bluuebunny/crossref_metadata_2025 huggingface dataset:
Population Changes During the 1957‐1958 Vole (Microtus) Outbreak in California
Authors: Murray Keith F.
Published: May 2006

A high population peak in Microtus montanus during 1957—1958 was synchronous throughout at least the California part of its range. Densities reached drastic outbreak levels only in relatively large cultivated basins. In the Tule Lake basin of northern California, populations survived the winter in sharply reduced numbers but did not suffer a drastic crash. From April 1958 onward, in spite of the resumption of breeding and renewed food and cover, voles in most fields continued to decline to the point of disappearance. Although breeding was fairly normal, relatively few young were successfully recruited into the population. A temporary resurgence of numbers occurred in some peripheral fields. Voles in favorable natural habitats showed less evidence of reaching extreme numbers and declined more slowly during spring than did those in cultivated fields. Voles in Bridgeport Valley, Mono County, had nearly disappeared by January 20, and were thought to have crashed in the wake of a severe precipitation—freeze episode. Tularemia was found at Tule Lake in December and early January, but subsequent testing was negative and there was no further evidence of die—offs. There were positive findings of Salmonella enteridis and Group A Streptococcus. Flea densities on Microtus were low. Neither the effects of disease nor destruction of food supply were thought to explain adequately the termination of the outbreak. Concepts of reduced viability due to crowding were compatible with observed events.
String Bogs and Other Patterned Organic Terrain Near Seney, Upper Michigan
Authors: Heinselman M. L.
Published: May 2006

Treeless string bogs and topographically oriented strips of bog forest have been discovered near Seney, Michigan, lat 46 degrees 15' N, perhaps the southern limit of patterned bogs on the North American continent. Patterned ground has developed through paludification of a sandplain dotted with extinct dunes and sloping about 8 ft/mile. Many peatlands in Michigan, Minnesota, and Wisconsin have similar slopes and exhibit patterning in various degrees. Thus the principles that can explain the patterns and bog—forming processes at Seney may apply to large areas of forested and treeless peatland. Studies should be directed toward the interrelations between vegetation, water chemistry, local geology, peatland topography, peat hydrology, peat accumulation, and physical geomorphic processes.
The Analysis of Multidimensional Contingency Tables
Authors: Fienberg Stephen E.
Published: May 2006

Ecological data often come in the form of multidimensional tables of counts, referred to as contingency tables. During the last decade several new methods of analyzing such tables have been proposed. Here, a class of models analogous to those used in the analysis of variance is discussed, and a method for computing the expected cell counts for the different models is presented. Two differenet tests for checking the goodness—of—fit of a particular model are then examined. The first is the simple generalization of the Pearson chi—square test statistic, while the second is referred to as the likelihood—ratio chi—square test statistic. Both have the same asympototic g2 distribution. The likelihood—ratio statistic can be used in the selection of a suitable model, via the technique of partitioning. All of the methods presented are illustrated using data collected by Schoener on lizards from the West Indies.
Effects of Temperature, Rainfall, and Fauna on Transfer of ^(137)CS, K, MG, and Mass in Consumer‐Decomposer Microcosms
Authors: Witkamp Martin , Frank Marilyn L.
Published: May 2006

Microcosms containing leaf litter, sand, and three, six, or nine millipedes were incubated for 14 weeks at either 5°, 15°, or 25°C under three rates of simulated rainfall. Effects of temperature, rate of leaching, and millipede density on transfer of (137)Cs, K, Mg, and mass and on evolution of CO2 were analyzed statistically and by analog computer simulation. Loss rates from litter increased in the order: Mg < mass <(137)Cs <K; the effects of the three environmental variables on transfer also increased in the same order. Transfer of Mg was primarily to humus; mass to CO2; (137)Cs to sand; and K to leachate. Loss rates of Mg and mass evolution of CO2, and transfers of (137)Cs were all influenced primarily by temperature and secondarily by millipede density. Only K was affected more by leaching than by millipedes. Production of CO2 showed a Q10 ° 2, but mineral transfer did not double at each 10°C increase because of significant temperature—moisture interaction. Computer simulation showed that pathways and rate coefficients for transfer of (137)Cs were identical whether it originated from litter or soil, that the major pathways were from litter to soil and from litter via millipedes to soil, and that about 7% of the initial leaf (137)Cs was easily leached from litter and transferred to soil and leachate during the first month. At higher temperatures, drying and rewetting cycles of the litter appeared to shift the litter—to—soil transfer of (137)Cs from the millipede ingestion—excretion pathway to that effected by microbial immobilization—mineralizaton cycles.
Competition for Nutrients by Marine Phytoplankton in Oceanic, Castal, and Estuarine Regions
Authors: Hulburt Edward M.
Published: May 2006

Fluctuations in the densities of marine phytoplankton species in the open and coastal ocean follow a sequence wherein one or several species may increase in abundance very much without causing a reduction in abundance of other forms. Theoretical calculations of the maximum size of nutrient—depleted zones about the plankton cells show that overlapping of these zones cannot occur at cell densities less than 3 x 108/liter. Since densities rarely exceed 106/liter in the open and coastal ocean, there is no possibility of an abundant species monopolizing the nutrient supply and forcing a less abundant form to extinction. The change from a coccolithophore—dominated plankton in the Sargasso Sea to the diatom—dominated plankton in the coastal water off New York cannot, therefore, be attributed to competition for nutrients by the two types of cells. But in some very shallow estuaries, Great South Bay and Moriches Bay near New York and Salt Pond at Woods Hole, the dominant forms sink considerably more slowly than the coastal and oceanic species and would thus be at an advantage over the latter. Plankton concentrations in the estuaries may come close to or exceed 109/litter, and monopolization of the nutrient supply should aid in the continued dominance of the abundant forms, eventually bringing about the extinction of many of the residual forms. This sequence is considered to be a real possibility in these estuaries and to be the reason for the reduced diversity of species observed there.
Freezing Resistance in Willows from Different Climates
Authors: Sakai A.
Published: May 2006

Freezing resistance studies were carried out on Salix sachalinensis (northern Japan), S. Sieboldiana (southwestern Japan), S. babylonica (Japan proper and Hachijo Island), S. caerulea (Lahore, Pakistan), S. tetrasperma (Singapore and Quetta, Pakistan), S. bonplandiana (Mexico City), and S. safsaf (Cairo). Twigs of the tenderest willows (S. Sieboldiana) wintering in the southwestern part of Japan resisted freezing to about —15°C, but when hardened at —3°C for 14 days in Sapporo, they resisted freezing at °50°C. After growing in Sapporo (northern Japan) for 1 year, these twigs survived immersion in liquid nitrogen (—196°C) following prefreezing at —20°C in winter. Cuttings from willows native to the tropics, when grown outdoors in Sapporo for 1 year, produced twigs which resisted freezing to about —30°C for 16 hr. A genetic potential to withstand freezing to very low temperatures is apparently present even in tropical willows. The temperatures most effective in producing maximum freezing resistance were nearly the same for both northern and subtropical willows irrespective of their native habitats, and the degree of freezing resistance in winter of any species of willow differed considerably and depended on air temperature in the localities at which plants were wintering.
Seed Dormancy in Luzula Spicata and L. Parviflora
Authors: Bell Katherine L. , Amen Ralph D.
Published: May 2006

Inhibitors localized at the micropyle and interacting with gibberellin impose dormancy on seeds of both Luzula spicata and L. parviflora from the Colorado Front Range. Removal of the inhibition by precise scarfication elicits germination in both species. Luzula spicata seeds lacking precise scarification were found germinated in tundra soil. Germination was experimentally induced in L. spicata by random scarification, which may be accomplished by repeated freeze—thaw cycles, followed by stratification for 2—3 months. The inhibitor in L. parviflora was inactivated by after—ripening. Germination requirements of L. spicata may represent adaptions to fall freeze—thaw cycles followed by extended chilling under accumulated snow in its tundra habitat. Luzula parviflora, a subalpine and montane species, lacks these adaptations.
Variation in the Availability of Food as a Cause of Fluctuations in Predator and Prey Population Densities
Authors: Jensen A. L. , Ball R. C.
Published: May 2006

Large cyclic fluctuations in the densities of laboratory populations of both bacteria and Protozoa were produced by adding sterile nutrient solutions to the cultures at long intervals. The fluctuations were greatly reduced, and they were no longer cyclic when the nutrient solution was added at shorter intervals. Experimentally, the major form of interaction between bacteria and Protozoa was predation of the Protozoa upon the bacteria. Both the population density of the Protozoa and the population density of the bacteria were reduced by decreasing the amount of nutrient solution added to the cultures.
Genetic vs. Environmentally Induced Variation in Medusahead (Taeniatherum Asperum [Simokai] Nevski)
Authors: Nelson Jack R. , Harris Grant A. , Goebel Carl J.
Published: May 2006

The influences of seed—nursery environment upon genecological characteristics of 20 medusahead strains was studied. Environmentally induced variation was observed in germination, early height development, and winter survival. Small, but significant, variation in dates of spike emergence and anthesis, caused by differences in seed—nursery environment, were observed. Results suggest that the common practice of attaching genecological significance to wild—grown seed may be subject to error, especially in germination and early phenological stages following germination.
Intraspecific Differences in Temperature‐Induced Respiratory Acclimation of Desert Saltbush
Authors: Chatterton N. J. , McKell C. M. , Strain B. R.
Published: May 2006

Following preconditioning to three temperature regimes (5°—16°C, 21°—32°C, 32°—43°C), dark respiration was measured over a 35°C range in three geographically isolated populations of Atriplex polycarpa (Torr.) S. Wats. Intraspecific differences in carbon dioxide exchange were found which correlated with the climate of the area of origin of the population.
Growth Rate of the Rock‐Boring Clam Penitella Penita (Conrad 1837) in Relation to Hardness of Rock and Other Factors
Authors: Evans John W.
Published: May 2006

The morphology and the growth rate of three populations of Penitella penita from substrata of different hardness were studied. Morphology differed significantly, the valves being delicate and elongate in the soft rock and heavy and tumid in he hard rock. The rate of growth decreased as the hardness of the substratum increased. Evidence is presented which suggests that these differences are not genetically controlled but are induced by the relative hardness of the substratum. Growth rate is dependent both on the width of growth bands and on the frequency with which these are deposited. The width of the growth band deposited during the shell deposition period is determined by the amount that the animal was able to enlarge its burrow during the preceding period of active boring. Growth band width increases with age and decreases with harder substrata. The duration of the growth interval increases with age and probably also with decreased availability of food.
Effects of Temperature and Photoperiod on Larval Development in Lestes Eurinus (Odonata: Lestidae)
Authors: Lutz Paul E.
Published: May 2006

Eight larval collections of the damselfly Lestes eurinus were made from October 1965 through May 1966. In each collection, eight groups of larvae were subjected to combinations of temperatures (15°, 20°, 25°, 30°C) and photoperiods (11 , 14 hr) until emergence. Using a unique lake facility, three additional groups of animals were subjected to 11—hr, 14—hr, and natural photoperiods all at natural temperatures. At every temperature, larvae completed their development more rapidly when subjected to the 14—hr day. The greatest differences in photoperiodic responses were observed at 20°C. In general, rates of larval responses were progressively faster at higher temperatures, but higher temperatures (25°C, 30°C) did not induce a faster rate for long—day animals. Both field and laboratory observations indicated that each of the later instars had a higher thermal coefficient for growth than that of the preceding instar. Rising vernal water temperatures induced a degree of synchrony into molting and emergence, and were, collectively, a most important factor in seasonal regulation. Quantitative data are presented for the first time in support of Corbet's LTT hypothesis of seasonal regulation in a summer species of Odonata. The separate and combined effects of temperature, photoperiod, and degree of maturity on the developmental rate of larvae are discussed.
Marking Insects with Dietary Manganese for Detection by Neutron Activation
Authors: Monro John
Published: May 2006

Pupal Mediterranean fruit—fly (eratits capitata Wied) showed different manganese contents as a result of different natural concentrations of manganese in the larval diet. Adults were marked by feeding the larvae on a diet containing 10—4 to 10—3 gm MnCl2/gm of medium. The marked adults were detected by the height of the 0.84 MeV gamma—ray peak following neutron activation. This method may be useful when large numbers of insects or other invertebrates are to be marked with a non—radioactive marker. Manganese (and other elements) may possibly be administered through food—plants for studies of dispersal.
A Quantitative Study of Foraging of Male and Female Spruce‐Woods Warblers
Authors: Morse Douglass H.
Published: May 2006

Males of four congeneric species of wood warblers (Parulidae) inhabiting a spruce forest of coastal Maine were found to forage higher than their females. They were the Magnolia (Dendroica Magnolia), Myrtle (D. coronata), Black—throat Green (D. virens), and Blackburnian (D. fusca) warblers. The foraging areas of males were nearer the height of their singing areas than were their nests, while foraging areas of females were nearer the height of their nest than the singing perches of their males. Very few differences were observed between sexes in the part of the tree utilized (proximal parts of limbs, tips of foliage, etc.) During the period of incubation, the foraging rates of females became noticeably greater than those of their males; before and after this period differences were less pronounced or non—existent. The partitioning of sexes results in a situation where males can forage readily while remaining maximally conspicuous, and females can forage in an area maximally adjacent to their nests. During this period males spent much of their time in territorial activities, females in nesting activities.
A Modified Shardakov Method for Determining the Osmotic Characteristics of Blood and Other Body Fluids
Authors: Soule Oscar H.
Published: May 2006

Application of the Shardakov method can ve made to partial or non—regulators from which measurable fluids are not available. This type of technique for measuring osmotic pressure of body fluids is also apparently the only method that can give these results without disturbing the intact biological system. If care is taken in selecting the bath concentrations, it is possible for the same animals to be used for other studies. The Shardakov method was used to detect changes in the concentration of the blood of anurans from different habitats. These variations are correlated with the relative aridity of the habitat and the ecology of the animals.
Notes on the Habitat of Microtus in Central Illinois
Authors: Lewin David C.
Published: May 2006

Studies on correlations between soil moisture and two species of Microtus in central Illinois show that M. pennsylvanicus is associated with wet habitat, whereas M. ochrogaster is found in dry habitat (P < .005). The data support Findley's (1954) hypothesis that competitive exclusion maintains vole separation in sympatric situations.
An Analysis of Variation Between Upland and Lowland Switchgrass, Panicum Virgatum L., in Central Oklahoma
Authors: Porter Clyde L.
Published: May 2006

Mass field collections and plants grown under various environmental conditions were analyzed to determine the extent of the morphological differences occurring between upland and lowland types of switchgrass, Panicum virgatum L., in McClain County, Oklahoma. The bases for these differences were also investigated. A comparison of field populations revealed differences in clonal habit, in the size of clones, and in the gross morphology of their vegetative organs. Lowland plants were larger in most aspects than those of upland areas although the differences between them were somewhat nullified by variations within each of the two types. Genetically controlled morphological differences became evident when the effects of environmental differences were eliminated. Although upland and lowland switchgrasses were somewhat modified under common greenhouse conditions, they exhibited essentially the same morphological differences as did field populations. A physiological difference in water requirement also occurred between the two types. Lowland switchgrass grew best under flooded conditions, whereas upland plants reached their greatest development under more moderate conditions of soil water. The morphological differences between field populations occurred largely, therefore, as a result of the morphological expression of this physiological difference in water requirement which was superimposed on lesser genetic differences. Upland and lowland switchgrasses also differed in their requirement for nitrogen, the latter having a somewhat lower requirement than the former. This factor probably did not contribute significantly to the existing morphological differences. The results of reciprocal transplants substantiated these conclusions. Plants of the lowland type were tetraploids. Hexaploids and octoploids occurred in the upland with hexaploids being the most common.
Food Specialization in Conus in Hawaii and California
Authors: Kohn Alan J.
Published: May 2006

The 6—11 vermivorous species of the marine gastropod genus Conus co—occurring on Hawaiian coral reefs and intertidal benches have specialized diets, as measured by prey species redundancy; each feed primarily on a different species, or group of species. In contrast, C. californicus has no co—occurring as potential competitors for food and its diet, comprising members of six classes in four animal phyla, is the most diverse known for any species of Conus. Prey species redundancy of the one common molluscivorous species in Hawaii is intermediate between values for the Hawaiian vermivores and C. californicus.
Influence of Ponderosa Pine on Herbaceous Vegetation
Authors: Moir William H.
Published: May 2006

Field and experimental data from Spokane, Washington, suggest that ponderosa pine clusters past the seedling stage adversely modify the herbaceous environment during their subsequent development. Indications of herb suppression appear early in the development of pine clusters, especially in the dense sapling stages. Increased light interception by the pine canopies and the poorer soil nitrogen supply under trees act together in bringing about a decline in herb populations. This decline is first indicated by reduced inflorescence production of grass species and later by lessened canopy coverage of the ground vegetation. Continued tree development unchecked by fire or artificial thinning appears to lead toward total or near—total herb suppression.
Reproduction in the Arenicolous Lizard Uma Notata
Authors: Mayhew Wilbur W.
Published: May 2006

Specimens of the sand—dwelling lizard, Uma notata, were collected monthly, primarily in the Algodones Dunes, Imperial County, California, from July 1958 through September 1962. These animals were autopsied to determine the breeding cycle of both sexes. Most individuals reach reproductive maturity during the second summer following hatching. Adult testis volumes change markedly during the year, generally reaching maximum size in May. Males were found as potential breeders from mid—April to mid—September. Females were found with eggs (usually two) in oviducts from mid—May to the late August. Females probably lay more than one clutch per year, based on observations of egg—laying captives. The reproductive period yields slightly from year to year due, at least in part, to the amount of rainfall that occurs the preceding winter. Breeding activity in males and the emergence of juveniles are delayed following dry winters. This is attributed to a series of interactions between organisms. U. notata tests do not become reproductively active if the lizards do not obtain adequate food. Insects that live in low—growing plants (annuals) normally are used for food by these lizards. However, insects that develop on these plants can do so only if sufficient rainfall occurs in winter to produce annuals. On the other hand, the larger plants (perennials) in the dunes acquire sufficient moisture from deep in the sand to flower each year, regardless of winter rains. Consequently, insects that utilize perennials are relatively plentiful every year. Following dry winters, Uma must rely on obtaining sufficient food from these insects, which presumably are more difficult to capture by sand—dwelling lizards. Thus, breeding activity is delayed until the requisite amount of food can be acquired. The reproductive responses of Urosaurus graciosus, a lizard that lives in perennial plants on these dunes, support this explanation.
Feeding Ecology of the Red‐Backed Sandpiper (Calidris Alpina) in Arctic Alaska
Authors: Holmes Richard T.
Published: May 2006

Shore birds are important trophic components of tundra communities during summer months, preying chiefly on insects. The Red—backed Sandpiper (C. alpina), studied in five seasons near Barrow, Alaska, 71°N, feeds largely on larvae and adults of the families Tipulidae and Chironomidae (Diptera). Sampling for availability and abundance of insect populations shows that the food source readily available and heavily used in early summer and again in late summer consists of tipulid larvae; as summer predation proceeds, important changes in numbers, and availability of different food species result from progression of their life—cycle stages and from changes in environmental conditions. Food supply and diet are most varied in July. Although feeding behavior and diet of redbacks change with prey availability, preferences are shown by adult sandpipers for tipulid larvae in early and late summer and to a lesser extent for chironomid larvae in midseason. Recently hatched young feed entirely on small—sized adult insects, mostly chironomid flies, which are obtained easily on the tundra surface. Differences between adult and young redbacks in habitat and food selection during late summer represent an intrapopulational means of apportioning food supply in a critical part of the season. With arctic insect faunas depauperate in variety of taxa, there is a limited diversity of food species for sandpipers. Adverse weather conditions characteristic of high—latitude climates can cause local food shortages. Interacting with the timing of generation replacement of important insect prey species, adverse weather promotes the widest variations in food conditions in July when young sandpipers are hatching and growing.
A Reformulation of Alternative (b) of the Broken Stick Model of Species Abundance
Authors: Vandermeer John H. , MacArthur Robert H.
Published: May 2006

A corrected formula for alternative (b) of MacArthur's broken stick species—abundance model is described and discussed.
Distributional Patterns in Assemblages of Attached Diatoms from Yaquina Estuary, Oregon
Authors: McIntire C. David , Overton W. Scott
Published: May 2006

Summer and winter distributional patterns of attached diatoms were investigated in Yaquina Bay and estuary, Oregon. Differences in species composition and diversity of diatom assemblages at selected stations from fresh water just below Elk City, Oregon, to the marine waters of lower Yaquina Bay were released to environmental gradients. A total of 16,475 diatoms from 30 samples was separated into 256 species and varieties, of which 97 were found in only one sample, and 72 were represented by a single individual. The most abundant diatoms in the August samples were Fragilaria striatual var. californica, Melosira moniliformis, M. nummuloides, Navicula mutica, and Synedra fasciculata, while in the February samples Achnanthes no.2 and no.4, Navicula diserta, N. mutica, and Nitzschia frustulum var. perpusilla were dominant. Of the most abundant taxa, Navicula no. 2, N. diserta, N. gregaria, Nitzschia frustulum var. perpusilla, Synedra fasciculata and Thalassionema nitzschioides were the most evely distributed among the stations. The mean species diversity for diatom assemblages sampled in February was slightly higher than for assemblages collected in August. In February the mean specific diversity within a genus was higher and the mean generic diversity slightly lower than in August. In general, differences in assemblages were closely related horizontally to the salinity gradient and vertically to the desiccation and insolation gradients. However, biological factors were more important in accounting for differences among assemblages in the summer than in the winter and these factors were primarily species interactions between diatoms and macro—algae.
Drought Relationships and Distribution of Two Mediterranean‐Climate California Plant Communities
Authors: Harrison A. T. , Small E. , Mooney H. A.
Published: May 2006

The summer drought—deciduous coastal sage in Southern California near Los Angeles has a bimodal, coastal and interior, distribution at low elevations (sea level to 300 m), whereas the evergreen sclerophyllous chaparral is developed at higher elevations. Winter rainfall is 300—350 mm at the low elevations and 500—600 mm at the higher altitudes. Photosynthesis and transpiration in response to artificial drying were examined in field—collected leaves of species from the two vegetation types. The fully hydrated mesomorphic leaves of the coastal sage species had initially higher photosynthesis and transpiration rates which declined rapidly during the first 20—30 min of drying, presumably because of hydroactive stomatal closure. At zero net photosynthesis cuticular loss of water was high, nearly 25% of the maximum rate for these species. In the chaparral species photosynthesis and transpiration rates were one—fourth to one—third those of the coastal sage species. Decline of rates with drying time was not nearly as rapid. Net photosynthesis continued at 20—30% of maximum after 70—80 min with lower cuticular losses of water vapor. During cool spring periods with sufficient soil moisture, high transpiration and assimilation rates allow for rapid growth, flowering, and fruiting in plants of the coastal sage community. They are drought—evading by virtue of their summer deciduous habit and are better adapted to prolonged summer drought in areas of low rainfall. Chaparral species, at slightly higher altitudes with higher precipitation and with deeper and more extensive root systems and xeromorphic leaf characteristics, are less sensitive to conditions of high evaporative demand and can maintain net assimilation, although low at times, throughout the long summer drought period.
Effect of Paloverde (Cercidium) Trees on the Radiation Flux at Ground Level in the Sonoran Desert in Winter
Authors: Lowe Charles H. , Hinds David S.
Published: May 2006

The radiation flux at winter solstice is reported for desert microenvironments under Cercidium crowns and in open desert. In addition to the net radiation flux and that of the upper and lower hemispheres, hourly radiation temperatures (equivalent black—body temperatures) were measured for soil surfaces, sky, and tree crowns. Radiation temperature—time as a limiting factor for organisms in the sense of resistance time was investigated. Winter environmental modification provided by Cercidium of 4—5 m height is large, and greater than expected. The effective (net) incoming radiation at ground level at midday in the open is more than twice that under the paloverde, and the effective (net) outgoing radiation in the open at night is more than twice as great as that under the tree. For these data, a computer model of the energy budget of a 1—kg hypothetical homoiotherm predicts (i) on the ground surface under the paloverde at night, an effective body—surface temperature of 7 degrees C with an increse of metabolic rate by only 2.6 times its standard rate; this is in sharp contrast to (ii) in the open under the night sky and on a colder ground surface, where the metabolic rate of the same animal exhibiting Newtonian cooling would have to be increased 6.2 times to balance its heat budget. The model also predicts little or no presence in the open on the ground during winter nights in the desert for small homoiotherms greatly less than 1 kg body weight, e.g., weights on the order of 100—200 g or less, unless for rapid forays of short duration.
Seasonal Calorific Values from a Deciduous Woodland in England
Authors: Hughes Malcolm K.
Published: May 2006

In a deciduous woodland in England ground—vegetation calorific values (4.158—4.517 Kcal/g ash—free weight) were lower than those for the tree wood (4.565—5.211 Kcal/g ash—free weight) and canopy leaves (4.632—5.635 Kcal/g ash—free weight). Ground—vegetation litter had lower calorific values (4.387—4.772 Kcal/g ash—free dry weight) than canopy litter on the forest floor (4.814—5.229 Kcal/g ash—free weight) and falling canopy litter (5.088—5.389 Kcal/g ash—free weight). Canopy leaf calorific values fell by all up to 11.5% during the summer, and other components showed seasonal changes relevant to consumer studies. Falling leaves had higher calorific content than autumn canopy leaves. Thus leaf production should be measured as litter fall, not standing crop.
A Two‐Compartment, Three‐Parameter Model for the Absorption and Retention of Ingested Elements by Animals
Authors: Goldstein Robert A. , Elwood Jerry W.
Published: May 2006

In many experiments on the absorption and retention of ingested elements, the measured retention curve is fitted to the sum of two exponential functions. The model used most often to interpret results assumes that the instantaneous rate of absorption of an element is proportional to its instantaneous rate of ingestion. The authors propose instead a model that assumes the instantaneous rate of absorption is proportional to the amount of unabsorbed element in the gut. The models lead to different interpretations of the parameters of the retention curve and to different functional descriptions of the accumulation of absorbed element in the body. Data are presented to support the author's proposed model over the commonly used model. Since both models are of equal mathematical complexity, there is no justification for favoring the commonly used model. Suggestions are made about how modeling should be incorporated into ecological studies. Models based on meaningful and testable hypotheses should be formulated prior to data collection.
Microtus Population Biology: Demographic Changes in Fluctuating Populations of M. Ochrogaster and M. Pennsylvanicus in Southern Indiana
Authors: Krebs Charles J. , Keller Barry L. , Tamarin Robert H.
Published: May 2006

Microtus pennsylvanicus and M. ochrogaster are sympatric in southern Indiana grasslands. From June 1965 to August 1967 four populations were lived trapped, three of them in 0.8—hectare (2—acre) outdoor pens. Both species increased during 1965 and reached peak densities in summer 1966. Microtus ochrogaster declined abruptly that fall and remained low; M. pennsylvanicus declined the following spring. One of the fenced populations increased to a density about three times that of its unfenced control. By early fall 1966 it had nearly destroyed its food resources and then suffered a severe decline associated with obvious overgrazing and starvation. No such overgrazing has been seen on any unfenced grasslands in this area. Dispersal is probably necessary for normal population regulation in these voles, since fenced populations seem unable to regulate their density below the limit set by starvation. Both species bred extensively in the winter of 1965—66 during the phase of population increase. There was little or no breeding during the winter after the peak. Survival of females in the trappable population of both species was high and relatively constant until the end of the cycle. In males, periods of low survival punctuated the increase and peak phases, and these periods of low male survival did not occur at the same time in the two Microtus species. Some mortality processes are thus highly specific for sex and species. In the fenced populations survival rates were very high and no sporadic male losses occurred. Increasing and peak populations of M. pennsylvanicus and M. ochrogaster are characterized by adults of large body size. During the increase and peak phases some voles stopped growing at low weights (30—40 g) while others reached high asymptotic weights (45—55 g). The demography of these Microtus species in southern Indiana is similar to that of other cycle voles and lemmings in temperate and arctic areas.
Pertinent Stimuli for Habitat Selection by the Juvenile Manini, Acanthurus Triostegus Sandvicensis
Authors: Sale Peter F.
Published: May 2006

Distribution of juvenile manini in tide—pools and on reef flats was significantly correlated with water depth and with cover availability. Substratum type, degree of water movement, and presence of conspecifics were also of potential value as stimuli for habitat selection, but water temperature, salinity, and oxygen content were eliminated as possible cues. Laboratory experiments were conducted testing the responses of juvenile manini to light intensity and direction, to substratum texture and color, to the presence of conspecifics, to variations in degree of water movement, and to presence of food algae. Habitat selection by manini was primarily a response towards a substratum containing suitable food and cover, in a depth of water appropriate to the size of the individual fish. Degree of water movement and presence of conspecifics had a minor influence on the selection process.
Distribution of Fine Roots in Three Pinus Radiata Plantations Near Canberra, Australia
Authors: Moir W. H. , Bachelard E. P.
Published: May 2006

Frequency distributions of fine roots (0.4—3—mm diameter) at 0—1.5— and 1.5—3—dm soil depths within 1958, 1948, and 1934 plantings of Pinus radiata D. Don, were obtained by soil coring and root extraction by wet sieving, but two other methods gave different results and were less sensitive to possible differences between stands. Fine roots perfuse the 0—1.5—dm soil depth in all stands and are significantly less abundant at 1.5—3 dm. Spatial variation of roots within the stands was independent of the proximity of pine stems. Roots extracted from cores by wet sieving had a bimodal frequency distribution in the 1948 and 1958 plantings. Fine roots can be further categorized into very fine roots having rapid turnover rates and fine roots which may eventually grow into diameter classes over 3 mm. The frequency distributions obtained by random or systematic sampling methods were compared by non—parametric tests and were not significantly different.
Some Vegetation and Sil Characteristics of Mountain Grasslands in Central Idaho
Authors: Mueggler W. F. , Harris C. A.
Published: May 2006

Vegetation and soils were evaluated on 23 relatively undisturbed grasslands scattered throughout the mountainous region of central Idaho. Analyses by ordination and cluster techniques suggest existence of at least two classifiable communities; (1) the Agropyron—Melica community, which includes an abundance of native annuals and relatively few perennial species; and (2) the Festuca—Agropyron—Antennaria community, which includes few annuals but numerous perennials, among which mat—forming species are conspicuous. Several of these grasslands were considered transitional. Some site characteristics differed considerably between the two communities. Herbage production varied greatly; it was greatest on north exposures and on soils having high water—holding capacity. Production of grasses and sedges generally doubled that of forbs. Shrubs were a minor component.
Distribution of Fungi in a Waste‐Stabilization Pond System
Authors: Cooke Wm. Bridge , Matsuura George S.
Published: May 2006

Fungus populations in a small waste—stabilization pond system near Lebanon, Ohio, were determined using a number of plating and enrichment culture techniques. Throughout the system, and in an adjacent stream, 212 species of filamentous fungi and yeasts were recovered. Before the system was placed in operation, few filamentous fungi and no yeasts were recovered from samples of bare soil, while after a year's operation, numbers of species increased fivefold and numbers of colonies counted increased nearly 200—fold. Additional numbers of yeasts and filamentous fungi in pond waters and sludges were present but were not sampled quantitatively. Except for November, when adverse conditions of undetermined nature reduced the fungal populations, the numbers of viable cells recovered indicate a favorable habitat for fungi. It appears certain that fungi can be counted among those saprobic organisms that play a part in the degradation and thus the removal of organic wastes from the waters of waste—stabilization ponds.
Plant Succession on the Sand Dunes of the Oregon Coast
Authors: Kumler M. L.
Published: May 2006

Parabolic sand dune succession was studied on 48 plots within a 150—mile section of the Oregon coastline. The sand dune communities were described and related to their successional sequence. Both plot and plotless techniques were used to obtain data for frequency, density, cover, and dominance. Successional stages of upland areas of coastal sand dune were represented by nine communities of plants which ranged from scattered, pioneer, herbaceous plants on barren, shifting sand to the near—climax, physical—biological system–the dune forest. The stands included a pioneer stage consisting of herbaceous plants which appeared early on the unstabilized dunes. A second community made up of many annual and some perennial herbaceous plants emerged on protected, lee slopes along the edges of dunes supporting pioneer communities. The third community located on somewhat stabilized sand was produced by a merging of some of the more hardy herbaceous plants from the second community, and the appearance of some shrubs also found in the following community. The fourth community was located on sites of stabilized sand and consisted mainly of shrubs. The remaining five communities, containing trees and shrubs on stabilized sand, were Pinus contorta—shrub; Pinus—Picea—shrub; Picea sitchensis—shrub; Picea—Tsuga—shrub; and Tsuga heterophylla—shrub. Many of the dominant species gradually declined as the succession proceeded from one community to another and other dominants appeared. The most notable exception to this progression occurred in the herbaceous community along the lee edges of the initial dunes, where the vegetational changes were much more abrupt.
Differences in the Life Tables of Tropical and Temperate Milkweed Bugs, Genus Oncopeltus (Hemiptera:Lygaeidae)
Authors: Landahl John T. , Root Richard B.
Published: May 2006

The life tables of Oncopeltus fasciatus from a temperate locality (Ithaca, New York) and O. unifasciatellus from a tropical locality (Cali, Columbia) are compared. When reared under controlled conditions approximating those they experience during the summer in their natural environments, the two species exhibit remarkably similar rates of development and mortality. The temperate species, however, which begins ovipositing sooner and produces more eggs, has a higher instantaneous rate of population increase (r). These results extend some theories advanced to explain latitudinal differences in the clutch size of birds.
Effect on Leaching on Pine Litter Decomposition Rate
Authors: Kowal Norman Edward
Published: May 2006

Leached pine needles have a much higher decomposition rate than unleached ones. Under laboratory conditions, the measurement of carbon dioxide production yields a close estimate of decomposition rate as measured by weight loss.
Populational Variation in Germination of Weedy Species
Authors: Palmblad Ivan G.
Published: May 2006

Germination tests were conducted on seed from individual plants and from bulk samples representing 174 populations and 105 species to survey the prevalence of germination polymorphism in flowering plants in Utah and surrounding areas. Twenty—two populations representing 15 species (about 1/8 of the populations sampled) exhibited polymorphism, as measured by the germination of seed from individuals of percentages significantly different from those of bulk samples. Several of the 15 species, including Bromus tectorum, Rumex crispus, and Amaranthus retroflexus, were represented by populations with germination polymorphism and by populations without it.
Dispersal Responses of Female Flour Beetles, Tribolium Confusum, to Presence of Larvae
Authors: Naylor Alfred F.
Published: May 2006

By offering female Tribolium confusum a choice of flour occupied or not occupied by larvae of the species, an avoidance response was demonstrated. The response was intensified by increasing larval density in occupied flour. Larvae showed a sporadic density—dependent tendency to leave flour.
Physiological Effect of Botfly Parasitism on Meadow Voles
Authors: Clough Garrett C.
Published: May 2006

Botflies of the genus Cuterebra were found infesting a population of meadow voles, Microtus pennsylvanicus, in three out of five years during the months of July, August or September. Maximum incidence was 45% in August. The number and position of larvae on the hosts is described. Infested voles had lighter thymus glands and heavier spleens than noninfested voles but survival time in cold water was only slightly lower and adrenal weights were similar.
Gamma‐Emitting Radionuclides in Alaskan Tundra Vegetation 1959, 1960, 1961
Authors: Rickard W. H. , Davis J. J. , Hanson W. C. , Watson D. G.
Published: May 2006

The gamma—emitting radionuclides derived from worldwide fallout were measured in samples of Arctic tundra vegetation collected from the Ogotoruk Valley, northwestern Alaska, during the summers of 1959, 1960, and 1961. Cerium—praseodymium—144 was the most abundant radionuclide measured during the 3 years of study. Smaller amounts of rutheniumrhodium—106, zirconium—niobium—95, cesium—137, manganese—54, and zinc—65 were also measured. Radioactivity of vegetation diminished from 1959 to 1961 primarily as a result of the decay of fallout radionuclides in the virtual absence of nuclear explosions in the earth's atmosphere. In 1961 the long—lived radionuclide cesium—137 contributed a larger percentage of total fallout radioactivity than it had in previous years. Lichens and mosses contained more radioactivity than their associated terrestrial vascular plants. Foliar interception appeared to be an important means of fallout accumulation. Terrestrial plants with persistent aboveground parts accumulated more cesium—137 than plants with more ephemeral aboveground parts. The lowest cesium—137 values were associated with aquatic emergent plants having aerially exposed parts for the shortest periods of time.
Seed Dormancy in the Alpine Rush, Luzula Spicata L.
Authors: Amen Ralph D.
Published: May 2006

A study of Luzula spicata seeds from the alpine tundra of the Colorado Front Range revealed complete dormancy due to a condition of the seed coat or endosperm. Dormancy appears to be related to the presence of a hard waxy layer (gelatinous sheath when imbibed) covering the entire seed surface. The only seed treatment effective in breaking dormancy in this species is scarification on the micropylar end of the seed. Some type of mechanical action on the seed coat apparently is necessary to elicit germination, presumably accomplished naturally by the abrasive action of soil particles (rather than by biotic action) but probably not until such time as the protective waxy or gelatinous buffer has been weathered away. Seeds from different alpine locations and collected in different years did not vary in the extent or degree of dormancy exhibited, nor did they vary significantly in their response to scarification and other treatments.
Phytoplankton Abundance and Primary Production Rates in Two Arctic Ponds
Authors: Kalff Jacob
Published: May 2006

Phytoplankton abundance and rates of primary production (C14), were studied at bidaily or tridaily intervals during two summers in two small Alaskan tundra ponds. The phytoplankton, composed largely of unicellular flagellates, numbered between 0.79 and over 100 X 106 cells per liter. Rarely did the percentage of cells smaller than 11μ fall below 75% of the total; net phytoplankton were negligible at all times. Annual carbon fixation during 1963 and 1964 was 380 mg/m2 (830 mg/m3) and 820 mg/m2 (2,000 mg/m3) in pond III and 670 mg C/m2 and 850 mg/m2 in pond II. Daily production, on the basis of a 140—day growing season in 1963 and 1964, averaged 2.6 and 5.9 mg/m2 respectively in pond III and 4.8 and 6.1 mg/m2 in pond II. Annual production rates are the lowest on record for fresh waters. Phytoplankton abundance and carbon fixation were, during a portion of the study, significantly correlated. Evidence was obtained that many of the phytoplankton were facultative heterotorphs and capable of supplementing autotrophic growth with heterotrophic growth under low light conditions.
Influence of Drought and Grasing on Mortality of Five West Texas Grasses
Authors: Box Thadis W.
Published: May 2006

Significantly more plants of silver bluestem (Andropogon saccharoides Swartz.), sideoats grama (Bouteloua curtipendula (Michx.) Torr.), sand lovegrass (Eragrostis trichodes (Nutt.) Nash), switchgrass (Panicum virgatum L.), and Indiangrass (Sorghastrum nutans (L.) Nash) died on Brownfield fine sand, eroded phase, grazed pastures, than on adjacent ungrazed areas, during a recent 4—year drought, although grazing pressure was light. The majority of ungrazed plants had either normal or hollow growth forms. Grazed plants commonly had only a small amount of living material along one edge. Size of clone and percentage of dead material in clones were positively correlated P <.01) in grazed sideoats grama and sand lovegrass plants and negatively related (P <.01) in ungrazed plants.
Germination of Eurotia Lanata in Relation to Temperature and Salinity
Authors: Workman John P. , West Neil E.
Published: May 2006

Seed collected from four native stands of winterfat (Eurotia lanata (Pursh) Moq.) in Utah were germinated at six levels of sodium chloride under two temperature regimes. Germination percentages differed significantly between seed sources and also between sodium chloride levels. Each seed source decreased in germination percentage as the sodium chloride level increased. The seed sources interacted significantly with sodium chloride levels and although not statistically significant, the seed source interaction with temperature also appears important. Genetic differences within the species enable some strains to germinate more successfully than other strains at certain levels of temperature and sodium chloride.