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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.