bluuebunny/crossref_metadata_2025 huggingface dataset:
Community Responses to Variable Predation: Field Studies With Sunfish and Freshwater Macroinvertebrates
Authors: Butler Mark J.
Published: April 2006

I studied the impact of variable predation by bluegill sunfish on macroinvertebrate prey in a North Florida lake. Underwater time—lapse cinematography and censuses of bluegill abundances in shallow, middepth, and deep habitats permitted estimation of predation intensity and variability within and among lake habitats. I then incorporated predation rates typical of the middepth zone in caging experiments where predation fluctuated in one treatment and remained constant in another. Prey community structure was subsequently monitored for 1 yr under variable, constant, ambient, and no predation regimes. Patchy, temporally variable predation characterized middepth and deep lake habitats, whereas in the shallow zone predation was relatively constant and homogeneous. Predation varied significantly every 2—4 wk in the middepth zone, but varied little between consecutive weeks or days. Caging experiments revealed that variable predation altered prey community composition and increased the mean size and size range of some prey (e.g., Odonate) as compared to the constant predation treatment. Prey abundances also appeared more heterogeneous among cages (patches) and varied more temporally under a variable predation regime. However, total prey abundance, species abundance, and within—patch spatial heterogeneity did not differ among predator treatments. In general, the macroinvertebrate community exposed to variable predation more closely approximated the natural middepth zone community than that from the constant predation regime. Previous studies of fish predation on macroinvertebrate communities have concentrated on shallow littoral habitats, but these results suggest that conclusions drawn from shallow habitats may not be representative of all lake zones. Variable predation may occur in many systems, and may contribute substantially to the spatial heterogeneity, temporal inconstancy, and species composition of prey communities.
Measurement of the Realized Qualitative Niche: Environmental Niches of Five Eucalyptus Species
Authors: Austin M. P. , Nicholls A. O. , Margules C. R.
Published: April 2006

A method is described, using Generalized Linear Modelling, for determining the qualitative environmental realized niche (QERN) of plant species. Five species of Eucalyptus growing in south—eastern Australia are used as examples. The frequency of each species occurrence in a data set comprising 6080 observations over an area of ≈40 000 km2 is modelled as a function of four environmental variables: mean annual rainfall, mean annual temperature, a solar radiation index, and rock type. The position and shape of the response of a species to these four variables is the species' QERN. The effect of rock type on the distribution of each species was found to be highly significant. To reduce model complexity, the data were stratified on rock type, and models for each species were generated for the two common rock types, granites and soft sediments. Whilst the model—fitting procedure generally is the same, each species' response demanded some modifications of the procedure. The continuous variates, mean annual temperature, mean annual rainfall, and solar radiation index, were categorized so that the magnitude of the model coefficients from each category would indicate the shape of each species' response. Continuous functions were then fitted to the categorical response shapes. Of the 10 models (5 species and 2 rock types) 5 revealed a skewed response to one or more of the environmental variables, one was linear, and two were bell shaped. Two more models revealed complex response shapes, suggesting that the environmental variables were inappropriate or insufficient to model those species' realized niches. The results provide evidence for asymmetric responses of species to environmental variables contrary to the bell—shaped symmetrical responses commonly assumed in ecological theory. Models of species' realized niches are necessary in community ecology to describe the role of environment, prior to studies on the role of competition in determining community composition. Limitations of the models, both statistical and ecological, are considered, with suggestions for improvements.
Competition, Disturbance, and Community Organization: The Provision and Subsequent Utilization of Space in a Rocky Intertidal Community
Authors: Dayton Paul K.
Published: April 2006

An understanding of community structure should be based on evidence that the growth and regulation of the component populations in the community are affected in a predictable manner by natural physical disturbances and by interactions with other species in the community. This study presents an experimental evaluation of the effects of such disturbances and competitive interactions on populations of sessile organisms in the rocky intertidal community, for which space can be demonstrated to be the most important limiting resource. This research was carried out at eight stations on the Washington coastline which have been ranked according to an exposure/desiccation gradient and subjected to comparable manipulation and observation. Physical variables such as wave exposure, battering by drift logs, and desiccation have important effects on the distribution and abundance of many of the sessile species in the community. In particular, wave exposure and desiccation have a major influence on the distribution patterns of all the algae and of the anemone Anthopleura elegantissima. The probability of damage from drift logs is very high in areas where logs have accumulated along the intertidal. Log damage and wave exposure have complementary effects in the provision of free space in a mussel bed, as wave shock enlarges a patch created by log damage by wrenching the mussels from the substratum at the periphery of the bare patch. Competition for primary space results in clear dominance hierarchies, in which barnacles are dominant over algae. Among the barnacles, Balanus cariosus is dominant over both B. glandula and Chthamalus dalli; B. glandula is dominant over C. dalli. The mussel Mytilus californianus requires secondary space (certain algae, barnacles, or byssal threads) for larval settlement, but is capable of growing over all other sessile species and potentially is the competitive dominant of space in the community.
Resource Heterogeneity Fosters Coexistence of a Mite and a Midge in Pitcher Plants
Authors: Naeem Shahid
Published: April 2006

Resource heterogeneity promotes coexistence between two competing species, Sarraceniopus darlingtoniae, a slime mite, and larvae of Metriocnemus edwardsi, a midge, which live together in pitchers of Darlingtonia californica, the California pitcher plant. Both species depend on resources derived from the decomposing insects captured by the pitchers. Experimentation revealed that midge larvae consumed resources at a greater rate than mites and that the densities of the two species are negatively correlated. These results indicate that M. edwardsi is a potential dominant competitor with S. darlingtoniae. Competition theory predicts that the presence of midge larvae should lead to the competitive exclusion of mites, yet these species coexist in field populations. This seeming paradox can be explained by temporal and spatial heterogeneity in resources. Midge larval density is generally associated with expected resource levels of pitchers, whereas mites are found in greatest abundance in pitchers whose resources differ from expected. This pattern suggests that the effects of competition vary and are strongest when actual resource levels equal expected resource levels. When resource levels are above expected levels, coexistence occurs. These results support Levins' (1979) model for coexistence of two species on a single resource. The implications of this study to the general debate over the role of interspecific competition in structuring communities are discussed.
Obtaining Birth and Mortality Patterns From Structured Population Trajectories
Authors: Wood S. N.
Published: April 2006

A method is presented for unravelling the demographic equation for structured populations. A solution to the McKendrick—von Foerster equation is constructed using spline functions and this is fluted to stage—structure population data in such a way that the solution is smooth, positive, and does not imply negative death rates. The smoothness of the surface, and hence the complexity of the population model, is determined in a statistically optimum manner using cross validation. Time— and age—dependent death rates can be obtained as well as time—dependent birth rates. Confidence intervals are obtained for population size and death rates that give a 95% probability that the true population dynamics are within the intervals. Practical application of the method is demonstrated, and comparison made with three alternative methods. The method requires estimates of stage populations at a series of times and estimates of the durations of those stages, or age ranges covered by the stages. The stage durations may vary with time.
The Color of Light in Forests and Its Implications
Authors: Endler John A.
Published: April 2006

Forests exhibit much variation in light environments, and this can affect communication among animals, communication between animals and plants, photosynthesis, and plant morphogenesis. Light environments are caused by, and can be predicted from, the geometry of the light paths, the weather conditions, and the time of day. The structure of forests leads to four major light habitats when the sun is not blocked by clouds: forest shade, woodland shade, small gaps, and large gaps. These are characterized by yellow—green, blue—gray, reddish, and "white" ambient light spectra, respectively. When the sun is blocked by clouds, the spectra of these four habitats converge on that of large gaps and open areas, so the single light environment during cloudy weather will be called open/cloudy. An additional light environment (early/late) is associated with low sun angles (near dawn or dusk); it is purplish. Each light environment is well defined and was found in forests of Trinidad, Panama, Costa Rica, Australia, California, and Florida. Scattered literature references suggest similar patterns elsewhere in North America, Europe, and Java. Perceived colors of animals, flowers, and fruits depend upon the interaction between ambient light color and the reflectance color of the animal or plant parts. As a result, an animal or plant may have a different appearance in each environment, i.e., a color pattern may be relatively cryptic in some light environments while relatively conspicuous in others. This has strong implications for the joint evolution of visual signals and vision, as well as microhabitat choice. Plant growth and form may also be affected by variation in the color of forest light.
Disturbance, Competition, and Herbivory Effects on Ragwort Senecio Jacobaea Populations
Authors: McEvoy Peter B. , Rudd Nathan T. , Cox Caroline S. , Huso Manuela
Published: April 2006

The balance of forces determining the successful control of ragwort Senecio jacobaea by introduced insects was investigated in a field experiment by manipulating the time of disturbance, the level of interspecific plant competition, and the level of herbivory by the cinnabar moth Tyria jacobaeae and the ragwort flea beetle Longitarsus jacobaeae. We used a factorial design containing 0.25—m2 plots arranged as 4 Blocks × 2 Disturbance Time (plots were tilled in Fall 1986 or Spring 1987) × 3 Plant Competition levels (vegetation other than ragwort was Removed, Clipped, or Unaltered) × 2 Cinnabar Moth levels (Exposed, Protected) × 2 Flea Beetle levels (Exposed, protected). The response of ragwort was measured as colonization, survivorship, and reproduction of the first ragwort generation, establishment of juveniles in the second generation, and changes in ragwort biomass from 1987 through 1990. We also made annual measurements from 1987 through 1990 of the allocation of space (the limiting resource in the Unaltered competition treatment) among the categories ragwort, other species, litter, and open space. Natural enemy responses were characterized by relating variation in the concentration of enemies and the concentration of ragwort among patches. We found that abundant buried seed and localized disturbances combined to activate incipient ragwort outbreaks, and that interspecific plant competition and herbivory by the ragwort flea beetle combined to inhibit the increase and spread of incipient outbreaks. Time of disturbance had little effect on the outcome of biological control. Under conditions in the Removed and Clipped treatments (where there was sufficient open space for germination and establishment), reduction in seed production in the first generation caused by cinnabar moth larvae led to a reduction in plant numbers in the second generation, but caused only a weak effect on ragwort cover and no detectable effect on ragwort biomass over the longer term from 1986 through 1990. At the spatial scale examined, inhibition by the ragwort flea beetle and plant competition took the extreme form of elimination of all ragwort individuals except the pool of seed buried in the soil. Our findings lead us to (1) reject the view that successful biological control leads to a stable pest—enemy equilibrium on a local spatial scale, (2) strongly endorse "search and destroy" and weakly endorse "complementary enemies" strategies suggested by Murdoch et al. (1985) as ways to improve control, and (3) emphasize resource limitation in the pest at low density as a key feature distinguishing biological control of weeds from biological control of insects.
Biomass, Productivity, Leaf Longevity, and Forest Structure in the Central Himalaya
Authors: Singh Surendra P. , Adhikari Bhupendra S. , Zobel Donald B.
Published: April 2006

Patterns of leaf characteristics, forest structure, tree species diversity, biomass, and productivity across a gradient of 3300 m and 15.7°C in mean annual temperature in Kumaun, in the Indian central Himalaya, were summarized and compared to values from other similar forests. Throughout the elevational gradient, the annual rainfall was high (100—300 cm), but not correlated with elevation. Evergreen species with a 1—yr leaf life—span dominated most of the elevational transect; above 1800 m, species with deciduous and multiyear evergreen leaves were also well represented. Although variability among sites within forest types was high, a number of consistent patterns were apparent. Forests of Pinus roxburghii and those at high elevations were most consistently different from other forest types. Leaf life—span was not strongly correlated with leaf mass, specific leaf mass, or leaf production efficiency (net primary productivity per unit leaf mass), contrary to relationships presented in the literature. Tree species richness and basal area were lower than for most similar types in Nepal. Biomass and productivity of the forests in Kumaun were relatively high, compared to mean values for similar forest types elsewhere. Measured values for most variables describing these forests (but not all) fell within the ranges for the variables in similar forests worldwide. The maximal values for forest biomass remained high, 500—600 Mg/ha, up to 2600 m elevation, but declined sharply in birch forest (°170 Mg/ha) above 3100 m. Net primary productivity (NPP) varied little (15—20 Mg°ha—1°yr—1) below 2700 m, despite a 10°C gradient in mean annual temperature and marked changes in basal area, tree density, growth form, and leaf characters. The level of productivity appeared not to be limited by rainfall, forest structure, leaf type, or temperature above an annual mean of 11°C. Leaf mass (LM) varied considerably among forest types, being 3.7—8.6 Mg/ha for deciduous species, 5.7—8.9 Mg/ha for P. roxburghii, and 10.0—28.2 Mg/ha for evergreen broad—leaved species. Leaf mass duration (leaf mass x months of the year with leaves present) was related directly to NPP and inversely to leaf production efficiency (NPP/LM). These data add substantially to the data base for forest properties, especially for broad—leaved evergreen forests.
A Spatial Patch Dynamic Modeling Approach to Pattern and Process in an Annual Grassland
Authors: Wu Jianguo , Levin Simon A.
Published: April 2006

Landscapes are hierarchical mosaics of patches that differ in their age, size, shape, content, and other aspects. The Jasper Ridge serpentine grassland exemplifies hierarchical patchiness and pattern—process interactions that are common features of natural ecosystems. Gopher mounds formed each year destroy all the plant individuals underneath and result in conspicuous spatial pattern in the landscape. A snapshot of the system is, therefore, a reflection of the patch mosaic of gopher mounds that are different in age and species composition and abundance. Based on a patch dynamics perspective, we have developed a spatially explicit patch—based modeling approach to studying landscape pattern and process dynamics. The simulation model (PatchMod) has two major components: a spatially explicit, age— and size—structured patch demographic model and a multiple—species plant population dynamic model. We use this simulation model to examine the spatiotemporal dynamics of the disturbance patches and of populations of two species on the local and landscape scales. The spatial patch dynamic model can relate spatiotemporal dynamics of plant populations to the age— and size—structured disturbance patch population, taking into account variability in microhabitats, complexity in patch overlap, and patch—based plant competition. The localized gopher disturbances can significantly structure the vegetation dynamics at the landscape level. Local populations at the patch level may go extinct frequently, though metapopulations may show little fluctuation. Disturbance promotes coexistence of Bromus mollis and Lasthenia californica by divorcing local competitive exclusion and global extinction. The functional representation of an ecological relationship such as density—dependent fecundity at the local patch scale may be transmuted by patchiness at the landscape scale.
Herbivore Effects on Phytoplankton Succession in a Eutrophic Lake
Authors: Sarnelle Orlando
Published: April 2006

Herbivory can potentially affect the speed and direction of plant succession by favoring the development of a community dominated by grazing—resistant species. This idea was tested experimentally by examining the effects of the planktonic herbivore, Daphnia, on phytoplankton succession in a naturally eutrophic lake. Phytoplankton succession was characterized by two major transitions in community structure. Algal dominance shifted from small diatoms and chlorophytes during the spring bloom to cryptophyte flagellates during the clear—water phase. After the clear—water phase, dominance shifted to filamentous blue—greens (cyanobacteria). Algal species positions in the successional sequence were repeatable from year to year, despite interannual shifts in the timing of species' peak abundances associated with a drastic change in the food web. In addition, evidence is presented to suggest that Daphnia—induced changes in water clarity may have fostered increases in epilimnetic mixing, which, in turn, may have stimulated brief blooms of large—celled algae after clear—water periods. Daphnia manipulation in large enclosures, and whole—lake observations before and after a fish kill, showed that intense grazing promoted the transition from edible, spring—bloom species to similarly edible, cryptophyte flagellates. In contrast, Daphnia grazing retarded further succession to grazing—resistant, filamentous blue—greens. Thus, the effects of herbivory on algal succession were not predictable from the relative susceptibilities of these algal species to grazing mortality. These results underscore the importance of indirect effects in the herbivore—plant interactions of planktonic communities. The observation that a single species of herbivore had opposite effects during two successional transitions implies that caution should be exercised when extrapolating grazer effects beyond the time scale of an experiment.
Competition Among Grasses Along a Nitrogen Gradient: Initial Conditions and Mechanisms of Competition
Authors: Wedin David , Tilman David
Published: April 2006

We grew four perennial grass species (Poa pratensis, Agropyron repens, Agrostis scabra, and Schizachyrium scoparium) for 5 yr in monocultures and in pairwise competition plots on an experimental nitrogen gradient. The gradient contained plots ranging from 100% sand to 100% black soil, plus plots that received additional N fertilizer. To examine the impact of initial conditions on the long—term outcome of interspecific competition, three competitive situations were created: seed vs. seed competition (both species planned simultaneously), seed invasions (each species added as seed to year—old monocultures of the other), and vegetative invasions (dividers separating adjacent monocultures of two species removed after 1 yr). Extractable soil NO3— and NH4+ were measured to test if species differences in the concentration of available soil N in monoculture (i.e., R* for N, Tilman 1982) could predict the long—term outcome of competition. By year 5, Schizachyrium displaced or greatly reduced the biomass of both Poa and Agropyron on the soil mixture gradient (the mixed soils but not the added—N plots) independent of the wide range of starting conditions. On these soils, Schizachyrium monocultures had significantly lower soil concentrations of both NO3— and NH4+ than either Poa or Agropyron monocultures. Similarly, Agropyron displaced or greatly reduced the biomass of Agrostis by year 5. Agropyron monocultures had significantly lower concentrations of NO3— and NO3— + NH4+, but not NH4+, than Agrostis monocultures. In contrast, no competitive displacement occurred in competition between Poa and Agropyron, and initial differences persisted over 5 yr. Monocultures of these two species did not differ in NO3— concentration, but did differ for NH4+ and NO3— + NH4+. Thus, species differences in ability to deplete soil NO3— successfully predicted the outcome of competition for all four species pairs on the soil mixture gradient. If resource preemption or asymmetric competition had been the mechanism of competition, initial conditions would have affected the long—term outcome of competition. Rather, these results support the R* (i.e., resource reduction) model for competition for soil N. In the added—N fertilizer plots, Schizachyrium had decreased biomass in competition with both Poa and Agropyron. However, neither Agropyron nor Poa appeared to have an advantage when they competed with each other in the added—N plots. For these three species pairs, the 5—yr results of competition in the added—N plots, which had greatly reduced light availability because of increased production and litter accumulation, depended on initial conditions. In the fourth pair, Agrostis was displaced by Agropyron in all competition treatments in the added—N plots. Thus, we cannot reject the hypothesis that resource preemption (i.e., asymmetric competition) is important in light competition.
The Pinus Contorta Forests of Banff and Jasper National Parks: A Study in Comparative Synecology and Syntaxonomy
Authors: La Roi George H. , Hnatiuk Roger J.
Published: April 2006

Pinus contorta Dougl. (lodgepole pine) is the most important seral tree species in the Canadian Rocky Mountains, forming a complex mosaic of even— and several—aged forests of fire origin over a wide range of elevations and habitats. East of the Continental Divide in Alberta it is the most abundant tree of montane and lower subalpine forests, due to extensive and frequent wildfires before 1910. Sixty—three mature, undisturbed P. contorta forest stands were surveyed for physiognomy, vascular floristic composition, species cover, age structure, and physical site properties. A direct gradient ordination of stands was constructed using elevation corrected to 53°N as the first axis, and Synthetic Moisture Index derived from Moisture Indicator Values of species as the second axis. Stands were classified using minimum—variance cluster analysis with species cover data, error—sum—of—squares association analysis with species presence—absence data, and dominance analysis with species based on the leading species of shrub and herb—dwarf shrub strata. Vascular species richness per stand averaged 38. Species occurring in a significantly higher percentage of stands in one national park than the other were more numerous in Banff than Jasper. Most stands were <100 yr old. Prevailing soils were Eluviated Eutric Brunisols and Orthic Eutric Brunisols. Both vascular species and community classification (syntaxonomic) units showed ecologically meaningful distribution and abundance patterns on the ordination. Though based on different criteria, the four classifications were quite similar, permitting synthesis of five PINUS CONTORTA community types (CT's), these forming an ecocline from low—elevation dry to high—elevation moist: PINUS CONTORTA/SHEPHERDIA CANADENSIS/ARCTOSTAPHY—LOS UVA—URSI (PICO/SCHA/ARUV), P. CONTORTA/S.CANADENSIS/ELYMUS INNOVATUS (PICO/SHCA/ELIN), P. CONTORTA/ALNUS CRISPA/LINNAEA BOREALIS (PICO/ALCR/LIBO), P. CONTORTA/MENZIESIA GLABEL—LA/VACCINIUM SCOPARIUM (PICO/MEGL/VASC), P. CONTORTA/LEDUM GROENLANDICUM/V. SCOPARIUM (PICO/LEGR/VASC). Stands of PICO/SHCA/ARUV are mostly seral to Pseudotsuga menziesii, of PICO/SHCA/ELIN to either Picea glauca or Pseudotsuga menziesii, of PICO/ALCR/LIBO to Picea glauca—Abies lasiocarpa, of PICO/MEGL/VASC to Picea engelmannii—Abies lasiocarpa, and of PICO/LEGR/VASC mostly to Picea mariana. Pinus contorta may be climax on dry, oligotrophic sites above the cold elevational limit of Pseudotsuga. A stable species structure (dominance hierarchy) develops in subordinate vascular strata of seral Pinus contorta forests long before the pine is replaced by climax tree species. The P. contorta forests of Banff and Jasper are compared with those of adjoining regions in Alberta, British Columbia, and Montana.
Dietary Relationships among Shrubsteppe Passerine Birds: Competition or Opportunism in a Variable Environment
Authors: Rotenberry John T.
Published: April 2006

The suggestion that in less stable environments resource limitation and subsequent interspecific competition may be relatively unimportant in determining bird community structure is explored by examining the dietary relationships within a guild of three ground—foraging passerine birds (Horned Lark, Sage Sparrow, and Western Meadowlark) in the shrubsteppe of southeastern Washington, USA, an area of severe, arid, unstable climate. General dietary analyses indicated a strong temporal component to the organization of bird diets: different species collected at the same time ate much the same things while the same species collected at different times ate different things. This pattern is reinforced by cluster analysis and stepwise discriminant analysis. Similarities in diet extended to other components as well. Dietary diversities tended to be the same for contemporaneous collections of birds, as did average prey sizes, although the latter evidenced a few statistically significant exceptions. Theoretically predicted relationships between diet and trophic structure morphology emerged only at the most general level, and even then were not always observed. In general, differences in body size or bill length were insufficient to account for variations in prey sizes, although meadowlarks did on occasion take significantly larger items than the other, smaller species. Average prey size was significantly correlated with the proportion of seeds in the diet and varied seasonally as seed consumption varied. Several aspects of this study indicate that shrubsteppe passerines are largely opportunistic in their foraging and diet selection, and that the apparent absence of fine tuning to their competitive milieu is most likely a function of the variable environment in which they coexist.
Forest Vegetation of the Big Thicket, Southeast Texas
Authors: Marks P. L. , Harcombe P. A.
Published: April 2006

Tree and shrub species composition and environmental characteristics were measured in 56 stands representing the range of natural vegetation types of the lower coastal plain of southeast Texas, and vegetation characteristics were related to the physical environment. Most of the stand—to—stand variation in species composition was expressed by the first axis of a reciprocal averaging ordination, and stand position along the first axis in turn was most highly correlated with percent sand in the surface soil (0—15 cm) (r = —.81, P <.05). The first ordination axis is interpreted as a soil moisture gradient. A more weakly expressed second axis of variation is interpreted as a soil aeration—parent material gradient (from high organic matter, low extractable Ca stands to low organic matter, high Ca stands). Overstory basal area, woody plant species richness of overstory and understory, and relative basal area of broad—leaved evergreens in both strata all varied in a regular way along the first ordination axis, having low values at the dry end, peaking in the wet—mesic range, and declining somewhat toward the wet end. Comparison of vegetation types in southeast Texas with those for the while of the southeastern. United States coastal plain showed widespread congruence of types. Major discrepancies were the lack of a pine flatwoods type in Texas and the presence in Texas of a flatland hardwood type and a pine—oak type more characteristic of the Piedmont further east. The question of fire, succession, and climax on the coastal plain is considered and it is suggested that the timing of different studies in the last 50 yr may have influenced results and interpretation.
Microbial and Animal Processing of Detritus in a Woodland Stream
Authors: Petersen Robert C. , Cummins Kenneth W. , Ward G. Milton
Published: April 2006

The detritus standing crop, microbial respiration, and macroinvertebrate biomass were examined in monthly samples from the riffle sections of a first—order woodland stream. Total detritus was remarkably constant; the average (with 95% CL) ash—free dry mass standing crop was 426.4 ± 85.9 g/m2 over the 14 mo of the study. Throughout the year benthic detritus was dominated by fine particulate detritus (<1 mm), which made up 68.9% of the total ash—free dry mass. Woody debris made up 8%, whole leaves 3.5%, and leaf fragments and other coarse particulate detritus accounted for 19.7% of the total standing crop. Decreases in standing crop were attributable to microbial respiration, macroinvertebrate assimilation, and downstream export. Microbial respiration annually removed 150% of the average standing crop, with the major effect on the smallest particle size category. Macroinvertebrate assimilation, defined as the sum of respiration and growth, removed 11.6% of the detritus standing crop annually. Shredders accounted for 20% of total animal assimilation, with the remaining 80% attributable to collectors and grazers. Based on monthly changes, it appears that total detritus standing crop is the result of the past discharge regime, which determines the overall amount of detritus present, and the rate of biological (microbial and invertebrate) processes, which determine the size and quality of the detritus particles. This suggests that detritus in streams, while strongly affected by both biotic and abiotic factors, may be in equilibrium within physical and biological constraints such that an annual steady—state system exists, similar to that for soil systems.
The Evolution of the Life Histories of Four Species of Intertidal Limpets
Authors: Parry Gregory D.
Published: April 2006

The life histories of four species of intertidal limpets, Cellana tramoserica, Notoacmea petterdi, Patella peroni, and Patelloida alticostata, which occur on the same shore but in different tidal zones, are compared. The population dynamics (recruitment, growth, and mortality) and the causes of mortality of each species are investigated. C. tramoserica and P. peroni have similar rates of growth and mortality, but P. peroni has a higher reproductive effort (the proportion of assimilated energy devoted to reproduction). Pd. alticostata has lower rates of growth and mortality than the above species, but its reproductive effort is similar to that of C. tramoserica. N. petterdi has the lowest rates of growth and mortality, but its reproductive effort is similar to, or perhaps slightly lower than that of C. tramoserica and Pd. alticostata. The causes of mortality vary among species. Predation by wrasses is the main cause of mortality of P. peroni and Pd. alticostata, which occur in the sublittoral and lower littoral zones, respectively. The principal cause of mortality of adult C. tramoserica, a midlittoral species, is starvation. N. petterdi, which occurs in the supralittoral zone, is a very long—lived species and the causes of its mortality could not be determined. Semiquantitative estimates of extrinsic adult mortality rates are obtained for the four species of limpet, and these are shown to be correlated with interspecific differences in reproductive effort. Adults of each species assume different levels of risk during reproduction. The adults of species which occur in seasonal environments appear to take greater risks when breeding than those of species which occupy more constant environments.
Longevity, Life History, and Relative Body Wall Size in Sea Urchins
Authors: Ebert Thomas A.
Published: April 2006

Annual survival rates in 38 populations of 17 sea urchins species in the Indo—West Pacific were related to relative size of the body wall and exposure to the surf. The urchin species are: Heterocentrotus trigonarius, H. mammillatus, Colobocentrotus atratus, Echinometra mathaei, E. oblonga, and Heliocidaris erythrogramma in the family Echinometridae; Prionocidaris baculosa in the Cidaridae; Stomopneustes variolaris in the Stomopneustidae; Echinothrix calamaris, E. diadema, Centrostephanus rodgersi, Diadema paucispinum, and D. setosum in the Diadematidae; Tripneustes gratilla, another Tripneustes sp. (possibly the same as T. gratilla), and Toxopneustes pileolus in the Toxopneustidae; and Salmacis belli in the Temnopleuridae. Populations were studied at Hawaii, Enewetak Atoll, Queensland, New South Wales and Western Australia, Sri Lanka, Seychelles, Kenya, Zanzibar, and Israel (Eilat). Live animals were dissected to determine the size of body components. The relative size (mass) of the body wall for a species is expressed by the constant α in the equation B = αTb, where B is wet mass of the body wall and T is total wet mass. A common β value of 0.976 ± 0.004 (SE) was used for all species, so α values can be used to compare relative body wall sizes among species. Values of α ranged from 0.966 for Heterocentrotus trigonarius (Enewetak Atoll) to 0.360 for Salmacis belli (Moreton Bay, Queensland, Australia). Parameters of the Richards growth function were determined from animals tagged with tetracy—cline. Tagged animals were collected after they had been in the field for 1 yr. Growth parameters were used with parameters from size—frequency distributions to estimate Z, the mortality coefficient. Annual survival probability p is e—z. Stepwise multiple regression was used to examine the relationship between annual survival probability (p) and two independent variables, α and E, where E is a subjective measure of exposure to surf (1 = most exposed). The function is p = 1.20α + 0.061E — 0.350. Survivorship increases with increased relative size of the body wall and with increased protection from the surf. The positive relationship between survival probability and relative body wall size supports the hypothesis that survival is related to allocation of resources to maintenance. The significance of longevity in urchins probably is that it is related to the predictability of survival of prereproductive individuals. The greater the unpredictability, the longer life must be. Long life requires a greater investment in maintenance mechanisms and hence, among other adaptations, a more massive body wall.
A Trophic Position Model of Pelagic Food Webs: Impact on Contaminant Bioaccumulation in Lake Trout
Authors: Vander Zanden M. Jake , Rasmussen Joseph B.
Published: April 2006

To test how well use of discrete trophic levels represents pelagic trophic structure, we compiled dietary data from >200 lake trout and pelagic forage fish populations and calculated a continuous (fractional) measure of trophic position for each population. Although discrete trophic levels qualitatively represent broad—scale patterns in trophic structure, pelagic food webs are characterized by complexity and omnivory, thereby limiting the ability of discrete trophic levels to quantitatively represent trophic structure in terms of mass transfer and energy flow. Lake trout trophic position, which ranged from 3.0 to 4.6, explained 85% of the between—lake variability in mean PCB levels in lake trout muscle tissue, providing a significant improvement over the use of discrete trophic levels as a predictor of contaminant levels. Having demonstrated the utility of trophic position, we developed a generalized trophic position model of lake trout food webs. This approach eliminates minor trophic linkages, calculates a fractional measure of each species' trophic position, and aggregates species of similar trophic position into trophic guilds. This realized model represents trophic structure in terms of mass transfer and accounts for the complexity and omnivory that characterize aquatic food webs. In our trophic position model, smelt (a species of pelagic forage fish) were designated a trophic guild separate from other pelagic forage fish, due to their elevated trophic position. Separate consideration of smelt was supported by elevated lake trout trophic position, PCB, and Hg levels in lakes containing smelt. Consideration of omnivory caused biomagnification factors (BMFs) to be many times higher than BMFs that ignored omnivory. These omnivory—corrected BMF estimates appeared to be more consistent with values calculated using stable nitrogen isotopes (δ15N), an alternative continuous measure of trophic position. (δ15N) provided trophic position estimates that generally corresponded with our diet—derived estimates.
Training at the Waseda Little Theatre: The Suzuki Method
Authors: Brandon James R.
Published: April 2006

During the past dozen years or so a number of contemporary theatre groups in Tokyo have been exploring, each in their own way, new and intensely theatrical approaches in the actor's art. Each group bases its work on ensemble playing, so that in the midst of the exploration, some consistency of performance style has seemed desirable. In either formal or informal ways, this usually means an actor training system created out of the group and designed for its own needs. A training system that is especially Japanese is the one developed by Tadashi Suzuki with members of the acting company of the Waseda Little Theatre (Waseda Shogekijo see T60, T65).

Suzuki formed the Waseda Little Theatre in 1965. Among the twenty members of the acting company today, seven are part of that original group. They gather four nights a week, after working at other jobs, to train under Suzuki's direction. Suzuki, with the actors, has created a series of training disciplines, combining voice and body, which, while being flexible and capable of variation, are precise in their structure.
Study of the evaporation of pollutant liquids under the influence of surfactants
Authors: Gavril Dimitrios , Atta Khan Rashid , Karaiskakis George
Published: April 2006

In the present work, reversed‐flow gas chromatography (RF‐GC) is utilized for the study of the evaporation of volatile liquids. Evaporation rates and the respective diffusion coefficients are determined for the evaporation of ethanol and 1,1,1‐trichloroethane in nitrogen, at 306.2 K. The precision (>99.5%) and accuracy of the method, as well as the uncertainty of the determined parameters, ascertain the potential of the presented methodology. The experimentally obtained evaporation rates have units of velocity, and for high volatility compounds their values are identified with the liquid film mass‐transfer coefficients. The latter compare successfully to available literature values, further ascertaining the validity of the presented methodology. The variation of the evaporation rates of ethanol and 1,1,1‐trichloroethane, in the presence of various amounts of Triton X‐100, indicates that different, but in any case high amounts of surfactant are required for the drastic retardation of the vaporization rate. The reduction of the evaporation rate can be attributed either to the formation of densely packed surface monolayers or to the formation of an insoluble monolayer. © 2006 American Institute of Chemical Engineers AIChE J, 2006
Reactive distillation design with considerations of heats of reaction
Authors: Huang Kejin , Nakaiwa Masaru , Wang San‐Jang , Tsutsumi Atsushi
Published: April 2006

Although reactive distillation columns allow direct utilization of heat of reaction to separation operation, the effectiveness of internal heat integration appears generally to be unsatisfactory and their thermodynamic efficiency could quite often be improved substantially through seeking further internal heat integration between the reaction and separation operations. Prudent arrangement of reactive section, effective determination of feed location, and deliberate distribution of catalyst constitute the three methods that can complement internal heat integration within a reactive distillation column. The reactive section is suggested to superimpose properly onto the stripping section for exothermic reactions and onto the rectifying section for endothermic reactions. Feed location and distribution of catalyst should be determined so that the effect of internal heat integration can be maximized to its fullest extent. A sequential procedure is proposed to determine an appropriate process configuration for internal heat integration within a reactive distillation column. Five reactive distillation systems, involving not only equilibrium‐limited but also kinetically controlled reactions, are used to evaluate the design philosophy proposed. It has been found that a substantial improvement in system performance can be achieved even for some reaction systems with side reactions and/or unfavorable thermodynamic properties. Seeking further internal heat integration has been demonstrated to be an effective method for refining process design of a reactive distillation column involving reactions with highly thermal effect. These conclusions are of great significance and can provide process designers with additional latitude to elaborate their process designs. © 2006 American Institute of Chemical Engineers AIChE J, 2006
Schizophrenia in an adult with 6p25 deletion syndrome
Authors: Caluseriu O. , Mirza G. , Ragoussis J. , Chow E.W.C. , MacCrimmon D. , Bassett A.S.
Published: April 2006

Chromosomal deletions at 6p25‐p24 are rare findings in patients with developmental delay. There is limited information about the adult phenotype. We present a 36‐year‐old patient with schizophrenia, mild mental retardation, progressive hearing deficits, and characteristic facial features. Ocular (Axenfeld–Rieger anomaly) abnormalities were diagnosed in infancy; vision, however, has remained unimpaired. There were no other major congenital anomalies. Brain imaging showed only minor changes. There was no family history of intellectual deficits or psychosis. Karyotyping revealed a 6p25 deletion, and detailed fluorescence in situ hybridization (FISH) analyses using 23 probes confirmed a 6.7 Mb 6p25‐pter deletion. The breakpoint is near a possible 6p25‐p24 locus for schizophrenia. Psychotic illness may be part of the neurodevelopmental abnormalities and long‐term outcome of patients with 6p terminal deletions. Other similarly affected patients likely remain to be diagnosed in adult populations of schizophrenia and/or mental retardation. © 2006 Wiley‐Liss, Inc.
Chiral separation of rac‐Ornidazole and detection of the impurity of (R)‐Ornidazole in (S)‐Ornidazole injection and raw material
Authors: Huang Jianquan , Cao Guoying , Hu Xin , Sun Chunhua , Zhang Junren
Published: April 2006

(S)‐Ornidazole is a subject of research as an antifertility agent in male animals at present. However, there seems to be no relative report on chiral separation for rac‐Ornidazole, which has been used as an effective medicine for more than 30 years. In this article, the chiral separation of rac‐Ornidazole on a Chiralcel OB‐H column based on normal‐phase high‐performance liquid chromatography (NP‐HPLC) is investigated and the methodology for detection of impurity of (R)‐Ornidazole in (S)‐Ornidazole injection and raw material is established. The novel mobile phase is utilized by mixing n‐hexane, methanol and isopropyl alcohol (95:4:1, v/v/v) instead of the typical mobile phase of n‐hexane and isopropyl alcohol, although the methanol, which offers a good resolution factor for the enantiomeric separation in this system, is not recommended on the Chiralcel OB‐H column according to the instruction supplied by Daicel Chemical Ind., LTD (Japan). Chirality, 2006. © 2006 Wiley‐Liss, Inc.
Cytokine‐induced killer cells against autologous CLL: Direct cytotoxic effects and induction of immune accessory molecules by interferon‐γ
Authors: Kornacker Martin , Moldenhauer Gerhard , Herbst Markus , Weilguni Edeltraud , Tita‐Nwa Freddy , Harter Christoph , Hensel Manfred , Ho Anthony D.
Published: April 2006

Cytokine‐induced killer cells (CIK cells), coexpressing CD3 and CD56, can be expanded from peripheral blood mononuclear cells by the timed addition of interferon‐γ (IFN‐γ), IL‐2 and OKT3. The effects of CIK cells on primary, autologous CLL cells are described. We used MACS to separate CD3+ cells for expansion of CIK cell effectors and CD19+ targets from peripheral blood of 16 CLL patients. Apoptosis was assessed by measuring annexinV staining in CLL cells. After incubation of autologous CIK with CLL, specific apoptosis in CLL cells was 15%. Coincubation with irradiated CIK cells for 48 hr before adding vital CIK cells resulted in an increased ICAM‐1 expression on CLL cells and an increase in apoptosis of CLL targets (30%). These effects were mediated by IFN‐γ secretion of CIK cells. In addition to their direct cytotoxic effect, CIK cells secrete IFN‐γ that modulates the expression of adhesion molecules on CLL cells, and this enhances apoptosis induction by cytotoxic effector cells. © 2006 Wiley‐Liss, Inc.