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Chemical abundances in main-sequence stars in open cluster M67van den Brink, Nemo January 2011 (has links)
The discovery of a solar twin in the open star cluster M67 (Önehag et al. 2011) implies a near-solar chemical composition for the cluster. This study uses high-resolution spectroscopic data of five main-sequence stars in M67 to analyze their abundance of a few key elements and compare results to the solar-twin composition and the composition of field twins (Melendez et al. 2009). The derived composition was also compared to predictions of stellar-structure models including the effects of element diffusion. (Richard, private communication). It is found that all analyzed elements are, to varying degree, less abundant in the five main sequence stars than in the solar twin. With the possible exception of iron, all derived abundances also fall clearly below the diffusion predictions.
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Patterns of fish and macro-invertebrate distribution in the upper Laguna Madre: bag seines 1985-2004Larimer, Amy Beth 15 May 2009 (has links)
The Laguna Madre is a hypersaline lagoon. Despite harsh conditions, the upper
Laguna Madre (ULM) is a highly productive ecosystem and a popular sportfishing area,
especially for spotted seatrout and red drum. It is also the most important Texas bay for
commercial fishing of black drum. TPWD’s Coastal Fisheries division began
conducting routine monitoring of coastal fishery resources in 1977 to guide
management. The goal of the present study was to improve understanding of spatiotemporal
trends in relative abundance of selected fish and macro-invertebrate species in
the upper Laguna Madre. I used TPWD’s bag-seine and water-quality data from the
years 1985-2004 to examine variation in species’ relative abundances and relationships
to several environmental factors. I hypothesized that one or more of these variables,
alone or in combination, were related to spatial and temporal trends in community
composition. I used detrended correspondence analysis (DCA) to measure species
turnover (beta diversity) and to determine which model (linear or unimodal) of species
response along a gradient to apply. I used canonical correspondence analysis to relate
species abundances directly to explanatory variables. The explanatory variables were tested for significance and the variance partitioned among three groupings: temporal,
spatial and environmental.
DCA indicated complete species turnover along two dimensions: seasonal and
spatial. It also indicated that a unimodal method such as CCA was appropriate for
further analysis. The CCA model included 39 variables. The included variables
explained 14% of the variation in species abundance in the data set. Since the first four
axes explained 67% of the variation contained in the first two DCA axes, the chosen
explanatory variables were sufficient to explain the majority of the tractable variation in
species abundance. The variance partitioning procedure indicated that temporal effects
were the most important in explaining species variation in the Upper Laguna, followed
by the spatial component. The pure environmental component explained the least
amount of variation.
In this study, much of the variability in species abundance was due to the
spawning patterns of estuary-dependent species, most of which spawn in the spring and
summer months, leading to higher abundances from spring through fall.
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The Texas Quail Index: Evaluating Predictors of Quail Abundance Using Citizen ScienceReyna, Kelly Shane 15 May 2009 (has links)
Annual abundance of northern bobwhite (Colinus virginianus) and scaled quail
(Callipepla squamata) fluctuates drastically in Texas, which complicates a quail
manager’s ability to forecast quail abundance for the ensuing hunting season. The Texas
Quail Index (TQI) was a 5-year citizen-science project that evaluated several indices of
quail abundance and habitat parameters as predictors of quail abundance during the
ensuing fall. I found that spring cock-call counts explained 41% of the variation in fall
covey-call counts for all study sites in year 1–4, and 89% of the variation in year 5.
Further investigation revealed that year 5 was a drought year and had a significantly
lower percentage of juveniles in the hunter’s bag. These results suggest that during
drought years, fall quail abundance is more predictable than during non-drought years
and that low breeding success may be the reason. If these data are correct, quail
managers should have a better ability to predict the declines of their fall quail abundance
in the dry years.
The TQI relied on citizen scientists (cooperators) to collect data. Since most
(66.1%) cooperators dropped out of the program, and <8% of all data sets were complete, I surveyed the cooperators by mail to determine the rate and cause of
cooperator decline and to identify characteristics of a reliable cooperator (i.e., one that
did not drop out of the study). I found that cooperator participation declined earlier each
year for year 1–4, and that year 5 demonstrated a steady trend with the least amount of
cooperators. Most respondents who dropped out (61.5%) reported their motive for
leaving was that it was too time consuming. I found no difference in mean cooperator
demographics, satisfaction, or landownership goals between those respondents who
dropped out and those that did not. However, 38% of those who dropped out were not
completely satisfied with communication from TQI coordinators compared to only 15%
of those who did not drop out, indicating that communication, or perhaps overall
volunteer management, might have been improved. Future studies should maintain
better communication with participants, require less time, and provide an incentive for
retention.
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Canopy Characteristics Affecting Avian Reproductive Success: The Golden-cheeked WarblerKlassen, Jessica Anne 2011 May 1900 (has links)
Habitat disturbances play a major role in wildlife distribution. Disturbances such as loss of breeding habitat and fragmentation are of particular concern for Neotropical migrant songbird populations. Additionally, different avian species respond differently to the surrounding environment at different spatial scales. Thus, multi-scale studies on bird abundance and reproductive success is necessary for evaluating the effects of habitat alterations. The golden-cheeked warbler (Dendroica chrysoparia) is a Neotropical migrant songbird that breeds exclusively in central Texas. In 1990, the U.S. Fish and Wildlife Service listed the golden-cheeked warbler as endangered, providing habitat loss among the list of justifications. Habitat requirements for this species are known to include mature juniper-oak (Juniperus-Quercus) woodlands; however, relationships between habitat characteristics and golden-cheeked warbler reproductive success remain unclear. Whereas the majority of golden-cheeked warbler research has focused on areas in the center of the breeding range, little is known about interactions between warblers and the environment at the edge of the range. Therefore, it is important to understand these relationships for successful golden-cheeked warbler management.
I investigated relationships between golden-cheeked warbler reproductive success and habitat characteristics, including canopy closure and tree species composition, at the study site and territory scale. My study took place within Kickapoo Cavern State Park and surrounding private properties in Kinney and Edwards counties in the southwest corner of the golden-cheeked warbler breeding range. I derived habitat characteristics from satellite imagery from the US Geological Survey National Land Cover Dataset (NLCD) and from field sampling. The NLCD provided data on canopy closure and tree species composition at a 30 m resolution. Additionally, I used spherical densitometers and transect evaluations to ground-truth data and take more detailed measurements. I determined reproductive success by nest monitoring and the Vickery index when nests could not be found. I monitored 80 territories across six study sites in 2009 and 2010. Reproductive success was 39.5 percent in 2009 and 59.4 percent in 2010. I found statistically significant results at the study site scale, whereas golden-cheeked warbler abundance increased as the portion of woodland increased. Similarly, I found that golden-cheeked warbler reproductive success increased at the study site scale as canopy closure increased. I did not find correlations between reproductive success and canopy closure or tree species composition at the territory scale. Results suggest that golden-cheeked warblers utilize a wider variety of habitat composition than previously thought, and habitat composition as a whole may not be the driving factors influencing warbler reproductive success in this region.
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An atomic physics viewpoint of stellar abundance analysisSobeck, Jennifer S. 04 May 2015 (has links)
Element abundance trends with overall metallicity contain vital clues to the formation and evolution of the Galaxy. Abundances may be used to elucidate nucleosynthesis mechanisms and to ascertain rates of Galactic enrichment. To obtain accurate abundances, several crucial inputs such as high-quality spectroscopic observations, rigorous calculations of line transfer, and precise atomic data (e.g. transition probabilities) are necessary. The current work endeavors to improve abundance values for key elements with a four-fold approach: accumulation of hundreds of high-resolution stellar spectra in order to commence a systematic and thorough Manganese abundance derivation in cluster and halo field stars; re-determination of the neutral chromium oscillator strengths and application of this data to stellar abundance analyses; modification of a radiative line transfer code in order to yield accurate abundances from evolved stars; and semi-empirical derivation of transition probabilities to allow for the utilization of spectral features in the red visible and infrared wavelength ranges for abundance determinations. The first comprehensive investigation of manganese in globular clusters is done in this work. A subsolar Mn abundance trend for both halo globular cluster and field stars is found. The analysis shows that for the metallicity range -0.7>(Fe/H)>-2.7 stars of 19 globular clusters have a a mean relative abundance of <(Mn/Fe)>= -0.37±0.01 (σ=0.10), a value in agreement with that of the field stars: <(Mn/Fe)>= -0.36± 0.01 (σ=0.08). Remarkably, the <(Mn/Fe)> ratio remains constant in both stellar populations over a 2 orders of magnitude span in metallicity. Next, the present study employed branching fraction measurements from Fourier transform spectra in conjunction with published radiative lifetimes to determine transition probabilities for 263 lines of neutral chromium. These laboratory values are used to derive a new photospheric abundance for the Sun: log [element of](Cr I)⊙= 5.64±0.01 (σ=0:07). In addition, oscillator strengths for singly-ionized chromium recently reported by the FERRUM Project are employed to determine: log [element of](Cr II)⊙ = 5.77±0.03 (σ= 0.13). No indications of departures from LTE are found in the neutral chromium abundances. The current work then takes advantage of the fact that transition metals exhibit relatively pure LS coupling and employs standard formulae to yield semi-empirical oscillator strengths. These data were then compared to experimental gf values in order to assess accuracy. Finally, this study undertakes a new abundance investigation of the RGB and RHB stars of the M15 globular cluster. A detailed examination of the both the metallicity and n capture elements is performed. This work appears to confirm that star-to-star abundance variations do occur among the M15 giants (which was initially observed by Sneden et al. 1997, 2000). / text
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Powerful fish in poor environments: Energetic trade-offs drive distribution and abundance in an extremophile forest-dwelling fishWhite, Richard Stuart Alan January 2013 (has links)
For many species, distribution and abundance is driven by a trade-off between abiotic and
biotic stress tolerance (i.e. physical stress versus competition or predation stress). This trade-
off may be caused by metabolic rate differences in species such that slow metabolic rates
increase abiotic tolerance but decrease biotic tolerance. I investigated how metabolic rate
differences were responsible for an abiotic-biotic tolerance trade-off in brown mudfish
(Neochanna apoda) and banded kokopu (Galaxias fasciatus), that drives the allopatric
distribution of these fish in podocarp swamp-forest pools. Brown mudfish and banded
kokopu distribution across 65 forest pools in Saltwater forest, Westland National Park, New
Zealand was almost completely allopatric. Mudfish were restricted to pools with extreme
abiotic stress including hypoxia, acidity and droughts because of kokopu predation in benign
pools. This meant the mudfish realised niche was only a small fraction of their large
fundamental niche, which was the largest out of sixteen freshwater fish species surveyed in
South Island West Coast habitats. Thus mudfish had a large fundamental to realised niche
ratio because of strong physiological stress tolerance but poor biotic stress tolerance
compared to other fish. A low metabolic capacity in mudfish compared to kokopu in terms of
resting and maximum metabolic rates and aerobic scope explained the strong mudfish
tolerance to extreme abiotic stress, but also their sensitivity to biotic stress by more powerful
kokopu in benign pools, and hence their allopatric distribution with kokopu. Despite being
restricted to extreme physical stress, mudfish populations were, in fact, more dense than those
of kokopu, because of low individual mudfish resting metabolic rates, which would cause
resources to be divided over more individuals. Distribution and abundance in mudfish and
kokopu were therefore driven by an abiotic-biotic tolerance trade-off caused by a
physiological trade-off between having slow or fast metabolic rates, respectively. The negative relationship between species resting metabolic rates and their tolerance to abiotic
stress provides a way of estimating the impact of human induced environmental change that
can either increase or decrease habitat harshness. Thus species with low metabolic rates, like
mudfish, will be negatively affected by human induced environmental change that removes
abiotic habitat stress and replaces it with benign conditions. My evidence shows that extreme
stressors provide a protective habitat supporting high mudfish biomass with significant
conservation value that should be maintained for the long-term persistence of mudfish
populations.
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Effects of local environmental factors and spatial habitat characteristics on the density of a marine gastropod, Megastraea undosa (Wood 1828)Abshire, Courtney Burke 20 December 2010 (has links)
The ability to identify and define factors which affect the abundance of marine species has been a primary goal of many ecologists. The need to accurately quantify the relationship between an organism and its environment is of critical importance in cases where that organism is the object of commercial harvest and tied to the economic well being of communities. This is especially evident for communities located along the Pacific coast of the Baja California peninsula where local fishing cooperative and their associated communities are dependent on the continuing successful harvest of a limited number of marine species, one of these being the marine gastropod Megastraea undosa (Wood, 1828). I conducted a multi-scale observational study investigating the effects of scale and selected local environmental and regional habitat characteristics of subtidal rocky reefs on the density of M. undosa. The study showed that M. undosa density varied significantly at two scales: quadrat (m2) and reef (100s m2). At the reef level, area and percent total cover were found to have a significant positive relationship with M. undosa density. No measured variable showed a significant association to M. undosa density at the quadrat level. Results suggest that both local and regional factors combine to affect M. undosa density and that their impacts on M. undosa density warrants further study. / text
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Sezónní rozdíly ve využívání terestrických biotopů u vážek / Is there any seasonal differences in terrestrial habitat use in dragonflies?Hronková, Jana January 2016 (has links)
Dragonflies (Odonata) passing through several life stages during their life cycle. During metamorphosis between stages, they did not change only morphology, but also habitat preferences. Although they are associated to aquatic environment during larval stage, adults are much more mobile and can utilize the surrounding terrestrial habitats. Adult dragonflies are also involved in to terrestrial food chains. However the relationship, between the quality of terrestrial habitats and the diversity of dragonflies as well as seasonal changes in utilization of these habitats are still not known. This thesis aiming to analyze the influence of seasonality and distance from aquatic habitat on the abundance of dragonflies. Moreover, the differences in fish farming intensity were considered in the analyses. Fieldwork took place during 2015 from May to September. Data from 29 localities of Czech Republic were included. It is not surprising that I found significant influence of seasonality, on the abundance of all species, as well as a negative relationship between dragonfly abundance and distance from water reservoir. Interestingly, it was found, that dragonfly utilization of terrestrial areas around the extensively managed habitats was significantly higher than in habitats around intensively managed ponds. These findings demonstrate the importance of terrestrial habitats for dragonflies, especially those occurring around extensively managed water habitats.
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Abundance včelstev v krajině a úživnost katastru / Abundance of honeybeeBrandejsová, Jana January 2016 (has links)
Determining place thesis Abundance of bee colonies in the country and the carrying capacity of the land register. Establishing a Connection in Úvaly near Prague with three beekeepers. For these three beekeepers were required to determine reserves of pollen with three visits in the period of May, June and July. Each measurement was carried out always at the three strongest hives. Proven reserves of pollen was performed using photographs of each honeycomb in the hive. After calculating reserves of pollen, to assess the value of honey to the surrounding plants. The conclusion was to determine whether a load for the site Úvaly near Prague is present or not enough bees and suggest possible solutions.
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Estrutura da comunidade de trepadeiras de dois fragmentos de florestas estacional semidecidual em diferentes estágios de conservaçãoRobatino, Angélica [UNESP] 29 April 2010 (has links) (PDF)
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robatino_a_me_botib.pdf: 576227 bytes, checksum: 70cf90c0b67d5855f8f2066708c509f7 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Plantas trepadeiras são componentes característicos das florestas tropicais e contribuem significativamente com a diversidade taxonômica. Além disso, desempenham papel estrutural e ecológico essencial para a manutenção dessas florestas. Áreas perturbadas podem ser locais ideais para a proliferação excessiva de trepadeiras, prejudicando os processos de regeneração natural. O objetivo geral deste estudo foi a caracterização florística e estrutural de comunidades de trepadeiras inseridas em dois fragmentos de floresta estacional semidecidual, sendo um com indicadores de perturbação (município de União Paulista, SP) e o outro considerado conservado (município de Matão, SP). Por meio do método de parcelas, em 1 ha, foram amostradas 3278 trepadeiras. Os 1101 indivíduos identificados no fragmento de Matão foram distribuídos em 19 famílias, 43 gêneros e 65 espécies; as famílias mais ricas em espécies foram Bignoniaceae (17), Sapindaceae (10 ), Malpighiaceae (9) e Apocynaceae (7). Os 1544 indivíduos identificados do fragmento de União Paulista distribuíram-se em 15 famílias, 38 gêneros e 66 espécies; as famílias mais ricas foram Bignoniaceae (25), Malpighiaceae (10), Fabaceae (7), Apocynaceae (6) e Sapindaceae (6). Em Matão houve maior proporção de trepadeiras preênseis (63,9%) em relação a trepadeiras volúveis (27,9%) e escandentes (8,2%). Já em União Paulista foi verificada proporção similar de indivíduos preênseis (47,8%) e volúveis (48,6%), com menor proporção de trepadeiras escandentes (3,6%). A espécie com maior IVI em Matão foi Melloa quadrivalvis, sendo H’=3,11 nats.ind-¹ e J’=0,75. Em União Paulista, Serjania lethalis apresentou maior IVI, sendo o H’= 3,09 nats.ind-¹ e J’= 0,74. A similaridade de Jaccard foi de 36%, enquanto que de Bray-Curtis foi de 32%. As características constatadas para o fragmento de Matão, como... / Climbing plants are characteristic components of the tropical forest and significantly contribute to the taxonomic diversity. Besides, participate in the structural and ecological role essential for the maintenance of those forests. Disturbed areas can be ideal places for the excessive proliferation of vines, harming the processes of natural regeneration. The aim study was the characterization of structural and floristic communities climbers inserted in two fragments of semideciduous forest, one disturbed (placed in União Paulista, SP) and one undisturbed (placed in Matão, SP). In 100 plots (1ha), were sampled 3278 climbers. The 1101 individuals identified from the Matão fragment were distributed in 19 families, 43 genera and 65 species; the richest families were Bignoniaceae (17), Sapindaceae (10), Malpighiaceae (9) e Apocynaceae (7). The 1544 individuals identified from the União Paulista fragment were distributed into 15 families, 38 genera and 66 species, the richest families were Bignoniaceae (25), Malpighiaceae (10), Fabaceae (7), Apocynaceae (6) e Sapindaceae (6). There were more tendril climbers (63.9%), than stem twiners (27.9%) and branch twiners (8.2%). Whereas, in União Paulista was verified a similar proportion of individuals tendril climbers (47.8%), and stem twiners (48.6%), with a smaller proportion of branch twiners (3.6%). Melloa quadrivalvis presented the highest IVI in Matão, were H’=3.11 and J’=0.75. In União Paulista, Serjania lethalis had the highest IVI, H’= 3.09 and J’= 0.74. The Jaccard’s similarity was 36%, while Bray-Curtis’s similarity was 32%. The characteristics observed in Matão fragment, like total abundance, proportional balance between climbers and trees abundance, significant amount of individuals with diameter >10 cm, besides the larger total basal area despite the smaller abundance, compared with the disturbed fragment; they... (Complete abstract click electronic access below)
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