bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the statistical analysis of vegetation change: a wetland affected by water extraction and soil acidification
Authors: ter Braak Cajo J.F. , Wiertz Jaap 
Published: May 2006

Abstract. A case study is presented on the statistical analysis and interpretation of vegetation change in a wetland subjected to water extraction and acidification, without precise information on the environmental changes. The vegetation is a Junco‐Molinion grassland and the changes in vegetation are evaluated on the basis of relevés in 1977 and 1988 of 20 plots in a small nature reserve on moist oligotrophic, Pleistocene sands in the Netherlands. The changes are attributed to water extraction (since 1972) and soil acidification and the effect of the environmental changes on the vegetation is inferred from data on water depth and acidity collected in 1988.Many species typical of wetlands decreased in abundance, including rare species such as Parnassia palustris, Selinum carvifolia and Ophioglossum vulgatum. Some species increased, notably Anthoxanthum odoratum, Holcus lanatus and Plantago lanceolata. A significant decrease was found in the mean Ellenberg indicator values for moisture and acidity. The mean indicator value for nutrients did not change significantly.Multivariate analysis of the species data by Redundancy Analysis demonstrated the overall significance of the change in species composition between 1977 and 1988 (P < 0.01, Monte Carlo permutation). The spatial and temporal variation in the species data was displayed in ordination diagrams and interpreted in terms of water depth and pH.A simple model is developed to infer the change in water depth and pH from the relevé data and recent data on water depth and pH. Because the correlation between water depth and pH made a joint estimation of the changes useless, the change in pH was estimated for a series of likely changes in water depth. For the most likely change in water depth, significant acidification was inferred from the change in vegetation. The model is more generally applicable as a constrained calibration method.
Ecological response surfaces for North American boreal tree species and their use in forest classification
Authors: Lenihan James M. 
Published: May 2006

Abstract. Empirical ecological response surfaces were derived for eight dominant tree species in the boreal forest region of Canada. Stepwise logistic regression was used to model species dominance as a response to five climatic predictor variables. The predictor variables (annual snowfall, degree‐days, absolute minimum temperature, annual soil moisture deficit, and actual evapotranspiration summed over the summer months) influence the response of plants more directly than the annual or monthly measures of temperature and precipitation commonly used in response surface modeling. The response surfaces provided estimates of the probability of species dominance across the spatial extent of North America with a high degree of success. Much of the variation in the probability of dominance is apparently related to the species' individualistic response to climatic constraints within different airmass regions.A forest type classification for the Canadian boreal forest region was derived by a cluster analysis based on the probability estimates. Five major forest types were distinguished by the application of a stopping rule. The predicted forest types showed a high degree of geographic correspondence with the distribution of forest types in the actual vegetation mosaic. The distribution of the predicted types also bears a direct relationship to seasonal airmass dynamics in the boreal forest region.
Past and current trends of change in a dune prairie/oak savanna reconstructed through a multiple‐scale history
Authors: Cole Kenneth L. , Taylor Robert S. 
Published: May 2006

Abstract. The history of a rapidly changing mosaic of prairie and oak savanna in northern Indiana was reconstructed using several methods emphasizing different time scales ranging from annual to millennial. Vegetation change was monitored for 8 yr using plots and for 30 yr using aerial photographs. A 20th century fire history was reconstructed from the stand structure of multiple‐stemmed trees and fire scars. General Land Office Survey data were used to reconstruct the forest of A.D. 1834. Fossil pollen and charcoal records were used to reconstruct the last 4000 yr of vegetation and fire history.Since its deposition along the shore of Lake Michigan about 4000 yr ago, the area has followed a classical primary dune successional sequence, gradually changing from pine forest to prairie/oak savanna between A.D. 264 and 1007. This successional trend, predicted in the models of Henry Cowles, occurred even though the climate cooled and prairies elsewhere in the region retreated. Severe fires in the 19th century reduced most tree species but led to a temporary increase in Populus tremuloides. During the last few decades, the prairie has been invaded by oaks and other woody species, primarily because of fire suppression since A.D. 1972.The rapid and complex changes now occurring are a response to the compounded effects of plant succession, intense burning and logging in the 19th century, recent fire suppression, and possibly increased airborne deposition of nitrates. The compilation of several historical research techniques emphasizing different time scales allows this study of the interactions between multiple disturbance variables.
Vertical distribution of below‐ground biomass in intensively grazed mesic grasslands
Authors: Rodríguez Miguel A. , Alvarez Javier , Gómez‐Sal Antonio 
Published: May 2006

Abstract. Previous work has shown that below‐ground biomass is more concentrated in surface soil layers in intensively grazed mesic grasslands than in moderately grazed grasslands. However, since the mesic grasslands previously studied shared similar compositional traits, the question remained whether grasslands with differing species composition, and intensive defoliation, showed similar biomass distribution patterns. Eight grasslands at four sites distributed along an elevational gradient were investigated. The upper and lower zones of a slope were sampled at each site. Four of these grasslands were grazed by livestock and the other four were grazed and mown. Biomass was divided into above‐ground, root crown and three root layers.Species composition varied according to management and topography. Annuals and perennial forbs had relatively more above‐ground biomass at the upper part of the slopes, while perennial grasses dominated the lower parts. The above‐ground biomass and root biomass at 4 — 7 cm depth attained maximum values in the lower, potentially more fertile, parts of the slopes. Crown biomass increased with altitude at the upper part of the slopes. Despite their differences in composition and structure, seven out of the eight stands showed a remarkable concentration of the below‐ground biomass near the soil surface, which decreased drastically with soil depth. This pattern is similar to that observed in the intensively grazed mesic communities studied earlier. This similarity was more evident in the more mesic‐like grasslands, since it increased from the upper, potentially drier parts of the slopes, to the lower parts, and, when each topographic position was considered separately, from low to high elevation.
Impact of grazing on vegetation dynamics in former ricefields
Authors: Mesléard F. , Lepart J. , Tan Ham L. 
Published: May 2006

Abstract. In the Rhône delta, Juncus gerardi and Scirpus maritimus are often the dominant species in abandoned rice fields which are artificially flooded in early spring to improve forage production. Under these conditions they occur either in mixed communities, or form monospecific stands. Monitoring the vegetation dynamics in quadrats located in six abandoned rice fields artificially flooded from November to April confirmed the important role of grazing.In ungrazed plots, communities dominated by Scirpus maritimus mixed with Juncus gerardi developed fast. After 42 months of management Scirpus maritimus had established in nearly all quadrats and continued to expand, whereas Juncus gerardi had started to decline.In grazed plots Juncus gerardi alone dominated and continued to increase in cover up to the 42nd month. Scirpus maritimus established at low densities mainly in quadrats where Juncus gerardi was initially absent. Introduction of seeds of Scirpus maritimus in communities of Juncus gerardi under controlled conditions demonstrated the existence of the phenomenon of preemption.The increase in cover of Juncus gerardi suggests that the preemption of Juncus gerardi over Scirpus maritimus plays a more pronounced role in the field in the presence of grazing.
Seed predation, disease and germination on landslides in Neotropical lower montane wet forest
Authors: Myster Randall W. 
Published: May 2006

Abstract. Seed mortality (caused by predators and pathogens) and germination were compared between Puerto Rico and Costa Rica on landslides in lower montane wet forest. Seeds of six common species on five Puerto Rican landslides and four common species on two Costa Rican landslides were used with a Cecropia species and a Gonzalagunia species included at both sites. In the Puerto Rican experiments Cecropia schreberiana was the only species to show significant seed predation (which was due to insects), pathogens grew from all species and fewer seeds were lost to predators than pathogens. Also in Puerto Rico mean germination across all species was 57 % before dispersal (filled seeds collected while still on the tree) and 71 % after, with Phytolacca rivinoides seeds germinating most abundantly, followed in descending order by Ocotea leucoxylon, Cecropia spec, Miconia racemosa, Palicourea riparia and Gonzalagunia spicata. In the Costa Rican experiments three species had significant predation: Cecropia polyphlebia and Urera caracasana (both due to insects) and Witheringia coccoloboides (due to mammals); pathogenic disease caused more seed loss than predation, and germination was high (61 % pre‐dispersal, 69 % post‐dispersal).Similarities between these island and mainland sites included (1) percentage of seeds lost to predation and percentage lost to pathogens (all in the 5–15 % range), (2) generalist pathogens which claimed more seeds than predators and (3) majority germination with a general increase after dispersal. Finally sites were dissimilar only in the number of species with significant predation loss and whether it was by insects or mammals, casting doubt on the traditional island/mainland dichotomy.
BOOK REVIEWS
Authors: Baskin Jerry M. 
Published: May 2006

Book reviewed in this article:Williams, J.E. & Woinarski, J.C.Z. (eds.) 1997. Eucalypt ecology: Individuals to ecosystems. xii + 430 pp. Cambridge University Press, Cambridge. ISBN 0 521 49740 X (hardback). Price USD 150.‐.
Tropical forest diversity, environmental change and species augmentation: After the intermediate disturbance hypothesis
Authors: Sheil Douglas 
Published: May 2006

Abstract.It is not simple to predict how environmental changes may impact tropical forest species diversity. Published hypotheses are almost invariably too incomplete, too poorly specified and too dependent upon unrealistic assumptions to be useful. Ecologists have sought theoretical simplicity, and while this has provided many elegant abstract concepts, it has hindered the attainment of more practical goals. The problem is not how to judge the individual hypotheses and arguments, but rather how to build upon and combine the many hard‐won facts and principles into an integrated science.Controversy is inevitable when the assumptions, definitions and applications of a given hypothesis are unclear. Elegance, as an end in itself, has too often been used to justify abstract simplification and a lack of operational definition. Clarifying and combining hypotheses while avoiding assumptions provides a potentially more useful, if less elegant, standpoint. An appraisal of Connell's intermediate disturbance hypothesis, and its application to long‐term observations from a Ugandan forest illustrates these concerns.Current emphases encourage ecologists to exclude consideration of environmental instability and non‐pristine ecosystems. In reality, many environmental changes and ecological processes contribute to both the accumulation and erosion of diversity, at all spatial and temporal scales. Site histories, contexts, long‐term processes, species‐pool dynamics, and the role of people require greater emphasis. These considerations reveal that many environmental changes, even those associated with degradation, can lead to a transient rise in species densities. Drawing on related studies, such as forest yield prediction, suggests that the formulation and calibration of simulation models provides the most tractable means to address the complexity of real vegetation. Simulation‐based approaches will become increasingly useful both in unifying the study of vegetation dynamics and in providing improved predictive capacity. Quantification of the processes, scales and sensitivities of the dynamics of tropical forest communities remains a major challenge.
Geometry, Calculus and Zil'ber's Conjecture
Authors: Peterzil Ya'acov , Starchenko Sergei 
Published: May 2006

§1. Introduction. By and large, definitions of a differentiable structure on a set involve two ingredients, topology and algebra. However, in some cases, partial information on one or both of these is sufficient. A very simple example is that of the field ℝ (or any real closed field) where algebra alone determines the ordering and hence the topology of the field:In the case of the field ℂ, the algebraic structure is insufficient to determine the Euclidean topology; another topology, Zariski, is associated with the ield but this will be too coarse to give a diferentiable structure.A celebrated example of how partial algebraic and topological data (G a locally euclidean group) determines a differentiable structure (G is a Lie group) is Hilbert's 5th problem and its solution by Montgomery-Zippin and Gleason.The main result which we discuss here (see [13] for the full version) is of a similar flavor: we recover an algebraic and later differentiable structure from a topological data. We begin with a linearly ordered set ⟨M, <⟩, equipped with the order topology, and its cartesian products with the product topologies. We then consider the collection of definable subsets of Mn, n = 1, 2, …, in some first order expansion ℳ of ⟨M, <⟩.
From “Metabelian ℚ-Vector Spaces” to New ω-Stable Groups
Authors: Chapuis Olivier 
Published: May 2006

The aim of this paper is to describe (without proofs) an analogue of the theory of nontrivial torsion-free divisible abelian groups for metabelian groups. We obtain illustrations for “old-fashioned” model theoretic algebra and “new” examples in the theory of stable groups. We begin this paper with general considerations about model theory. In the second section we present our results and we give the structure of the rest of the paper. Most parts of this paper use only basic concepts from model theory and group theory (see [14] and especially Chapters IV, V, VI and VIII for model theory, and see for example [23] and especially Chapters II and V for group theory). However, in Section 5, we need some somewhat elaborate notions from stability theory. One can find the beginnings of this theory in [14], and we refer the reader to [16] or [21] for stability theory and to [22] for stable groups.§1. Some model theoretic considerations. Denote bythe theory of torsion-free abelian groups in the language of groups ℒgp. A finitely generated groupGsatisfiesiffGis isomorphic to a finite direct power of ℤ. It follows thataxiomatizes the universal theory of free abelian groups and that the theory of nontrivial torsion-free abelian groups is complete for the universal sentences. Denote bythe theory of nontrivial divisible torsion-free abelian groups.
Machines, Logic and Quantum Physics
Authors: Deutsch David , Ekert Artur , Lupacchini Rossella 
Published: May 2006

§1. Mathematics and the physical world. Genuine scientific knowledge cannot be certain, nor can it be justified a priori. Instead, it must be conjectured, and then tested by experiment, and this requires it to be expressed in a language appropriate for making precise, empirically testable predictions. That language is mathematics.This in turn constitutes a statement about what the physical world must be like if science, thus conceived, is to be possible. As Galileo put it, “the universe is written in the language of mathematics”. Galileo's introduction of mathematically formulated, testable theories into physics marked the transition from the Aristotelian conception of physics, resting on supposedly necessary a priori principles, to its modern status as a theoretical, conjectural and empirical science. Instead of seeking an infallible universal mathematical design, Galilean science usesmathematics to express quantitative descriptions of an objective physical reality. Thus mathematics became the language in which we express our knowledge of the physical world — a language that is not only extraordinarily powerful and precise, but also effective in practice. Eugene Wigner referred to “the unreasonable effectiveness of mathematics in the physical sciences”. But is this effectiveness really unreasonable or miraculous?Numbers, sets, groups and algebras have an autonomous reality quite independent of what the laws of physics decree, and the properties of these mathematical structures can be just as objective as Plato believed they were (and as Roger Penrose now advocates).
American Logic in the 1920s
Authors: Davis Martin 
Published: May 2006

In 1934 Alonzo Church, Kurt Gödei, S. C. Kleene, and J. B. Rosser were all to be found in Princeton, New Jersey. In 1936 Church founded The Journal of Symbolic Logic. Shortly thereafter Alan Turing arrived for a two year visit. The United States had become a world center for cutting-edge research in mathematical logic. In this brief survey1we shall examine some of the writings of American logicians during the 1920s, a period of important beginnings and remarkable insights as well as of confused gropings.The publication of Whitehead and Russell's monumentalPrincipia Mathematica[18] during the years 1910-1913 provided the basis for much of the research that was to follow. It also provided the basis for confusion that remained a factor during the period we are discussing. In 1908, Henri Poincaré, a famous skeptic where mathematical logic was concerned, wrote pointedly ([13]):It is difficult to admit that the wordifacquires, when written ⊃, a virtue it did not possess when writtenif.Principiaprovided no very convincing answer to Poincaré. Indeed the fact that the authors ofPrincipiasaw fit to place their first two “primitive propositions”*1.1: Anything implied by a true proposition is true.*1.2: ⊢p⋁p⊃punder one and the same heading suggest that they had thought of what they were doing as just such a translation as Poincare had derided.
A Model-Theoretic Approach to Ordinal Analysis
Authors: Avigad Jeremy , Sommer Richard 
Published: May 2006

AbstractWe describe a model-theoretic approach to ordinal analysis via the finite combinatorial notion of an α-large set of natural numbers. In contrast to syntactic approaches that use cut elimination, this approach involves constructing finite sets of numbers with combinatorial properties that, in nonstandard instances, give rise to models of the theory being analyzed. This method is applied to obtain ordinal analyses of a number of interesting subsystems of first- and second-order arithmetic.
Degree Spectra of Relations on Computable Structures
Authors: Hirschfeldt Denis R. 
Published: May 2006

There has been increasing interest over the last few decades in the study of the effective content of Mathematics. One field whose effective content has been the subject of a large body of work, dating back at least to the early 1960s, is model theory. (A valuable reference is the handbook [7]. In particular, the introduction and the articles by Ershov and Goncharov and by Harizanov give useful overviews, while the articles by Ash and by Goncharov cover material related to the topic of this communication.)Several different notions of effectiveness of model-theoretic structures have been investigated. This communication is concerned withcomputablestructures, that is, structures with computable domains whose constants, functions, and relations are uniformly computable.In model theory, we identify isomorphic structures. From the point of view of computable model theory, however, two isomorphic structures might be very different. For example, under the standard ordering of ω the success or relation is computable, but it is not hard to construct a computable linear ordering of type ω in which the successor relation is not computable. In fact, for every computably enumerable (c. e.) degree a, we can construct a computable linear ordering of type ω in which the successor relation has degree a. It is also possible to build two isomorphic computable groups, only one of which has a computable center, or two isomorphic Boolean algebras, only one of which has a computable set of atoms. Thus, for the purposes of computable model theory, studying structures up to isomorphism is not enough.
III.—Telesphoros at Dionysopolis
Authors: Wroth Warwick 
Published: May 2006

Since the publication of my article on Telesphoros in the last number of the Journal of Hellenic Studies (Vol. III. pp. 283–300) my attention has been drawn to certain coins of Dionysopolis in Phrygia which seem to indicate the existence of a cultus of Telesphoros at that place. Two of these coins are in the British Museum, and the third will probably be acquired in a short time for the same collection:—1. Obv. ΔΗΜΟС Youthful head of Demos r.
Inscriptions from Rhodes
Authors: Smith Cecil 
Published: May 2006

Impressions of the following additional inscriptions have been sent me by Mr. Albert Biliotti, from marbles found by himself or his agents at different parts of Rhodes:—10. On a fragment of marble complete on the top edge only. From the Akropolis of Kamiros. Height 10 in. by 13½ in.This seems to be a fragment of a list of priests, ἱερεῖς, ἱεροποιοὶ, or ἱεροθύται, perhaps similar to Foucart, No. 62: the letters are clear, well cut, and of a fairly good period. It is unfortunate that the upper portions containing the names of deities should be so little preserved; there is sufficient however still remaining to enable us to recover the title of a deity who has been I believe hitherto unknown—Apollo Mylas—such at least seems to be a reasonable explanation of the fragmentary word at the end of the second line.
Ceramus (Κέραμος) and its Inscriptions
Authors: Hicks E. L. 
Published: May 2006

Mr. W. R. Paton, who is very well acquainted with the Gulf of Cos, has been good enough to send me some impressions and copies which he recently made of inscriptions at Keramo, the site of the ancient Ceramus. So few are the documents hitherto published from this town, that I readily consented to edit these copies for the Journal, the more so because I had been led to study the history of Caria somewhat minutely in connexion with another town of this region, Iasos. It happens also that one of the very few instances where Ceramus is named, even in inscriptions, is in a decree of Ephesus, discovered by Mr. Wood and now in the British Museum, which I have recently prepared for the press. We shall have occasion to refer to it presently.Before proceeding to examine the inscriptions, I am glad to transcribe an account of the neighbourhood of Ceramus which I begged Mr. Paton to draw up, knowing well how interesting such particulars are to less-travelled students of Greek antiquities.