bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of environment and grazing disturbance on tree establishment in meadows of the central Cascade Range, Oregon, USA
Authors: Miller Eric A. , Halpern Charles B. 
Published: May 2006

Abstract. Within the last century there has been widespread establishment of trees in mountain meadows of the Pacific Northwest. We reconstructed patterns of tree invasion at 17 meadow sites in the central Cascade Range of Oregon, USA ‐sites representing diverse physical environments and vegetation types and experiencing different histories of recent anthropogenic disturbance (sheep grazing). Spatial distributions and age structures of invasive tree populations were analysed with respect to climatic records and grazing history. Patterns of establishment varied considerably among meadows, reflecting strong differences in environment and grazing history. In montane hydric meadows, tree establishment was spatially clumped beneath large old trees and on elevated microsites; however the timing of invasion differed between sites with stable versus fluctuating water tables. In upland mesic/dry montane meadows, timing of invasion corresponded with cessation of sheep grazing (early 1940s) and the onset of wetter summers (mid 1940s). In the subalpine zone, climate and aspect interacted to produce contrasting histories of invasion on north‐ and south‐facing slopes.Establishment on north‐facing slopes, concentrated in heath‐shrub communities, coincided with regional warming (ca. 1920–1945) when snowpacks were lighter and melted earlier. Recruitment of trees onto south‐facing slopes occurred later, when conditions were wetter (1945–1985). In many environments, the spatial distribution of recruitment suggests that once trees have established, autogenic factors become increasingly important as individual trees or groups of trees alter the physical or biotic conditions that once inhibited establishment.Knowledge of the factors that influence invasion, and of their varying importance across gradients in environment and vegetation, is critical to predicting future changes in these dynamic systems.
Sixty years of vegetation dynamics in a south boreal coniferous forest in southern Norway
Authors: Nygaard Per Holm , Ødegaard Torbjørn 
Published: May 2006

Abstract. Vegetation data from permanent plots were collected in 1931, 1961 and 1991 in a south boreal forest 20 km north of Oslo in southern Norway. Major changes were found in the vegetation composition during those 60 years. The main changes were a reduction in the frequency of species and the frequency of joint occurrences of vascular species such as Andromeda polifolia, Calluna vulgaris, Cornus suecica, Eriophorum vaginatum, Maianthemum bifolium, Melampyrum pratense, Trientalis europaea, Vaccinium uliginosum and V. oxycoccus, and mosses, e.g. Dicranum fuscescens, Hylocomium splendens, Pleurozium schreberi, Ptilidium ciliare and Ptilium crista‐castrensis.The observed changes were interpreted as being induced by internal processes e.g. notably a long‐term change from paludified forest to mesic forest. In particular the growth of Picea abies seems to be a main driving force. The dominance of Picea abies and Vaccinium myrtillus appears to have rendered the conditions more unfavourable for other species. A doubling of the living stem biomass of P. abies during the last 67 yr shows that this old‐growth forest has not yet reached a steady state. It was demonstrated that species such as Deschampsia flexuosa and Molinia caerulea did not increase in frequency in response to nitrogen deposition, as has occurred elsewhere in northern Europe. pH in the humus layer increased with 0.2 unit from 1961 to 1991.The results of this study indicate that protection from logging has initiated the reduction of species in the field layer and bottom layer. This study questions if monitoring of forest vegetation should be restricted to protected forests as is the practice in Scandinavia today. We recommend that also areas with some kind of selective cutting will be used for monitoring of forest vegetation.
Relationship between spatial strategies and morphological attributes in a Uruguayan grassland: a functional approach
Authors: Altesor A. , Pezzani F. , Grun S. , Rodríguez C. 
Published: May 2006

Abstract. In a native grassland in Uruguay subjected to continuous grazing by cattle, four permanent plots of 40 × 40 cm were established. Plots were divided into 16 × 16 cells and the presence of species was recorded seasonally during two years. The spatial dynamic of the dominant species was defined through three parameters: persistence, short‐distance spread and long‐distance spread. The association between the spatial strategies and certain morphological attributes that were presumed to be important to the spatial behaviour of the species, was examined using Correspondence Analysis.Four types of spatial strategies were observed: (1) persisting over the year in the same cell without showing any type of mobility; (2) continuously growing due to the solid advancing front of ramets, persisting or not persisting (3) in the same cells; and (4) multi‐strategy with high persistence and both high short‐ and long‐distance spread. Among the selected attributes, the erect/prostrate habit, the capacity of vegetative propagation by means of bulbs, rhizomes or stolons, the ratio length/width of leaves and the season of active growth were the characteristics most closely associated with the spatial strategies.
Differentiation diversity of Argentine cacti and its relationship to environmental factors
Authors: Mourelle Cristina , Ezcurra Exequiel 
Published: May 2006

Abstract. We studied the differentiation diversity (β‐diversity or species turnover) patterns of the three main cactus growth forms (columnar, opuntioid and globose) in 318 (1° × 1°) squares covering Argentina. We analysed the degree of association between species turnover of each growth form with the spatial variation of a set of 15 environmental variables.Species turnover was estimated in two ways: (1) by calculating species turnover along latitudinal and longitudinal gradients and (2) by evaluating the species turnover between each square and its eight surrounding neighbouring grid cells.For the three growth forms, species turnover in latitudinal transects was mostly related to the mean within‐transect values of certain environmental variables, while in longitudinal transects it was related to the variation of some environmental variables within the transect rather than to their mean values. For columnar species, transect species turnover was mainly associated with variation in temperature, confirming the temperature‐sensivity of this growth form. For opuntioid species, turnover along transects was mainly related to topographic variables. In the case of globose cacti, transect turnover was associated with variation in temperature and rainfall.For the three growth forms, areas of high turnover coincided with marked transitions between different biogeographic provinces, while the areas with lowest species turnover coincide with topographically and climatically uniform plains. Species turnover between individual squares was positively associated with the proportion of summer rainfall in globose cacti, the variation of mean annual temperature in columnar cacti and was negatively related to mean annual temperature in opuntioid cacti. Compared to the other growth forms, globose cacti presented a much larger proportion of squares with a high species turnover.In general, differentiation diversity was lower for the opuntioid and the columnar species, two growth forms with higher dispersal ability and was highest for the globose cacti, which have the lowest dispersal capacity. Environmentally heterogeneous areas, where large‐scale transitions between biomes occur, have exceptionally high species turnover, and are important target areas for the conservation of biodiversity.
Plant functional traits and environmental filters at a regional scale
Authors: Diaz Sandra , Cabido Marcelo , Casanoves Fernando 
Published: May 2006

Abstract. Links between plant traits and the environment, i.e. sets of plant attributes consistently associated with certain environmental conditions, are the consequence of the filtering effect of climatic, disturbance and biotic conditions. These filters determine which components of a species pool are assembled into local communities. We aimed at testing for consistent association between plant traits and climatic conditions along a steep regional gradient, divided into 13 climatically homogeneous sectors, in central‐western Argentina. We analyzed 19 vegetative and regeneration traits of the 100 most abundant species along the gradient. For each trait, we tested for homogeneity of frequencies of different categories between sectors and the regional species pool, using the χ2 statistic. We rejected H0 in 71% of the pair‐wise comparisons, which strongly suggests a ‘filtering effect’ of climatic factors on key plant functions. Vegetative traits were filtered more often than regeneration traits. Specific leaf area, life span, ramification, canopy height, leaf weight ratio, carbon investment into support tissue and pollination mode were the traits showing differences in the largest number of pair‐wise comparisons.This is probably the first attempt to detect, on a quantitative, statistically conservative basis, consistent linkages between climatic factors and numerous plant traits, over a broad spectrum of environmental conditions and plant growth forms. We discuss the advantages and limitations of this approach in predicting vegetation structure and functioning under present environmental conditions, and those expected for the next century as a consequence of global change.
How season of grazing and herbivore selectivity influence monsoon tall‐grass communities of northern Australia
Authors: Ash Andrew J. , McIvor John G. 
Published: May 2006

Abstract. The hypothesis that season of defoliation and herbivore selectivity may be as important as level of use in determining plant community response to grazing was tested in a monsoon grassland in northern Australia. Plots, dominated by the tussock grasses Themeda triandra and Chrysopogon fallax, were grazed by cattle at low, medium and high rates of utilization in either the early wet, late wet or dry seasons. Effects of grazing on species composition were greatest in the early wet season when high rates of utilization significantly reduced the proportion and occurrence of Themeda and increased the proportion of forbs. Grazing in the dry season had no significant effect on composition.At medium and high levels of utilization in the early wet season, the pasture responded negatively to defoliation, only partially compensating for plant tissue lost to herbivory. The negative response to defoliation carried over to the next wet season when these same medium and high‐grazing treatments produced only 80 % and 60 % growth, respectively, of that in treatments grazed at low levels of utilization or those grazed during the dry season. The frequency of Themeda was still lower, and that of annual grasses and non‐leguminous forbs higher, in plots that had been grazed at a high rate of utilization for just eight weeks in the early wet season two years previously. Species richness and diversity were also significantly affected by this grazing disturbance. If species composition is to be maintained in these grasslands then stocking rates must be set at low levels to cope with the combined effect of undercompensation in response to defoliation in the wet season and strong dietary preferences for grazing sensitive species.
Flood drift and propagule bank of aquatic macrophytes in a riverine wetland
Authors: Cellot Bernard , Mouillot Florent , Henry Christophe P. 
Published: May 2006

Abstract. Drift of aquatic macrophyte propagules was investigated in a wetland along the River Rhône, during the first flood after the growing season (i.e. in the winter of 1995–1996). Input and output drift were studied at the beginning, around the top, and at the end of the river overflow in the upper reach of a cut‐off channel. The soil propagule bank was sampled along the study area before and after the flood. The amount and composition of viable propagule drift and bank were determined, analysed and compared. Drift densities and richness were on average higher at the outlet of the channel than at the inlet (respectively: 23.2 vs 13.1 viable propagules/100 m3 of water and 8.7 vs 2.6 taxa per sample). Immigrating taxa were mostly in the form of helophyte seeds, whereas numerous resident hydrophyte species left the disturbed area rather as vegetative propagules.Temporal variability in propagule bank structure was weak, and mean bank densities did not change before and after the flood (respectively: 33 047 ± 10 510 vs 35 653 ± 15 070 viable propagules/m2 of ground, including Chara). However, the density of Elodea canadensis significantly increased after the flood while that of Eleocharis acicularis decreased. This contrast suggests that flood responses vary among species. Despite a broad overlap in the taxa (18 out of 25 were common both to drift and bank collections), no significant relationship occurred in composition or structural changes between flood drift and propagule bank. Flood acted as a means of distribution of existing propagules and also as a provider of new vegetative dispersal units.
Simulated plant population responses to small‐scale disturbances in semi‐arid shrublands
Authors: Wiegand Thorsten , Dean W. Richard J. , Milton Suzanne J. 
Published: May 2006

Abstract. We used a spatially explicit simulation model to examine the impact of small‐scale disturbance (created by the digging of aardvarks, Orycteropus afer, and bat‐eared foxes, Otocyon megalotis or as a management action) on the temporal and spatial dynamics of a typical Karoo shrub plant community, and to gather insight into the interplay between disturbance structure and population dynamics. Establishment, growth, mortality, seed dispersal and competitive interactions were modelled over long time‐scales in annual time‐steps under the influence of stochastic and unpredictable rainfall.Three disturbance regimes were included, varying the type, rate and size of the small‐scale disturbances. The impact of a disturbance regime on long‐term community dynamics depends on complex interactions between disturbance characteristics and life‐history attributes of component species. Plant density decreased with overall disturbance rates; this effect was independent of the type of disturbance. A given type and rate of disturbance did not influence all species within a guild (e.g. colonizer species) in the same way. The reason for these differences was that species responded not only to the disturbance but to changes in competition intensity from other species and changes in their reproductive potential relative to other species as well. Such interactions resulted in a sequential change in dominant species within guilds as disturbance rates increased. An increase in the overall disturbance rate did not always produce the trend in evenness expected from the intermediate disturbance hypothesis, but was influenced by the relative abundance of different types of disturbance.
New Evidence on the Province of Asia
Authors: Habicht Christian 
Published: May 2006

In this paper the text of a new inscription from Ephesus will be presented and discussed. The fragmented stone on which it is written was brought by a workman to the excavation office in spring 1969. It is not known where exactly it was found, although D. Knibbe has suggested privately that it was originally set up in the Agora.Österreichisches Archäologisches Institut, Ephesus Inventory No. 3653. Fragment of a large slab of white marble, broken on top and at the bottom. The left margin is partly preserved, the right margin almost entirely. There are mouldings on both sides. The hollow in the form of a semicircle at the right margin originates in all probability from re-use of the stone.Height 75 cm. Width 68·5. Thickness 12·5. The height of the letters is 1·0, the distance between the lines 0·6 cm. The writing is in two columns which are separated from each other by a vertical scratch. This was made after the left column had already been engraved, as can be seen from the small detour in 1 19. Plate I. For the establishment of the text I have been able to use a large-scale photograph and the latex squeeze provided by the Austrian Archaeological Institute.
Analytic Ideals
Authors: Solecki Sławomir 
Published: May 2006

§1. Introduction. Ideals and filters of subsets of natural numbers have been studied by set theorists and topologists for a long time. There is a vast literature concerning various kinds of ultrafilters (or, dually, maximal ideals). There is also a substantial interest in nicely definable (Borel, analytic) ideals—these by old results of Sierpiński are very far from being maximal— and the structure of such ideals will concern us in this announcement. In addition to being interesting in their own right, Borel and analytic ideals occur naturally in the investigations of compact subsets of the space of all Baire class 1 functions on a Polish space (Rosenthal compacta), see [12, 18]. Also, certain objects associated with such ideals are of considerable interest and were quite extensively studied by several authors. Let us list here three examples; in all three of themIstands for an analytic or Borel ideal.1. The partial order induced byIonP(ω):X ≥IYiffX \ Y ϵ I([16]) and the partial order (I, ⊂)([18]).2. Boolean algebras of the formP(ω)/Iand their automorphisms ([6, 5, 19, 20]).3. The equivalence relation associated withI:XEIYiffX Δ ϵ I([4, 14, 15,9]).In Section 4, we will have an opportunity to state some consequences of our results for equivalence relations as in 3.
Gödel's Path from the Incompleteness Theorems (1931) To Phenomenology (1961)
Authors: Tieszen Richard 
Published: May 2006

In a lecture manuscript written around 1961 (Gödel *1961/?), Gödel describes a philosophical path from the incompleteness theorems to Husserl's phenomenology. It is known that Gödel began to study Husserl's work in 1959 and that he continued to do so for many years. During the 1960s, for example, he recommended the sixth investigation of Husserl'sLogical Investigationsto several logicians for its treatment of categorial intuition (Wang 1997, p. 164). While Gödel may not have been satisfied with what he was able to obtain from philosophy and Husserl's phenomenology, he nonetheless continued to recommend Husserl's work to logicians as late as the 1970s. In this paper I present and discuss the kinds of arguments that led Gödel to the work of Husserl. Among other things, this should help to shed additional light on Gödel's philosophical and scientific ideas and to show to what extent these ideas can be viewed as part of a unified philosophical outlook. Some of the arguments that led Gödel to Husserl's work are only hinted at in Gödel's 1961 paper, but they are developed in much more detail in Gödel's earlier philosophical papers (see especially 1934, *193?, 1944, 1947, *1951, *1953/59). In particular, I focus on arguments concerning Hilbert's program and an early version of Carnap's program.§1. Some ideas from phenomenology. Since Husserl's work is not generally known to mathematical logicians, it may be helpful to mention briefly a few details about his background.
Incompleteness, Mechanism, and Optimism
Authors: Shapiro Stewart 
Published: May 2006

§1. Overview. Philosophers and mathematicians have drawn lots of conclusions from Gödel's incompleteness theorems, and related results from mathematical logic. Languages, minds, and machines figure prominently in the discussion. Gödel's theorems surely tell us something about these important matters. But what?A descriptive title for this paper would be “Gödel, Lucas, Penrose, Turing, Feferman, Dummett, mechanism, optimism, reflection, and indefinite extensibility”. Adding “God and the Devil” would probably be redundant. Despite the breath-taking, whirlwind tour, I have the modest aim of forging connections between different parts of this literature and clearing up some confusions, together with the less modest aim of not introducing any more confusions.I propose to focus on three spheres within the literature on incompleteness. The first, and primary, one concerns arguments that Gödel's theorem refutes the mechanistic thesis that the human mind is, or can be accurately modeled as, a digital computer or a Turing machine. The most famous instance is the much reprinted J. R. Lucas [18]. To summarize, suppose that a mechanist provides plans for a machine,M, and claims that the output ofMconsists of all and only the arithmetic truths that a human (like Lucas), or the totality of human mathematicians, will ever or can ever know. We assume that the output ofMis consistent.
Tarski's System of Geometry
Authors: Tarski Alfred , Givant Steven 
Published: May 2006

AbstractThis paper is an edited form of a letter written by the two authors (in the name of Tarski) to Wolfram Schwabhäuser around 1978. It contains extended remarks about Tarski's system of foundations for Euclidean geometry, in particular its distinctive features, its historical evolution, the history of specific axioms, the questions of independence of axioms and primitive notions, and versions of the system suitable for the development of 1-dimensional geometry.
Church's Problem Revisited
Authors: Kupferman Orna , Vardi Moshe Y. 
Published: May 2006

AbstractIn program synthesis, we transform a specification into a system that is guaranteed to satisfy the specification. When the system is open, then at each moment it reads input signals and writes output signals, which depend on the input signals and the history of the computation so far. The specification considers all possible input sequences. Thus, if the specification is linear, it should hold in every computation generated by the interaction, and if the specification is branching, it should hold in the tree that embodies all possible input sequences.Often, the system cannot read all the input signals generated by its environment. For example, in a distributed setting, it might be that each process can read input signals of only part of the underlying processes. Then, we should transform a specification into a system whose output depends only on the readable parts of the input signals and the history of the computation. This is called synthesis with incomplete information. In this work we solve the problem of synthesis with incomplete information in its full generality. We consider linear and branching settings with complete and incomplete information. We claim that alternation is a suitable and helpful mechanism for coping with incomplete information. Using alternating tree automata, we show that incomplete information does not make the synthesis problem more complex, in both the linear and the branching paradigm. In particular, we prove that independently of the presence of incomplete information, the synthesis problems for CTL and CTL*. are complete for EXPTIME and 2EXPTIME, respectively.
Gap Forcing: Generalizing the Lévy-Solovay Theorem
Authors: Hamkins Joel David 
Published: May 2006

AbstractThe Lévy-Solovay Theorem[8] limits the kind of large cardinal embeddings that can exist in a small forcing extension. Here I announce a generalization of this theorem to a broad new class of forcing notions. One consequence is that many of the forcing iterations most commonly found in the large cardinal literature create no new weakly compact cardinals, measurable cardinals, strong cardinals, Woodin cardinals, strongly compact cardinals, supercompact cardinals, almost huge cardinals, huge cardinals, and so on.