bluuebunny/crossref_metadata_2025 huggingface dataset:
Physical and Chemical Factors Affecting Hatching in the Green Sea Turtle, Chelonia Mydas (L.)
Authors: Bustard H. Robert , Greenham Peter
Published: May 2006

The successful construction of an egg chamber by nesting turtles in coral sand requires that sand slippage be prevented. The factors preventing this are presence of sufficient moisture and/or tree rootlets. Under average conditions of tree rootlets, if the sand was moist enough for the turtle to successfully dig a chamber it contained an adequate water content for incubation. Chlorinity values of natural nests were very low, averaging about 50 mgCl—/kg. At the time of construction natural nest temperatures were about 25%C but metabolic heating increased this by approximately 6°C towards the end of the incubaton period. Under experimental conditions high incubation success was obtained at temperatures of 27, 30 and 32oC. No eggs hatched at 15, 20 and 38C. Eggs incubated at 30°C in sand containing 365 and 730 mgCl—/kg successfully hatched (although percentage hatch decreased with increasing chlorinity) indicating that chlorinity in the natural nest was not a limiting factor.
Alteration of Surface Soil Characteristics by Four Tree Species
Authors: Challinor David
Published: May 2006

Changes in soil proprties were studied in a 30—year—old mixed plot plantation of Norway spruce (Picea abies (L.) Karst.), red oak (Quercus rubra L.), white pine (Pinus strobus L.), and red pine (P. resinosa Ait.). The species plots were arranged in a Latin square. The surface 5 inches (12.8 cm) of soil below Norway spruce contained the highest percentage of organic matter and the greatest pore volume of the four species. However, it had a slower inflitration rate than the soil supporting the other two conifers, but not as slow as that below oak. Organic matter content in the soil below all species decreased rapidly with depth. Differences in the nitrogen, postassium and calcium content of the soil below the four species were concentrated in the surface 2 inches of soil and generally disappeared below that level. Soil below Norway spruce had the highest concentrations of the three aforementioned elements at the surface inch and that of white pine the least. The amount and quality of litter—derived organic matter in the soil was evidently the key factor in determining differences in the nutrient content of the soil in which these four tree species were growing.
Effects of Fire on an African Plateau Grassland
Authors: Lemon Paul C.
Published: May 2006

The Nyika Plateau of Malawi (formerly Nyasaland), Africa, is a fire—conditioned grassland. The large (750 square miles) plateau, which extends from 6,000 to 8,000 ft elevation at about 10° S lat, supports numerous endemic plants and animals suggesting a long, stable climatic and fire history. An intensive 10—month investigation concentrated on the vegetation, particularly plants that related to the welfare of eland, roan antelope, and zebra. Three herbaceous legunes were assessed on burning plots which had been maintained for the previous 4 years. Three sampling methods did not show injury to any of the legumes, and Aeschynomene oligophylla, a native nodule—producing forage plant, increased after burning. Incidental studies of braken fern showed no important changes in any combination of treatments, except that fire and close grazing might favor it. Judicious burning seems a satiscactory, perhaps even essential, land—use practice if an increase of the large grazing animals is the goal.
Forest Composition on Loessal and Non‐Loessal Soils in West‐Central Mississippi
Authors: Caplenor Donald
Published: May 2006

Four forest communities related to obvious edaphic areas in west—central Mississippe were sampled. Communities on thick loess were dominated by Liquidambar Styraciflua, Tilia sp., Quercus nigra, Liriodendron Tulipifera, Quercus falacata var. pagadaefllia, ulmus americana and rubra, and Carya cordiformis; those on thin loess by Fagus grandifolia, Nyssa sylvatica, Quercus velutina, and Carya tomentosa. Upland communities on non—loessal soils were dominated by Pinus taeda, Pinus echinata, Quercus falcata var. falcata, and Quercus alba; bottom land communities by Liquidambar Styraciflua, Fagus grandifolia, and Pinus glabra. Plant communities on deep loess and creek bottom non—loess were most closely related by species composition. These communities were quite distinct from communities of the general region as described in the literature. Examination of physical, climatic, and weather data indicated that the principal environmental factor delimiting the communities was availability of water.
The Relationship of the Distribution of the Diatom Skeletonema Tropicum to Temperature
Authors: Hulburt Edward M. , Guillard Robert R. L.
Published: May 2006

Skeletonema tropicum is distinguished from S. Costatum in possessing a greater number of chromatophores than the latter. S. tropicum is to be found north of the equator as far as latitude 30° in the western Atlantic Ocean, whereas the ubiquitous S. costatum extends into the cold waters farther north. The reason for the limited distribution of S. tropicum, as determined by growth of unialgal cultures, is its inability to live at temperatures less than 13°C.
Lethal Oxygen Thresholds for Certain Temporary Pond Invertebrates and Their Applicability to Field Situations
Authors: Moore Walter G. , Burn Alan
Published: May 2006

The normal dissolved oxygen patterns in certain temporary heterotophic pools in southeastern Louisiana are characterizd by relatively high values after initial flooding followed by a gradual decline to as low as 10% saturation as the pond ages. Laboratory delimitation of lethal oxygen thresholds for several characteristic temporary pond invertebrates revealed LD 50's of 0.1—0.4 ppm under test conditions. An unusual 8—day period of complete subsurface oxygen depletion during summer flooding in one such pond is described. Except for the conchostracans, there was little adverse effet on the macrofauna. This is attributed to the seeking of the partly oxygenated surface layer of the pond by the animals.
Logarithmic Regression as a Measure of Population Density Response: Comment on a Report by G. W. Salt
Authors: Solomon M. E.
Published: May 2006

Using the ratios of successive densities of an increasing insect population, Morris (1963a, b) fitted a straight line to the points in the plot of log Nt+1 versus log Nt, and used its slope as an index of density—dependence. Salt (1966) applied the method to protozoan populations, and also demonstrated that the points so plotted may fit a shallow curve rather than a straight line. He used the ratio between the slopes at the beginning and end of the curve as an index of density—dependence. This ratio is however an index of change in density—dependence rather than a measure of its intensity. The implications and treatment of such changes in slope are discussed.
An Experimental Study of the Role of Spiders as Predators in a Forest Litter Community. Part 1
Authors: Clarke Raymond D. , Grant P. R.
Published: May 2006

An experiment was designed to investigate the influence of spiders, as predator, upon other organisms in a maple forest litter community. A large number of spiders was removed from an enclosed (experimental) area; spiders were allowed to remain in 1 enclosed and 2 open areas (controls). Following spider removal, centipedes and collembola, known prey organisms of spiders, were at consistently higher densities in the experimental area than in the 3 controls during a 10 week period. Millipedes, not taken by spiders, were not consistently higher in the experimental area. These data indicate that predation by spiders is an important subtractive process acting on populations of centipedes and collembola.
Population Size, Ecology and Mineral Reservoir of the Millipede, Narceus Annularis (RAF.)
Authors: Shaw George Gerald
Published: May 2006

A very dense population of the millipede Narceus annularis (Raf.) was studied. Population size and sex ratio of adults in 3 hectares were determined five times during 1966. From this information the seasonal ecology of the millipede is outlined. Speculation on the significance of the population as a forest mineral reservoir and how this is calculated are given.
The Intrinsic Rate of Natural Increase of Irradiated Peromyscus in the Laboratory
Authors: French Norman R. , Kaaz Howard W.
Published: May 2006

This study was undertaken to determine the effect of continuous low—level exposure to gamma radiation on a population of small mammals (Peromyscus maniculatus sonoriensis) in the laboratory. The average dose rate was slightly greater than 1 roentgen/day. One group was exposed as adults, with irradiation beginning when they were weaned (age 3 to 4 weeks); another group was the offspring of the irradiated adults, hence these animals were irradiated since conception. Descendants from 3 separate field populations were present in each group. The intrinsic rate of natural increase, r, was increased in animals irradiated as adults (r = .3574), as a result of an elevation of the instantaneous rate of birth, b, and a reduction of the instantaneous death rate, d. Animals irradiated since conception showed a lower intrinsic rate of natural increase (r = .1897) than the controls (r = .3134) due to a lower b and an increased d. Life span was shortened by irradiation. The average life expectance at birth, eo, was 22.18 ± 1.54 months for control females, 19.61 ± 1.99 for the females irradiated as adults, and 15.62 ± 1.58 for females irradiated some conception. Male life expectancy was greater in each group. The animals that survived irradiation during the pre— and postnatal stages had greater further life expectancy than individuals of equivalent age groups that had been irradiated only as adults. Age specific natality, mx, was reduced by radiation, both by lowering the maximum number of young per female and by shortening the reproductive life spans of females. Reduction was greatest in the animals since conception. There was evidence of hyperovulation in the group irradiated as adults. There was variation among the 3 field populations represented, both in reproductive capacity of control animals and in sensitivity to radiation. Among controls, the population from the lowest field elevation had the greatest intrinsic rate of natural increase. This population showed the least sensitivity to radiation, judged by the change in r. The greatest sensitivity to radiation was in the population from intermediate elevations. Field populations of Peromyscus living in favorable environments might withstand the degree of reduction induced by this level of radiation exposure. Field populations living under less favorable conditions possibly could not.
Studies on The Limitation of a Natural Population of Paramecium Aurelia
Authors: Hairston Nelson G.
Published: May 2006

A natural population of Paramecium aurelia was sampled over the 2 years 1963 and 1964. The habitat was a small seep in a mature hardwood forest, and the population consisted almost entirely of Variety 2. Of 3,397 specimens collected, 1 was Variety 4. During the 2 years, four major peaks in population density were observed. These occurred in June and November of 1963 and in August and November of 1964. The two November peaks followed the annual leaf fall; the other peaks were related to heavy rain. These factors would introduce additional nutrients into the habitat; and it was concluded that the population was limited primarily by food. This conclusion was reinforced by the failure of the population maxima to be related to seasonal climatic factors, and by loss rates during population declines which were unrelated to the density of paramecia or to water temperature. Two experiments were carried out in the habitat: the addition of water to the area surrounding the seep, and the addition of paramecia to part of the seep. The hypothesis of food limitation was confirmed in the first experiment; the second showed that at sufficiently high densities, loss rate is related to density, and thus can act as a regulatory mechanism. The results of this study indicate that competition for a common resource is likely betwen the varieties of P. aurelia, six of which are known to occur in the vicinity of the seep. Variety 2 is evidently superior throughout this habitat, but other more complex habitats contain two to six varieties, indicating that there should be sufficient ecological differences between the varieties to allow each to be superior to the others under some natural conditions.
A New Model For Age‐Size Structure of a Population
Authors: Sinko James W. , Streifer William
Published: May 2006

An equation describing the dynamics of single species populations is derived. The model allows for variations in the physiological characteristics of animals of different ages and sizes. An analytical solution which holds under certain specific conditions is found. It is shown that Von Foerster's equation, the logistic equation and other prior models are special cases of the new model.
Composition and Productivity of a Subtropical Prairie
Authors: Porter Clyde L.
Published: May 2006

The vascular flora of a seasonally wet marl prairie in subtropical Florida was composed of 39 species, the most important of which were Muhlenbergia capillaris var. filipes, Mariscus jamaicensis, and Andropogon rhizomatus. These three species contributed greatly to the standing crop of live material which, except immediately following the September 1965 hurricane, was in excess of 107 g/m2 throughout the year. The peak standing crop of 161.4 g/m2 was reached in August under flooded conditions largely as a result of the growth of Muhlenbergia. The net production of organic matter was slight in some intervals but occurred throughout the year. Production was correlated largely with the wet and dry seasons, although minimum temperatures in January and February apparently depressed production slightly. The net productivity of the vascular component of the community was in excess of 200 g/m2 for the 1—year period. This value would be increased significantly if the productivity of the algal mat which covers the soil surface during the wet season were included.
Environmental Influences on Initiation and Maintenance of Hibernation in the Arctic Ground Squirrel, Citellus Undulatus
Authors: Drescher James W.
Published: May 2006

A controlled laboratory experiment was designed to investigate the ecological effects of temperature and photoperiod on patterns of hibernation in the arctic ground squirrel. Increased hibernation was clearly associated with regimes of decreasing photoperiod and constant temperature. Decreasing temperature and constant photoperiod had similar, though greater, effects. The combination of decreasing photoperiod and temperature, which constituted the best simulation of natural conditions, was associated with a hibernation time exceeding the sum of times in the two independent tests. Photoperiod seemed to have as great an influence on initiation of hibernation as did temperature, although the latter was more influential in maintaining hibernation. Statistical analysis clearly indicated that, under the conditions of this experiment, simulated natural photoperiod and temperature fluctuations served as external environmental timing cues to which arctic ground squirrels responded by adjusting their patterns of hibernation. It is suggested that the same mechanisms may operate in the field.
Contour Maps of Infestation Incidence Useful in Epizootiology of Screw‐Worms, Cochliomyia Hominivorax (Coquerel)
Authors: Davis Richard B.
Published: May 2006

Data collected during the Screw—Worm Eradication Program in the southwestern United States and northern Mexico provided opportunity for the development of contour maps to show the incidence of larvae of the screw—worm fly, Cochliomyia hominivorax (Coquerel), in animal wounds. An empirical technique was developed for choosing biologically meaningful contours and for actual contour plotting. This approach to the study of population dynamics should be useful in studies of other animals.
Daily Patterns in the Activity of the Arboreal Ant Azteca Alfari
Authors: Barnwell Franklin H.
Published: May 2006

The arboreal ant, Azteca alfari, normally restricts its activity to the crown of trees of the genus Cecropia. However, if the trunk of the tree is forked near the ground, ants may descend in large numbers to the fork where they cross from one side of the tree to the other. In these movements onto the lower trunk two different daily patterns have been recorded, one of strictly diurnal activity and the other with major activity occurring just after sunset.
The Interrelationship of the Aphid, Acyrthosiphon Pisum, and Its Parasite, Aphidius Smithi, in a Stable Environment
Authors: van den Bosch Robert , Lagace Charles F. , Stern Vernon M.
Published: May 2006

The interrelationship between the aphid, Acyrthosiphon pisum (Harris) and its parasite, Aphidius smithi Sharma & Shubba Rao, was studied in two strip harvested alfalfa fields near Famoso, California in the summer of 1963. Strip harvesting had a stabilizing effect on the alfalfa environment particularly as regards micro climate. As a result both Acyrthosiphon and Aphidius remained highly active in midsummer. By contrast in previously studied solid harvested alfalfa fields both species were strongly depressed during summertime. The current studies also produced information on migration of female Aphidius and on the wasp's density dependence.
Temperal Dissociation and Population Regulation in Certain Hesperiine Butterflies
Authors: Clench Harry K.
Published: May 2006

Eleven species of flower feeding hesperiine butterflies are open field residents in a locality in western Pennsylvania. They may be grouped in 5 sets. The species of each of the first 4 sets (respectively 3, 2, 2, 2 species) are remarkably precise chronological replacements in the timing of their average adult flight periods (the basis for the set groupings). The times of the population peaks of set II, furthermore, coincide with population minima of set 1 (the numerically dominant set). Aggregate Daily Nutrient Demand (DND–the product of average body volume and estimated average population density of a species on a given day) of these species reaches 4 peaks through the annual season, and these peaks coincide approximately in time with the peaks of aggregate DND of all other butterflies in the area and with the local flowering times of the major adult food flower species. (The fifth set, of two species, is quite rare and replacement timing is imperfect, possibly related to the extreme mimetic resemblance of the two.) It is argued that these temporal dissociations arose adaptively to reduce or eliminate competition for adult food (flower nectar), and that the availability of adult food is therefore a population regulator of these butterflies.
An Instrument for Measuring Light Intensities in Dense Vegetation
Authors: Wiens John A.
Published: May 2006

The design and use of an instrument which permits rapid sampling of light intensity and penetration in dense vegetation (e.g. grasslands, marshes) or small spaces (e.g. tree holes, burrows) are described. A small photoconductor is mounted on a narrow probe, which is attached by a long lead wire to the reading instrument.
Passive Dispersal of Viable Algae and Protozoa By Certain Craneflies and Midges
Authors: Revill Donald L. , Stewart Kenneth W. , Schlichting Harold E.
Published: May 2006

Four species of aquatic Diptera, Tipula triplex Walker (Tipulidae), Bittacomorpha clavipes (F.) (Ptychopteridae), Chaoborus punctipennis (Say) (Culicidae), and Tendipes sp. (Tendipedidae), were collected aseptically and used to inoculate sterile soil—water extract. Twenty—one genera of algae, five Protozoa, a moss protonema and Alternaria were identified in the 51 cultured washings.Comparisons by “Student's t” showed that B. clavipes carried significantly more algae and Protozoa than the other three insect species, and T. triplex carried more than the midges. Found in over 18% of the cultures were the blue—green algae Anabaena, Anacystis, Chroococcus and Phormidium, and the green algae Chlamydomonas, Chlorella, Chlorococcum and Protococcus. The protozoans were found at lower frequencies. It is suggested that these viable algae and Protozoa are carried by these four insect species across land barriers.
Wintertime Photosynthesis of Bristlecone Pine (Pinus Aristata) In the White Mountains of California
Authors: Schulze E. D. , Mooney H. A. , Dunn E. L.
Published: May 2006

Winter rates of photosynthesis and respiration in bristlecone pine were measured at controlled temperatures at 3,094 m elevation. Following the onset of severely cold temperatures in autumn, net photosynthesis declined sharply. By midwinter net photosynthesis became zero and remained there through early spring; during this time only low gross photosynthesis could be measured. Respiration rates remained high until late winter and then dropped significantly in early spring when temperatures increased and the soil thawed. The absence of net photosynthesis and the continued high respiration results in a large negative CO2 balance by the end of the winter. Approximately 117 hr of photosynthesis during summertime at peak rates are needed to equalize the winter loss of 140 mg CO2 per gram dry weight of photosynthetically active tissue. These findings are related to the growth of bristlecone pine at timberline.
Climate: A Factor in the Origin of the Pole Blight Disease of Pinus Monticola Dougl
Authors: Leaphart Charles D. , Stage Albert R.
Published: May 2006

Measurements of cores or disc samples representing slightly more than 76,000 annual rings from 336 western white pine tree were compiled to obtain a set of deviations from normal growth of healthy trees that would express the response of these trees to variation in the environment during the last 280 years. Their growth was demonstrated to be a function of temperature and available moisture for the period of climatic record from 1912 to 1958. Extrapolating the relation of growth to weather to the long tree ring record of western white pine, we find that the period 1916—40 represents the most adverse growth conditions with regard to intensity and duration in the last 280 years. This drought, superimposed on sites having severe moisture—stress characteristics, triggered the chain of events which ultimately resulted in pole blight. If the unfavorable conditions for growth during 1916—40 do not represent a shift to a new climatic mean and if western white pine is regenerated only on sites with low moisture—stress characteristics, the probability is high that pole blight will not reoccur for many centuries in stands regenerated from this date on.
Innate Control of Migrations of Salmon and Trout Fry From Natal Gravels to Rearing Areas
Authors: Raleigh Robert F.
Published: May 2006

The upstream and downstream directional responses of demes of sockeye salmon (Oncorhynchus nerka) fry from inlet and outlet streams hatched and reared under controlled, identical conditions were tested in the laboratory. The tests compared innate directional responses of fry from the two sources to variables of water source and temperature. Both variables influenced the directional responses of the fry. The direction of migration (upstream for outlet fry or downstream for inlet fry) and response to changes in the test variables differed substantially between fry from inlet or outlet streams; this response difference held for populations of sockeye salmon from different geographical locations (Canada and Alaska). The differences were concluded to be innate in origin. Single tests of fry of rainbow (Salmo gairdneri) and cutthroat (S. clarki) trout from inlet and outlet streams indicated that directional responses of fry from these species are also innately influenced. The significance of matching the innate responses of donor stocks of fish to the characteristics of a recipient environment is discussed.
Mechanisms of Competitive Exclusion Between Two Species of Chipmunks
Authors: Brown James H.
Published: May 2006

Two species of chipmunks, Eutamias dorsalis and E. umbrinus exclude each other from certain elevations on isolated mountain ranges in the central Great Basin. Competitive success is determined by habitat; dorsalis excludes umbrinus from the sparse pinon—juniper forests at lower elevations and umbrinus excludes dorsalis from the denser forests at higher altitudes. The two species occur together only in a very narrow strip of intermediate habitat. Observation of the behavior and interactions of the two species within this overlap zone resulted in the following explanation for the mutual exclusion. E. dorsalis, the more aggressive and more terrestrial species, chases umbrinus from those areas where the trees are so widely spaced that umbrinus must flee on the ground. The competitive advantage immediately shifts to the more social and arboreal umbrinus when the trees are sufficiently large and dense that their branches interlock. In these habitats umbrinus readily escapes dorsalis by fleeing through the trees over routes that the more aggressive species cannot follow. In such situations the aggressive nature of dorsalis actually becomes competitively disadvantageous because the more social umbrinus is so numerous that dorsalis wastes a great deal of time and energy on fruitless chases. The differences between the two species in aggressive behavior apparently represent adaptations to the density of cover and food resources in their habitats. The main mechanisms of the competitive interaction between these two chipmunks (interspecific aggression, the ability of the subordinate species to utilize some feature of the habitat to escape from the dominant species, and aggressive neglect on the part of the dominant species) may frequently be important in cases of competitive exclusion between highly mobile animals.
Competition Between Two Chipmunk Species (Eutamias)
Authors: Sheppard David H.
Published: May 2006

Two chipmunk species were studied in the mountains of western Alberta from 1961 to 1965. One species, Eutamias minimus, is largely confined to alpine habitat but also ranges into subalpine forest, where its distribution narrowly overlaps that of E. amoenus. The fundamental niches of the two species, estimated from their habitat distributions elsewhere, are both reduced in western Alberta. Mark and recapture trapping in an overlap zone showed that neither species selected habitat deficient in cover and both species made the same relative use of the available forest. The boundary between the two species was not clearly predictable by obvious habitat features. Eutamias amoenus luteiventris is larger than E. minimus oreocetes and, on an average, has larger litters, earlier maturity, and higher populations density. The two species take similar foods, depending on availability in their respective habitats, but the food consumption of individual minimus is less than that of amoenus. In the laboratory, amoenus was highly successful in interspecific encounters with minimus, regardless of whether or not minimus was a resident of the observation cage. In addition, amoenus dominated minimus in a mixed—species group and minimus exhibited avoidance behavior under such conditions. The highly developed aggressive behavior of Eutamias amoenus enables it to exclude E. minimus from subalpine habitats, but the latter survives in alpine situations where its small size is an adaptation to a reduced food supply.
Some Effects of Temperature and Oxygen Concentration on Phyllopod Ecology
Authors: Horne Francis R.
Published: May 2006

Seasonal distributional patterns of five phyllopods from southwest Texas are similar to those of the same species from more northern latitudes. At both latitudes a primary environmental cue controlling the appearance of phyllopods seems to be temperature. For instance, in Texas Branchinecta packardi was the only cold water species. In addition to the effects of temperature on phyllopod zoogeography, diurnal studies show that high temperatures contribute both directly and indirectly to oxygen depletion in temporary ponds. The comparative tolerance of phyllopods to near anaerobic conditions was as follows: calm shrimp, Caenestheriella setosa > tadpole shrimp, Triops longicaudatus > fairy shrimp, Streptocephalus texanus.
The Structure of Tropical Bat Faunas
Authors: McNab Brian K.
Published: May 2006

The species that constitute a tropical bat fauna partition the food available in an environment in an orderly manner, the two most important parameters of partitioning being the type of food and food particle size. On small Caribbean islands there seems to be a fundamental partitioning of food that includes one fruit bat, two nectar bats, two insect bats, and one fishing bat; other food habits, such as blood and meat, are not generally present because of the apparent absence of these foods in sufficient quantities. Mainland tropical bat faunas are similarly structured in terms of food type and size, but it is not possible to make a complete analysis due to the many rare species, whose habits are generally unknown.
Intraseasonal Change in Caloric Content of Some Freshwater Invertebrates
Authors: Wissing Thomas E. , Hasler Arthur D.
Published: May 2006

Intraseasonal changes in caloric contents of planktonic cladocerans (Daphnia spp. and Leptodora kindtii), amphipods (Hyalella azteca), and chironomid larvae (primarily Glyptotendipes sp.) were studied in 1968. Mid—summer decreases of 823, 2117, and 422 g—cal/g dry weight were observed in the Daphnia, L. kindtii, and H. azteca, respectively. Calorica content of Daphnia increased again during August and early September. The energy content of chironomid larvae increased steadily during June and July and then declined. The low value (4899 g—cal/g dry weight) occurred on 9 September. Variation in energy content of the Daphnia appeared to be related to known changes in population numbers. The influence of significant changes in caloric contents of food organisms on the daily ration of predator fish species is discussed.
Soil Microfungi of Dry to Mesic Conifer‐Hardwood Forests in Northern Wisconsin
Authors: Christensen Martha
Published: May 2006

The Soil microfungi in 36 northern Wisconsin conifer—hardwood forests have been surveyed by the dilution plate technique. Populations of 180 isolates from six sites in each forest examined, and frequency (sites of occurrence) was used to assess species importance. The 6,461 isolates represented 476 taxonomic entities, but only 87 (18%) of these occurred in three or more forests or had one frequency of at least 50% The principal forms in the conifer—hardwood unit were Mortierella vinacea II, Trichoderma spp., Mortierella isabellina, Penicillium nigricans, Mortierella nana, Pullularia pullulans, and Monocillium humicola var. brunneum. A few of the top—ranking conifer—hardwood microfungi are widely distributed in Wisconsin soils, others have occurred in similar types in northern and southern Wisconsin, and a third assemblage (including Mortierella vinacea II and M. nana) has been isolated only from conifer and conifer—hardwood soils in the State. An ordination, based upon compositional similarity in the microfungal communities, revealed a greatest difference between maple and hemlock soil populations. When tree importance values were superimposed on the three—dimensional microfungal ordination, spheres of occurrence were apparent for all major tree dominants. This finding confirmed the hypothesis that species composition in soil microfungal communities is correlated with vegetation, but litter calcium content, rather than the linear dry—to—mesic vegetational gradient, correlated with the first axis in the microfungal ordination. In a beech—hemlock forest soil, related densities for several dominant taxa varied with season. Both spores and hyphal fragments gave rise to colonies on the dilution plates prepared for six forest soils, and there was a direct correspondence between total colonies and numbers of germinating spores. A comparison of densities for four dominant species indicated a possible antibiotic interaction.
Germination Response to Temperature and Salinity of Four Dune Grasses from the Outer Bank of North Carolina
Authors: Senaca Ernest D.
Published: May 2006

At four constant thermoperiods (65°, 75°, 85° and 95°F) and three alternating diurnal thermoperiods (65° —75°, 65° —95°F), good germination (above 70%) was obtained with seed of Ammophila breviligulata Fern., Panicum amarulum Hitch. and Chase., and Spartina patens (Ait.) Muhl. without cold treatment under certain temperature conditions. None of the constant temperature treatments yielded good germination. All attempts to obtain good germination with Uniola paniculata L. without cold treatment were unsuccessful. Various periods of cold treatment had no effect upon subsequent germination in the 65° —95°F alternating diurnal thermoperiod in A. brevilligulata and S. patens. In P. amarulum cold treatment for 15 days was sufficient to ensure good germination. Cold treatment for 30 days was adequate for good germination in U. paniculata, but 15 days was not always sufficient. When cold treatment for 30 days at 43°F preceded germination in the seven temperature conditions, germination was increased in all species. Maximum tolerance limits for A. breviligulata and U. paniculata to NaCl lie between 1.0% and 1.5%. The upper limit of NaCl concentration for germination of P. amarulum is between 1.5% and 2.0% and for S. patens about 4.0%. Germination response to salinity was primarily an inverse linear relationship for A. breviligulata, P. amarulum, and U. paniculata, but a curvilinear relationship in S. patens. In this species germination was successful at 2.0% NaCl. Germination inhibition in A. breviligulata, P. amarulum, and S. patens was apparently primarily an osmotic effect. Based on germination response, S. patens is the most salt tolerant, followed by P. amarulum which is more than U. paniculata. A. breviligulata is the most salt sensitive.
Population Growth Efficiencies on Laboratory Hydra Pseudoligactis Hyman Populations
Authors: Schroeder Lauren
Published: May 2006

Population growth efficiencies (GE) of 22 laboratory populations of Hydra pseudoligactis fed Artemia sp. nauplii were determined. Maximum growth efficiencies of ca. 37% were observed for ingestion rates greater than 0.5 cal each day per calorie of hydra. The instantaneous growth rate increased continuously with increased ingestion above the minimum of ca. 0.25 cal each day per calorie of hydra. The maximum calculated net efficiency was ca. 55%. Although GE was constant above ingestion rates of 0.5, net efficiency and growth rates continued to increase with increasing rates of ingestion.
Allelopathy by Myrmecophytes: The Ant Azteca as an Allelopathic Agent of Cecropia
Authors: Janzen Daniel H.
Published: May 2006

Azteca ants, that obligatorily live in neotropical second—growth trees of the genus Cecropia, kill vine ends that begin to climb on the Cecropia trunk. Presumably this aids the Cecropia tree in its efforts to maintain an emergent position in the general canopy, and may be one of the selective advantages of being occupied by an Azteca colony. This system is, in both process and pattern, extremely similar to that of the swollen—thorn acacias and their ant occupants. In both cases the ants are effectively allelopathic agents, and are functionally analogous to the chemicals liberated by some plants in their competitive interactions with other plants; like these chemicals, the ants are "produced" at a metabolic cost to the plant. The ants may, however, be a more efficient allelopathic agent than a chemical because of their versatility.
Distribution on Environmental Gradients: Theory and a Preliminary Interpretation of Distributional Patterns in the Avifauna of the Cordillera Vilcabamba, Peru
Authors: Terborgh John
Published: May 2006

A new theoretical approach to the study of distribution is presented in this paper. The central concerns the types of interactions between organisms and their surroundings which may function to impose limits on the occurrence of species on a smooth unifactorial environmental gradient. The theory is constructed of a set of three complementary and mutually exclusive models which arbitrarily are given the power of accounting for all possible distributions. Each of the models predicts a different patter of distribution within a group of organisms and each contains two or more unique features which serve to distinguish it from the others. In their simplest form the models state that the occurrence of species is limited respectively by: (i) physical or biological conditions that vary in parallel with the measured gradient, (ii) competitive exclusion and (iii) environmental discontinuities (ecotones). Predictions of each model include (a) the shape of population density curves, (b) the shape of congruity (faunal attenuation) curves, (c) distributional patterns at the termini of gradients, and (d) the form oft he frequency distribution of ecological amplitudes. Application of the theory is demonstrated with data obtained in a study of the distribution of bird species on a uniform elevational gradient in the Eastern Andes of Peru. A series of four expeditions to the Northern Massif of the Cordillera Vilcabamba, a vast undisturbed mountain wilderness, provided information on the upper and lower limits of occurrence of over 410 species of forest birds. Faunal composition and the relative abundances of many species wee estimated at each of 15 stations through large netted samples of birds (170—604 individuals). Following a protocol described in the text, the upper and lower limits of 261 species were assigned to one or another of the three models. Certain limitations of method result in a small number of unavoidable errors in these assignments; hence the outcome of the partitioning procedure is only a first approximation. As evaluated by this preliminary analysis, the three mechanisms of distributional limitation differ appreciably in their importance in the Vilcabamba avifauna. Ecotones account for less than 20% of the distributional limits, competitive exclusion for about one—third of the limits and gradually changing conditions along the gradient for about one—half of the limits.
Forests of Small Stream Bottoms in the Coastal Plain of Southwestern Alabama
Authors: Gemborys S. R. , Hodgkins Earl J.
Published: May 2006

Overstory and understory data were collected from 49 forest stands in 27 small stream bottoms in the Gulf Coastal Plain region of southwestern Alabama. The stands were arranged in a single—dimensioned ordination on the basis of the importance values of the persistent species in the overstories. Leading dominant species, from the dry end to the wet end of the ordination gradient, were Cornus florida, Pinus palustris, Quercus nigra, Liquidambar styraciflua, Nyssa sylvatica v. sylvatica, Magnolia virginiana, and N. sylvatica v. biflora. Two important seral species, most prominent at the middle of the ordination gradient and of relatively little importance at either end, were Pinus elliottii and Liriodendron tulipifera. The stand position on the ordination gradient, referred to as the moisture—regime index, was significantly related to water—table depth, soil—surface gradient, and soil pH at 63.5 cm. Failure to obtain significant relationship with other soil variables was attributed to the high frequency of fresh soil deposition in the small stream bottoms. As a check on the ordination analysis, species—present data were used to construct a species—correlation diagram. When species moisture—regime numbers from the ordination analysis were inserted in this diagram, good agreement was revealed in the results of the two independent analyses.
Photosynthesis Light Sensor and Meter
Authors: Biggs W. W. , Edison A. R. , Eastin Jerry D. , Brown K. W. , Maranville J. W. , Clegg M. D.
Published: May 2006

An improved light sensor with a spectral response based on photon absorption between 400 and 700 nm was developed for both field and environmental chamber use. The indicated sensor response was selected because it approximates the photosynthetic response of plants for which data are available. A silicon photo cell with high response in the visible range was used as a sensor. The spectral response was controlled by use of a Kodak Gelatin Wratten Filter. A visible bandpass interference filter produced a sharp cutoff at 700 nm. Heat—absorbing glass eliminated transmission beyond 1,000 nm, and a diffusing plastic and filters were mounted in a miniaturized cosine—corrected head that was fitted with a collimating system to eliminate spectral shifts which arise when light enters the interference filter at oblique angles. Error calculations indicate that under sun—and—sky radiation and various artificial light sources the errors are smaller than those associated with available standard calibration lamps. The device also includes a battery—operated meter circuit suitable for making measurements over a wide range of intensities.
Patterns of Hatching Success in Subarctic Birds
Authors: Jehl Joseph R.
Published: May 2006

Data from a single subarctic locality are used to test Ricklef's general conclusions regarding patters of nesting mortality in arctic birds. They provide additional evidence that hatching success is greater among arctic than among Temperate Zone passerines. However, they do not indicate important differences in hatching success between ground—nesting birds with precocial young and those with altricial young, nor do they confirm that predator—induced nesting losses are density dependent in arctic regions. Predation may be a more important cause of nesting failure than Ricklefs acknowledged. Differences in our findings in part from differences in sampling methods. further analyses of nesting morality should combine data from studies of selected species with those from regional studies.
An Insect Dispersal Parameter
Authors: Scotter D. R. , Lamb K. P. , Hassan E.
Published: May 2006

A random walk model for insect dispersal leads to the diffusion equation. Diffusivity is a suitable parameter to characterize the rate of dispersal. The methods by which diffusivity may be computed using data from the most common types of dispersal experiments are discussed. Some of the implications and limitations of the model are mentioned. The probability that an insect will move more than a certain distance in a certain time in proposed as a useful statistic. Dispersal data from adult Pantorhytes weevils in a dense canopy of cacao are presented and successfully interpreted in terms of the diffusion analysis. The diffusivity found was 0.75 m2 day(—1). It is calculated that there is a probability of 0.01 that any beetle will move more than 20 m in 1 month.
Labeling Adults of Red Palm Weevil (Rhynchophorus Ferrugineus) with Cerium for Detection by Neutron Activation
Authors: Rahalkar G. W. , Mistry K. B. , Harwalkar M. R. , Bharathan K. G. , Gopal-Ayengar A. R.
Published: May 2006

Adult red palm weevils (Rhynchophorus ferrugineus Oliv.) were labeled by topical application of cerium chloride (CeCl_3) in 90% ethanol. Marked adults were detectable by assay of radiocerium following neutron activation of excised elytra. No significant loss of cerium from marked insects occurred over prolonged periods or after repeated washing with water. This marking technique has potential application in ecological studies, especially those of long duration.
Time Lag in Population Growth Response of Isochrysis Galbana to a Variable Nitrate Environment
Authors: Caperon John
Published: May 2006

Non—steady—state population growth equations are presented for Isochrysis galbana growing in a nitrate limited chemostat. It is necessary to introduce a more general response function in place of the customary time—lag parameter to describe the observed population growth. The model successfully predicts the population growth over two experiments, one of 56 and another of 80 days, under a variety of dynamic and steady—state growth conditions. The increasing instability at lower growth rates, shown by both the data and the growth equations, indicates that steady—state growth equations may not be adequate in at least some natural environments.
Weight Dynamics of Eucalyptus in the Mallee Vegetation of Southeast Australia
Authors: Holland P. G.
Published: May 2006

Methods for the estimation of aerial biomas and its annual increment were devised and with them studies of the weight dynamics of Eucalyptus in two stands of mallee vegetation were made. The stands differ in species composition, age, and aerial biomass, yet the eucalypts of both added 6—8% to their aboveground biomass in 1965—66. In the older stand mean stem age is much less than stand age, and active stem replacement processes operate within it. But in the younger stand these processes do not appear, as yet, to have begun, and most stems of Eucalyptus in it are of the same age as the stand. Although both stands were fairly productive of plant tissues during the 1965—67 drought, it is likely that mature stands of mallee vegetation maintain their aerial biomass within limits determined by annual variations in the biotic and physical environments. This control shows in the variety of stem ages represented in the older stand.
Experimental Zoogeography of Islands: A Model for Insular Colonization
Authors: Simberloff Daniel S.
Published: May 2006

A distinction is made between immigration rate (in spp./time) for an island, and invasion rate (in propagules/time) for a species and an island. An analogous distinction is drawn between an island extinction rate and a species extinction rate (or intrinsic probability of extinction in a given time interval). It is claimed that the most objective definition for "propagule" is any animal of group capable of population increase under any conceivable circumstances. Immigration and island extinction curves are unique only if plotted against time, not against number of species. A model for non—interactive colonization is discussed, and its equilibrium number of species, ° derived. It is shown that data from the defaunated Florida Keys can be interpreted as arising from non—interactive colonization to an ° near the non—interactive ° (and to a point above a more enduring interactive °), followed by a slow decline in ° (as population sizes and interaction increase) to an enduring ° near that obtaining before defaunation. The effect on this scheme of increasing distance from source area is shown, and a simulation of the non—interactive part of the scheme was performed with corroborates that part of the model. Explicit equations for the "expected" colonization, immigration, and island extinction curves are given for non—interactive colonization, and predictions are given about the general changes in these curves as interaction becomes significant.
Exploration and Movement Patterns of the Canyon Mouse Peromyscus Crinitus in an Extensive Laboratory Enclosure
Authors: Brant Daniel H. , Kavanau J. Lee
Published: May 2006

In a laboratory enclosure in which individual canyon mice Peromyscus crinitus had continuous access to complex, extensive, burrow—simulating mazes for several days, the spontaneous movement patterns were similar to the known movement patterns of Permyscus in the wild. Since establishing and engaging in these movement patterns appear to be self—rewarding activities, they are assumed to be the expression of inherited tendencies to explore and to develop wide—ranging adapted locomotor activity, including the establishment of home ranges. When the animals ran an activity wheel, their exploration of new regions ceased and their retraversal of familiar regions decreased. These findings suggest that a dynamic balance between exploration and general activity determines the size of the movement patterns, and that the altering of environmental variables in extensive enclosures can be used to determine the extent to which each variable influences the movement patterns.