bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Evaluation of the Rice Outlook and Situation Price Forecasts
Authors: Elam Emmett W. , Holder Shelby H. 
Published: July 2016

AbstractThe Rice Outlook and Situation (RO&S) forecasts were compared to the forecasts of a univariate Box-Jenkins (BJ) model. On balance, the RO&S forecasts had lower mean square forecast errors and lower mean absolute forecast errors than the BJ model forecasts. The differences in the squared and absolute forecast errors were not significant, however. Based on the concept of conditional efficiency as set forth by Granger and Newbold, it was found that the BJ forecasts did not add any information that might improve forecast accuracy beyond what was already incorporated in the RO&S forecasts.
Wheat Acreage Response: Investigation a Regional Econometric Investigation
Authors: Bailey Kenneth W. , Womack Abner W. 
Published: July 2016

AbstractAn econometric model of planted wheat acreage was estimated for five distinct production regions in the United States. This structural investigation represents an update of previous published work with specific attention given to policy program variables, weather, production cost, risk, market price influences, and program participation. Estimated results indicated regional divergence in responsiveness to government program variables. The most significant divergence occurred in the Cornbelt and Southeast—soft red winter wheat areas. Results indicate that management of the wheat program from the USDA level will contain countervailing production incentives unless these regional characteristics are taken into consideration in policy directives.
The Pricing Efficiency of Agricultural Futures Markets: An Analysis of Previous Research Results
Authors: Garcia Philip , Hudson Michael A. , Waller Mark L. 
Published: July 2016

AbstractThe analysis examines quantitatively the findings of previous studies of the pricing efficiency of various agricultural markets using a logit framework. The findings provide insight into the importance of commodity characteristics, uncertainty, and testing procedures used on the results of past research of pricing efficiency. The study also identifies several areas for further research.
Patenting Life Forms: Issues Surrounding the Plant Variety Protection Act
Authors: Claffey Barbara A. 
Published: July 2016

This paper examines the issues surrounding the patenting of life forms, specifically the social and private costs and benefits of the Plant Variety Protection Act (PVPA) (Plant Variety Protection Act, 1970). The PVPA is a current issue, encompassing all the elements of the economic, social, and moral controversy aroused by the broader issue of patenting life forms generally.The subsequent sections of the paper outline the specific issues surrounding the PVPA, discuss the issue of plant patenting, present the arguments favoring and opposing plant patenting, and, finally, present an analysis of the major issues of the PVPA.
Linkages Between Crop Insurance and Pre-Harvest Hedging
Authors: Dhuyvetter Kevin C. , Kastens Terry L. 
Published: July 2016

AbstractThe impact pre-harvest hedging and crop insurance strategies have on expected revenue and associated risk as well as how producers' risk attitudes affect optimal strategies was analyzed for Kansas wheat farms. No insurance, Catastrophic (CAT), Actual Production History (APH), and Crop Revenue Coverage (CRC) were considered. Average revenue was similar across alternatives, but APH and CRC resulted in the least income variability. Risk reduction effects of hedging were small and the advantage of CRC over APH decreases as hedging increases. This historical study provides useful information; however, if future market conditions differ significantly from the past, optimal strategies may change.
Impacts of Within-Farm Soil Variability on Nitrogen Pollution Control Costs
Authors: VanDyke Laura S. , Bosch Darrell J. , Pease James W. 
Published: July 2016

AbstractThe effects of considering variable within-farm soil runoff and leaching potential on costs of reducing nitrogen losses are analyzed for a Virginia dairy. Manure applications may cause nitrogen losses through runoff and leaching because of factors such as uncertain nitrogen mineralization. Farmers can reduce nitrogen control costs by applying manure on soils with less nitrogen loss potential. Ignoring within-farm soil variability may result in overstating the farm's costs of reducing nitrogen losses.
Accounting for Spatial Characteristics of Watersheds in Evaluating Water Pollution Abatement Policies
Authors: Qiu Zeyuan , Prato Tony 
Published: July 2016

AbstractThis study evaluates three agricultural nonpoint pollution abatement policies: regulating the spatial pattern of agricultural activities, ambient tax, and abatement tax/subsidy. All three policies incorporate spatial characteristics of agricultural emission loading and movement for an agricultural watershed in the Midwest. The effects of spatial variation in natural conditions and landscape features on agricultural emissions and crop yield are evaluated using a newly developed biophysical simulation model and experimental data. While the policies are equally cost effective in reducing agricultural nonpoint source pollution, their implementation feasibility is quite different.
Environmental versus genetic causes of morphologic variability in bryozoan colonies from the deep sea
Authors: Schopf Thomas J. M. 
Published: July 2016

Bryozoans are colonial animals and this permits the partitioning of their morphologic variability into components of within colony (i.e. within a single genotype) and between colony (i.e. between genotype) variance. These data have been obtained for four species of the endemic deep-sea genus Euginoma for a series of characters. In 8 comparisons, one component of the total variance dominated at the 5% level. Population (between colony) variance contributed significantly to the total variance in 63% of the comparisons (5 of 8); individual (within colony) variance contributed significantly to the total variance in 37% of the comparisons (3 of 8).Compared to shallow water species, the surprising feature of the deep-sea data is that the between colony component of variance is as high as it is. Possibly in the more stable, deep-sea environment, the genotypic contribution to the variance of each individual colony is expressed to a greater degree than in the more variable, shallow water regime. If so, then analyses of variability in colonial animals may be an independent means of ascertaining stability gradients in the fossil record.
Covariation patterns in the postcranial skeleton of moas (Aves, Dinornithidae): A factor analytic study
Authors: Cracraft Joel 
Published: July 2016

The covariation patterns of the postcranial skeleton in eight species of moas (Aves, Dinornithidae) from the Pleistocene of New Zealand are described using multiple factor analysis. Rotation schemes include an orthogonal Varimax and oblique (direct quartimin) simple structure solutions.Four major patterns of covariation are resolved: a length factor, primarily that of leg length; a width factor, including pelvis width and long bone widths; a sternal breadth factor; and a sternal length-posterior pelvis length factor. The first two patterns represent a functional separation between body size and those aspects of the skeleton, scaling allometrically, adapted to support body weight. The sternal breadth factor may indicate that features contributing to trunk support are independent from those width measurements of the pelvis and hindlimb bones. The sternal length-posterior pelvis length factor reveals a pattern of covariation that is somewhat independent of other patterns (long bone lengths) determining variability in body size.
Growth models in fossil arborescent cheilostome bryozoans
Authors: Cheetham Alan H. , Hayek Lee-Ann C. , Thomsen Erik 
Published: July 2016

Cheilostome bryozoans that grew as rigidly erect arborescent colonies dominate many bryozoan-rich assemblages of Tertiary age, in which they are found most commonly as small dissociated fragments. The regularity with which branching and branch thickening occur in intact colonies of living species provides a basis for quantitative reconstruction of these growth processes in fossils. We propose models to describe branch thickening, develop methods to extend both thickening and branching models to fossils, investigate the thickening and branching properties of four Paleocene and five Oligocene species and compare the properties of these fossils to those of nine living species.The properties investigated are largely mutually independent and species specific irrespective of geologic age and have similar numerical ranges among different assemblages of coeval species. Species are evenly distributed across the range of possible morphologies between observed extremes, without obvious gaps. Statistically significant trends through time are identified in gradients of branch thickening, which have implications for the resistance of colonies to mechanical stress, and in angles of bifurcation, that are important in the way growing colonies occupy space.
Predation and Parallel Evolution: Recurrent Parietal Plate Reduction in Balanomorph Barnacles
Authors: Palmer A. Richard 
Published: July 2016

Field and laboratory data indicate that all four species of Thais (Gastropoda, Muricacea) from rocky shores of the northeastern Pacific selectively attack barnacles at the margins of parietal (lateral) and opercular plates. Attacks are also more likely to be successful at plate margins. Such preferential attack and differential attack success may account for the evolutionary reduction in the number of parietal plates exhibited within seven of the eight families of balanomorph barnacles. Additional evidence suggests that predation by drilling gastropods may have also favored the evolution of strong external ribbing on these plates within some balanomorph lineages.Radiation and plate reduction in the Balanomorpha occurred in concert with extensive radiation in muricacean gastropods, starting in the Late Cretaceous. Of the three skeletal conformations exhibited by open-surface dwelling barnacles (8, 6 and 4 parietal plates), only genera of the four-plated form have become proportionally more common in the Recent. Further, in a rather striking evolutionary experiment, a lineage of barnacles evolving free from gastropod predation retained primitive skeletal features. This supports the interpretation that predation by drilling gastropods has been an important selective force behind the widespread, parallel evolutionary tendency towards plate reduction in the Balanomorpha; a trend recognized by Darwin (1854), but for which he offered no explanation.
Age (Mortality) Profiles as a Means of Distinguishing Hunted Species from Scavenged Ones in Stone Age Archeological Sites
Authors: Klein Richard G. 
Published: July 2016

Some ungulate species at Upper Pleistocene and Holocene archeological sites in South Africa exhibit catastrophic mortality profiles, while others exhibit attritional ones. The awareness by Stone Age people that some species are especially amenable to driving or snaring probably accounts for the catastrophic profiles. Natural catastrophic death immediately followed by human scavenging is a much less likely explanation because the species samples comprise material lumped from deposits that accumulated more or less continuously over hundreds or even thousands of years during which period there is no reason to suppose the repeated occurrence of natural catastrophes nearby.The inability of Stone Age people to obtain prime-age adults in species that are not particularly amenable to driving or snaring presumably accounts for the attritional mortality profiles. Although the species that display attritional profiles conceivably were scavenged, the high proportion of very young individuals in the profiles suggests active hunting. Very young individuals are much less abundant in attritional profiles from local non-archeological sites, probably because their carcasses were removed from the record before burial, primarily by carnivore or scavenger feeding. Scavenging would account for the abundance of very young individuals in the archeological sites only in the unlikely event that people could regularly locate carcasses before other predators did.In general, geomorphic/sedimentologic context is probably the best criterion for determining whether a species characterized by a catastrophic profile in an archeological site was hunted or scavenged. At the majority of known sites, active hunting is suggested. In the case of a species characterized by an attritional profile in an archeological site, the proportion of very young individuals in the sample probably provides the best criterion for distinguishing hunting from scavenging. A relatively high proportion of very young individuals suggests active hunting.
Stabilizing species selection in the Archaeogastropoda
Authors: Gilinsky Norman L. 
Published: July 2016

Factor analysis of morphometric data from fossil and recent Archaeogastropoda reveals that there has been a progressive reduction in the variety of archaeogastropod shell shapes through time. High and low spired genera have slowly disappeared while equidimensional forms, which have always been the most common, have become even more abundant. The taxonomic manifestation of this trend has long been appreciated and involves: 1) the extinction of most of the Pleurotomariacea, the Euomphalacea, Trochonematacea, and several other superfamilies, which collectively comprise most of the variation in shape among early archaeogastropods, and 2) the proliferation of the primarily equidimensional Trochacea and Neritacea. I suggest that this macroevolutionary trend may be explained by the general process I refer to as “stabilizing species selection.” More specifically, I suggest that the mechanism of stabilizing species selection in the case presented here may have been differential rates of origination.I believe that the innovative concept of species selection has been burdened by the adherence of its advocates to the idea that differential extinction is its primary mechanism. This preference for differential extinction is rooted in our emphasis upon differential mortality in microevolution and is not based upon data of macroevolutionary change. I argue that differential origination may be as important as differential extinction in directing macroevolutionary change and that demographical and autecological properties of species may be its agents. Recognition of the importance of differential origination will have an important impact upon our concept of the relationship between adaptation and the evolutionary process.
Ideas on the timing of metazoan diversification
Authors: Stanley Steven M. 
Published: July 2016

Fossil data suggest that the great majority of metazoan classes that existed in the Early Cambrian arose after about 700 my ago. The rectangular model of evolution, which views most evolutionary change as being concentrated in speciation events, can easily accommodate the implied rate of divergence.If, as some authors believe, the eukaryotic cell arose long before the start of the Cambrian, an explanation is required for the delay of large-scale metazoan divergence. The advent of sexuality may have triggered diversification, not by accelerating phyletic evolution, as traditionally believed, but by making possible speciation and, hence, adaptive radiation. Another important delaying factor may have been the near-saturation of Precambrian algal systems in the absence of cropping by herbivores. Uncropped Precambrian systems should have been self-limiting in terms of diversification. When advanced heterotrophy finally arose, self-propagating feedback systems of diversification should have been set in motion. Even if the eukaryotic cell arose later than commonly envisioned and triggered the radiation of the Metazoa about 700 my ago, the earlier absence of sexuality and cropping may have delayed the transition from the prokaryotic condition to the eukaryotic condition.
Species diversity in the Phanerozoic: an interpretation
Authors: Raup David M. 
Published: July 2016

Species diversity among fossil invertebrates of the Phanerozoic is highly correlated with volume and area of sedimentary rocks. The correlations are statistically significant at the 1% level. The relationship holds even in regions (such as Canada) where the area and volume of rock do not increase through time. These results are interpreted as indicating that the apparent number of species is strongly dependent on sampling and that many of the changes in diversity seen in the Phanerozoic are artifactual. Consequently, there is no compelling evidence for a general increase in the number of invertebrate species from Paleozoic to Recent. This conclusion applies primarily to marine organisms. Diversity may have been in dynamic equilibrium throughout much of this time.A few intervals of the Phanerozoic have consistently fewer invertebrate species than would be predicted from the amount of sedimentary rock available for study. The Silurian, Permian, and Cretaceous stand out in this regard. This may result either from lower than normal diversity during these periods or from an unusual abundance of unfossiliferous rocks (evaporites, red beds, etc.).
Recruitment, growth, and mortality of a living articulate brachiopod, with implications for the interpretation of survivorship curves
Authors: Thayer Charles W. 
Published: July 2016

An intertidal sample of 118 to 155Terebratalia transversaon Saltspring Island, B.C., was censused in 1974, 1975, and 1976. Growth in length was a maximum of 7.8 mm per year and declined with size (age). As in fossil articulates, mortality rate was independent of age (size). Recruitment was patchy in time and space, was multi-annual or continuous, and was concentrated near conspecific adults. There were as many as 800 individuals/m2. None moved or changed orientation. Morphologic variation ofTerebrataliavalves is not directly controlled by the intensity of waves or currents.Paleontological survivorship curves based on size-frequency data are subject to ambiguous interpretation because two critical assumptions (direct relationship of size and age, constant population structure) are difficult to justify.
Form and function of orthoconic cephalopod shells with concave septa
Authors: Westermann G. E. G. 
Published: July 2016

Models of “ideal” orthoconic shells having simple concave septa with minimal weight and maximal strength and analysis of 72 species of fossil orthocones and cyrtocones yield important insights into the physical principles underlying cephalopod shell design. The ideal septum is a spherical cap weighing only 77% of a hemispherical septum of equal strength. The septa of most longicones approximate this ideal shape while those of brevicones are less curved, probably owing to buoyancy problems. Increase in septal strength leads to weight increase unless the shell becomes more logiconic or septal spacing increases or both. However, increased spacing requires more cameral liquid for septum formation, thus reducing buoyancy. In ideal longicones, septal spacing resembles the cone radius for thick, strong septa but declines to half of the cone radius for thin, weak septa. In ideal intermediates and brevicones, spacings are respectively reduced by factors of about 2 and 4, with similar additional dependence on septal thickness. Most real septa resemble these ideal models.The relative length of the body chamber to the phragmocone varies greatly between about 0.2 and 1.5, depending mainly on the wall thickness and to a lesser degree on the septal thickness, apical angle and body density. Removal of cameral liquid in the adult must be compensated for by additional growth to retain neutral buoyancy. The conditions for neutral equilibrium calculated for longicones with different “counterweights” indicate that: (1) cameral liquid only is least feasible; (2) half-and-half calcium carbonate and liquid results in one-third length and one-quarter volume reduction of the body chamber; (3) with calcium carbonate only, body chamber reduction is minimal. Real ‘counterweights’ appear to be intermediate between (2) and (3), providing the animal with horizontal stability, which is missing in (3). Most uncalcified siphuncles reduce the body chamber only slightly although they improve horizontal stability. If the wall attains full thickness only at the apical end of body chamber, the liquid-only ‘counterweight’ becomes feasible.
Genic heterozygosity and rate of speciation
Authors: Avise John C. 
Published: July 2016

The hypothesis is proposed that mean level of heterozygosity is functionally related to rate of speciation in evolutionary phylads. Under this hypothesis, phylads which speciate more rapidly do so because of increased level of within-species genetic variability which is then available to conversion to species differences under appropriate ecological or environmental conditions. An important corollary is that rate of speciation could be limited in phylads with low genetic variability, irrespective of environmental considerations.This hypothesis has been tested with respect to electrophoretically detectable variation in products of structural genes in two families of North American fishes characterized by grossly different rates of speciation. Totals of 69 species of the highly speciose Cyprinidae, and 19 species of the relatively depauperate Centrarchidae, were assayed for mean level of heterozygosity at 11–24 genetic loci. Since Cyprinidae and Centrarchidae exhibit on the average nearly identical levels of genic variation (Ĥ= 0.052 ± 0.004, andĤ= 0.049 ± 0.009, respectively), the hypothesis that level of heterozygosity affects rate of speciation in these fishes is not supported.Nonetheless, the amount of genic variability in both Cyprinidae and Centrarchidae is large, comparable to mean levels in previously studied vertebrates. The great wealth of genome variability, reflected in the electrophoretic variation present in virtually all outcrossing organisms, apparently can accommodate considerable flexibility in rate and pattern of evolutionary response to the various environmental regimes challenging organisms.
A provincial model of Phanerozoic marine diversity
Authors: Valentine James W. , Foin Theodore C. , Peart David 
Published: July 2016

Much new empirical evidence on the levels of Phanerozoic paleoprovinciality and of species diversity within paleocommunities now permits a reevaluation of marine diversity patterns. Data on paleoprovincial patterns are assembled from the literature and evaluated by means of a stochastic computer simulation model. The simulation is based on the statistics of modern patterns of diversity and endemism extrapolated conservatively to the paleoprovincial patterns and on estimates of species duration from the fossil record. The species diversities associated with the paleoprovincial patterns are then corrected for temporal changes in species packing in communities as determined by Bambach (1977) from studies of paleocommunities. The model thus has an empirical basis throughout. Furthermore it is free of biases that can arise due to the differential preservation of taxa in space and time.The Paleozoic and Mesozoic were characterized by low provinciality and low average species diversity, on the order of 38,000 to 40,000 species, although there were significant fluctuations in standing diversities. In the Cenozoic, provinciality rose markedly, primarily through the appearance of latitudinal provincial chains, and average species diversity rose to about 240,000. Today it stands over 350,000; this is an order of magnitude greater than the Paleozoic average.