bluuebunny/crossref_metadata_2025 huggingface dataset:
Seasonal Variation in Standing Crop and Species Diversity of Insect Communities in a small Quebec Stream
Authors: Mackay Rosemary J. , Kalff J.
Published: May 2006

Seasonal changes in the distribution and abundance of insects species were studied in a small cool woodland stream where the primary food material was fallen leaves. Between March 1966 and March 1967, weekly quantitative samples were taken from sand, gravel, stone, leaf, and leaf detritus habitats. The number of insects per unit area of each habitat was least in sand and increased through gravel, stones, leaves, and detritus. Biomass per unit area was least in gravel and increased through detritus, sand, leaves, and stone. The annual standing crop of the stream as a whole was approximately 3,000 insects/m2 and 2 g/m2 (dry wt.). The number of insect species in any one habitat varied according to apparent spatial heterogeneity of the environment, to substrate stability, and to food resources. Leaves supported the highest number of species (92), sand the least (61). Species diversity was higher during summer and winter than during spring and autumn. When compared with other aquatic environments, the bottom fauna of the stream has oligotrophic features, including a large number of species and an annual standing crop of poor to intermediate richness.
Aspects of the Limnology of an Endorheic African Lake (L. Chilwa, Malawi)
Authors: Moss Brian , Moss Joyce
Published: May 2006

Owing to relatively low rainfall during the past few years, Lake Chilwa (15°S, 36°E), lake with internal drainage, is on the verge of complete drying out. The results of chemical and biological investigations undertaken whilst water was available are presented. A fluctuation between high dry season and lower wet season levels of major ions was found. It is likely that salts in the lake originated primarily from salt springs, rather than from evaporation of inflowing river water. Inorganic phosphate and nitrate were sometimes not detectable in the water, but were released in large quantities following flooding of the marginal mud—flat. The lake was classified as moderately saline (Class II, Talling and Talling 1965) in 1966/67, but as a result of evaporation salinity and alkalinity increased sufficiently for it to become a Class III lake in 1967/68. At high water levels fish production was high, possibly as a result of extensive digestible diatom crops on the sediment surface. Factors limiting primary productivity included light intensity, as a result of high turbidity and water color, and low levels of nitrate.
Growth Form and Distribution of Vine Maple (Acer Cirinatum) on Marys Peak, Western Oregon
Authors: Anderson H. G.
Published: May 2006

Vine maple growth form and distribution differ between plant communities. Most stems are erect in the high elevation Pseudotsuga/Acer/Gaultheria community, whereas crown spread, bryophyte cover, height, and diameter attain a maximum in the Pseudotsuga/Acer/Polystichum community. Layering is primarily responsible for the distribution of vine maple and can only occur where the stems become arched and contact the ground. On slopes exceeding 30% most stems lean down or across the slope. In some communities upslone movement of vine maple is restricted because of repeated fires and the step slope which limits layering.
A Measure of Culture‐Induced Changes In a Laboratory Population of Protozoa
Authors: Salt George W.
Published: May 2006

Continued maintenance of organisms in laboratory cultures may produce stocks which differ in some degree from wild populations of the same species. Comparison of laboratory and wild populations of Woodruffia metabolica, a predatory ciliate, provides a measure of the effect. After an estimated 1,000—1,500 generations in laboratory culture, "domesticated" Woodruffia consumed the same number of prey organisms (Paramecium aurelia) per generation but increased at only 2/3 the rate of wild Woodruffia. After 7 months of laboratory cultivation, the wild Woodruffia's rate of increase decreased by 10% (not statistically significant). The precise means whereby the difference resulting from laboratory culture is brought about cannot be identified with certainty. However, existence of such a different leads to the conclusion that if laboratory studies are intended to explain quantitative phenomena in wild populations, experiments should be conducted as nearly as possible on organisms freshly caught in the wild.
Ecological Relations of Three Atta Species in Panama
Authors: Weber Neal A.
Published: May 2006

Of the three Atta species of Panama (sexdens L., cephalotes isthmicola Weber and colonzbica tonsipes Santschi), sexdens is a grassland species as it is in South America, and the other two are forest or forest‐grassland ecotone species. While sexdens and tonsipes may nest in the same general grassy area, sexdens extends along the sandy Pacific shore, and the other two nest primarily in clay. A unique relationship in the heart of the city of Colon on the Atlantic side was a colony of isthnzicola surrounded by colonies of tonsipes. Their leaf‐bearing files were separate and they were mutually hostile. The main plaza of Panama City on the Pacific side has been occupied by sexdens despite the gradual extinguishing of foraging areas by buildings. Barro Colorado Island has isthmicola and tonsipes occupying similar habitats. Personal records since 1938 are noted. Usually the species of the leaf‐cutting ant, Atta, occupy well‐defined and separate areas (Fig. 1) throughout their range from Texas and Louisiana to Argentina and Uruguay. The gap between texana Buckley in Texas and the northernmost extent of mexicana F. Smith in Arizona is several hundred miles wide. In Uruguay sexdens L. is found to the north and on the rolling pampas while vollcnweideri Forel is found only close to the Rio Uruguay, according to Carbonnel (pers. commun.). The much closer relations of sexdens and cephalotes L. in Brazil have been described by Borgmeier (1959) and Goncalves (1960), and in Guyana and Venezuela in Weber 1946, and 1947. There is generally a well‐defined ecological difference, sexdens being found in grassland or the grassland‐forest ecotone and cephalotes occurring in the forest. In Guyana sexdens seemed more an ant of sandy soil and cephalotes an ant of clay, but this is not always consistent. The three species of Panama (Weber 1941, 1956, 1968) are sexdens, cephalotes isthmicola Weber and colombica tonsipes Santschi (Fig. 2). It should not be assumed that the ranges of any Atta are stabilized. All fluctuate with changes in climate and for more obscure reasons. In part it may be that the species and the genus have evolved in relatively recent times compared with such genera as Myrmicocrypta and Sericomyrmex. They clearly have more flexibility in meeting climatic change.
Diversity in Terrestrial Cave Communities
Authors: Poulson Thomal L. , Culver David C.
Published: May 2006

Local species diversity of terrestrial arthropods was determined from a combination of trapping and census in an area of variable passage type in Flint Ridge Cave System in Mammoth Cave National Park, Kentucky. We measured evaporative rate, substrate moisture, substrate organic content, predictability and stability of food and microclimate, substrate diversity, and intensity of flooding. We found significant correlations of species diversity with substrate diversity, substrate organic content, and intensity of flooding.
Egg Hatching and Life History of a Fairy Shrimp Branchinecta Mackini Dexter (Crustacea: Anostraca) in a Mohave Desert Playa (Rabbit Dry Lake)
Authors: Brown Lon R. , Carpelan Lars H.
Published: May 2006

Observations on populations of Branchinecta mackini in temporary ponds, which last for as little as 3 days to as long as 4 months, on a desert playa showed that hatching of dehydrated cysts (eggs) follows initial entry of water into the basin if salinity remains low. Salinity ranges from an initial 0.5% to as much as 34% as the pond evaporates. Hatching is continuous at constant low salinity, but since salinity general increases rapidly, initial hatch is usually of short duration. Additional periods of hatching follow further inflows of water or after meeting of ice, that is, after reductions in salinity. The duration of hatching is inversely proportional to rate on increase in salinity. When salinity of small—volume summer ponds increases at rates above 500 ppm (1,000 (mu)mhos) per day, three in virtual inhibition of hatching. Laboratory studies showed that egg hatching was controlled by both salinity and oxygen operating in various combinations to inhibit or stimulate hatch. The hatching characteristics obtained from laboratory cultures after ejection from ovisacs of living females. The finding that a salinity—oxygen complex regulates hatching in a desert pond permits tentative explanation of a difference between branchiopods of humid and arid regions. In both cases the branchiopods are characteristic of astatic waters, and stimulation of the egg to hatch must be by some factor that changes at the time or origin of the temporary pond. In humid regions the factors of concern are temperature and oxygen. If the water undergoes significant changes in salinity, as it does in arid regions, control of egg hatch may be by both salinity and oxygen, with temperature limited to control of rate of development.
Relationships Between Derived Vegetation Gradients and Measured Environmental Variables in Saskatchewan Wetlands
Authors: Walker B. H. , Wehrhahn C. F.
Published: May 2006

Thirty—four relatively undisturbed stands of vegetation in shallow marsh, nonto slightly saline wetlands in south—central Saskatchewan were examined with respect to environmental influence on species distribution. Four environmental gradients account for the bulk of variation in the vegetation in the vegetation. They are, in decreasing order of importance, disturbance (despite the fact that all stands chosen are relatively undisturbed), available nutrients, water regime, and salinity. The greatest variation in the data from these stands as a whole is in their salinity, but this is not reflected in the vegetation. The correlation between water regime and available nutrients is negative. A number of other factors show minor correlations with the vegetation and with each other. The method of application of principal components analysis used in this study was a valuable aid in the interpretation of the data. It provides estimates of the proportions of (1) the variance associated with each principal component and (2) the total variation in the vegetation data that can be assigned to variation in the environmental measurements.
The Shelter‐Related Behavior of the Losbter, Homarus Americanus
Authors: Cobb J. Stanley
Published: May 2006

Some of the relationships between a lobster (Homarus americanus) and the dimensions of its shelter have been examined. Field studies showed that lobsters generally occupied shelters in which the height was less than the width, and that there was a correlation between lobster size and shelter size. In the laboratory lobsters chose low profile shelters when given a choice of flat (height = ½ width) versus square (height = width) profile openings. Back doors were often present in the field, and laboratory experiments suggested that some sort of constriction before the rear opening was necessary to qualify it as a back door. The amount of time spent in eight opaque or transparent shelter under bright, dim, and dark illumination was measured. In bright and dim light with opaque shelter, lobsters spent significantly more time in a shelter than in the other treatments, showing darkness to be major factor in shelter selection. Shelters are excavated by pushing sand or gravel with the third maxillipeds in a bulldozing motion or by digging with the first two or three pairs of walking legs, followed by a vigorous fanning of the pleopods.
Biomass Dynamics in a Moose Population
Authors: Jordan Peter A. , Botkin Daniel B. , Wolfe Michael L.
Published: May 2006

From a simple model, we have calculated with a digital computer the standing crop, the gains in weight (secondary production), and the transfer of biomass by death (potential food for predators) on a monthly basis for all age and sex categories of the Isle Royale moose, a population unhunted by man and in equilibrium with its predator, the timber wolf. These estimates provide a more accurate and detailed picture than available before of biomass dynamics in a wild ungulate population. For this single—prey—single—predator system, results demonstrate that the accumulation of biomass in the prey population permits a steady flow of food to the predator, although production of food for the prey (woody and aquatic vegetation) is seasonally highly cyclic. The storage of biomass is examined in terms of the year classes of moose. Further uses of the model are discussed.
Cladoceran Faunas Associated with Aquatic Macrophytes in Some Lakes in Northwestern Minnesota
Authors: Quade Henry W.
Published: May 2006

The cladoceran faunas associated with 12 species of aquatic macrophytes were studied to determine if the Cladocera showed community preference to specific plants. Almost 3,000 specimens belonging to 38 species of Cladocera were counted. Forty—two collections were made in seven lakes near Lake Itasca (N.W. Minnesota). SCUBA was used to select appropriate single—species stands of the 12 plants. When all collections from each species of plant were summed from all seven lakes, some grouping was evident. The cladoceran communities resulted in a breakdown of the plants into five groups. These were broad—leaved submersed, fine—leaved submersed, floating—leaved, Chara, and others. Water depth and sediment type did not seem to determine the distribution of those plant groups that showed specific cladoceran associations. When all cladoceran collections from a single lake were grouped the two limnologically most similar lakes showed quite different cladoceran faunas. Two measurements of community type, namely coefficient of community and per cent similarity, were calculated with the latter giving better results. These measurements supported the hypothesis that aquatic macrophytes control the distribution of the littoral Cladocera.
Translocation of C^(14)‐Labeled Compounds in Mycorrhizae and It Implications in Interplant Nutrient Cycling
Authors: Reid C. P. P. , Woods Frank W.
Published: May 2006

Loblolly pine (Pinus taeda L.) seedlings were grown axenically in mycorrhizae synthesis cultures with either the symbiont Pisolithus tinctorius (Pers.) Coker and Couch or Thelephora terrestris (Ehrh.) Fr. Glassware was designed to allow synthesis of mycorrhizae on two seedlings physically separated except for a bridge formed between the two root systems by mycorrhizal fungus mycelium. Glucose—C14 and sucrose—C14 were used as tracers to investigate movement of labeled compounds from mycorrhizal roots to external mycelium, from external mycelium to roots and from one root system to the other via shared mycelium. Whether applied to foliage as glucose—C14 or sucrose—C14, C14 was readily translocated to pine roots. Transport of C14 from mycorrhizal roots to external hyphae of T. terrestris up to a distance of 12 cm was shown, but only slight movement of C14 occurred into external hyphae of P. tinctorius. The introduction of glucose—C14 and sucrose—C14 to isolated strands of T. terrestris resulted in the movement of C14 from strands to roots. Movement of isotope from one seedling to the other via mutually—shared mycelium did not occur in the synthesis cultures; however, C14 movement between root systems artifically linked by mycelial strands indicated that interplant exchange can take place. Evidence suggests that mycorrhizal fungi such as T. terrestris could be effective in the exchange of organic and possibly other materials between root systems in an ecosystem.
Feeding by Paracoenia and Ephydra (Diptera> Ephydridae) on the Microorganisms of Hot Springs
Authors: Brock M. Louise , Wiegert Richard G. , Brock Thomas D.
Published: May 2006

Adult and larval ephydrid flies feed upon the microorganisms which colonize the effluents of hot springs, whereas the dolichopodid flies associated with them are not consumers of microorganisms, but are predators. Field observations were confirmed by radio—active isotope experiments differential extraction of radioactivity and assay of chlorophyll and proteins show that C14—labeled algae and bacteria are consumed and assimilated by the ephydrid insects. The natural history of these insects and their possible role in mineralization is also discussed.
Radiosonde Data for Characterization of a Mountain Environment in British Columbia
Authors: Peterson Everett B.
Published: May 2006

Thermograph records of the frequency of freezing and sub—freezing temperatures at altitudes of 3,200 ft (975 m) and 4,000 ft (1,219 m) on a mountain slope were compared with published radiosonde data of the same parameter from the same altitudes in the atmosphere. In winter on the windward side of the Coast Mountains of southern British Columbia radiosonde readings from offshore can form the basis of a reliable climatology of the freezing level.
An Ordination Technique Based on the Best Possible Stand‐Defined Axes and Its Application to Vegetational Analysis
Authors: Swan J. M. A. , Dix R. L. , Wehrhahn C. F.
Published: May 2006

An ordination technique for the analysis of vegetation data is described. The procedure resembles the Wisconsin method in the use of stands to define axes and Beals' formula to calculate stand axis positions. Differences from the Wisconsin method are: (1) axes are spatially related in a geometrically acceptable manner and (2) the best possible stand—defined axes are objectively selected. The method is simpler to understand than principal components "factor" analysis, and much less computation is required if there are many species in the data. Without modification of the method, a three—dimensional ordination was obtained for each of three sets of data, two from the North American prairies and one from the Canadian boreal forest. Hence, the technique objectively selects axes from "real" data in accordance with its design, but as yet we cannot say how effective it is in the display and interpretation of species interrelationships.
One Hundred and Thirty Years of Plant Succession in a Southeastern Wisconsin Lowland
Authors: Vogl Richard J.
Published: May 2006

The post—glacial history of a marl and peat marsh contained evidence that early hydrarch succession may have been relatively rapid due to higher plant as well as invertebrate animal productivity. Pristine open marsh, sedge meadow, and wet prairie were held in quasi—equilibrium by alternations of floods during wet periods and fires during drought. Fires either checked terrestrial advancement or turned it back to earlier aquatic stages by organic substrate removal. Recent fire control and continued lowering of water levels hastened intermediate hydrarch succession by quickly and directly converting aquatic to terrestrial sites. A peat burn increased soil pH and soil nutrients, particularly the phosphates, and eliminated plant competition so that open marsh was immediately invaded by aspen forest, which if uninterrupted, will be converted to lowland hardwood forest. Recurring fires could perpetuate the sucker—sprouting aspen, but burning decadent aspen forest might originate true prairie. Although fire is usually catastrophic and retrogressive, it produced successional stability and even acted as a successional accelerator in this lowland.
Synchronized Life Cycles in the Orange‐Crowned Warbler and Its Mallophagan Parasites
Authors: Forster Mercedes S.
Published: May 2006

The purpose of this study was to determine the relationship in timing of important stages of the life cycles of mallophagen lice and the cycles of the subspecies of the Orange—crowned Warbler (Vermivora celata) which they parasitize. The timing of breeding in the mallophagans Ricinus picturatus and Menacanthus sp. coincides with the timing of breeding in the subspecies of host warbler, resulting in sufficient numbers of lice for transfer to the newly available juvenal warbler hosts. No eggs are laid during the periods of avain molt; any eggs present would be lost with the feathers as they are dropped. Breeding is very limited in the winter when reproductive effort would be wasteful; opportunities for dispersal are rare at this time, and birds are extremely efficient at keeping their numbers of lice at a minimum. Several lines of evidence suggest that the timing of breeding in R. picturatus and Menacanthus sp. is controlled by the reproductive hormones of V. celata. Hormones are available to these lice with feed on the blood of their host. Peak breeding in the louse populations coincides with peak production of reproductive hormones in avian populations and lasts only as long as the breeding season of the subspecies parasitized. Juvenal birds which are not producing great quantities or reproductive hormones never carry louse eggs. During the fall molt periods, the gonads are in a refractory state and produce a minimum amount of reproductive hormones. During the late fall and in mild winters, birds frequently exhibit some reproductive behavior which accounts for the limited egg laying by lice at this time. Though hormone production may be moderately high during the winter, release to the blood is usually restricted. Members of the mallophagan genus Philopterus normally do not feed on blood, and in this group the life cycle is not so closely coordinated with that of the Orange—crown.
A Connecting Pot Technique for Root Competition Investigations Between Woody Plants or Between Woody and Herbaceous Plants
Authors: Whitcomb Carl E. , Roberts Eliot C. , Landers Roger Q.
Published: May 2006

Two—meter trees were placed in plastic containers so that four large roots could be extended through side holes into openings at the base of smaller pots. The effects of one species on another could be adequately measured by a precise determination of roots produced by the species in the smaller pots at the conclusion of the experiment. Many combinations of tree species or tree and herbaceous species are feasible.
Photosynthetic Response to Temperature and Moisture Stress of Three Timberline Meadow Species
Authors: Klikoff Lionel G.
Published: May 2006

The photosynthetic response to temperature and moisture stress of three dominants of the west, moist, and dry meadows of the central Sierra Nevada was determined. The wet meadows are relatively cold; the dry meadows, warm and the moist meadows, intermediate. The photosynthetic response to moisture stress parallels the natural distribution with Carex exserta of the dry meadows being least sensitive, Potentilla breweri of the moist meadows intermediate, and Calamagrostis breweri of the wet meadows most sensitive. The photosynthetic response to temperature also parallels the natural distributions. Calamagrostis photosynthesis more efficiently at lower temperatures than Carex or Potentilla.
Photoperiodism in Froelichia Floridana (Nutt.) Moq. (Amaranthaceae)
Authors: Davidson Robert A.
Published: May 2006

Preliminary studies suggest that flower initiation in plants from Iowa and Texas populations of Froelichia floridana (Nutt.) Moq. is promoted by short—day photoperiods and retarded by long—day photoperiods. However, the degree of long—day retardation is less for northern plants than for southern plants. These differences are probably adaptive and seem to relate most directly to flowering before (southern plants) or after (northern plants) the summer solstice.
Trace Element Regulation in the Marine Alga Caulerpa Racemosa
Authors: Harriss Robert C.
Published: May 2006

Determination of concentrations of eight trace elements in the dry matter of C. racemosa revealed that the transition elements Mn, Fe, Co, and Ni are more highly concentrated than the alkali and alkaline earth elements. The Ni/Co and Ca/Sr ratios in the alga are distinctly different from the ratios of these elements in sea water, while the K/Rb ratio is only slightly different.
Olfactory Response of the Khapra Beetle (Trogoderma Granarium Everts.) Larva to Factors From Larvae of the Same Species
Authors: Heller D. , Shulov A.
Published: May 2006

Using a simple olfactometer, it was found that traces left by crawling larvae of Trogoderma granarium lure other Trogoderma granarium larvae more than various forms of wheat tested. The power of attraction of these traces was compared quantitatively to the power of attraction of minced larvae. Only the latter could, in certain quantities, counteract and overcome the lure of the traces of Trogoderma granarium.
Humidities in Vole Runways
Authors: Getz Lowell L.
Published: May 2006

Relative and absolute humidities were measured in meadow vole runways in a wet marsh and a dry upland abandoned field. There were no significant differences in the humidity conditions between the two areas during the night. During the day the relative humidity of the marsh averaged only 6% higher than that of the abandoned field. The absolute humidity of the abandoned field was significantly higher than that of the marsh from 0800—1400 hr. The observed differences were not great enough to impose a significant measurements was recorded in prairie vole runways. There was no significant difference between the humidity regimes of the meadow and prairie vole runways. Evaporative water loss as influenced by humidity does not appear to be major factor influencing the local distribution of the meadow and prairie vole.
Caloric Values of Plant Seeds Eaten by Birds
Authors: Kendeigh S. Charles , West George C.
Published: May 2006

Gross energy values are given for 51 species of seeds collected in east—central Illinois.
A Population Study of the Cone Moth Laspeyresia Toreuta Grote in Pinus Banksiana Stands
Authors: Abrahamson Lawrence P. , Kraft Kenneth J.
Published: May 2006

The relative density of the cone moth, Laspeyrsia toreuta, was determined for a six—year period in Pinus banksiana stands in two areas of Upper Michigan. The number of emergence holes was used as an index of population size. Density was found to be correlated at the 95% confidence level with May—June rainfall, May—June temperature and rainfall interaction, and cone production. The two areas showed similar patterns of population and cone production.
Fecundity, Reproductive Rates, and Innate Capacity for Increase of Three Parasites of Therioaphis Maculata (Buckton)
Authors: Force Don C. , Messenger P. S.
Published: May 2006

Three species of hymenopterous parasites of the spotted alfalfa aphid were reared over a range of constant temperatures. At each thermal level, life—table data were obtained for each species. These data were used in computing certain statistics concerning reproduction and rates of potential population increase which are valuable in assaying the effectiveness of each species as an aphid parasite. The temperatures studied ranged from 10 to 35°C, and the relative humidity was held as constant as possible between 40 and 60%. Artificial illumination and photoperiods were identical in all studies. The studies showed that the braconid, Trioxys utilis Muesebeck, generally has the highest mean total fecundity of the three species, although the aphelinid, Aphelinus semiflavus Howard, produced more eggs in the temperature range of 18 to 22°C. The gross reproductive rate and net reproductive rate of T. utilis were also higher than the other parasites throughout most of the temperature range studied, although again A. semiflavus showed higher reproductive rates between 24 and 27°C. The innate capacity for increase, rm, of T. utilis was decidedly the highest of the three parasites at all temperatures. The braconid, Praon palitans Muesebeck, was inferior tot he other two parasites in nearly all phases of these life—table statistics. Its inclination to enter a facultative hibernal diapause at relatively mild temperatures, plus its intolerance of higher temperatures, which the other two species endured, limited its thermal range of effectiveness. Statistics such as total fecundity, gross reproduction, rate, net reproduction rate, and innate capacity for increase are discussed relative to their value in indicating the potential effectiveness parasites can be expected to possess in the field.
Habitats of Three Oregon Voles
Authors: Goertz John W.
Published: May 2006

Voles of the species Microtus oregoni oregoni, M. townsendii townsendii, and M. montanus canicaudus were collected from Coast Range and Williamette Valley habitats in webstern Benton County, Oregon, from June 1957 to January 1959, in an effort to determine habitat preferences. Collecting results indicate that the Oregon vole is a species of the Coast Range mountains. It is found in all Coast Range (Douglas fir) habitats, but prefers grassy cutover areas. Townsend voles are most closely associated with both Coast Range and Valley riparian situations especially where dense stands of sedge and grass occur. The gray—tailed vole is found on all agricultural lands, especially in fields and pastures of grass and legumes and along fence rows. This species is not associated with Coast Range habitats. The gray—tailed vole is at all times a potential agricultural pest.
Growth and Survival of Bitterweed, Helenium Amarum, in Relation to Nutrition and Competitors
Authors: Caplenor Donald
Published: May 2006

Bitterweed (Helenium amarum (Raf.) H. Rock) was grown in sand culture with various concentrations of mineral nutrient solution in competition with Bermuda grass (Cynodon dactylon (L.) Pers.), both clipped and unclipped. It was also grown in field plots with natural competitors at different fertilizer concentrations and different levels of clipping. Response was measured chiefly by percentage of survival of plants and by dry weight of plant tops. As compared to plants of its own species grown under identical cultural conditions,but without competitors, bitterweed growth was favored by relatively low levels of mineral nutrients. The same relationship was demonstrated when bitterweed growth was compared to growth of certain natural competitors. Survival and growth were clearly related to edaphic factors resulting from the absence of interspecific effects. Thus, in nature bitterweed is a successful competitor only when some factor destroys competitors or severely inhibits their ability to compete.
Division Rates of Salt Marsh Diatoms in Relation to Salinity and Cell Size
Authors: Williams Richard B.
Published: May 2006

Fourteen species of motile pennate diatoms obtained from a Georgia salt marsh were cultured under uniform conditions (19°—20°C, 16,000—23,000 lux) in soil—water medium at salinities between 1 and 68 %. All species grew well over at least the range of 10 to 30%; several species grew well over the entire salinity range. At 20 % the division rate was either maximal or close to maximal. Diatom preconditioned to particular salinities in general divided at the same rate as those not preconditioned. Maximum rates for the 14 species ranged from 0.6 to 3.2 divisions/day. These maximum rates had highly significant correlations with both the logarithm of the cell volume and the square root of cell area/cell volume. Least squares regressions were computed for these relationships with volume expressed in μ3 and area in μ2. Maximum number of divisions per day = 3.75 — 0.7 (log volume) =—0.01 + 1.64 (area/volume)½
Interspecific Transfer of Ca‐45 and P‐32 by Root Systems
Authors: Woods Frank W. , Brock Kirby
Published: May 2006

The extent and rate of interspecific translocation of P—32 and Ca—45 were determined when radiosotopes introduced into stumps of seven red maples were found in leaves of 19 other species which were up to 24 ft from the donor maples. The mode of interspecific transfer may be either by exudation from the donor and absorption by the acceptor species or through mutually shared mycorrhizal fungi. Root grafting probably is not important in transfer. The importance of recognizing the root mass of an ecosystem as a functional unit, rather than an association of independent entities, is emphasized.
A Submarine Algal Growth Chamber for Studies in Benthic Productivity
Authors: Chapman V. J.
Published: May 2006

Anapparatus is described which is a first approach to the growing of large marine algae in situ under some degree of light control. After overcoming mechanical problems, Carpophyllum maschalocarpum and Ecklonia radiata were successfully grown in the chamber. Grazing by fish, echinoderms, and other animals makes experimentation difficult. Various improvements are suggested.
An Apparatus for Experimental Cultivation of Benthic Marine Algae
Authors: Neushul M. , Powell J. H.
Published: May 2006

A series of small carts on a set of tracks running down into the water at a 35° angle to a depth of 14.3 m below mean lower low water and used for experimental outplantings of benthic marine algae. Algae attached to the carts were grown at known depths. The experimental utilization of natural environmental conditions provided basic information on the growth and reproduction of larger marine algae.
Substrate Relations of the Burrowing Amphipod Pontoporeia Affinis in Lake Michigan
Authors: Marzolf G. Richard
Published: May 2006

Pontoporeia affinis, a burrowing amphipod and the predominant macrobenthic invertebrate in the upper Great Lakes, was studied during the summer months of 1960 and 1961 with regard for its association with the bottom sediments. The primary requirement of the sampling method was to obtain an undisturbed sediment sample. A corer was used to achieve this end. The particle size distribution of the sediments in the study area is graded from coarse, well—sorted sands in the shallow water at the mouth of Grand Traverse Bay to fine, less—well—sorted sediments in the deeper water of Lake Michigan. Loss on ignition was utilized to estimate the organic material in the sediments. Over the sandy sediments organic matter was largely restricted to a thin detrital layer. The amount of organic material in the silty sediments of the deep water was several times that of the sandy sediments. Bacteria were counted directly and correlated with depth, particle size, and estimates of the organic content of the sediments. The number of bacteria per gram of dry sediment ranged from 126 x 106 to 860 x 106. The distribution of P. affinis in the study area showed no significant correlation with depth, particle size, or organic matter estimates of the sediments, but correlated with the number of bacteria in the sediments. The numbers of P. affinis collected from several of the stations exceeded maximum population densities reported in the literature. In the laboratory P. affinis selected sediment particles smaller than 1 (0.05 mm). There was no apparent resolution of size differences in experiments utilizing sediments finer than 1. There was significant selection of substrates whose surface layers were enriched with organic matter or which were allowed to condition, assumedly by the growth of bacteria on the substrate surfaces. Relationships of P. affinis to the substrate were shown to be strongly influenced by the presence of bacteria and organic matter in the sediments, one or both of these serving as the energy source for the amphipod populations. The predominance of P. affinis in the benthic community and its high population densities indicate that it accounts for a large part of the energy dynamics of the benthic trophic system.
Natural History, Limiting Factors and Energetics of the Opisthobranch Navanax Inermis
Authors: Paine Robert T.
Published: May 2006

Populations of the carnivorous opisthobranch Navanax inermis, living in the vicinity of San Diego, California, were studied from September 1961 to August 1962. Three sampling stations were established, one on the open coast and two in relatively sheltered bays. For all stations, population density and prey content of each gut at time of capture are known. Other data, including caloric content of principal prey, rates of Navanax oxygen consumption, and turnover time of food in gut have permitted the energy available to the field population for growth to be estimated. Laboratory studies, including a complete energy budget in which calories of ingestion, egestion, growth, and reproduction are known, gave data on assimilation efficiency (62%) and maximum possible growth rates (small individuals, 7 to 9% wet wt/day; large, 2.1 to 3.8%). Potential growth in the field, determined by assuming complete conversion to new protoplasm of any caloric excess remaining after consideration of the daily metabolic costs, was compared to these maximum laboratory rates and related to density. In bays, an optimum habitat, density and caloric surplus are positively correlated density—dependent cannibalism characterizes populations of small individuals; and all sized individuals are usually food limited. In marginal, open coast habitats, population density appears to be more closely related to events in the physical environment.
Characteristics and Uses of Peromyscus Tracking Data
Authors: Sheppe Walter
Published: May 2006

Movements of island populations of deer mice were studied by smoked paper tracking supplemented by live trapping. Some mice tracked regularly, others rarely. Some stations were tracked much more than others. The number of track records per night varied greatly, being much greater immediately after trapping than at other times. Tracking was increased when novel track shelters were substituted for familiar ones. Use of shelters is a form of exploratory behavior that occurs most often when the shelters present stimuli strong enough to elicit exploration but not strong enough to repel the mouse. Tracking also was increased when bait was placed in the shelters. The tracking method produces more data than trapping and interferes less with the movements of the mice. However, it has a greater probability of error, produces more variable results, and does not provide data on the condition of the mice.
The Effects of Crowding on the Survival of Meadow Voles (Microtus Pennsylvanicus) Deprived of Cover and Water
Authors: Warnock John E.
Published: May 2006

This study investigated the effect of crowding on the survival time and endocrine response of laboratory—reared meadow voles deprived of cover and water. Crowding was experimentally varied in terms of amount of social contact (number of individuals/group) rather than density (number of individuals/unit area). The crowded situation consisted of ten animals (five of each sex) in a pen of 15 ft2, the uncrowded situation of two animals (one of each sex) in a pen of 3 ft2–one mouse per 1.5 ftw in both situations. Survival times were recorded for 504 experimental mice. Supplementary data on adrenal weight, spleen weight, thymus weight, body weight, and the amount of wounding were obtained for 888 mice. In the animals provided with an adequate supply of cover, crowding induced hypertrophy of the spleen and of the female adrenal, but it had no adverse effect on wounding or survival. In the absence of cover, however, crowding precipitated much fighting and mortality. Twenty—seven per cent of the crowded animals deprived of cover succumbed whereas none of those with cover died. This mortality was greatest among the males. Crowding lowered the survival time of meadow voles deprived of water with males having a lower survival time than females. Prolongation of the crowding period decreased the survival time in males but not in females. The ill effects of crowding on survival time disappeared within a few days after animals were released from the crowded situation. Crowded animals autopsied after succumbing has slightly enlarged adrenals and greatly enlarged spleens compared with uncrowded animals. The thymus was not affected by crowding. The incidence of wounding in males was greater in the crowded animals. In all cases animal deprived of water showed adrenal hypertrophy, splenic and thymic atrophy, and a loss in body weight. Dominant males in the social hierarchies of stabilized groups showed longer survival times without water than subordinate males. They also showed greater gains in body weight. Adrenal weight, thymus weight, spleen weight, and the amount of wounding in males also varied in relation to social rank but appeared to be more closely related to the stability of a social hierarchy. The females showed very little agonistic interaction and did not organize into recognizable social hierarchies. The low frequency of social conflict and high survival time in females, and the high frequency of social conflict and low survival time in males, suggest that crowding does affect the capacity of an animal to survive in stressful situations. It can be concluded that under the conditions applying in this study crowding operates to regulate populations of voles by increasing the vulnerability of the animals to various deleterious factors. Conclusive evidence remains to be presented that crowding does, in fact, operate to regulate populations in nature.
The Determination and Use of Thermodynamic Data in Ecology
Authors: Scott D.
Published: May 2006

Procedures are outlined whereby enthalpy, entropy, and Gibbs' free energy could be determined for biological material from heat of combustion, chemical analysis, and entropy determinations. Some criteria for determining possible energy pathways between species are derived from their free energy concentrations. Rarely will a pathway be thermodynamically impossible.
Social Stimulation and the Survival of Mice Under Prolonged Water Deprivation
Authors: Ressler Robert H. , Haasch William D.
Published: May 2006

Pairs of male, hybrid mice sharing a .03 ml daily water ration lost significantly less weight and survived significantly longer if permitted physical contact in the cage than if separated by a wire screen. Physical contact prolonged survival even when the analysis was restricted to the possible victims of cannibalization. Although allowed to consume the full water ration on each day, additional mice housed one—per—cage lost as much weight and died as soon as unseparated pairs sharing the ration. It is suggested that, if physical contact among individuals is maintained, aggregation may be advantageous to a population even when it results in a reduced supply for each individual of a resource necessary for survival.
A Gradient Analysis of Wisconsin Prairie Vegatation on the Basis of Plant Structure and Function
Authors: Knight Dennis H.
Published: May 2006

Twenty—six stands of Wisconsin prairie vegetation, distributed along a moisture gradient, are compared on the basis of plant structure and function. Characters used include method of vegetative propagation, penology, height, life form, leaf size, and root—system structure, and importance in a stand in evaluated from the percentage of the prevalent species with the character. Numerous characters show trends along the moisture gradient, some being more common in the flora of dry parries, others in the flora of wet prairies. Using structural—functional characters, an index is developed to indicate the relative importance of plant characters most common in dry prairie. With this index the stands are arranged according to their relative wetness or dryness. In contrast to compositional indices based on species presence, the structural—functional index has the potential of being applied to similar grasslands around the world, regardless of species differences.
Energy, Plants, and Ecology
Authors: Gates David M.
Published: May 2006

The environmental factors affecting the flow of energy between a plant and its environment are described. These factors are solar and thermal radiation, air temperature, water vapor density of the air, and wind speed. The mechanisms of radiation, convection, and transpiration which transfer energy between the plant and the environment are expressed in analytical form. An example is given of a 24—hour cycle for a plant illustrating the daily variation of each of these factors and of the resulting plant temperature. Basic plant properties, such as absorptance to radiation, convection coefficient, and water vapor diffusion resistance, determine the extent to which the environment influences the energy content and temperature of the plant. Photosynthesis is light and temperature dependent, and other physiological processes are temperature dependent only. Maxima and minima in photosynthetic activity occur during a day as a consequence of changes in light intensity and leaf temperature produced by varying environmental conditions. The ecological significance of these environmentally influenced physiological processes is enormous in terms of productivity and competition.
Spacing and Competition in Natural Stands of Sand Pine
Authors: Laessle Albert M.
Published: May 2006

Spacing studies of many even—aged, pure stands of sand pine of various age classes using nearest neighbor distances show that most stands under 23 years old are either aggregated or essentially randomly distributed. Most stands 23 or more years old show significant to highly significant departures toward regular spacing. Information regarding the severity and duration of maximal intraspecific competition between the trees was obtained by measuring nearest neighbor distances to all pines, dead or alive. departure towards more even spacing was shown in nearly every stand when only live trees of the same quadrat were considered. Only stands showing maximal intraspecific competition–those showing a considerable number of dead trees–were studied. In an aggregate stand which showed marked trunk divergence from the center of clumps, distances were measured in the same sample both at breast height and at ground level. The difference in apparent spacing proved highly significant–the breast height measurements being essentially random, the ground level ones highly aggregate. A marked thinning of the understory herbs and shrubs appeared correlated with longer maximal intraspecific competition in one portion of a stand than in another part of the same stand with a dense understory. Correlations between the sum of the squared diameters of nearest neighbors and the distance between them proved positive at the 1% level in three stands, positive at the 5% level in three, and so weakly positive in three as to have little significance. Correlation coefficients were only weakly consistent with stand age, the older stands tending to have the higher correlations.
Ecology of the Basking Habit in Turtles
Authors: Boyer Don R.
Published: May 2006

A combined field and laboratory study was conducted to assess the biological implications of the basking habit in turtles. The effect of light intensity and incidence angle, water and air temperatures, wind, and cloud cover upon rates of heat gain in turtles were investigated, and all were found to have importance. Biological factors of importance are behavior, shape, weight, and rarely, color; sex and species were not important except as they affect the other factors. A series of motivation studies was conducted to identify the environmental factors initiating and directing basking. The taxonomic incidence of the basking habit in turtles is discussed. Basking serves primarily as a method of thermal control, with secondary benefits in drying of the skin and shell.