bluuebunny/crossref_metadata_2025 huggingface dataset:
Activation of presynaptic A1‐receptors by endogenous adenosine inhibits acetylcholine release in the guinea‐pig ileum
Authors: Lee J. J. , Talubmook C. , Parsons M. E.
Published: March 2003

1 It is well established that presynaptic adenosine A1‐receptor activation inhibits acetylcholine (ACh) release in the guinea‐pig ileum. The present study extends this observation and examines a possible role for endogenous adenosine in modulating cholinergic nerve function.

2 The actions of the adenosine uptake blocker, dipyridamole, the adenosine deaminase inhibitor, erythro‐9(2‐hydroxy‐3‐nonyl)adenine (EHNA) and the A1‐receptor antagonist, 1,3‐dipropyl‐8‐cyclopentylxanthine (DPCPX) were examined on electrically evoked neurogenic, cholinergic twitch contractions of the guinea‐pig ileum. Some additional studies measuring [3H]‐ACh release were also performed.

3 Adenosine and the selective A1‐receptor agonist, 2‐chloroadenosine (2‐CA), inhibited electrically evoked contractions and, in the case of 2‐CA, [3H]‐ACh release. The actions were antagonized by DPCPX. At low concentrations, dipyridamole and EHNA enhanced the effect of adenosine causing a leftward shift of the concentration–response curve. In contrast, inhibition induced by 2‐CA was unaffected by either dipyridamole or EHNA.

4 When applied alone at higher concentrations, EHNA and dipyridamole produced a concentration‐dependent suppression of cholinergic neurotransmission. In both cases, the effect could be reversed by DPCPX. At the same concentration, DPCPX alone produced a small but consistent increase in twitch height and [3H]‐ACh release.

5 The data confirm the existence of inhibitory presynaptic adenosine A1‐receptors modulating cholinergic nerve function in the guinea‐pig ileum and suggests that these receptors can be activated by endogenous adenosine released either as adenosine itself or as an ATP metabolite.
A preliminary analysis of distribution patterns in a large, pantropical genus, Barleria L. (Acanthaceae)
Authors: Balkwill M. ‐J , Balkwill K
Published: March 2003

Barleria L. (Acanthaceae) is a large, polymorphic, widespread genus of herbs and shrubs comprising about 300 species, occurring mainly in Africa and Asia but with one species, Barleria oenotheroides Dum.Cours., extending to the New World tropics. Recent completion of a monographic infra‐generic classification of the genus (in which seven sections are recognised, and the names of four of these validated in this paper—see Appendix 1), has facilitated a comprehensive analysis of distribution patterns on a global scale. The richest representation of Barleria is in Africa where there are two centres of diversity, one in tropical East Africa (about eighty species) and the other in southern Africa (about seventy species). The number of species tails off rapidly to both the Far East and the West. Barleria shows a marked trans‐Atlantic disjunction between West Africa and the Neotropics, with B. oenotheroides shared by these two regions. This type of disjunction, which is known in other genera of the family, cannot be adequately explained in Barleria on the basis of long‐distance dispersal or past continental movements. There is a high degree of regional endemism (e.g. 75% for the Indian subcontinent) at both the species and sectional levels within this genus. The degree of similarity between regions is correspondingly low. The endemics in each region tend to belong to only one or a few of the sections. There are few truly widespread taxa within the genus. East and West Africa are the only regions in which all sections are represented. Sections Barleria and Prionitis C.B. Cl. are the most widespread in the genus; Sections Somalia (Oliv.) Lindau, Fissimura M. Balkwill and Stellatohirtae M. Balkwill are mainly restricted to Africa and Sections Chrysothrix M. Balkwill and Cavirostrata M. Balkwill are the most restricted, occurring mainly in India and Sri Lanka. On a local scale, many of the species show highly restricted, clumped distributions; this is apparently related to particular soil types and possibly to the short‐distance, ballistic mode of seed dispersal. This account of the biogeography of Barleria is to be regarded as preliminary, as much taxonomic work at the species level remains to be done before a full‐scale cladistic biogeographic account can be undertaken. Particular areas worthy of future investigation include establishing the centre of origin of the genus and investigating the basis for the high degree of endemism shown by many of the species.
A numerical analysis of the mesoscale distribution patterns of vascular plants in the subarctic Kevo Nature Reserve, northern Finland
Authors: Heikkinen Risto , Birks H. J. B , Kalliola Risto
Published: March 2003

Different numerical techniques were used to detect and describe the major ecological‐biogeographical patterns of vascular plant distributions at the meso‐scale level in a subarctic region in Finland. The distribution patterns of 231 native taxa in 362 1 km2 grid squares of the Kevo Nature Reserve were analysed by two‐way indicator species analysis and detrended correspondence analysis, and were subsequently related to twenty‐eight geographical, topographical, geological, and vegetational variables using simple discriminant functions and canonical correspondence analysis with associated Monte Carlo permutation tests.

The floristic variation detected reflects variations in environmental factors operative at the regional and local scales. No major broad‐scale coherent geographical patterns were detected; instead, the spatial distribution of the grids with a similar floristic composition shows a scattered distribution. All the numerical techniques reveal a major gradient from alpine areas to lowland sites with rivers and rocky outcrops, and the most important explanatory variables for predicting the main floristic variation are all associated with altitude. The floristic patterns represented by the second ordination gradient mainly correlate with the abundance of mires. Partial ordinations indicate that both the geographical and geological variables explain relatively little of the species distributional patterns.

Although the meso‐scale approach reveals much about the plant‐environment relationships in the study area, the floristic variation appears to be determined mainly by fine‐scale factors. In the most heterogeneous grids, the grid size used fails to detect accurately the ecological patterns of the species present.
Co‐occurrence of species with various geographical ranges, and correlation between area size and number of species in geographical scale
Authors: Ya. Vilenkin B , Chikatunov V. I
Published: March 2003

Co‐occurrence of species of various geographical ranges is important to correct endemism evaluation. This co‐occurrence is shown as non‐hazardous. Influence of area size on species richness is assumed to be different with respect to endemic and non‐endemic species. The territory of Israel and Sinai is subdivided into twenty biotic provinces. We segregated three hundred and twenty‐five tenebrionid species inhabiting this territory into endemic, regional and ubiquitous species. Regression of the number of endemic species on the number of regional species is non‐linear. Two distinct regression lines correspond to hot and cool areas. The number of ubiquitous species depends positively on numbers of both endemic and regional species, and negatively on their product. Ubiquitous species are predominantly synanthropic, and inability to tolerate competition with other tenebrionids is assumed as the basis of numerical relationships with other species. Correlation between numbers of endemic and non‐endemic species of bird and mammal and size of area is analysed at the broad geographical scale. Relationships between area size evaluation and the numbers of endemic and non‐endemic species are always different. The square root of the area km2 is always more important in species richness determination than area itself. This variable is a linear characteristic of the area and its significance is discussed. Possible ecological interactions between species of various geographical ranges are also considered. A new method of evaluation of the level of faunal endemism is proposed.
Corticolous lichens as potential bioindicators of fire history: a study in thecerradoof the Distrito Federal, central Brazil
Authors: Mistry Jayalaxshmi
Published: March 2003

Abstract.The aim of this study was to investigate the potential use of epiphytic corticolous lichens as indicators of fire history in thecerrado(savannas) of central Brazil. Work was carried out at the Reserva Ecológica do IBGE and the Jardim Botânico de Brasilia, 33 km outside Brasilia D.F., in ten plots ofcerrado densowithin the ‘Fire Project’ area. Each plot was subjected to a specific prescribed burning regime, with study sites varying from a plot protected from fire for over 20 years to a plot burned every 2 years. Research was carried out in two stages: (1) a preliminary survey of plots with different fire histories, measuring variables about the lichen habitat and the lichen communities present in the habitats; (2) lichen sampling in plots with different fire histories, where collection and identification of lichen species took place. Field techniques used included plotless sampling, and identification of lichens was carried out using taxonomic keys, both in the field and in the laboratory. The results show that fire is a major determinant of epiphytic corticolous lichen communities incerrado densovegetation. The abundance, distribution and recolonization of lichen communities can clearly be correlated with the frequency and behaviour, in terms of homogeneity and flame heights, of the fires that have occurred in each of the plots surveyed. Particular lichen species also show differential sensitivities to fire frequency and behaviour. This study shows that responses of corticolous lichens, at both the community and species level, can be used as bioindicators of fire history in areas ofcerrado densovegetation in central Brazil.
The historical biogeography of sturgeons (Osteichthyes: Acipenseridae): a synthesis of phylogenetics, palaeontology and palaeogeography
Authors: Choudhury Anindo , Dick Terry A.
Published: March 2003

Abstract. The historical biogeography of sturgeons is explored using information from palaeogeography, palaeontology and phylogenetic interrelationships. The integration of information from these diverse sources indicates that sturgeons reached a wide Laurasian distribution in the Cretaceous and Tertiary by freshwater and coastal dispersal routes across land connections and along newly forming continental margins. The fossil record also suggests a considerable degree of morphological stasis and also supports an estuarine habit, and perhaps diadromy, as an old and conserved life history trait. While a ‘centre of origin’ for sturgeons remains elusive, phylogenetic relationships indicate that diversification appears to have been associated with fragmentation of biota, and of landmasses and basins, by late Tertiary geological and climatic phenomena, such as orogeny and unequal glaciation over North America, the desiccation of central Asia and alteration of its drainages, and the formation of discrete Ponto‐Caspian basins by the fragmentation of the Paratethys. Amphi‐oceanic distributions of certain species (Acipenser medirostris Ayres) and sister taxa (e.g. A. oxyrhynchus Mitchill and A. sturio L.) are explained by coastal dispersal and subsequent vicariance by geological (sea‐floor spreading and development of new continental margins) and climatic (Pliocene cooling) changes during the Tertiary. An hypothesis is developed for the relationships of the North American sturgeons and their potential relationships with the Siberian sturgeon A. baeri. Late Tertiary climatic and geological phenomena are hypothesized as mediators of vicariance and subsequent diversification of these acipenserids. It appears that although acipenserids are a geologically old group, the historical biogeography of surviving lineages is best explained by more recent geological and climatic changes.
Oaks, acorns, and the geographical ecology of acorn woodpeckers
Authors: Koenig Walter D. , Haydock Joseph
Published: March 2003

We investigated the geographical ecology of acorn woodpeckers (Melanerpes formicivorus) using 30 years of Audubon Christmas Bird Counts and data on the diversity and abundance of oaks. Spatial autocorrelation in acorn woodpecker population densities is not significantly greater than zero both in either the southwestern United States, where populations are often locally isolated, or along the Pacific Coast, where they are more evenly distributed. In both regions, the effective distributional limit of acorn woodpeckers is set not by the limits of oaks but by sites where oak diversity drops to a single species. This result is consistent with acorn production patterns in central coastal California demonstrating that variability in overall acorn production and the probability of acorn crop failure decline with increasing oak species number but drop most markedly when two, compared to one, species of oaks are present together. Along the Pacific Coast, acorn woodpecker densities increase and population variability decreases with increasing abundance and diversity of oaks; however, analyses indicate that overall population size in this region is primarily determined by resource abundance while population stability is determined by resource diversity. Comparable patterns are not obvious in the Southwest, where acorn woodpecker densities are much lower than along the Pacific Coast. This may be due to a combination of greater competition for resources and oak communities that differ both qualitatively and quantitatively in their productivity compared to those along the Pacific Coast.
Effects of data characteristics on the results of reserve selection algorithms
Authors: Pressey R. L. , Possingham H. P. , Logan V. S. , Day J. R. , Williams P. H.
Published: March 2003

We tested the effects of four data characteristics on the results of reserve selection algorithms. The data characteristics were nestedness of features (land types in this case), rarity of features, size variation of sites (potential reserves) and size of data sets (numbers of sites and features). We manipulated data sets to produce three levels, with replication, of each of these data characteristics while holding the other three characteristics constant. We then used an optimizing algorithm and three heuristic algorithms to select sites to solve several reservation problems. We measured efficiency as the number or total area of selected sites, indicating the relative cost of a reserve system. Higher nestedness increased the efficiency of all algorithms (reduced the total cost of new reserves). Higher rarity reduced the efficiency of all algorithms (increased the total cost of new reserves). More variation in site size increased the efficiency of all algorithms expressed in terms of total area of selected sites. We measured the suboptimality of heuristic algorithms as the percentage increase of their results over optimal (minimum possible) results. Suboptimality is a measure of the reliability of heuristics as indicative costing analyses. Higher rarity reduced the suboptimality of heuristics (increased their reliability) and there is some evidence that more size variation did the same for the total area of selected sites. We discuss the implications of these results for the use of reserve selection algorithms as indicative and real‐world planning tools.
Mid‐Holocene vegetation diversity in eastern Cumbria
Authors: Skinner C. , Brown A. G.
Published: March 2003

The concept of biodiversity can operate at several different ecological levels from that of the Global ecosystem to the genetic diversity of a single species. This paper focuses on the beta‐type diversity of vegetation communities at the intra and inter‐regional scale, using five mid‐Holocene (Neolithic) pollen diagrams from eastern Cumbria (c. 500 km2 centred on the Eden valley). The sites were selected in order to include the variation in both soil/rock type and altitude within the study area, ranging from the Eden valley and southern limestone plateau to the foothills and summits of the western edge of the Pennines. The local pollen component which is dominant in these small sites, is used to determine intra‐regional vegetation diversity for a time‐slice in the Neolithic. Simple statistical methods are used to compare sites and as a measure of intra‐regional vegetation‐type diversity. This is compared with estimates of the community diversity for the British Isles during the same period. The results suggest that the intra‐regional vegetation diversity is comparable to that of Northern England, and it is related to variation in both altitude and soil type. There are some differences, for example the steepness of the western face of the Pennines is probably responsible for a lack of the pine dominated zone, and pedological constraints probably prevented the full development of woodland on the limestone plateau at the south of the study area. The open landscape of the limestone plateau acted as a refuge for late glacial herbaceous taxa prior to their re‐expansion into the wider landscape after widespread deforestation and arable cultivation. The results have implications for both the mapping of past vegetation at the national scale and for landscape archaeology.
Altitudinal and latitudinal distribution of east Malagasy forest bird communities
Authors: Hawkins A. F. A.
Published: March 2003

Aim To describe variation in forest bird communities with altitude and latitude.

Location Eastern Madagascar.

Methods Extraction of data from forest bird inventories conducted in eastern Madagascar.

Results There is a strong decline in species richness with altitude, above about 1300 m. Below this altitude, species richness is about constant or declines slightly. Seventy‐eight percent of species occurring regularly in forest are absent from at least one of low, mid‐altitude or high altitude forest. Of eighty‐seven species occurring regularly in forest, only four or possibly five have latitudinally limited distributions, over a latitudinal range of over 1200 km. Three or possibly four are limited to the northern two‐thirds, and one appears to be at least much more common in the southern half.

Main conclusions Eastern Malagasy rain forest birds show previously unanalysed variation in altitudinal distribution. There is much less latitudinal variation. Species currently considered threatened are concentrated in the lowland and high‐altitude zones. This may be at least partly due to lack of survey effort giving the impression that these species are rare, but lowland forests at least are under great human pressure. Bird conservation initiatives would probably have most effect if targeted at lowland east Malagasy rain forest.
Habitat associations of parrots on the Wallacean islands of Buru, Seram and Sumba
Authors: Marsden Stuart , Fielding Alan
Published: March 2003

Aim To investigate patterns of habitat use in nineteen populations of parrots on three Wallacean islands, and examine the degree to which habitats used by a species can be predicted across islands.

Location The Wallacean islands on Buru, Seram and Sumba.

Methods A logistic regression method was used to relate the presence/absence of parrot species at census plots to vegetation axes derived from ‘gross’ habitat parameters such as altitude, tree sizes, and percentages of vegetation coverage at different strata. Receiver Operating Characteristic Plots were then used to test predictions of habitat use by conspecific populations on the nearby and distant islands, and by different parrot species on the same island.

Results Parrots on Buru and nearby Seram tended to be associated with open‐canopied lowland forests, while on the distant and low‐lying island of Sumba, the preference was for closed‐canopy forests at higher altitudes. There were usually close affinities in habitat usage by conspecific populations on the two nearby islands. One exception was where the species occurred on the two islands as separate subspecies. Habitat preferences on Sumba, however, were so distinct that paradigms developed for Buru and Seram failed to predict distributions on this distant island.

Main conclusions For populations on more distant islands, it will usually be better to predict habitat use by considering the habitat used by other parrot species occurring on that island, than a conspecific population from another region. Conservation research programmes which concentrate parrot study on just one or two islands in every region of Wallacea may be more successful than those which ‘run through’ several islands in a group, but which miss out whole regions.
Brazilian Páramos I. An introduction to the physical environment and vegetation of the campos de altitude
Authors: DeForest Safford Hugh
Published: March 2003

Aim The campos de altitude are a series of cool‐humid, grass‐dominated formations restricted to the highest summits of the southeastern Brazilian Highlands. Relatively little is known of the ecology, biogeography, or developmental history of this archipelago of mountaintop formations. This contribution presents an overview of our present state of knowledge with respect to the past and present physical environment and vegetation of the campos de altitude. The aim is (1) to introduce an international audience to the natural history of these diminutive yet important ecosystems, and (2) to provide the background for a series of forthcoming contributions that will treat the ecology of the campos de altitude and explore physical and biotic relationships between these ‘Brazilian páramos’ and similar formations in the high mountains of equatorial South and Central America.

Location Beginning at altitudes of 1800–2000 m, the campos de altitude are found atop the highest summits of the main ranges of the southeastern Brazilian Highlands, between the states of Santa Catarina and Minas Gerais/Espírito Santo.

Methods Drawing upon both original data and previously published results, this contribution reviews what we presently know about the physical environment and vegetation of the campos de altitude, in the context of geographic setting, geology, palaeoclimatology and palaeobotany, modern climate, modern vegetation, and conservation.

Results and main conclusions Uplift of the southeastern Brazilian ranges to altitudes high enough to support orographic grasslands may have occurred as early as the middle‐ to late‐Tertiary; pollen records show that campos de altitude have been extant on southeastern summits at least since the Late Pleistocene. The present‐day climate of the campos de altitude is cool and (per)humid, but patterns of rainfall, temperature, and frost are distinctly seasonal. Although the flora of the campos de altitude is highly diverse and characterized by a high degree of endemism, the campos de altitude maintain strong floristic similarities to equatorial alpine formations of the Andean and Central American Cordillera; these similarities also extend to climate, soils, and vegetation physiognomy. Anthropogenic fires and grazing are widespread in the campos de altitude and probably contribute significantly to the modern structure of vegetation communities.
Distribution and ecology of myxomycetes in high‐latitude regions of the Northern Hemisphere
Authors: Stephenson Steven L. , Novozhilov Yuri K. , Schnittler Martin
Published: March 2003

Aim

The objective of this study was to analyse the data represented by 1976 specimens of myxomycetes collected in high‐latitude regions of the Northern Hemisphere to obtain information on the biogeographical relationships and patterns of occurrence of these organisms. The question of what factors limit myxomycete distribution in high‐latitude and cold‐dominated regions was also addressed.

Location

Specimens of myxomycetes considered herein were collected from twelve study areas in Iceland, northern Russia and Alaska, and Greenland. The vast majority of specimens were collected during the period of 1989–98.

Methods

Nine hundred and thirty‐three specimens were recorded as field collections. In addition, 1043 specimens originated from moist chamber cultures prepared with 1453 substratum samples collected in the various study areas. From a database recording the type of substratum (wood, bark of living trees, litter or dung) for each specimen, patterns of substratum occurrence for particular species of myxomycetes in high‐latitude regions were determined.

Results

From the 150 species recorded for the twelve study areas, thirty‐three were found to be widely distributed (recorded from at least five study areas), and only forty‐one had a frequency of occurrence higher than 1% either in moist chambers or as field collections. These data were examined in an effort to identify possible factors limiting the distribution of myxomycetes in high‐latitude regions.

Main conclusions

Upon first inspection, the arctic and subArctic myxomycete biota seems to be a depauperate version of that of temperate and boreal regions. However, a few species elsewhere recorded as rare but found to be fairly common in this study indicate that a certain degree of distinctiveness exists in Arctic and subArctic myxomycetes.
The voice of historical biogeography
Authors: Crisci Jorge V.
Published: March 2003

Historical biogeography is going through an extraordinary revolution concerning its foundations, basic concepts, methods, and relationships to other disciplines of comparative biology. There are external and internal forces that are shaping the present of historical biogeography. The external forces are: global tectonics as the dominant paradigm in geosciences, cladistics as the basic language of comparative biology and the biologist’s perception of biogeography. The internal forces are: the proliferation of competing articulations, recourse to philosophy and the debate over fundamentals. The importance of the geographical dimension of life’s diversity to any understanding of the history of life on earth is emphasized. Three different kinds of processes that modify the geographical spatial arrangement of the organisms are identified: extinction, dispersal and vicariance. Reconstructing past biogeographic events can be done from three different perspectives: (1) the distribution of individual groups (taxon biogeography) (2) areas of endemism (area biogeography), and (3) biotas (spatial homology). There are at least nine basic historical biogeographic approaches: centre of origin and dispersal, panbiogeography, phylogenetic biogeography, cladistic biogeography, phylogeography, parsimony analysis of endemicity, event‐based methods, ancestral areas, and experimental biogeography. These nine approaches contain at least 30 techniques (23 of them have been proposed in the last 14 years). The whole practice and philosophy of biogeography depend upon the development of a coherent and comprehensive conceptual framework for handling the distribution of organisms and events in space.
The Bering Strait connection: dispersal and speciation in boreal macroalgae
Authors: Lindstrom S. C.
Published: March 2003

A large number of boreal seaweeds have either sibling species or conspecific populations of a single species in the North Pacific and North Atlantic Oceans. This pattern is thought to have arisen from the dispersal between the two oceans through the Arctic Ocean after the opening of the Bering Strait in the mid‐to‐late Miocene or earliest Pliocene and from subsequent vicariant speciation as the Arctic Ocean froze and Bering Strait closed intermittently during glacial periods. Recent molecular studies of species in all three major seaweed phyla reveal patterns of vicariance. However, a number of lines of evidence point to differences in origins of these clades; some appear to be Pacific in origin whereas others appear to be derived from Atlantic stock. Different origins can be explained by recent stratigraphic finds that push the first Cenozoic opening of the Bering Strait back from 3.1–4.1 to 4.8–7.4 Ma (million years ago). Northern hemisphere ocean circulation models suggest that water flow would have been from the North Atlantic–Arctic south through the Bering Strait prior to the closure of the Panamanian Isthmus c. 3.5 Ma in contrast to the northward flow from the Pacific into the Arctic and North Atlantic, which developed after the closing of the Isthmus. Despite these differences in timing of the two invasions, there are no significant differences in levels of relationships among species with a North Atlantic origin compared with species with a North Pacific origin based on currently available data. More work is required to understand vicariance in seaweeds, especially in deciphering when a speciation event has occurred.
Explanations of patterns of intertidal diversity at regional scales
Authors: Zacharias Mark A. , Roff John C.
Published: March 2003

Aim

To test the hypothesis that the abiotic variables of salinity, temperature and fetch could explain patterns of intertidal species richness at regional scales (100–1000 s of km).

Location

British Columbia, Canada.

Methods

Using a 180 station data set collected over 7° of latitude on bedrock shorelines, we used a combination of correlation, multiple regression and ordination to show that species richness was strongly related to fetch, salinity and temperature.

Results

Results are consistent with the expected outcomes from the stability‐time and intermediate disturbance hypotheses.

Main conclusions

Temperate intertidal environments are predominantly physically accomodated at regional scales. Implications for near‐shore conservation are that the conservation of outer coast environments protects more species in a given area than inner coast environments.
Spatial and temporal variation of fire regimes in a mixed conifer forest landscape, Southern Cascades, California, USA
Authors: Beaty R. Matthew , Taylor Alan H.
Published: March 2003

Aim

In this study, we evaluated the fire‐forest mosaic of a mixed conifer forest landscape by testing the hypothesis that pre‐fire suppression fire regime parameters vary with species composition (tree species), and environment (i.e. slope aspect, slope position, elevation).

Location

Our study was conducted in the 1587 ha Cub Creek Research Natural Area (CCRNA), Lassen National Forest, CA, USA.

Methods

We quantified the return interval, seasonal occurrence, size, rotation period, and severity of fires using dendroecology.

Results

Slope aspect, potential soil moisture, forest composition, and fire regime parameters in our study area co‐vary. Median composite and point fire return intervals (FRI) were longest on higher, cooler, more mesic, north‐facing (NF) slopes covered with white fir (Abies concolor), Douglas fir (Pseudotsuga menziesii)–white fir, and red fir (A. magnifica)–white fir forests, shortest on the dry, south‐facing (SF) slopes covered with ponderosa pine (Pinus ponderosa)–white fir forests and intermediate on west‐facing slopes dominated by white fir–sugar pine (P. lambertiana)–incense cedar (Libocedrus decurrens) forests. The spatial pattern for length of fire rotation (FR) was the same as that for FRI. Fires in CCRNA mixed conifer forests occurred mainly (90%) in the dormant season. Size of burns in CCRNA mixed conifer forests were generally small (mean=106 ha), however, during certain drought years widespread fires burned across fuel breaks and spread throughout the watershed. Fire severity was mainly high on upper slopes, low on lower slopes and moderate and low severity on middle slopes. Patterns of fire severity also varied with slope aspect. Fire frequency decreased dramatically in CCRNA after 1905.

Conclusions

In CCRNA, fire regime parameters [e.g. FRI, fire extent, FR, fire severity] varied widely with species composition, slope aspect and slope position. There was also temporal variation in fire extent with the most widespread fires occurring during drought years. The important contributions of topography and climate to variation in the fire regime indicates that exogenous factors play a key role in shaping the fire‐forest structure mosaic and that the fire‐forest structure mosaic is more variable, less predictable and less stable than previously thought. Finally, some characteristics of the fire regime (i.e. fire severity, season of burn) in CCRNA are different than those described for other mixed conifer forests and this suggests that there are geographical differences in mixed conifer fire regimes along the Pacific slope.
Post‐glacial vegetation migration in conterminous Montréal Lowlands, southern Québec
Authors: Muller Serge D. , Richard Pierre J.H.
Published: March 2003

Aim

This work examines the post‐glacial plant migration patterns at a regional scale.

Location

St Lawrence lowlands and adjacent highlands, southern Québec.

Methods

The post‐glacial plant dynamics in the St Lawrence lowlands are reconstructed based on fifteen pollen diagrams and seventy‐four radiocarbon dates.

Results

Migratory trends are shown for the first established plant formations (tundra, boreal forest and mixed forest), while the subsequent onset of deciduous forests shows no particular pattern.

Main conclusions

Several factors are involved in this contrasting behaviour. First, the palaeogeographical context, principally determined by the location of the ice sheet and Champlain Sea, played a major role during the initial stages. The Champlain Sea constituted a barrier to seed dissemination between the Appalachians and Laurentians, favouring the development of Populus instead of Picea in the latter region. Secondly, ecological processes partly determined differences in establishment between conifer‐dominated forests and deciduous forests. The former resulted from the successive onset of dominant species (Picea and Abies), while the deciduous forest stages resulted from domination shifts between already established taxa. Thirdly, physiographic traits explain local departures to the general migratory pattern. The major departure comprises of the onset of tundra, boreal forest and mixed forest on Monteregian hills (most of which constituted islands within Champlain Sea) before their establishment in Appalachians.
A comparison of δ13C ratios of surface soils in savannas and forests in Amazonia
Authors: Magnusson W. E. , Sanaiotti T. M. , Lima A. P. , Martinelli L. A. , Victoria R. L. , De Araújo M. C , Albernaz A. L.
Published: March 2003

Aim

To determine the relationship between stable carbon isotope ratios in surface soils and the present vegetation in Amazonian savannas.

Location

Areas in and around savannas in the Brazilian Amazonian States of Amazonas, Pará, Amapá, Roraima, Mato Grosso and Maranhão.

Methods

δ13C ratios were measured from surface (0–5 cm depth) soils in fifty‐two plots in savanna plots with different covers of trees, shrubs, and grasses, and in ten adjacent areas covered by forest.

Results

Soil δ13C ratios varied widely (–24.9 to –15.2‰) among and within savannas, but were distinguishable from δ13C ratios under forest (–30.3 to –27.3‰). One site close to forest with 38% tree cover, 44% shrub cover and 45% grass cover was distinguishable from both forest and savanna on Landsat TM5 images, and had a δ13C ratio of –26.7‰. Tree density (TD), basal area (BA) and cover differed strongly between savanna and forest areas. However, most savanna areas had soil organic matter with δ13C ratios closer to those of forest trees than C4 grasses.

Main conclusions

In Amazonia, soil δ13C values >–25‰ can be unequivocally attributed to savannas irrespective of depth. However, there is no precise relationship between tree or grass cover in savannas and surface‐soil δ13C values. This is partly because shrubs, as well as trees and grasses, contribute significantly to soil organic matter δ13C ratios, and partly because there is a stronger negative relationship between area of bare ground and cover of C4 grasses than between area of bare ground and cover of trees or shrubs. This means that the ratio of C3 to C4 plants tends to increase with a decrease in total cover. Areas with large amounts of open ground, may have a small proportion of grass cover relative to tree and shrub cover. Although we did not encounter any such places in this study, very harsh conditions could lead to desert‐like formations with little grass cover and soil organic‐matter δ13C ratios similar to forest areas.
Cladistic biogeography and the art of discovery
Authors: Ebach Malte C. , Humphries Christopher J.
Published: March 2003

Aims

Cladistic biogeography is about discovering geographical congruence. The agreement of several taxon‐area cladograms (TACs) rarely yields a perfect result. Areas may overlap, taxa may not be evenly distributed, and thus, ambiguity may be prevalent in the data. Ambiguity is incongruence and may be resolved by reducing paralogy and resolving potential information. Recently, several new approaches in cladistic biogeography [i.e. Brooks parsimony analysis (BPA), Assumption 0] interpret ambiguity as congruence. These methods are problematic, as they aregenerational. Methods constructed under thegenerationparadigm are flawed concepts that are immunized from falsifying evidence. A critique of modified BPA reveals that taking an evolutionary stance in biogeography leads to flaws in implementation.

Methods

Area cladistics is a new development in cladistic biogeography. Area cladistics adopts paralogy‐free subtree analysis using Assumption 2, to discover the relative positions of continents through time.

Results

Geographical congruence is the result of allopatric (geographical) speciation. Vicariance, dispersal and combinations of both, are recognized causes for allopatric speciation. Area cladistics highlights the concept that all these events occur in response to geological changes (e.g. continental drift) either directly, by geographical boundaries, or indirectly, at the level of ocean currents. Samples of chosen examples all respond to the geological process. The examples include Ordovician–Silurian and Lower Devonian trilobites to yield a general areagram which is a representational branching diagram that depicts the relationships of areas.

Main conclusion

Finding one common biogeographical pattern from several unrelated groups is a qualitative approach to interpret the positions of continental margins through time. Area cladistics is not a substitute for palaeomaps that are derived from palaeomagnetic data, but general areagrams adding to the body of knowledge that yields more precise interpretations of the earth's past.
Can landscape‐scale characteristics be used to predict plant invasions along rivers?
Authors: Campbell G. S. , Blackwell P. G. , Woodward F. I.
Published: March 2003

Aim

To determine whether the invasions of hydrochorus plants, that is those which can make use of rivers to transport their propagules, can be predicted using information derived at the landscape scale. This is desirable to avoid the need for the difficult to measure parameters required by detailed invasion models.

Methods

A model for plant propagule dispersal was developed that simulated both local dispersal (autochory) and aided dispersal along river corridors (hydrochory). This provided the simulated invasion behaviour that was to be predicted by the simple analytical method. This latter was based on readily available river network characteristics. The analytical summary was then tested for its ability to predict the results of a series of simulation experiments.

Results

Predicted dispersal rates derived from the analytical summary method were strongly correlated (R2 of 0.8941) to the mean seed displacement simulated by the plant dispersal model.

Main conclusion

The simple analytical summary of the river networks provides a good probabilistic description of the simulated invasion process. This means that readily available information might be able to be used to predict real invasions by alien plant species. This method should now be tested against observed invasions by alien plants.
Schizophrenia: a review of current research and thinking
Authors: COFFEY MICHAEL
Published: March 2003

• Schizophrenia is the major mental illness of our time and causes serious disturbances for those with the condition as well as using up significant proportions of scarce health resources.

• This paper reviews the recent literature on advances in classification, aetiology, epidemiology and treatments.

• Methodological problems encountered in researching this condition are discussed.

• Advances in treatments offered for this condition have improved outcomes but whether the patient receives these treatments may depend on what local services are prepared to offer.
Research in peri‐operative nursing care
Authors: LEINONEN TUIJA , LEINO‐KILPI HELENA
Published: March 2003

• This review analyses 97 research reports dealing with peri‐operative care which included patients. The literature review was done as the basis of a development project to measure the quality of intra‐operative nursing care from the patient's perspective.

• The pre‐operative phase provides information about the teaching, anxiety and stress of patients. Few sources dealt with the intra‐operative phase; there were a small amount of reports concerning concrete nursing activities (e.g. surgical position and warming the patient). The most information was available on the post‐operative phase, such as recovery, adaptation and the treatment of pain.

• Peri‐operative research is mainly concerned with the quality of nursing care, control of life and ambulatory surgery.

• The main defects of analysed studies can be characterized as follows: small samples and a single hospital, lack of definition of terms, theoretical ambiguity, short follow‐up times, anaesthetic or other drugs used during the care not mentioned in the report (especially in studies on pain and quality). Previously developed research tools had usually been well tested, but there was great variety in the testing of investigator‐constructed tools. There were also discrepancies in the evaluation of validity and reliability.

• Future research should especially deal with treatment of pain and anxiety, information and guidance given to patients, and the costs of surgical care; there is also a need for studies dealing with intra‐operative care from the patient's perspective. Although information is already available on the above mentioned topics, more detailed and comprehensive facts are still needed.
Ethical issues and their practical application in a psychological autopsy study of suicide
Authors: COOPER JAYNE
Published: March 2003

•The psychological autopsy research method provides detailed information about a suicide using various sources including, coroners' reports, medical records and information gathered from interviews with key informants.

•The purpose of this article is to discuss the ethical issues that arose when undertaking a psychological autopsy study in Manchester, UK. The sensitive nature of the research is discussed, in particular in relation to the participation of the close relatives and friends of the deceased.

•These issues, identified from the experiences of other researchers in this field and by conducting a study in Manchester, had implications for the research design and its application.

•The reactions of the informants who took part in the Manchester study are reported, and their comments should be used to refine future studies on sensitive topics. Their suggestions on their needs and the needs of the suicidal have implications for future health service provision.
Competency for nursing practice
Authors: Watkins Mary J.
Published: March 2003

• This article discusses the report of the United Kingdom Central Council for Nursing, Midwifery and Health Visiting (UKCC) Commission that was published in 1999.

• Problems identified with the previous Project 2000 model of diploma‐level nursing programmes are identified, including student criticisms of placement arrangements and the existence of both theory–practice and practice–theory gaps.

• The UKCC Commission’s recommendations for curricular revision are discussed, particularly in relation to clinical competence and how this should be defined and measured.

• The implications for who should supervise and assess students in clinical practice are also explored.

• The importance of preparing and assessing students for holistic individualized care which respects patients’ own beliefs, values and culture is emphasized.
‘Ventilator‐dependent’ children who spend prolonged periods of time in intensive care units when they no longer have a medical need or want to be there
Authors: Noyes Jane
Published: March 2003

• Children who are dependent on ventilators currently spend many months and in some cases years in intensive care units when they no longer have a medical need to be there.

• This article presents the views of 18 young ‘ventilator‐dependent’ people (and their parents) who experienced prolonged periods of time in intensive care units and compares their experiences with published literature.

• Findings strongly suggest that living in an intensive care unit is inappropriate and detrimental to health and well‐being.

• Recommendations are made regarding the need for alternative placements, appropriate nursing care, the review of funding and discharge management procedures, and upholding children’s rights.
Men making sense of their chest pain – niggles, doubts and denials
Authors: White Alan K. , Johnson Martin
Published: March 2003

• Participant observation was undertaken of the early admission period of 25 men admitted to hospital with acute chest pain, followed by in‐depth interviews of 10 of the men after discharge.

• Grounded theory methods were used in the analysis to develop a model of how the men came to interpret their experiences.

• An emerging feature of the men’s experiences was that, although they had suffered intense pain prior to admission, there had been a series of delays whilst they tried to rationalize their symptoms.

• We relate our discussion to literature on men and masculinity and the notion of Foucault (1975) of self‐surveillance, to offer an insight into the men’s self concept and social situation.

• Our conclusions suggest that men’s self concept as ‘healthy’ may inhibit a speedy response to the signs and symptoms of acute coronary occlusion, increasing the risk of cardiac arrest without nearby life support.
Informational needs about the effects of gynaecological cancer on sexuality: a review of the literature
Authors: Gamel Claudia , Hengeveld Michiel , Davis Bryn
Published: March 2003

• In order to develop a supportive and information‐giving intervention for women with gynaecological cancer, the effects of cancer on sexuality and the associated informational needs were reviewed.

• Pre‐diagnosis symptoms of gynaecological cancer which affect sexual function may resolve after treatment; these symptoms are often replaced by treatment‐associated effects on sexuality.

• Sexual dysfunction has been found even when women report regular intercourse and sexual satisfaction.

• Effects on sexuality seen at 6 months gradually resolve over time. However, women with cervical and ovarian cancer tend to attain better long‐term sexual function than those with vulvar and endometrial cancer.

• Specific sexuality information needs can be ascertained from the findings of qualitative studies in which the experience of sexuality, sexual adaptation and received information is described.

• Different sexuality information is needed at three time periods: diagnosis and treatment period; recovery and first intercourse; the period of rebuilding sexual life.

• The type of information and the time when it is needed are not necessarily the same for women and their partners.