bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Market Economy in the Early Roman Empire
Authors: Temin Peter 
Published: May 2006

The economy of the early Roman Empire has been an object of study for at least the last century. The discussion has been marked by continuing debate, known sometimes as the primitivist/modern debate and at other times as the Finley debate, following his famous Sather lectures, The Ancient Economy. This paper is a contribution to this debate, written by an economist rather than an ancient historian. My purpose is to define the concept of a ‘market economy’, and to see if it fits the evidence we have for the early Roman Empire.Finley declared that, ‘ancient society did not have an economic system which was an enormous conglomeration of interdependent markets’. He drew implicitly on research by Polanyi to oppose the views of Rostovtzeff within the field of ancient history and those of Fogel and Engerman in economic history, but he did not explicitly join their conceptual apparatuses. Morris has summarized the debate fuelled by Finley's dramatic lectures in his foreword to the twenty-fifth anniversary edition and argued that the controversy is still vigorous today. I hope to clarify the issues in this debate and even resolve the debate for the period of the early Roman Empire.
Plant species associations in alpine‐subnival vegetation patches in the Central Caucasus
Authors: Kikvidze Zaal 
Published: May 2006

Abstract. Patches of herbaceous vegetation found at the boundary of the alpine and subnival belts in the Central Caucasus (3000 m) were analysed for species composition, interspecific associations, as well as for relations between age, size and diversity of the patches. 34 plant species were recorded. Positive and negative associations were found among the most frequent species. A model is presented that describes the cumulation of species in patches during succession. In the final and stable successional stage, the maximum number of species within a patch was nine.Species composition varies in patches of different age, typical alpine species being more frequent in older ones. The results are interpreted as evidence for niche differentiation and selection of species composition through the 'sieve’ of interspecific relations, taking place during succession in the studied patches.
Vegetation types of the deltaic Mediterranean coast of Egypt and their environment
Authors: Zahran M. A. , El‐Demerdash M. A. , Mashaly I. A. 
Published: May 2006

Abstract. The delta section of the Mediterranean coast of Egypt canbe divided ecologically into four main habitats: salt marsh, sand formation, reed swamp and fertile non‐cultivated land. In each habitat vegetation types can be distinguished based on the dominance of single species. The salt marsh habitat comprises five such communities dominatedby: Zygophyllumaegyptium, inula crithmoides, Arthrocnemum macrostachyum, Juncus acutus and Ha‐locnemum strobilaceum. The vegetation of the sand formation includes 11 communities dominatedby: Elymus farctus ssp.farctus, Alhagigraecorum, Cynodon dactylon, Heliotropium curassavicum, Stipagrostis lanata, Thyme‐laea hirsuta, Moltkiopsis ciliata, Asparagus stipularis and Pancratium maritimum (sand dunes), Cressa crética and Phragmites australis (sand flats). The reed swamp habitat is dominated by Typha domingensis. In the fertile non‐cultivatedlandAlhagigraecorum, Cynodon dactylon and Heliotropium curassavicum are the dominants.Quantitative cluster analysis revealed a lower number of clusters than there are dominance types, but on the whole the two systems are similar.Ordination and subsequent analysis of correlation between vegetation gradients and soilfactors showed that the decisive soil factors for the variation in salt marsh vegetation are moisture availability and CaC03 content, and for the sand formation soil moisture, ‐ fertility and ‐ salinity.
A vegetation zonation from saltmarsh to riverbank in New Zealand
Authors: King Warren McG. , Wilson J. Bastow , Sykes Martin T. 
Published: May 2006

Abstract. Brackish riverbank marshes have been little studied. Therefore, a plant community sequence was sampled from saltmarsh to near‐freshwater riverbank marsh on a number of disjunct marshes along the Taieri River, Otago, New Zealand, from near the mouth to 9 km inland. Salinity decreased steadily upstream, though the actual values were very different on two days sampled.Ten communities are recognised. The major vegetation zonation was upshore more than upstream, though there were several interactions between the upshore and upstream gradients. Few species, if any, were restricted to the mid reaches of the length of river sampled. There was only a very slight upshore increase in species richness, and no trend upstream.Sequences of communities occurred upshore on all marshes, but the sequence differed, even within a marsh. Species were assorted into communities in different ways from those of marine marshes in the area. Some species, native and exotic, occupied different beta‐niches from those they occupied in other countries. Individualistic community structure is inferred.
Population ecology of Acacia tortilis in the semi‐arid region of the Sudan
Authors: Kennenni Legesse , van der Maarel Eddy 
Published: May 2006

Abstract. The population ecology of Acacia tortilis, one of the important woody species in the arid and semi‐arid regions of northern Africa, was studied in the Sudan: Ten sample plots were established and all individuals in the plots were mapped and their basal diameter, stem height, crown height and cover measured annually for three years. Individuals were grouped into different height‐classes, ‘life‐forms’: trees >1.65 m, shrubs > 0.65 m and < 1.65 m, saplings < 0.65 m and seedlings (saplings less than one year old). The population density was 510 ind./ ha in 1985, 432 ind. / ha in 1986 and 218 ind. / ha in 1987. The life‐form distribution of the population showed clear differences between plots and years.Mortality in Acacia tortilis, expressed as loss in individuals per year, amounted to 167 ind. / ha / yr. Drought and lethal cutting were found to be the main mortality factors. The population declined by 15.3 % from 1985 to 1986 and by 49.5 % from 1986 to 1987.Natality (recruitment), expressed as number of newly established saplings, was 13 ind. / ha / yr. Recruitment is apparently discontinuous and bound to years with a relatively high precipitation.
A hierarchical set of models for species response analysis
Authors: Huisman J. , Olff H. , Fresco L.F.M. 
Published: May 2006

AbstractVariation in the abundance of species in space and/or time can be caused by a wide range of underlying processes. Before such causes can be analysed we need simple mathematical models which can describe the observed response patterns. For this purpose a hierarchical set of models is presented. These models are applicable to positive data with an upper bound, like relative frequencies and percentages. The models are fitted to the observations by means of logistic and non‐linear regression techniques. Working with models of increasing complexity allows us to choose for the simplest possible model which sufficiently explains the observed pattern. The models are particularly suited for description of responses in time or over major environmental gradients. Deviations from these temporal or spatial trends may be statistically ascribed to, for example, climatic fluctuations or small‐scale spatial heterogeneity. The applicability of this approach is illustrated by examples from recent research. A combination of simple, descriptive models like those presented in this paper and causal models as developed by several others, is advocated as a powerful tool towards a fuller understanding of the dynamics and patterns of vegetational change.
An 11400 year paleoecological history of a British chalk grassland
Authors: Bush M. B. 
Published: May 2006

AbstractThe first broad‐based, paleoecological analysis of a sedimentary sequence on the British chalk, dating to the terminal Pleistocene, reveals a history of climatic, vegetational and faunal change. The past co‐occurrence of currently allopatric species among molluscs, beetles and plants supports hypotheses of the impermanence of communities. Modern pollen rain data are utilized to refine the ecological interpretation of the fossil pollen data.The presence of the Windermere Interstadial (Allerod) and the Loch Lomond re‐advance (Younger Dryas) are represented by decreased abundances of arboreal taxa and increased representation of cold grassland elements. Open grassland habitats appear to have been a continuous landscape element, at least locally, since the late‐glacial period on the northern British chal Mands, although their species composition has changed greatly in the last 11400 yr.
Vegetation establishment in post‐fire Adenostoma chaparral in relation to fine‐scale pattern in fire intensity and soil nutrients
Authors: Rice S. K. 
Published: May 2006

AbstractAt fine spatial scales (0.1–10m), chaparral communities have been shown to be strongly influenced by canopy‐gap patterns, leading to periodicities in vegetation at 4–5 m spatial scales. Fine‐scale variations in fire behavior and post‐fire erosion can lead to changes in the patterning of viable seeds and nutrients and may alter the spatial patterning of post‐fire chaparral communities. This study deals with the relationship among fire behavior, post‐fire nutrient availabilities and vegetation patterns in a 1‐yr old, post‐fire Adenostoma fasciculatum chaparral community in the Sierra Nevada Mountains, California, USA. Variations in mineral soil exchangeable cations (Ca, Mg) and extractable phosphorus (P04‐P) were correlated with ash distribution. Cations and measures of ammonium and nitrate were also correlated with fire intensity, measured by the diameter of the smallest remaining A. fasciculatum twigs following fire. Fire intensity was correlated with the pattern of post‐fire vegetation establishment based on first axis DC A scores. However, ash PO4‐P was more highly correlated with sample DCA scores, local species richness and total cover (p < 0.01), suggesting that small‐scale variations in PO4‐P which correlate with ash distributions may be important in structuring this community.Two‐ and three‐term local variance analysis revealed a maximum of pattern intensity in DCA first axis scores at 4–5 m intervals that likely corresponds to pre‐fire canopy‐gap patterns. However, total cover showed pattern at spatial scales of 8–10 m, and was correlated at this scale with patterns of ash distribution and fire intensity. Microtopographic patterns also occur at similar spatial scales. Microtopographic patterns appear important in determining post‐fire plant nutrient and water distributions and, thereby, patterns of plant establishment. Thus, the scale and intensity of post‐fire vegetation pattern may differ considerably from pre‐fire conditions.
Fire and other variables as determinants of forest/fynbos boundaries in the Cape Province
Authors: Manders P. T. 
Published: May 2006

Abstract.Forests in the southwestern Cape are restricted to sheltered stream banks and patches of rock scree owing to protection from recurrent fire and the more favourable soil moisture conditions in these habitats. The effects of a prescribed burn on 17 March 1987 on the forest / fynbos boundaries in the Swartboskloof catchment are described. No evidence of erosion of the forest edge was recorded, although this could be ascribed to the low intensity of the fire.Soil properties, primarily pH and aluminium and available phosphorus levels, differed markedly between forest and fynbos. It is argued, however, that this is a result, not a cause of vegetation change. Light extinction levels and soil moisture availability after the fire were lower in the fynbos than in the forest, and are considered to preclude incursions of forest species into fynbos of a low post‐fire age.
Seed dispersal spectra: a comparison of temperate plant communities
Authors: Willson Mary F. , Rice B. L. , Westoby M. 
Published: May 2006

Abstract. We compare the dispersal spectra of diaspores from varied plant communities in Australia, New Zealand, and North America, assigning dispersal mode to each diaspore type on the basis of apparent morphological adaptations. Species with ballistic and external dispersal modes were uncommon in most communities we surveyed. Ant dispersal was also rather uncommon, except in some Australian sclerophyll vegetation types. The frequency of vertebrate dispersal ranged up to 60% of the flora, the highest frequencies occurring in New Zealand forests. Wind dispersal ranged as high as 70% of the flora, with the highest values in Alaska, but usually comprised 10–30% of the flora. Many species in most communities had diaspores with no special morphological device for dispersal. Physiognomically similar vegetation types indifferentbiogeographic regions usually had somewhat dissimilar dispersal spectra. The frequency of dispersal by vertebrates often increased and the frequency of species with no special dispersal device decreased along gradients of increasing vertical diversity of vegetation structure. Elevation and moisture gradients also exhibited shifts in dispersal spectra. Within Australia, vertebrate‐ and wind‐dispersal increased in frequency along a soil‐fertility gradient, and dispersal by ants and by no special device decreased. Habitat breadths (across plant communities) and microhabitat breadths (within communities) for species of each major dispersal type did not show consistent differences, in general. Ant‐dispersed species often had lower cover‐values than other species in several Australian vegetation types.We discuss the ecological bases of these differences in dispersal spectra in terms of the availability of dispersal agents, seed size, and other ecological constraints. Seed size is suggested to be one ecological factor that is probably of general relevance to the evolution of dispersal syndromes.
BOOK REVIEWS
Authors: Monson Russell K. 
Published: May 2006

Book reviewed in this issue.Lambers, H., Cambridge, M. L., Konigs, H. & Pons, T. L. (eds.) 1989. Causes and Consequences of Variation in Growth Rate and Productivity of Higher Plants, x + 354 pp. SPB Academic Publishing, The Hague. ISBN 90–5103–033–9. Price: USD 90.00.
Importance of the soil seed bank of disturbed sites in Chilean matorral in early secondary succession
Authors: Jiménez Héctor E. , Armesto Juan J. 
Published: May 2006

Abstract. The dynamics of the seed bank may provide clues to the process of recovery of the vegetation of disturbed sites. The role of the seed bank may be more important in areas with a seasonal climate than in areas where seedling recruitment is not limited to one season. We studied the seed bank and the seed rain in three sites of the Chilean mediterranean‐climate region (33° 48'S) which differed in the degree of anthropic disturbance: a closed‐canopy, second‐growth forest; an open matorral; and an old‐field. Additionally, we tested the germination of seeds from the soil and from the current‐year seed crop. The seed bank varied considerably between the two years of study, although no change in the vegetation could be observed. Seed density and species richness were lower in 1989 than in 1988. The seed bank of the second‐growth forest changed less between years, while the old‐field showed the largest change. The highest seed rain occurred under shrub patches in the open matorral, while few seeds fell in the spaces between shrub clumps or in the old‐field. In the forest, seed rain was low and correlated with species cover. Germination was low (0 ‐ 15%) in tests using either soil samples or fresh seeds.These results indicate that matorral succession is a very slow process, limited mainly by low germination and low arrival of propagules to open areas. Most woody species have animal‐disseminated fleshy propagules. The presence of established shrubs which may serve as perches or refuges for animals increases species richness in the seed rain and the seed bank.
Changes in prairie vegetation under elevated carbon dioxide levels and two soil moisture regimes
Authors: Nie D. , Kirkham M. B. , Ballou L. K. , Lawlor D. J. , Kanemasu E. T. 
Published: May 2006

Abstract. It is important to know how increasing levels of atmospheric CO2 will affect native vegetation. The objective of this study was to determine the effect of elevated CO2 concentrations on species composition in a tallgrass prairie kept at a high water level (730 mm of water in a 2000 mm soil profile) and a low water level (660 mm of water in 2000 mm). 16 cylindrical plastic chambers were placed on the prairie to maintain two levels of CO2 (ambient or twice ambient) during two growing seasons in 1989 and 1990. Frequency of species was determined on 25 July 1989 and on 5 and 10 October 1990.At the beginning of the study, Poa pratensis (Kentucky bluegrass), the dominant C3 species, had the highest frequency of 43.3%, but decreased with time. However, at the end of the experiment and under the high soil‐water level, there were more P. pratensis plants in the elevated CO2 treatment (frequency: 13.5%) than in the ambient CO2 treatment (1.0%). Under the low soil water regime, the reverse occurred (frequencies: 3.6% and 11.0% for high and low CO2, respectively).The frequency of major C4 plants, Andropogon gerardii (big bluestem), A. scoparius (little bluestem) and Sorghastrum nutans (Indian grass) was not affected by CO2. However, water did affect their frequency. Under low water, the frequency of A. gerardii decreased between 1989 and 1990. Under both soil moisture levels, the frequencies of S. nutans and A. scoparius increased. At the end of the study, Indian grass grown with high water had the highest frequency of all species on the prairie (frequency at the end of the study in October, 1990, of 44.4% and 47.4% for the high and low CO2 levels, respectively). Unlike Indian grass, little bluestem grew better under low water conditions than under high water conditions.These results suggest that, if the climate becomes drier, A. scoparius will flourish more than S. nutans or A. gerardii, and P. pratensis may die out. Elevated CO2 might not increase survival of C3 plants under dry conditions, if temperatures are too high for them.
Morphological analysis of herbaceous communities under different grazing regimes
Authors: Díaz S. , Acosta A. , Cabido M. 
Published: May 2006

Abstract. A methodology for the morphological analysis of herbaceous communities is presented, together with an example of its application in montane grasslands in the province of Córdoba (Argentina) subject to grazing and burning.The method, based on multivariate ordination and classification techniques, enabled the detection of morphological changes at three levels in response to disturbance: (a) characterization of the spatial structure of the vegetation; (b) identification of morphological plant groups; and (c) quantification of morphological shifts among different individuals of a single species.The architecture of the vegetation changed toward a progressive miniaturization of photosynthetic structures and concentration of biomass close to the ground, as disturbance intensity increased. Six morphological plant groups (modes of response) showing different behaviour in relation to competition for light and pressure from large herbivores were identified. Some species, highly preferred by ungulate grazers, showed high morphological variability among morphs growing in different grazing situations, whereas some others were morphologically uniform.
Fire and competition in Australian heath: a conceptual model and field investigations
Authors: Keith David A. , Bradstock Ross A. 
Published: May 2006

Abstract. We describe a model of heath vegetation, in which species were classified into five functional groups based on characteristics of their propagule pools, post‐fire growth, timing and mode of reproduction and competitive status. The model assumes no recruitment without fire and a simple competitive hierarchy based on vertical stature. A critical feature of the model is an initial post‐fire window of 5–6 yr in which competition from overstorey species on understorey species is reduced. Understorey functional groups differ in their ability to exploit this window.In the field, we tested five predictions derived from the model: (a) overall species richness of understorey varies inversely with overstorey density as a result of a trend in richness of woody species, but not in herbaceous species; (b) where an overstorey was present in the previous fire interval, post‐fire population density is reduced in a functional group of understorey serotinous resprouting shrubs, but not in a group of understorey obligate‐seeding shrubs with soil seed banks; (c) in understorey serotinous resprouting shrubs, post‐fire regrowth in resprouting individuals is adversely affected by the presence of an overstorey in the preceding fire interval; (d) in understorey serotinous resprouting shrubs, levels of pre‐fire propagules are lower in the presence of an overstorey, reducing the density of post‐fire recruits; and (e) in understorey serotinous resprouting shrubs, recruitment relative to the pre‐fire population is unaffected by overstorey species within the window of reduced competition. Of these, three tests (a,b,d) supported the model, one (e) may support the model, but the results were inconclusive and one (c) did not support the model.Limitations and further applications of the model are discussed. Our results suggest that maintenance of high densities of overstorey populations is in conflict with conservation of some understorey species. Models of the type we propose will help identify and resolve such conflicts and promote the judicious use of fire to maintain full species diversity of plant communities.
Suppression of annuals by Tribulus terrestris in an abandoned field in the sandy desert of Kuwait
Authors: El‐Ghareeb R. M. 
Published: May 2006

AbstractIn an abandoned field in the sandy desert of Kuwait annual plants were less numerous in stands dominated by Tribulus terrestris than in adjacent stands dominated by other species.In the Tribulus stands, annuals were smaller in phytomass and stature. Possible physical and biotic factors were investigated in both types of stands in order to determine the causative agent(s) for the lesser density and development of annuals in the Tribulus stands. Physical conditions of moisture, light and soil characteristics did not appear to be limiting to annuals in the Tribulus stands.Experimental evidence is presented for the leaching from T. terrestris shoots of water‐soluble substances which strongly inhibit the germination and radicle elongation of most of the associated annual species. The effect of these substances is fairly specific. Preliminary analysis indicates the presence of phenolic compounds in the leachate of T. terrestris, which are believed to play a significant role in the growth inhibition. The possible role of chemical inhibition on certain annuals in stands of T. terrestris is discussed.