bluuebunny/crossref_metadata_2025 huggingface dataset:
The Mystery Plays of Michael Kirby
Authors: Carroll Noel
Published: April 2006

As a sculptor, photographer, playwright and director, Michael Kirby has been and is still an articulate proponent of the interanimation of the arts. As a practitioner as well as a theoretician of several arts, he has made and defended work that not only mixes media but also transposes forms and preoccupations of one art to others. Kirby’s commitment to the lively cross-fertilization of the arts partially accounts for the rise of Structuralist Theatre since that movement, in certain respects, appears to have been influenced in important ways by the tendency of Minimalist Art referred to as systemic painting.

Some of Kirb’s Structuralist plays, like Revolutionary Dance and Identity Control, are composed of a series of dramatic, narrative vignettes that have no apparent causal or chronological relation. Kirby created his dramatic incidents as a painter might choose a color or shape, i.e., with an eye to its place in the overall formal structure.
Vakhtangov's The Dybbuk
Authors: Fishman Pearl
Published: April 2006

Habimah, Israel's National Theatre, was born in the midst of the great upheaval of the Russian Revolution. In 1917, under the inspiring leadership of Nachum Zemach, the first group of 12 actors began training for the attainment of their goal—the establishment of a professional repertory theatre group to perform in Hebrew. They formed their theatre as a collective officially called “The Mutual Society, Ltd.” in which all had equal privileges and obligations. It was their hope that this dramatic group would be part of the process of national rebirth in Palestine.

From 1918 until 1924, at a time when Hebrew was considered a “counter revolutionary” language and Zionists were being arrested by the hundreds, Habimah's repertoire consisted of plays dealing with Jewish subjects, giving dramatic expression to the traditions and aspirations that nourished the Russian Zionist movement.
The Khan Theatre Company
Authors: Lerner Motti
Published: April 2006

The Khan Theatre Company was formed in 1972 in Jerusalem by Michael Alfreds, an English Jewish theatre director and teacher. Alfreds has worked in Israel since 1968 staging several successful plays such as The Mandrake by Machiavelli and The Donkeys by Plautus in the Haifa Municipal Theatre. Despite his success he still had difficulty working in the more well established theatres. Therefore, he accepted an invitation from the Jerusalem Municipality and formed a group of six young actors who were tired of seeking a comfortable milieu. They moved to Jerusalem and found their home in a renovated ruined Turkish inn—a 750-year-old khan. With government and municipal aid they formed the Khan Theatre Company to be the only repertory theatre in Jerusalem.
Dry Matter Production in Young Loblolly (Pinus Taeda L.) and Slash Pine (Pinus Elliottii Engelm.) Plantations
Authors: Nemeth John Charles
Published: April 2006

The net primary productivity of the pine species and lesser vegetation (herbaceous ground cover) plus turnover rates between the litter layer and soil organic matter were investigated in young loblolly and slash pine plantations in Beaufort County, North Carolina. Estimations of the aboveground tree biomass and production by components were made by applying multiple regression, weight—prediction equations developed from harvest data (15 slash pine and 41 loblolly pine trees) to tree dimensions from 28 permanent, undisturbed plots. Optimal plot size was determined by time—cost analysis. Total biomass for slash pine ranged from 5.2 mt/ha and 9.9 kg/tree (age 4) to 31.7 mt/ha and 29.8 kg/tree (age 8), and loblolly pine ranged from 4.2 mt/ha and 4.7 kg/tree (age 4) to 107.6 mt/ha and 82.7/tree (age 12). Net production for slash pine was greater than loblolly pine and ranged from 3.9 mt/ha per year and 8.0 kg/tree per year (age 4) to 12.3 mt/ha per year and 11.6 kg/tree per year (age 8). Loblolly pine produced from 4.3 mt/ha per year and 4.8 kg/tree per year (age 4) to 4.1 mt/ha per year and 4.3 mt/ha per year (age 8). Net primary production of loblolly pine was 22.3 mt/ha per year and 18.8 kg/tree per year at age 10 and 11 and dropped to 18.4 mt/ha per year and 13.6 kg/tree per year at age 12. The decrease in production rate of loblolly pine at age 12 was correlated with a decrease in branch needle biomass as canopy closure progressed. Five root systems were excavated, and percentage of aboveground tree biomass was used to calculate root biomass and production. Canopy closure also caused a decrease in net primary production of the lesser vegetation from 1.8 mt/ha per year in the open stands to 0.2 mt/ha per year under closed stands. Simultaneously, the ground—litter component increased from 3.7 to 5.8 mt/ha through litter fall, and the turnover rate to the soil decreased. Soil organic matter accounted for 88% (102.0 mt/ha) to 52% (124.0 mt/ha) of total plot biomass in the youngest and oldest stands, respectively. Caloric analysis was done on all plant material and ground litter. The results are presented as net primary production and turnover rates (109 cal/ha per year).
History of an African Rift Lake and Its Climatic Implications
Authors: Richardson J. L. , Richardson A. E.
Published: April 2006

Analysis of a 28—m core from a relict fresh—water lake in Kenya had provided a detailed limnologic and climatic history covering 9,200 years. The core is an incomplete section through the sediments of a submerged crater near the eastern shore of Lake Naivasha. The overall sedimentation rate, 0.33 cm wet sediment per year, is the most rapid on record for a lake whose sediments are essentially autochthonous and organic. A three—stage limnologic history is inferred from the microfossils (particularly diatoms), chemistry, and mineralogy of the core: (A) From before 9,200 B.P. until about 5,650 B.P. a lake significantly larger than the present one existed in the basin. Algal productivity was high, and the water temperature was probably above the present average. The surface waters of this lake were evidently depleted in silica, suggesting some stratification, but the total ion content was not far below today's (B) Between 5,650 B.P. and 3,040 B.P. the lake shrank, aquatic macrophytes increased in abundance near the core site, and the water grew more dilute. The crater became isolated from the main lake and finally dried briefly. (C) For the past 3,000 years a small lake has existed in the basin. It has been frequently smaller and its water sometimes much more concentrated than that of the modern lake. The lake discharged through a southern outlet prior to 5,650 B.P., but since that time has had no surface outlet. Various freshening mechanisms have operated during the past 5,000 years, probably including deflation, burial of alkaline layers, underground seepage, and perhaps ion removal by aquatic plants. The climate during the period of the large lake (Leakey's Gamblian Pluvial period) was much wetter and probably warmer than today, and rainfall at Naivasha was more seasonal. Rainfall was perhaps 65% above the modern average. We find no convincing evidence for an early post—Gamblian wet phase, the Makalian, proposed by earlier workers for this region. A later wet phase, the Nakuran, may be represented by the small, fluctuating lake of the past 3,000 years, but this lake probably never stood as high as the strandline previously assigned to the Nakuran. The climatic inferences from this study are in substantial agreement, but provide interesting points of contrast, with those from other recent investigations in sub—Saharan Africa.
Population Persistence and Density Dependence
Authors: Royama T.
Published: April 2006

This paper reformulates the notion of density dependence and shows how this notion plays an important role in constructing appropriate models for data analysis. The regulation and persistence of population processes are interpreted as a close resemblance to the behavior of a series of random variables in which the second moments are bounded. On this basis the formal criteria of persistence are deduced. General structural models of population processes are set up and translated into discrete single—variable difference equations, ranging from the simplest linear first—order process to more complex nonlinear second—order processes. The discussion includes the derivation of general conditions for the second—order limit cycles, a reanalysis of the Canadian lynx 10—yr cycle, and models for population outbreaks. Based on the results of the preceding study of models, the notion of density dependence is reformulated. First, the meaning of the word 'dependence' is discussed. In the context of 'density dependence,' the word has two meanings; the causal dependence of a factor on density, and the statistical dependence. Statistical dependence is defined as a converse of statistical independence, the latter being a process in which the rate of change in density has zero correlation with density; this is a very special class of processes and is unlikely to occur in natural population processes. Therefore, the test of density dependence against the null hypothesis of statistical independence will not provide much insight. It is also argued that a deduction from the persistence criteria shows that a negative correlation between density and its rate of change is a necessary outcome of regulation and hence that the notion of 'density—dependent regulation' in statistical dependence is an uninspiring tautology. As opposed to statistical density independence, which necessarily generates an unbounded population process, causal density independence may satisfy the persistence conditions and hence may regulate populations. However, such a causally 'density—independent regulation' tends to be 'fragile' against perturbations by random exogenous factors. It is a particular class of causally density—dependent processes that can ensure regulation more durable against such perturbations. The inference of generating mechanism from observation is discussed. Although regression analysis is an essential method of inference, simple regression analysis will not work unless the observed processes are known to be a simple Markov chain. Statistical inference of generating mechanisms in observed systems depends largely on the choice of appropriate models, and it is in the construction of such models that the notion of causal density dependence plays an important role.
Tissue Water Potential, Photosynthesis, C‐Labeled Photosynthate Utilization, and Growth in the Desert Shrub Larrea divaricata Cav.
Authors: Oechel W. C. , Strain B. R. , Odening W. R.
Published: April 2006

Tissue water potential is the most important factor throughout the seasons controlling phenological events, photosynthesis, and productivity of Larrea divaricata growing in Deep Canyon near Palm Desert, California. Growth of reproductive structures was initiated at the time of highest tissue water potential and ceased as water potential decreased. Percentage foliation correlated strongly with dawn water potential (r = 0.89). The elongation rate of stems and the rate of node production were both dependent on tissue water potential. Leaf growth and node growth proceeded at varying rates throughout the year, providing a continuous sink for photosynthates. Photosynthesis rates ranged from 9.02 mg CO2 incorporated per day per gram dry weight of leaf tissue in September to an estimated 74.7 mg CO2 in early February. Net photosynthesis and relative productivity correlated very strongly with dawn water potential (r = 0.93 and r = 0.97, respectively). Larrea plants were labeled at 1— to 2—month intervals with photosynthetically incorporated 14CO2to determine the utilization in growth and storage of photosynthate fractions produced at various times throughout the year. Tissue was subsampled at similar intervals, and the activity in various metabolic compounds (sugar, starch, lipid, organic acid, amino acid, protein, cellulose, and cell—wall materials) was analyzed. The utilization of photosynthates in the various fractions was similar in all seasons. No appreciable mobilization into and out of storage materials was apparent. Never dormant, Larrea remains metabolically active and forms new tissue throughout the year. This growth pattern may be an important adaptation allowing Larrea to exist in a wide range of geographical and climatic areas, and, perhaps owing to the species' tropical affinities, it might have been a preadaptation to the desert environment.
Subalpine Coniferous Forests of Central Honshu, Japan
Authors: Franklin Jerry F. , Maeda T. , Ohsumi Y. , Matsui M. , Yagi H. , Hawk Glenn M.
Published: April 2006

Mature subalpine forest communities were sampled at four locations in central Honshu, Japan–Mounts Fuji and Ontake and Yatsugatake and Chichibu Mountains. Data were subjected to similarity—ordination and association analyses. There are three major groups of communities: Tsuga diversifolia/moss, Abies spp./herb, and conifer/Sasa. Tsuga/moss forest understories are depauperate in vascular plants or dominated by ericads such as Rhododendron and Menziesia and have very stony soils. Abies/herb forests have luxuriant understories in which herbs and ferns are conspicuous; they occur over a wide range of soil conditions. Conifer/Sasa forests have extremely dense layers of dwarf bamboo (Sasa spp.) 1—1.5 m in height and occur on deep, fine—textured volcanic—as soils. Composition and structure of 11 community types and phases belonging to these groups are described. Successional trends appear to favor the more shade—tolerant Abies mariesii and Abies vetichii over Tsuga diversifolia and Picea jezoensis var. hondoensis although this varies with site. Japanese forests have many similarities with those in the eastern United States, but the dwarf bamboo communities are strictly an Asian phenomenon.
Multiple Regulation States in Populations of the California Vole, Microtus Californicus
Authors: Hestbeck Jay B.
Published: April 2006

Two experiments were designed to test which hypothesis of population regulation provided the most consistent explanation of population fluctuations in the California vole. The first experiment tested the effects of spacing behavior and of initial breeding—season density on population regulation. The second experiment tested the effects of resource level, of population history, and of population substructure. A factorial design was used for each experiment. The first experiment was analyzed as two separate factors. The second experiment was analyzed with a 2 × 2 × 2 factorial analysis of variance. The results indicate that naturally occurring populations appear to be regulated by two separate but equally important mechanisms. When habitat occupation is patchy, spacing behavior dominates and densities are regulated below 200 individuals/ha. Individuals from these populations can be characterized as coming from low or early—increase phases. Survival is low due to very high dispersal losses and a moderate mortality rate. Individuals have a greater tendency to be reproductive. Males have lower masses. When habitat occupancy is more uniform, increasing overall density reduces the dispersal rate and, as a result, densities increase further. In this situation, resource limitation dominates the regulation process. Peak densities of these populations range from 500 to 800 individuals/ha. Individuals from these populations can be characterized as coming from the peak phase. Survival is high due to low dispersal losses and a moderate mortality rate. Individuals tend less to be reproductive, and males are heavier.
Constraints and Competition in the Evolution of Flowering Phenology
Authors: Kochmer John P. , Handel Steven N.
Published: April 2006

We tested whether the flowering times of animal—pollinated plants are influenced by phylogenetic membership and by life form (e.g., annual, perennial, etc.). We analyzed existing data sets on 2298 animal—pollinated angiosperms of North and South Carolina and 1575 animal—pollinated angiosperms of temperate Japan, and also analyzed a null model based upon the Carolina flora. Our analyses of the complete data sets and of subsets including only the largest families showed that: (1) the floras of the Carolinas and temperate Japan have bimodal distributions of flowering times, with peaks in spring and late summer; (2) within each of these floras, families differ very significantly in flowering time; (3) for most families, flowering times in the Carolinas and in Japan are statistically indistinguishable; (4) the sequences of flowering, ordered by family, are also statistically indistinguishable in the two floras; (5) within each flora, skewness of flowering time differs markedly among families; (6) for a typical family, the skewness of flowering time is the same in the two floras; (7) there is a significant negative correlation between skewness and mean family flowering time; and (8) life forms differ in flowering time, though less markedly than families. These results demonstrate that phylogenetic membership and life form strongly influence a species' flowering time. We argue that seasonal limitations of flowering times are caused by phylogenetic constraints, which may not have changed for millions of years. This study does not provide the degree of resolution needed to determine whether or not there is natural selection for alteration of flowering times in these floras, whether by competition or other mechanisms. However, our results do suggest that competition for pollination does not push species' flowering times beyond seasonal boundaries imposed by phylogenetic constraints. The effects of competition on flowering time are probably limited to small and temporary readjustments of the phenological relationships of competitors. Studies of the flowering times of animal—pollinated plants must consider the strong limits to seasonal displacement imposed by phylogeny and life form, and the probable existence of many alternative modes of escape from competition besides seasonal shifts. We consider the implications of recent paleobotanical studies that suggest that temperate plant communities may not have been sufficiently stable through time for plants to have achieved competitive equilibria. Phylogenetic and life history constraints are likely to influence the evolution of many community characters besides flowering time. The methods we have used and the conclusions we have drawn are relevant to a wide variety of ecological characters in plants and animals.
Spatial and Temporal Variation in Settlement and Recruitment of Intertidal Barnacles
Authors: Caffey Hugh M.
Published: April 2006

I examined the spatial and temporal partitioning of variation in settlement and early survival of an intertidal barnacle, Tesseropora rosea. Monthly, for 3 yr, I monitored the density of newly settled barnacles (<30 d old) and new recruits (30—60 d old) on each of three spatial scales referred to as: within sites (i.e., replicate areas within 3 m2), among sites within shores (i.e., six sites arrayed horizontally in the mid—intertidal region, with 20—50 m between adjacent sites), and among shores (seven headlands along the New South Wales coast with 11—555 km between them). Sites and shores were initially chosen to be as similar as possible with respect to height in the intertidal region, density of adult Tesseropora, and wave exposure. All observed variation was, therefore, within—habitat variation and not readily related to any of the factors already known to affect the density of settlers or their subsequent survival, such as exposure or intertidal level. There was significant variation in the densities of settlers and recruits on all spatial scales at any given time. Variation among months and among years was also great at any given spatial scale. There were no simple, consistent trends, however, in the variation within any spatial or temporal scale, i.e., variation at any spatial scale interacted strongly with that for any temporal scale. The shores ° years interaction (the interaction of large—scale spatial with large—scale temporal variation) produced dominant year—classes on some shores in some years and on other shores in other years. Proportional survival of new settlers also varied significantly on all spatial and temporal scales monitored. Thus, much residual patchiness exists in the spatial and temporal distributions of barnacles <60 d old. Previous authors investigating the structure and maintenance of rocky intertidal communities have played down the fact that settlement and recruitment of the component species vary greatly on different scales. Yet, such variation should be explicitly incorporated in the development of theory for marine populations and communities.
Feeding Preferences of Tegula Funebralis and Chemical Defenses of Marine Brown Algae
Authors: Steinberg Peter D.
Published: April 2006

I examined the effects of phenolic compounds in marine brown algae on the feeding behavior of the intertidal gastropod Tegula funebralis and other marine herbivores. The effects of algal nitrogen content and thallus toughness were also investigated. T. funebralis showed consistent feeding preferences in the laboratory and in the field in pairwise tests of 13 species of marine brown algae (Phaeophyta) from central California. Relative levels of phenolic compounds, which are known to deter feeding by herbivorous snails, differed greatly between preferred and nonpreferred species of algae. The total phenolic content of the six most preferred species of algae averaged 0.83% of dry mass; the phenolic content of the seven least preferred species averaged 4.53%. Differences in relative tanning ability were similarly large. Tannic acid, a terrestrial plant tanin, when experimentally added to one kelp species, deterred feeding by T. funebralis. These results and analyses of studies of additional species of brown algae also showed consistent differences in the phenolic content between species in the order Laminariales (typically low) and those in the order Fucales (uniformly high). Feeding preferences of other gastropod, echinoid, and crustacean algivores from the northeast Pacific Ocean are strikingly similar to those of T. funebralis; this supports the contention that high levels of phenolic compounds in brown algae are a generally effective feeding deterrent against many kinds of marine invertebrate herbivores. Organic nitrogen content of the algae was positively correlated with the feeding preferences of T. funebralis. However, this was most likely an indirect effect of the significant negative correlation between algal nitrogen and phenolic contents. Thallus toughness of the algae did not seem important in determining overall feeding preferences of Tegula, but may have affected choices between algae that were low in phenolics. I suggest that feeding preferences of Tegula funebralis for brown algae are primarily due to avoidance of algal defenses; positive aspects of food quality (such as attractants or nutritional content) probably play a lesser role in determining preference.
Demographic Effects of Reproductive Resource Supplementation in a Territorial Frog, Dendrobates Pumilio
Authors: Donnelly Maureen A.
Published: April 2006

To determine whether tadpole—rearing sites (bromeliads) or oviposition substrates (leaf litter) were the objects of male defense in the position—dart frog Dendrobates pumilio, I experimentally increased the availability of these two resources in a complete two—factor factorial design for variance analysis and examined the demographic response of the frogs. I also examined the effects of resource addition on sex ratio and age—structure. Mark—recapture data were collected on experimental and control plots during the 7 mo of the treatment period, during which 4754 observations were made on 1208 marked individuals. I used a three—factor repeated measures analysis of variance to determine if resource addition affected density. The addition of oviposition substrate did not result in increased density, but the addition of bromeliads led to an increase in the density of adult males and females on treatment plots relative to the controls. To document which demographic variables were affected, animals were classified as immigrants, recruits, or survivors; all losses were assumed to be the result of emigration. The demographic variables were analyzed with three—factor repeated measures ANOVA. The increases in males resulted from increased survival on treatment plots, whereas the increase in females resulted from increased immigration, recruitment, and the accumulation of survivors. Sex ratio was not affected by resource supplementation but age—structure was; litter addition increased the proportion of juveniles on treatment plots. The population—level response suggests that bromeliad availability is limited and this resource is defended by males.
Dynamics of Canopy Structure and Light Interception in Pinus Elliottii Stands, North Florida
Authors: Gholz H. L. , Vogel S. A. , Cropper W. P. , McKelvey K. , Ewel K. C. , Teskey R. O. , Curran P. J.
Published: April 2006

In order to develop a model of the carbon cycle for mature slash pine (Pinus elliottii) stands in north Florida, we studied seasonal variation in leaf area index (LAI, allsided), aboveground biomass increment and litterfall, and light penetration through the forest canopy, over a 3—yr period. The primary approach to establishing monthly LAI included annual destructive analyses and monthly measurements of needle fall and elongation. Imagery from the Landsat Thematic Mapper (TM) and pattern of light penetration were also used in attempts to derive less ardouous estimates; the TM imagery was most promising. LAIs ranged from 3.0 to 6.5 on control plots over the 3 yr, with repeated fertilization increasing maximum LAI by >40%. Seasonal variation was high (40%), as was variation from year to year. An average of 31% of the incident photosynthetically active radiation (PAR) penetrated the canopies annually, ranging from 18 to 42% seasonally. Seasonal light penetration could not be described using a simple application of the Beer—Lambert law, perhaps due to the highly aggregated nature of the canopies. Models incorporating more information on canopy structure are necessary to predict light penetration through slash pine stands accurately. A model of needle litterfall was derived that could account for much of the seasonal and annual variation using stand basal area and climate conditions from the spring of the previous year; this model may be useful for developing climate—driven predictions of LAI. Efficiencies of use of incoming and intercepted PAR were low compared to other forest types. Low light interception and high nutrient—use efficiencies (demonstrated in earlier studies) are important adaptive characteristics of slash pine stands to these relatively warm and nutrient—poor sites.
Late Quaternary Vegetational History of Grays Lake, Idaho
Authors: Beiswenger Jane M.
Published: April 2006

Pollen contained in sediment cores, from Grays Lake, Idaho, indicate cold, dry conditions from ≈70 000 to 30 000 yr BP when an Artemisia steppe surrounded Grays Lake and extended into the nearby mountains. From ≈30 000 until 11 500 yr BP, somewhat moister conditions supported a conifer woodland. Pinus and other conifers grew in the foothills and among Artemisia on the open plains. Increases in Picea, Abies, and Artemisia signaled the onset of a cool transitional climate ≈11 500 yr BP. Juniperus and members of the Chenopodiaceae/Amaranthaceae and Compositae families all became more abundant as the climate became warmer and drier. Xeric conditions persisted from ≈10 000 to 7100 yr BP, reaching a maximum ≈8200 yr BP. Subsequently, the climate of the Grays Lake Basin has been cooler and moister, with increases in conifers and decreases in Juniperus and steppe plants.
Paleolimnology of a Cape Cod Kettle Pond: Diatoms and Reconstructed pH
Authors: Winkler Marjorie Green
Published: April 2006

Changes in pH over the past 12 000 yr in Duck Pond in the Cape Cod National Seashore were reconstructed using a diatom—pH transfer function. The reconstructed pH suggested that the pond has been acid for its entire history with a mean reconstructed pH of 5.3 ± 0.3 (standard error of the predictive equation ± 0.5). There was a brief period during the late—glacial (at ≈11 500 BP) of higher pH of ≈6, possibly caused by increased windiness and erosion (inferred from concurrent pollen and sediment changes indicative of an open spruce—Hudsonia parkland), increased leaching of cations from outwash sands of the drainage basin, and/or increased instability of the water levels during lake development. The reconstructed pH history indicates that Duck Pond has become more acid recently (with a mean pH of 5.1 ± 0.1 for the past 150 yr) although the pH has varied both up and down throughout the Holocene with acidity as low as the present at other times in the past 12 000 yr. The significance of these changes in reconstructed pH is problematic because the pH variations lower in the core remain within the standard error of the equation and primarily reflect a long—term naturally acid ecosystem. This finding illustrates the need for more local and regional long—term lake pH histories so that naturally acid lakes can be distinguished from anthropogenically degraded lakes and ecologically sound management decisions can be made. In the pre—European—settlement levels of the core, correlations between charcoal and alkaline Fragilaria diatoms suggest that forest fires in the drainage basin may have affected pond pH. Correlations between charcoal and acid diatoms in post—European—settlement sediments suggest an effect on pond pH from recent increase in windborne industrial acids. Negative correlation between diploxyon Pinus species and the reconstructed pH and positive correlation between haploxylon Pinus and the alkaliphilic diatoms suggest that vegetation changes, which also reflect the climate and fire history of the region, have also affected pH of the pond.
Vegetation, Soil, and Climate on the Green Mountains of Vermont
Authors: Siccama Thomas G.
Published: April 2006

The Appalachian extension of the Boreal Forest, dominated by balsam fir, red spruce, and white birch, extends down the slope of the Green Mountains to about 2,600 ft (792 m), where it merges with the Eastern Deciduous Forest dominated by sugar maple, beech, and yellow birch. These two forest formations occur as well—developed horizontal bands on the mountains, with a distinctive tension zone forest between them. In this midslope forest the species of neither the deciduous nor boreal forest are able to form well—developed long—lived stands. The contact between the deciduous and boreal forest is climatically, not edaphically, controlled. The current vegetation and soil development is the result of the long—term effects of a vertical climatic discontinuity expressed as a nonlinear decline in the length of the frost—free period across the midslope transitional forest and as a marked increase in the frequency of the cloud base at and above ca. 792 m. This results is increased moisture from fog drip and frequent occurrence of hoar frost in winter. The sharp decrease in the length of the growing season, together with marked changes in icing and atmospheric moisture conditions, limits the upward extension of the beech—maple forest.
Density Dependence in Time Series Observations of Natural Populations: Estimation and Testing
Authors: Dennis Brian , Taper Mark L.
Published: April 2006

We report on a new statistical test for detecting density dependence in univariate time series observations of population abundances. The test is a likelihood ratio test based on a discrete time stochastic logistic model. The null hypothesis is that the population is undergoing stochastic exponential growth, stochastic exponential decline, or random walk. The distribution of the test statistic under both the null and alternate hypotheses is obtained through parametric bootstrapping. We document the power of the test with extensive simulations and show how some previous tests in the literature for density dependence suffer from either excessive Type I or excessive Type II error. The new test appears robust against sampling or measurement error in the observations. In fact, under certain types of error the power of the new test is actually increased. Example analyses of elk (Cervus elaphus) and grizzly bear (Ursus arctos horribilis) data sets are provided. The model implies that density—dependent populations do not have a point equilibrium, but rather reach a stochastic equilibrium (stationary distribution of population abundance). The model and associated statistical methods have potentially important applications in conservation biology.
Disturbance, Succession, and Maintenance of Species Diversity in an East Texas Forest
Authors: Glitzenstein Jeff S. , Harcombe Paul A. , Streng Donna R.
Published: April 2006

Vegetation change following selective logging and major natural disturbance was investigated through the use of stand history reconstruction and population monitoring in an east Texas pine—hardwood forest. High frequencies of release in beech (Fagus grandifolia) and white oak (Quercus alba) occurred after apparently natural disturbances in 1800—1810, 1860—1870, and 1960—1970, and after selective logging beginning ≈1910. Pulses of recruitment occurred after all disturbances except the most recent one. Age data suggest that recruitment after the 1910 disturbance was asynchronous among species, with loblolly pine (Pinus taeda) regenerating first, followed sequentially by white oak, red maple (Acer rubrum), and beech. At present, only magnolia (Magnolia grandiflora) is showing significant new recruitment. After the 1910 disturbance, regenerating pines grew rapidly and became dominant in the re—forming overstory. Most hardwoods originating after the 1910 disturbance did not reach the overstory. White oak initially outgrew maple and beech and is presently larger. Over the last 20 yr beech growth has been greater than white oak growth, resulting in a decline in the average size difference between individuals of these species. Presently, mortality rates of understory populations are high for sweetgum, blackgum, and the oaks, and are low for beech and magnolia. These latter two species are also the faster growing. If these trends continue, beech and magnolia will become increasingly predominant in the forest understory and eventually in the overstory as well. Map data show that saplings and small trees are abundant under pine and oak, but not under beech and magnolia. Future disturbance is therefore likely to accelerate succesion to more shade—tolerant species in parts of the forest now dominated by pine and oak, but is most likely to re—initiate new regeneration, including pine and oak, in areas now dominated by beech and magnolia. These results suggest a pattern of cyclical replacement driven by disturbance, a pattern which may help preserve species diversity in southern mesic forests.
Organic Carbon Flow in a Swamp‐Stream Ecosystem
Authors: Mulholland Patrick J.
Published: April 2006

An annual organic carbon budget is presented for an 8—km segment of Creeping Swamp, an undisturbed, third—order swamp—stream in the Coastal Plain of North Carolina, USA. Annual input of organic carbon (588 gC/m2) was 96% allochthonous and was dominated by leaf litter inputs (36%) and fluvial, dissolved organic carbon (DOC) inputs (31%). Although the swamp—stream was primarily heterotrophic, autochthonous organic carbon input, primarily from filamentous algae, was important during February and March when primary production/ecosystem respiration (P/R) ratios of the flooded portions were near one. Annual output of organic carbon via fluvial processes (214 gC/m2, 95% as DOC, was 36% of total annual inputs, indicating that the swamp—stream segment ecosystem was 64% efficient at retaining organic carbon. Respiration (327 gC/m2) accounted for most of this retention, or about 57% of annual inputs, and storage accounted for the remaining 7% of inputs. Organic carbon dynamics in the Creeping Swamp segment were compared to those reported for upland stream segments using indices of organic matter processing suggested by Fisher (1977) and a loading potential index suggested here. Creeping Swamp, while loading at a high rate, retains a much larger portion of its organic carbon inputs than two upland streams. Organic carbon loading potential in Creeping Swamp is very large, primarily because of its great width and complete canopy; however, its low gradient and dense vegetation enhance organic carbon retention, especially of coarse particulate organic carbon (COPC), by maintaining low water velocities with little erosive force, tortuous flow pathways, and debris dams. Most of the retention and oxidation of organic carbon in the flooded Creeping Swamp ecosystem takes place in the floodplain. It is suggested that floodplain exchanges should also be considered in budgets of higher gradient rivers and streams. Despite the high degree of retention and oxidation of organic inputs to Creeping Swamp, there is a net annual fluvial export of 21 gC/m2, mostly in the dissolved form. Watersheds drained by swamp—streams in the southeastern United States are thought to have large organic carbon exports compared to upland forested drainages, because the stream network covers a much greater proportion of the total watershed area.
Reproductive Interdependence of Pinon Jays and Pinon Pines
Authors: Ligon J. David
Published: April 2006

Pinon Jays (Gymnorhinus cyanoephalus) and pinon pine trees (Pinus edulis) interact in a mutualistic fashion, in that the jays provide a primary means of seed dissemination for pinon trees in the Southwest, while at irregular intervals the trees provide the jays with an abundant and highly nutritious source of food. Availability of pinon seeds permits both late winter (February) and late summer (August) breeding by the jays. Seeds and photoperiod interact synergistically to accelerate gonadal development in late winter. When seeds are abundant, considerable testis growth takes place in some Pinon Jay ♂ ♂ even before the winter solstice. This relationship was investigated experimentally. Use of a specific food (pinon seeds) as a proximate timer for breeding, the ability of individual jays to breed in spring, molt, and breed again in August without an intervening period of gonadal refractoriness, and testicular development in early December, when day length approaches its minimum, are extraordinary characteristics among north—temperate—zone passerine birds. The synchrony of seed production by pinon pines over large geographic areas is interpreted as an evolved mechanism that (1) overwhelms invertebrate seed and cone predators, and (2) increases the numbers of seeds per tree that will be cached by Pinon Jays and other vertebrates. Caching sites of Pinon Jays are often at locations especially conducive to germination and growth of pinon pine seedlings.
Foraging Movements of a Frugivorous Bat, Carollia perspicillata (Phyllostomatidae)
Authors: Heithaus E. Raymond , Fleming Theodore H.
Published: April 2006

The foraging movements of a Neotropical frugivorous bat (Carollia perspicillata)were studied to better understand its impact on the plants it disperses and the factors influencing its foraging behavior. Radio telemetry was used during 2 wet seasons to monitor the bats' movements in a Costa Rican seasonal tropical forest. We monitored 24 individuals for periods of up to 19 nights. This sample size permitted a statistical analysis of the influence of bats' weight, bat's sex, moonlight, and the distribution of resources on foraging patterns. Carollia perspicillata is a refuging species: individuals dispersed from shared day roots to feed at night, then returned after foraging. At night there were 3 major activity periods, but there was some activity all night. When foraging, each individual went to 2 to 6 feeding areas that were used consistently through the observation period. Each night it flew back and forth between areas. Searching for new feeding areas was uncommon. Average flight distances for individuals were 1.6 kilometres between the day roost and feeding areas, 1.5 km among feeding areas, and 1.6 km to gather fruits within feeding areas. The density at feeding areas decreased with distance from the day roost, as predicted by refuging theory. There was little overlap among different individuals' feeding areas, but the largest amount of overlap was adjacent to 1 day roost. Bats from the 2 major day roosts shared feeding a areas only at locations midway between the roosts. Flight patterns were influenced by bats' weights, the patchiness of resources, and the amount of moonlight. From these and other observations, we infer that both predation and energetic considerations affect C. perspicillata foraging. In addition, this species appears to respond to long—term factors as well as night—to—night conditions so that dynamic models will be necessary to describe its foraging.
The Metapopulation Ecology of the Red‐Spotted Newt, Notophthalmus viridescens (Rafinesque)
Authors: Gill Douglas E.
Published: April 2006

The population dynamics and ecology of the red—spotted newt were studied from 1974 to the present in a series of mountain ponds in the Shenandoah Mountains, Virginia. Adult and juvenile newts were censused using a combination of methods, including drift fences and dip—netting. A technique of individual recognition was developed utilizing the number and pattern of dorsal red spots. Assisted by a simple system of toeclips, designating pond and year of first capture, these methods provided records of age, survival, and movements of >8,500 individuals. The results revealed 2 migratory peaks of adults each year: a breeding migration to ponds in March, and an August—September emigration to terrestrial hibernacula. Breeding population size, ranging from 6 to >2,600 adults per pond was stationary during the study but was significantly correlated with pond age. Annual turnover of breeding populations to new adults exceeded 50%. Sex ratios were consistently 2 ♂ ♂: 1 ♀ in the breeding populations but tended toward 1:1 in the cohorts of new recruits. Annual adult ♀ survival was density dependent and significantly less than that of♂ ♂. The average ♀ expected to breed only 1.3 times, whereas ♂ ♂ had an expectancy of 1.9 breeding seasons. Faithfully homing to the same pond year after year, adults never migrated to new ponds between breeding seasons. Juvenile production at most ponds was poor over the 3 yr. Only 1 pond had a reproductive output consistently above a calculated replacement rate. It is inferred from the combination of poor reproduction and high immigration rates that breeding adults were not replaced by their own progeny but rather by foreign—born individuals. The red—spotted newt is basically a colonizing species responding to pond habitats that rapidly shift in time and space. It is suggested that beaver ponds have the necessary attributes of small size and temporal instability to which the life—history patterns of newts seems adapted. The majority of ponds in this area functioned as reproductive sinks in a larger, metapopulational structure. Adults in such ponds were reproductive failures or most of their lives. Only a small number of adults accounted for the regional reproduction in 1974 and 1975, but I very populous pond produced >91% of the young in 1976. Because reproductive success is pond dependent, interdemal selection may play an important role in newt evolution. It is hypothesized that homing behavior evolved as a consequence of natural selection within metapopulation centers and that the eft stage is the mechanism of dispersibility to new ponds. A new model of metapopulational dynamics is presented.
Evaluation of Mortality Factors in Insect Life Table Analysis
Authors: Royama T.
Published: April 2006

An individual animal may suffer simultaneously from several different maladies, which lead to its eventual death. Such "overlaps" between contemporaneous mortality factors create some problems in partitioning, in a consistent manner, the animals killed among several specific causes. The aim of this paper is to develop the notion of "killing power" of a mortality factor, so that we can properly evaluate and incorporate in a model the effect of any given factor on the dynamics of the animal population concerned. I first introduce the basic notion of killing power under the assumption that the mortality factors involved are operating independently of each other. The killing power of a given factor is then shown to be equivalent to the marginal probability of an animal being killed by that factor. The assumption of independence of the mortality factors is relaxed, and the more general notion of conditional killing power is introduced. This is equivalent to the conditional probability of an animal being killed by a given mortality factor, when that individual has not been simultaneously affected by other contemporaneous factors. The concept of mutually exclusive mortality factors is discussed to clarify an apparent confusion in some published literature. Typical examples of this type of mortality factor are an extended drought and excessively wet weather, both of which may kill some animals, but which will not occur simultaneously. Therefore, unless the stage division in the life tables so broad that these types of factors can occur in the same stage, we do not need to consider mutually exclusive mortality factors. How to evaluate the killing power of a mortality factor is illustrated with some examples taken from the literature. Also discussed is a more complicated case, in which the annual fluctuation in the proportion of animals killed by a given factor is correlated with those killed by other contemporaneous mortality factors. Concluding remarks include some notes on the division of stages in a life table so as to facilitate the evaluation of the killing powers of as many mortality factors as possible.
The Influence of Epiphytic Lichens on the Nutrient Cycling of an Oak Woodland
Authors: Knops Johannes M. H. , Nash Thomas H. , Schlesinger William H.
Published: April 2006

We examined the importance of the epiphytic lichen, Ramalina menziesii, in a blue oak (Quercus douglasii) woodland of California, using a factorial experiment in which lichens were removed from tree canopies and the soil surface for 3—yr period. Each blue oak contained an average of 3.8 kg of lichen biomass, totaling 590 kg/ha for the entire woodland; oak leaf biomass was 958 kg/ha. Removal of lichens affected the interception of rainfall by the forest canopy and the deposition of water and nutrients in throughfall collected beneath the canopy. Trees with lichens had higher deposition of total N, organic N, Ca, Mg, Na, and Cl, and a lower deposition of SO4 under their canopy; deposition of NO3, NH4, K, and total P was not affected. Accounting for the uptake of nutrients by lichens, we calculate that canopy lichens enhance the receipt of N and P from the atmosphere by 2.85 and 0.15 kg·ha—1· yr—1, respectively. The bulk deposition (wetfall + sedimentation) of N and P for the same period was 0.88 and 0.06 kg·ha—1·yr—1, respectively. Because retranslocation of N occurred prior to leaf abscission, the percentage of N in leaf litter was approximately half that in lichen litter. Lichen litter significantly slowed the decomposition of oak leaves on the forest floor. Oak leaf and lichen litter decomposition was slow, with low N release; whereas P release was much more rapid. The removal of lichens had no effect on leaf biomass or nutrient content, acorn productivity, or tree—ring increment of the oak trees, probably because soil pools of N and P were large relative to the magnitude of the flux changes caused by the manipulations. In fact, no differences in soil mineralization rates among the treatments were detectable. Overall, the manipulations significantly affected annual intersystem capture of nutrients, but the magnitude of these changes was insufficient to affect intrasystem fluxes or forest productivity.