bluuebunny/crossref_metadata_2025 huggingface dataset:
Early fire and forest change in the Baliem Valley, Irian Jaya, Indonesia
Authors: Hope Geoffrey
Published: March 2003

Abstract. A 3.5 m section of organic sediment was obtained from a karstic pond on a hill in the centre of the Baliem Valley, one of the major settled intermontane highland areas of New Guinea. The material spans two time periods each of approximately 2 millennia, one from about 2000 BP to the present and the other from 33,500 to 31,500 BP. The pollen analysis of the earlier section showed that it formed when the valley was forested by Nothofagus forest, but a carbonized particle input was consistently present after about 32,500 years ago. The recent section covers a period when the hill was totally cleared except for grassland and some open shrubby regrowth. The early burning and associated clearances are tentatively ascribed to a human origin. Fire is associated with slope erosion on the hill at 28,000 BP which supports the hypothesis of long term human settlement in the area.
Long‐term effects of daily grazing orbits on nutrient availability in Sahelian West Africa: I. Gradients in the chemical composition of rangeland soils and vegetation
Authors: Turner Matthew D.
Published: March 2003

Abstract. An investigation of the long‐term effects of livestock grazing on the spatial distribution of plant nutrients was conducted in the Sahelian region of West Africa. The study area was located along the transhumance corridor used for at least the past century by a long‐established population of agropastoralists in central Mali. Spatial variation of plant and soil chemistry across eighteen sites was investigated with respect to a grid, whose axes are defined by distance from a pan from which livestock disperse to graze primarily during the early dry season (D1) and by distance from the nearest of three pans used primarily during the rainy season (D2). Particle size distribution, pH, total C, N, and P of surface soil (0–10 cm) was determined for four composite samples collected at eleven of the eighteen ecological sites. Elemental analysis (N, P, Ca, Mg, K, Mn, Fe, Zn, Cu) was performed on above‐ground tissue samples (excluding seeds) of the three most common grasses and the most common legume collected at all eighteen sites at the end of the rainy season.

Results demonstrate that long‐term grazing movements can, over the long‐term, affect nutrient availability over wider spatial scales (5 km radii) than previously observed by shorter‐term studies. Soil and plant chemistry were found in general to be most affected by the historic gradient of cattle presence during the rainy season (D2). Controlling for soil C and coarse sand fraction, soil pH was found to decline with D2 (−0.5 pH units per km D2) and to a lesser extent D1 (−0.15pH units per km D1), a finding that cannot be explained solely by a consideration of local geomorphology. The pH gradient was found to significantly affect micronutrient concentrations in plant tissues. Phosphorus (P) concentrations of plant tissue were found to decrease with D2. The increase in P‐availability near rainy‐season encampments could result from P‐release from Al‐complexes at higher pH and/or by the redistribution of P from outlying zones towards rainy‐season encampments.
A vegetation map of Central Africa derived from satellite imagery
Authors: Mayaux Philippe , Richards Tim , Janodet Eve
Published: March 2003

Aim This paper presents the Joint Research Centre's TREES Project satellite derived Vegetation Map of Central Africa, at 1:5,000,000 scale, with a detailed description of the vegetation classes and their distribution. The information content of the map is compared with other conventional and satellite derived maps of the region for validation and evaluation purposes.

Location The map focuses on the Guineo‐Congolian ecological domain and covers the following countries: Cameroon, Central African Republic, Republic of Congo, Equatorial Guinea, Gabon and the Democratic Republic of Congo.

Methods Using coarse resolution satellite imagery a map of vegetation cover has been produced based upon the spectral response of the vegetation cover. Digital image processing and geographical information systems techniques were employed, together with local knowledge, high resolution imagery and expert consultation, to compile a cartographic map product.

Results The TREES Vegetation Map of Central Africa has been shown to be strongly correlated with the FAO Forest Resources Assessment for 1990. Comparison with other map sources indicates that the map contains greater spatial detail and is more consistent than conventionally compiled maps. The conventional maps however, contain more thematic information content relating to vegetation type.

Main conclusions The map improves our state of knowledge of the vegetation cover of Central Africa and presents the most consistent and spatially detailed view yet published at this scale. Thematic information content on forest type is limited but should be improved in the near future with the inclusion of data from new satellite sensors. This first version of the map and future planned updates should provide an important input for regional stratification and planning purposes for forest resources, biodiversity and climate studies.
The distance decay of similarity in biogeography and ecology
Authors: Nekola Jeffrey C. , White Peter S.
Published: March 2003

AimOur aim was to understand how similarity changes with distance in biological communities, to use the distance decay perspective as quantitative technique to describe biogeographic pattern, and to explore whether growth form, dispersal type, rarity, or support affected the rate of distance decay in similarity.

LocationNorth American spruce‐fir forests, Appalachian montane spruce‐fir forests.

MethodsWe estimated rates of distance decay through regression of log‐transformed compositional similarity against distance for pairwise comparisons of thirty‐four white spruce plots and twenty‐six black spruce plots distributed from eastern Canada to Alaska, six regional floras along the crest of the Appalachians, and six regional floras along the east–west extent of the boreal forest.

ResultsSimilarity decreased significantly with distance, with the most linear models relating the log of similarity to untransformed distance. The rate of similarity decay was 1.5–1.9 times higher for vascular plants than for bryophytes. The rate of distance decay was highest for berry‐fruited and nut‐bearing species (1.7 times higher than plumose‐seeded species and 1.9 times higher than microseeded/spore species) and 2.1 times higher for herbs than woody plants. There was no distance decay for rare species, while species of intermediate frequency had 2.0 times higher distance decay rates than common species. The rate of distance decay was 2.7 times higher for floras from the fragmented Appalachians than for floras from the contiguous boreal forest.

Main conclusionsThe distance decay of similarity can be caused by either a decrease in environmental similarity with distance (e.g. climatic gradients) or by limits to dispersal and niche width differences among taxa. Regardless of cause, the distance decay of similarity provides a simple descriptor of how biological diversity is distributed and therefore has consequences for conservation strategy.
The land use history (1278–1990) of a mixed hardwood forest in western Belgium and its relationship with chemical soil characteristics
Authors: Verheyen K. , Bossuyt B. , Hermy M. , Tack G.
Published: March 2003

Aim During the last decades, an increasing number of studies have stressed the importance of historical human influence on the ecology of forests and on the characteristics of forest soils. Therefore, the objectives of this study are (1) the quantification of the land use history of Ename Wood from 1278 to 1990 and (2) to find out whether the former land use of the forest has long‐lasting effects on present‐day chemical soil properties.

Location The 62‐ha present‐day Ename Wood is situated in western Belgium and is the remainder of the 145‐ha historical Ename Wood.

Methods We disposed of eighteen land‐use maps for the period between 1278 and 1990 which were digitized using a geographic information system (GIS). Transition between the different land uses and Shannon–Wiener diversity indices were calculated to quantify the history of changing land use. Mixed soil samples were taken in lots delimited on the basis of the historical data. Next, the soil properties were combined with the land‐use variables using redundancy analysis and
ANOVA.

Results The quantification of the land use changes showed that the present Ename Wood is the result of several forest regression and progression phases, with a complete clearance in the nineteenth century. Diversity in land use was maximal between the fourteenth and the sixteenth century due a variety of transitional forms between forest and pasture. A positive correlation between the duration of arable land use since the 19th century clearance and soil pH, calcium and phosphate content was observed and a negative correlation was found with the carbon content, the total nitrogen content and the C:N ratio. These correlations are probably caused by a combination of acidification processes and the accumulation of organic matter under forest in combination with manuring practices in the twentieth century. Present‐day forest lots which have been pastured for some time between 1278 and nineteenth‐century clearance still had a significantly lower pH and degree of base saturation, which is probably caused by the export of nutrient rich plant material at that time.

Discussion and conclusions The results demonstrate that the developed methodology is successful and confirm that historical land use, even in the distant past, can still influence present‐day soil characteristics. For this reason, long‐term historical land use should always be considered in forest ecological research.
Biogeography and ecology of freshwater diatoms in Subantarctica: a review
Authors: Van de Vijver Bart , Beyens Louis
Published: March 2003

Subantarctica is situated between the Antarctic and the Subtropical Convergence and consists of the islands in the southern Atlantic, Indian and Pacific Oceans. Diatoms are an important component of all Subantarctic aquatic, moss and soil habitats. Taxonomic studies reveal a high diversity and species richness in both the present‐day and the fossil diatom flora. Planktonic diatoms are almost completely absent. A similarity analysis of the diatom composition from different localities in the southern zone (below 40°S) resulted in a biogeographical zonation. Three regions could be formed, based on their diatom composition: Subantarctica, Maritime Antarctica and the Antarctic Continent. The diatom communities in the different regions are all characterized by a high proportion of cosmopolitan species. A second feature of the southern diatom floras is the decreasing diversity when moving southwards.
Floristic analysis of vascular plant genera of North America north of Mexico: characteristics of phytogeography
Authors: Qian Hong
Published: March 2003

The phytogeographical characteristics of North America north of Mexico (NANM) were examined based on an analysis of the 1904 indigenous genera of the vascular plants known to the area. According to the worldwide distribution patterns of the genera, the 1904 genera were grouped into ten phytogeographical elements (categories). About 67.3% of the genera found in the native flora of NANM also occur in other areas of the world; of these, 71.4% occur in the Old World. About 32.7% of the 1904 genera are endemic to North America. The origins of the floristic relationships between North America and the rest of the world and the origin of the present‐day flora of North America are discussed. The current floristic patterns of the NANM vascular plant genera resulted in part from palaeogeological events such as the unification of tectonic plates into a single supercontinent, Pangaea, and then the breakup of the united supercontinent into Laurasia and Gondwana followed by the fragmentation of Laurasia and Gondwana into individual continents as they are today due to the movement of plate tectonics. Many of the endemic genera of North America likely originated in the North American continent during the Tertiary, particularly during the uplifting of Rocky Mountains.
Fire regimes and forest changes in mid and upper montane forests of the southern Cascades, Lassen Volcanic National Park, California, U.S.A.
Authors: Taylor A. H.
Published: March 2003

Aim Spatial and temporal variation in fire regime parameters and forest structure were assessed.

Location A 2630‐ha area of mid‐ and upper montane forest in Lassen Volcanic National Park (LVNP).

Methods Two hypotheses were tested concerned with fire‐vegetation relationships in southern Cascades forests: (1) fire regime parameters (return interval, season of burn, fire size, rotation period) vary by forest dominant, elevation and slope aspect; and (2) fire exclusion since 1905 has caused forest structural and compositional changes in both mid‐ and upper montane forests. The implications of the study for national park management are also discussed.

Results Fire regime parameters varied by forest compositional group and elevation in LVNP. Median composite and point fire return intervals were shorter in low elevation Jeffrey pine (Pinus jeffreyi) (JP) (4–6 years, 16 years) and Jeffrey pine–white fir (Abies concolor) (JP‐WF) (5–10 years, 22 years) and longer in high elevation red fir (Abies magnifica)— western white pine (Pinus monticola) (RF‐WWP) forests (9–27 years, 70 years). Median fire return intervals were also shorter on east‐facing (6–9 years, 16.3 years) and longer on south‐ (11 years, 32.5 years) and west‐facing slopes (22–28 years, 54‐years) in all forests and in each forest composition group. Spatial patterns in fire rotation length were the same as those for fire return intervals. More growing season fires also occurred in JP (33.1%) and JP‐WF (17.5%) than in RF‐WWP (1.1%) forests. A dramatic decline in fire frequency occurred in all forests after 1905.

Conclusions Changes in forest structure and composition occurred in both mid‐ and upper montane forests due to twentieth‐century fire exclusion. Forest density increased in JP and JP‐WF forests and white fir increased in JP‐WF forests and is now replacing Jeffrey pine. Forest density only increased in some RF‐WWP stands, but not others. Resource managers restoring fire to these now denser forests need to burn larger areas if fire is going to play its pre‐settlement role in montane forest dynamics.
Altitudinal zonation of Andean cryptogam communities
Authors: Kessler Michael
Published: March 2003

To test whether cryptogamic plant communities in tropical Andean rain forests are distributed in floristically discrete communities corresponding to altitudinal belts, I subjected the elevational distribution of pteridophytes along two elevational gradients in Bolivia, and of bryophytes and lichens along two transects in Peru and Colombia (data from Gradstein & Frahm, 1987;
Wolf, 1993) to an analysis of deviance. All well‐defined elevational boundaries in floristic composition were related to marked ecological changes: the transition from the steep mountains to the hilly lowland zone coupled with a change in geological substrate at 400 m along the Bolivian Carrasco transect, a strong humidity gradient at 1000 m at the Bolivian Masicurí transect and at 1250–1980 m along the Colombian transect, and the transition from mixed cloud forests to forests dominated by Polylepis or Podocarpus at 3400–3600 m in Carrasco, at 1650–1800 m in Masicurí, and at 3670 m in Colombia. Consequently, floristic elevational belts appear to be well‐defined at strong environmental boundaries and in fairly species‐poor forest communities where the presence or absence of one or a few tree species influences the whole ecosystem while they are ill‐defined in species‐rich communities such as tropical forests at low to mid‐elevations.
The relationship between cave biodiversity and available habitat
Authors: Christman Mary C. , Culver David C.
Published: March 2003

Aim

The goal of this study was to determine the role habitat availability plays in the distribution of obligate subterranean cave fauna in eastern North America.

Location

The numbers of stygobites, troglobites and caves in the counties of the south‐eastern USA were analysed.

Methods

The data were characterized by large numbers of zeroes and by spatial clustering of non‐zeroes in five regions. Regression and conditional autoregressive (CAR) models were used to elucidate the patterns and relationships between numbers of species and numbers of caves both locally and regionally.

Results

Local effects (regions and numbers of caves in counties) accounted for 45% of the variation in troglobite counts (P=< 0.001) and 24% of the variation in stygobite counts (P=< 0.001). Significant spatial autocorrelation among both stygobites and troglobites (P=< 0.0001) was found as well.

Conclusion

Overall, habitat availability as measured by cave numbers influenced species richness. Spatial and regional effects also played an important role in determining the observed distributions of the subterranean fauna. Terrestrial and aquatic communities showed very different patterns in their relationship to habitat and within the different regions.
Comparison of methods to estimate historic species richness of mammals for tests of faunal relaxation in Canadian parks
Authors: Wiersma Yolanda F. , Nudds Thomas D.
Published: March 2003

Aim

Some recent tests of faunal change in reserves have relied on, but been limited to, estimates of species richness from random samples of historic range maps. We evaluated a different, Geographic Information Systems (GIS)‐based, approach to count species directly, as the latter method might facilitate rapid estimation of historic species richness as well as composition for samples of the same size, shape and exact location as present‐day reserves.

Location

National parks throughout Canada.

Methods

Geographic Information System.

Results

The GIS‐based method tended to count, in exact locations of modern parks, fewer species (on average, seven disturbance intolerant and five disturbance tolerant) present historically than extrapolated from randomly sampled sites, but the differences were not greater than expected by chance. However, correlations between number of species lost and park size were weaker than reported previously, suggesting a greater potential for other factors to influence a change in species richness (and composition) than inferred earlier.

Main conclusions

Direct counts of historic range maps using GIS tools provided a quick means to estimate site‐specific historic species richness not statistically different from estimates produced by random sampling. As well, the GIS‐based method could yield data about historic species composition for the specific location and size of modern reserves, which may be more ecologically meaningful in terms of assessing what factors may have contributed to the observed species losses.
Halffter’s Mexican Transition Zone, beetle generalized tracks, and geographical homology
Authors: Morrone Juan J. , Márquez Juan
Published: March 2003

Aim

Halffter’s Mexican Transition Zone is a complex area in which the Neotropical and Nearctic regions overlap. We test its existence and extension through a track analysis of beetle taxa, and discuss the implications of geographical homology.

Location

The area analysed corresponds to the Caribbean subregion, which occupies Mexico, Central America, north‐western South America, and the Western Indies.

Methods

The panbiogeographic or track analysis was based in the comparison of 134 individual tracks belonging to different beetle taxa (species and supraspecific groups). A Parsimony Analysis of Endemicity (PAE) was applied in order to classify the areas by their shared taxa according to the most parsimonious cladogram, and the nested sets of areas were represented as generalized tracks.

Results

Two generalized tracks resulted: (1) northern generalized track: comprising the Sierra Madre Occidental, Sierra Madre Oriental, Transmexican Volcanic Belt, Balsas Basin and Sierra Madre del Sur biogeographic provinces; and (2) southern generalized track: comprising the Chiapas, Mexican Gulf, Mexican Pacific Coast and western Panamanian Isthmus biogeographic provinces.

Main conclusions

The generalized tracks obtained correspond broadly to Halffter’s Nearctic and Mesoamerican patterns, respectively; however, in contrast to Halffter’s Mesoamerican pattern, the southern generalized track extends further north through the lowlands of the Pacific and Mexican Gulf coasts.
Biogeography of the Antilles based on a parsimony analysis of orchid distributions
Authors: Trejo‐Torres J. Carlos , Ackerman James D.
Published: March 2003

Aim

We obtain biogeographical patterns based on the distributions of shared orchid species of the Caribbean. These patterns are used to define biogeographical zones. We then analyse the concordance between the distributional patterns with ecological and physical features of the islands.

Location

We use orchid species recorded on 49 islands of the Greater, Lesser, and southern Antilles, and the Bahamas. Three continental areas are included: Florida (North America), the Yucatan (Central America), and the Guianas (South America).

Methods

We use a parsimonious analysis of species distributions that produces the best arrangements of shared taxa among areas. The analysis uses 356 shared orchid species of the 863 species recorded for studied areas. The methodology has been used to infer historical relationships among areas but we interpret the results as static or ecological patterns of biogeographical affinities.

Results

Two kinds of island groupings are revealed. (1) Groups with common geology and geomorphology: the Bahama Archipelago, the Virgin Islands, the Cayman Islands and the southern Dutch Antilles. (2) An aggregation of distant islands with a heterogeneous geology but a common physiography: the Greater Antilles/Trinidad/Lesser Antilles/Margarita‐Tobago. The Guianas are linked with the Greater Antilles, while the Yucatan and Florida are linked to the Bahamas.

Main conclusions

Groupings of islands are congruent with their gross ecological features either from similar geomorphology or common physiography. The strong affinity among islands considerably distant among each other is explained by the high vagility of dust‐seeded orchids. Then, floristic affinities seem determined by ecological characteristics of islands rather than by dispersal barriers. We predict that other plant groups with dust‐like diaspores and animals with good vagility should show comparable biogeographic patterns. Parsimony analysis of distributions (PAD) is an alternative methodology to multivariate analysis to compare biotas, and a graphic complement to quantitative methods producing numerical values.
Biogeography of Australian freshwater fishes
Authors: Unmack Peter J.
Published: March 2003

Aim

To investigate biogeographic patterns of obligate freshwater fishes.

Location

Australia.

Methods

Similarity indices, parsimony analysis, and drainage‐based plots of species’ ranges were used to identify patterns.

Results

Relationships among regions were deduced largely by concordance between methodologies, then summarized into a proposed series of faunal provinces.

Main conclusions

The most striking pattern was in the incidence of endemism across the continent. Provinces in southern, central, and western Australia have high numbers of endemic fishes, presumably resulting from isolation by aridity and drainage divides. With exception of one region, northern and eastern Australia provinces have few endemics, probably explained in the north by high drainage connectivity during times of lowered sea levels. This does not account for low endemism in the east because drainages appear to have remained isolated during lowered sea levels and patterns suggest an absence of distinct barriers of other kinds. By default, climate again seems the most probable cause of species’ distributional limits. Whatever the case, most patterns were almost certainly established in the distant past, perhaps as early as Miocene. Influences of Plio–Pleistocene events on broad patterns of freshwater fish distributions seem minimal.
Rarity, specialization and extinction in primates
Authors: Harcourt A. H. , Coppeto S. A. , Parks S. A.
Published: March 2003

Aim

To determine and explain biological traits that distinguish rare from common primate taxa.

Location

Africa, Americas, Asia, Madagascar.

Methods

We compare the biology of rare primate taxa with the biology of common taxa. Rarity is defined by (1) small size of geographic range; (2) small geographic range plus low local population density; and (3) small geographic range plus low local density plus narrow habitat specificity. After a linear comparison of size of geographic range with various biological traits, globally and by realm, extremes of rarity and commonness per realm are identified, and then combined for a global analysis. Tests are done both with genera treated as independent data points (n=62), and also with phylogenetic control by use of an independent contrasts test. Extinction risk in vertebrates, including primates, often correlates with high resource requirements, slow population recovery rate, and specialization. The three indices of rarity are therefore compared with these three general traits. Measures of resource use are body mass, local density, annual range size, and group size; of recovery rate, interbirth interval, and maximum intrinsic rate of natural population increase; and of degree of specialization, variety of diet, of habitats, maximum latitude, and morphological variety. All data come from the literature. Because several measures are compared, probabilities are Bonferroni corrected.

Results

If rarity in primates correlates with any biological attribute, it consistently correlates with only measures of specialization, and not with measures of high resource use, or slow population recovery rate. Without phylogenetic correction, the first two indices of rarity associate significantly with all four measures of specialization, and the third with maximum latitude. With phylogenetic correction, the first index still associates with all four, the second with two (maximum latitude, number of species per genus), and the third shows no significant associations. While the four measures of specialization are strongly interrelated, stepwise regressions on geographic range indicate that maximum latitude has the strongest effect, followed by dietary variety and number of species per genus and, finally, habitat variety.

Main conclusions

The most commonly demonstrated traits of susceptibility to extinction are those of high resource use, slow recovery rate, and specialization. Yet, while rarity (almost however, it is defined) is an inevitable precursor to extinction, specialization is the only trait found to correlate with rarity in this study. We cannot explain this apparent contradiction.
Moving to suburbia: ontogenetic and evolutionary consequences of life on predator‐free islands
Authors: Blumstein Daniel T.
Published: March 2003

Aim

Many species find themselves isolated from the predators with which they evolved. This situation commonly occurs with island biota, and is similar to moving from the dangerous inner‐city to the suburbs. Economic thinking tells us that we should expect costly antipredator behaviour to be lost if it is no longer beneficial. The loss of antipredator behaviour has important consequences for those seeking to translocate or reintroduce individuals from predator‐free islands back to the predator‐rich mainland, but we have neither a detailed understanding of the mechanisms of loss nor information on the time course of relaxed selection. Some antipredator behaviours are experience‐dependent: experience with predators is required for their proper performance. In these cases, antipredator behaviour is lost after only a single generation of isolation, but it should be able to be regained following exposure to predators. Other behaviours may be more `hard‐wired'. The evolutionary loss of antipredator behaviour may occur over as few as several generations, but behaviours may also persist for many thousands of years of predator‐free living.

Location

Australia and New Zealand.

Methods

I discuss the results of a series of studies designed to document the mechanisms and time course of relaxed selection for antipredator behaviour in macropodid marsupials. Controlled studies of visual, acoustic and olfactory predator recognition, as well as field studies of antipredator vigilance focused on several species of kangaroos and wallabies.

Results

Visual predator recognition may be retained following 9500 years of relaxed selection, but olfactory and acoustic predator recognition may have to be learned. Insular populations allow humans to approach closer before fleeing than mainland animals. Insular species may retain `group size effects' – the ability to seek safety in numbers – when they are exposed to any predators.

Main conclusions

I suggest that the presence of any predators may be an important factor in maintaining functional antipredator behaviour. Managers should pay particular attention as to the source and evolutionary history of their population when planning translocations or reintroductions.
Boreal tree taxa in the central Scandes during the Late‐Glacial: implications for Late‐Quaternary forest history
Authors: Kullman Leif
Published: March 2003

Aim

This paper seeks to elucidate the first post‐glacial arrival of tree species to high elevations in the Scandes. This enables testing of general theories concerning glacial refugia, immigration routes and palaeoclimate.

Location

The study site, 1360 m a.s.l., was close to the summit of Mt Åreskutan in the alpine region of the southern Swedish Scandes, 400–500 m above modern tree‐limits.

Methods

Tree megafossils (trunks, roots, cones) were retrieved (and radiocarbon‐dated) from the ground surface in the forefields of receding `perennial' snow‐patches. This approach allows elevational range‐margin reconstructions to be made with an accuracy not possible with any other method.

Results and conclusions

Megafossils were recovered substantially higher and earlier than previously recorded or inferred for tree growth in this part of Europe. The species were Betula pubescens Ehrh. ssp. tortuosa (Ledeb.) Nyman, Picea abies (L.) Karst. and Pinus sylvestris (L.). The oldest dates obtained are c. 14,000, 11,000 and 11,700 BP for these species, respectively. For the first time, explicit evidence of tree growth in the Late‐Glacial (including the Younger Dryas stadial) is demonstrated for central/northern Scandinavia. The swift appearance of boreal tree species at high northern latitudes and altitudes on the western fringe of Scandinavia and near the most extended margin of the Weichselian ice sheet hypothetically suggests that the first immigration of the trees considered here was from the west. Glacial refugia for these species (other plants and animals as well) on the exposed continental shelf areas west and southwest of Norway is hypothesized. By extension, the results fit into a more general pattern, suggesting the presence of boreal and temperate trees quite close to the full glacial (Weichselian) ice margins in central Europe. Thus, the Quaternary forest and landscape history of Europe seems more complex than previously believed.
Physiographical and historical effects on forest vegetation in central New England, USA
Authors: Gerhardt Fritz , Foster David R.
Published: March 2003

Aim  Land‐use history can be an important determinant of ecosystem characteristics, even in landscapes that outwardly appear ‘natural’. In New England, like much of the eastern United States, the natural reforestation of agricultural lands over the past 150 years has created a predominantly forested landscape. Understanding the physiographical and historical factors controlling forest structure and composition is a major challenge to ecologists, conservationists and land managers.

Location  We studied the forest structure and composition of Petersham, Massachusetts, which is located in the Central Upland physiographical province of New England. Like much of New England, Petersham was largely cleared for agriculture by the mid‐1800s, but most of the agricultural fields were abandoned and naturally reforested in the late‐1800s and early 1900s. The modern landscape is > 90% forested by a mosaic of primary and secondary woodlands.

Methods  At seventy‐four randomly selected 0.04‐ha plots, we measured the abundances of all vascular plants in the overstory and understory and nine physiographical and historical variables.

Results  Species richness was primarily related to landform: species‐rich communities occurred in poorly drained basins and species‐poor communities occurred on well‐drained glacial outwash. Distributions of the sixty‐nine most common species were associated with (in order of importance) landform, past land use and elevation. Many species were restricted to specific physiographical conditions, but no species were restricted to specific past land uses. Nine plant associations identified by two‐way indicator species analysis were associated with elevation, landform, soil texture and past land use. Ordination by canonical correspondence analysis indicated that the vegetation reflected two principal gradients: a physiographical gradient, defined by landform and soil texture, and a land‐use gradient.

Main conclusions  These analyses suggest the following ranking of factors controlling forest structure and composition in this landscape at this time: landform > agricultural history > elevation > hurricane = fire = logging. Even in this physically heterogenous landscape, land‐use history continues to play an important role in shaping forest vegetation 100–150 years after agricultural abandonment and reforestation.
Chestnut: history and ecology of a transformed species
Authors: Paillet Frederick L.
Published: March 2003

Abstract Aim  The character and distribution of American chestnut (Castanea dentata) populations in New England are analysed to identify the extent to which the introduced chestnut blight and historic land use practices have affected chestnut distribution and life history.

Location  The study focuses on chestnut in Connecticut and Massachusetts but includes analysis of data related to other Castanea species in North America and Europe.

Methods  The ecology and palaeoecology of chestnut is investigated using a range of techniques, including examination of the growth form of chestnut trees in plantations located away from blight, mapping of chestnut sprouts and blight‐killed trees at various locations, anatomical examination of chestnut stems, analysis of early forestry practices, identification of changes in the relative abundance of chestnut pollen in Holocene lake sediments and comparison of American chestnut with other Castanea species.

Results  Examination of chestnut sprouts surviving in the former range of that species shows that most sprouts originated from suppressed seedlings and that environmental factors severely limited the survival of sprouts from large blight‐killed trees. Palynological data show that chestnut was either present in very low populations or entirely absent from New England and only became abundant after about 2500 years ago. All factors suggest that chestnut abundance is related to the natural disturbance cycle, while human‐induced transformations of the landscape and the introduction of chestnut blight have further transformed the character of chestnut in New England.

Main conclusions  Most surviving chestnut sprouts in New England forests represent old seedlings that have continued to re‐sprout since establishment before the introduction of blight nearly 100 years ago. The growth form of these sprouts ensures a minimal substrate of bark tissue for blight establishment so that blight has a relatively minor effect on seedling–sprout survival. The identification of modern chestnut sprouts as old seedlings indicates that the observed distribution of sprouts in New England woodlands is strongly influenced by land use conditions and especially field abandonment at the time when chestnut blight arrived from its point of introduction.
Three hundred years of forest and land‐use change in Massachusetts, USA
Authors: Hall Brian , Motzkin Glenn , Foster David R. , Syfert Mindy , Burk John
Published: March 2003

Abstract Aim  The aim of this study was to document changes in forest composition, structure and distribution across Massachusetts, USA, from the time of European settlement (seventeenth century) to the present, and to investigate environmental and historical influences on regional patterns of variation.

Location  The study area encompasses the State of Massachusetts (69.9–73.5°E, 41.3–42.9°N), a 21,000‐km2 area in the north‐eastern United States.

Methods  A wide range of historical sources was used to document changes in land use and land cover for the historical period. Witness trees from early land surveys enabled us to evaluate vegetation patterns prior to widespread European settlement, and to compare historical and modern species composition. Nineteenth century maps of forest cover and contemporary agricultural censuses documented forest patterns during the peak agricultural period. Geographic Information System analyses were used to relate variation in climate, geology and land‐use history to historical and modern forest composition.

Results  Massachusetts has a complex east‐to‐west environmental gradient involving changes in physiography, climate, geology and natural disturbance. Until the middle of the twentieth century, agriculture was the most important land‐use across the region; although the percentage of land in agriculture and the timing of major land‐use changes were remarkably consistent across the state, historical forest patch sizes varied locally and regionally in relation to physiography. Forest composition of both early historical and modern forests is most strongly related to environmental conditions, especially variation in climate. Historical land‐use resulted in a state‐wide increase in early successional tree species and a dramatic, although recovering, change in forest structure.

Main conclusions  At a regional scale, environmental conditions apparently control broad patterns of variation in vegetation composition. Historical land‐use practices were relatively homogenous across Massachusetts and local variation was reduced through data averaging at broad spatial scales. At finer spatial scales, historical land‐use has strong and persistent impacts on vegetation composition and structure.
Vegetation variation across Cape Cod, Massachusetts: environmental and historical determinants
Authors: Motzkin Glenn , Eberhardt Robert , Hall Brian , Foster David R. , Harrod Jonathan , MacDonald Dana
Published: March 2003

AbstractAim We evaluate environmental and historical determinants of modern species composition for upland vegetation types across Cape Cod, Massachusetts, a region that supports numerous uncommon species assemblages that are conservation priorities.

Location The study area encompasses the entire peninsula of Cape Cod, Massachusetts, USA.

Methods Historical changes in land‐use and land‐cover across the study region were determined from historical maps and documentary sources. Modern vegetation and soils were sampled and land‐use and fire history determined for 352 stratified‐random study plots. Ordination and classification were used to assess vegetation variation, andG‐tests of independence and Kruskal–Wallis tests were used to evaluate relationships among individual species distributions, past land‐use, surficial landforms and edaphic conditions.

Results At the scale of this investigation, modern species distributions result from individualistic response to a range of environmental and historical factors, including geography, substrate and disturbance history, especially the pattern of past agricultural activity. The structure or composition of all vegetation types in the region have been shaped by past land‐use, fire, or other disturbances, and vegetation patterns will continue to change through time. Conservation efforts aimed at maintaining early successional vegetation types may require intensive management comparable in intensity to the historical disturbances that allowed for their widespread development.
Latitude, seed predation and seed mass
Authors: Moles A. T. , Westoby M.
Published: March 2003

Aim We set out to test the hypothesis that rates of pre‐ and post‐dispersal seed predation would be higher towards the tropics, across a broad range of species from around the world. We also aimed to quantify the slope and predictive power of the relationship between seed mass and latitude both within and across species.

Methods Seed mass, pre‐dispersal seed predation and post‐dispersal seed removal data were compiled from the literature. Wherever possible, these data were combined with information regarding the latitude at which the data were collected. Analyses were performed using both cross‐species and phylogenetic regressions.

Results Contrary to expectations, we found no significant relationship between seed predation and latitude (log10proportion of seeds surviving predispersal seed predation vs. latitude,P= 0.63;R2 = 0.02;n= 122 species: log10proportion of seeds remaining after postdispersal seed removal vs. latitude,P= 0.54;R2 = 0.02;n= 205 species). These relationships remained non‐significant after variation because of seed mass was accounted for. We also found a very substantial (R2 = 0.21) relationship between seed mass and latitude across 2706 species, with seed mass being significantly higher towards the tropics. Within‐species seed mass decline with latitude was significant, but only about two‐sevenths, as rapid as the cross‐species decline with latitude. Results of phylogenetic analyses were very similar to cross‐species analyses. We also demonstrated a positive relationship between seed mass and development time across ten species from dry sclerophyll woodland in Sydney (P < 0.001;R2 = 0.77; Standardized Major Axis slope = 0.14). These data lend support to the hypothesis that growing period might affect the maximum attainable seed mass in a given environment.

Main conclusions There was no evidence that seed predation is higher towards the tropics. The strong relationship between seed mass and latitude shown here had been observed in previous studies, but had not previously been quantified at a global scale. There was a tenfold reduction in mean seed mass for everyc. 23° moved towards the poles, despite a wide range of seed mass within each latitude.
Primary plant succession on recently deglaciated terrain in the Canadian High Arctic
Authors: Jones Glenda A. , Henry Greg H. R.
Published: March 2003

Aim  Primary succession in a high arctic environment was examined to determine whether the patterns conform to models based on studies in temperate regions. The location also presented an unique opportunity to examine a well preserved pre‐Little Ice Age plant community and organically enriched palaeosol that are being released from the glacier along with the glacial and glaciofluvial sediments.

Locations  The main location was the recently deglaciated terrain of the Twin Glacier foreland at Alexandra Fjord, Ellesmere Island (79° N). The position of the glacier from air photos in 1959 and 1981, and periodic direct monitoring of the position of the terminus since 1980 provided good chronological control. Surveys of succession patterns were also conducted at four other sites in the Alexandra Fiord region of eastern central Ellesmere Island.

Methods  Vegetation cover of mosses and vascular plants (lichens were not present) was measured in 1994 and 1995 using a stratified random design. twinspan and canonical correspondence analysis were used together to examine successional vegetation patterns in relation to a set of environmental variables. Species richness, total vegetation cover, and a combined set of soil parameters (pH, organic matter content, moisture and fine substrate) were compared between the two principal soil types, palaeosol and glaciofluvial sediment.

Results  Terrain age accounted for most of the variation in species composition over the study area. The succession followed a directional‐replacement series with four main stages of dominance in at least 44 years: (1) mosses → (2) graminoid‐forb → (3) deciduous shrub‐moss → (4) evergreen dwarf‐shrub‐moss. There was little difference in species richness patterns over time on the palaeosol compared with the glaciofluvial sediment. However, total vegetation cover was significantly higher on palaeosol and there was a significant difference in a combined set of soil parameters between the two soil types, which indicates that palaeosol may provide conditions more favourable for establishment and growth.

Main conclusions  Directional‐replacement succession is possible in a high arctic oasis environment; however, this mode of succession is probably atypical of much more extensive high arctic environments such as polar deserts. Descriptive results from four other glacier forelands sampled in 1995 on east‐central Ellesmere Island showed directional succession with no species replacement at two sites and non‐directional succession without species replacement at another site. Primary succession in these high arctic sites is strongly controlled by local environmental conditions.
Sign reading: making sense of what is going on in the ward
Authors: WAKEFIELD ANN
Published: March 2003

• When entering a ward the environment observed can be perceived in one of two ways: either from the perspective of `background', this being the backdrop against which events take place, or as the main focus of attention, thereby alerting the observer to what is going on in the setting.

• Whilst undertaking their work nurses emit signs which patients, relatives and other staff interpret and through which they gain an understanding of the type of work about to be undertaken at the clinical interface.

• The themes of private work, showdown work and tragic plight work, which were generated from an observational study in a surgical ward, are discussed in this article.

• Findings show that, despite nurses attempts to hide the gravity of a message from patients, they in fact give more away than they hide.
Evidence‐based practice: a retrograde step? The importance of pluralism in evidence generation for the practice of health care
Authors: CLARKE JANICE B.
Published: March 2003

• The origin of evidence‐based medicine is explored and its connection to evidence‐based practice examined.

• Widespread acceptance of the dominant scientific paradigm supporting evidence‐based practice is challenged.

• Knowledge classifications and their relevance for nursing practice are considered, with the need for a critical balance to be pursued.

• Recommendations are made, regarding the future of evidence for practice, and a brief example of emerging evidence concerning values of professional caring is offered in redressing the balance.