170 research outputs found
Letter from [author unknown] to John Muir, 1884 Apr 2
No full textDr. George Engelmann Born at Frankfurt on the Main, February 2nd, 1809 DIED, In the midst of his scientific labors at his more in St. Louis, on Monday, February 4th, 1884, in the seventy-fifth year of his age 3003 Locust Street, St. Louis March 10th, 1884https://scholarlycommons.pacific.edu/jmcl/44166/thumbnail.jp
The effects of climate on Engelmann spruce regeneration and vigor
No full text2017 Fall.Includes bibliographical references.Recent climate modeling suggests that drought will become more frequent in the southern Rocky Mountains over the next century. Understanding how tree species will respond and adapt to this changing climate is vital to guide future management decisions by land managers. Future increases in drought frequency and severity will likely have an impact on the composition of forests. Modeling studies have been used to predict the effect that increasing drought will have on Engelmann spruce in southwest Colorado, but little field data has been gathered to validate this modeling. This study uses empirical data to test whether drought conditions are related to decreases in seedling establishment and tree vigor. Annual regeneration data from 1990 to 2009 was collected from 24 sites with 30-year PRISM precipitation normals ranging from 531 mm to 924 mm to determine if dry and wet sites respond differently to drought. Elevations of our study sites ranged from 3100 m to 3500 m above sea level. Among these 24 sites, we found the number of seedlings per hectare varied between 1804 and 18975. We used a mixed effects model to identify climate variables important to annual seedling establishment density. A separate provenance study on the White River National Forest was analyzed to identify drought effects on tree vigor. Engelmann spruce bareroot seedlings from twenty sources ranging from British Columbia to New Mexico were planted in 1970 at an elevation of 2930 m north of Vail, Colorado. Annual precipitation normals of the 20 seed sources ranged from 423 – 1918 mm. We collected increment cores from six to eight trees from each of the 20 seed sources in 2016, and standardized the chronology of each tree using standard dendrochronological techniques. We then analyzed the annual radial growth response of each provenance to a period of severe drought from 2000-2004 using both RWI and a resistance/resilience framework. For both parts of our study, we found weather variability and drought did not impact regeneration or vigor as much as hypothesized, suggesting regeneration and vigor of spruce in these high elevation forests are not reduced by contemporary levels of drought
Impacts of coarse woody debris and edge effects on Engelmann spruce regeneration
No full text2016 Summer.Includes bibliographical references.Engelmann spruce (Picea engelmannii Parry ex Engelm.) is a notoriously difficult species to regenerate, and there has been a history of regeneration failures following group selection cuts on the Uncompahgre Plateau. Our goal was to investigate edge effects and coarse woody debris management on regeneration success in group selection openings. Group selection is an uneven-aged system used in the West to regenerate high elevation spruce-fir forests with small (<1 ac) openings. We implemented an Engelmann spruce germination study on the Uncompahgre Plateau in group selection openings. Permanent plots were installed in spring of 2015. We altered microsite conditions by manipulating coarse woody debris amounts at varying distances from the north and south edges in combination with scarification. Findings show that the southern edge provides a benefit to spruce germination through 23 meters. Coarse woody debris was significantly beneficial at all distances from edge, and without coarse woody debris germination was extremely low
Predatory and energetic relations of woodpeckers to the Engelmann spruce beetle
No full textIncludes bibliographical references.June, 1967.A general theory of the population dynamics of predator-prey systems was developed from a survey of pertinent literature. According to the theory, populations of simplified predator-prey systems fluctuate wildly and periodically. Complicating factors dampen the amplitude of the population fluctuations and thus exert a stabilizing influence on the systems. The predator-prey system between the Northern Three-toed, Hairy and Downy Woodpeckers, and the Engelmann spruce beetle was chosen for an investigation of the population dynamics of a natural predator-prey system. The population densities of several species of bark beetles attracted to trees killed and damaged by a fire on the study area in Northern Colorado, increased to levels that attracted the feeding attention of the woodpeckers. The numerical response of the woodpeckers to prey density was graded, that of the Northern Three-toed Woodpecker was the most pronounced and that of the Downy Woodpecker was the least pronounced. Spatial and temporal differences were noted in the foraging behavior of the three species of woodpeckers; similar but less apparent differences were also noted in the foraging behavior between the sexes of the Northern Three-toed and Hairy Woodpeckers. Both the interspecific and intersexual differences in foraging behavior were correlated with morphological and dietary differences. The metabolic demands of free-living woodpeckers were estimated by feeding diets of known caloric content to active woodpeckers in cages at several different ambient temperatures. Estimates were also made of the caloric content of Engelmann spruce beetle larvae and the rate at which they are digested by the woodpeckers. Combining these estimates with the estimates of the relative densities of woodpeckers, and the average number of spruce beetle larvae found per woodpecker stomach made it possible to calculate the number of larvae consumed by each species of woodpecker. This method gave results very similar to the usual method whereby the number of larvae surviving in bark protected from woodpeckers is compared with the number surviving in bark exposed to woodpeckers. Every aspect of the predator-prey system between woodpeckers and the Engelmann spruce beetle, except the number of larvae destroyed, conforms to general theory. The number of prey destroyed in this predator-prey system is higher than that known for any other system between vertebrate predators and invertebrate prey
Engelmann spruce and subalpine fir stand dynamics in north central Colorado
No full text2015 Spring.Includes bibliographical references.Stemwood biomass and production were measured in a 600-year chronosequence of stands consisting of Engelmann spruce and subalpine fir in the Colorado Front Range. The stands were part of a chronosequence established and measured in 1984. The original chronosequence showed near-constant biomass of spruce after approximately 250 years of development. Spruce production also had remained nearly constant after an initial rise and fall during the first 250 years. Fir biomass decreased more than that of spruce after around 150 years. Fir biomass remained at lower consistent sub-dominate values through the end of the chronosequence. Fir's high production from early stand development decreased and remained constant after approximately 175 years of development. Changes over the most recent 29 years did not follow the patterns in the 1984 chronosequence: spruce biomass dropped by 70% with little change in fir biomass. This resulted in a 47% average decrease in total stand biomass since 1984. Stand biomass showed no relationship with stand age. Spruce beetle-kill appeared to have played a major role in live biomass decline in all stands. Net increment was negative in fir as increases in fir production were more than offset by fir mortality. The stands investigated have developed from post-fire initiation and, although there was no evidence of subsequent major disturbance in 1984, severe beetle infestation since then has altered expected trends in spruce-fir forest structure. Stand age pattern projections will likely continue to be altered by disturbances and changing disturbance regimes
Letter from [author unknown] to John Muir, 1884 Apr 2
No full textDr. George Engelmann Born at Frankfurt on the Main, February 2nd, 1809 DIED, In the midst of his scientific labors at his more in St. Louis, on Monday, February 4th, 1884, in the seventy-fifth year of his age 3003 Locust Street, St. Louis March 10th, 188
Author:
No full textThis thesis presents a new approach to the reconstruction of dental panoramic x-ray images with experimental results. The reduction of the x-ray dose that offers higher safety for the patient reduces diagnostic image quality. Inverse filtering often fails due to insufficient knowledge about the noise, which varies depending on the location. In order to overcome the aforementioned obstacles, the method proposed in this thesis firstly develops a semi-empirical scatter-glare model of the photon projection process and applies it to the auto computation of an appropriate noise-estimate. Secondly, the energy of the noise-estimate is then subtracted from that of the diagnostic image in the different resolution levels of a Multiresolution Decomposition. Experiments show that the method outperforms state-of-the-art denoising in terms of better modulation transfer function and signal to noise ratio.
Time-since-death and its effect on wood from beetle-killed Engelmann spruce in southwest Colorado
No full text2016 Fall.Includes bibliographical references.Spruce beetles (Dendroctonus rufipennis) have caused extensive mortality on 1.5 million acres in Colorado during the current epidemic. There is considerable interest in harvesting treatments aimed at removing dead trees for reasons of fire risk, watershed health, and human dimensions. The byproducts from these treatments can either be viewed as a difficult and costly disposal problem or an opportunity for the recovery of forest products. However, a major barrier to the latter option is the lack of knowledge about how the material changes with time standing dead. Ten plots were selected on the Rio Grande National Forest (RGNF), from which 86 Engelmann spruce (Picea engelmannii) trees were felled and sampled. Tree rings were analyzed to determine Time-Since-Death (TSD) on all study trees. TSD and other variables such as diameter, elevation, and bark retention were used to develop models predicting the deterioration rate from beetle mortality (seasoning check, heart rot, and sap rot). In a separate mill study, eleven trees from the RGNF were milled to dimensional lumber to determine the lumber tally, prevalence of blue stain, and lumber grade breakdown. Checking was found to be most strongly correlated with tree diameter, and the effect of TSD was most pronounced at larger diameters. Higher elevations and increased bark retention served to reduce or slow checking. Sap rot was found to increase with TSD, but heart rot was not. Many study trees had moisture contents suitable for the development of rot. In the mill study, older dead trees produced a lower percentage of select structural lumber than control trees. Net Scribner was a poor predictor of lumber tally; gross Scribner and product potential cubic were more accurate. Results from this study may help land managers maximize sawtimber recovery by prioritizing treatment areas. Information such as tree diameter, TSD, and elevation will allow foresters to better differentiate stands that have already been subject to severe deterioration from those that will in short order
Beyond the Bosphorus? Comparing German, French, and British Discourses on Turkey's Application to Join the European Union. IHS Political Science Series Paper, No. 111, December 2006
No full textThis article examines the impact of national borders on public discourses, based on a case study of the struggle surrounding Turkey’s application to join the European Union (EU). Comparing opinions, reasons and interpretation patterns in press commentaries about enlarging the EU beyond the Bosphorus, the findings confirm the paramount importance and robustness of national cleavages between the German and the French public sphere on the one hand, and the British on the other. Whereas Turkish membership was predominantly re-jected on the continent, the British commentators strongly and almost unanimously sup-ported Ankara’s request to open doors. These similarities and divergences, I argue, are first and foremost the result of, and linked with, competing visions of Europe’s finality, especially regarding various constitutional ideas and cultural principles. Against this background, the Turkey question was partly exploited as an instrument supporting or repressing different conceptions of the European Union’s future
- …
