Variation In Frequency Of Occurrence Research Articles

Community-level modelling of boreal forest mammal distribution in an oil sands landscape

Anthropogenic landscape disturbances are known to alter, destroy, and fragment habitat, which typically leads to biodiversity loss. The effects of landscape disturbance generally vary among species and depend on the nature of the disturbances, which may interact and result in synergistic effects. Western Canada's oil sands region experiences disturbances from forestry and energy sector activities as well as municipal and transportation infrastructure. The effects of those disturbances on single species have been studied and have been implicated in declines of the boreal woodland caribou (Rangifer tarandus caribou). Yet, the specific responses of the mammal community, and of functional groups such as prey and predators, to those interacting disturbances are still poorly known. We investigated the responses of black bear, grey wolf, coyote, fisher, lynx, red fox, American red squirrel, white-tailed deer, moose, caribou, and snowshoe hare to both natural habitat and disturbance associated with anthropogenic features within Alberta's northeast boreal forest. We used a novel community-level modelling framework on three years of camera-trap data collected in an oil sands landscape. This framework allowed us to identify the natural and anthropogenic features which explained the most variation in occurrence frequency among functional groups, as well as compare responses to linear and non-linear anthropogenic disturbance. Occurrence frequency by predators was better explained by anthropogenic features than by natural habitat. Both linear and non-linear anthropogenic features helped explain occurrence frequency by prey and predators, although the effects differed in magnitude and spatial scale. To better conserve boreal biodiversity, management actions should extend beyond a focus on caribou and wolves and aim to restore habitat across a diversity of anthropogenic disturbances and monitor the dynamics of the entire mammal community.

Body-size spectra of biofilm-dwelling protozoa and their seasonal shift in coastal ecosystems

Community-based assessment of protozoa is usually performed at a taxon-dependent resolution. As an inherent ‘taxon-free’ trait, however, body-size spectrum has proved to be a highly informative indicator to summarize the functional structure of a community in both community research and monitoring programs in aquatic ecosystems. To demonstrate the relationships between the taxon-free resolution of protozoan communities and water conditions, the body-size spectra of biofilm-dwelling protozoa and their seasonal shift and environmental drivers were explored based on an annual dataset collected monthly from coastal waters of the Yellow Sea, northern China. Body sizes were calculated in equivalent spherical diameter (ESD). Among a total of 8 body-size ranks, S2 (19–27μm), S3 (28–36μm), S4 (37–50μm) and S5 (53–71μm) were the top four levels in frequency of occurrence, while rank S1 (13–17μm), S2 and S4 were the dominant levels in abundance. These dominants showed a clear seasonal succession: S2/S4 (spring)→S2/S4 (summer)→S4 (autumn)→S2 (winter) in frequency of occurrence; S1 (spring)→S4 (summer)→S2 (autumn)→S1 (winter) in abundance. Bootstrapped average analysis showed a clear seasonal shift in body-size spectra of the protozoa during a 1-year cycle, and the best-matching analysis demonstrated that the temporal variations in frequency of occurrence and abundance were significantly correlated with water temperature, pH, dissolved oxygen (DO), alone or in combination with chemical oxygen demand (COD) and nutrients. Thus, the body-size spectra of biofilm-dwelling protozoa were seasonally shaped and might be used as a time and cost efficient bioindicator of water quality in marine ecosystems.

Diurnal variation in occurrence frequency of summertime localized intense rainfall in the Tokyo metropolitan area

Diurnal variation in occurrence frequency of summertime localized intense rainfall in the Tokyo metropolitan area

Nectar yeasts in Delphinium nuttallianum (Ranunculaceae) and their effects on nectar quality

Abstract Microorganisms colonize the nectar of many angiosperms. Variable diversity and spatio-temporal dynamics of nectar-inhabiting microorganisms (e.g., yeasts) may drive variation in nectar sugar composition and subsequent plant–pollinator interactions. We assessed yeast frequency of occurrence and density in the nectar of the perennial herb, Delphinium nuttallianum , across multiple spatio-temporal scales, including flower lifetime and sex-phase transition, flowering season, populations, and years. We tested the hypothesis that pollinators vector yeasts by comparing densities between virgin flowers and those open to visitation. Finally, we identified yeasts using molecular methods and tested for an association between yeast density and nectar composition using ultra-performance liquid chromatography. Yeasts were frequent colonists of Delphinium nectar, occurring in all populations and years sampled. Yeast frequency of occurrence and density varied across most spatio-temporal scales examined. Pollinators were vectors of yeast: virgin flowers remained yeast-free, while those open to visitation became inoculated. Nectar samples were species-poor, with a majority colonized by Metschnikowia reukaufii . Finally, increasing yeast density was correlated with a decrease in sucrose and an increase in monosaccharides. Our results document that yeasts form species-poor communities in populations of this hermaphroditic perennial, in addition to highlighting their spatio-temporal dynamics and effects on nectar quality. Spatio-temporal variation in frequency of occurrence, density, and changes in nectar may have important implications for the nature and strength of interactions between Delphinium and its pollinators.

English

For the occurrence and diversity of insect associated fungi in agroecological habitats of Hot Arid Zone of Punjab, Pakistan soil samples were collected. Insect associated fungi were classified as entomopathogens, opportunistic pathogens and secondary colonizers isolated from the Galleria mellonella bait insect exposed to the soil samples in question. Total 20 number of soil samples collected from Muzzafargarh and Layyah districts belonging to different localities of zone were examined. The frequencies of these species were different in both districts. Total frequency of occurrence of these fungi was the highest in District Muzaffargarh that was found to be 18.18% among all types of observed fungal species in comparison with that of 17.20% in District Layyah. Six species of opportunistic fungi in Hot Arid Zone were found including; Fusarium oxysporum, Fusarium solani, Fusarium sp., Penicillium sp., Aspergillus flavus and Mucor sp. with different frequencies in each district. Total frequency of occurrence of these fungal species was the highest in District Muzaffargarh that was found to be 60.60% among all types of observed species in comparison with that of 41.16% in District Layyah. Six species of secondary colonizers with variation in frequency of occurrence were found in Layyah and Muzaffargarh districts of hot arid zone. The species observed were including; Chaetomium globosum, yeast, Trichoderma sp., Trichoderma koningii Rhizopus oryzae, and Absidia glauca. The highest frequency of occurrence of these fungal species was eminent in District Layyah with the rate of 41.06% among all types of observed species in comparison with that of 21.21% in District Muzaffargarh.   Key words: Entomopathogens, opportunistic pathogens, secondary colonizers and Galleria mellonella bait.

Phenology of an agarophyte Gracilaria birdiae Plastino and E.C. Oliveira (Gracilariales, Rhodophyta) in Northeastern Brazil

The reproductive phenology and thallus length of Gracilaria birdiae were studied over a period of 12 months in a natural bed in Northeastern Brazil. Fertile specimens of G. birdiae were observed during the entire study period. Tetrasporophytes were the most common with an annual mean of 80.1±5.6%, followed by cystocarpic plants (9.3±3.4%), male gametophytes (8.3±3.6%) and infertile plants (2.2±3.4%). Only male gametophytes and infertile plants showed a variation in occurrence frequency during the year (p<0.05). With respect to thallus length, a distinct seasonal variation was observed for all reproductive stages (p<0.05), with the highest values recorded during the rainy season (March to August) and the lowest in the dry season (September to February). The results demonstrate that the size of individuals in this population is significantly affected by the periodic changes in the environment caused by rainfall regimes and hydrodynamism.

Ecotaxonmic baseline evaluation of the plant species in a seasonally flooded forest land proposed for a Rivgas refinery project in Ase-Ndoni, Rivers State, Nigeria

The survey of the flora composition of an ecosystem is important in several environmental baseline studies. An ecotaxonomic assessment was carried out in Ase-Ndoni proposed Rivgas Refinery project site in other to find out the plant species of medicinal and other economic values. The investigation was carried out to establish a baseline data for imminent environmental vicissitudes and envisaged ecological vagaries as could be the case with the Rivgas Refinery Project. A simple random sampling based on standard procedure for ecological assessment was employed in this study. Results of the enumeration show seasonal variation in species frequency of occurrence. A total of 41 and 24 representative species of medicinal and other economic plants were recorded in the wet and in the dry seasons. These reflect a rich flora diversity of ethnobotanical values in the project site. Hence the envisaged event of uncontrolled and accidental hydrocarbon and effluent discharge, a preconceived knowledge of the vegetation could be helpful in the determination of the long and short term effects of such ecological problem. KEYWORDS : Environment, project area, vegetation sampling, species abundance, and medicinal / economic species.

Statistics of Antarctic surface meteorology based on hourly data in 1957–2007 at Syowa Station

Statistical characteristics of the surface meteorology are examined at Syowa Station (69°00′S, 39°35′E), which is located on an island near the coastal region of the Antarctic continent, based on operational observations made over the 50-year period from February 1957 through January 2007, which includes missing periods equivalent to 5 years. Statistics are obtained for the surface temperature, sea level pressure (SLP), and horizontal winds in terms of frequency distribution, frequency power spectra, seasonal variation, diurnal variation, inter-annual variation, and trends, using hourly observation data, and several interesting characteristics are elucidated. The mean temperature, SLP, and wind speed over the 50-year period are −10.5 °C, 986 hPa, and 6.6 m s −1, respectively. The frequency distribution of temperature is far from the normal one, because less variation exists in summer at higher temperatures. The predominant wind direction is northeasterly (southwestward), and a weak secondary peak is observed in the southerly (northward) direction in the frequency distribution. The directional constancy of winds is 0.78. The frequency spectra over a wide range of 2 h to 20 years exhibit clearly isolated peaks corresponding to annual and diurnal frequencies and their higher harmonics. An important finding is that the spectral shape is proportional to a power of the frequency with a transition frequency for all physical parameters. The transition frequencies correspond to about 5 days for temperature and winds and 3 days for SLP, most likely due to cyclonic activity. A peak in the 11-year solar cycle is not identified in any spectrum. Another interesting feature is the dominance of semi-annual and semi-diurnal variations in SLP, while annual and diurnal variations are dominant for temperature and winds. Statistically significant trends are not detected for annual mean surface temperature and SLP over the 50-year period, while a positive trend is significant for wind speed. These trends are also examined as a function of the months. The inter-annual variation of SLP is well correlated with that of the Antarctic Oscillation index, indicating that Syowa Station can be regarded as a typical Antarctic station. Furthermore, statistical analysis was conducted for blizzards (severe snow storms), in terms of duration, and seasonal and inter-annual variation in frequency of occurrence. It is shown that the blizzards are dominant in the period from late March to late October. No systematic variation in blizzard frequency was observed during the 50-year period. Instead, the frequency depends largely on the year with a minimum of nine in 1988 and a maximum of 42 in 1982. As a typical example, a synoptic chart is used to show the cause of a strong snow storm on 27 May 1996, when the absolute maximum gust was observed.

Prevalence of major foliar and panicle diseases of Sorghum (Sorghum bicolor [L.] Moench) in the Deccan plateau of India

Extensive on-farm disease surveys were conducted from August 1999 until March 2001 in four sorghum-growing states of the Indian Deccan plateau. A total of 965 fields were surveyed covering 228 fields in Andhra Pradesh (AP), 406 in Karnataka (KAR), 290 in Maharashtra (MH) and 41 in Tamil Nadu (TN). Among 14 foliar diseases observed, maize stripe virus (MStV), a tenuivirus transmitted by the delphacid plant hopper (Peregrinus maidis), and among five panicle diseases, ergot or sugary disease (Claviceps sorghi and C. africana) were the most destructive diseases. MStV was prevalent in 28.4% and ergot in 13.4% of the fields surveyed in two years across four states. Yet, the mean incidence of MStV in AP was 6% with 85% mean severity. The values in KAR were 12% incidence and 83% severity, in MH 5% and 67%, and in TN 12% and 76%, respectively. The mean incidence of ergot in AP was 34% with 67% mean severity. The values in KAR were 41% and 79%, in MH, 30% and 67%, and in TN 100% and 100%, respectively. Variation in frequency of occurrence of MStV was observed between 1999 and 2001. Variations in frequency could be due to weather factors, vector survival, cropping pattern, and host specificity. The frequency of ergot also was varying among years, locations, seasons and cultivars. An ergot epidemic was observed during the 1999 rainy season in Maachinenipalli village (16°35′N; 78°3′E), Andhra Pradesh. In September 2000, the disease had spread to 13 neighboring administrative zones damaging about 130,000 ha. This paper elucidates the distribution of diseases observed between 1999 and 2001 but does not imply that the diseases are restricted necessarily to a particular zone or location.

No evidence of general decline in an amphibian community of Southern France

We investigated long term changes in an amphibian community in the Languedoc area of Southern France by comparing results of a survey of 56 ponds made in the early 1970s with results of a survey of the same localities in 2001. Based on the frequency of new occurrences and disappearances of species in the sample ponds, there is no sign of a general decline of amphibians in this area. Most species showed non-significant variation in frequency of occurrence or had increased. “Green frogs” ( Rana perezi/ ridibunda/ kl. grafi) showed clear signs of decline, but this is a local phenomenon rather than a decline at the regional scale. Pelodytes punctatus probably declined also, possibly due to its sensitivity to fish introduction. The species richness in the ponds has also remained stable except in ponds where fish have been introduced. The only adverse impact of human activities that we could detect was thus the introduction of fish, which had a significantly adverse effect on amphibian species richness.

Quasi 2-day oscillation of the ionosphere: A statistical study

Abstract A large database of hourly ionosonde measurements, encompassing more than 20 stations during 1957–1991, is examined for evidence of the quasi-two-day (QTD) oscillation. A QTD (frequencies between 0.50±0.08 day−1) oscillation in ƒ o F 2 at the 95% confidence level is found to exist with the following characteristics: 1. 1. Amplitude variations primarily in the range ±0.4–1.0 MHz; 2. 2. Occurrence frequency (i.e. in a given month, at a given station, the percentage of years in which a QTD event was detected) maximizing at about 30–60% during local summer in both hemispheres; 3. 3. At mid-latidues, zonal structure corresponding either to westward propagation with zonal wavenumber s = 1, or a stationary oscillation with indeterminable zonal wavenumber; at lower latitudes (ca. 20°) a much broader spectrum of wavenumbes (s = −2 to s = +4) is evident; 4. 4. No variation in occurrence frequency with solar cycle. At the same confidence level a QTD oscillation in hmF2 occurs much less frequently than ƒ o F 2 , with typical amplitudes of order ±8–16 km.

DRUG‐INDUCED AKATHISIA REVISITED

SUMMARY Despite the fact that the neuroleptic drugs have been widely used for more than 40 years, one of their most common side‐effects, akathisia, has been relatively neglected. There are still no universally agreed diagnostic criteria for akathisia, particularly chronic akathisia, and in this review article, we discuss the controversies surrounding the voluntary nature of its motor features and the importance of the dysphoric component. We also review the published epidemiological studies to show the great variation in frequency of occurrence. Finally, we discuss the possible neurotransmitters involved in the pathophysiology and treatment of this condition.

Episodes of surface westerly winds as observed from islands in the western tropical Pacific

We describe the characteristics of surface westerly wind episodes in the tropical Pacific between mid‐1957 and 1980, as they can be determined from a collection of daily average wind records from islands. Several types of frequency of occurrence and duration statistics are presented; events in which the maximum westerly anomalies exceed 7 m s−1 are not common, but are prominent in the records. There is strong seasonal and geographical variation in frequency of occurrence. Four types of westerly episodes are found; we call them types N, C, S, or FS, according to whether the maximum westerly wind is found north of, centered on, south of, or “far south” of the equator near the international date line. Sixteen, 45, 47, and 47 events of type N, C, S, and FS are identified, respectively. The strongest westerly winds are associated with type C and S events; maximum daily average values can exceed 20 m s−1. Only type C and S events are found to have substantial equatorial zonal wind anomalies. Several examples of type C and S events are presented. Composite events of each type have been computed, and their characteristics are described. In order to explore relationships between equatorial westerly events and cyclones, all of the named tropical cyclones within a region encompassing the near‐date line islands have been identified; various statistics are presented, but no absolute relationships have been identified. The similarity between the composite type C and S anomaly patterns and patterns of the El Niño‐Southern Oscillation monthly mean zonal wind anomaly previously documented in the literature is striking; evidently, the westerly events often dominate in the monthly average anomaly.

The occurrence and characteristics of electron beams over the polar regions

Data from the Lockheed experiment on the polar‐orbiting satellite S3‐3 have been used to study the morphology and some of the characteristics of narrow, field‐aligned electron beams. The beams were found to occur very commonly in a circumpolar zone corresponding to that of the statistical auroral oval. Upflowing, downflowing, and counterstreaming beams were found throughout the altitude range examined (3000–8000 km), but the variation of occurrence frequency with altitude depended on beam direction and indicated that the source region of the beams was commonly at or above 1 RE. The beams are characterized by a very narrow pitch angle distribution with a median half width at half maximum of 6° and by very soft energy spectra, and they were not usually detectable at energies above 400 eV. In contrast, their peak fluxes extended over a wide range, sometimes exceeding 1011 (cm² sr s keV)−1, although more usually they were less than 3×109 (cm² sr s keV)−1. Upflowing ions, especially ion conics, were commonly found in close association with the electron beams. It appears likely that several of the main features of the beams can be accounted for by a source model of a region of short‐lived multiple double layers.

A lunar effect in the occurrence of conjugate echoes on topside sounder ionograms

Radio waves, transmitted by the Alouette 2 and Isis 1 satellites, can become trapped in magnetic field aligned ionization ducts, which can extend between the northern and southern hemispheres of the earth. In a set of data containing 1.8 × 105 ionograms recorded at five low-latitude telemetry stations from December 1965 to November 1971, conjugate echoes were observed on 4.5% of the ionograms. The frequency of occurrence of these echoes has a lunar semimonthly oscillation about the 4.5% average with an amplitude of (0.63 ± 0.13)% and with maximums at lunar ages of 4.9 and 16.9 hours (6 and 21 days after new moon). This oscillation occurs in independent blocks of data at very nearly the same lunar ages. The effect appears to depend on longitude, since it is found to be strongest in the data recorded at the American telemetry stations, intermediate at the African and Hawaiian stations, and weakest at the Asian and Australian stations. This effect is strongest for data recorded at the Quito telemetry station, where for data recorded between December 1965 and December 1966 a lunar semimonthly oscillation of amplitude (3.0 ± 0.2)% was found in the percentage occurrence of conjugate echoes. This semimonthly variation probably indicates that lunar tidal induced electric fields in the dynamo region have some influence in the production or duration of conjugate ducts; it is surprising, however, that no lunar diurnal or semidiurnal variation in occurrence frequency of conjugate ducts was found.