bluuebunny/crossref_metadata_2025 huggingface dataset:
Pheidole Megacephala and Iridomyrmex Humilis in Bermuda‐Equilibrium or Slow Replacement?
Authors: Haskins Caryl P. , Haskins Edna F.
Published: May 2006

Ants which actively extent their ranges and displace long—established populations of indigenous species on a world scale are limited to relatively few species. Two of the most striking are Pheidole megacephala and Iridomyrmex humilis. The former expanded its range from its original supposed home in middle Africa during the last century, displacing native species on a vast scale from Australia and Japan to the West Indies and Florida. Beginning somewhat later, Iridomyrmex humilis spread from western South America in a similar fashion and likewise attained a worldwide distribution. Its habitat preferences bring it into direct competition with Pheidole. During the second half of the nineteenth century its is known to have replaced Pheidole in Madeira, where Pheidole itself had earlier replaced the native ant fauna. Nothing is known in detail however, of the pattern of this replacement. Pheidole megacephala is known to have occupied Bermuda by the beginning of the present century, and largely replaced the native ant fauna. In 1957 it was observed by the authors that Iridomyrmex humilis had been introduced into Bermuda. This introduction, paralleling that in Madeira almost a century earlier, offers an excellent opportunity for a detailed analysis of the pattern by which one aggressive species of worldwide distribution may replace or coexist with another equally aggressive in an environment eminently suited to both, and in which there is evidently considerable competition for identical microhabitats. The present paper summarizes the result of two detailed surveys of the distribution of colonies of P. megacephala and I. humilis in Bermuda, made in 1959 and 1963. They evidence a gradual extension of the range of I. humilis at the expense of P. megacephala in a characteristic pattern. It is hoped that other workers will be encouraged to undertake further surveys of this change as it proceeds.
New Stool Shoots From a 20‐Year‐Old Swamp‐Mahogany Eucalyptus Stump
Authors: Wold Myron L. , Lanner Ronald M.
Published: May 2006

A stump of swamp—mahogany eucalyptus (Eucalyptus robusta Sm.) near Hilo, Hawaii, produced sprouts more than 20 years after it was cut. Examination showed that the stump was being kept alive by root grafts from a nearby tree. Production of the stool shoots may have been triggered by storm damage to the nearby tree. This damage may have stopped the flow of growth inhibitors from the crown of the tree of the living stump through the root grafts.
Comparative Nocturnal Thermal Budgets of Large and Small Trees
Authors: Turrell F. M. , Austin S. W.
Published: May 2006

Less freeze injury was observed in unprotected large citrus trees during the freezes of 1962 and 1963 than in small. Earlier observations in the Coachella Valley of southern California prompted this study of the nocturnal heat exchange of a small (3—year—old) and a large (40—year—old) grapefruit tree in two orchards of their respective sized trees. Micro—climate studies were made in these orchards during several winter seasons. Other data for heat transfer calculations have been developed from numerous sources. The heat transfer budget for calm nights showed that leaves were the principal heat exchangers and that shading by neighboring trees reduced their radiation rates to about half in large trees. Stored heat of the ground beneath, and in the woody framework inside the large trees was reflected and reradiated within the leafy crown which had highly insulating properties. The top of the crown of large trees was warmed by the inversion layer.
Ecotypic Differentiation in Prosopis (Mesquite)
Authors: Peacock J. Talmer , McMillan Calvin
Published: May 2006

Laboratory—germinated seedlings of 26 populations, representing three species of Prosopis and obtained from a wide geographic expanse bounded by the Oklahoma—Kansas border to the north and inclusive of continental Mexico to the South, were utilized in experimental ecology during 1961 and 1962. In germination, no population or species character was affected by temperature or light. The ultimate height of seedlings on an experimental, reconstituted soil was substantially greater than for plants on a natural, acid soil from eastern Texas. Ten—, 12—, 14—, and 16—hr photoperiods with some temperature control and 12—, 14—, and 16—hr photoperiods under two temperature regimes resulted in less maximum height and an earlier inception of dormancy in Oklahoma and Texas populations. More southerly populations were less influenced by photoperiod. All populations had significantly greater heights under warm nights (24 degrees C) than under cool nights (13 degrees C) at a day temperature of 30 degrees C. In an experimental garden, a gradient in mean height and date of dormancy inception was recorded, more northern populations having lower maximum height averages and earlier dormancy. Freezing promoted dormancy in the Mexican populations. Spring activity was primarily under the influence of temperature. An ecoclinal response to low temperature, correlated with latitude of origin, showed least frost resistance in Mexican populations. The northern distribution of Prosopis is probably limited by the severity of winter temperatures; the eastern distribution is probably limited by edaphic factors. Ecotypic differentiation over the northern part of its range adds weight to the historical evidence that mesquite has occupied its current distribution for a considerable period of time. Orderly evolutionary developments have undoubtedly resulted in ecological differentiation in diverse habitats and thus have effected the presented distribution of mesquite.
Preliminary Survey of a Possible Molluscan Pest in the Southern United States
Authors: Dundee Dee Saunders , Stutts Baldwin Shields , Hermann Patti Watt
Published: May 2006

A Veronicellid slug, heretofore unknown in the Gulf Coastal region, appeared in late 1960 in both Mobile and New Orleans. Since then it has spread rapidly throughout much of the area. Studies on the distribution, ecology, and behavior are being made.
Analysis of the Reingestion Rhythm in Confined Cottontails
Authors: Heisinger J. F.
Published: May 2006

Reingestion in caged cottontails occurs as a well—synchronized diel rhythm coinciding with or following sunrise. On a reversed lighting regimen rabbits slowly adjust their rhythmic functions so that reingestion is closely fixed to the light time. When they are exposed to sunlight the relationship between the onset of reingestion and sunrise differs during the seasons. As the days become longer reingestion begins later in the morning. This daily and seasonal relationship appears to follow very closely the condition found in unconfined populations. A gastrocolic reflex appears to govern the rate of hard pellet defecation, but another answer apparently must be found to explain the cyclic production of soft feces. The transition from soft feces to hard pellets occurs previous to and is independent of the evening feeding activity. If rabbits are not allowed to feed in the evening a second period of reingestion occurs, at least in some animals.
Mean Separation of Organisms in Three Dimensions
Authors: Gallagher Brent S. , Burdick Jerry E.
Published: May 2006

Equations are derived which give the mean distance between small organisms randomly dispersed in three dimensions. Models based on binomial and Poisson distributions are developed and compared in terms of easily—measured field variables, and a quantitative criterion is given for choosing between them. The results are extended to mixed populations.
Dry‐Matter Production of Mountain Maple and Balsam Fir in Northwestern New Brunswick
Authors: Post L. J.
Published: May 2006

Measurements of dry—matter production in even—aged stands in northwestern New Brunswick show that the annual weight increment of mountain maple is constant while that of balsam fir increases. By age 25 the total production of balsam fir stands is 2.3 times, and the current production is 3.7 times, that of mountain maple.
Ecology of Two Populations of an Aquatic Isopod, Lirceus Fontinalis Raf
Authors: Styron C. E.
Published: May 2006

Two populations of Lirceus fontinalis Rafinesque in DeKalb County, Georgia are isolated in separate river drainages and evolving in response to different environmental stresses. Drought and high temperatures seem the main ecological factors limiting the population on Mount Arabia. These factors are of little moment to the population in Lullwater Creek where biotic factors are of primary ecological significance. Behavioral patterns associated with moisture, flowing water, and temperature fluctuations contribute to the ability of Mount Arabia Lirceus to survive climatic stresses and repopulate solution pits. Behavioral patterns associated with flowing water and light add to the ability of Lullwater Creek Lirceus to maintain their position in the continuously flowing stream and to avoid predators. Although they belong to the same specie morphologically, members of these two populations are not the same species physiologically and ecologically. They differ significantly in their respiratory rates, tolerance to anaerobic conditions, and to a combination of gamma radiation, high temperature, and drought stresses. Members of the two populations are considered to be ecotypes or races of L. fontinalis.
Structure of the New England Herring Gull Population
Authors: Kadlec John A. , Drury William H.
Published: May 2006

Measurements of the rates of population increase, reproduction, and mortality together with an observed age ratio, were used to analyze the population of the Herring Gull in New England. Data from sporadic censuses prior to this study, aerial censuses by the authors, and National Audubon Society Christmas Bird Count indicated that the New England breeding population has been doubling every 12 to 15 years since the early 1900's. This increase has involved founding new colonies and expanding the breeding range There is evidence that 15 to 30% of the adults do not breed in any given year. Sixty—one productivity measurements on 43 islands from 1963 through 1966, involving almost 13,000 nests, showed that from 0.8 to 1.4 young/breeding pair/year is the usual range of rate of production. The age distribution in the population was determined by classifying Herring Gulls by plumage category on an aerial census of the coast from Tampico, Mexico, to Cape Sable, Nova Scotia. Of the 622,000 gulls observed, 68% were adults, 17% were second— and third—year birds, and 15% were first—year birds. Mortality rates derived from band recovery data were too high to be consistent with the observed rate of population growth, productivity, and age structure. Loss of bands increasing to the rate of about 20%/year 5 years after banding eliminates most of the discrepancy. The age structure and rate of population increase indicate a mortality rate of 4 to 9% for gulls 2 years old or older, compared with the 25 to 30% indicated by band recoveries. The population structure we have developed fits everything we have observed about Herring Gull population dynamics, except mortality based on band recoveries.
The Anolis Lizards of Bimini: Resource Partitioning in a Complex Fauna
Authors: Schoener Thomas W.
Published: May 2006

The tiny island of South Bimini contains 4 species of lizards of he genus Anolis, a number surpassed only on the 4 largest islands of the Greater Antilles and on 2 very large and nearby satellite islands. These species are syntopic with respect to a two—dimensional area of the ground but divide the habitat according to perch height and perch diameter: sagrei is partly terrestrial but occurs more often on small and large low perches; distichus prefers the trunks and large branches of medium to large trees; angusticipes inhabits small twigs, especially at great heights; and carolinensis is found mostly on leaves or on the adjacent twigs and brances. The size classes of the species are staggered in such a way that the interspecific classes which overlap most in habitat overlap least in prey size. Similarities in prey size and prey taxa for classes of the same species are somewhat greater than those expected on the basis of habitat and morphology alone. The distribution of the species among the vegetation communities of Bimini can be explained on the basis of perch height and diameter preference. Within the same species, the larger lizards usually eat larger food, fewer items, and in sagrei more fruit; and they have a greater average range of food size per digestive tract. One species (distichus) is extremely myrmecophagous: about 75—90% of its food items are ants. In 3 of the 4 species, subadult males take more food and average smaller prey then females of the same head length. That species (distichus) which takes the smallest food items and whose classes overlap the most in habitat preference with those of other species is least dimorphic is size between the sexes. It is suggested that such small, nondimorphic species are best suited for insinuation into complex faunas, whereas larger, dimorphic forms are best for the colonization of empty areas. The usefulness of various measures of overlap and specialization is evaluated for this lizard association.
An Epizootic of Plague in Gunnison's Prairie Dogs (Cynomys Gunnisoni) in South‐Central Colorado
Authors: Lechleitner R. R. , Kartman L. , Goldenberg M. I. , Hudson B. W.
Published: May 2006

In June 1964 and epizootic of plague began in Gunnison's prairie dogs (Cynomys gunnisoni) in Cochetopa Park, Saguache County, Colordo. Seven colonies of prairie dogs were known in the area at that time. By the end of the summer, 2 of these colonies were exterminated and several others were greatly decimated. A residual phase of the epizootic continued through the summer of 1965 and terminated in 1966 leaving only a few prairie dogs in 2 colonies. No evidence was obtained to indicate that the populations of other mammals living in the area wer adversely affected by plague. The mammalian reservoir of plague in this area remains unknown, but the data suggest that small mammals such as the deer mouse (Peromyscus maniculatus) and the golden—mantled ground squirrel (Citellus lateralis) may be involved. The spread of infection from prairie dog to prairie dog is via flea vectors, especially Opisocrostis tuberculatus, O. labis, and Oropsylla idahoensis. The vector responsible for getting the initial infection into the prairie dogs from some reservoir source is unknown. Apparently, the transfer of Pasteurella pestis from a mammalian reservoir into a population or prairie dogs is an improbable event, and this improbability, rather than any resistance to infection, or resistance to disease, by the prairie dogs is a major factor which allows them to live in such areas of plague enzooticity.
Low Cost, Automatic, Nest and Burrow Monitor Using Radioactive Tagging
Authors: Frigerio Norman A. , Eisler William J.
Published: May 2006

An automatic, transistorized nest and burrow monitor is described which is low in cost, portable, self—contained and weather—proof. Each unit monitors 4 locations to a diameter of 32 m, each animal up to 1 m from its detector. Permanent weekly records are provided for each channel. Gamma rays from a tag on the animal are detected by miniature GM tubes. These are presented as counts on small, electric—pen recorders. While any gamma—emitting radionuclide can be used, certain ones are recommended by reason of their half—lives, gamma energies, and low radiation dose of the animal.
Behavioral Thermoregulation in Butterflies
Authors: Clench Harry K.
Published: May 2006

Behavioral thermoregulation is well studied in reptiles but has not previously been known to exist in butterflies, where it seems to be widespread and perhaps universal. Like reptiles, butterflies are heliotherms, deriving their heat almost exclusively from the sun. For reception of heat they make much use of their wings. Blood circulates in the wings, making them effective heat exchangers whose efficiency is improved by modifications of structure, color and pattern. Behavioral acts (often group—specific) for heat gain include dorsal, lateral and body basking, and ground contact. Behavioral devices for heat loss include shade seeking and probably normal and excessive respiration (evaporative cooling). In optimal air temperatures a series of minor adjustment devices permits normal activity with little concession to temperature control: sum minimizing, irradiation balancing, and wing opening. Five major thermoregulatory behavior patterns can be distinguished: minimal activity, matutinal warming, vesper warming, vernier control and cooling dominant. One or another of these is in operation at all times. Butterflies and reptiles share many behavior devices but moths differ considerably from both. They are myothermus, their major heat source being muscular energy. Heliothermic butterflies and myothermic moths are compared and contrasted with respect to the ecological significance of these specializations, particularly in feeding habits. Some of the many remaining problems are discussed, most important of which is the necessity for obtaining actual body temperatures to amplify the observational data of the present paper.
An examination of Logarithmic Regression as a Measure of Population Density Reponse
Authors: Salt George William
Published: May 2006

Logarithmic regression has been proposed as a measure of density response. The method was tested with data from experimental populations of the protozoan Woodruffia metabolica for which the density response was known. Only the effect of density on reproduction was tested, as there was no mortality. The method does work but is not very sensitive. The total range of values within which negative density response (density dependence) can fall is from 1.00 to 0.73. Further, the method requires fitting a straight line to data which in reality are slightly curvilinear. The ratio of the initial slope to the last slope provides a measure which is about six times as sensitive as logarithmic regression but is more susceptible to error from random variations.
Effect of Past an Prevailing Temperatures on the Carbon Dioxide Exchange Capacities of Some Woody Desert Perennials
Authors: Strain B. R. , Chase Valerie C.
Published: May 2006

The effect of temperature preconditioning on the net photosynthesis and dark respiration of four woody desert perennials (Larrea divaricata, Hymenoclea salsola, Encelia farinosa, and Chilopsis linearis) was analyzed. After the establishment of stem cuttings or field transplants in a greenhouse, the plants were preconditioned at daytime temperatures of 15°, 30°, or 40°C in a growth chamber for 7—17 days. Carbon dioxide exchange capacities wer then determined at various temperatures. There were distinct species differences in response to the preconditioning treatments which could be correlated with differences in distribution and ecology.
Perception of Infrared Radiation from Forest Fires by Melanophila Acuminata de Geer (Buprestidae, Coleoptera)
Authors: Evans William G.
Published: May 2006

When Melanophila acuminata De Geer was stimulated with infrared radiation, responses were obtained in the range of from 2.0 to 6.0@m. The highest sensitivity was found to be, however, in the 2.5 to 4.0@m range at an energy level of 6.0 x 10@o5 watts per cm2. The organs which detect infrared radiation are found on the mesothorax adjacent to the coxal cavities. Through consideration of the physical characteristics of infrared radiation it has been possible to estimate the distances from which forest fires of various sizes could be detected by M. acuminata. For instance, the radiation from a 50 acre fire in mountainous terrain could be detected by this insect from 5 km away but the same size fire on flat land could only be detected from 1 km. The ecological implications of the habits of this insect are also discussed.
Comment on a Report by J. H. Vandermeer and R. H. MacArthur Concerning the Broken Stick Model of Species Abundance
Authors: Pielou E. C.
Published: May 2006

The correct formula is given for the relative abundance of the rth rarest species in MacArthur's overlapping niche model. The correction given by Vandermeer and MacArthur (1966) is shown to be erroneous.
A Procedure for Calculating Daily Moisture Stress and Its Utility in Regressions of Tree Growth on Weather
Authors: Zahner Robert , Stage Albert R.
Published: May 2006

A method is described for computing daily values of moisture stress on forest vegetation, or water deficits, based on the differences between Thornthwaite's potential evapo—transpiration and computed soil—moisture depletion. More realistic functions are used for soil—moisture depletion on specific soil types than have been customary. These functions related daily rates of depletion to characteristics of soil—moisture tension. Separate functions account for surface soil wetting and drying processes following rain and during dry periods. Two methods of summarizing the day—to—day distribution of moisture stress are illustrated. One utilizes directly accumulated stress values during such logical growth intervals as periods of leaf flushing or bud setting. In an example of a regression of red pine shoot growth on water deficits, 72% of the variation in annual growth was accounted for by moisture stress during certain periods of both previous and current growing seasons. The second method computes moisture stress and weather variables as functions of time over two growing seasons and utilizes the coefficients of orthogonal polynomials as independent variables in regressions of growth. In an example of western white pine basal area growth utilizing this latter method, moisture stress accounted for a 28% reduction in the variance of growth remaining after the effects of temperature and precipitation per se had been removed. The complete model accounted for 78% of the total variation.
On the Ecological Significance of Bergmann's Rule
Authors: McNab Brian K.
Published: May 2006

A positive correlation of weight with latitude in homoiotherms (Bergmann's rule) cannot normally depend upon the physics of heat exchange. Most latitudinally widespread mammals in North America do not follow this rule. Those that do are usually carnivores or granivores; a change in their body size reflects a change in the size of their prey. A latitudinal change in the size of available prey is due either to the distribution of the prey species or to the distribution of other predators utilizing the same prey species. Only the smallest species of a set of similar predators normally will conform to Bergmanns rule, and then only beyond the limits of distribution of the largest species. These changes in size seem to be another example of character displacement.
Penetration of Bog Peats and Lake Sediments by Tritium from Atmospheric Fallout
Authors: Gorham Eville , Hofstetter Ronald H.
Published: May 2006

Tritium in surface bog peats of the Red Lake wetland, northern Minnesota, exhibits about the same concentration as in atmospheric precipitation, which is still appreciably enriched by tritium from nuclear weapon testing. Past input pulses are not preserved in the peat profile, and the pattern of subsurface decline suggests that most of the modern precipitation rich in tritium is removed rapidly by evapotranspiration and by lateral runoff within the top 1.5 m of the 3.5—m thickness of little—decomposed Sphagnum peat at the crest of the raised bog. However, some bomb tritium has penetrated, presumably by molecular diffusion, down to the discontinuity between the highly permeable Sphagnum peat and the underlying well—decomposed and much less permeable fen peat. In profundal lake sediments of four Minnesota lakes the influence of highly enriched precipitation from the early 1960's has likewise been largely transitory and of major significance only in sediment depths of less than 1 m, although some penetration below the depth has occurred, presumably by molecular diffusion.
Phytosociological Analysis of Oklahoma Upland Forest Species
Authors: Risser Paul G. , Rice Elroy L.
Published: May 2006

Ordiantional procedures have been employed to describe the vegetation in Oklahoma upland forests and demonstrate the position of individual species within this vegetation. Species ordinations provide a rapid and efficient method of demonstrating similarity in species behavior.
Principal‐Component Analysis of Interrelations Among Fungi, Mites, and Insects in Grain Bulk Ecosystems
Authors: Sinha R. N. , Wallace H. A. H. , Chebib F. S.
Published: May 2006

Interrelations among temperature, moisture, and viability of grain, and mites, insects, and fungi were studied from 8,135 samples collected at monthly intervals from two 13.6—ton wheat bulks stored in a granary at Winnipeg, Manitoba for 8 years during 1959—67. The bins were fumigated once with phospine (PH3) in August 1965, to determine the effect of the chemical on the existing relationships in the grain bulk ecosystems. Of the 32 possible principal components extracted from 32 variables by the principal—components method, the first 11, accounting for 65.6% of the total variability, were interpreted. The first principal component is a measure of general aging of the grain and fungal succession. The second and third principal components are measures of the major arthropod populations interacting with their physical environment. The analysis shows that Alternaria and its associates Gonatobotrys, Cochliobolus, Nigrospora, which are carried within seeds from the field, gradually disappear in storage and are replaced by Aspergillus versicolor, Aspergillus spp., Penicillium, Absidia, Chaetomium, Rhizopus, and Streptomyces. A grain mite Tarsonemus, which thrives mainly on Chaetomium, is the only arthropod that is positively correlated with the last group of fungi. The abundance of the granary arthropods, Cheyletus, Acarus, Glycyphagus, and Lepinotus is unaffected by time and most fungi, but appears to be regulated by a complex interaction of temperature, moisture, and, in some cases, the depth of the grain bulk. The predatory mite Cheyletus was related to its prey Glycyphagus and Lepinotus, but it did not effectively control the prey population. Interrelations among fungi and between some fungi and some arthropods in bulk grain ecosystems is confirmed statistically. The biological significance of the most important principal components and variables within these principal components are discussed.
Effects of Temperature, Salinity and Substrate on Distribution of Clymenella Torquata (Leidy), Polychaeta
Authors: Kenny Ron
Published: May 2006

The tube building polychaete worm, Clymenella torquata, occurs on the Atlantic coast of North America in estuarine situations. Investigations of the physical environment and the density of the worm populations in the Newport River estuary, North Carolina, showed that the species is found in greatest numbers near low water, in areas where the median particle size of the substrate is between 0.2 and 0.32 mm and where the salinity remains above 25%. From laboratory experiments on the survival of worms under controlled conditions a 50% lethal temperature of 39.2°C was recorded; and 15% salinity resulted in a 50% lethal time of 45 hr. The combined effects of temperature and salinity were tested. The efficiency of tube building under different conditions of temperature and salinity and with substrate particles of various sizes was tested and shown to be at a maximum at 25°C and 35% salinity using particles between 0.25 and 0.42 mm in diameter.
Morphological Changes in Swine Associated with Environmental Temperature
Authors: Weaver Morris E. , Ingram Douglas L.
Published: May 2006

Ten animals from two litters of English large white pigs were weaned at 12—15 days of age and placed one per cage within constant—temperature rooms. In the first group, a comparison was made between three animals raised at 5°C and their littermates raised at 35°C. There were marked differences in appearance and in gross morphology. Those from the cold environment had more hair, were shorter and more stocky, and had a shorter tail and smaller ears than their littermates. A second group of animals were raised at 20°C and 35°C; it was found that with respect to all measurements the 20°C pigs were intermediate between the 5° and 35°C animals. These observations accord with Bergmann's Rule that animals raised in colder environments are characterized by a reduced surface area/body weight ratio. The results likewise substantiate Allen's Rule that in colder climates the length of appendages and of extremities is reduced.
The Effect of Clumped Distributions in Sparse Populations
Authors: Rohlf F. James
Published: May 2006

Andrewartha and Birch's model for the effects of sparse populations in the sheep tick was reinvestigated and the results extended. Simple analytical solutions were found for the case in which ticks are distributed randomly. Clumped distributions of ticks were found to lower the probability of a female finding a mate unless the average number of ticks per sheep was less than unity.
Feeding Rates of Freshwater Snails (Goniobasis Clavaeformis) determined with Cobalt
Authors: Malone C. R. , Nelson D. J.
Published: May 2006

A short—term radionuclide method was developed for estimating feeding rates of snails inhabiting freshwater streams. Snails were allowed to feed for 1 hr upon the surfaces of rocks previously soaked in a Co60 solution. Organic detritus and aufwuchs were scraped from the rocks and assayed to determine radioactivity. When the dpm of Co60 mg—1 of food were known, the quantity of biomass ingested by the snails could be calculated by determining the radioactivity in the snails. Feeding rates varied both diurnally and monthly, suggesting periodicity in feeding activities and interactions with environmental factors.
Effect of Sea Water on Seed Germination in Two Pacific Atoll Beach Species
Authors: Lesko G. L. , Walker R. B.
Published: May 2006

The structure of the fruits and the physiology of the seeds of Scaevola taccada (Gaertn.) Roxb. and Messerschmidia argentea (L.) I. M. Johnst. facilitate dispersal by sea currents and subsequent germination. Fruits were floated on sea water for 120 days without significant loss in germination capacity. The seeds of fruits floated on sea water germinated 1—2 weeks sooner than dry seeds, when placed in nonsaline conditions. Both rate and percentage of germination in these species decreased sharply with the increase of salinity in the substratum, and became nil at a salt concentration less than half that of sea water. The data and the observations make possible a reasonable reconstruction of the transport of these species to the Marshall Islands and their establishment on the atoll beaches. The fruits are capable of drifting the length of the dissemination route suggested by Wiens (1962), and the seeds would not germinate en route. Exposure to rain on the beaches would result in rapid germination.
Changes in the Growth Pattern of White Pine Trees Undergoing Suppression
Authors: Bormann F. H.
Published: May 2006

The phenotypic responses of suppressed trees were studied in a 60—year—old white pine stand. The first evidence of suppression is a tree—wide decrease in the production of secondary xylem. Height growth is relatively insensitive. During the latter 30 years of life suppressed trees made 50.7% of their total height growth but only 19.1% of their total diameter growth. Eventually the cambium fails to cut off xylem at the base of the tree. With time, the sheath of new—formed xylem retreats from the based giving rise to an increasingly large zone of missing rings. Girdling experiments indicate that diminished supplies of food and growth regulators move through the zone of missing rings to support primary root growth. Apparently the phloem remains functional in the zone of missing rings. Either the phloem can function for periods greater than 1 or 2 years, or the cambium cuts off phloem alone in the missing ring zone. In the normal cambial cycle, phloem alone is produced during the last part of the growing season. It is proposed that a physiological threshold exists below which growth conditions are inadequate for the production of secondary xylem but remain favorable for the production of primary root growth and possibly for secondary phloem. This physiological mechanism is of considerable ecological significance since, as suppression proceeds, the plant invests a higher and higher proportion of its decreasing energy supply in primary growth or in all tissues that require annual renewal thus prolonging its survival. Hence, the growth of white pine, while undergoing suppression, illustrates the principle of phenotypic adaptability.
Shrub‐Carrs of Southeastern Wisconsin
Authors: White Keith L.
Published: May 2006

Shrub—carr vegetation over its full range of variation in southeastern Wisconsin was quantitatively analyzed and the influence of origin, environmental factors, and disturbance on the vegetation was investigated. Plant composition was sampled in 76 stands distributed over 13 counties. A list of common shrub—carr species was derived by combining presence with frequency or intercept data. Salix petiolaris and Cornus stolonifera were the most common of 38 shrub species. The vegetation had three distinct layers, an upper dominant shrub layer, an intermediate tall herb, grass, and sedge layer, and a low diminutive herb layer, but there was no stratification within the shrub layer. The pattern of plant distribution was very heterogeneous, due to irregularities in the soil surface and to disturbance. The response of common species to disturbance was indicated by arranging stands along a disturbance gradient. Most shrub—carrs in southeastern Wisconsin originated in the 1930's when shrubs colonized abandoned mowing meadows. The relative stability of the shrub—carr as a community appeared to be due to shrub resprouting after disturbance. Lowland forest undoubtedly invades the shrub—carr, although fire may kill seedlings and saplings and thus retard three invasion.
Effects of Prescribed Burning on Soil Microorganisms in a Minnesota Jack Pine Forest
Authors: Ahlgren Isabel F. , Ahlgren Clifford E.
Published: May 2006

Soil dilution plate counts on selective media for bacteria, streptomycetes, and fungi were made at intervals before and after two prescribed burns on 10—acre jack pine tracts. Carbon dioxide determinations were also made. These tracts were compared with similar tracts cut and unburned and uncut and unburned. Three—year results are given. The number and activity of most microorganisms decreased immediately after fire but rose abruptly to a very high level after the first rainfall following burning. This increase is believed caused by the leaching of ash minerals. Depth and extent of the effects were influenced by intensity of fire and moisture conditions. Number and activity of organisms were generally lower in burned soil the second growing season after fire. Some effects were still noticeable the third growing season. Streptomycete populations were greatly increased the third growing season. Rainfall also caused a fluctuation of microbial populations on the unburned tracts.
Plant Communities and Soil Moisture Relationships Near Denver, Colorado
Authors: Branson F. A. , Miller R. F. , McQueen I. S.
Published: May 2006

Plant communities and some causal factors were studied on a stony soil, on pebble mounds on stony soil, and on an adjacent soil derived from the Pierre Shale in an area 14 miles northwest of Denver, Colorado, at approximately 6,000 ft altitude. Average annual precipitation is 15.2 inches. The three dominant perennial species on the soil derived from Pierre Shale were buffalograss, blue grama, and western wheatgrass, all of which are characteristic of the mixed prairie association of the Great Plains. True prairie species characteristic of prairies of the Midwest, big bluestem, little bluestem, Indiangrass, switchgrass, and prairie dropseed, were present in significant amounts on the stony soil; however, most of the other species were montane. Some of the montane species were mountain muhly, sandwort, and beardtongue. More than twice as many species occurred on the stony than on the other two soil conditions. The greater availability (lower tensions) of soil moisture in the stony soil appears to be the primary cause of the larger number of species and generally more mesic flora. Infiltration rates were highest on pebble mounds and stony soil. Although the stony soil contained less zinc, potassium, sodium, and sulfate, plant species from the stony soil contained larger quantities of these nutrients. The higher pH in the shale—derived soil (7.1 as compared to 6.0—6.3) and larger quantities of montmorillonitic clays may have reduced the availability of these nutrients to plants. The presence of vegetation on pebble mounds that indicates either disturbance or droughty conditions is attributed to the activities of the mountain pocket gopher. Species prominent on mounds were cheatgrass, sixweeks fescue, ragweed, and hairy goldaster. Similar soil moisture conditions in mounds and in stony soil indicate that the two soils should have the same kind of vegetation if disturbance is not a factor. Evidence suggests that pocket gophers may be the causal factor for both the mounds and the subclimax vegetation on mounds.
Growth Response of Two Sedges Inhabiting a Radioactive Waste Disposal Area
Authors: Plummer G. L. , Crossley D. A. , Gardiner D. A.
Published: May 2006

An observed increase in the size of the inflorescences of two sedges inhabiting a radioactive waste disposal area is correlated with the complex interaction between various edaphic factors that contribute to plant growth and an "effect" of ionizing radiation. The perennial sedges, Carex frankii and Carex vulpinoidea, tolerate a continuous dose rate generally in excess of 2 R/day at ground level. Although radiation has been associated with excessive plant growth, it is not entirely independent of other factors, such as the combined contribution of potassium and organic matter, soil pH, calcium, as well as other unmeasured edaphic conditions.
Foliar Nitrogen and Phosphorus Level Related to Site Quality in a Northern Minnesota Spruce Bog
Authors: Watt Richard F. , Heinselman M. L.
Published: May 2006

Channels of relatively rapid water movement, termed "water tracks," in black spruce bogs in former glacial Lake Agassiz are often associated with a rich flora and shallow peat. Adjacent areas of lesser water movement are characterized by a depauperate, less productive flora and deeper peats. Black spruce foliage, collected from transects running from the good site in the water track with vigorous stands to the very poor muskegs bearing stunted trees one—fourth mile distant, was analyzed for 13 mineral elements. Nitrogen and phosphorus levels were significantly correlated with site quality; potassium displayed an inverse correlation. Levels of N and P were low, generally below the point at which deficiency symptoms have been reported for this or other spruces. The inverse relationship of potassium is a growth dilution effect, since the levels appear sufficient on all sites. The higher levels of nitrogen on good sites may be attributed to nitrogen fixation by speckled alder, which is abundant on the good sites but absent on poorer sites. More rapid decomposition of litter, indicated by lesser depth of peat accumulation, movement of enriched water, and nearness of mineral subsoil, may influence the level of N and P in the water track. Other elements were not related to site quality for black spruce.
Branch Dimensions and Estimation of Branch Production
Authors: Whittaker R. H.
Published: May 2006

Branches are organs of complexly interrelated dimensions; despite the relative flexibility of plant growth, high correlations connect most external branch characteristics. Complex interrelations also connect internal characteristics–mean and total cross—section area of branch segments of a given age, number, length, and weight of segments, and wood radial increment and productions–, different patterns of taper along the length of branches appear in different characteristics. Radial wood increment and amount of wood growth decrease from young terminal branchlets down to the base of the branch axis, and amounts of wood production differ widely between vigorous and slow—growing branches. Estimates of branch production are possible from regressions of branch dry weight in relation to branch age. Analyses of actual growth in samples of Rhododendron maximum and Quercus alba branches indicate that such estimates are generally overestimates because growth rates from regressions are excessive when applied to less vigorous branches. The amount of error is not necessarily small but may be acceptable in production research, particularly if some correction for slower growth of some branches is possible.
Comparative Chlorophyll and Energy Studies of Prairie, Savanna, Oakwood, and Maize Field Ecosystems
Authors: Ovington J. D. , Lawrence D. B.
Published: May 2006

Estimates are given of the concentrations and total quantities of chlorophyll (a + b) and energy in the plant matrial present in prairie, savanna, oakwood, and maize field ecosystems at different times through 1959. Marked differences in chlorophyll and energy contents were recorded both between ecosystems and seasonally at each ecosystem. While large amounts of energy are held from year to year in natural ecosystems, the annual production of plant material only accounts for a small part of the annual incident solar radiation. The results are discussed in relation to the factors affecting the potential capabilities of vegetation for energy accumulation.
Temperature and Development of the Wood Frog, Rana Sylvatica, in Alaska
Authors: Herreid Clyde F. , Kinney Stephen
Published: May 2006

Wood frogs breed in a variety of ponds and lakes in central Alaska. Dates of first appearance of frogs ranged from 24 April to 22 May. Egg laying began 4—6 days later. Egg laying was completed in a pond 4—8 days after the first egg mass appeared. Wood frogs tend to lay their egg masses at the same spot. The average number of eggs per mass was 778 with an egg diameter of 1.6 mm. Development of eggs was directly related to water temperature and occured at the same rate as that shown for wood frogs from New York. Temperature limits that permit at least 50% survival of eggs through hatching were 6°—24°C. Temperature tolerance of eggs and tadpoles varied with age and acclimatization. Temperature preference of tadpoles followed a normal curve and ranged from 9° to 29°C. Development in the field varied among different ponds and different years. Rapid growth occured once the larvae were free swimming. Average maximum weight ranged from 2.15 to 2.85 g; maximum length varied from 5.5 to 6.0 cm. Time to metamorephosis ranged from 53 to 78 days. Two periods of development are distinguished: In period I, fertilization to free—living stage, growth rate is determined by water temperature. This period occupies one—third of the development time but has a higher mortality rate than period II. The later period includes the free—swimming stage until climax metamorphosis, and development rate is determined by environmental factors such as food and population density, as well as temperature.
Population Ecology of Feral House Mice
Authors: DeLong Karl T.
Published: May 2006

Demographic changes which occurred during population fluctuations in the field were studied by live—trapping six populations during a two—year period. An attempt was made to determine the factors which prevent unlimited population increase. Four major population declines were observed. Epidemic disease caused mortality in one. A second population declined in the fall when insufficient food caused cessation of reproduction. The addition of supplemental food on two experimental grids, however, was sufficient to support both high growth rates and high recruitment of young during the winter, but supplemental food was not sufficient to maintain breeding indefinitely. These populations declined during the usual breeding season in the presence of supplemental and natural food, abundant cover, and few predators. It therefore seemed probable that these two populations were not limited by external factors, but by some intrinsic mechanism. Increased emigration and mortality, primarily of juveniles and subadults, occurred during the latter part of the population increase, but the decline of these populations was primarily caused by a large reduction in the number of weaned young per lactating female, and finally by cessation of breeding conditions in females. Several general characteristics of these populations were established. Body growth rates were highest during the late spring and early summer and lowest during the winter. Home ranges were first established by juveniles or subadults, and were rarely shifted unless the animal left the population. Similarly, the mean length of daily movement by any weight group did not vary greatly, even with a change in breeding activity or population density. Both mortality and dispersal, however, were affected by the breeding condition of the population. In breeding populations, mortality and dispersal of juveniles and subadults increased markedly as density increased, whereas during the nonbreeding season, those parameters were not affected by the weight of an animal, density, or supplemental food.
Influence of Volcanic Eruptions on Xylem Growth Patterns
Authors: Eggler Willis A.
Published: May 2006

Xylem formed in four pine trees growing near Paricutin Volcano, Mexico, during 8 years of volcanic activity had several kinds of abnormalities, including narrow, wide, asymmetrical, and incomplete annual growth layers, and abnormally low, as well as high, ratios of dense to porous wood. Five other pine trees were studied 12 years after volcanic activity had ceased. Only one of them was consistently producing normal annual growth layers. Among the others porous wood was produced almost exclusivcely, making it impossible to correlate growth layers with years. Reduced supplies of photosynthate, poor aeration, and abnormal supply of auxin may be responsible for the abnormal growth pattern.
Soil Respiration of Tropical Vegetation types
Authors: Schulze E. D.
Published: May 2006

Soil respiration rates, measured during the dry season of 1966 in Costa Rica by absorption of CO2 through KOH followed by titration with HCI, were lowest in the savanna and the decidous forest (300—400 mg CO2/m2/hr); they were between 1,000 and 2,000 mg CO:2/m2/hr in the gallery forest and the wet forest; and were highest in the secondary growth vegetation (2,556 mg CO2/m2/hr). The results were related to the climatic conditions in these habitats. The climate limits the development of organisms in the soil and the primary production in the vegetation. Comparisons of European, Canadian, and tropical soil respiration rates show the limitation of soil respiration through limitations of primary productivity.
Isolation of Azotobacter Insignis From Fresh Water
Authors: Johnstone Donald B.
Published: May 2006

Azotobacter insignis Derx has been isolated from flowing fresh water streams in Vermont and appears most frequently associated with submerged aquatic plants. This is the first report of this strictly aquatic species of aerobic nitrogen—fixing bacteria in North America. Added to the isolations in Java, Denmark, and Scotland it suggests a wide distribution.