bluuebunny/crossref_metadata_2025 huggingface dataset:
Canopy‐Coverage of the Desert Shrub Vegetation Mosaic of the Nevada Test Site
Authors: Rickard W. H. , Beatley Janice C.
Published: May 2006

Canopy—coverage of shrubs and perennial herbs was determined on 44 relatively undistributed sites scattered throughout the vegetation mosaic covering valleys in southcentral Nevada. The dominant shrubs were Larrea divaricata, Grayia spinosa, Lycium andersonii, Coleogyne ramosissima, atriplex confertifolia, Artemisia tridentata, and A. arbuscula subsp. nova. Perennial herbs contributed little to canopy—coverage. The perennial herbs most frequently encountered were Oryzopsis hymenoides and Stipa speciosa. In the spring of 1960, on 34 of the same sites, the canopy—cover of annual herbs was also determined. Sites dominated by Larrea shrubs had more annual species and also the greatest amount of annual cover. Chaenactis stevioides was ubiquitous and often the dominant annual encountered throughout the vegetation mosaic. Other important annuals was Mentzelia veatchiana, Eriogonum maculatum, Eriophyllum pringlei, Bromus rubens, Cryptantha nevadenseis, C. circumscissa, and Amsinckia tessellata.
Dry Matter Losses and Mineral Leaching in Bluestem Standing Crop and Litter
Authors: Koelling Melvin R. , Kucera C. L.
Published: May 2006

Changes in mineral composition were observed for current growth and standing crop of prairie bluestem, Andropogon spp. Simulated litter samples of big bluestem, A. Gerardi, separated into foliage and flower stalk fractions were also analyzed over a 2—year period. Considerable leaching or transfer of various constituents, especially nitrogen, phosphorus, magnesium, and potassium, occurs in the standing crop prior to deposition in the litter. Potassium showed a 96% turnover in the vegetation before the end of the first year. Silica showed a distinct rising trend with age of the standing crop. This trend continued through the litter phase and accounted for a major portion of the total mineral oxide. Dry—matter losses in the litter samples were about 50% more rapid for foliage than for flower stalks. This difference in decay rates is attributed to less water—soluble product in the latter. Total ash after 2 years of decomposition in the litter samples was approximately twice the initial level for both foliage and flower stalks. Whereas percentage of nitrogen showed a decreasing trend during the first year in the standing vegetation, nitrogen levels increased on a percentage dry weight basis during the litter phase. Increasing nitrogen in the litter, compared to relatively more rapid dry—matter losses, suggested a narrowing of the C/N ratio as decomposition progressed. Higher nitrogen concentrations in the foliage collected from control plots than from burned plots are attributed to slower growth and less biomass production, compared to greater grass productivity on fire plots.
Radiation Screens for Air Temperature Measurement
Authors: MacHattie L. B.
Published: May 2006

Thermometers shaded from direct sunshine may read 5{\circ}—10{\circ}F higher than air temperature, due to terrestrial and reflected solar radiation. An experimental comparison of four types of thermometer screens close agreement at night or under canopy; but in sunshine the thermometer in one screen read 1 degree—3 degrees F higher than ambient air temperature.
Killdeer (Charadrius Vociferus Linnaeus) as a Means of Dispersal for Aquatic Gastropods
Authors: Malone Charles R.
Published: May 2006

Two species of fresh—water snails were found capable of attaching themselves to the feet of killdeer. Once attached and removed from water, the snails remained attached and retained their viability for sufficient lengths of time to effect passive overland dispersal.
High Temperature Tolerances of Bufo Hemiophrys and Bufo Cognatus
Authors: Schmid William D.
Published: May 2006

Temperature tolerances of Bufo hemiophrys and B. cognatus were examined by exposing specimens to lethal high temperatures. Bufo cognatus was able to tolerate significantly higher temperatures than B. hemiophrys. The results yielded an estimated interspecific difference in upper lethal temperature of 2.34 degree plus or minus 0.41 degree. This different was correlated with the geographic distributions of the two species; i.e., the more southern species, B. cognatus, was able to tolerate higher temperatures. This has been taken to indicate that a physiological specialization has taken place which is adaptive for the two species in the microclimates of their respective habitats.
Evidence for Regulation of Community Metabolism in a Marine Ecosystem
Authors: Copeland B. J.
Published: May 2006

The light intensity on a marine ecosystem containing turtle grass as the dominant producer was changed from 1500 ft—c to 230 ft—c. Immediately after the light reduction, community metabolism decreased rapidly. This was followed by a gradual increased in metabolism util it reached the previous level. The dominant producer changed from turtle grass to blue—green algae.
Productivity of Inbred Strains of Tribolium Confusum and Tribolium Castaneum
Authors: Crenshaw John W. , Lerner I. Michael
Published: May 2006

Studies of the variation in productivity in inbred strains of Tribolium confusum and Tribolium castaneum were undertaken to determine the effects of inbreeding on different strains of common ancestry. Six strains of each species were tested after eight to ten generations of inbreeding by full sibling crosses. The founding parents of each strain were taken from synthetic populations, on of T. confusum, another of T. castaneum, each of which had been established by systematic crosses involving stocks of different origin. Three pairs of sibling strains, two of T. confusum, one of T. castaneum, each pair derived from the same ancestral parents in the founding generation of inbreeding, were included in the 12 stains investigated. In length of productivity period, significant interstrain variation in means and variances was found for the strains of T. castaneum investigated. Differences between the strains of T. confusum examined were found to be not significant. In total 120—day productivity, significant intraspecies, between—strain variation in means and variances was found for both T. confusum and T. castaneum. Analysis of per—day productivity for a 40—day period revealed significant strain differences in productivity in T. confusum; interstrain differences in variance could not be demonstrated. In T. castaneum, significant interstain variation in means and variances was found. Interstrain differences in productivity reflect genotypic differences due to inbreeding as well as genotypic differences of the founding parents of the different strains. Differences between sibling strains, having the same founding parents, are attributable to inbreeding only. The two sibling strains of one pair T. confusum tested exhibited remarkable similarity in all traits compared. The other pair of T. confusum showed slight though significant differences only in total 120—day productivity period and per—day productivity. Difference in total productivity fell short of significance, but the difference in variances was significant. Apparent interstrain variation is greater in T. castaneum than in T. confusum for all three traits analyzed. T. castaneum appears to perform relatively better and T. confusum relatively less well in competition experiments than would be indicated by their basic productivity.
Fossil Pine Pollen and Full‐Glacial Vegetation in Southeastern North Carolina
Authors: Whitehead Donald R.
Published: May 2006

A reassessment of the difficulties inherent in size—frequency identification of pollen indicates that the reliability of the method is of low order. Accurate identifications assume: (1) Adequate data on size variation for all relevant extant species; (2) a standardized method of preparation for all modern samples; (3) use of mounting medium in which size is stabilized (not glycerine or glycerine—jelly); (4) preparation of all samples from a given fossil profile by an identical technique (not necessarily the same as that employed for modern material); (5)cognizance of the fact that size of modern and fossil grains cannot be compared directly and that the size changes may occur as a function of sediment type within a profile; and (6) presentation of size—frequency curves for the fossil material. New Pollen size measurements for the 13 eastern pines indicate that no single species can be identified on a size—frequency basis. The mode for small pine grains described by Frey from the full—glacial portion (M Zone) of the Singletary Lake profile could have been contributed to by either jack pine or red pine (or both). These data and new pollen analyses from the M Zone sediments suggest that the dominant full—glacial forest type in the region consisted of widely spaced pines (jack and/or red pine) associated with heliophytic herbs and shrubs (Artemisia, Polygonella, Plantago, Ambrosia, caryophylls, and chenopods). Boreal elements (Picea, Abies, Schizeae pusilla, Sanguisorba canadensis, Lycopodium annotinum, L. lucidulum) may have occurred on more mesic sites surrounding the lakes or on the poorly drained inter—Bay regions.
Uptake and Transfer of Cesium‐137 by Chlamydomonas, Daphnia, and Bluegill Fingerlings
Authors: King Susan F.
Published: May 2006

Concentration factors of Cs—137 for Chlamydomonas moewusii, Daphnia pulex, D. magna, and Lepois macrochirus fingerlings were determined following direct exposure to the isotope in solution and following ingestion of labeled food by the daphnids and fish. Cesium specific activity, temperature, and algal cell concentration were varied to determine effects on Cs—137 uptake. of Cs—137 by all organisms was less at 8° than at 22°C. Chlamydomonas uptake rose with increase of available cesium in the water up to 1.0 ppm and fell with increasing algal densities. Cesium uptake bu D. pulex and D. magna differed. D. pulex uptake of Cs—137 increased but D. magna uptake was not affected when available labeled Chlamydomonas was increased. In direct uptake studies at 22°C, D. pulex concentrated three times the amount of Cs—137 concentrated by D. magna. Direct uptake of Cs—137 by L. macrochirus was negligible. Fingerlings showed increased uptake when allowed to feed for 24 hr on labeled daphnids. Efficiency of removal of Cs—137 from ingested food was 21% for D. pulex, 13—14% for L. macrochirus, and 0.0% for D. magna. In on food chain study at 22°C, Chlamydomonas, at 20 x 107 cells/liter, reached a 24 hr concentration factor of 319; D. pulex, after feeding on the labeled alga for three days, had a concentration factor of 354; and the striated muscle tissue of L. macrochirus, which had fed for one day on the labeled D. pulex, had a concentration factor of 7.8. Rad dosages received by each species from Cs—137 decay in the water and organisms were calculated. Based on the concentration factors given in the above food chain study, Chlamydomonas received 0.11 rads/day, D. pulex 8.5 rads/day, and L. macrochirus muscle 0.38 rads/day.
A Comparison of Some Species‐Individuals Diversity Indices Applied to Samples of Field Insects
Authors: Menhinick Edward F.
Published: May 2006

A comparison was made of several cumulative species/cumulative individuals indices using a statistical distribution corresponding to the species of insects in a sample from the herb stratum of a lespedeza field. Criteria used in comparison were that the indices be intensive for a given universe regardless of sample size and that the indices differentiate between universes having different numbers of species for a given number of individuals. Species/log individuals, species–1/natural log of individuals, log species/log individuals, and species/square root of individuals were examined. Only the index of species/square root of individual met both of the criteria.
A Possible Ecological Relation Between Soil Disturbance, Light‐Flash, and Seed Germination
Authors: Sauer Jonathan , Struik Gwendolyn
Published: May 2006

A connection is suggested between two well—known but hitherto unrelated phenomena: germination under field conditions of certain seeds following soil disturbance and germination in laboratory experiments of certain seeds following brief exposures to light. A light—flash mechanism for breaking dormancy is proposed as a possible adaptation aiding pioneer plants in exploitation of disturbed habitats.
A Summer Carrion Study of the Baby Pig Sus Scrofa Linnaeus
Authors: Payne Jerry A.
Published: May 2006

A carrion study of the baby pig, Sus scrofa Linnaeus, was conducted during the summers of 1962 and 1963 in a mixed mesophytic hardwood—pine community at Clemson, South Carolina. Six stages of decomposition were delimited for carrion exposed to arthropods: fresh, bloated, active decay, advanced decay, dry, and remains. Five stages were recognized for carrion protected from arthropods: fresh, bloating and decomposition, flaccidity and dehydration, mummy, and desiccation and disintegration. Carrion free of insects decomposed and dried very slowly, retaining its form for many months, while 90% of the carrion open to insects was removed in 6 days. Carrion temperature during the bloated through advanced decay stages differed widely from that of air or soil. A definite ecological succession occurred among the fauna of carrion. Each stage of decay was characterized by a particular group of arthropods, each of which occupied a particular niche. Their activities were influenced by physical properties of carrion, rapidity of putrefaction, time of day, and weather. A total and 522 species representing 3 phyla, 9 classes, 31 orders, 151 families, and 359 genera were collected from decomposing pigs. Four orders of arthropods (Coleoptera, Diptera, Hymenoptera, and Araneida) accounted for 78% of the carrion fauna. Two coleopterous families, Histeridae and Staphylinidae and three dipterous families, Sarcophagidae, Calliphoridae, and Muscidae, represented 26% of the fauna.
Diurnal and Seasonal Patterns of Net Assimilation in Douglas‐Fir, Pseudotsuga Menziesii (Mirb). Franco, as Influenced by Environment
Authors: Helms John A.
Published: May 2006

A 2—year study on net assimilation was carried out in a 38—year—old natural stand of Douglas—fir. Five trees in each of the dominant, co—dominant, and suppressed crown classes were studied using the cuvette method on intact branches and measuring the CO2 exchange with an infrared gas analyzer. Light intensity, air temperature, and relative humidity were monitored using selenium photocells, thermocouples, and a 2—mv, 24—line recorder. The net gain in photosynthesis in 1962 was found to be two to three times that in the drier year of 1961. Expressed per unit weight of dry foliage per hour, suppressed foliage possessed higher photosynthetic efficiency than co—dominants, which in turn were slightly more efficient than dominants. Douglas—fir could photosynthesize at low light intensities. The CO2 compensation point was commonly as low as 10 ft—c, and maximum rates of net assimilation were attained at 800 ft—c. Net assimilation could not be predicted from specific levels of air temperature, light intensity, or relative humidity, but not found to be directly related to light intensities below 750 ft—c and to air temperatures above 30°C. Apart from these extreme situations, net assimilation under natural conditions is apparently limited by the interaction of many internal and external factors. Diurnal patterns of net assimilation differed in trees of different crown class. The rates of photosynthesis and nocturnal respiration commonly fluctuated within each diurnal pattern despite apparently stable environmental conditions. The causes of midday depressions are complex as depressed patterns occurred under hot conditions in summer and under cool, foggy conditions in autumn. Bursts of CO2 evolution immediately after sundown, lasting up to 2 hours, were commonly observed in summer and autumn.
Comparative Physiological Ecology of an Arctic and Alpine Population of Thalictrum Alpinum L.
Authors: Mooney H. A. , Johnson Albert W.
Published: May 2006

An ecological comparison was made between an alpine population of Thalictrum alpinum L. from the White Mountains of California and diploid and triploid plants of an arctic population from Ogotoruk Creek, Alaska. In a uniform environment plants of the alpine population were found to differ physiologically from the arctic plants in their photoperiod requirement, temperature of optimum photosynthesis, and photosynthetic light efficiency. Arctic triploid differed from diploid plants primarily in their greater vigor and photosynthetic capacity. Certain of the physiological differences between populations correlate with structural leaf characteristics, and are comparable to those previously found between arctic—alpine populations of Oxyria digyna. The ecological differences between the arctic chromosome races are discussed in relation to polyploid frequency in the arctic.
Radio Tracer Demonstration of Isopod Herbivory
Authors: Paris Oscar H. , Sikora Anne
Published: May 2006

Some food resources of Armadillidium vulgare were investigated by tagging plants in the field with 32P. Uptake of radionuclide by isopods in plots in which different plants had been tagged indicated that the animals utilized Silybum marianum and Vicia sativa as food. It was demonstrated that Armadillidium is a grazer as well as a scavenger in grassland. A broad adaptability in resource utilization probably contributes to the isopod's ubiquitousness and success as an invading species.
Tree Leaf Energy Balance
Authors: Knoerr K. R. , Gay L. W.
Published: May 2006

Detached leaves of three tree species, Quercus velutina, Magnolia grandiflora, and Prunus caroliniana, were exposed in transpiring and non—transpiring situations under high radiation intensities to a range in wind velocities. Convective heat losses from these leaves were determined as a residual in the energy balance equation, with all other energy exchange components being measured or known. The leaves responded to their external environment in accordance with accepted heat transfer theory. Leaf—air temperature differences were maximum for non—transpiring leaves in still air, and minimum for transpiring leaves exposed to high wind velocities. Convective heat transfer coefficients, calculated from the measurements of convection, were compared with those determined from heat transfer theory. The forced convection coefficients agreed closely with those predicted by theory. The free convection coefficients, however, were close to the theoretical values only for the larger leaves. They increased to about twice the predicted values as leaf size decreased. Reasons for this difference are discussed. The ratios between convection and latent heat exchange (Bowen ratios) for the individual leaves were different from published values for whole forest stands. These differences are considered in discussing the relative role of individual heat transfer processes in various portions of the tree crown.
Phenology of Alpine Plants in Northern Colorado
Authors: Holway J. Gary , Ward Richard T.
Published: May 2006

During the summers of 1960 and 1961 ten primary phenology stations, representing variations in slope, exposure, elevation, snow cover, and vegetation cover, were established in a 300—acre study area, ranging from 10,600 to 11,200 ft elevation in the northern part of Rocky Mountain National Park, Colorado. At each station approximately 75 plants of various species were observed weekly from early June to late September. Measurements of the physical environment were recorded at least twice a week. June and July were characterized by moderate to strong winds and frequent thundershowers. Air temperature maxima were mostly between 50 degrees and 70 degrees F, and night minima were typically between 30 degrees and 50 degrees F. Soil temperatures at 15—cm depth were commonly 40 degrees—50 degrees F. Precipitation from June 10 to September 10 ranged from 3.5 to 8.9. in. in the 2 years. Initiation of new growth for many species at the relatively snow—free stations occurred in May, and as late as early August in snow—accumulation areas. Most species showed definite signs of dormancy by the middle of September. The duration of phenological phases varied considerably, but the following ranges were common: in bud, 2—5 weeks; in flower, 2—3 weeks; in fruit, 4—5 weeks. There was notable stability in phase duration for a given species, even at quite different sites. Snow cover is considered to be the primary factor influencing phenology. Possible correlations of penology with environmental data are suggested, including the relationship of moisture uptake and consequent development to soil temperature.
Viability of Wild Meadow Voles Under Various Conditions of Population Density, Season, and Reproductive Activity
Authors: Clough Garrett C.
Published: May 2006

Wild meadow voles, Microtus pennsylvanicus, from four undisturbed populations were studied to learn the influence of population density, season, and reproductive activity on survival time in acute stress and on gland weights. Survival time in cold water was longer in winter. Survival time showed no correlation with population density in fall samples taken from very sparse to very dense populations. Thymus weights were lower in breeding voles and lower in winter. Adrenal weights were greatly influenced by reproductive activity, being increased in females and decreased in males. The results of the two survival tests used on one population, fasting—dehydration and cold water, showed different trends of change during two winters. In two experiments covering two to four months, the effect of density on survival time and gland weights was studied by manipulation of vole numbers on an island and in large outdoor pens, to create populations of high and low density. The average survival time in cold water and the gland weights showed no differences related to density. Analysis of the correlations between survival time in cold water and gland weights indicated that the adrenal, thymus, and spleen weights were not useful as indicators of viability. It is postulated that changes in mortality rates as a result of decreased viability due to dense population conditions play a minor role in fluctuations of rodent numbers.
Competition between Varieties 2 and 3 of Paramecium Aurelia: The Influence of Temperature in a Food‐Limited System
Authors: Hairston Nelson G. , Kellerman Sara L.
Published: May 2006

Abstract. Variety 2 of Paramecium aurelia won over Variety 3 in laboratory competition experiments at 5, 15, 20, and 25°C, even when Variety 3 was given a 6:1 advantage. The result was obtained most rapidly at 5°, and Variety 3 persisted longest at 15 and 20°. A four‐fold difference in food made no difference in the rate at which Variety 2 won, suggesting that at both levels food was severely limiting to the populations. Different combinations of stocks of the two varieties produced significantly different rates at which Variety 2 won. The data are consistent with the hypothesis, derived from field data, that Variety 3 is excluded from certain habitats by competition with Variety 2. A consistent morphological difference between the two varieties is described.
Ecology of Three Sympatric Species of Parasitic Insects of the Genus Megarhyssa (Hymenoptera: Ichneumonidae)
Authors: Heatwole Harold , Davis Donald M.
Published: May 2006

Three species, Megarhyssa atrata lineata, M. macrurus lunator, and M. greenei greenei were studied in beech—maple forests in Michigan . All are diurnal with similar activity patterns except that female M. atrata maintain a high degree of activity later in the day than do the others. Saturation deficits above 10 g/m2 inhibit activity whereas normal summer daytime temperatures do not. There does not seem to be a significant difference between time of emergence of females and of males in the spring, nor are there differences in seasonal occurrence of the various species except that M. Greenei may persist slightly longer in the fall. Insects of both sexes and of all species tend to return repeatedly to the same log or stump with but a limited amount of movement between sites. Adults rest on the undersides of beech and maple leaves during inactive periods. Since there are more such places than individuals to use them, competition for shelter does not seem to occur. Neither do adults compete for food. The larvae of the three species are largely segregated ecologically in that they parasitize different segments of the host population. This depends on the facts that (1) the adults select a host larva at a depth in the wood so that complete insertion of the ovipositor at right angles to the surface of the wood will just reach it, (2) the ovipositors of the different species are of different lengths, and (3) the host larvae maintain themselves at about the same depth in the wood for most of their larval period. There is succession of species on a given log but not to the extent that the three species would be ecologically segregated without the above mechanism. The sequence of species in the succession seems to depend on differences in ovipositor length. Females are usually more abundant on logs when a species is invading a new log; males are usually more numerous in the declining phase. Adults can live at least 27 days. Predators in the area were robber flies and perhaps a chipmunk. Incidence of parasitism of Tremex by Megarhyssa was 26.7% in part of a log which was examined.
The Abert Squirrel and Its Dependence on Ponderosa Pine
Authors: Keith James O.
Published: May 2006

The Abert squirrel (Sciurus aberti aberti) occurs throughout the ponderosa pine belt in central Arizona where it appears to have become ecologically dependent on ponderosa pine. Studies of the squirrels and their relationship to ponderosa pine were conducted at the Fort Valley Experimental Forest and adjacent areas on the Coconino National Forest near Flagstaff, Arizona, between October 1953 and June 1955. Adult squirrels molt twice each year, and their summer and winter pelages are somewhat different in color shade and pattern. In a sample of 313 adult squirrels, males weighed an average of 589 g; females, 60 g. Body measurements are similar between sexes, except that females apparently have longer tails. The squirrels obtain most of their food from ponderosa pine. The inner bark of terminal twigs is the principal food during winter, and ovulated cones are preferred in summer. Staminate flowers and apical buds of pine are also important foods. Other foods include fleshy fungi, carrion, and bones. The home range of squirrels was determined in summer by trapping and in winter by mapping areas of activity in snow. On the average, squirrels ranged over about 18 acres during summer and five acres in winter. Squirrels are strictly diurnal and in 1954 were active and fed each day even in inclement weather. Abert squirrels build nests in the branches of ponderosa pine. These nests, composed of pine twigs, have an outside diameter of about one and one—half feet and an inside diameter of six inches. Squirrels do not prefer any particular site in the tree for their nest. They may occupy several nests during a year. In 1954 squirrels bred only in May at Fort Valley. The gestation period was estimated at about 40 days, and young squirrels were born between June 10 and July 12. Litter size varied from two to five and averaged 3.4. Of 729 squirrels collected during different years, 57% were male and 43% were female. Young squirrels had thick ear tufts in September, but on adults tufts were absent or very thin at that time. This difference is the best available criterion of age. The obvious causes of mortality did not appear to be responsible for the considerable losses that evidently occurred during the winter of 1953—54; other factors must have reduced squirrel densities. The number of feeding sites evident after fresh snows is a reliable indicator of squirrel density. Counts of the total number of twigs clipped by squirrels during winter appear to be related to population densities and differences between years should indicate trends in populations. In central Arizona squirrels are now apparently less numerous than at the turn of the century. This is probably due to the deterioration of squirrel habitat caused by logging and lack of adequate pine regeneration. Short—term fluctuations in population are believed to be caused by variations in quality and quantity of food supply which in turn may be related to the reproductive cycle of ponderosa pine. Intensive forest management should result in larger and more stable populations of the Abert squirrel.
Interactions of Peromyscus and Mus in a One‐Acre Field Enclosure
Authors: Caldwell Larry D. , Gentry John B.
Published: May 2006

Peromyscus polionotus (old—field mice) and feral Mus musculus (house mice) have coexisted in a large old—field area at the AEC Savannah River Plant for 12 yr following removal of human habitations and the abandonment of agriculture in the region, but in two replicate experiments a Mus population has failed to survive when the two species were confined to a one—acre enclosure in the field. In the second experiment, as described in this paper, five Mus were introduced into the enclosure in December 1960 and nine Peromyscus in June 1961. Rapid population growth in both species occurred in the fall of 1961 until about 23 of each species were present, a much bigger density than occurred outside the enclosure. A decline in recruitment rate and a continued high disappearance rate in the Mus population resulted in a gradual decline and extinction of this species; whereas the Peromyscus population maintained itself at a level of 20 to 28 individuals. The two species at first occupied separate areas in the enclosure, but common occupancy of feeding areas increased as the density increased. It was concluded that interspecific competition for seeds was important in the outcome of the experiment, and that the migratory behavior of Mus greatly reduces competition with the more sedentary Peromyscus when populations of the two species are not confined to a limited area.
Breeding Dates of Rana Sylvatica at College, Alaska
Authors: Kessel Brina
Published: May 2006

At College, Alaska (64 degrees 52' N. Lat., 147 degrees 49' W. Long.), Rana sylvatica usually commences breeding activities during the last week of April or the first week of May (extremes from 1952 through 1963 ranged from 24 April to 18 May). Phenologically, these frogs breed as early as seems possible for a terrestrial poikilothermic vertebrate, and annual variations in breeding dates appear largely due to variations in the spring thaw conditions which, in turn, are related to environmental temperatures and to persistence of snow cover.
Medium Perfusion in Cultures of Small Aquatic Animals
Authors: Salt George W.
Published: May 2006

For experiments on animal populations which run for extended periods of time, a method of removal of medium is needed in order to avoid accumulation of metabolites and inhibition of population processes. This can be done for cultures of small aquatic organisms, such as protozoa, by using a filter paper wick which removes fluid by capillary action. The animals are not removed. A like volume of fresh fluid is added after each removal to maintain a constant volume. To prevent drying of the wick, the culture dish and wick are kept in a saturated atmosphere inside a glass cabinet or box.
Population Regulation and Population Inertia
Authors: Murdoch William W.
Published: May 2006

Regulation is defined as the return of a population to equilibrium density. An operational definition of regulation is convergence to a single density by subpopulations which have been manipulated previously to different densities. The equilibrium density may be fixed or variable. If the equilibrium is variable then regulation may produce instability (numerical inconstancy) and non—density—dependence. Population inertia is the tendency for a population to resist changes away from its current density. If speed of regulation is defined as |s|, the speed of convergence to equilibrium, then inertia is 1/|s|. The evolution of mechanisms of inertia involves changes in the demographic functions, mediated through physiology or behavior, which keep the rate of numerical change low. It is not clear if populations are control systems or non—control systems, which makes the convergence experiment difficult to interpret theorectically. Experiments and observations are needed which will try to distinguish, among stable populations, between those with tight regulation and those with high inertia.
Fitting Nonlinear Models to Biological Data by Marquardt's Algorithm
Authors: Conway Gordon R. , Glass Norman R. , Wilcox Jerome C.
Published: May 2006

Equations describing biological phenomena frequently have parameters entering nonlinearly. A highly efficient method for determining the values of parameters in such equations that will give the best least—squares fit to a set of data is Marquardt's algorithm. A step—by—step derivation of the algorithm is given in terms that require only a knowledge of elementary calculus and matrix algebra. As an example, the method is used to fit the logistic equation to a set of data.
The Accuracy of Pitfall Trapping for the Sand‐Beach Isopod Tylos Punctatus
Authors: Hayes Willis B.
Published: May 2006

A population of the isopod Tylos punctatus on a California beach was sampled by simultaneous coring and pitfall trapping. The traps showed a statistically significant bias against females, particularly gravid ones, and against juvenile isopods when compared to the cores. It is concluded that, for studying the population structure of this species, and perhaps others as well, pitfall traps produce samples that are too inaccurate to be useful.
Early Seedling Survival of Melilotus in Bluegrass Sod
Authors: Caruso John L.
Published: May 2006

Seeds of Melilotus alba and M. officinalis were sown in four different—sized openings in Canada bluegrass, a dominant of an old field. A relationship between seed germination and size of opening in the sod was not apparent but early seedling survival was correlated (P < .01) with size of opening, the larger openings yielding a greater number of viable seedlings. The areal extent of the dominant plant in the old field thus appears to regulate the number of sweetclover plants at an early stage of their life cycle.
Energy Exchange of White‐Tailed Deer, Western Minnesota
Authors: Moen Aaron N.
Published: May 2006

The energy exchange of white—tailed deer in an open field environment under clear winter skies at night is presented. Environmental radiation flux was measured with field instruments; radiation loss and surface temperature of deer were estimated with a simulator; heat loss by convection, evaporation, and warming ingested food was estimated from methods and data reported in the literature for other species. Metabolic heat production at three dietary levels, environmental radiation flux, and the heat loss at air temperatures from 0° to —40°C and wind velocities from ½ to 12 mph at deer height were integrated to provide a quantitative basis for determining the conditions under which thermal stress commences. Calculations are for fawns and does in a standing position in an open field under clear, nocturnal skies. The smaller deer reach a negative energy balance at air temperatures approaching 0°C and wind velocities of ½ to 1 mph if they are on a starvation diet. A maintenance to full diet enables them to withstand higher winds and lower temperatures. The larger deer reach a negative energy balance at air temperatures approaching 0°C and wind velocities of 3 mph when on a starvation diet. A full diet, however, enables them to withstand exposure to ½40°C temperatures and wind velocities of 8 mph. The behavior of the animals on the study area indicated that food rather than cover was of major importance in determining the locations where the deer remained during cold weather. Neither wind nor air temperatures to 35°C forced the deer into the protection of the woodlots. The energy balance predicted from the calculations indicated that these weather conditions should not cause a negative energy balance as long as the food supplied an adequate amount of energy and the deer could seek shelter from wind by moving behind a hill, shrub, or herbaceous vegetation in the open fields.
The Adaptive Significance of Colonial Nesting in the Brewer's Blackbird (Euphagus Cyanocephalus)
Authors: Horn Henry S.
Published: May 2006

The adaptive significance of colonial nesting for the Brewer's blackbird was studied in a sagebrush desert in eastern Washington. The colonies were small enough (5—30 pairs) to allow analysis of the behavior of individual birds and their reproductive success. The structural simplicity of the study site allowed easy access to the nests and accurate measurement of their spatial distribution. The effects of predation on breeding success were analyzed with respect to colony shape and the spatial distribution of the nests. On the study area the predation pattern favored more widely spaced nests in liner colonies, but more closely spaced nests in round colonies. I examined the role of colonial nesting in aiding the exploitation of a spatially and temporally variable food supply by taking food samples from nestling birds, measuring patterns of food availability, and observing the foraging patterns of the adult birds. An idealized model relates the spatial distribution of nests to the efficiency of individual exploitation of different distributions of food. In addition to conforming to the conditions of the model, Brewer's blackbirds take advantage of each other's foraging success. In conclude that colonial nesting in the Brewer's blackbird is primarily adaptive to the variable nature of their food supply.
Regulation of Animal Numbers: A Model Counter‐Example
Authors: Horn Henry S.
Published: May 2006

Data resembling either density dependent or density independent control of animal numbers may be generated by models that differ in degree but not in kind.
Mortality Patterns in Mammals
Authors: Caughley Graeme
Published: May 2006

Methods of obtaining life table data are outlined and the assumptions implicit in such treatment are defined. Most treatments assume a stationary are distribution, but published methods of testing the stationary nature of a single distribution are invalid. Samples from natural populations tend to be biased in the yound age classes and therefore, because it is least affected by bias, the mortality rate curve (qx) is the most efficient life table series for comparing the pattern of mortality with age in different populations. A life table and fecundity table are presented for females of the ungulate Hemitragus jemlahicus, based on a population sample that was first tested for bias. They give estimates of mean generation length as 5.4 yr, annual mortality rate as 0.25, and mean life expectancy at birth as 3.5 yr. The life table for Hemitragus is compared with those of Ovis aries, O. dalli, man, Rattus norvegicus, Micortus agrestis, and M. orcadensis to show that despite taxonomic and ecological differences the life table have common characteristics. This suggests the hypotheses that most mammalian species have life tables of a common form, and that the pattern of age—specific mortality within species assumes an approximately constant form irrespective of the proximate causes of mortality.
Some Factors Affecting Respiration of Periphyton Communities in Lotic Environments
Authors: McIntire C. David
Published: May 2006

Laboratory streams, a 509—liter respirometer chamber, and a Gilson differential respirometer were used to study factors influencing rates of periphyton respiration in lotic environments. Rates of respiration, expressed on an ash—free dry weight basis, determined for sections of intact communities in air—saturated water, varied between 0.8 mg O2/g hr at 7.2°C and 2.3 mg O2/g hr at 18.6°C for a community grown at 38 cm/sec current velocity, and between 0.4 mg O2/g hr at 7.2°C and 1.7 mg O2/g hr at 18.5°C for a community grown in a current of 9 cm/sec. These values were in good agreement with rates obtained manometrically in Warburg experiments and with values reported in the literature for various aquatic plants. The periphyton that developed in the swifter current exhibited a greater metabolic response to shaking than material grown in a slow current velocity. The fast—current community usually had a higher respiratory rate than the slow—current community. Rates of respiration in both communities decreased rapidly when the dissolved oxygen concentration was reduced below air saturation, indicating that the sessile lotic communities were particularly susceptible to oxygen exhaustion in the vicinity of the respiring cells. The enhancement of respiration by increasing O2 tension above air saturation was more pronounced at 5°C than at 13°C, and concentration of oxygen above air saturation had a greater effect on respiration when the flasks were not shaken.
Color Change and the Ecology of the Marine Isopod Idothea (Pentidothea) Montereyensis Maloney, 1933
Authors: Lee Welton L.
Published: May 2006

The isopod Idothea montereyensis lives on marine plants in the rocky intertidal zone on the west coast of North America. It occurs in red, green and brownish color varieties which usually match the color of the plant on which the isopod is found, and individuals are capable of undergoing color change when transferred to plants of another color. A population of Idothea montereyensis occurs on the eelgrass Phyllospadix scouleri which forms large beds at about the 0.0 tidal level; these animals are subjected to wave action which may be severe during the winter. Another population occurs inshore of the Phyllospadix on various species of red algae which grow in the more protected deeper pools and channels. During the year, when large numbers of young are released, there is a massive exchange of individuals between the Phyllospadix and the red algal populations. Young which cannot hold on in the exposed Phyllospadix beds are swept in to the inshore red algae, while, presumably as a result of population pressure, the adult animals on inshore red algae move out to the Phyllospadix beds. The result of these major population exchanges is clearly advantageous. Young which cannot hold on to the Phyllospadix are provided with a protected habitat for development and growth on the inshore red algae, whereas the adults moving to the Phyllospadix are provided with ample space and food in a region where they are not competing strongly with their own young for these things. It is the middle—sized and larger animals which survive through the winter on Phyllospadix; the summer young grow and develop in the protected inshore areas. The ability to change color may allow the animals to utilized for food and substrate a larger quantity and variety of intertidal plants, with greater safety from predators, than would be possible without color change. It may provide camouflage to animals within a relatively short time after the occurrence of highly advantageous shifts in habitat.
Ecology of Red Maple (Acer Rubrum L.) in a Massachusetts Upland Bog
Authors: Moizuk Georgene A. , Livingston Robert B.
Published: May 2006

Red maple, a typical component of wetland communities, develops to maturity in late stages of bog succession, as in the spruce—fur zone, but it never develops beyond the seedling stage on open or shrub—covered portions of the Sphagnum mat. Detailed studies were made of temperature conditions on the open mat and into the spruce—fir of a Massachusetts bog, together with chronological studies of marked red maple seedlings. Seedlings on the Sphagnum mat, where temperatures are low and the frost—free season is very short, were not killed by the late frosts, but survived for 2 years or more. Tests of germination and growth under flooded conditions showed that red maple grows best under conditions of constant flooding. In the flooding studies germination was equally good in both the normal bog medium, living Sphagnum, and spruce—fir humus, but subsequent development of the seedlings was far superior in the humus. Nutritional studies using the Sphagnum medium with nutritional supplements showed that red maple growth in the Sphagnum is limited by deficiencies of N and P. Plants low in K show little, if any, deficiency. It is concluded that the deficiency of N and P limits red maple development on the bog mat. Although seedlings may persist for 2 or move years they ultimately fail for they cannot obtain essential N and P from the sphagnum medium, even though they possess well—developed mycorrhizae.
Soil Factors and the Occurrence of Partridge Pea (Cassia Fasciculata Michx.) in Illinois
Authors: Foote L. E. , Jackobs J. A.
Published: May 2006

Partridge pea frequently occurs on non—stable sites and in Illinois occurs most often on silty clay loam soils. There was no tendency to occur on sandy sites as has been previously reported. Partridge pea occurs on soils with a wide range of pH values and on sites with both low and high phosphorus values. Low phosphorus values predominate in both the slowly and readily available forms. Partridge pea stands generally occur on soils with very high levels of available potassium but also occur on sites quite deficient in potassium. Total, mineral, and extractable calcium (measured as CaO) were present in partridge pea site soils in amounts ranging from .40 to 2.55%, .22 to 1.31%, and .03 to 1.27%, respectively. Soils with partridge peas growing on them have a wide range in total nitrogen content but low values less than .181% predominate. These soils also generally have a low rate of nitrate production. Low nitrate production and/or low levels of available phosphorus may restrict the growth of other species on sites where C. fasciculata occurs. Total nitrogen and nitrate production, however, were not related to the amount of phosphorus. Subsoil clay content did not seem to be a factor in partridge pea stand occurrence. The species' ability to grow under some adverse conditions and on non—stable sites, including eroding areas, indicates that it is a species which might have a use similar to Korean lespedeza (Lespedeza stipulacea L.).
Matrix Cluster Analysis of Montane Forest Vegetation of the Oregon Cascades
Authors: West Neil E.
Published: May 2006

Cluster analyses of matrices of coefficients of similarity have yielded dendrograms graphically illustrating synecological affinities in montane forest vegetation on the east flank of the central Oregon Cascades. Vegetation patterns of more continuous variability then unit—association have been divided into operational synecological units. Knowledge of areal representation and environmental gradients associated with stands allows theoretical interpretations on vegetation distribution as well as extension of the information for land management.
Survival of Alaskan Woodfrog (Rana Sylvatica) Larvae
Authors: Herreid Clyde F. , Kinney Stephen
Published: May 2006

Data were collected on the average number of eggs per egg mass, the percentage of eggs successfully fertilized, and early mortality within the egg mass. A dilute solution of neutral red was used to mark tadpoles for estimates of population size. An average of 96% of the eggs and larvae died in four ponds before metamorphosis was complete.
Energy Dynamics of Colorado Pikas
Authors: Johnson Donald R. , Maxwell Marvin H.
Published: May 2006

Like other lagomorphs, pikas reingest fecal matter which is high in protein content and energy value (5.2 kcal/g). The plant food stored in haypiles is low in caloric content (4.5 kcal/g) but some populations utilize energy—rich aspen bark (5.2 kcal/g) during the winter and spring months. The daily energy intake of a non—gravid, non—lactating, adult pika (171 g) is estimated at 54.8 kcal of which 68% is assimilated. Food intake, and perhaps feces reingestion, is increased during pregnancy and lactation.