bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential Feeding and Niche Relationships among Orthoptera
Authors: Caplan Elizabeth Bruning
Published: May 2006

The acridian species Melanoplus bivittatus (Say), Melanoplus differentials (Thomas) and Melanoplus lakinus (Scudder) occur in the same habitat, utilizing the same foods. Such coexistence suggests that these species are in the same niche and in competition for a common food supply. Their food usages were investigated by offering samples of dominant and semi—dominant vegetation from the common habitat to caged populations of each species, then estimating the amount consumed. The overall usual of foods of each species formed a preferential pattern sufficiently different from the patterns of the other two species to indicate that the three grasshopper populations occupy separate niches in the community and are not in complete competition for food.
Radioisotope Measurement of Food Consumption by a Leaf Beetle Species, Chrysomela Knabi Brown
Authors: Crossley D. A.
Published: May 2006

A field using radioisotopes to estimate consumption of vegetation by insects was evaluated by comparisons with feeding rates measured in the laboratory. The uptake of 137Cs was investigated for beetle larvae (Chrysomela knabi Brown) feeding on willows in the White Oak Lake bed, an area contaminated with radioactive waste products. Beetle larvae and adults accumulate 137Cs from willow leaves and reach steady—state equilibrium concentrations. Information on biological half—lives (elimination rates) for cesium was used to convert the 137Cs concentrations attained by the beetle larvae into estimates of 137Cs intake rates. Food intake rates were estimated from radiocesium intake rates, by measuring 137Cs concentrations in willow leaves. Food intake rates estimated by this method for field areas were 7 to 16 mg dry wt of plant per larva per day. Laboratory measurements of food consumption rates, by comparison, were about 9 to 10 mg/larva per day for larvae of similar size. Influences of temperature on biological half—lives were also studied, but no correction was applied to the field estimates since mean field temperatures were close to those used in laboratory experiments. The good agreement between laboratory and field measurements supports the validity of previous applications to entire communities of plant—feeding insects. The method would be equally useful with predaceous animals as with herbivores. Measurements of food eaten can be converted to energy units by bomb calorimetry.
Community Dynamics on An Artificial Prairie
Authors: Cottam Grant , Wilson H. Cameron
Published: May 2006

The changes occurring on the J. T. Curtis Prairie, an artificial prairie in the University of Wisconsin Arboretum, were studied by means of four surveys spaced at 5—year intervals. Frequency data from more than 650 meter—square quadrats with known locations were obtained at each survey. Five stands, delimited on the basis of their compositional index (CI) as determined by indicator species, were compared with native prairies having similar CI values by means of species lists and sum frequency of the species. When prairie species only are considered, some artificially established stands are as similar to native stands as native stands is the presence of large numbers of non—prairie species. The artificial stands have much larger species lists and higher sum frequencies than native prairies. The results indicate that the Curtis Prairie is becoming very similar to native prairies in numbers and species of prairie plants, and that the non—prairie species are materially reduced in importance.
Root Extension in a Longleaf Pine Plantation
Authors: Ferrill Mitchell D. , Woods Frank W.
Published: May 2006

Root extension in a 24—year—old longleaf pine plantation in the North Carolina sandhills was studied by the application of 10 mc of I131 directly to the soil, on the surface, or at depths of 1 or 3 ft, and surrounding trees monitored with a portable scintillation counter. Within 10 ft of the point of application, all trees above 3.0 inches absorbed I131 in sufficient quantities to be detected. Beyond 22 ft for surface applications, and 33 ft for 1— and 3—ft depths, no I131 was detected in any trees. Regressions were computed to determine whether root extension could be predicted. When distance from the point of application was used as the dependent variable, an index of competition and the angle from the tree row proved to be the most useful, to the exclusion of the various measures of tree size.
The Influence of Habitats on Mating Systems of North American Passerine Birds
Authors: Verner Jared , Willson Mary F.
Published: May 2006

Regardless of sex ratio, a polygynous mating is expected to be adaptive for the females as well as for the male. Two possible selective bases for the evolution of polygyny are considered: 1) One male may make it advantageous to several females to mate with him by appropriating a large share of a limited number of nest sites. 2) When a large share of the food for the young is obtained from the territory, local variations in food availability could influence the mating system. Given a sufficient minimum level of food supply, the difference in food availability between two males' territories may be great enough to permit a female to rear more young on the better territory, unaided by her mate, than she could on the poorer one even with full assistance from her mate. In this case, selection would favor a female pairing with the male on the better territory, even if this meant establishing a polygynous association. Fourteen of 291 species of North American passerine birds have been reported to be regularly polygynous or promiscuous. Thirteen of the 14 breed in marshes, prairies, or savannah—like habitats, where productivity resulting from solar energy is concentrated into a narrow vertical belt; that in a forest is spread unevenly over a broad vertical belt. Thus, the density of productivity–and of avian food sources–is potentially much greater in marshes and prairies than in forests. Hence, marshes and prairies are more likely than forests to present the minimum requisite food supply and sufficiently great differences in available food between territories for selection to favor polygyny.
Preliminary Experiments on the Foraging of Closely Related Species of Birds
Authors: Grant P. R.
Published: May 2006

The foraging and interactions of three species of sparrows were studied. Both in the wild and in experiments, Zonotrichia melodia and Z. georgiana foraged similarly and with relatively little interaction. Z. melodia was always dominant to Z. georgiana. A greater degree of interaction occurred between Z. melodia and Z. albicollis. These two species foraged differently, Z. melodia spending more time feeding in the grass than Z. albicollis. The degree of differences in foraging between them remained constant from the first to the second experiment, even though both species fed more in the grass in the latter than in the former. In neither experiment was the difference in foraging caused by interactions between the two species in the experiments. It is suggested that interspecific differences in foraging and interaction are related to the need for avoiding competition.
Benthic Fauna and Sediments in the Newly Created Lake Kariba (Central Africa)
Authors: McLachlan A. J. , McLachlan S. M.
Published: May 2006

The development of bottom depostis and the distribution of the associated fauna were studied over a 2—year period in a drowned river "estuary" of the newly created Lake Kariba. The lake bottom was initially made up of submerged soil, the chemical characteristics of which could be related to the parent rock. However, the soil was found to be rapidly changing under the influence of shoreline erosion, river sediment, and the accumulation of organic debris. These factors also affected the distribution of bottom fauna, in which chironomid larvae predominated. Faunal biomass was positively correlated with the amount of organic carbon in the profundal zone and inversely associated with the quantity of coarse sand in the littoral. Superimposed on this pattern was a response to water depth. In the littoral zone, faunal biomass decreased with increasing depth. In the profundal region, benthos was absent when the lake was thermally stratified during the hot season. The annual regime of water—level fluctuation affected shoreline processes, for example by interrupting the development of barrier beaches and coastal erosion. Since these processes were fundamental to the development of sediment patterns, changes in water level influenced the distribution of bottom fauna as well.
Social Faciltation in Weaverbirds: Effects of Varying the Sex Ratio
Authors: Collias N. E. , Brandman M. , Victoria J. K. , Kiff L. F. , Rischer C. E.
Published: May 2006

Experimental colonies of African Village Weaverbirds (Ploceus cucullatus cucullatus) in large outdoor aviaries at Los Angeles were observed. When males were caged singly, each with several females, these males expanded their territorial holdings and had more nests accepted by the females than was the case when other males were present. When several additional males were present during the height of the breeding season, the resident males showed little or no change in their rate of nest—building, but with extra males present more fresh nests became available and more females accepted nests. When the breeding season started to decline, adding more males stimulated renewed onset of nest—building by resident males. When the number of females in each colony was increased four times, the average rate at which the males built and tore down their nests about doubled while the frequency with which the males gave the nest—advertisement display to untamed females tripled. But at the same time the males built on the average only half as many nests per female, reflecting an effective reduction in competition between males for mates when an abundance of females was present.
Energy Exchange in Plant Canopies
Authors: Alderfer Ronald G. , Gates David M.
Published: May 2006

A theoretical model is presented for the exchange of radiant and sensible heat between leaves in a plant canopy and the environment. The distribution of short—wave (0.3—3.0(mu)) radiation in a canopy is described by a modified form of the Kubelka—Munk equations for light transmission through scattering media. Upward and downward radiation fluxes are computed for any level of a canopy as a function of canopy density and optical properties of the leaves. A series of simultaneous equations is used to determine both thermal radiation and leaf temperature at any point in the canopy. Each equation in the series is the energy budget for a leaf at the level in the canopy. This model uses information about the external physical environment together with optical properties of leaves to predict the distribution of solar radiation, leaf temperature, and thermal radiation throughout a plant canopy. Experiments are reported which test the reliability of the theoretical model.
Annual Tree‐Litter Production by Successional Forest Stands, Juneau, Alaska
Authors: Hurd Richard M.
Published: May 2006

Litter production in four stands (pioneer Alnus—Salix to old—growth Tsunga heterophylla/Picea sitchensis) for 3 years averaged 2,850 kg/ha. Production varied among stands and years, but no real differences were apparent. Nonwoody litter was about 64% of total litter and, although less variable, there were no consistent differences for stands nor years.
Sampling to Estimate Mean Leaf Temperatures and Transpiration Rates in Vegetation Canopies
Authors: Miller Philip C.
Published: May 2006

The measurement of leaf temperatures at different levels in the canopy is important for clarifying the relative contributions of each level to the energy balance, evapotranspiration, and primary production of the total canopy. Frequently mean leaf temperatures at each level will be adequate for the study. Since individual leaf temperatures vary at each level, more than one leaf temperature must be measured to estimate mean leaf temperature. A procedure is outlined for deciding the number of leaves at each level required to estimate the mean leaf temperature within specified accuracies. The procedure involves first calculating expected in sunlit leaf temperatures due to differing orientation to the sun and leaf resistance, sunlit leaf temperatures with the energy—budget equation, then estimating the variation to be solving for the number of sunlit leaves to be measured, and finally, calculating the total number of leaves to be measured at each level in order to have an adequate sample of both sunlit and shaded leaves. The number of leaves calculated by this procedure should be considered the minimum number of leaves to be measured because of other causes of variation in leaf temperatures.
Species and Individual Productivity in Phytoplankton Communities
Authors: Maguire Bassett , Neill William E.
Published: May 2006

The relative productivity of individual cells in a mixed phytoplankton community has been determined by (14)C autoradiography. These data allow the estimation of the relative contribution of each of the component species to total community production, illustrate the size—specific production of the cells of each of these species, and suggest predictions concerning future successional developments of the community.
Estimating Leaf‐Area Growth in Pine
Authors: Harms William R.
Published: May 2006

Nondestructive estimates of the leaf—area growth (A) of a pine tree can be obtained from periodic measurements of the green length and the average fascicle length of the foliated portion (fascicle cluster) of individual branches. The prediction equation is A = b_0N + b_1 (Sum of N G_iL_i) where G_i is the green length, L_i is the average fascicle length for the ith fascicle cluster (i = 1,2,...,N), and N is the number of fascicle clusters on the tree. The coefficients for the equation are determined by the method of least squares from a representative sample of fascicle clusters of known leaf area and varying G and L.
Competitive Relationships of Annual Ryegrass (Lolium Multiflorum Lam.)
Authors: McKell C. M. , Duncan Cameron
Published: May 2006

Annual ryegrass (Lolium multiflorum) competition with Kentucky bluegrass, hardinggrass, Blandon brome, wild oats, tall fescue, rose clover, and with itself was studied in greenhouse and field experiments. Ryegrass in a mixture of species always had a detrimental effect on the growth of other species. It did not furnish the usual advantages to other species which occur from a nurse crop or from litter. Annual ryegrass exhibited self—interference when grown in various combinations and densities.
Species Diversity of Euglossa in Panama
Authors: Ricklefs Robert E. , Adams Ralph M. , Dressler Robert L.
Published: May 2006

Species diversity, relative abundance and geographical replacement are described for samples of Euglossa bees collected with the aid of chemical attractants at four localities in central Panama. Marked differences were found in the species collected, in their patterns of relative abundance and in distributions of morphological features (tongue length and body weight). Assuming that a given species in different localities in similarly attracted to a given compound and that the collections are unbiased in other respects, our results suggest that there may be fundamental differences between localities in the partitioning of niches. There are also striking differences from place to place in the proportions of long—tongued and/or large—bodied species.
Primary Production in Grazed and Ungrazed Desert Communities of Eastern Idaho
Authors: Pearson L. C.
Published: May 2006

The harvest method was employed to study primary production in two plant communities, one of which had been continuously grazed for about 70 years while the other had been protected from grazing for a period of 11 years. Exclosures were constructed around both study areas to protect them from livestock grazing during the 2 years of the study. There was 45% more top growth in the protected area but only 68% as much root mass; consequently, average annual net production was at least 12% greater in the grazed area. Irrigation with 9 cm water increased top—growth yield 41.4%. Although over 30 species of plants were present in each community, two species contributed over half of the annual production in both areas. In the protected community 65% and in the grazed community 80% of the plant mass was underground. Proportion of plant mass underground ranged from 55% to over 98% in individual plants excavated whole. Following harvesting of the tops, dry weight of the roots decreased 1.6% during the first week, 22.1% during the first month, and 31.3% during the first 8 months. To measure seasonal trends in productivity, six plots, each 1 m2 in area, were harvested every week during two growing seasons. Artemisia tridentata, the principal shrub present, seemed to be most productive during the fall and early spring while Stipa comata, the principal grass, was most productive during late spring and early summer.
Interpretation of Invertebrate Drift in Streams
Authors: Waters Thomas F.
Published: May 2006

Various experiments were conducted in a small Minnesota trout stream to determine if data on the drift of stream invertebrates obtained with stationary nets set in the stream, may be interpreted as indication of permanent downstream displacement. A mayfly, Baetis vagans McDunnough, and the scud, Gammarus limnaeus Smith, were the two species primarily involved in the drift. Drifting invertebrates were collected in arrays of several shallow nets stacked on their supporting rods to obtain the vertical distribution of the drift through the water column. Both species entered the drift nets, not only along the stream bottom, but in all water strata. A comparison of the standing crops with drift net accumulations indicated that the drift was too large to be supplied only by the standing crops in the vicinity of the drift nets and that the organisms must have drifted down from upstream areas. Measurement of the dispersal of organisms moving into a denuded stream bottom area, alternately open to movement from upstream and downstream, indicated that both species did so primarily at night and from upstream. Experimentally blocking the drift with nets set from bank to bank reduced daily drift rates downstream from the block position through a distance of 38 m, including two riffles and an intervening pool, indicating that the organisms normally drifted through at least this distance. In general, it appears that the accumulation of organisms in drift nets is the result of a permanent displacement of the organisms downstream, and not the result of nondirectional activity in the immediate vicinity of the nets.
A Theoretical Study of Population Regulation in Tribolium Confusum
Authors: Taylor N. W.
Published: May 2006

A deterministic mathematical model is constructed to describe the population growth in colonies of the grain beetle, Tribolium confusum, under laboratory conditions. It is shown how the eating of eggs by adults can account for the main features of the observed population growth, in particular the occurrence of a maximum in the adult numbers and the tendency then to reach a steady state.
Detritus Over the Reef and Its Potential Contribution to Adjacent Waters of Eniwetok Atoll
Authors: Marshall Nelson
Published: May 2006

Observations of particulate matter from off the reefs at Eniwetok Atoll suggest that organic matter, including aggregates, transported in suspension from the reefs to the midatoll areas may constitute a substantial contribution to the trophic systems within the lagoon.
A Twenty‐Year Record of Understory Vegetational Change in a Virgin Pennsylvania Forest
Authors: Hough Ashbel F.
Published: May 2006

The understory vegetation in a 4,08—acre tract of virgin hemlock—hardwood forest on the Allegheny National Forest in northwestern Pennsylvania was studied over a 20—year period by means of color and black—and—white photographs taken at 5—year intervals from 1942 to 1962. The declines which took place in the understory were believed to be caused by browsing by the resident white—tailed deer population. The deer herd, under very light hunting pressure, has depleted the browse supply and damaged advance reproduction of hemlock and hardwoods, preventing understory recovery during the 1942—62 period. Unless relieved, this continued browsing of the understory vegetation will eventually reduce and endanger the scientific and educational value of the area.
Effect of Pruning the Parent Root on Growth of Aspen Suckers
Authors: Zahner Robert , DeByle Norbert V.
Published: May 2006

Various portions of the root systems of bigtooth aspen (Populus grandidentata) suckers were severed, and the subsequent height and radial growth of stems were measured. Aspen vegetative regeneration is heavily dependent on the parent roots for at least 25 years following initial suckering. The distal portion of the parent root contributes more to sucker growth than does the proximal. New roots at the base of suckers contribute little during the first 6 years, then become progressively more important with age, and by 25 years account for about half of annual stem growth.
A Leafy Liverwort Hydrosere on Yakobi Island, Alaska
Authors: Shacklette Hansford T.
Published: May 2006

The liverworts Nardia compressa (Hook.) Gray and Scapania paludosa K.M. are able, because of their aquatic nature and rank growth of intertwined stems, to dam a swift mountain rivulet, thus causing a series of terraced pools to form. Growth of the liverworts closes the pool surface, and vascular plants invade the liverwort mat, leading to the development of a Cladothamnus pyroliflorus Bong. physiographic climax community in an area occupied by late—melting snowbeds. Other hydrophytic bryophytes of the area form mats of insufficient strength to impound streams on steep slopes. The typical snowbed climax communities of this region are not, however, the result of liverworth hydrarch succession.
The Reproducibility of Shrub Cover Sampling
Authors: Stephenson Stephen N. , Buell Murray F.
Published: May 2006

To test the validity of making quantitative measurements of vegetation cover, replicate samples of the same stand of vegetation were made. The line intercept method was used to determine shrub cover values on eight 10—m lines. The results treated statistically indicate that the sampling procedure is reproducible and the results directly comparable.
Total Net Productivity and Turnover on an Energy Basis For Tallgrass Prairie
Authors: Kucera C. L. , Dahlman Roger C. , Koelling Melvin R.
Published: May 2006

The energy equivalent of total net productivity including foliage and roots on unburned prairie in 1962 was 4.351 X 106 cal/m2, representing 992 g of biomass. The root system provided slightly over 50% of the annual increment. For 1963 the total growth was 1,133 g/m2. The average energy for these years was equivalent to 1.21% of the incident radiation received during the growing season for the 400—700 μm portion of the light spectrum. The maximum energy budget including current increment, roots of previous years, and litter was equal to 2.6 turnovers. In years with favorable rainfall, fire approximately doubled the aboveground yield. During drought, productivity increases of fire plots over control plots were curtailed sharply. On a dry matter basis, the total aboveground biomass at the end of the growing season was approximately twice that of the standing crop. During the April—September period for 3 years of observation, the loss in dry weight of the aboveground material ranged from 57% to 65%. For the remiander of the year the decrease was 31—39%. These values indicate a fluctuating but generally balanced annual system of growth and decay. For aboveground biomass, the turnover estimate was 2 years, and for root biomass, 4 years. The decay time of a standing crop or root increment as determined from isolated litter samples and carbon—14—labeled roots in the field indicated that the annual turnover was comprised of a series of increments of different ages, decreasing in caloric content with time on a dry weight basis (uncorrected for ash). On an ash—free basis, litter 4 years old showed some increase in caloric content, suggesting changing composition of the residual fraction. The tallgrass prairie is seen as a relatively efficient ecosystem when compared to the worldwide terrestrial average. The stimulus of fire to dry matter production in the humid prairie indicates a more efficient use of solar energy; however, the long—term effects of sustained burning require observation.
Relationship Between Standing Crop and Primary Productivity Along a Hot Spring Thermal Gradient
Authors: Brock Thomas D.
Published: May 2006

Quantitative measurements of photosynthesis (by carbon—14) and chlorophyll were made for algal mats which had developed at a series of stations along the thermal gradient formed by the outflow channel of a hot spring at Yellowstone National Park. The temperature range studied was from 30°—70°. Comparisons were made of photosynthetic efficiency, which had been measured and calculated in different ways. There was no simple correlation between standing crop (as measured by chlorophyll, protein or RNA per unit area) and photosynthesis. Animal grazers on the algal mats occur only at temperatures below 50°; the low standing crop at the lower temperatures may be due to the comsumption of algae and bacteria by these animals. At a temperature of 58oC, very thick mats are found, composed mostly of filamentous bacteria with a surface layer of algae. It is suggested that the organic carbon originating from the algae is assimilated by these bacteria and is not released because of the absence of grazers. At temperatures close to the upper limit for algal growth, standing crop is low although photosynthetic efficiency is high, and the algae are optimally adapted to the temperatures at which they are living. Some physiological factor other than photosynthesis may limit the growth of algae at these highest temperatures. The value of hot springs as models to study aspects of ecosystem trophodynamics is shown by this work.
The Effects of Thermal Heterogeneity in the Environment on the Activity and Development of Oncopeltus Fasciatus (Dallas)
Authors: Barrett Ronald W. , Chiang H. C.
Published: May 2006

The reactions of age specific nymphs of the milkweed bug to a heat spot in the laboratory and to sunlight in the field were observed. Laboratory results showed that in an environment where a thermal heterogeneity is present, the insects were attracted to a spot warmer than the ambient temperature. This was particularly striking when the ambient temperature was low, as reflected by both the large percent of nymphs which responded and by a higher chosen temperature. The responses also varied with the intra—instar age, being the most striking in the pre—feeding period, next in the post—feeding period, and the least in the feeding period. Ecdysis, however, never occurred on the heat spot even at low ambient temperatures. Heat spot aggregation resulted in a higher rate of development. This increment was greater at lower ambient temperatures. These results correlated with the field observations. During the pre—feeding period, the nymphs stayed on the top parts of plants basking in the sun throughout the day. During the feeding period and post—feeding period, they stayed in the sun only during the morning hours. The possible implications of these activity patterns to the survival, abundance and distribution of the species also are discussed.
Behavioral Thermoregulation and Its Role in the Ecolgy of the Red‐Bellied Newt, Taricha Rivularis
Authors: Licht Paul , Brown Allen G.
Published: May 2006

Laboratory thermal gradient studies indicate a capacity for behavioral control of body temperature throughout the life history of the red—bellied newt, Taricha rivularis. The aquatic larvae exhibit district thermal preferences, between 20 to 26oC, within a week of hatching. Heat resistance varies with age and previous thermal history, but the thermal preferendum is ralatively stable. Thermal responses of terrestrial adults are similar to those of larvae. Temperature appears to be more important than soil moisture during the initial microhabitat selection of hydrated newts. However, preferences for soil moisture and diurnal shelters may eventually compromise thermal preferences. Thermal responses change markedly during the aquatic transition and subsequent entry into the breeding—stream in the spring. The aquatic adults avoid temperatures above 18 to 20° and show little avoidance of near—freezing temperatures. A loss of heat avoidance occurs after exposure to 23°C for several days. The heat resistance of adults is only slightly different from that of a larvae. Field observation in a breeding—stream with hot springs indicate that behavioral responses to temperature may play an important role in the ecology of this newt. Thermal preferences may influence the diurnal movements and micorhabitat distribution of larvae. Avoidance of high temperatures prevents the breeding adults from approaching areas near the hot spring effluent. A high thermal conductivity and differential heating in brain, legs, and body make the hot effluent very hazardous. Thermal preferences may influence the activity of the terrestrial adults even though they may not fully attain these levels of body temperature. Comparisons with adults and larvae from other breeding populations of T. rivularis indicate that these thermal responses are characteristic of the species. Furthermore, thermal preferences appear virtually identical among the larvae of several species and hybrids of Taricha. These results do not support previous conclusions that salamanders lack distinct thermal preferences and the ability to control body temperature.
Population Growth Response of Isochrysis Galbana to Nitrate Variation at Limiting Concentrations
Authors: Caperon John
Published: May 2006

Data are presented from two continuous culture experiments with Isochrysis galbana using nitrate as limiting nutrient. It is suggested that initial uptake of nitrate is very rapid compared to the next synthesis step and thus that the concentration of some form of internal rather than environmental nitrogen controls growth rate when the nitrogen supply is limiting. Under this assumption the steady state growth rates are shown to fit a hyperbolic curve relating growth rate to the inferred internal nitrogen concentration.
The Roles of Pine and Spruce in the Forest History of Minnesota and Adjacent Areas
Authors: Wright H. E.
Published: May 2006

Compilation of the percentages of pine and spruce pollen from throughout northeastern and north—central North America shows that at the present time pine exceeds 10% in the tundra, forest/tundra transition, and boreal forest, and that spruce percentages are generally higher than pine in these areas except in Manitoba. The conifer—hardwood forest has much more pine pollen, especially to the west, and it has very little spruce. In the deciduous forest, pine pollen is generally less than 10%, and in the prairie only a few percent. The late—glacial spruce zone of New England may record a vegetation similar to the boreal forest of today, which contains Pinus banksiana, but the evidence indicates that in the Great Lakes region pine trees were absent. As a result of the climatic change that set off the rapid retreat of the ice sheet from the Great Lakes region, starting about 12,000 years ago, the peripheral spruce forest rapidly deteriorated. The spruce was replaced in south—central Minnesota by birch and alder, and these by elm, oak, and other deciduous trees about 9,500 years ago. In east—central Minnesota, however, the wave of spruce destruction did not arrive until about 10,500 years ago, and by this time pine had invaded from the east, perhaps by way of the northern end of the Great Lakes when the ice retreated into Canada. Here the spruce forest was replaced by pine in a very few hundred years. In northeastern Minnesota spruce remained important until about 9,000 years ago. The pine involved in these forest transformations was either jack or red pine (or both), according to studies of pollen morphology. White pine arrived in eastern Minnesota about 7,000 years ago, also from the east. Just before this time, the prairie, which had developed in western Minnesota by 8,000 years ago, expanded to the east, as did the oak savanna that bordered it on the side of the forest. Effects of the prairie expansion can be detected in the pollen sequence even in northeastern Minnesota. At the end of the period of prairie expansion, about 4,000 years ago, white pine expanded slowly to the west, reaching northwestern Minnesota about 2,700 years ago. Jack and red pine arrived in this region only about 1,000 years ago.
Structure and Function in California Grasslands
Authors: McNaughton S. J.
Published: May 2006

Functional and floristic properties of annual grasslands on serpentine and sandstone soils at an elevation of 180 m on Stanford University's Jasper Ridge were determined along an intuitive habitat gradient from northeast to southwest exposures. The most frequent species contributed the most to peak standing crop in only half the stands. Stipa pulchra, the only native species among the important species, was more important on serpentine than on sandstone sites. Bromus mollis, the other consistently important species, increased in importance with decreasing moisture supply on both soils. The sandstone grasslands sustained a greater biomass, were more productive, and were less diverse than serpentine grasslands. Within the grasslands as a whole, productivity was inversely related to diversity and positively related to dominance. Stability, however, was related to neither productivity, diversity, or dominance. Thus productivity may increase in such a system with no sacrifice in stability. Properties of sandstone grasslands were clearly related to the habitat gradient from cool, moist sites to warm, dry sites. There was no such relationship in serpentine grasslands. Dominance—diversity curves generally fit previously described models, except on southwestern serpentine exposures. The annual grassland vegetation is a mosaic of floristic composition and ecological properties, shifting in response to habitat patterns but without abrupt discontinuities.
An Evaluation of the Grassland Quarter Method
Authors: Risser Paul G. , Zedler Paul H.
Published: May 2006

The point—centered quarter method was applied to six prairie stands in the University of Wisconsin Arboretum using the procedure of Dix (1961). Comparison of quadrat density counts to those obtained with the quarter method showed the two to be significantly correlated. However, the relative difference of the estimates was highly significantly correlated with the aggregation characteristics of the stands as measured by Pielou's index (Pielou 1959). The use of the quarter method on grasslands is subject to question, unless careful checks against quadrat counts are made.
Transplantation of Salt Marsh Vegetation, Georgetown, South Carolina
Authors: Stalter Richard , Batson Wade T.
Published: May 2006

A salt marsh located on the Baruch plantation at Georgetown, South Carolina includes four vegetation zones (High high marsh, Low high marsh, High low marsh and Low low marsh.) Thirty plants of each of the dominant species in each zone were transplanted into the other three vegetation zones, and thirty plants of each of the dominant species in each zone were dug up and replanted in the same zone to serve as controls. Survival and growth rate of the transplants suggest that several species can tolerate conditions not found in their usual zones. Salicornia virginica of the Low high marsh can grow in the High low marsh and Low low marsh, while Limonium carolinianum of the Low high marsh survived when planted in the High low marsh. The data suggest that there are two forms of Spartina alterniflora, a dwarf form occupying the High low marsh, and a tall form occupying the Low low marsh.
Measurement of Elemental Assimilation by Animals from Radioisotope Retention Patterns
Authors: Reichle David E.
Published: May 2006

Measurements and nutrient assimilation by animals from dietary inputs often are based upon chemical analyses of food and feces. Therefore, those budgets of the difference between nutrient values of food consumed and feces produced provide an estimate of the digestive assimilation of nutrients–equivalent to metabolizable energy in energy balance calculations (Harris 1966)–if it can be assumed that intestional secretion of nutrients is not a significant source of error. Although this experimental approach is reasonable for those animals where urinary and digestive products are distinct, e.g., mammals (Petrusewicz 1967), it cannot be applied to those organisms where metabolic and digestive products are intimately mixed in feces. In the latter case, assimilation measurements are biased by the organism's turnover of materials through normal excretory and secretory processes. Fecal analyses on insects and other invertebrates describe only net assimilation–equivalent to apparent digestible energy (Harris 1966)–and do not reflect true digestive efficiency as often implied in the literature.
The Ecological Consequences of Interspecific Territorial Behavior in Birds
Authors: Murray Bertram G.
Published: May 2006

When considering cases in which territorial aggression occurs between species, we find that the relationship varies with the species' geographical and ecological distributions. If similarly sized species are narrowly sympatric or are widely sympatric but normally occupy different habitats, they both are interspecifically territorial and maintain mutually exclusive territories. If similarly sized species are widely sympatric and are common in the same habitats, one species is interspecifically aggressive and the other species flies away when chased. In this paper I present a model that explains these observations. I propose that interspecific territoriality can account not only for these differences in behavior and habitat but also for differences in foraging behavior and bill shape between sympatric species. The last three differences have usually been explained to be consequences of interspecific competition for food. The assumptions of the model proposed here are that (i) interspecific territoriality is misdirected intraspecific territoriality, (ii) territorial behavior prevents some individuals from breeding in optimal habitat, (iii) the individuals of one species are usually dominant over the other species in interspecific encounters, and (iv) of the habitats available to two interspecifically territorial species in their area of sympatry, one habitat is optimal for them both. This model is unusual in that a corollary of assumption (i) is that interspecific territoriality is not an adaptive characteristic, contrary to the assumptions of earlier writers. Nevertheless, the model is interesting and worth consideration because of the range of observable phenomena that are predicted.
Self‐Absorption Corrections for the ^(14)C Method with BaCO_3 for Measurement of Primary Productivity
Authors: Wood Kenneth G.
Published: May 2006

Self—absorption of (14)C beta radiation is shown to follow an exponential relationship under certain conditions. A new method of BaCO(2) fixation of activity is presented by which it is possible to determine productivity without using the efficiency of the detector in the calculations. Many objections to the Geiger—Muller method are explained, and corrections are suggested for the methods of Steemann Nielsen and of Sorokin.
Phytoplankton Ingestion by the Fingernail Clam, Sphaerium Transversum (Say), in Pool 19, Mississippi River
Authors: Gale William F. , Lowe Rex L.
Published: May 2006

In Pool 19 of the Mississippi River, the fingernail clam, Sphaerium transversum, appears to feed non—selectively on phytoplankton, although green algae were in higher percentages in guts than in plankton samples. Diatoms were of paramount importance in clam guts and water samples during most sampling periods, especially from December to April when mean monthly water temperatures were less than 4 degrees C. Ingestion by clams was heaviest in spring, early summer, and fall. Clams appeared to stop ingesting when water temperatures fell to about 2—4 degrees C. In February and March, 80—90% of the clams had ceased ingesting. Ingestion did not cease simultaneously in all clams. Throughout the year some contained little or no phytoplankton. Much of the phytoplankton in the gut near the anus appeared completely undigested. Phytoplankton diversity (d) in clam guts and in water was high in July and August and low in February and March. A maximum of 33 phytoplankton genera occurred in clams in August; 38 genera were present in water samples in July and August. Concentrations of over 50,000 plankters/ml (primarily Stephanodiscus hantzschii) occurred in March 1968; minimum concentrations occurred in July.
Invasion and Development of Beaked Hazel in Red Pine Stands in Northern Minnesota
Authors: Tappeiner John C.
Published: May 2006

Invasion of red pine stands in northern Minnesota by beaked hazel occurred mainly by seeding, and dense undergrowths were formed by a coalescence of many individual clones (about 2,000/acre). In young undergrowths, where beaked hazel was becoming established, 25—43% of the individuals were in the seedling stage under 12 years old, and 72—92% of the clones were under 20 years old. Clonal development, which is slow and limited, begins with the initiation of underground stems when seedlings are 7—12 years old. From 46% to 73% of the clones were only 30 cm in diameter or under, and the largest clone (over 30 years old) occupied an area of only 1.2 by 1.8 m. The control of beaked hazel undergrowth made be possible by light burning while the plant is in the seedling and young clonal stage and by controlling seed source.
Estimates of Water Loss and Its Relation to Environmental Parameters in Douglas‐Fir Saplings
Authors: Hinckley Thomas M. , Scott David R. M.
Published: May 2006

Water use by plantation Douglas—fir (Pseudotsuga menziesii [Mirb.] Franco) cannot always be predicted from environmental parameters. Under conditions of low soil—water content, no significant correlations were found between solar radiation or air temperature, or both, and sap flow. However, highly significant correlations were observed after soil—moisture recharge had occurred. Zones of xylem sap pressure and relative stomatal apertures were found within the crowns of 6—m high trees. Vertical zones of xylem sap pressure seemed to be controlled by differential stomatal closure which, in some cases, acted independently of crown microenvironment. However, differences in xylem sap pressures between the north and south sides of the trees could readily be explained by differences in microenvironment.
Carbon xerogels as catalyst supports: Study of mass transfer
Authors: Job Nathalie , Heinrichs Benoît , Lambert Stéphanie , Pirard Jean‐Paul , Colomer Jean‐François , Vertruyen Bénédicte , Marien José
Published: May 2006

Hydrodechlorination of 1,2‐dichloroethane on Pd‐Ag alloys was used as a test reaction in order to study mass transfer in carbon xerogel supports. The selected supports were obtained from evaporative drying and pyrolysis of resorcinol‐formaldehyde aqueous gels. Since the pore texture of these materials can be tailored through the adequate choice of the gel synthesis conditions, the maximum pore size of the supports was fixed at 10 × 10−9 m, 30 × 10−9 m (mesoporous supports), or 70 × 10−9 m (macroporous support). One Pd‐Ag/activated carbon catalyst was also prepared for comparison. Diffusional limitations in mesoporous xerogels and in the active charcoal were highlighted by catalytic measurements with pellets of increasing size (≤ 1.125 × 10−3 m); the effectiveness factor of the catalyst decreases when the pellet size increases. On the contrary, it remains equal to 1 for the macroporous support, whatever the pellet size, which shows that diffusional limitations can be completely avoided by choosing an appropriate pore size range. © 2006 American Institute of Chemical Engineers AIChEJ, 2006
Covalent linkages between cellulose and lignin in cell walls of coniferous and nonconiferous woods
Authors: Jin Zhenfu , Katsumata Kyoko S. , Lam Thi Bach Tuyet , Iiyama Kenji
Published: May 2006

Covalent linkages between wall polysaccharides and lignin, especially linkage between cellulose and lignin were discussed by carboxymethylation technique of whole cell walls of coniferous and nonconiferous woods. Hydroxyl groups of plant cell walls polysaccharides were highly substituted, but not those of lignin by carboxymethyl groups under the used conditions, and separated into water‐soluble and insoluble fractions by water extraction. Carboxymethylated wall polysaccharides linked covalently with lignin were distributed into the water‐insoluble fractions. Composition of carboxymethylated sugar residues in the both fractions was analyzed quantitatively by 1H NMR spectroscopy after hydrolyzation with D2SO4 in D2O. More than half of cellulose linked covalently with lignin in coniferous wood, but only one‐sixth of cellulose was involved in the linkage in nonconiferous wood. The major noncellulosic wall polysaccharides of coniferous wood also linked significantly with lignin. On the other hand, noncellulosic wall polysaccharides of nonconiferous wood were involved slightly in the covalent linkage with lignin. The situation of linkage between wall polysaccharides containing cellulose and lignin was visualized by scanning electron micrographs. © 2006 Wiley Periodicals, Inc. Biopolymers 83: 103–110, 2006

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Dynamic contrast-enhanced magnetic resonance imaging is a poor measure of rectal cancer angiogenesis
Authors: Atkin G , Taylor N J , Daley F M , Stirling J J , Richman P , Glynne-Jones R , d'Arcy J A , Collins D J , Padhani A R
Published: May 2006

Background

The aim of this study was to investigate the use of magnetic resonance imaging (MRI) for non-invasive measurement of rectal cancer angiogenesis and hypoxia.

Methods

Fifteen patients with rectal adenocarcinoma underwent preoperative dynamic contrast-enhanced (DCE) and blood oxygenation level-dependent (BOLD) MRI. Microvessel density (CD31 level), and expression of vascular endothelial growth factor (VEGF) and carbonic anhydrase (CA) 9 were measured immunohistochemically in histological tumour sections from 12 patients. Serum VEGF levels were also measured in 14 patients. Correlations between quantitative imaging indices and immunohistochemical variables were examined.

Results

There was good correlation between circulating VEGF and CD31 expression (rs = 0·88, P < 0·001). CD31 expression did not correlate with any dynamic MRI parameter, except transfer constant, with which it correlated inversely (rs = −0·65, P = 0·022). Tissue and circulating VEGF levels did not correlate, and neither correlated with any tumour DCE MRI parameter. No relationship was seen between BOLD MRI and CA-9 expression.

Conclusion

The negative correlation between transfer constant (reflecting tumour blood flow and microvessel permeability) with CD31 expression is paradoxical. DCE MRI methods for assessing tissue vascularity correlate poorly with histological markers of angiogenesis and hypoxia, suggesting that DCE MRI does not simply reflect static histological vascular properties in patients with rectal cancer.
Novel stent system for bifurcation lesions: Examination by intravascular ultrasound
Authors: Miyazawa Akiyoshi , Webster Mark W.I. , Fitzgerald Peter J. , Ormiston John A.
Published: May 2006

Bifurcation disease represents a mechanical and biological challenge for definitive interventional treatment. This case report discusses an experience with a novel stent system designed for the treatment of bifurcation lesions. © 2006 Wiley‐Liss, Inc