations, and modeling. Specifically, I investigate the relative roles of vegetation and sediment supply in shaping coastal dunes over inter-annual and multi-decadal time scales (Chapter 2), characterize a biophysical feedback between beach grass species growth habit and sediment supply (Chapter 3), uncover the mechanisms leading to beach grass coexistence and whether A. breviligulata can invade and dominate new sections of coastline (Chapter 4), and examine the non-target effects resulting from management actions that remove Ammophila for the recovery of the threatened Western Snowy plover (Charadrius alexandrinus nivosus) (Chapter 5). I found that vegetation and sediment supply play important roles in dune shape changes across inter-annual and multi-decadal time scales (Chapter 2). I determined that a biophysical feedback between the beach grass growth habits and sediment supply results in species-specific differences in sand capture ability, and thus, is a likely explanation for differences in dune shape (Chapter 3). I found that all three beach grass species can coexist across different sediment deposition rates, and that this coexistence is largely mediated by positive direct and indirect species interactions. I further determined that A. breviligulata is capable of invading and dominating the beach grass community in regions where it is currently absent (Chapter 4). Combined, these findings indicate that A. breviligulata is an inferior dune building species as compared to A. arenaria, and suggest that in combination with sediment supply gradients, these species differences ultimately lead to differences in dune shape. Potential further invasions of A. breviligulata into southern regions of the Pacific Northwest may diminish the coastal protection ability of dunes currently dominated by A. arenaria, but this effect could be moderated by the predicted near co-dominance of A. arenaria in these lower sediment supply conditions. Finally, I found that the techniques used to remove Ammophila for plover recovery have unintended consequences for the native and endemic dune plant communities, and disrupt the natural disturbance regime of shifting sand. A whole-ecosystem restoration focus would be an improvement over the target-species approach, as it would promote the return of the natural disturbance regime, which in turn, would help recover the native biological community. The findings from this dissertation research provide a robust knowledge base that can guide further investigations of biological and physical changes to the coastal dunes, can help improve the management of dune ecosystem services and the restoration of native communities, and can help anticipate the impacts of future beach grass invasions and climate change induced changes to the coast.
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2298. [Article] Nearshore distribution of barnacle and mussel larvae and oceanographic mechanisms of onshore transport and delivery
Recruitment of larvae from the plankton is an important determinant of community structure in marine systems. In populations of many marine species, recruitment determines the basic demographic parameters ...Citation Citation
- Title:
- Nearshore distribution of barnacle and mussel larvae and oceanographic mechanisms of onshore transport and delivery
- Author:
- Tyburczy, Joe
Recruitment of larvae from the plankton is an important determinant of community structure in marine systems. In populations of many marine species, recruitment determines the basic demographic parameters of immigration, emigration, and reproduction. Moreover, the effect of recruitment as an "ecological subsidy" can determine the strength of interactions among species and whether populations are limited by recruitment itself, or by competition or predation. For this reason, understanding the transport of larvae is essential for management and conservation. In Chapter 2, my coauthors and I investigated the vertical and cross-shelf distribution of barnacle and bivalve larvae with a series of paired day/night sampling cruises off the coast of central Chile. Barnacle larvae were generally found close to shore (within 1.5 km), and the cross-shelf distribution of all taxa varied little despite contrasting upwelling conditions. Since current velocities decrease quickly with proximity to shore, larvae distributed in the nearshore are less likely to be dispersed long distances. Further, the consistent cross-shelf distribution of larvae suggests that they are not necessarily swept on- or offshore by upwelling or relaxation. Depth distributions consistent with classical diel vertical migration (DVM; swimming deeper during the day, shallower at night) were found in barnacle nauplii, but not barnacle cyprids or in bivalve larvae. One potential advantage of DVM is that it may limit offshore transport and thereby increase the odds that larvae will reach suitable habitat when they are competent to settle. Another possible benefit of DVM is that it may increase feeding opportunity in shallow water at night when visual predation risk is low, while providing refuge at depth during the day when visual predation in the upper water column is greater. In Chapter 3, my coauthors and I undertook a large-scale study in northern Monterey Bay, CA that integrated high-frequency physical and biological sampling to allow resolution of multiple different potential mechanisms of onshore larval transport and settlement. Depending on location within Monterey Bay, three processes were found to be associated with onshore barnacle settlement: regional upwelling, local diurnal upwelling driven by afternoon sea breezes, and the passage of an upwelling shadow front. Based on these findings we propose a novel conceptual model that encompasses oceanographic processes at multiple scales and reconciles apparent inconsistencies between empirical results and existing theories. In Chaper 4, my coauthors and I developed a simple larval transport model using data on currents, offshore flux of barnacle larvae, and onshore settlement of barnacles from the empirical study in Chapter 3. A parameter set was found that produced model settlement correlated with observed settlement. The fit of modeled and observed settlement was sensitive to model parameters. However, for all parameter sets examined, onshore transport of particles was much greater at depth. This result from the larval transport model is consistent with the conceptual model proposed in Chapter 3. Further, during intervals when onshore transport was observed, model particle trajectories clearly show onshore transport only at depth via two of the mechanisms identified in Chapter 3 (local diurnal upwelling and passage of the upwelling shadow front).
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2299. [Article] Rheological and spectroscopic characterization of surimi under various comminuting and heating conditions
Optimization of comminuting and heating conditions for surimi gel preparation obtained from three fish species: Alaska pollock (AP) (Theragra chalcogramma), Pacific whiting (PW) (Merluccius productus), ...Citation Citation
- Title:
- Rheological and spectroscopic characterization of surimi under various comminuting and heating conditions
- Author:
- Poowakanjana, Samanan
Optimization of comminuting and heating conditions for surimi gel preparation obtained from three fish species: Alaska pollock (AP) (Theragra chalcogramma), Pacific whiting (PW) (Merluccius productus), and threadfin bream (TB) (Nemipterus spp.) was the focus of this study. Three parameters during comminution were separately evaluated: chopping time, chopping temperature, and salting time. Results from fracture gel analysis suggested a strong relation between the fish's environmental habitat and optimal final chopping temperature. Extending chopping time to 15 min under strictly controlled temperature at 0 °C was preferable for cold water fish AP surimi. Even though high chopping temperature (20 °C) for a shorter time (12 min) surprisingly resulted in strong gel texture similar to that of 0 °C for 15 min, high chopping temperature should not be employed for AP surimi. AP could set as a gel at this temperature within a shorter time in a holding tank which could subsequently cause a problem when extruded on the cooking belt. Temperate water fish Pacific whiting, demonstrated its maximum gel strength when chopped at 15-20 °C. The optimum comminution condition for warm water fish threadfin bream surimi was to chop the surimi until the paste temperature reached between 25-30 °C. Prolongation of chopping once the surimi hit its threshold (optimum) temperature diminished the quality of the resulting protein gel. Cooling system connected to the chopping bowl is strongly recommended as it will allow the comminution process to be extended as long as possible until the surimi paste reaches its target temperature. Raman spectroscopy disclosed the different level of protein unfolding based on secondary structure of α-helix and β-sheet during various comminuting conditions. Unfolding of protein was facilitated by increased chopping temperature to a greater degree than extended chopping time. Extending chopping could denature the light meromyosin structure as it could not form a semi gel-like structure at temperatures between 32-40 °C. Protein solubility of surimi paste in salt solution always decreased with prolonged chopping time. The decrease rate accelerated with increased chopping temperature. The formation of disulfide interchange gradually took place during chopping as observed from Raman spectroscopy. Also the surface hydrophobicity increased with extended chopping time. However, gel strength behaved differently according to the various chopping conditions indicating the lack of its relationship between salt soluble protein, disulfide formation, and surface hydrophobicity to gel strength. During extending chopping time, not only more mechanical force is applied to unfold protein structure, but proteins also have longer time to be extracted more by salt. Addition of salt at a different time during chopping process was therefore conducted using threadfin bream surimi due to its higher thermostability. Extending chopping time without salt followed by salt addition at the last step resulted in lower gel texture compared to the conventional chopping protocol where salt is always added at the early stage of comminution. Mechanical chopping could unfold protein structure; however, proteins, rather than staying solubilized, would precipitate and form a randomized structure under the chopping condition without salt. The heating condition greatly affected the gelation and rheological properties of AP surimi. The highest elastic modulus was obtained with the slowest heating rate at 1 °C/min. Increased heating rate did not only shorten the time for proteins to unfold and form a well-organized network, it also interfered with the protein network through the vibration of water molecules as phase angle increased. This suggested that AP surimi gained more viscous properties and failed to form an elastic gel. Adjusting moisture content along with applying various frequencies did not alter the pattern of G' formation when paste was heated at different heating rates. AP surimi favored the slow heating.
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2300. [Article] Science basis for changing forest structure to modify wildfire behavior and severity
Fire, other disturbances, physical setting, weather, and climate shape the structure and function of forests throughout the Western United States. More than 80 years of fire research have shown that physical ...Citation Citation
- Title:
- Science basis for changing forest structure to modify wildfire behavior and severity
- Author:
- Graham, Russell T., McCaffrey, Sarah, Jain, Theresa B.
Fire, other disturbances, physical setting, weather, and climate shape the structure and function of forests throughout the Western United States. More than 80 years of fire research have shown that physical setting, fuels, and weather combine to determine wildfire intensity (the rate at which it consumes fuel) and severity (the effect fire has on vegetation, soils, buildings, watersheds, and so forth). Millions of acres of forestlands (mainly in dry forests dominated by ponderosa pine and/or Douglas-fir) contain a high accumulation of flammable fuels compared to conditions prior to the 20th century. Forests with high stem density and fuel loading combined with extreme fire weather conditions have led to severe and large wildfires (such as those seen in the summers of 2000, 2002, and 2003) that have put a number of important values at risk. Although homes in the path of a wildfire are perhaps the most immediately recognized value, these wildfires also put numerous other human and ecological values at risk, such as power grids, drinking water supplies, firefighter safety, critical habitat, soil productivity, and air quality. For a given set of weather conditions, fire behavior is strongly influenced by stand and fuel structure. Crown fires in the dry forest types represent an increasing challenge for fire management as well as a general threat to the ecology of these forests and the closely associated human values. Crown fires are dependent on the sequence of available fuels starting from the ground surface to the canopy. Limiting crown fire in these forests can be accomplished by actions that manage in concert the surface, ladder, and crown fuels. Reducing crown fire and wildland fire growth across landscapes decreases the chances of developing large wildfires that affect human values adjacent to forested areas. However, a narrow focus on minimizing crown fire potential will not necessarily reduce the damage to homes and ecosystems when fires do occur. Homes are often ignited by embers flying far from the fire front, and by surface fires. Fire effects on ecosystems can also occur during surface fires where surface and understory fuels and deep organic layers are sufficient to generate high temperatures for long periods. Fuel treatments can help produce forest structures and fuel characteristics that then reduce the likelihood that wildfires will cause large, rapid changes in biophysical conditions. Fuel treatments can also help modify fire behavior sufficiently so that some wildfires can be suppressed more easily. Subsequent, sustained fuel treatments can maintain these conditions. Different fuel reduction methods target different components of the fuel bed. Thinning mainly affects standing vegetation, and other types of fuel treatments such as prescribed fire and pile burning woody fuels are needed to modify the combustion environment of surface fuels. In forests that have not experienced fire for many decades, multiple fuel treatments—that is, thinning and surface fuel reduction—may be required to significantly affect crown fire and surface fire hazard. Fuel treatments cannot guarantee benign fire behavior but can reduce the probability that extreme fire behavior will occur. Fuel treatments can be designed to restore forest conditions to a more resilient and resistant condition than now exists in many forests, and subsequent management could maintain these conditions, particularly in dry forests (ponderosa pine and Douglas-fir) where crown fires were historically infrequent. The degree of risk reduction will depend to some degree on the level of investment, social and economic acceptability of treatments, and concurrent consideration of other resource values (for example, wildlife). This report describes the kinds, quality, amount, and gaps of scientific knowledge for making informed decisions on fuel treatments used to modify wildfire behavior and effects in dry forests of the interior Western United States (especially forests dominated by ponderosa pine and Douglas-fir). A review of scientific principles and applications relevant to fuel treatment primarily for the dry forests is provided for the following topics: fuels, fire hazard, fire behavior, fire effects, forest structure, treatment effects and longevity, landscape fuel patterns, and scientific tools useful for management and planning.