bluuebunny/crossref_metadata_2025 huggingface dataset:
Transfer Studies of Ecologic and Genetic Variation in the American Smelt
Authors: Rupp Robert S. , Redmond Malcolm A.
Published: May 2006

Introductions of American smelts, Osmerus mordax, from six established populations into eight new environments were made in Maine in 1957—62 to determine which characteristics of the parent populations would be altered by transfer to the new environments and which would remain unaltered. Four of the host lakes had not contained smelts previously, three had contained smelts which were removed by rotenone, and one is thought to have contained a smelt population which disappeared 4 or 5 years before the experimental transfer. In several cases the growth rates, lengths, and longevities attained by smelts changed greatly with change in their environment. The time of the spawning season for one stock of smelts remained unaltered following transfer to an environment where the previous smelt population routinely had spawned much later. In one case smelts hatched from eggs of a stream—spawning population adapted immediately to the shore—spawning habit in a host lake where tributaries are absent. The success of smelts in the various new environments appeared to depend mostly upon the intensity of interspecific competition and other biotic factors, as with most fishes.
The Distributional Pattern of Benthic Invertebrates of the Continental Shelf off North Carolina
Authors: Cerame-Vivas M. J. , Gray I. E.
Published: May 2006

The benthic macroinvertebrate fauna of the continental shelf off North Carolina may be divided into three species assemblages, each occupying a given area and corresponding to three biogeographic provinces. North of Cape Hatteras, in a wedge having its narrow end near Diamond Shoals, the fauna and the environment correspond to the Virginian Province. South of Cape Hatteras, over roughly the inshore half of the continental shelf, the Carolinian Province is represented. Offshore from these two provinces, over the outer half of the shelf, lies the Tropical Province. Conclusions regarding these faunas and these provinces are based on dredging collections including 211 species representing 16 classes from 6 phyla. One—fourth of the total number of species are new distribution records for the coasts of North Carolina.
Water Budget of a Forest Damaged by Ionizing Radiation
Authors: Reiners W. A. , Woodwell G. M.
Published: May 2006

Cumulative evapotranspiration, measured by soil—moisture changs over a growing season, was only slightly greater in intact zones of a gamma—irradiated oak—pine forest than in severely damaged zones. In the central part of this forest where exposures exceeded 160 R/day and only scattered herbaceous plants survived, cumulative evapotranspiration was about 85% that of the intact forest. Rates of evapotranspiration increased along the gradient of decreasing radiation damage during the first half of the growing season, but were roughly equal at all exposures during a drought in the latter half of the season. Differences in rates of evapotranspiration were detectable at chronic exposures of 11.5 R/day, where the dominants retained 50% of their foliage.
Growth and Reproduction of Eragrostis Tenella in Pastures on the Upper Gangetic Plain
Authors: Sant Harshwardhan R.
Published: May 2006

The reproductive capacity and growth forms of Eragrostis tenella Roem et Schult are directly influenced by the intensity and duration of light, the amount of exchangeable calcium in the soil, and particularly by grazing. Although the species grows under trees, it achieves its greatest height, spread, fresh weight, and seed output in full sunlight. Growth pattern is irregular in response to calcium, but maximum seed production is achieved in soil containing about 14.14 meq% exchangeable calcium. Grazing or clipping, far from diminishing the seed supply, seems actually to increase the total seed output, since frequently clipped plants and over—grazed fields show the greatest reproductive capacity, a fact which is significant for either the control or deliberate encouragement of E. tenella.
An Improved Method of Obtaining Density from Line‐Transect Data
Authors: Strong Charles W.
Published: May 2006

Measurements are taken perpendicular to the transect across the greatest extent of each intercepted plant. The sum of the reciprocals of these measurements is multiplied by the desired unit—area and divided by the length of the transect to obtain the density statistic. The relationship of this method to that of McIntyre (1953) is discussed, and the stratified random sampling pattern is suggested in preference to a single long transect.
Movement of the Crawfish Faxonella Clypeata in a Linear Maze
Authors: Mobberly William C. , Owens Jerald V.
Published: May 2006

Dispersal of the crawfish Fazonella clypeata in a linear environment does not show a density—dependent relationship in populations of 1, 5, 10, 20, and 30 animals. Crawfish without chelae moved approximately the same distance per time period as intact animals. Animals with antennae or eyestalks absent moved less than intact animals. The control of locomotion by a hormone originating in the eyestalk possibly explains why eyestalkless animals had very little movement. The means for the dispersal of intact male and female groups were not significantly different from each other. The innate tendency toward dispersal may be found in some crawfish species demonstrating intra—specific aggressive behavior.
Some Factors Affecting Aggregation of Isotoma Viridis, Bourlet and Arion Fasciatus, Nilsson
Authors: Jensen Paul , Corbin Kendall W.
Published: May 2006

A number of kinds of sampling boards were used to test the effect of different microclimates on the state of aggregation of various prairie cryptozoa. White boards had significantly more Isotoma viridis (Collembola), Arion fasciatus (a slug) and a general category of mites than did black boards. The collembolan was more abundant under large than small boards just about in proportion to the differences in perimeters of the two boards. The collembolan also had a definite diurnal cycle. Actual microclimatic differences could not be demonstrated.
Light Control of Aquatic Insect Activity and Drift
Authors: Bishop John E.
Published: May 2006

Investigations on aquatic insect activity, measured as drift in an artificial stream system with rigid light and temperature conditions, demonstrated a light—controlled, labile, exogenously—mediated activity rhythm. A threshold value for light, incident at the water surface, which when decreased led to high drift rates, and when increased suppressed activity, was determined to lie between 10—3 and 10—4 ft—c (10—2 and 10—3 lux). Preliminary experiments showed variations in wavelength to have little effect on the activity patterns of the insects.
Association of Species and Their Relationship to Microtopography Within Old Fields
Authors: Zedler Joy B. , Zedler Paul H.
Published: May 2006

The relationship of vegetational pattern to edaphic environment was examined within the old—field—prairie ecotone of a central Wisconsin drained marsh. Examination of several soil factors established significant correlations between the elevation gradient (with a range of 1.5 m) and organic matter content and moisture. Several species showed definite peaks of frequency and density across the elevation gradient with the invading prairie species predominating on the low ridges and wetland species largely restricted to depressions. Old—field species, such as Poa pratensis and Linaria vulgaris, were present on all topographic positions but appeared to be yielding to competition with the above species groups at the extremes of the elevation gradient. Pattern of species groups was further investigated by the use of normal association analysis. Environmental differences were tested between the resulting subdivisions of this analysis; this further documented the influence of microtopography on the distribution of the vegetation. In addition, organic matter levels were shown to be important in species distribution where differences in elevation were not in control. Normal association analysis and environmental correlation are considered in regard to the continual nature of plant distribution.
Habitat Specificity, Speciation, and Species Density in Australian Desert Lizards
Authors: Pianka Eric R.
Published: May 2006

From data demonstrating habitat specificity, it is concluded that Australian desert lizards recognize more habitats than North American desert lizards. The large amount of environmental heterogeneity and intimate mixing of habitats in Australia allow many more lizard species to coexist there than in North America. An interpretive hypothesis for lizard speciation by means or habitats fluctuating in time and space is proposed.
Vegetation and Soil Development on a Recently Glaciated Area Near Mount Robson, British Columbia
Authors: Tisdale E. W. , Fosberg M. A. , Poulton C. E.
Published: May 2006

Rapid retreat of the Robson Glacier since 1783 has produced a series of moraines well suited for study of vegetation and soil development. The terminal and five recessional moraines ranging in age from 180 to 50 years were suited in August 1963 in continuation of earlier work by W. S. Cooper. Vegetation development shows early dominance of Hedysarum and Dryas, followed by Salix, Arctostaphylos rubra, and other shrubs. Tress enter the stand early, but are largely confined to one species, Picea engelmanni. The vegetation of the two oldest moraines bears a superficial resemblance to the mature forest of the region, but differs greatly in floristic composition and structure. Soil Formation ranges from virtually none on the youngest moriane to a rudimentary podsolic B horizon on the oldest recessional moriane Accumulation of soil nitrogen appears to be slow, despite the existence of root nodules on Dryas octopetala, D. drummondii, and Hedysarum mackenzii.
Soil‐Site Characteristics and Occurrence of Sugar Maple Canker in Pennsylvania
Authors: Ward W. W. , Berglund J. V. , Borden F. Y.
Published: May 2006

The occurrence and severity of an annual canker disease among sugar maples, Acer saccharum Marsh., were studies with respect to the soil. topographic, three, and stand c characteristics of maple—growing sites in the nonglaciated plateau and mountain region of Pennsylvania. Symmetric correlation, multiple regression, and factor analytic procedures were used in interpreting approximately 100 variables, or interactions among variables, measured on each of 62 plots. The analyses indicated that occurrence and severity of cankering was most closely associated with those characteristics peculiar to slowly permeable soils. On the heavily cankered plots soils were relatively shallow to an impervious layer, and the A horizons contained a greater clay content and more pore space. A decrease in the percentage of the total root count in the surface 6 inches of these soils indicated that the surface layer was not particularly favorable for the development and survival of roots. The lower vigor of sugar maples growing on such sites was significantly correlated with greater canker incidence.
Use of a Vacuum‐Clipper for Harvesting Herbage
Authors: Van Dyne George M.
Published: May 2006

A vacuum—clipper for harvesting low—growing herbage is described. Some litter and soil are picked up by this device when harvesting herbage, and equations were developed to predict net herbage weight from gross herbage weight. About 90% of the variation in net herbage weight accounted for by variations in gross herbage weight under good conditions. The vacuum—clipper increased the speed of fieldwork up to tenfold under difficult working conditions on winter range. The influence was determined off relative variations of clipping time in the field and variations in laboratory separation time upon the optimum ratio of plots clipped to plots separated. In this study, the optimum ratio of plots clipped to plots clipped and separated varied from five to eight.
Soil Physical Properties in Relation to Plant Community Patterns in the Shadscale Zone of Northwestern Utah
Authors: Mitchell John E. , West Neil E. , Miller Raymond W.
Published: May 2006

Physical properties of soils associated with monospecific communities of Eurotia lanata and Atriplex confertifolia were studied to determine their possible influence on the vegetation pattern. Complete homogeneity of all properties examined indicated a lack of genetic soil variability as a cause of community differentiation.
Sensors for Measuring Light Available for Photosynthesis
Authors: Federer C. A. , Tanner C. B.
Published: May 2006

Consideration of energy absorption by photosynthesis indicates that photon flux density in the 400— to 700—nm wavelength range is best measure of light available for photosynthesis. When light spectral distribution changes, deviation of sensor spectral response from the photon response introduces errors in measurements. These errors are calculated for several sensors and spectral distributions. A selenium photovoltaic cell with a Written 85C filter is a simple system which closely approximates the photon response.
Circadian Activity Pattern with Two Peaks
Authors: Aschoff Jurgen
Published: May 2006

The 24—hr rhythms of behavior and other physiological functions are based upon an endogenous self—sustained oscillation. This is proven by experiments in which animals, kept in constant conditions, show a freerunning circadian period which deviates to a certain degree from that of the earth's rotation. The 24—hr rhythms of activity are furthermore characterized by typical patterns of which the one with two peaks in one period is most common. Under natural conditions, these two peaks of activity are often closely related to specific stimuli in the environment; e.g. to dawn and dusk. They have therefore been described as being directly caused by the environment. However, one may consider not only the circadian period but also the pattern part of an endogenous system. This hypothesis has been tested in experiments with finches. The results are: 1) Birds kept in artificial light—dark cycles show the same two—peak pattern either in cycles with interposed twilight or in cycles with rectangular changes between light and dark, 2) Under constant conditions, the second peak may disappear; but more often, it either remains or becomes more pronounced tan under conditions of a light—dark cycle. 3) With different levels of constant intensity of illumination, the birds show different circadian periods and different durations of activity; under those conditions, the two peaks keep the same proportional relationship to the activity time regardless of its duration. It is concluded that the basic two—peak pattern of locomotor activity is a persistent property of the circadian oscillating system.
Influences of Seasonal Factors on the Activity Onset of the House Finch
Authors: Enright J. T.
Published: May 2006

In laboratory experiments, cold environmental temperature (2°C) caused male House Finches to awaken later, relative to "dawn," than warm temperatures (20°C) when day lengths (hours of light per cycle) were held constant. When temperature was held constant, greater day lengths also caused later awakening relative to "dawn." Extrapolation of these observations to field conditions suggests that seasonal changes in average temperature and day length may exert opposite influences on awakening time: the long days of spring would induce minimal "anticipation" of dawn, while the warmer temperatures would tend to counteract this influence. Additional circumstantial evidence suggests that reproductive maturity may also cause earlier awakening, relative to dawn, day length and temperature held constant.
Environmental Modification of Habitat Selection in Adult Damselflies
Authors: Johnson Clifford
Published: May 2006

The adult habitat preferences of four damselfly species were analysed to determine whether their choices could be modified by environmental conditions at the site of adult emergence. Four species occurring in southwestern New Mexico were studies. Hetaerina americana, Hyponeura lugens, and Ischnura demorsa prefer lotic waters while I. damula favors lentic conditions. Last instar larvae of each species were transferred from their favored habitat so upon emergence the adult would be initially confronted with an environment unlike that preferred by the species. Such larvae composed the experimental group for each species. Control groups provided observations on habitat preference from individuals known to have emerged from the favored habitats. Chi—square analysis indicates a significant modification of behavior occurred in all four experimental groups. Heritability of habitat selection is not sufficiently understood for use in evolutionary studies.
The Detection of Regulation in Animal Populations
Authors: St. Amant J. L. S.
Published: May 2006

If the detection of regulation in a population is attempted by taking a linear regression of log population density against log previous population density, the slope, b, of the line thus obtained is supposed to be less than 1 only if regulatory tendencies are present in the population. However, a nonregulated population will probably give similar values of b < 1 provided only that the successive differences between log population values are not all the same. This spurious indication of regulation becomes more likely and more apparent if the number of census points is small, or if the variation in numbers of animals is large compared to the total population change over the period measured. Complexities which are almost certain to occur in natural situations and which make satisfactory models for regulated and nonregulated populations intractable or indistinguishable probably require that investigations of regulation either use more detailed information that census data alone, or that they adopt an experimental approach by testing for convergence of altered densities of subpopulations.
Adult Behavior and Population Structure in Erebia Epipsodea (Lepidoptera: Satyrinae)
Authors: Brussard Peter F. , Ehrlich Paul R.
Published: May 2006

Data are presented on the effects of air temperature, wind, and solar radiation on the flight activity of the alpine butterfly Erebia epipsodea, a species which occurs, at least in montane central Colorado, in large, effectively panmictic populations which are continuously distributed over wide areas. Thermal—flight relationships in the adults are well adapted to the often marginal weather conditions prevalent in this locality during the flight season. Other aspects of flight behavior which may serve an epideictic function and insure greater spacing of males than would otherwise occur are also reported and discussed.
Root‐Shoot Ratios on Native Forest Herbs and Zea Mays at Different Soil‐Moisture Levels
Authors: Struik Gwendolyn J. , Bray J. R.
Published: May 2006

Seven forest herbs had a higher below—ground dry matter production in a dry forest than in a mesic or moist forest. Zea mays had a higher relative below—ground production in a droughty portion of a field than in a non—droughty.Root/shoot ratios tend to increase with increasing xericness of the habitat.
Pokeweed Seed Germination: Effects of Environment, Stratification, and Chemical Growth Regulators
Authors: Farmer R. E. , Hall Geraldine C.
Published: May 2006

Pokeweed seed exhibits a stratification requirement for dark germination. While unstratified seed germination in light, stratification increased germination speed and lowered the temperature threshold for light germination. Variation in germination characteristics of seed from individual plants was broad, and a portion of seed from each plant had a light requirement which stratification did not replace. Gibberellin—induced dark germination was observed only after seed were treated with concentrated sulfuric acid for five minutes. GA7 was more effective than GA3 in stimulating germination. Abscisic acid partially inhibited germination of stratified seed in light and completely inhibited it in dark.
Disappearance of Plant Material Under a Winter Snow Cover
Authors: Bleak Alvin T.
Published: May 2006

Disappearance of plant material from fine—mesh nylon bags occurred during the late fall, winter, or early spring when mountain ranges in central Utah are generally snow covered. Quantitative loss of matter from leaves and stems of two grasses and two broad—leaved forbs was mostly attributed to decomposition by fungi and bacteria and to leaching. Loss of material from bags in direct contact with the snow cover during two consecutive winter periods averaged 30% for the relatively coarse Agropyron trachycaulum, 39% for Bromus inermis, 48% for Lupinus alpestris, and 51% for Mertensia arizonica var, leonardi. The ratio of leaf to stem weights decreased with all aspects.
A Fine Wire Psychrometer for Measurement of Humidity in the Vegetation Layer
Authors: Caldwell Martyn M. , Caldwell Marie Lynn
Published: May 2006

A small, compact, fine wire thermocouple psychrometer was tested under controlled conditions in climatized wind tunnels. The unit was found to be free of radiation errors and fully ventilated at only 1 cm sec—1. Because of the simple construction and favorable response characteristics, this psychrometer is recommended for measurement of humidity in the vegetation layer.
Southern Mixed Hardwood Forest in the Virginia Coastal Plain
Authors: Ware Stewart A.
Published: May 2006

The more mature portions of the College Woods at Williamsburg, Virginia, were analyzed and compared with the southern mixed hardwood forest (SMHF) described by Quarterman and Keever (1962). In order of decreasing importance values the dominants in the three layer were Quercus alba, Liriodendron tulipifera, Pinus taeda, Fagus grandifolia, Quercus falcata, and Acer rubrum. Cornus florida, Acer rubrum, and Ilex opaca were the most important understory tree species, with Myrica cerifera and Euonymus americana as the abundant shrub species. The forest exhibited a strong relationship to the SMHF. Ten of the SMHF group I overstory species were present, contributing 62% of the total tree layer importance value; those missing (Quercus laurifolia and Magnolia grandiflora) are very rare so far north. The sampled community differs from the SMHF in the high importance of Liriodendron and Acer rubrum. These species may generally be more important in the north—eastern portion of the SMHF.
A Polyurethane Stemflow Collector for Trees and Shrubs
Authors: Likens Gene E. , Eaton John E.
Published: May 2006

A collar of polyurethane foam was developed for collecting stemflow from hardwood trees. This collector is economical, chemically inert, and easy to install on stems of various textures, sizes, and shapes.
Seasonal Basal Growth Area as an Expression of Competition in Northern Hardwoods
Authors: Winget C. H. , Kozlowski T. T.
Published: May 2006

A 2—year study of basal area change of six tree species was conducted with vernier growth bands in the northern conifer—hardwood sub—formation in north—central Wisconsin. Curves of basal area change per unit of stem circumference satisfactorily expressed differences in initiation of stem expansion, rate and duration of growth, and winter shrinkage for various species and crown classes. Seasonal growth for all species and crown classes was represented by a sigmoid curve beginning with a short period of slow basal area increase in early spring and ending with a longer period of declining growth rates leading to relative stability through late summer and fall. Winter shrinkage, most marked in basswood, began in early winter and often exceeded total summer growth by midwinter. Recovery was complete by early spring. Hemlock began rapid growth earlier and ceased growth later than any other species studied. Basswood began and ceased growth later than sugar maple, white and yellow birch, and trembling aspen. Timing of rapid growth initiation was somewhat affected by weather and tree condition. The decreasing order of vigor in competition of the major species was (1) sugar maple, (2) hemlock, and (3) yellow birch and basswood. Differences in amounts of cambial growth of species and crown classes were traceable to differences in both rate and duration of growth. Delay of rapid stem expansion in lower crown classes was much less marked than in lower crown classes of pure coniferous stands studied elsewhere, probably because of less canopy shading in spring. Differences in times of cessation of growth of crown classes were more marked, with the most suppressed trees ceasing growth earliest. Effects of particular stand conditions were most evident in growth of suppressed crown classes.
Comparative Photosynthetic and Respiratory Responses to Temperature and Light by Pseudotsuga Menziesii Var. Menziesii and Var. Glauca Seedlings
Authors: Krueger Kenneth W. , Ferrell William K.
Published: May 2006

Douglas—fir seedlings of the geographic varieties menziesii and glauca were grown from seed collection from southern Vancouver Island, B. C., and western Montana. Photosynthetic and respiratory rates were compared for a range of temperatures, light intensities, and under constant high—intensity illumination. Maximum apparent photosynthesis occurred near temperatures of 20 degrees—25 degrees C for 35— and 65—day—old seedlings. Seedlings from Vancouver Island had significantly higher rates of photosynthesis than seedlings from Montana at certain temperatures at both ages. Respiratory rates of 35—day—old seedlings from Vancouver Island were significantly higher at 20 degrees—35 degrees C than those from Montana, but at 65 days of age only at 15 degrees and 40 degrees C. Seedlings from Montana required more light to reach the compensation point at 20 degrees C, and photosynthesized less at light intensities of 200 to 1,000 ft—c than did Vancouver Islands seedlings. Saturation intensity for seedlings from both varieties was near 3,000 ft—c. After 11 hours of illumination at 10,000 ft—c, the photosynthetic rate of Vancouver Island seedlings had declined from the initial rate significantly more than had Montana seedlings. Observed differences in photosynthesis and respiration between young seedlings from these two regions often decrease as seedlings become slightly older. Comparison of two Vancouver Island and two Montana sources showed that differences between seedlings of the same geographic variety can be greater than between seedlings of the two varieties.
Paleoecological Studies of Potato Lake and Its Environs
Authors: Whiteside Melbourne C.
Published: May 2006

A 286—cm core of sediments was taken from the center of Potato Lake, Coconino Co., Arizona. Pollen, chemical, and physical analyses were made on the sediment. Pluvial conditions, evidenced by high PAP percentages, exist until approximately the 120—cm level of the core; at this level a major change in pollen types occurs with pine assuming dominance. A core section at 142—172 cm was dated at 14,000 plus or minus 300 BP. Post—pluvial climate, as reflected by the pollen diagram, was fairly stable. Loss on ignition at 550 degrees C of the sediment material implies that eutrophication of Potato Lake began at the close of the pluvial. Variations of iron, manganese, and calcium may be explained by lake succession from oligotrophic to eutrophic conditions
Ornithocoprophilous Endemism in Pacific Basin Angiosperms
Authors: Ornduff Robert
Published: May 2006

Evidence is presented for the existence of genetically distinct races or taxa of angiosperms which are restricted to deposits of seabird guana occurring on islands in the Pacific basin. Various lines of evidence suggest that these ornithocoprophilous plants can be considered somewhat weedy nitrophilous halophytes. Many of the morphological characters by which they are distinguished from their nearest non—coprophilous relatives seem to be adaptively related to the unusual nature of their habitat. Other not obviously adaptive characters may have become fixed by genetic drift in these small populations. A possible mode of origin of guano endemism is proposed.
The Frequency and Magnitude of Intraspecific Parasitism in Triatoma Sanguisuga (Leconte) (Hemiptera)
Authors: Hays Kirby L.
Published: May 2006

Triatoma sanguisuga (Leconte) will feed upon their own species in the labortory. Some of these insects passed from the first to the fourth instar without any nourishment except haemolymph from other bugs. One insect was maintained 556 days on haemolymph along. All stages of the insect, including adults, paratized each other. It required 17 to 24 mg of haemolymph taken in 5 to 8 feedings for the insect to pass through the second instar and 57 to 65 mg of haemolymph taken in 8 to 13 feedings to pass through the third instar. One nymph took 106 mg of haemolymph in the fourth instar, but it did not molt to the fifth instar. Trypanosoma cruzi was not passed from infected to uninfected insects during parasitism.
Multivariate Procedures in an Investigation of Vegetation and Soil Relations of Two Beech Woodlands, Cotswold Hills, England
Authors: Barkham John P. , Norris John M.
Published: May 2006

Vegetation and soil systems in two beechwoods were examined by measurements of variables at the same sites. Principal components analysis was used to generate hypotheses about the relationship between vegetation and soil which were tested by simple correlation of components and variables. Further information explaining the variation of the vegetation system was obtained by simple correlation with environmental data. Canonical correlation was used to relate the variables of the two systems directly and all together. The primary relationship between vegetation and soil was found to be in terms of soil—moisture variation. However, light variation associated with changing canopy quantity and slope variation were found also to affect both systems particularly through their effect on soil moisture.
Dietary Similarity of Some Primary Consumers
Authors: Hansen R. M. , Ueckert D. N.
Published: May 2006

The dry—weight composition of the diets of richardson ground squirrels (Citellus richardsonii), mormon crickets (Anabrus simplex), and six species of grasshoppers (Xanthippus corallipes, Circotettix rabula, Aeropedellus clavatus, Melanoplus infantalis, Melanoplus bruneri, and Melanoplus alpinus), collected at Prairie Divide, Colorado, was determined. Many food plants were shared by these herbivores. Vetch (Astragalus spp.), sandwort (Arenaria fendleri), fungi, parry oatgrass (Danthonia parryi), bluegrass (Poa spp.), fringed sagebrush (Artemisia frigida), dandelion (Taraxacum officinale), and sedge (Carex spp.) were major foods. Bluegrasses, vetch, and sandwort would probably become limiting if population peaks of several of these herbivores coincided. The ranking of the food niches of these herbivores from specialized to generalized based on mean indices of dietary similarities is X. corallipes, A. clavatus, C. rabula, M. alpinus, A. simplex, M. bruneri, C. richardsonii, and M. infantalis. Males ate fewer species of food plants than females of the same orthopteran species, and the diets of males and females of the same orthopteran species were occasionally less similar than were the overall diets of different species on the same date.
Ecological Investigations of Thlaspi Alpestre L. Along an Elevational Gradient in the Central Rocky Mountains
Authors: Rochow Theodore F.
Published: May 2006

Plants of Thlaspi alpestre L. (Cruciferae) from a high elevation population in the Medicine Bow Range of Wyoming were genetically dwarfed. These plants broke dormancy and entered dormancy more rapidly than a subalpine population from the same area. The overwintering of seed of T. alpestre before germination in the field may be caused by properties of the seed coat. The distribution of T. alpestre at high elevations is limited in part by a low reproductive ability; at low elevations, competition and infection by pathogens may shorten the life span of T. alpestre and limit its distribution.
Mechanism of Desiccation Damage of Conifers Wintering in Soil‐Frozen Areas
Authors: Sakai A.
Published: May 2006

In 1966—67 in the eastern part of Hokkaido, where severe cold weather and a dry state prevailed throughout the winter, most young conifers, especially those wintering on the southern slopes, were seriously damaged. Minimum temperature was about —30°C, and soil temperature at 10—cm depth even on the southern slopes remained below zero for 3.5 months. Soil was frozen down to about 40 cm. Temperatures of stems and leaves of young conifers wintering on the southern and northern slopes rose to about 17° and 9°C, respectively, in midday and remained unfrozen for about 6 and 2 hr, respectively, in the daytime. Under these conditions, the conifers wintering on the southern slopes were intensely dehydrated towards the end of February. In most damaged trees, browning was observed on the stem bark. Trees in which desiccation damage was artificially induced exhibited nearly the same browning as that observed in trees suffering damage under natural conditions. Stems and leaves of young Sakhalin fir and Ezo spruce could stand freezing in winter below —50C, and white pine and American arborvitate which sustained damage seriously under natural conditions also survived freezing below —120°C. Young conifers wintering in frozen soil were damaged by dehydration resulting from a combination of freezing of soil and exposure to sunshine.
Comparative Autecology of the Lizard Cnemidophorus Tigris in Different Parts of Its Georgraphic Range
Authors: Pianka Eric R.
Published: May 2006

I studied various aspects of the life history of Cnemidophorus tigris over much of its geographic range, from southern Idaho through southern Arizona and into northern Sonora. In the northern parts of its range, Cnemidophorus usually emerge from hibernation in May, and most adults aestivate during the midsummer months, but in the south the animals are active from April through late August. The seasonal period of activity is therefore considerably shorter in the north. Daily periods of activity are of similar duration from north to south, although the time of emergence tends to be later on northern areas. There is a significant positive correlation between estimated abundance and the total precipitation during the last 5 years, suggesting that the abundance of this species is determined by food supply. There is a latitudinal cline in the mean body temperature of active lizards, with northern populations being active at lower air and body temperature. Whereas termites constitute the major food of southern lizards, beetles and grasshoppers are the primary food of northern lizards. Some seasonal dietary trends are described. The numbers and biomass of predatory lizards, birds, and snakes increase from north to south; correlated with this is a latitudinal increase in the percentage of lizards with broken regenerated tails. Hence there is probably greater predation on southern lizards. The length of fat bodies in C. tigris is not correlated with latitude but shows an inverse correlation with the long—term average annual precipitation. It is suggested that lizards from less productive areas must allow themselves a greater margin of safety due to the more probable occurrence of drought. Northern lizards breed only once during the short northern season but lay significantly larger clutches than southern lizards, which lay at least two clutches annually. Clutch size appears to be flexible in response to feeding conditions; in one study area with a low long—term mean precipitation, females laid larger clutches during the second year, after supranormal rainfall. There is a significant correlation between mean number of eggs per clutch and the deviation of the short term (last 5 years) mean precipitation from the long—term mean precipitation. A number of facts suggest that there was a decided population "crash" on one study area during the period of study. Competition is briefly discussed and it is suggested that if there is any latitudinal trend, it is most likely in the direction of greater competition among southern lizards. In the conclusions, I suggest that the ecological challenges facing the northern populations are primarily physical, largely climatic ones, biotic interactions (particularly predation) assume relatively greater importance to southern lizards.
Copper Concentrations in the High‐Beach Isopod Tylos Punctatus
Authors: Hayes Willis B.
Published: May 2006

The beach isopod Tylos punctatus occupies a high—intertidal habitat, but has a hepatopancreatic copper concentration similar to that of more marine isopods. Considerable intraspecific variation was noted, however, and the differences may not be significant. The copper—retention gradient from marine to terrestrial isopods is discussed in relation to variations in the inorganic sulfate content of the environment, and an experiment is proposed.
The Ecological Efficiency of Consumer Populations
Authors: Turner Frederick B.
Published: May 2006

It has been suggested that the ecological efficiencies (or gross efficiencies of yield to ingestion) of steady—state consumer populations may be a constant 8—12%. It is now argued that, on the basis of available data, the ecological efficiency of populations of homeothermic animals cannot exceed 2—3%.
Engelmann Spruce (Picea Engelmannii Engel.) at Its Upper Limits on the Front Range, Colorado
Authors: Wardle Peter
Published: May 2006

Engelmann spruce is the dominant tree at timberline in the Front Range at approximately 3,350 m elevation; it occurs as krummholz in the forest—tundra ecotone up to about 3,500 m, and occasional individuals are found in the tundra up to 3,730 m. Temperatures decrease with increasing altitude above timberline, whereas wind velocity increases, especially during winter. Winter snow is deeper and persists longer in the forest than in the krummholz above, its depth in the latter tending to remain constant once the lower portions of the plants are packed. Soil temperatures fluctuate widely beneath tundra vegetation in the neighborhood of krummholz plants, whereas under forest variations are small and there is a prolonged period in spring when they remain within 0.6°C (1°F) of freezing point. Krummholz growth forms of spruce arise through death of needles and shoots exposed to the prevailing westerly winds. Even in the summer young exposed needles tend to be somewhat chlorotic, and many show lesions. In winter windward needles dry out, become bleached, and are eventually shed. Certain needles, instead of becoming bleached during winter, turn brown and dry out in early spring. In krummholz, even within a single shoot, sharply contrasting differences develop in winter between leeward needles that show only small seasonal decreases in water content, and windward needles that dry out and die. Desiccation is usually confined to krummholz, mainly affected small needles on stunted shoots and the distal needles of long, robust shoots, but in the winter of 1961—62, following a cold, wet September, it extended to leading shoots of saplings below timberline. Replenishment of water in needles during winter is probably from water stored in sapwood above the snow pack, since sapwood beneath the snow pack remains frozen in both forest and krummholz. Late—lying snow delays the spring growth of seedlings below timberline, but they occur even where snow persists until late in June. Above timberline, spruce seems to be less tolerant of late—lying snow. It is concluded that though the position of timberline is correlated with summer temperatures, dry winter winds are the immediate, though probably not the ultimate, cause of the krummholz growth forms in the forest—tundra ecotone.
Relation of Body Size to Food Intake, Oxygen Consumption, and Trace Element Metabolism in Forest Floor Arthropods
Authors: Reichle David
Published: May 2006

Food intake and respiratory heat loss are the major pathways of energy flow through animal communities. In certain cases flow rates can be estimated for the total population from selected measurements of individual species. Metabolic parameters (Y) of arthropods from the floor of a Libriodendron tulipifera forest were correlated with size (X) of species: Y = aXb. This power function relationship is similar to the "active surface area" hypthesis of animal metabolism. The species examined ranged in size from 2.1 mg to 1.6 g live weight, and spanned a diversity of food habits and taxonomic categories. Food consumption was proportional to the 0.68 power of body weight. Metabolism (μl O2 hr—1) varied with the 0.84 power of body weight, while metabolic rate (μl O2 g—1 hr—1) was inversely proportional (b = —0.16) to body size. Within closely related species, 137Cs turnover rates were closely correlated with metabolic rates. These rates varied with temperature and followed a Q10 of approximately two. By applying appropriate temperature corrections, body size relations can be used to estimate food intake and metabolism of species in their natural habitats. Radiotracers also may permit measurement of temporal fluctuations in metabolism resulting from activity in the field.
Relationships Between Saturation Deficit and The Survival and Distribution of Terrestrial Isopods
Authors: White Joseph J. , Zar Jerrold H.
Published: May 2006

Equations are presented (1) to determine the specific gravity of a glycerol—water solution necessary to maintain a desired relative humidity in a small experimental chamber and (2) to predict the relative humidity which would be maintained by a given glycerol—water solution. The woodlouse, Tracheoniscus rathkei Brandt can survive its normal life span only if exposed to saturation deficits very near zero. In this species, as well as in 8 previously reported species, survival time is inversely related to saturation deficit rather than simply to the relative humidity. When equations for this relationship are compared for the various species, it is observed that those species whose survival times are decreased most by increases in saturation deficit are those which are normally found in wetter habitats.
Life‐History Studies on Lestes Eurinus Say (Odonata)
Authors: Lutz Paul E.
Published: May 2006

Extensive field studies in 1965—1966 in a small woodland impoundment in Guilford County, North Carolina indicated the duration of the life cycle of Lestes eurinus was about 1 yr. Rapid larval growth occurred from July to mid—October with development being arrested by late October. The population overwintered in the three stages preceding the ultimate instar. Larval growth was resumed in March and progressed rapidly until emergence. Emergence began on May 1, was rather unsynchronized, lasted for 2 months, and was temperature—dependent. Oviposition occurred during June and July; the females wee observed to oviposit only in the abundant emergent bur—reed Sparganium americanum. Eclosion occurred from mid—July until mid—August. The larvae grew rapidly in the succeeding months and attained the overwintering stages by October.
The Effect of Reduction in Stream Flow on Invertebrate Drift
Authors: Minshall G. Wayne , Winger Parley V.
Published: May 2006

Artificial reduction of stream discharge resulted in an increase in benthic invertebrates in the drift. Virtually all bottom—dwelling forms were affected. Entry into the drift seemed an active process initiated by changes in current velocity and depth, and resulting in reversal of the normal avoidance response to light.
The Feeding Ecology of Five Sympatric Finch Species
Authors: Pulliam H. Ronald , Enders Frank
Published: May 2006

Within habitats the overlap of food—size utilization of five sympatric finch species is almost 100% despite considerable differences in culmen lengths. It is suggested that the differences in bill size reflect differences in the proportion of large seeds in the set of habitats in which each species feeds and does not function to reduce competition within habitats. Although seed production was sufficient to maintain the finch populations through winter, the finches did eat at least 40% of the available seeds. Of the five finch species commonly present at least three seem to be limited by their winter food supply. The diversity of finches in the yield was not significantly correlated with either food abundance or food diversity.
The Second Derivative and Population Modeling
Authors: Clark John P.
Published: May 2006

Deficiencies in first—order differential equations are discussed as a motivation for considering second—order equations. The premise that environmental and intrapopulational forces act to alter the rate of change of a population, instead of the population size directly, is then investigated as a basis for modeling the dynamics of populations. The predictions of this assumption are compared to several classical features of previously published data and found to give some justification for the adoption of this view.
Vegetation, Microtopography, and Depth of Active Layer on Different Exposures in Subarctic Alpine Tundra
Authors: Price Larry W.
Published: May 2006

Four slopes with different exposures (southeast—, southwest—, east—, and north—facing), but with similar gradients, elevations, and rock type, were studies in the Ruby Mountains of southwest Yukon Territory, Canada, Vegetation was best developed on the southeast facing slope, was successively less on east— and southwest—facing slopes, and least on the northfacing slope. Solifluction lobes were present in varying degrees, and their development largely followed that of vegetation in that they were best developed on the southeast—facing slope and least well developed on the north— and southwest—facing slopes. The vegetation occurred in sharply delineated communities across the lobes on the southeast—facing slope, and the communities repeated themselves in predictable patterns. The same communities were present on the east—facing slope, but were not as distinct. Plant cover was relatively impoverished on southwest— and north—facing slopes, where there fewer microhabitats and where soil, moisture, and temperature conditions were not found in favorable combinations. Depth of the active layer largely corresponded to the presence of vegetation and microtopography. The active layer was shallowest and most variable on the southeast—facing slope. Plant cover, in general, was more important than exposure in determining the depth of thaw.
Some Effects of Stem Flow from Forest Canopy Trees on Chemical Properties of Soils
Authors: Gersper Paul L. , Holowaychuk N.
Published: May 2006

The most abundant elements contained in stem flow from American beech (Fagus grandifolia), red oak (Quercus rubra), and sugar maple (Acer saccharum) were C >>> K = Ca > Na = Mg = P. Variations in leaching potential and in concentration of chemical constituents around the base of beech trees, due to non—uniform stem flow, produced considerable variation in chemical properties of soil around the stems. The presence or absence of organic litter in surface soil samples caused only slight differences in chemical properties of the samples. Systematic variations in chemical properties of Bennington and Dekalb soils were developed with radial symmetry with respect to the stems of several tree species. Generally, the greater the difference in chemical properties of these soils with respect to distance from the tree stem, the greater the quantity of stem flow from the tree. In soil under those trees with relatively large quantities of stem flow, organic C, exchangeable K, and (137)Cs increased, while pH decreased progressively inward toward the stems, particularly in the upper 10—20 cm of soil. The magnitude of variations was greater in Bennington soil than in the more acidic and coarser textured Dekalb soil, and greater under beech trees and red oak than under sugar maple, pignut hickory (Carya glabra), and white oak (Quercus alba). The variations under beech and red oak were attributed mainly to effects of stem—flow water, whereas those under the other species were attributed mainly to effects of organic litter or to a combination of the two effects. The content of the fallout radioisotope (137)Cs in soil under the trees was used as substantiating evidence of the quantity of stem flow the trees.