Spatial Patterns Of Occurrence Research Articles

Early life history of a seahorse, Hippocampus mohnikei , in Tokyo Bay, Japan

The early morphological development, seasonal and spatial occurrence patterns, and food habits of a seahorse, Hippocampus mohnikei, in offshore waters of Tokyo Bay, central Japan, were studied on the basis of 206 juvenile and young specimens (6.0–65.3 mm TL) collected between August 1995 and January 1999. All the specimens were collected within the period from May to January, inclusive, each year. In the least developed specimen (6.0 mm TL), the number of dorsal, anal, and pectoral fin rays had attained the adult complement, whereas the minute caudal fin, consisting of two rays, was present in juveniles of 6.0–26.4 mm TL. Hippocampus mohnikei≧35 mm TL, being larger than settlement size (ca. 30 mm TL), had very low gut fullness index values (GFI = 0, >70% of specimens), whereas those of 15–29 mm TL had higher values (GFI = 2–4, >80% of specimens). In addition, larger individuals selectively fed on larger planktonic animals (species of Brachyura), which occurred naturally at low densities, although smaller food items, such as Oithona davisae and Penilia avirostris, occurred abundantly, being consumed by smaller H. mohnikei individuals (15–34 mm TL). These results indicated that food availability for H. mohnikei in offshore waters of Tokyo Bay is significant for individuals larger than settlement size, because their food preference would shift from smaller food items to larger food items, which would be scarce in their environments.

Dispersal, Recruitment and Site Occupancy of Grassland Plants in Fragmented Habitats

We examined adhesive seed dispersal, recruitment and site occupancy of 17 plant species characteristic of semi-natural grasslands. The main objectives were to examine different aspects of dispersal: the potential distance of seed transport: the likelihood of recruitment at putative suitable sites along road verges: the spatial (realised) patterns of occurrence along road verges (occupancy): and associations among these aspects and seed size. Adhesive dispersal capacity was investigated experimentally using cattle. Recruitment was investigated by seed sowing experiments. Occupancy was recorded in two regional surveys. Results suggested that adhesive dispersal may be an effective mode of seed transport, even for species which lack special adhesive' structures, such as hooks or hairs. Fifteen of the 17 species successfully recruited at the experimental gaps and adjacent grassy areas. Disturbance promoted seedling recruitment. Seedling emergence was negatively associated with adhesive dispersal capacity. Spatial (occupancy) patterns were not related to recruitment features or dispersal capacity. There is some support for a trade-off between adhesive dispersal capacity and recruitment ability, but no support for a trade-off between adhesive dispersal capacity and ability to withstand competition during recruitment. The results are discussed in the context of species distribution and persistence in fragmented landscapes. We suggest that adhesive dispersal has been underestimated as a mechanism of seed transport, but that adhesive dispersal capacity per se is not the main factor determining species occupancies in fragmented grasslands.

Variation in the diet of Cassin's auklet reveals spatial, seasonal, and decadal occurrence patterns of euphausiids off California, USA

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 137:1-10 (1996) - doi:10.3354/meps137001 Variation in the diet of Cassin's auklet reveals spatial, seasonal, and decadal occurrence patterns of euphausiids off California, USA Ainley DG, Spear LB, Allen SG We investigated spatial and temporal variation in the diet of a planktivore, the Cassin's auklet Ptychoramphus aleuticus, in the Gulf of the Farallones, California, USA, where its population has decreased ca 50% in size coincident with the general decline of zooplankton in the California Current. Stomach samples were collected and compared among birds foraging at sea during the non-upwelling, post-spring transition (to upwelling), and upwelling periods each year from 1985 to 1988. Upwelling-period samples also were compared with samples regurgitated to chicks on the Farallon Islands during that period; such samples had been collected during 1971 and 1977-1991. During the non-upwelling period, auklets fed on the small, energetically inferior, oceanic euphausiid Euphausia pacifica, but following the spring transition, the auklets switched to small, juvenile fish (mostly Sebastes spp.) until these had grown too large for capture. Thereafter, the auklets switched to the larger and energetically more valuable euphausiid Thysanoessa spinifera, which had become available upon the onset of upwelling. This general pattern was repeated each year, although some between-year variability among ancillary prey was evident. Auklet foraging locality, however, varied only slightly throughout the year; auklets were most dispersed during El Niño. It was apparent that the availability of T.spinifera was linked to upwelling. The decrease in the prevalence of T.spinifera in the diet fed to chicks from 1971 to 1991 is consistent with decreased intensity of upwelling in the region, as is the reduction in numbers of auklets in the region over the same period. Our results indicate the value of studies of easily accessible marine predators, which can temporally and spatially integrate patterns in the prevalence of prey species, thereby increasing our understanding of the important processes that structure food webs. California Current . Cassin's auklet . Diet . Euphausia pacifica . Euphausiid . Interannual variability . Thysanoessa spinifera . Upwelling Full text in pdf format NextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 137. Publication date: June 27, 1996 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1996 Inter-Research.

Deriving Incident Management Measures Using Incident Probability Models and Simulation

Incidents cause a large part of congestion and subsequent costs. Incident management is aimed at preventing the occurrence of incidents as well as minimizing the impact of incidents that occur. Two elements of incident management are addressed: the modeling of the incident occurrence probability for freeway sections and the modeling of the logistics of incident removal by various emergency services (tow trucks, ambulances, etc.). Models are presented that relate incident probabilities to road and traffic variables such as number of lanes, type of section (e.g., weaving sections), and traffic volumes and composition. These models give insight into the factors determining incident frequencies and may be used to design incident prevention measures. The results indicate that, for example, the splitting up of weaving sections into a series of joins and forks may be a very effective way to reduce the number of incidents. Traffic characteristics and the number of lanes also play important roles. These incident probability models can be used to generate the input for a logistics model. Such a model is presented. It was developed to test the effectiveness of various procedures aimed at minimizing incident duration. Examples of such procedures are the optimal location of emergency and recovery vehicles, given the spatial pattern of incident occurrence; optimal assignment of such vehicles to incidents; and various strategies for going from the vehicle's station to the incident site. These strategies include the permission to use the shoulder lane for emergency services. Experiments with the models for a heavily trafficked part of the Dutch freeway network indicate that a combination of such strategies can reduce incident congestion costs by nearly one-half.

Seasonal Activity of Meloe americanus (Coleoptera: Meloidae) in a Mississippi Old-field Habitat

Adults and triugulin larvae of Meloe americanus Leach were collected by pitfall trapping and sweepnetting of foliage during 14 consecutive months at an old-field site in Washington Co., MS. Adults were captured in pitfalls from December to April, and triungulins were captured in pitfalls and attached to Apoidae (Hymenoptera) hosts on foliage only from April to May and from September through October. Several scenarios are proposed to explain this unusual pattern of disjunct triungulin seasonal occurrence. Spatial patterns of adult and triungulin occurrence are correlated with successional changes in the habitat, and attachment sites of triungulin larvae on Apoidae hosts are documented.

OnWhy Abortion Rates Vary: A Geographical Examination of the Supply of and Demand for Abortion Services in the United States in 1988, by Patricia Gober

A lIthough there has been a sub-specialty of geography known as medical geography for many years, its practitioners have tended to shy away from the more controversial socio-political issues concerning health care, and rarely publish their work in the major geography, public health, or medical journals. Studies involving perinatal health conducted by geographers are also quite rare, irrespective of the venue in which they appear. It was therefore with great anticipation that I awaited the publication of Patricia Gober's article Why Abortion Rates Vary: A Geographical Examination of the Supply of and Demand for Abortion Services in the United States in 1988 (Gober 1994). Having now read this paper, I feel compelled to offer some comments by way of linkage with researchers in the fields of biometry, perinatal epidemiology, demography, spatial statistics, and related fields who might share some or all of my concerns. There is much of value in Gober's paper, and herein lies the predicament for the casual audience. An understanding of the historical context within which abortion services have been sought, provided, legislated, regulated, and moralized is a prerequisite to the careful study of geographic factors in the supply of and demand for these services. Gober provides a workmanlike overview, chronicling the history of the preand post-Roe v. Wade eras. There are two significant omissions from this discussion. First, information on trends in maternal and reproductive mortality associated with these procedures before and after the landmark Supreme Court decision should be added (Cates 1984; Forrest and Henshaw 1993). Second, data on how changes in state laws affect abortion rates are available; this information might help the reader to understand the spatial patterns described and analyzed later in the paper (Korenbrot et al. 1990). If one overlooks the comments concerning reliability and validity of data sources below, the discussion of spatial patterns of occurrence and residence-based abortion rates is also a useful contribution which deserves a wider audience. Gober is also to be commended for her courage in addressing one of the most highly charged topics on the contemporary American scene. I agree with Gober that, from the perspective of the geographer, l[o]ur mission ... is to identify the geographic variations in abortion rates, to seek their causes, and to predict their change under a variety of potential scenarios (Gober 1994:248). Where I differ is in my ability to accept the spatial and statistical analyses presented in this paper as a useful first step in this process. There are significant problems with the data sources, construction of dependent variables, selection of independent variables, and choice of statistical methods for the ecological analysis which collectively render the conclusions of Gober's study highly problematic.

Playas and Lunettes on the Southern High Plains: Morphometric and Spatial Relationships

Abstract The pre-European impact of natural and human disturbance on the forests of the southeastern piedmont is poorly understood, particularly since nearly all forests were cleared from this region during the colonial period. To uncover the character of historical disturbance processes in the piedmont, this study examines the environmental controls of presettlement species distribution through the analysis of land-survey records from central Georgia. Ordination of witness trees by detrended canonical correspondence analysis in conjunction with interpretation of spatial patterns of species occurrence suggest that topography and soil texture had important direct influences on forest composition. Beyond such direct effects, however, these environmental factors better reflect a fuel moisture gradient as a primary control of species' distribution in the landscape. Pine, the most abundant taxon in the survey records (27 percent), occurred primarily on dry uplands that were prone to frequent burning. Fire-tole...

Tropical Cyclones in the Southwest Pacific: Spatial Patterns and Relationships to Southern Oscillation and Sea Surface Temperature

An analysis of a 20-yr dataset of tropical cyclones in the southwest Pacific has been made to determine the spatial patterns of cyclone occurrence and how these depend on the Southern Oscillation (SO) and sea surface temperature. A local measure of cyclone incidence is defined as the number of cyclones that enter into a 2° lat-long square during some period (eg., within one season) and this quantity is mapped for four Southern Oscillation index (SOI) categories. The maps show that the geographical distribution of cyclone incidence shifts eastward and northward during negative SOI phases and vice versa. The mean annual incidence for the whole region is 28% higher than average for our strongly negative SO category and 16% below average for our near-zero category. To explore the roles of the SO and local SST, correlation analysis was applied to mean values of cyclone incidence for four subregions of 20° longitude width between 10° and 22°S. Markedly different SOI/SST responses were found on either side of 170°E. In the Coral Sea subregion (150°–170°E), seasons with a relatively high tropical cyclone incidence were preceded by significant positive anomalies in SST and weak positive anomalies of the SOI. The behaviors of the three eastern subregions (lying between 170°E and 130°W) were similar to each other, but were very different to that of the Coral Sea subregion. Their seasons of higher cyclone incidence were preceded by significant negative anomalies of SOI and Tahiti pressure, which continued into the cyclone season, but with only weak or nil SST relationships. Analysis of variance was used to determine the relative contributions of the main variables for each subregion. Altogether, SOI/SST variables before the cyclone season can explain from 20% to 50% of the variance for the individual subregions. Concurrent variables can explain 70% of the variance for the three eastern subregions taken as a single unit. On the basis of these statistical results, the authors proposed that the primary influence on tropical cyclone incidence west of 170°E is the local oceanic conditions, as represented by SST, while to the east of 170°E it is the eastward extent of favorable atmospheric conditions, as indicated by the SOI or Tahiti pressure. The results have application to seasonal cyclone forecasting and natural hazard assessment and mitigation activities within the region.

Statistical study of ULF wave occurrence in the dayside magnetosphere

Ultralow‐frequency (ULF) waves are observed almost everywhere in the dayside magnetosphere. The mechanism by which these waves are generated and transformed in the dayside magnetosphere is still not understood. Here we report a statistical study of these waves based on magnetic field data from the ISEE 1 spacecraft. Data from the first traversal of the spacecraft through the entire dayside magnetosphere have been examined to determine the spatial distribution of wave occurrence. Successive 20‐min segments of data were transformed to a field‐aligned coordinate system. The parallel component was detrended and all three components of the field spectrally analyzed. Wave occurrence was defined by the presence of significant peaks in the power spectra. Wave events were categorized by three wave frequency bands: Pc 3 with T∼10‐45 s; Pc 4 with T∼45‐150 s; the short‐period part of the Pc 5 wave band with T∼150‐324 s. Properties of the spectral peaks were then entered into a data base. The data base was next sorted to determine the spatial occurrence pattern for the waves. Our results show that Pc 3 waves most frequently occur just outside synchronous orbit and are approximately centered on local noon. Pc 4 waves have a similar distribution with its peak further out. Pc 5 waves have high occurrence rate at the two flanks of the magnetosphere. Peaks in spectra obtained near the magnetopause are less clearly defined than those deeper in the magnetosphere.

Types of ionospheric scintillations in southern mid-latitudes during the last sunspot maximum

A 5-yr study (1987–1992) has been undertaken at a southern mid-latitude station, Brisbane (35.6°S invariant latitude) on scintillation occurrences in radio-satellite transmission (at a frequency of 150 MHz) from polar orbit Transit satellites, within a sub-ionospheric invariant latitude range 20–55°S. Over 7000 recorded passes were used to define the spatial and temporal occurrence pattern of different types of scintillation events. Two predominant scintillation types were found: so-called type P (associated with a scintillation patch close to the magnetic zenith) and type S (characteristic of the equatorward edge of auroral scintillation oval). Type S was by far the most frequent during sunspot maximum (1988–1992), with sharp occurrence peaks in the summer-autumn period. Its seasonal occurrence showed a high degree of correlation (correlation coefficient r = 0.8) with the seasonally averaged 10.7 cm solar radio flux. This type occurred mainly at night-time except in austral summer where 40% of scintillations were detected in daytime, coinciding with the well-known summer peak of sporadic- E occurrence. Type P was more predominant during a year (1987) of ascending sunspot activity but decreased to a much lower level during the sunspot maximum.

Distribution patterns of Tetrapygus niger (Echinodermata: Echinoidea) off the central Chilean coast

We investigated spatial distnbution and temporal occurrence patterns of Tetrapygus niger in the subtidal zone off the central Chilean coast from March to November 1990. The shallowest portion of the subtidal zone and the shallowest edge of the kelp forest of Lessonia trabeculata appeared to be important recruitment zones for this species We found a s~gnificant number of recruits along the bed border, and a marked decrease of u rchn abundance toward the center of the kelp Data obtained in September and November outside the kelp bed showed juvenile urchins [i.e. <24 mm test diameter (TD)] strongly associated with crevices. Size-frequency distributions at 2 m depth for those months also showed a large trough of intermediate-sized individuals (i.e. 15 to 30 mm TD). Temporal analysls of size-frequency distributions of individuals collected outs~de the kelp showed a relatively slow shift of modes between March and September and a malor modal shift from September to November. Density values of urchins found in November were relatively low; however, the individuals appeared aggregated.

Persistent Patterns of Thunderstorm Activity in the Central United States

Abstract Observations of thunderstorm events by mouth for the period 1948–77 at 106 stations in the central United States are used to examine persistent spatial patterns in thunderstorm occurrence. A principal components analysis reveals that nearly 55% of the variance is explained by the first four components. An oblique rotation was performed using the first four components, with distinct synoptic-scale patterns revealed. The synoptic environments of four months representative of the four rotated components arc briefly described. A regionalization is presented that was developed by assigning each grid point to the rotated component on which it has the highest loading.

The role of water ice clouds in the Martian hydrologic cycle

A one‐dimensional model for the seasonal cycle of water on Mars has been used to investigate the direction of the net annual transport of water on the planet and to study the possible role of water ice clouds, which are included as an independent phase in addition to ground ice and water vapor, in the cycle. The calculated seasonal and spatial patterns of occurrence of water ice clouds are qualitatively similar to the observed polar hoods, suggesting that these polar clouds are, in fact, an important component of the water cycle. A residual dry ice cap in the south acts as a cold trap which, in the absence of sources other than the caps, will ultimately attract the water ice from the north cap; however, in the presence of a source of water in northern mid‐latitudes during spring, it is possible that the observed distribution of vapor and ice can be in a steady state even if a residual CO2 cap is a permanent feature of the system.

Twentieth-century climate change, fire suppression, and forest production and decomposition in northwestern Minnesota

Long-term fire, climate, and vegetation data were used together with simulation models to estimate the effects of 20th century climate change and fire suppression on fire regime and organic-matter accumulation in mixed-conifer stands of Itasca State Park, northwestern Minnesota. Spatial and temporal patterns of fire occurrence and forest composition over the last 150 years determined by stratigraphic charcoal, fire-scar, tree-ring, and pollen analyses in separate studies provide evidence for vegetation and fire relationships. Water balances constructed from temperature and precipitation data collected since 1840 were used to model fire probability and intensity of burn before fire suppression which began in 1910. Existing patterns of biomass accumulation in forest-floor, herb, shrub, and tree components were compared with fire history and topographic variability to provide a spatial perspective on fire effects. Simulation models used these relationships to estimate (i) how accumulation of organic matter had changed through the past under the different fire regimes that prevailed on different topographic aspects, (ii) the changes brought about by fire suppression in 1910, and (iii) the fire regimes and their effects that would have prevailed since fire suppression with the warm–dry climate of the 20th century. Humus, litter, shrubs, and herb cover were less abundant and more variable spatially and temporally before fire suppression. Spatial variability in forest-floor organic matter, which resulted from different fire frequencies in different vegetation and topographic settings before fire suppression, was largely gone by 1920 as a result of fire suppression. Had fire suppression not been instituted in 1910, fire frequency would have increased by 20–40% in the 20th century because of warmer and drier conditions. Forest-floor oganic matter would have been largely depleted by frequent and severe fires exposing mineral soils, particularly during the drought years of the 1930s. Herb biomass would have increased, shrubs would have been more variable, and tree seedling establishment would have been substantially altered. Time required for buildup of fuels limits the extent to which increased moisture deficits increase fire frequency.

Inferences on the inheritance of congenital anomalies from temporal and spatial patterns of occurrence.

Most congenital anomalies are believed to result from interactions between genetic and environmental determinants, whose relative importance is not generally established. Temporal and spatial patterns allow inferences on the underlying transmission processes; in particular, it is possible to discriminate between sporadic and nonsporadic genetic factors, and to find evidence for the effects of environmental heterogeneity in time and space. We studied the occurrence of 14 anomalies in 14 registries of Western Europe. Four basic patterns have been identified: (1) Chromosomal abnormalities have uniform incidences and do not show significant geographical variation, in agreement with the expected consequences of randomly scattered nondisjunction events. (2) The homogeneous spatial distributions of three severe malformations (renal agenesis, oesophageal atresia, ano-rectal atresia) are consistent with both the effects of fresh mutation and segregation of detrimental alleles. (3) A decrease of similarity of incidences with distance has been observed for neural tube defects, and this is the expected consequence of isolation by distance on genetically determined traits. (4) For facial clefts, polydactyly, and hypospadias, all postulated processes poorly account for the observed temporal and spatial patterns.

Testing the consistency for mapping urban vegetation with high-altitude aerial photographs and landsat MSS data

Two methods of analysis were evaluated for mapping urban vegetation on high-altitude, color-infrared aerial photographs and Landsat MSS data of Syracuse, NY. The first method consisted of defining the spatial patterns (strata) of urban vegetation occurrence. The second method discriminated woody and herbaceous vegetation classes within defined strata. Emphasis was placed on evaluating the consistency of each method. Results indicate that consistent spatial patterns of urban vegetation strata were not achieved on either of the two data types tested due to the spatial complexity of the urban vegetation. However, for discriminating woody and herbaceous vegetation classes within defined strata, good consistency was noted among the interpreters of the high-altitude aerial photographs. The coarse spatial resolution of the Landsat MSS data resulted in low precision for identifying these two vegetation classes in this highly urbanized area. Where photointerpretation efforts are intended for mapping vegetation within numerous urban areas, the estimation of proportions of vegetation classes within defined strata should be a data analysis procedure more objective and consistently repeatable than is the delineation of vegetation patterns.

Spring and summer macroinvertebrate drift in the Lower Mississippi River, Louisiana

Macroinvertebrate drift was sampled dielly each month at three stations across the lower Mississippi River, Louisiana. At least 134 taxa were identified from seven phyla. Total drift catches varied with respect to month, time of day, and station. Relative abundance was greatest in June and August, moderate in July, and lowest in April and May. Dipterans, ephemeropterans and trichopterans numerically dominated the catches and each tended to have its zenith in July, August and June respectively. Important non-insect groups were hydroids, oligochaetes, pelecypods and amphipods and with the exception of pelecypods, were most abundant in April. The presence of certain apparent ‘exotic’ oligochaetes suggested that at least some elements of the drift may be derived from rather remote areas — perhaps even the drainage headwaters. Diel periodicity was most pronounced during the summer months of high total drift densities. Ephemeropterans exhibited strong, nocturnally — oriented diel periodicity, both at the ordinal and lower taxonomic levels, trichopterans and dipterans showed varying tendencies with respect to individual lower taxa. Catches for the dielly-periodic taxa indicated a preponderance of the bigeminus forms. But each major insect order may have had one lower taxon exhibiting the alternans pattern. The stations were decreasingly productive from right-shore to left-shore, while taxonomic richness was greater at midstream and approximately equal along the shores. But spatial patterns of occurrence varied according to months.

Temperature effects in relation to the patterns of distribution and abundance of three species in the Drosophila affinis subgroup

Abstract. 1. The effect of temperature on several aspects of the biology of Drosophila affinis, D.algonquin and D.athabasca were investigated in order to gain insight as to why these closely related species differ in their spatial and temporal patterns of occurrence.2. No differences exist between the three species in the effect of temperature on egg hatchability.3. Productivities of the three species were measured in a temperature gradient device. These measurements indicated that D.athabasca has an advantage in productivity over D.affinis at cooler temperatures (below 25°C). At warmer temperatures (above 25°C) the greater productivity of D.affinis makes it the better species. Drosophila algonquin, like D.athabasca, was characterized by its productivity curve as a species more adapted to cooler climates.4. The competitive abilities of the three species were measured at 25°C, at 18°C, and in an environment which fluctuated between 18 and 25°C on a daily cycle. Competitive ability was estimated on the basis of the performance of the species in two‐ and three‐species populations.5. In general, D.affinis exhibited its highest competitive ability relative to the other two species at the highest experimental temperature. D.athabasca had its highest competitive ability at the lowest temperature. The competitive ability of Ddgonquin was intermediate; less than that of D.affinis but greater than D.athabasca.6. The dependence of competitive ability and productivity on temperature is thought to be partly responsible for the differences between the species with respect to their geographic distributions and their spatial and temporal patterns in natural populations.

Some characteristics of foreshocks and their possible relationship to earthquake prediction and premonitory slip on faults

Foreshocks occur before a large fraction of the world's major (M ≥ 7.0) earthquakes. Teleseismically located events before major earthquakes from 1914 to 1973 were considered together to examine possible average temporal and spatial patterns of foreshock occurrence. Several days before the main shocks and apparently near the epicenters of them (Δ ≲ 30 km) the activity begins to increase, culminating in a final rapid acceleration of activity in the last day. The acceleration continues up to the time of the main shocks, except for a possible temporary decrease about 6 hours before them. The seismicity increases approximately as the inverse of time before main shock. This relationship is essentially unrelated to the magnitude of the main shock. The magnitude of the largest foreshock is also unrelated to the magnitude of the main shock. In addition, pairs of major events are common. Ten percent of the world's major events are preceded by other major events within 100 km and 3 months. For foreshocks within each of three sequences studied, the ratio of the amplitudes of the P and S waves were approximately the same, suggesting that the faulting mechanisms are the same for events in each sequence. By assuming an inhomogeneous fault plane on which asperities fail by static fatigue, we derived an equation for accelerating premonitory slip as a function of time, which agrees with the observed time dependence of foreshocks.

Multi-satellite scintillations, spread- F and sporadic- E over Brisbane—1

Associated amplitude scintillation and vertical-incidence ionosonde data were obtained during a two-year recording period at Brisbane. Scintillations were recorded using radio-satellite transmissions at a frequency of 150 MHz from six U.S. Navy Navigational Satellites (NNSS). It was found that a consistent decrease of scintillations in the morning from 0200 to 0600 LT coincided with an increase in the occurrence and intensity of the frequency spread of spread-F, especially in the southern Winter. A midnight (2200 to 0200 LT) maximum in scintillations coincided with increases of the range spread of spread-F and nocturnal sporadic E( E S), especially in the Summer. A second increase in scintillations was consistently recorded in the afternoon from 1400 to 1800 LT in the Winter, and was associated with a pronounced enhancement in the occurrence and range spread of daytime E S; the occurrence of spread- F was insignificant during this period. The Winter of 1974 was associated with an unusually high occurrence of E S in the afternoon period. Simultaneously, average scintillation index reached its highest level. The diurnal variation in the spatial occurrence pattern of scintillations indicates an equatorwards drift of scintillation patches as the night progresses. Scintillations tended to occur at relatively large zenith angles, especially during the post-midnight hours. The equatorwards drift direction of scintillations is in agreement with the reported movement of ionization patches responsible for spread- F and E S at Brisbane. It appears that the spatial difference in the reflection of ionosonde echoes, associated with the frequency and range spread, is responsible for the varying degree of correlation of scintillations with these two types of spread- F.