Showing papers in "Journal of Biogeography in 1974"
720Â citations
TL;DR: In this article, regression analyses were computed for the prediction of island species numbers in the British Isles, using as independent variables island area, island elevation, the number of soil types, ON latitude, the distance from mainlanid Britain, distance from the nearest other island, and number of vegetation types, and latitudinal range.
Abstract: Regression analyses were computed for the prediction of island species numbers in the British Isles, using as independent variables island area, island elevation, the number of soil types, ON latitude, the distance from mainlanid Britain, the distance from the nearest other island, the number of vegetation types, and latitudinal range. In simple regressions, the number of island soil types was the best single predictor of island species number. In multiple regressions, area, ON latitude, and distance from Britain also made significant contributions to the prediction of island species numbers. These analyses are discussed in terms of the theory of island biogeography in general and the description of the British Isles in particular. The slope of the log species, log area curve reveals that the plant species distribution pattern on the British Isles is more like that of continents than of islands.
111Â citations
105Â citations
TL;DR: The patterns of distribution of vertebrates (primarily terrestrial forms) are analysed from the Silurian onwards, using palaeogeographical maps which show epicontinental seas as well as intercontinental oceans as discussed by the authors.
Abstract: The patterns of distribution of vertebrates (primarily terrestrial forms) are analysed from the Silurian onwards, using palaeogeographical maps which show epicontinental seas as well as intercontinental oceans. Silurian vertebrates (fish) are known almost exclusively from Euramerica. Many Devonian fish which are normally found in fresh waters seem to have been able to cross intervening seas between one continent and another. It is suggested that this ability may be physiologically related to their capacity to use aerial respiration. There is some evidence for a separate Devonian osteostracan fish fauna in China. Amphibians are first known from the uppermost Devonian of the Euramerican continent, and land vertebrates are known almost exclusively from that continent until the Mid Permian. It is suggested that tetrapods may have evolved in Euramerica, and were only able to colonize Asia and Gondwanaland after continental drift had linked these areas with Euramerica, causing the Uralian and Alleghanian orogenies.
94Â citations
TL;DR: Stratified sampling techniques are found to exhibit greater overall comparative accuracy then either random or systematic sampling, though their general behavioural properties mirror those of the parent strategy in other respects.
Abstract: The properties offour sampling models, random and its derivative stratified random sampling, systematic and its derivative stratified systematic unaligned sampling, are examined empirically with special reference to the context of vegetation survey. Some interesting behaviour patterns emerge in relation to (i) relative accuracy at high and low sample intensity, (ii) variability of estimation, (iii) performance with units of different shape and fragmentation, and (iv) stabilization across sample intensity. Stratified sampling techniques are found to exhibit greater overall comparative accuracy then either random or systematic sampling, though their general behavioural properties mirror those of the parent strategy in other respects. Finally, the different spatial properties of the models are briefly discussed.
72Â citations
TL;DR: In this article, the production, movement and storage of seed in an old growth coniferous forest and adjacent secondary community in British Columbia, Canada, were monitored for three years.
Abstract: Production, movement and storage of seed in an old growth coniferous forest and adjacent secondary community in British Columbia, Canada, were monitored for 3 years. The old growth forest possessed a small seed budget that included some seed of secondary species, characteristic of disturbed situations. The secondary community possessed a far larger seed budget, dominated by locally-growing secondary species. Small quantities of seed of secondary species were able to infiltrate appreciable distances into the old growth forest. However, the store of seed of these species within the forest was insufficient to account for the large populations that soon appear at logged sites, unless initial populations deriving from this source had undergone very rapid expansion thereafter. The development of rotational tree harvesting in the area is likely to promote an expanding seed budget for secondary species, and a diminishing one for the primary species, characteristic of old growth forests.
64Â citations
TL;DR: In this article, the authors examined a large sample of salt pans from the North Norfolk coast salt marshes and found that pan density is positively related to marsh height and negatively to distance from the marsh/sea edge.
Abstract: The widely accepted view that salt pans are formed during the initial colonization of the marsh surface is examined using a large sample of salt pans from the North Norfolk coast salt marshes. A multiple regression model suggests that pan density is positively related to marsh height and negatively to distance from the marsh/sea edge. Since marsh height increases with time this model does not agree with the initial hypothesis. Further investigation of the regression model, however, indicates the dangers inherent in assigning causal mechanisms, for the independent variables are shown to be merely limiting conditions of pan density. Examination of these factors allows an alternative hypothesis for pan formation to be postulated: pans may be formed by the erosion of bare patches in the existing marsh vegetation, caused by rafts of vegetation debris brought in by high tides and deposited on the marsh surface.
60Â citations
TL;DR: It is suggested that the savanna islands in southern Venezuela are relics of more widespread savanna which existed under previously drier conditions; the islands have survived locally through burning, in spite of a later tendency to increasing rainfall and general reforestation.
Abstract: Isolated tracts of savanna in the humid environment of southern Venezuela are described. Their distribution is not related to peculiarly adverse soil conditions; nor do the savannas seem to have been formed solely as a result of slash and burn agriculture or direct forest burning. Nevertheless, the savannas are contemporarily fire maintained. In view of these conditions and also of the floristic affinity among tropical American savannas, it is suggested that the savanna islands in southern Venezuela are relics of more widespread savanna which existed under previously drier conditions; the islands have survived locally through burning, in spite of a later tendency to increasing rainfall and general reforestation. Similar relict savannas also exist elsewhere within the main body of the Amazon forest. In currently drier areas such as the llanos and campos cerrados the situation is less clear, but some relict savanna may also exist in places where pyrogenic savanna has been postulated.
52Â citations
TL;DR: The Engines of the Planet II:Evolution, the Source of Novelty as mentioned in this paper is a history of biogeography with a focus on plate tectonics and the evolution of life on the planet.
Abstract: Preface. Acknowledgments. 1 A History of Biogeography. 2 Patterns of Distribution. 3 Communities and Ecosystems. 4 Patterns of Biodiversity. 5 The Engines of the Planet I: Plate Tectonics. 6 The Engines of the Planet II:Evolution, the Source of Novelty. 7 From Evolution to Patterns of Life. 8 Life,Death,and Evolution on Islands. 9 Drawing Lines in the Water. 10 Living in the Past. 11 The Geography of Life Today. 12 Ice and Change. 13 The Advent of Humanity. 14 Into the Future. Conservation Biogeography. Further Reading. References. Glossary. Index.
39Â citations
30Â citations
TL;DR: Braun-Blanquet's traditional phytosociological method is assessed alongside a number of numerical taxonomic methods such as associationanalysis and other clustering techniques to assess the relative merits of these methods.
Abstract: This study attempts to assess the relative merits of a number of classificatory methods suitable for examining plant/environment relationships on a local and regional scale. Braun-Blanquet's traditional phytosociological method is assessed alongside a number of numerical taxonomic methods such as associationanalysis and other clustering techniques. Each classification is evaluated in terms of the clarity of the hierarchical groups and the ease with which some rational hypotheses can be formulated concerning these groups and their environmental relationships. A procedure which can be used for these assessments is outlined and some preliminary conclusions drawn about the merits of particular classifications.
TL;DR: Attempts have been made to determine the position of the Permian equator by means of spatial diversity changes in brachiopods of that age, but the results have been interpreted in very different ways.
Abstract: Following a brief review of the faictors controlling the distribution of terrestrial vertebrates and marine invertebrates four patterns of provincialism related to lithospheric plate movements are distinguished, and illustrated by both qualitative and quantitative studies. Diversity changes in geological time, with mass extinction treated as an extreme case of diversity reduction, have been explained by the splitting and suturing of continental masses, with concomitant changes in potentiality for genetic isolation and interspecies competition as well as such non-biological factors as stability or predictability of the environment and position of sea level. However, the postulated diversity increase since the Palaeozoic has been challenged on methodological grounds. Attempts have been made to determine the position of the Permian equator by means of spatial diversity changes in brachiopods of that age, but the results have been interpreted in very different ways.
TL;DR: In this article, the species and stand relationships in an area of eucalypt forests and woodlands to the east of Hobart, Tasmania, Australia are described and the vegetation is shown to be essentially a continuum with sharp vegetation boundaries only occurring on geological junctions in drier parts of the study area.
Abstract: This study describes species and stand relationships in an area of eucalypt forests and woodlands to the east of Hobart, Tasmania, Australia. Quadrat and species groupings are found to be related to substrate, altitude and aspect. However, the vegetation is shown to be essentially a continuum with sharp vegetation boundaries only occurring on geological junctions in the drier parts of the study area. The frequency and intensity of fire has a marked effect on the physiognomy of the vegetation, but probably has only marginal effects on species composition.
TL;DR: This study uses a variety of indices to outline spatial differences in the seasonal rainfall regimes of the Tsavo National Park and adjacent areas and calls for a careful assessment of these environments.
Abstract: The bimodal rainfall regime of the greater part of Kenya has long been recognized (Miller, 1931). But due partly to the inadequacy of the rain gauge network and to the low density of population, few detailed studies of the seasonal characteristics of precipitation have been carried out, particularly for the semi-arid region of Kenya. The necessity for sound management strategies in all the low rainfall zones of Kenya is particularly apparent in many of the national parks and game reserves, and calls for a careful assessment of these environments. This study uses a variety of indices to outline spatial differences in the seasonal rainfall regimes of the Tsavo National Park and adjacent areas.
TL;DR: The inner limits of the distribution of three common corticolous lichens are mapped in the west central Scotland area using a modified version of Hawksworth & Rose's qualitative zone scale for estimating mean winter S02 using lichens and a new technique for determining microgram amounts of sulphur in lichen material is briefly outlined.
Abstract: The inner limits of the distribution of three common corticolous lichens are mapped in the west central Scotland area. By employing a modified version of Hawksworth & Rose's (1970) qualitative zone scale for estimating mean winter S02 using lichens, the pattern of S02 air pollution over the survey region is traced. That the lichen data reflect S02 levels rather than other factors is supported by (a) field transplant experiments which show that Hypogymnia physodes and Usnea subfloridana accumulate sulphur and exhibit morphological damage in proportion to the mean S02 levels, and to a lesser extent by (b) bark pH studies which demonstrate that a good linear relationship pertains between mean pH and S02. A new technique for determining microgram amounts of sulphur in lichen material is briefly outlined.
TL;DR: In this paper, an intensive survey was made of part of one campo area using a grid of 108 quadrats, each 4 m x 4 m in size, and presence/absence data for all plant species within this have been analysed using association analysis and principal components analysis, and the resultant groupings of quadrats compared with values of soil moisture, organic content, pH, levels of extractable sodium, potassium, calcium, magnesium andphosphate.
Abstract: Variations in the floristic composition and environmental conditions of an area of grassland from the northeastern Mato Grosso are described. The grassland, including a range from dry grassland to the moister campo types, occurs as a narrow strip between gallery forest and savanna woodland (cerrado), and is subjectively classified into eight main divisions: 1, cerrado/campo transitional areas; 2, dry grassland on lateritic hills; 3, white sand areas at heads of campos; 4, dry campo; 5, campo of intermediate wetness; 6, wet campo; 7, very wet campo flushes; 8, gallery forest/campo transitional areas. An intensive survey was made of part of one campo area using a grid of 108 quadrats, each 4 m x 4 m in size. Presence/absence data for all plant species within this have been analysed using association analysis and principal components analysis, and the resultant groupings ofquadrats compared with values of soil moisture, organic content, pH, levels of extractable sodium, potassium, calcium, magnesium andphosphate. Although the campo is sharply defined at its boundaries with cerrado and gallery forest, the vegetational variation within it proved to be continuous andgradual. The distribution of most species in this campo is most closely correlated with soil moisture differences. Most species are restricted to a narrow range within the soil moisture gradient and appear to be independently distributed. It is concluded that the species composition of the vegetation is determined by a combination of the range of water table fluctuations and by burning.
TL;DR: The occurrence of slough grass (Beckmannia syzigachne (Steud.) Fern.
Abstract: The occurrence of slough grass (Beckmannia syzigachne (Steud.) Fern.) in the Mackenzie River Delta appears to be a consequence of the following sequence of physical and biological interactions. Within lakes that are connected to major distributaries, miniature deltas and wave-built shoals are formed by locally accelerated sediment deposition. Waterfowl are initially attracted to these topographic features because their insular nature affords protection from terrestrial predators. Heavy use by waterfowl causes ecological modifications along the margins of these sites: Beckmannia syzigachne is introduced, while grazing and nitrification stimulates the growth of native grasses, causing a greater cover and abundance in the affected area. The attractiveness of delta points and wave-built shoals as resting and feeding sites causes waterfowl to continue to frequent them, and vegetation along their margins is maintained in a disclimax condition.
TL;DR: The authors describe the application of a range of water insoluble dyestuffs for use in soil water studies that are easy to prepare, are not washed out of the soil, and can be extracted with simple inexpensive apparatus.
Abstract: The authors describe the application of a range of water insoluble dyestuffs for use in soil water studies. These water insoluble dyes are easy to prepare, are not washed out of the soil, and can be extracted with simple inexpensive apparatus.
TL;DR: Theories of the relationships involved in species movement between different zoogeographic regions or subregions are examined, and the conclusion reached that it is not necessary to invoke the concept of relative species dominance as a determinant of the direction of species movement in many cases.
Abstract: Theories of the relationships involved in species movement between different zoogeographic regions or subregions are examined, and the conclusion reached that it is not necessary to invoke the concept of relative species dominance as a determinant of the direction of species movement in many cases. Alternative views are put forward, using techniques similar to those developed by Macarthur & Wilson in their study of island biogeography. The theory of the relationships between different zoogeographic regions or subregions has not been examined in detail, although I have elsewhere (Horton, 1973a, b, 1974) looked at some aspects of the problem. Darlington (1957) examined these relationships qualitatively and suggested that the main factor determining direction of species movement between -such regions was the relative dominance of the groups in the areas concerned. Simpson (1950) documented the interchange of species between the nearctic and neotropical regions and also reached the conclusion that dominance determined the direction of species movement. I have suggested (Horton, 1974) that it is not necessary to use the concept of dominance to explain Darlington's and Simpson's findings, but that the patterns of climatic change in different regions provide a sufficient explanation. It should, nevertheless, be possible to make some generalizations about patterns of dispersal and this study is an attempt to find such generalizations. Macarthur & Wilson (1963, 1967) expressed the hope that the methods they developed for the study of island biogeography could be extended to encompass other aspects of zoogeography. This study uses similar techniques modified to allow for an interchange of species between two regions, rather than the one way flow of species from the mainland to an island. Let us consider two areas, A and B, separated by a barrier. Let each contain ten species and let each satisfy the following conditions: (1) no previous contact between A and B; (2) both A and B have reached equilibrium with other areas, i.e. they are holding an equilibrium number of species with extinction balancing immigration; (3) all species in A and B are equally likely to