bluuebunny/crossref_metadata_2025 huggingface dataset:
Plant Succession on Dune Sands in Fremont County, Idaho
Authors: Chadwick Howard W. , Dalke Paul D.
Published: May 2006

Active sand dunes in Fremont County, Idaho, move northeastward at an approximate rate of 3 m/year. Sand deposits, continuous in some areas for several kilometers, extend to windward from the dunes in the form of long ridges, parallel to the wind direction. Five successional vegetation stages, distinct as to dominant species, appear on the deposits as belts transverse to the direction of dune movement. Elymus flavascens and Psoralea lanceolata dominate the pioneer stage, which lasts up to about 30 years. The second stage, dominated by Chrysothamnus nauseosus with an understory of the two pioneer species, lasts from 10 to 70 years. Purshia tridentata then replaces much of the C. nauseosus to form a third stage lasting for about 50 to 70 years. Dominant species in the fourth stage are Artemisia tridentata, P. tridentata, and in many areas Prunus virginiana var. demissa. Very little A. tridentata is found after 700 to 900 years of stabilization, and the final and most extensive stage on deep sand is dominated by dense P. tridentata with clumps of P. virginiana var. demissa. Vegetation on old, shallow deposits has characteristics of both that on deep sand and the Artemisia/bunchgrass type on the surrounding native soil. Fields that were plowed and abandoned in the early 1930's now support dense stands of Stipa comata. The presence of dense shrub stands on dunes now topographically sheltered by the wind, but not on migrating dunes, indicates that establishment of a species on sand depends on relative site stability rather than on soil nutrient buildup caused by previous vegetation. Deep sand holds moisture available to plants throughout the dry part of the growing season while the native soil does not, which probably accounts for the greater shrub density and vigor on sand.
Influences of a Thermonuclear Cratering Test on Close‐In Populations of Lizards
Authors: Turner Frederick B. , Gist Clayton S.
Published: May 2006

Following the Sedan test of July 6, 1962, adult Cnemidophorus tigris, Crotaphytus wislizeni, and Uta stansburiana were exterminated to a distance of 4,000 ft from ground zero. Very few adult lizards of any species were observed within 6,000 ft of ground zero during August and November 1962, but the posttest observations in 1962 may have reflected seasonal inactivity. Sampling in June of 1963 indicated that the apparent absence of adults within 4,000 ft was real. No changes attributable to the test were detected at 8,500 to 9,000 ft. Eggs of the three species hatched following the tests in areas where adults did not survive. Young Uta stansburiana were numerous in August from 2,600 to 9,000 ft from ground zero. By October, the young lizards at 2,600 ft were gone, and mortality at 3,800 ft was extremely heavy. At 9,000 ft the apparent density of young Uta was only slightly reduced as compared to that in August. In June of 1963, adults of the three species were observed between 4,500 and 5,000 ft from ground zero, and Uta was apparently most abundant. It is possible that Cnemidophorus is more sensitive than Uta to the deleterious influences involved in this study. The immediate mortality within 4,000 ft is attributed to the gross physical effects of the detonation–dirt fall and blast–which destroyed all of the vegetation out to 2,000 ft and caused partial damage to 5,000 ft from ground zero. Delayed mortality–as that exhibited by juveniles which hatched after the test–is attributed to destruction of habitat. Neither the depletion of food resources nor the residual gamma radiation is likely to have been lethal. Absorbed tissue doses, as registered by three microdosimeters implanted in lizards before the test and recovered July 28 were probably significantly less than the free—air dose registered in the same area.
Laboratory Studies on Competition Among Three Parasites of the Spotted Alfalfa Aphid Therioaphis Maculata (Buckton)
Authors: Force Don C. , Messenger P. S.
Published: May 2006

Three species of solitary endophagous parasites of the spotted alfalfa aphid were tested under constant temperature conditions to obtain information on the reproductive behavior and competitive ability of each in relation to the others. The braconid, Trioxys utilis, was found at both 21 and 27°C to be a very effective competitor because of its ability to find hosts rapidly, to oviposit rapidly and frequently, because of the ability of its larvae to compete successfully with other larvae within the host, and because of its habit of parasitizing young aphids before they become attractive to other parasite species. However, it tends to be wasteful of eggs, in the laboratory at least, since under some situations it does not readily discriminate parasitized from unparasitized hosts. Corresponding with this propensity toward superparasitism is its habit of multiple parasitism. A second braconid, Praon palitans, is somewhat less efficient in its search ability, oviposition rate, and host discrimination than T. utilis. It tends to waste eggs through excessive amounts of superparasitism. It also multiple—parasitizes hosts freely. It parasitizes older host stages, which if already parasitized by other species places it at a disadvantage. However, the larvae of this species are excellent competitors within multiple—parasitized hosts. The third parasite, Aphelinus semiflavus, is inferior to the other species in its slowness to find and parasitize hosts. However, it discriminates to a high degree parasitized from unparatized hosts, and tends to avid wastage of eggs through superparasitism or multiple parasitism. Larvae of this species, when engaged in internal competition with other species through multiple parasitism by the latter, generally fail to survive.
Origin and Disjunction of the Alpine Tundra Flora on San Francisco Mountain, Arizona
Authors: Moore Thomas C.
Published: May 2006

San Francisco Mountain, an extinct, eroded volcano 12,670 ft in elevation, is situated on the Colorado Plateau in northern Arizona. The summits of the two highest peaks of the mountain support a disjunct flora of approximately 51 known species of alpine tunda vascular plants on 2 square miles of area above the 11,500—ft timberline. The relict alpine tundra flora is definitely related to the tundra of the high peaks of the main Rocky Mountains to the north and northeast. At least 90% of the present alpine tundra vascular flora is believed to have migrated southward to the mountain during Pleistocene time, possibly as recently as 65,000 to 75,000 years ago. As of 10,000 to 24,000 years ago, the alpine tundra vascular flora began to be disjunct from its progenitor flora in the main Rocky Mountains. There seems to be in progress a retrogressive directional change in the tundra flora to even less complex community types than exist at present.
A Pitfall Trapping Survey of Darkling Beetles in Desert Steppe Vegetation
Authors: Rickard W. H. , Haverfield L. E.
Published: May 2006

A pitfall trapping survey of autumn emergent darkling beetles was conducted on the Hanford Reservation, Benton County, Washington, in 1963. Forty—nine pitfall traps were arranged in a grid pattern in greasewood and sagebrush communities. Quantitatively, the beetle catch was composed almost entirely of two species Pelecyphorus densicollis and Stenomorpha puncticollis. These appeared in the traps in September and reached a peak of abundance in mid—October. Trap catches declined until early December when the beetles were killed by the onset of cold weather. A total of 4,378 beetles was captured, marked, and released. An estimate of beetle population indicated that about one thousand more beetles were present in the sagebrush community. Stenomorpha was more abundant than Pelecyphorus in either community, but more Pelecyphorus occurred in sagebrush than in greasewood. A dense sward of cheatgrass in the greasewood community appeared to reduce the catch of Pelecyphorus but not Stenomorpha. Pelecyphorus showed a predilection for open ground between shrub canopies but Stenomorpha predominated on ground beneath the shrub canopies. On the average, Stenomorpha weighed more than Pelecyphorus. This resulted in a beetle biomass of approximately the same magnitude in both communities.
Life History Variations in An Association of Odonata
Authors: Kormondy Edward J. , Gower Jennett L.
Published: May 2006

Seventeen species of Odonata occurring in east Twin Pond, Crawford Co., Pennsylvania, were studied over two adult seasons between June 1961 and September 1962. Emphasis was on larval growth patterns, emergence patterns, adult population size and sex ratio, and habitat selection. One— and two—year larval growth patterns with varying degrees of uniformity in age class distribution were observed. The species will overwintered as larvae with cessation of growth. Considerable annual variation existed in each species in: onset, peak and duration of emergence period; the degree of synchrony of emergence; population size; sex ratio. The variations showed no consistent pattern of alternation among the different species suggesting plasticity of response to differential influences. Distribution appears to be clumped and determined largely by the vegetation.
Estimation of Tolerance over an Indefinite Time Period
Authors: Green Roger H.
Published: May 2006

Ecologists and toleration physiologists are often interested in tolerance limits of organisms over indefinite periods of time. A method is proposed by which estimates of LD 50 over finite periods of time can be used to predict the tolerance limit over an indefinite period of time.
An Apparatus for Continuous Recording of Food Intake in Caged Birds
Authors: Morton Martin L.
Published: May 2006

A description is made of an apparatus that will provide a continuous record of food intake by small caged birds. This apparatus employs strain gages as its principal transducer. It can detect a weight change of 0.05 g in 15 g, has an accuracy of greater than 99%, and yields a linear record of weight versus strain. The method has many obvious laboratory applications. Sample data are presented.
Predation and Abundance in Populations of Flour Beetles
Authors: Young Allen M.
Published: May 2006

Single—species populations of flour beetles, Tribolium confusum and T. castaneum, were experimentally manipulated to demonstrate that both predation by adults on pupae and predation by larvae on eggs are effective mechanisms for regulating the abundance of adult beetles. It was shown that predation by adults on pupae is the more effective of the two mechanisms, since experimental interference with the first kind of predation produces a larger increase in adult populations than does interference with the second kind. The same generalization holds for both species.
Freezing Resistance of Alpine Plants
Authors: Sakai A. , Otsuka K.
Published: May 2006

During the growing season alpine plants on Mt. Kurodake (1,984 m) in the Taisetsu mountain range in Hokkaido, Japan, survived freezing to only —5° to —7°C. Even after exposure to 0° and —3°C for 2 weeks, the resistance to freezing of these plants increased only slightly. During the winter, however, most alpine plants studied survived freezing at temperatures below —30°. Salix pauciflora, Diapensia lapponica, mosses, an lichens resisted freezing down to —70°C. They also retained viability after immersion in liquid nitrogen following prefreezing at —30°C. Furthermore, there did not appear to be an essential difference in the hardening effect between willows growing in high mountains and in low altitudes in Hookaido. Alpine plants may be characterized by their dwarf form, short growth period, and high freezing resistance of subterranean stems, crowns, and roots.
Effects of Host Fighting Behavior on the Course of Infection of Trypanosoma Duttoni in Mice
Authors: Jackson L. A. , Farmer J. N.
Published: May 2006

In one experiment, male albino mice were inoculated with Trypanosoma duttoni, and were allowed to begin fighting on the same day; the fighting animals developed significantly lower parasitemias than the isolated controls throughout the reproductive phase of the infection. In two other experiments, mice were allowed to fight for a period of 10 days prior to inoculation; the fighting animal exhibited higher parasitemias than the controls, with the subordinate mice developing slightly, but not significantly, higher parasitemias than the dominant animals. Since all differences noted among controls, dominants and subordinates were during the reproductive phase of the infection, and since no differences were observed in the length of infection among these groups, it was concluded that fighting altered the ablastic, but not the trypanocidal antibody response. This alteration is believed to have resulted from the action of adrenal cortical hormones on antibody—producing cells. Sustained elevation of plasma corticosterone levels during 10 days of fighting in the latter experiments may have been responsible for the different results obtained with the two experimental designs.
An Empirical Approach to the Estimation of Pattern Intensity from Density and Cover Data
Authors: Kershaw K. A.
Published: May 2006

Previous measures of pattern intensity have assumed a direct relationship between intensity of pattern and mean square/mean, i.e., pattern intensity is related to plant abundance. From a series of simple arithmetical models pattern intensity is shown in fact to be independent of density. The statistic nΣ1|x2n —o 1 — x2n|/n°Ns (where x = individual values of the data matrix at any one block size (Ns) and n = the number of pairs of comparisons of any one block size) gives a density—independent measure of observed intensity which has a simple relationship to mean square at any one block size. This allows pattern intensity to be calculated directly from mean square values: calculated intensity = /2°variance Ns In field data calculated intensity gives an inflated value when compared with the observed intensity of the data. A generalized correction term has been derived from a range of density data to adjust calculated intensity values. This approach is extended to cover data where the same square root relationship holds but requires a series of correction terms for each block size.
Plant Dispersal by Hares (Lepus Capensis L.) in Kenya
Authors: Agnew A. D. Q. , Flux John E. C.
Published: May 2006

Of 369 hares examined, 160 had a total of 810 disseminules of 17 plant species in their fur. The six commonest plants were Tragus berteronianus, Achyranthes aspera, Pupalia lappacea, Boerhavia repense, Harpachne schimperi, and Themeda triandra. Female hares carried almost three times as many burs as did males. The incidence of zoochory by wild mammals seems unexpectedly variable in different regions.
Homing in Leopard Frogs, Rana Pipiens
Authors: Dole Jim W.
Published: May 2006

A field study of the movements of displaced adult Rana pipiens was conducted in two summers in northern Michigan, using a thread trailing device to follow the animals. Animals displaced relatively short distances (to about 1 km) from their capture site generally oriented correctly in their homeward direction. No evidence of successful homeward orientation could be found in animals displaced greater distance. Blinded frogs displaced up to 800 m oriented and homed as successfully as normal animals displaced comparable distances, from both upwind and downwind of home. It is suggested that orientation is type I (Griffin 1952). Possible mechanisms serving to guide the homing movements of the frogs are discussed.
Reproductive Potential, Activity, and Cycles in the Painted Turtle, Chrysemys Picta
Authors: Gibbons J. Whitfield
Published: May 2006

Reproductive cycles, reproductive potential and activity were determined for populations of the painted turtle, Chrysemys picta. The male reproductive cycle is divisible into three phases. From late March to early May (the mating season) the testes are small but the sperm ducts are filled with sperm. Spermatogenesis occurs from July to October. This results in an increase in testis size. The winter phase is characterized by small testes. Most of the sperm are contained in the epididymis at this time. Transitional periods occur between each of these phases. Courtship behavior occurs in spring and fall, but effective mating probably does not occur in the fall. Ovarian follicles begin to increase in size in September. By March the largest follicles are around 16 mm in diameter. Immediately before ovulation these increases to about 18 mm in diameter. Ovulation occurs around the middle of May and enlarged follicles, as well as the oviducal eggs, are invariably present at this time. Presumably a second clutch is laid. The second ovulation probably occurs in middle June. Mean clutch size is about 6.5 eggs and the annual reproductive potential for an individual is around 13 eggs. Adults become active in early spring when water temperatures reach the minimum tolerance limits. Reproduction is believed to be the incentive for this early activity. Distances traveled by mature males are greatest in the spring. Travel is limited throughout the summer. Juveniles and mature males are found in the same general area in successive summers whereas mature females have often traveled long distances. This is attributed to females leaving the water in one area for nesting purposes and returning to the water in another area.
Soil Moisture in Relation to Vegetation Distribution in the Mountains of Northern Idaho
Authors: Daubenmire R.
Published: May 2006

Soil drouth becomes intense in summer in the steppe (Festuca—Symphoricarpos) of the basal plain, decreasing progressively through Pinus ponderosa and Pseudotsuga menziesii forests on ascending the adjacent foothills. On mid—slopes where Abies grandis appears, and still higher in the mountains where Thuja plicata, Tsuga heterophylla, and Abies lasiocarpa occur, soil drouth appears to be of minor ecologic importance. In mesophytic forest areas early stages in secondary succession that are characterized by overly dense stands of slowgrowing individuals may develop intense soil drouth during this stagnation phase. On the upper parts of south—facing slopes, even high in the forested mountain, small parks with grassland climaxes containing Agropyron spicatum and Festuca idahoensis represent local areas of soil drouth comparable with that of steppe on the basal plain where the same grasses dominate. Climax vegetation types thus closely reflect soil moisture regimes, whereas altitude above sea level is very unreliable. Three grasses native to areas too dry for even the most xerophytic trees were found to germinate in autumn, develop slowly during the winter and so be sufficiently mature by early summer to endure several month of enforced aestivation. Trees, in contrast, do not germinate until spring and so are not far enough developed for their tap roots to descend more rapidly than the soil desiccates. Since they are incapable of enduring prolonged soil drouth they perish as the dry zone extends downward and overtakes their root tips.
Field and Experimental Winter Limnology of Three Colorado Mountain Lakes
Authors: Pennak Robert W.
Published: May 2006

Physical, chemical, and plankton conditions were studied during two winters in three Colorado mountain lakes. Black Lake is mesotrophic, Pass Lake is highly oligotrophic, and Tea Lake is shallow, eutrophic, and pondlike. The lower waters of Black and Pass lakes absorb heat from the basin so that their winter temperatures are above 4.0°C and as high as 5.4°C. The substrate and bottom waters reach equilibrium in late February or March. Thereafter the lower waters cool toward 4.0°C. Black and Pass lakes had thick snow covers and no photosynthesis for 5—7 months, but Tea Lake had little snow and intermittent photosynthesis during all winter months. Black and Pass lakes are summer—oligotrophic and winter—eutrophic. They became so highly anaerobic by March and April that trout populations died. Such winter kills are thought to occur frequently in many small mountain lakes. All three lakes had negligible winter populations of diatoms and green and blue—green algae, but the populations of μ—algae attained winter maxima of 1—14.5 million cells per liter. Such maxima had no consistent seasonal pattern. The importance of winter algal heterotrophy is discussed. Winter copepod and cladoceran populations were negligible; densities seldom exceeded one adult per liter. Rotifer populations were usually dense, commonly exceeding 500 per liter, especially during December and January before the onset of severe anaerobiosis in Black and Pass lakes, and during all months in Tea Lake. Seston varied much more widely than during the months of open water. The seston of large lake—water samples stored in the dark at 3°C for 30 days ranged from a 20% decrease to a 350% increase over the original seston content. Winter plankton had an average respiratory rate in situ of about twice that of the plankton in corresponding water samples kept in a dark refrigerator at 3°C. Water samples treated with antibiotics had a lower plankton respiratory rate during 30 days in a dark refrigerator at 3°C than did refrigerated control samples. After an interval of 60 days, however, comparable samples treated with antibiotics had a respiratory rate higher than that of controls. It is postulated that the inhibition of bacteria by antibiotics makes nutrients available to yeasts, molds, mutant antibiotic—resistant bacteria, and μ—algae (?), which, after a lag phase, grow and collectively attain a high respiratory rate after the longer experimental interval. These results on seston and plankton show that the metabolism of small, enclosed experimental water samples is highly variable and poorly understood, especially in the dark at low temperatures.
Structural Characteristics of Benthic Algal Communities in Laboratory Streams
Authors: McIntire C. David
Published: May 2006

Effects of light intensity and current velocity on the species composition and ecological properties of communities of benthic algae were investigated in laboratory streams. Of the 15 diatom taxa studied, only Melosira varians, Meridion circulare, and Navicula radiosa were more abundant in streams receiving 700 ft—c of illumination than in those receiving 150 ft—c. Achnanthes exigua, A. minutissima, Meridion circulare, Rhoicosphenia curvata, and Navicula radiosa were indifferent to current velocity, while current velocity had a positive effect on the abundance of Nitzschia linearis, Achnanthes lanceolata, Navicula cryptocephala, N. minima, N. seminulum, Synedra ulna, Gomphonema parvulum, G. angustatum, Cocconeis placentula, and the lanceolate Nitzschia. Melosira varians exhibited a negative response to current and was more abundant in standing water. Of the six taxa other than diatoms, Anabaena variabilis and Tribonema minor were more abundant in streams at the higher light intensity, but only one species, Phormidium retzii, was more abundant in streams with a current than in standing water. At a particular season, light intensity, and current velocity, conditions in a laboratory stream allow the establishment of an algal community with a more or less unique species composition and a characteristic biomass, pigment concentration, and increment of export. In order to understand the factors which influence productivity in these communities, it is necessary to have some knowledge of the autecologies of the community constituents and the mechanisms which regulate species composition and diversity of the flora.
Rates of Competitive Exclusion by the Argentine Ant in Bermuda
Authors: Crowell Kenneth L.
Published: May 2006

Since its introduction to Bermuda in 1953, Iridomyrnex humilis has expanded steadily, replacing Pheidole megacephala in all habitats. The basis for this competition was not determined. The dispersal rates of Iridomyrmex from 1953—1966 are analyzed. From 1953 to 1959, Iridomyrmex increased its distribution at the rate of 394 ha. per year. However, radius did not increase linearly, and it is suggested that only those foci within a critical distance of the perimeter can colonize new areas. Moreover, after 1959 there was a decrease in both number of new foci and growth of individual foci. Therefore, while Iridomyrmex and Pheidole have not established an equilibrium, the rate of replacement has slowed markedly.
Comments on the Escape of Prey from Avian Predators
Authors: Recher Harry F. , Recher Judy A.
Published: May 2006

Observations on foraging herons indicate that only a small number of prey organisms manage to escape after being seized by a heron. Those prey which do escape mostly belong to a few genera which have elaborate post—capture escape behavior or possess physical structures which interfere with swallowing by the heron and which tend to prolong the interval between capture and swallowing. Individuals of these genera escape significantly more frequently than prey lacking such behavior or structures.
Environmental Factors Limiting the Productivity and Size of Experimental Populations of Drosophila Serrata and D. Birchii
Authors: Ayala Francisco J.
Published: May 2006

Laboratory populations of several geographic strains of the sibling species, Drosophila serrata and D. birchii were studied. Under the experimental conditions, the biomass produced by a population is determined by the amount of food, and it is independent of temperature and the feeding schedule. The number of flies produced is determined mainly by the amount of food, temperature having a slight effect. Living space determines the size of the population, which is independent of the amount of food and of temperature.
Pontellid Copepods as Indicators of an Oceanic Incursion over Georges Bank
Authors: Sherman Kenneth , Schaner Everett
Published: May 2006

The distribution of pontellid copepods was used to delineate the region of mixing between coastal and oceanic surface waters during an incursion of Gulf Stream water over Georges Bank. The greatest changes in the distribution of pontellids wee at 21°C and between 32.5@% and 33.0@% salinity.
Niche Breadth and Dominance of Parasitic Insects Sharing the Same Host Species
Authors: Price Peter W.
Published: May 2006

A guild of six parasitic insects (Hymenoptera) which attack cocoons of the same sawfly populations was composed of four indigenous and two introduced species. The indigenous parasitoids included the ichneumonids, Pleolophus indistinctus (Prov.), Mastrus aciculatus (Prov.), Gelis urbanus (Brues) and Endasys subclavatus (Say), and the introduced species were the ichneumonid, Pleolophus basizonus (Grav.), and the eulophid, Dahlbominus fuscipennis (Zett.). Their distributions were sampled on five variable requirements, or resource sets. Litter moisture content and seasonal activity varied within plots, and host density, host species, and plant community varied between lots. Although the distributions of the indigenous species overlapped, in relative terms each species occupied one position in the niche space that was poorly exploited by all other guild members. Such an enclave permitted each of the first three species to develop a zone of dominance over the other parasitoids. The introduced species had no recognizable enclave. The most abundant guild member, P. basizononus, was dominant in the sites most favorable to litter—searching parasitoids. It had the broadest niche over the range of litter moisture content and length of seasonal activity, and it interacted more with all other species than any other guild member. It was a better competitor than the next most broadly adapted species, P. indistinctus. Competitive superiority is proposed as the driving force behind abundance, leading to dominance in favorable sites. The density—dependent interaction between individuals, which results in dispersal, appears to be responsible for the occupation of a broader niche.
Phytoplankton Energetics in a Sewage‐Treatment Lagoon
Authors: Verduin Jacob
Published: May 2006

Metabolic rates in a sewage—treatment lagoon system near Deshler, Ohio, were investigated between March 21 and June 10, 1964. The ponds were well mixed vertically, exhibiting daytime average eddy diffusivities of about 1 cm2/sec. The waters had a high titratable base, ranging from 3 to 10 meq/1 during the period of study. Low oxygen levels were encountered for only a short period in the second stage of the two—pond system. Light absorption averaged about 99%/m. The phytoplankton communities, dominated by Scenedesmus, rose to values near 50 (mu)1/1. Rates of CO_2—uptake in the order of one mole–m(—3) day(—1) were observed, but O_2 production averaged only one—fifth as high. A graph of CO2—uptake vs. light intensity revealed a curve closely similar in shape to the typical photosynthesis vs. light curve, but a separate set of data, based on the (14)C uptake, showed anomalously high values at surface light intensities. CO_2 uptake by a photosynthetic metabolic process that does not produce oxygen is postulated to explain the imbalance between CO_2 and O_2 budgets.
Competitive Exclusion as a Factor Influencing the Distributions of Two Species of Terrestrial Salamanders
Authors: Jaeger Robert G.
Published: May 2006

The salamander Plethodon richmondi shenandoah is restricted to areas of talus on Hawksbill Mountain, Shenandoah National Park, Virginia, while P. cinereus inhabits the soil outside the talus. To test the hypothesis that the former species is excluded from the soil by the latter species, three enclosures were constructed in each of four habitats: (i) in talus consisting only of bare rocks, (ii) in talus where soil has infiltrated between but not under rocks, (iii) in isolated pockets of shallow soil within the rocky confines of the talus, and (iv) in deep soil outside the talus. In each habitat one enclosure contained an isolated sample of shenandoah, another an isolated sample of cinereus, and the third a mixture of the two species. The above testes indicated that: (i) neither species survived the extremely dry conditions of the bard rocks for more than a week, (ii) shenandoah expressed a higher survivorship than did cinereus in this relatively dry habitat, (iii) in the shallow soil shenandoah had lower survivorship in the presence of cinereus than it did in isolation, and (iv) in the deep soil shenandoah had poorer survivorship than cinereus in the mixed species enclosure and poorer survivorship than its isolated control. P. cinereus apparently inhibits the presence of shenandoah in areas of soil, while shenandoah survives better under rocky conditions. However, the talus is a suboptimal habitat for shenandoah, since its survivorship in isolated enclosures is significantly better in the presence of soil. It seems unlikely that salamanders other than cinereus could exclude shenandoah from the soil or that other animals exert a strong influence. Predation, diseases, and parasites also do not appear to exclude shenandoah from areas of deep soil. Competitive exclusion by cinereus has probably restricted the distribution of shenandoah to the suboptimal talus refugium.
Interspecific Territoriality in a Pomacentrid Reef Fish, Pomacentrus Flavicauda Whitley
Authors: Low Richard M.
Published: May 2006

Field observations on territorial behavior of the fish P. flavicauda were made for a total of 200 hours at Heron Island, Great Barrier Reef. Specimens 6 cm or more in length restricted their movements to areas of approximately 2 m2 over at least a 5—month period. Distribution of the fish was highly correlated (rs = 0.89) with the amount of interface between sand and dead coral. Such areas provided algae in close proximity to shelter. Observations of agonistic behavior showed that P. flavicauda usually responded agonistically to 38 species of 12 families, but not to 16 other species of 6 families. Apparently competitors for algae elicit an agonistic response from P. flavicauda, while carnivores do not. Maps locating the positions of agosnistic encounters indicate that the entire home range is defended as a territory. The effectiveness of the agonistic behavior was indicated when, following the removal of 6 specimens of P. flavicauda, there was an increase in algal—feeding fishes seen within their territories. Implications, of these results for out understanding of interspecific territoriality are discussed.
Competition for Sulfur by Three Annual‐Range Species in Relation to Temperature
Authors: McKell Cyrus M. , Derwyn R. , Whalley B. , Williams W. A.
Published: May 2006

Competition for sulfur among Trifolium hirtum, Bromus mollis, and Erodium botrys was studied under adequate (20 lb./acre) and inadequate (5 lb./acre) levels of sulfur and three temperatures (10 degrees, 15.5 degrees, and 21.1 degrees C) under controlled environment conditions. At low levels of sulfur there was little difference in yield or sulfur uptake among the three species with regard to temperature when grown in mono—, di—, or trispecific combinations. In general, both sulfur uptake and yield increased slightly with increasing temperature. At the adequate sulfur level there was a large increase in yield and sulfur uptake of T. hirtum both when grown alone and in combination with other species. This increase was most marked at higher temperatures; it was reduced by the presence of B. mollis, but was unaffected by the presence of E. botrys. The growth and sulfur uptake of B. mollis was increased somewhat by the presence of T. hirtum, but was unaffected by the presence of E. botrys.
Growth of Red Oak (Quercus Rubra L.) Seedlings in Relation to Light and Nutrients
Authors: Phares Robert E.
Published: May 2006

Growth and nutrient uptake of red oak seedlings were studied under conditions simulating a forest understory. The tallest seedlings grew in 30% of full light; seedlings in full light had the greatest dry weight accumulation. Seedlings in full light had an average height of 9.7 inches, and those at 30% and 10% light averaged 12.9 and 8.8 inches respectively. Only seedlings in 30% or more light responded in height growth to an NPK fertilizer. Seedlings in 10% light accumulated nutrients, but showed no growth response to fertilization. Thus, fertilization did not lower the minimum light requirements.
Postglacial and Interglacial Vegetation History of Southern Georgia and Central Florida
Authors: Watts W. A.
Published: May 2006

From 8,500 to 5,000 radiocarbon years ago three sites in southeastern Georgia and peninsular Florida, Lake Louise, Scott Lake, and Mud Lake, had predominant sclerophyllous oak forest, scrub, or savanna, probably with patches of bluestem prairie. About 5,000 year ago pine forest came to predominate on upland sites, and there was a more diverse flora of broad—leaved trees than before. Bayhead and cypress swamp vegetation did not become significant until after 5,000 BP, when Fagus (beech) also became abundant for the first time. The sediments at both Lake Louise and Scott Lake present evidence for recent forest clearance and consequent modification of the lake ecosystem. No vegetation record is available for the earlier postglacial or the period of the main Wisconsin Glaciation. Probably most lake basins of the region were dry during this time because of depression of the regional water table in highly permeable Tertiary limestones, caused by eustatic depression of sea level during Wisconsin Glaciation. At Lake Louise, as at Mud Lake, organic deposits too old to be dated by the radiocarbon method underlie the postglacial sequence, separated from it by clastic sediments that represent a large sedimentational hiatus. The lower organic deposits have the characteristics of an interglacial cycle. They are referred to the Sangamon interglacial, thus modifying a previous opinion that the Mud Lake sediments were partly Illinoian and partly Sangamon in age. A basic interglacial cycle proceeding from dry oak forest and herbaceous communities with eutrophic lakes to pine forest with hammock, bayhead, and cypress swamp vegetation is reconstructed for the southeastern United States.
Energy‐ and Weight‐Loss Functions for Decomposing Foliage in Birch and Aspen Forests in Interior Alaska
Authors: Van Cleve Keith
Published: May 2006

Linear relationships were established for energy loss as a function of weight loss for birch, aspen, and alder foliage. Half times for weight loss ranged from 555 days to 651 days. Half times for energy loss ranged from 604 to 720 days.
Effects of Temperature and Light Intensity on the Growth of Scrophularia Marilandica
Authors: Cline Morris G.
Published: May 2006

The effects of temperature and light intensity on the growth of Scrophularia marilandica L. were studies under artificial, semi—natural, and natural environmental conditions. The plants in the controlled environment rooms were grown under 10 different combinations of temperature (48°/58°—63°/73°F) and light intensity (24—123 cal/cm2/day). The plants in the semi—natural experiment were grown outdoors on prepared plots representing seven levels of average radiation ranging from 20.4 to 405.7 cal/cm2/day. Net assimilation rate (NAR) was proportional to light intensity up to 123 cal/cm2/day in the growth rooms. In the semi—natural studies, it was proportional up to 150 cal/cm2/day and from this point up to 300 cal/cm2/day, NAR increased but not proportionally. Above 300 cal/cm2/day NAR was independent of solar radiation. Under controlled conditions NAR decreased slightly with age at the highest light levels. The length of the vegetative phase, the specific leaf area, and the leaf—area ratio were sharply decreased at higher light intensities. The dry weight of all plant organs was augmented by high light intensities. Roots and axillary shoots were especially sensitive. In the growth—room experiments, temperature effects were more pronounced than were light effects. Stem elongation was completely inhibited at temperature regimes below 63°/73°F, and leaf expansion was markedly diminished below 57°/68°F. Consequently the shoot developed a rosette habit and flowering was inhibited. Decreases in temperature to 48°/58°F had little effect of root growth. The net effect of low temperatures was to depress the shoot—root ratio. However, NAR was increased by a reduction in temperature from 63°/73° to 48°/58° at all intensities. The shoot—root ratio of shaded plants was increased to a greater extent by a rise in temperature than was that of the unshaded plants. Regardless of light level, plants at 48°/58°F consistently had a smaller shoot—root ratio than did those at 63°/73°F. Inhibition of stem elongation and subsequent rosette development at low temperatures were not affected by changes in light intensity. The usual development of greater leaf areas by plants growing under lower light intensities was partially reversed at low temperatures. In early spring shoots of native Scrophularia marilandica sprouted from crown buds attached to perennial roots. The timing differential between leaf expansion in April and shoot elongation in May appears to be a temperature—photoperiod interaction. In early spring and autumn cool temperatures which repressed shoot growth had little effect on root growth. Roots increased greatly in size through late summer into early autumn.
A Method for Estimating Crown Weight in Eucalyptus, and Some Implications of Relationships between Crown Weight and Stem Diameter
Authors: Attiwill P. M.
Published: May 2006

Equations relating crown weight to diameter at breast height outside bark (dbhob) are developed for approximately 50—year—old, even—aged stands of Eucalyptus obliqua from initial branch weight—branch girth relationships. These equations are used to predict crown weights of individual trees; the predictions of n'trees per unit area have standard errors of 15%/n' of the summed branchwood weights. Although stem weight is a function of dhob2, considerations both of (crown weight)–dhob and (crown weight)—(stem diameter at base of crown) relationships show that crown weight is a function of (stem diameter at base of crown)2=consent (dhob)3, thus accounting for form factor. There is no logicval basis, therefore, for selecting a tree of mean dhob as a unit for estimating (weight of mean tree x number of tees) dry weight per unit area. The bias (in this sense meaning the deviation from the true value) of estimates so obtained are discussed; an index of the error is provided by the distribution of dhob3 with respect to dbhob. The error, one of underestimation, is likely to increase with stand age, and this must be an important deficiency in some of the productivity—age sequences which have been developed. Expressions defining the tree of mean crown weight are derived, but confidence limits for estimates of dry weight based on a limited number of mean trees, no matter how they are defined, cannot be set until population variation has been estimated.
Recent Pollen Spectra from the Deciduous and Coniferous‐Deciduous Forests of Northeastern Minnesota: A Study in Pollen Dispersal
Authors: Janssen C. R.
Published: May 2006

Pollen samples were taken along nine transects across local vegetational belts bordering bogs or ponds in overall deciduous and coniferous—deciduous forest regions. Three types of pollen rain are distinguished: local, extralocal, and regional. Local pollen rain is derived from plants that grow at or very close to the sampling point. High local values are common in all sorts of vegetation types: lakes, bogs, marshes, and forests. Extralocal pollen rain is derived largely from trees that grow on the slopes and upland adjacent to the sampling site, but not extensively over larger areas. When excluded from the pollen sum along with the local types, its curves increase slightly, but noticeably, along the transect as the source of dispersal is approached. The regional pollen rain is derived from plants common far beyond the immediate basin slopes. When the extralocal and local types are excluded from the sum of upland pollen types, the regional pollen rain differs little from site to site. Its recognition permits comparison of modern and presettlement pollen rain with the composition of the recent regional vegetation.
Change in Distribution and Availability of Nitrogen with Forest Succession on North Slopes in Interior Alaska
Authors: Heilman Paul E.
Published: May 2006

Forest succession on north slopes in interior Alaska results in the development of sphagnum bogs on sites formerly occupied by productive forest. This process is one of gradual deterioration of site associated with the accumulation of moss layers on the forest floor. Advancing succession is accompanied by an increasing nitrogen deficiency in black spruce trees. Black spruce growing on the sphagnum bogs are extremely nitrogen deficient. As the moss layers thicken, the soils become increasingly cold with permafrost rising to within as little as 15 inches of the surface of the sphagnum soils. Examination of the depth distribution of nitrogen revealed very small quantities of nitrogen in the upper and warmer portions of these profiles, with the bulk of the nitrogen located in the very cold and latest to thaw, lower layers. In contrast, in the soils under birch of the nitrogen was located in the warmest upper layers. Under these conditions, much higher rates of mineralization of soil nitrogen must be obtained. The results show why burning, although changing many factors including volatilization of an undetermined amount of nitrogen, may lead to a large increase in available nitrogen because of the change in depth distribution of the nitrogen in the soil.
Analysis of the Species‐Area Relation
Authors: Kilburn Paul D.
Published: May 2006

An equation of the form y = kx2 describing more precisely the species—area relation for plant species in smaller areas is proposed as a result of intensive examination of species presence in six stands of three undisturbed plant communities in the midwest. Each individual equation for each stand is based on a relatively small sample of 900 m2, but within such an area, the fit of observed data to the equations is very close. In these equations, in which y represents species numbers and x the area, k varies primarily according to species size, while the exponent z more truly reflects the species—richness of the community. Both of these constants may prove to be important measures of different community features. The equations fit rooted data more closely than covered, and it is suggested that the former type of information, being easier to obtain and probably more accurate, is preferable. Comparison of published species numbers for larger areas in floras show clearly that the above equation, so very accurate in the smaller areas actually sampled,does not hold for larger areas as the actual number of species drops far below what the equation predicts. An equation describing this relation for a communityover it entire range of area cannot be accurately constructed without considerable additional information on species numbers in larger areas. Such an equation will probably be sigmoid and more complex than the ones presented here. A method is described whereby one may objectively select an appropriate plot size for a given community based on its equation and not affected by the size of the sample from which the equation is derived. Such equations provide a useful means of comparing several floristic features as well as helping to assess historical aspects of plant communities.
Notes on the Ecology and Reproduction of Trichocorixa Reticulata in a Jamaican Salt‐Water Pool
Authors: Davis Charles C.
Published: May 2006

A population of the water boatman Trichocorixa reticulata (Guerin—Meneville) was studied in an isolated, small, shallow, highly saline pool in the mangrove area adjacent to Port Royal, Jamaica. Salinities were great at 43% 0/00, and the temperature of the water during the period of study ranged from 37.8° to 395°C. The boatmen were depositing large numbers of eggs on solid substrata. Despite the very high salinities, the hatching mechanisms were fully comparable to those occurring in the eggs of fresh—water Coleoptera. Eggs hatched equally well in water of 43 0/00 and 4.3 0/00 salinity, except that the process was more rapid in dilute meals. Eggs immersed in water with a salinity greater than 43 0/00 did not hatch until their medium was diluted.
Further Observations on Serpentine Response in Emmenanthe
Authors: Wicklow Donald T.
Published: May 2006

Field observations of Emmenanthe on chaparral burns in California suggest modification of Tadros' (1957) interpretation of serpentine response. The exclusion of E. penduliflora from serpentine soils is relative, not absolute; and both E. penduliflora and E. rosea on serpentine are strongly affected by fire.
A Light, Sturdy, Inexpensive Point Quadrat Frame
Authors: Woodell S. R. J. , Boorman L. A.
Published: May 2006

A point quadrat frame is described, which is inexpensive, compact, and hard—wearing. Its construction and mode of use are outlined.
On the Pollination Ecology of Ficus Sycomorus in East Africa
Authors: Galil J. , Eisikowitch D.
Published: May 2006

Pollination and seed setting in ficus sycomorus have been investigated in East Africa. Ficus sycomorus is monoecious, each fig bearing both male and female flowers. Inside the figs 6 sycophilous wasps develop: Ceratosolen arabicus, Ceratosolen galili and sycophaga sycomori (primary sycophiles), and Apocrypta sp., Eukoebelea sp. and Sycoryctes sp. (secondary sycophiles). The structure and behavior of these wasps and their bearing on pollination and seed productionare studied. Ceratosolen arabiacus is the legitimate pollinator of Ficus sycomorus. It oviposits chiefly into short—styled female flowers, thus ensuring seed setting in the long—styled ones. It is a mutualistic symbiont of the fig. Sycophaga sycomori oviposits into both short— and long—styled flowers, and does not cause seed setting. It is a competitor of Ceratosolen, but a parasite of the fig. Eukoebelea, Apocrypta and Sycoryctes are inquilines, making use of galls induced by the activity of the primary sycophiles. They do not interfere with seed production in pollinated flowers not occupied by Ceratosolen or Sycophaga.