bluuebunny/crossref_metadata_2025 huggingface dataset:
Late‐Quaternary History of High‐Elevation Vegetation in the White Mountains of New Hampshire
Authors: Spear Ray W.
Published: April 2006

The pollen and plant—macrofossil records from four small lakes in the subalpine and alpine zone of the White Mountains, New Hampshire, give a 13 000—yr paleoenvironmental history. The White Mountains were deglaciated before 13 000 yr BP. Downwasting of the continental ice sheet was rapid. The summits projected above the ice as nunataks for only a brief period of time. Residual ice may have existed in Franconia Notch until 11 000 yr BP. From 13 000 to 11 750 yr BP a barren periglacial desert covered the highest altitudes in the White Mountains. Tundra vegetation occupied the lower slopes and valleys. The mean annual temperature was roughly 5°—10°C colder than today. Sparse tundra vegetation surrounded all four high—elevation sites from 11 750 to 10 300 yr ago and several taxa, particularly Artemisia and Caryophyllaceae, indicate disturbance. The summits were subjected to intense periglacial activity. The mean annual temperature was 4—6° lower than present. By 10 300 yr BP shrubs such as willow, juniper, and dwarf birch had invaded the tundra at Lake of the Clouds. Spruce woodland dominated the lower slopes and valleys. At 10 300 yr BP spruce populations arrived at high—elevation sites. Macrofossils of fir, birch, and shrubs also occur in sediments of this age. The temperature increased to or exceeded modern levels. Tree species did not reach the Franconia Notch sites until 9750 yr BP. At these sites the establishment of subalpine forests spanned a much shorter time period. Forest with poplar, spruce, and birch replaced the spruce woodlands of low elevations. Subalpine fir forests became well established by 9000 yr BP. Evidence from the alpine site shows that the fir trees were more abundant and treeline higher than today from 10 300 to 5000 yr BP. After 5000 yr BP, the pollen percentages of alpine indicators increased and the numbers of fir macrofossils dropped. Of the three sites in subalpine fir firest, only the lowest shows any evidence of a warmer interval in the early Holocene. Treeline is apparently a poor temperature indicator because wind and moisture are the major factors determining its position. Taxa of the Northern Hardwood Forest (e.g., white pine, hemlock, yellow birch, sugar maple, and beech) arrived at lower elevations by 6500 yr BP, but the zones of modern vegetation became established only after 2000 yr BP when spruce populations expanded at low elevations between 750 and 1200 m.
Woody Seedling Dynamics in an East Texas Floodplain Forest
Authors: Streng Donna R. , Glitzenstein Jeff S. , Harcombe P. A.
Published: April 2006

We monitored woody plant seed deposition, seedling emergence, and the survival and growth of seedlings (i.e., plants ≤0.5 m tall regardless of age) in an East Texas river floodplain forest from 1979 through 1984. In addition, we estimated the relative importance of flooding, drought, fungal attack, herbivory, proximity to a conspecific adult, and shade in causing seedling mortality. Tree species fell into two major groups on the basis of their demographic characteristics and responses to unfavorable conditions. The first group was composed of heavy—seeded species, of which water oak (Quercus nigra) was the primary example. They produced few seeds, but had high seedling survival. Seedlings of these species emerged late in the summer, thereby avoiding peak periods of flooding and damping—off mortality. Seedling survival was little affected by drought, herbivory, or proximity to a conspecific adult. The second group included most of the common tree species (e.g., ironwood, Carpinus caroliniana; sweetgum, Liquidambar styraciflua; red maple, Acer rubrum; American elm, Ulmus americana). They produced large crops of light seeds which dispersed throughout the study area. In these species, seedling survival was low for the 1st yr, but increased substantially thereafter. Flooding, drought, damping—off, proximity to a conspecific adult, and herbivory were important causes of 1st—yr seedling mortality. for these species was not constant over the growing season, but was concentrated in peaks associated with particular events (e.g., a drought in 1980, and flooding and damping—off in 1981 and 1982). Seedlings emerging earlier in the spring were usually better able to survive these periods of environmental stress. During the course of the study, extensive flooding in 1979 and during 1983—1984 resulted in increases in the proportion of water oak in the seedling layer, while periods of reduced flooding during 1980—1982 allowed several of the more prolific, lighter seeded species (especially ironwood, sweetgum, and deciduous holly, Ilex decidua) to increase in importance. The two spring—dispersing, light—seeded species, red maple and elm, emerged late in the spring and therefore increased in relative abundance during 1984 when early floods killed seedlings of earlier emerging, autumn—dispersing species. Thus, spatial and temporal variation in understory seedling composition in our study was due largely to (1) species differences in the ability to increase rapidly in numbers during favorable periods as compared to the ability to survive stressful periods, and (2) the interaction of emergence phenology with the occurrence of environmental stress. These results demonstrate that variation in flooding or other environmental stresses can alter seedling layer species composition and may thereby influence opportunities for canopy replacement, thus helping to maintain species diversity in southern floodplain forests.
Desert Rodent Community Structure: A Test of Four Mechanisms of Coexistence
Authors: Brown Joel S.
Published: April 2006

Four mechanisms of coexistence are considered that may contribute to the diversity of desert granivorous rodent communities. In the first, bush/open microhabitat selection, coexistence is possible if there is a trade—off between foraging efficiency in the bush and open microhabitats. In the second, temporal variation in resource abundances, coexistence is possible if there is a trade—off between foraging efficiency and maintenance efficiency. The first species can forage profitably on low resource abundances while the second uses dormancy to travel inexpensively in time between periods of high resource abundances. In the third, spatial variation in resource abundance, coexistence is possible if there is a trade—off between foraging efficiency and the cost of travel. The first species forages patches to a lower giving—up density, (the density of resource at which a forager ceases foraging), while the second can inexpensively travel between patches with high resource abundances. In the fourth, seasonal rotation in foraging efficiencies, coexistence is possible if there is a trade—off between the costs of foraging during different seasons. The species that is the more efficient forager changes seasonally. The first mechanism of coexistence has received much empirical attention and support. The other three have not previously been considered with desert rodents. In a community of four granivorous rodent species, I used artificial seed patches to measure species— and habitat—specific foraging efficiencies and live—trapping to measure population sizes and mean distances between recaptures. Of the four, the fourth mechanism of coexistence best explained the presence of Perognathus amplus, Dipodomys merriami, and Spermophilus tereticaudus in the community. Each species enjoyed a period of the year during which it was the most efficient forager. Furthermore, the annual population densities of these three species fluctuated out of phase. Seasonal changes in species—specific predation risks and body size—dependent metabolic costs may have accounted for these results. The third mechanism of coexistence best explained the presence of Ammospermophilus harrisii in the community. This species preferred to forage a large number of widely spaced patches to a high giving—up density rather than forage a few patches to a low giving—up density.
Host Plant Selection by Battus philenor Butterflies: The Roles of Predation, Nutrition, and Plant Chemistry
Authors: Rausher Mark D.
Published: April 2006

In a previous study it was demonstrated that a major selection pressure responsible for seasonal changes in the searching and oviposition preferences of the pipevine swallowtail butterfly, Battus philenor (Lepidoptera: Papilionidae), is a seasonal increase in the disappearance rate of early—instar larvae from one of their two host plants in east Texas, Aristolochia reticulata (Aristolochiaceae). The primary objective of this study was to determine the causes, both proximate and ultimate, of that increased disappearance rate. The results may be summarized as follows: 1) The seasonal increase in disappearance rates of larvae feeding on A. reticulata plants is due primarily to a decrease in the size at which larvae disperse from their original host plant. No seasonal increase in the intensity of predation on larvae was detected. 2) Larvae readily consume the young foliage of A. reticulata plants but seldom accept mature foliage. 3) The amount of A. reticulata foliage that is acceptable to larvae decreases between early April and late May. This decrease explains the seasonal decrease in the size at which larvae disperse from their original host plant. 4) Growth rates, corrected for variation in consumption rates, are much lower for larvae fed mature leaves than for larvae fed young leaves. 5) Poor larval growth on mature leaves appears to be due to two effects of sclerophyllization: low nitrogen content and increased toughness. No effects of digestibility—reducing plant secondary compounds were detected. 6) For A. reticulata plants in the field, the probability that a leaf will be eaten once it is discovered by a larva is lower for mature leaves than for young leaves. 7) For A. serpentaria plants, which grow sympatrically with A. reticulata, mature leaves and young leaves are equally acceptable to larvae. Mature A. serpentaria leaves are not markedly sclerophyllous. These results indicate that the causes of the observed seasonal increase in disappearance rates of larvae on A. reticulata can be traced ultimately to changes in the nutritional content of the foliage as it ages. They also suggest that a seasonal deterioration in the nutritional quality of A. reticulata foliage is a major selection pressure leading to the observed seasonal shift in the searching and oviposition preferences of females from A. reticulata in the early spring to A. serpentaria late in the spring. Finally, the results provide evidence supporting the contention that an important ecological function of sclerophylly is to defend plants from herbivores.
Community Organization in Temperate and Tropical Rocky Intertidal Habitats: Prey Refuges in Relation to Consumer Pressure Gradients
Authors: Menge Bruce A. , Lubchenco Jane
Published: April 2006

The structure of a tropical rocky intertidal community on Taboguilla Island on the Pacific coast of Panama is characterized by extremely low abundances of noncrustose algae and sessile animals, indistinct vertical zonation patterns (a result of the low abundances), and the occurrence of most invertebrates (except barnacles) and upright algae in holes and crevices (as opposed to open, smooth surfaces). This contrasts strikingly with two temperate rocky intertidal communities, which have high covers of plants and animals, more obvious zones, and invertebrates and upright algae occurring both on relatively homogeneous surfaces and in holes and crevices. Field experiments were done and observations were made in the Panama community to test the effects of different types of consumers (both predators and herbivores) on their prey and on the types of escapes utilized by the prey. Consumer exclusion experiments suggest that (1) predation and herbivory are severe at all times of the year, (2) consumer pressure is a cumulative function of many types and species of predators and herbivores, (3) the primary effect of larger fishes and crabs is to restrict most prey to three—dimensional refuges (holes and crevices), and (4) the primary effect of smaller consumers, mostly invertebrates, is to keep abundances of the prey low. Thus, in the Panama system, three—dimensional space (holes and crevices) appears to be particularly important as a refuge from consumers, while escapes from consumers in body size, time, or two—dimensional space (e.g., in a higher zone) documented so frequently in temperate areas, assume secondary importance for many prey. This restriction of the types of escapes utilized by prey species appears to be a consequence of two main factors: the presence of fast—moving consumers (i.e., herbivorous and predaceous fishes and herbivorous crabs which are absent or rare in the two temperate communities), and the year—round foraging of all consumers.
Late‐Pleistocene Vegetational Changes in Northeastern North Carolina
Authors: Whitehead Donald R.
Published: April 2006

Regional and local environmental changes spanning the last 30 000 yr have been reconstructed based on paleoecological studies of the sediments in Rockyhock Bay, a peat—filled Carolina Bay in Chowan County, northeastern North Carolina. During the Plum Point Interstadial (30 000—21 000 BP), temperate forests with both deciduous and coniferous taxa occupied the area. Some boreal elements and constituents of northern hardwoods forests were also present. Climate was somewhat cooler than at present, and Rockyhock was a shallow—water body. During the full—glacial and most of the late—glacial (21 000—10 000 BP), the regional forests were boreal in character and were dominated by northern pines and spruce. Many other boreal taxa were present. The climate was colder, more continental, and drier than at present. Water table in the basin was higher, and there was a dense growth of Isoetes on the bottom sediments. There is indication of slight lowering of water table about 14 400 yr ago. Deciduous forests containing constituents of modern white pine—hemlock—northern hardwoods forests replaced the boreal forests about 10 000 yr ago. By 7200 yr ago, most of the "northern hardwoods" taxa had been replaced by other deciduous species including sweetgum. Between 7200 and 5000 yr ago, the water table dropped, peat began to form throughout the basin, and swamp forests with blackgum, cedar, magnolia, and may swamp shrubs began to develop. The swamp forests were modern in aspect by 4000 yr ago. During the last 4000 yr, there is indication of at least one secondary successional change within the bay, perhaps induced by a disturbance such as fire.
Experimental Analyses of Structural Regulation in a Marine Sand Community Exposed to Oceanic Swell
Authors: VanBlaricom Glenn R.
Published: April 2006

The development of general theories concerning the origin and maintenance of community organization in marine sedimentary environments will benefit from studies of similar processes in the widest possible range of habitat types. The roles of predation and disturbance by large epibenthos are thought to be significant in many such habitats, but the bulk of recent experimental confirmation comes from shallow areas protected from oceanic swell. This field experimental study examines relationships among demersal predators, predator—caused local disturbance, infauna, and infaunal food resources in an exposed marine sand habitat at 17—m depth in southern California, USA. Manipulation of predator densities with exclusion cages, simulation of biological disturbance, and study of dispersal and habitat selection of infauna showed the importance of recurrent local disturbances by the rays Urolophus halleri and Myliobatis californica, which dig pits to expose prey but clear other infauna in the process. Benthic invertebrate populations show complex but reproducible patterns of reoccupation of disturbed sites. The most striking aspect of these patterns is active selection of recently formed pits by certain species. Ray pits are sites of accumulation for organic material on which most of the infauna feed. Experiments showed that populations which rapidly colonize new ray pits are responding to the concentration of food resources which are otherwise sparsely distributed. Responses of infauna to ray disturbance are correlated with postlarval swimming capability and method of feeding. Early colonists are active nocturnal swimmers that feed on detritus at the sand—water interface. Such features allow efficient exploitation of patchy, ephemeral concentrations of organic matter. Later arrivals are primarily subsurface feeders with limited swimming activity. The relative abundances of infauna are sensitive to seasonal changes in ray disturbance rates. Early pit colonists predominate when disturbance rates are high. The ray disturbance phenomenon produces a persistent mosaic of patches in various stages of infaunal recolonization. Other experiments showed the importance of predation by sea stars (Astropecten verrilli) and speckled sand dabs (Citharichthys stigmaeus). Sea stars consume crab larvae soon after they settle to the bottom and begin metamorphosis. During the study, recruitments of two crabs, Cancer gracilis and Portunus xantusii, were much reduced by sea star predation. A caging experiment indicated that high—density populations of P. xantusii have important negative effects on some infaunal populations. Thus, sea star predation on young crabs is important to the maintenance of infaunal community organization. Sand dabs consume infauna which are flushed into the water column or onto the sand surface by digging rays. This commensal behavior constitutes an important additional source of mortality for populationsthat are otherwise unavailable as food for sand dabs, which are visual predators.
The Demography of Jack‐in‐the‐Pulpit, a Forest Perennial that Changes Sex
Authors: Bierzychudek Paulette
Published: April 2006

A size—classified transition matrix model of the demography of Arisaema triphyllum, a perennial herb of temperate deciduous forest, was constructed from 3 yr of field data from two different sites. Arisaema is quite unusual in that individuals change sex in a pattern determined by their sizes: small individuals do not flower, larger individuals reproduce as males, and the largest as females. As plants increase or decrease in size, they also may change sex. Though demographic parameters varied with the site and with the year, some consistent patterns were seen Mortality rates ranged from 20 to 40%/yr for small, nonflowering plants, but decreased to much lower levels as plants reached reproductive size. For these large plants, mortality rates did not differ between sexes or among size—classes. Because rates of sexual reproduction were severely pollinator limited, levels of seed production were low (averaging 7 seeds°female—1°yr—1) and were not correlated with plant size. All plants engaged in clonal reproduction, regardless of their size. Transition matrices based on these data were compared statistically and were found to vary in time, as a result of year—to—year environmental variability. No population had achieved a stable size distribution. The classical method of calculating rate of increase, @l, was therefore rejected, and an alternative method incorporating temporal stochasticity substituted. A sensitivity analysis was performed to evaluate the effect on population growth of changing various life history parameters. Differences in rates of individual growth and of clonal reproduction were found to be largely responsible for the relative success of the two populations, one of which was increasing, the other declining. Arisaema's status as a climax—forest herb suggests that temporally varying transition matrices might be common even in environments traditionally regarded as "stable." The prevalence of temporal variability has consequences both for the future direction of demographic theory and for the design and analysis of field studies.
Community Structure and Productivity in Ceanothus Chaparral and Coastal Sage Scrub of Southern California
Authors: Gray John T.
Published: April 2006

Adjacent, 22—yr—old stands of evergreen chaparral and drought—deciduous coastal sages scrub at a low—elevation site near the ocean in the Santa Monica Mountains of California were analyzed. The chaparral is a pure stand of Ceanothus megacarpus and has an aboveground live biomass of 6482 g/m2. The coastal sage scrub is co—dominated by Salvia leucophylla and Artemisia californica and has an aboveground live biomass of 925 g/m2. Attached and standing dead wood comprise 15% and 21% of the total live and dead biomass in the chaparral and coastal sage scrub, respectively, Mean annual aboveground primary production in Ceanothus chaparral is 1056 g°m—2°yr—1, while litterfall is 801 g°m—2°yr—1. In the coastal sage scrub, mean annual primary production is 355 g°m—2°yr—1 and litterfall, 199 g°m—2°yr—1. The drought—deciduous shrubs begin leaf production 1—3 wk after the initial winter rains and continue for 5—7 mo; thereafter, the shrubs lose most of their leaves in the summer. Twig and flower/fruit production continues for several months after leaf growth has ceased. Artemisia and Salvia have no measurable growth for 2 and 4 mo, respectively. In Ceanothus, leaf production begins 3—4 mo after the first rains of winter, and may or may not continue through the summer. Wood production and flowering/fruiting coincide with foliage production. Ceanothus may show measurable aboveground growth for up to 11 mo of the year. Flower production does not occur each year; however, in a flowering year, the production of all reproductive structures is very high (151 g°m—2°yr—1). The length of the measurable aboveground growing season in the two growth forms does not fully account for the great differences in their annual net primary production. The high net primary production in the Ceanothus chaparral is much greater than other evergreen, mediterranean—type ecosystems and most temperate shrub communities. This high productivity is attributed to a tolerance of low water potentials, high photosynthetic rates, and an efficient use of nutrients in C. megacarpus. The high production in Ceanothus chaparral and the potential for reproduction in the coastal sage scrub suggest that the commonly ascribed senscence of mature shrub stands may not occur in these communities.
The Reproductive Cycle of Microtus ochrogaster in Eastern Kansas
Authors: Rose Robert K. , Gaines Michael S.
Published: April 2006

About 800 Microtus ochrogaster were live—trapped at biweekly intervals from May 1971 through March 1973 in 3 grassland study areas in eastern Kansas, USA. Details of reproduction were determined by autopsy. Population density increased through the first winter, reached a peak in April 1972, then declined sharply during that summer and beyond. Body length, but not body mass, tended to be positively related to density. Both sexes matured at about the same weight; development was somewhat prolonged during the winter months, especially in the winter preceding the population peak. Pregnancy rates were high, approaching maximal iteroparity, throughout the study, with intervals of nonbreeding in both Julys, and in August and December of the population decline. Embryo counts increased significantly during the months of peak density but did not diminish in the period of the population decline. There was no association between either maternal weight or parity and number of embryos. Corpora counts were not higher in heavy or multiparious ♀ ♀, nor did the level of prenatal mortality increase during the period of greatest density. Except for a few individuals taken in July and August 1971, ♂ ♂ with a mass 30 g or more were judged to be fertile, as were a majority of the 20 to 29—g ♂ ♂. Body weight and testes weight were significantly correlated in fertile ♂ ♂ but not in nonfertile ♂ ♂. These reproductive findings were applied to a model of population regulation of microtine cycles. The pattern of reproduction of Kansas and Indiana prairie voles was compared. Three concordant lines of evidence seem to indicate that Kansas and possibly other geographical populations of prairie voles have adjusted the breeding schedule to accommodate both hot and dry summers and cold, snowy winters. Pregnancy rate, litter size, and adjusted testes weight all show a significant increase in March–April and September–October and a decrease in midsummer and midwinter. Thus the pattern of reproduction of Kansas prairie voles may represent a composite of the patterns shown by the dry—adapted species, such as Microtus californicus, and the cold—adapted microtines, such as Microtus pennsylvanicus. Based on the observations of this study, Kansas prairie voles seem to have adjusted to both harsh seasons by breeding more or less continuously, with the midsummer depression possibly reflecting the Great Plains origin of the species, and the winter depression being a facultative response to weather, density, or quality of habitat.
Community Structure, Dynamics and Nutrient Cycling in the Okefenokee Cypress Swamp‐Forest
Authors: Schlesinger William H.
Published: April 2006

Aspects of community structure and nutrient circulation are described for the cypress (Taxodium distichum) forest in Okefenokee Swamp, Georgia, USA. This bog environment is characterized by low nutrient availability and large peat accumulations. The tree stratum of the forest is dominated by cypress, which is probably due to recurrent understory fires which eliminate other swamp species. In stands throughout the cypress forest, the density and total basal area of living stems >4 cm diameter vary greatly, but mean values (1,465 stems/ha; 52 m2/ha) are high compared to upland forests. Natural thinning appears to be unimportant. Abundant standing dead trees suggest that differences in density among stands are due to past differences in the frequency and intensity of forest fires during periodic droughts. At an intensive study site, biomass and net primary production were measured using techniques of dimension analysis. Cypress trees compose 98% of the total forest above—water biomass of 307 tonnes/ha. Most of the cypress biomass is in tree boles (96%), little is in foliage (0.8%). Presumably due to the acid, nutrient—poor conditions in the swamp, total above—water net primary productivity is low (692 g°m—2°yr—1); the high biomass is the result of the old age (150 yr) of the stand and the high density of trees. Cypress net production is largely channeled into bole wood (41%) and current twigs with needles (41%). It appears that in recent years, above—water biomass has been maintained at a constant level by fire—induced thinning. The nutrient pools in the above—water community are large (666 kg/ha Ca, 111 kg/ha Mg, 230 kg/ha K, 996 kg/ha N and 46 kg/ha P). These nutrients are largely contained in cypress boles and do not freely circulate. The annual nutrient uptake in the forest is rather small compared to that in upland forests. The nutrient uptake (54 kg°ha—1°yr—1 Ca, 11 each for Mg and K and 2.3 for P) is largely channeled to the small amount (231 g/m2) of very efficient cypress foliage. Foliage abscission and foliar leaching by rainfall return 73 to 91% of the annual nutrient uptakes each year; therefore, there are only small permanent additions of nutrients to the above—water pools each year. Except for K which is apparently reabsorbed from foliage before abscission, the cypress trees do not appear to conserve foliar nutrients. However, nutrient conservation may be effected by minimizing the amount of foliage. Litterfall from the forest has resulted in a large accumulation of peat. Although some nutrient regeneration apparently occurs, these peat deposits contain large, permanent nutrient losses from the community. Nutrients cycling is dissolved form (e.g., foliar leachates) and nutrients received from atmospheric precipitation are likely to be of special importance to the nutrition of this closed—basin swamp forest community.
The Importance of Temporal Resolution in Food Web Analysis: Evidence from a Detritus‐Based Stream
Authors: Tavares-Cromar Annette F. , Williams D. Dudley
Published: April 2006

A series of time—specific food webs for the macroinvertebrate riffle community of Duffin Creek, Ontario was constructed using dietary information obtained from the analysis of gut contents. Trophic links were quantified using a dietary index of relative importance. Precision of the analysis was maintained at a high level by: (1) identifying dietary items as accurately as possible via direct gut analysis; (2) identifying web members to the species level, thus avoiding the taxonomic aggregation and lumping of size classes common in food web analyses; and (3) ensuring temporal resolution of the web by determining ontogenic variation in the diets of dominant members of the community. The Duffin Creek webs are heavily detritus—based with a large proportion of top—to—basal, and intermediate—to—basal links. Top—to—basal links, proportions of top and intermediate species, and lower connectance (0.180—0.219) varied temporally. Trophic connectance ranged from 0.090 to 0.109, consistent with values expected for a web consisting largely of specialist feeders. Weak links made up the largest proportion of total links in the webs, whereas very strong links made up the smallest proportion. Omnivory was more common than indicated in other webs and can be attributed to ontogenic diet switching. Comparison of the statistics for a summary web with those generated for the time—specific webs indicated that the total number of links per web, total number of species, number of top and intermediate species, and linkage density were much greater for the summary web. In view of these differences, the importance of temporal resolution when assessing food web structure and dynamics is emphasized. The possibility that some of the observed features in our web are common to other detritus—based webs is considered. Future studies of this calibre are justified.
Mortality Rates of 205 Neotropical Tree and Shrub Species and the Impact of a Severe Drought
Authors: Condit Richard , Hubbell Stephen P. , Foster Robin B.
Published: April 2006

Mortality rates of 205 tree and shrub species were estimated during two intervals, 1982—1985 and 1985—1990, in two size classes, 1—10 and ≥ 10 cm in diameter, in a 50—ha census plot in tropical moist forest on Barro Colorado Island in Panama. The severe dry season of 1983 was the focus of the study, since prior observations had demonstrated that it caused mortality in the forest. Here we document that forest—wide mortality was ≈ 3%/yr during the drought interval but only 2%/yr during the period afterwards, and that excess mortality during the first interval amounted to 2% of stems in the larger size class and 1% in the smaller. Overall, just under 70% of all species had higher mortality during the first census interval, but not all species were equally affected. Canopy trees had significantly higher mean mortality rates during 1982—1985 than during 1985—1990, but treelets and shrubs showed no or slight differences. This was counter to our prediction that species with short root systems would suffer more from a long drought. Shrubs did, however, have higher mortality rates than trees and treelets during both census intervals. We also evaluated mortality rates for subgroups of species that specialized on different microhabitats in the forest. As we predicted, colonist species (those associated with light gaps) had higher mortality rates than generalist species, 7—10%/yr compared to 2—4%/yr, but only in the smaller size class. Unexpectedly, colonizers had similar mortality rates as non—colonizers in the larger size class. Gap colonizers and generalist species were similarly affected by the drought–both had elevated mortality during 1982—1985. Species whose distributions were associated with moister soils (on the slopes around the island's plateau or in a swamp in the midst of the 50—ha plot) also had elevated mortality during the drought period, but no more so than generalist species. This was counter to our prediction that species from moist microhabitats would suffer more during an extended drought than generalists. Understory treelets that were slope specialists had higher mortality than generalists during both census intervals, but not large trees that were slope specialists. Our conclusions emphasize diversity as well as pattern. Every trend we illustrated had well—documented exceptions: large trees with lower mortality during the drought period, for example. Clearly, accurate predictions about how tropical forests will respond to climatic perturbations will require much detailed information from many species.
Factors Governing Habitat Selection by Prothonotary Warblers: Field Tests of the Fretwell‐Lucas Models
Authors: Petit Lisa J. , Petit Daniel R.
Published: April 2006

The ecological and evolutionary ramifications of habitat selection for the population dynamics of Prothonotary Warblers (Protonotaria citrea) were examined by evaluating specific factors affecting choice of habitat by the warblers, and testing the predictions of habitat selection theories proposed by Fretwell and Lucas (1970). Seven study plots were established along the Tennessee River in west—central Tennessee between 1987 and 1989. Each plot consisted of 80 nest boxes in a 20 column $\times$ 4 row grid, with one row placed along shoreline over standing water (flooded habitat), and three parallel rows placed inland at 35—m intervals (dry habitat). Flooded and dry habitats differed in vegetative structure and species composition, and flooded habitat contained more natural nest sites, higher arthropod abundances, and fewer species competing for nest sites than did dry habitats. Warblers settled preferentially in flooded habitat, where breeding density was higher than in dry habitat. When predation effects were excluded, birds in flooded habitat fledged more young per nest and made more nesting attempts than did birds in dry areas. With predation included, no significant differences in breeding success in the two habitats were found. Distribution of breeding warblers across wet and dry habitats followed the “ideal dominance” model of Fretwell and Lucas (1970), with older and larger males excluding younger and smaller ones from flooded areas. Territoriality in Prothonotary Warblers apparently serves to limit breeding density and to maximize breeding success within preferred habitat.
Actor Training in the Neutral Mask
Authors: Eldredge Sears A. , Huston Hollis W.
Published: April 2006

During the first World War, in Paris Jacques Copeau developed the idea of a severe and simple form of theatre, neither classical nor topical, but versatile through the economy of its means. In 1919 he remodelled the stage of the Vieux-Columbier in accordance with his new ideas, and over the next two years he founded a school for the training of actors, the École du Vieux Columbier. Both in design and in acting, Copeau wanted to make large statements with simple gestures. The pursuit of simplicity made him eliminate distractions, to create the still ground against which a movement or a form could be seen. His bare architectural stage was meant to magnify the evanescent statements of the drama. “I want the stage to be naked and neutral,” he wrote, “in order that every delicacy may appear there, in order that every fault may stand out; in order that the dramatic work may have a chance in this neutral atmosphere to fashion that individual garment which it knows how to put on.”
Hierarchical characterization of aggregates for Monte Carlo simulations
Authors: Briesen Heiko
Published: April 2006

Modeling of crystallization processes is usually based on deterministic population balances. Although conceptually there is no such limitation, population balance modeling is used only up to a few internal dimensions because of the computational effort. Alternatively, Monte Carlo methods are increasingly used for the simulation of particulate systems. There, the characterization of particles is also often limited to a few size and shape parameters similar to those of deterministic population balance modeling. A major advantage of Monte Carlo methods, however, is its simple extensibility to more complex particle characterizations. However, actually considering the full three‐dimensional shape of a complex agglomerate may lead to a prohibitive computational effort. To overcome this bottleneck a hierarchical particle characterization is proposed. This characterization allows the realistic representation of the agglomerates, without the need for detailed geometric computations for each particle. Instead of the full geometry, substitution systems are introduced that can be used to perform aggregation events or to identify crystal faces that are available for growth. The substitution systems consist of point mass systems, which preserve certain characteristics of the original agglomerate such as the moment of inertia. Numerical studies show the applicability of the approach. Based on this characterization, modeling of rate processes can be performed on a much higher level of detail than is allowed by standard one‐ or two‐dimensional particle characterizations. © 2006 American Institute of Chemical Engineers AIChE J, 2006
Asymmetric aziridination of 1,3‐dienes catalyzed by bisoxazoline‐copper complexes
Authors: Ma Linge , Du Da‐Ming , Xu Jiaxi
Published: April 2006

The asymmetric aziridination of 1,3‐dienes catalyzed by bisoxazoline‐CuOTf complexes with PhINTs as a nitrene precursor has been achieved in moderate yields with up to >99:1 regioselectivity, up to >99% diastereoselectivity, and up to 80% enantioselectivity. α,β,γ,δ‐Unsaturated ketones usually produced cis‐γ,δ‐aziridinated products, while 1,4‐diphenyl‐1,3‐butadiene afforded both of cis‐ and trans‐aziridine derivatives as major products by the use of different bisoxazoline ligands. The configuration of cis‐aziridine derivatives was proposed on the basis of the reaction mechanism. Chirality, 2006. © 2006 Wiley‐Liss, Inc.
Regularly methylated novel pro‐apoptotic genes associated with recurrence in transitional cell carcinoma of the bladder
Authors: Christoph Frank , Weikert Steffen , Kempkensteffen Carsten , Krause Hans , Schostak Martin , Miller Kurt , Schrader Mark
Published: April 2006

Epigenetic silencing of tumor suppressor genes by promoter hypermethylation has been shown for a variety of genes in bladder cancer. Various p53 target genes have been investigated, but only few demonstrated promoter hypermethylation when semiquantitative detection methods were applied. To address to the question whether promoter methylation of novel p53 effector genes is a common event in transitional cell carcinoma of the bladder, we selected the p53 target genes apoptotic protein‐activating factor (APAF‐1), Caspase 8 (CASP‐8), death‐associated protein kinase, (DAPK‐1) and insulin‐like growth‐factor‐binding protein‐3 (IGFBP‐3), performing quantitative methylation‐specific real‐time PCR. The individual level of methylation (normalized index of methylation) was correlated with clinicopathological features as well as the biological behavior of the superficial and muscleinvasive tumors. Tissue was obtained from 110 tumor patients and 20 patients without urological malignancy. The median follow‐up of the tumor patients was 52 months. Hypermethylation of the promoter region in tumor specimens was common for APAF‐1 (100%), DAPK‐1 (74%) and IGFBP‐3 (66%), but not for CASP‐8 (3.6%). It was seen less frequently and with undetectable or low methylation levels in the normal urothelium group. The APAF‐1 methylation levels significantly correlated with tumor stage and tumor grade. The APAF‐1 and IGFBP‐3 methylation levels were able to separate tumors with higher recurrence risk from low‐risk tumors in nonmuscleinvasive and muscleinvasive tumors. In multivariate analysis, APAF‐1 and IGFBP‐3 methylation levels were independent prognostic markers for recurrence in superficial bladder tumors. This study provides new insights into the role of promoter methylation of selected p53 target genes. The extent of promoter methylation of specific genes offers additional prognostical information and is associated with the outcome in patients with nonmuscleinvasive and muscleinvasive bladder cancer. © 2006 Wiley‐Liss, Inc.
Foreign exchange intervention and the Australian dollar: has it mattered?
Authors: Edison Hali , Cashin Paul , Liang Hong
Published: April 2006

Since the Australian dollar was floated in December 1983, the Australian central bank (Reserve Bank of Australia) has actively intervened in the foreign exchange market. Using daily exchange rate and official intervention data from January 1984 to December 2001, this paper examines what effects, if any, foreign exchange operations by the Reserve Bank of Australia (RBA) have had on the level and volatility of the Australian dollar exchange rate. First, using an event study we evaluate the effectiveness of intervention by examining its direct effect on the level of the exchange rate. We find that over the period 1997–2001, the RBA has had some success in its intervention operations, by moderating the depreciating tendency of the Australian dollar. Second, we investigate the effects of RBA intervention policies on exchange rate volatility over the floating rate period. Our results indicate that intervention operations tend to be associated with an increase in exchange rate volatility, which suggests that official intervention may have added to market uncertainty. Overall, the effects of RBA intervention are quite modest on both the level and the volatility of the Australian dollar exchange rate. Copyright © 2006 John Wiley & Sons, Ltd.
Using doctoral education to prepare faculty to work within Boyer's four domains of scholarship
Authors: Austin Ann E. , McDaniels Melissa
Published: April 2006

This chapter focuses on the role of graduate education in preparing future faculty members for engagement not only in the domain of discovery but also in the scholarships of application, integration, and teaching.
Insulin‐like growth factor‐I increases bone sialoprotein (BSP) expression through fibroblast growth factor‐2 response element and homeodomain protein‐binding site in the proximal promoter of the BSP gene
Authors: Nakayama Youhei , Nakajima Yu , Kato Naoko , Takai Hideki , Kim Dong‐Soon , Arai Masato , Mezawa Masaru , Araki Shouta , Sodek Jaro , Ogata Yorimasa
Published: April 2006

Insulin‐like growth factor‐I (IGF‐I) promotes bone formation by stimulating proliferation and differentiation of osteoblasts. Bone sialoprotein (BSP), is thought to function in the initial mineralization of bone, is selectively expressed by differentiated osteoblast. To determine the molecular mechanism of IGF‐I regulation of osteogenesis, we analyzed the effects of IGF‐I on the expression of BSP in osteoblast‐like Saos2 and in rat stromal bone marrow (RBMC‐D8) cells. IGF‐I (50 ng/ml) increased BSP mRNA levels at 12 h in Saos2 cells. In RBMC‐D8 cells, IGF‐I increased BSP mRNA levels at 3 h. From transient transfection assays, a twofold increase in transcription by IGF‐I was observed at 12 h in pLUC3 construct that included the promoter sequence from −116 to +60. Effect of IGF‐I was abrogated by 2‐bp mutations in either the FGF2 response element (FRE) or homeodomain protein‐binding site (HOX). Gel shift analyses showed that IGF‐I increased binding of nuclear proteins to the FRE and HOX elements. Notably, the HOX‐protein complex was supershifted by Smad1 antibody, while the FRE‐protein complex was shifted by Smad1 and Cbfa1 antibodies. Dlx2 and Dlx5 antibodies disrupted the formation of the FRE‐ and HOX‐protein complexes. The IGF‐I effects on the formation of FRE‐protein complexes were abolished by tyrosine kinase inhibitor herbimycin A (HA), PI3‐kinase/Akt inhibitor LY249002, and MAP kinase kinase inhibitor U0126, while IGF‐I effects on HOX‐protein complexes were abolished by HA and LY249002. These studies demonstrate that IGF‐I stimulates BSP transcription by targeting the FRE and HOX elements in the proximal promoter of BSP gene. J. Cell. Physiol. 208: 326–335, 2006. © 2006 Wiley‐Liss, Inc.
Date consumption and dietary significance in the United Arab Emirates
Authors: Ismail Baraem , Henry Jeya , Haffar Imad , Baalbaki Riad
Published: April 2006

Date consumption in the United Arab Emirates was determined among different subgroups of the nation's society. Adult consumers of both sexes and different age groups (18–30 and 30–60) and occupations (students, workers, at home) were surveyed for information on their daily consumption of six date food groups (rutab, tamr, seh, debbs, batheeth and madlouj). Percentage distribution of portion size, frequency of consumption and season, over different consumer groups per date food group, were determined. Differences in the daily consumption of every date food group within and among the different population groups were tested. The most consumed date food groups were rutab and tamr, with rutab being more frequently consumed than tamr during the summer season. Overall, no major differences were observed in average daily consumption per capita of most of the date food groups between males and females, between employed and home‐based consumers, and between students and individuals of 18–30 years old. On average, daily consumption of dates per capita was 114.3 g, equivalent to 10 date fruits. However, it was noted that the younger population does not consume dates as much as the older population does. Nevertheless, data obtained highlighted the significance of dates in the UAE nation's diet considering the relatively high average consumption of dates per capita. Copyright © 2006 Society of Chemical Industry
Seligman lecture 2005 food product engineering: building the right structures
Authors: Aguilera José Miguel
Published: April 2006

Driven by consumers' expectations and new knowledge, a paradigmatic shift is occurring in food engineering from the prior emphasis in processes and unit operations to the design of products that provide convenience, health and well‐being. The structure of foods affects their sensorial, physical and transport properties as well as the bioavailability of some nutrients. Food structure is provided by nature or imparted during processing and preparation. Presently, food product engineering is stabilizing, transforming and creating edible microstructures that are desired by consumers using conventional unit operations. This paper revises the progress in the science of food materials and its contribution to the understanding of how food structures are formed from the molecular to the macromolecular level. Food product design of the future will be based on a wider scientific knowledge adopted from many disciplines and advanced tools that reduce the scale of fabrication. This poses a challenge to food engineering education. Copyright © 2006 Society of Chemical Industry
Brain 1H magnetic resonance spectroscopic differences in myotonic dystrophy type 2 and type 1
Authors: Vielhaber Stefan , Jakubiczka Sibylle , Gaul Charly , Schoenfeld Mircea Ariel , Debska‐Vielhaber Grazyna , Zierz Stefan , Heinze Hans‐Jochen , Niessen Heiko G. , Kaufmann Jörn
Published: April 2006

To evaluate cerebral metabolism and intergroup differences in closely matched patients with myotonic dystrophy type 2 (DM2, n = 15) and type 1 (DM1, n = 14), we performed 1H magnetic resonance spectroscopic (MRS) analyses of the occipital and temporoparietal cortical regions as well as of subcortical frontal white matter. Relative to healthy subjects, the concentration of N‐acetylaspartate was significantly reduced in all tested brain regions in both disease groups. In the DM1 patients we also observed a concomitant depletion of creatine and choline levels, particularly in the frontal white matter. A discriminant analysis based on the 1H‐MRS data distinguished between the DM2, DM1, and control groups with an overall accuracy of 88%. 1H‐MRS indicates that neurochemical alterations involving gray and white matter occur in patients with DM2 and DM1. Although structural abnormalities (cerebral atrophy, white matter lesions) are similar in DM2 and DM1, changes in cerebral metabolites can differentiate these disease groups, suggesting that the diseases differ in their neurocellular pathology. Muscle Nerve, 2006