Vegetation History (Handbook of Vegetation Science, vol. 7)

348 tentatively suggested. This paper clearly represents a valiant effort to stimulate thought on the interpretation of the available paleoecological data and stresses the great lack of studied sites in the Amazon lowlands. Subsequently Radtke provides preliminary results from marine terraces about tectonic uplift in north and central Chile. Suguio and Tessler report about the assemblages of sedimentary structures in a nearshore deposit. The Holocene environmental history of Argentina is reviewed by Rabassa. The volume ends with a study on shoreline changes in French Guiana (Prost) and a geological mapping project of the north coastal plain of Rio Grande do Sul in southern Brazil (Horn). The 18 papers of highly variable scope are generally well presented. The layout of some papers is aberrant and a few graphs have too small lettering, whereas some other reproductions need more focus. These remarks aside, the volume contains valuable contributions and is another argument for centers of Quaternary studies, to place this serial on the bookshelves to promote easy access. HENRY HOOGHIEMSTRA(Amsterdam)

Vegetation History (Handbook of Vegetation Science, vol. 7). B. Huntley and T. Webb III (Editors). Kluwer Academic Publishers, Dordrecht/Boston/London, 1988, xx+803 pp. ISBN 90-6193-188-6. Price: Dfl. 400.00/US$ 220.00/£stg 116.00. Hardback. Knowledge of past vegetation distribution is fundamental to the study and understanding of modern flora and plant communities. It is in that light that the publication of a volume on Vegetation history in the series Handbook of vegetation science should be viewed. The volume consists of 21 chapters, grouped into four sections. An introduction and a closing discussion by the editors and an index complete the book. In the introduction the editors mention that they have tried to select reviews that will appeal to ecologists and especially to

vegetation scientists. This should by no means be taken to mean that the book would be of less interest to palynologists and palaeobotanists. On the contrary: for the reviewer it functioned as an efficient upgrading course. The volume contains a wealth of information not always readily available to the individual researcher. The first section, on Background and Methods, starts with a chapter by George L. Jacobson Jr., in which basic principles of the study of vegetation history, such as deposition and source area of plant remains, sampling strategies and analytic methods, are very briefly reviewed. Several of these aspects are treated at greater length in succeeding chapters. The author makes the interesting point that a stratigraphic deposit can be considered as a type of permanent plot, one that is collecting data continuously for thousands of years. In the second chapter, by I. Colin Prentice, the question of how pollen records vegetation is the central theme. The problem of pollenvegetation relationships can be approached from two sides, the empirical one (surface samples, artificial pollen traps) and the theoretical one. The author presents theoretical models, formulated in mathematical equations, for the dispersal and deposition of pollen and for the calibration of pollen data, i.e. the quantitative correspondence between pollen frequencies and plant abundances. It is reassuring that the theoretical models do not upset the traditional interpretation based upon empirical evidence. In his chapter entitled '~Data analysis and display", Eric C. Grimm focusses upon the analogue approach for reconstructing past vegetation. The potentialities of the use of multivariate numerical techniques for grouping surface~sample pollen spectra are illustrated by a few examples. Similarly, ordination methods are applied to determine whether or not fossil pollen assemblages have analogues in the modern pollen rain. It is evident that the analogue approach works successfully only in regions in which enough natural vegetation is still left. The greater part of Europe, for instance, does not meet this requirement.

349 Dating methods are reviewed by Matti Saarnisto (Time-scales and dating). Radiometric dating methods applied to the last 10 million years include radiocarbon, uraniumseries, potassium-argon and thermoluminescence dating. A particularly precise time-scale is provided by the varve chronology. Dating via correlation of pollen assemblage zones requires t h a t they be synchronous over wide areas, which is problematic to say the least. Not only volcanic rocks but also marine and fresh-water sediments lend themselves to magneto-stratigraphic studies, thus permitting long-distance correlation. A less well-known relative dating method concerns amino acid dating, based upon the conversion of L ("lefthanded") to D ("right-handed") amino acid isomers after the death of an organism. The final chapter of the first section, by Patrick J. Bartlein, deals with non-botanical evidence of climatic changes (Late-tertiary and quaternary palaeoenvironments). The nature and (possible) causes of climatic variations on different time-scales, ranging from less t h a n 101 to more t h a n 106 years, are reviewed. Climatic simulation models provide a means for explaining the climate of the past, as is illustrated by the example of the simulated atmospheric circulation 18,000 years ago. A key role in the climatic history is attributed to insolation variations, determined by variations in the earth's orbit and axial orientation, implying a rehabilitation of the old Milankovitch theory. The climatic implications of the variations in oxygen isotope ratios t h r o u g h o u t the Cenozoic, in relation to geological events, are discussed. Section II, entitled "Late-Tertiary and Pleistocene Vegetation History" includes four chapters on longer-term vegetation histories of major geographical areas. In the chapter on Europe, William A. Watts reviews at some length the Pliocene-Pleistocene boundary, which witnessed a dramatic impoverishment of the flora, the Holsteinian (the last interglacial but one) and the Eemian interglacial followed by a few interstadials. The post-Eemian warm phases have actuated the question of the

distinction between interglacials and relatively warm interstadials. Watts discusses criteria other than vegetation that could be adduced in defining an interglacial, such as an enhanced seasonality of warmer summers and colder winters at the beginning of an interglacial and a metronomic regularity of glacial/ interglacial cycles. Curiously, Frenzel's synthetic work on the Pleistocene flora of northern Eurasia is not mentioned. The chapter on North America, by Linda E. Heusser and James E. King, reviews a large body of data pertaining to different periods and areas. Pliocene floral data, predominantly plant macrofossils, are evidence of the development of vegetation adapted to drier and cooler environments and of increasing geographic diversification. The Pleistocene vegetation history of coastal western North America reflects glacial/interglacial cycles, but through the moderating influence of the Pacific Ocean, glacial climates were relatively mild and temperate conifer forest could maintain itself. Different climatic histories are concluded for the Sangamonian (last interglacial) of the central and the eastern United States. The pollen evidence testifies to a long midWisconsinan interstadial (> 50,000-c. 25,000 B.P.) with predominantly open forest and woodland. Palynological evidence for the Late Cenozoic of Australasia, discussed by A.P. Kershaw, is confined mainly to New Zealand, SE and NE Australia. In the early Miocene, vegetation was more homogeneous than it is today, closed forest being predominant. In Australia, mesic rain forest was severely affected in the Late Tertiary, for which reduced temperatures as well as lowering of precipitation are held responsible. The Pleistocene witnessed an alternation of dramatic expansion of open woody and herbaceous vegetation during glacial periods and recolonization by arboreal vegetation during interglacials. The author holds the view t h a t the replacement of firesensitive rain forest and sclerophyll communities by fire-resistant and fire-promoting vegetation, as recorded in Late Pleistocene

350 pollen sequences, was brought about by the Aboriginals through the practice of burning. The chapter on (northern) South America by Thomas van der Hammen differs from the other contributions in that the palynological evidence discussed has all been obtained by the author and collaborators. This is simply because no other evidence is available. Most impressive is the continuous long pollen record of the high plain of Bogota, displaying 15 major climatic cycles in the Quaternary. For the northern tropical Andes the vegetation and climatic history of the last glacial could be reconstructed in considerable detail. During dry periods, probably corresponding to certain intervals of Pleistocene glacials, savanna vegetation replaced tropical lowland forest, leading to a fragmentation of the rain forest. Section III comprises 6 chapters on the glacial and Holocene vegetation history (20,000 B.P. to the present) of temperate and boreal regions in both the northern and southern hemispheres. The European scene is treated by Brian Huntley who has expertly succeeded in amalgamating the tremendous body of data available for this continent. TWINSPAN (Two-way Indicator Species Analysis) has been employed to distinguish groups of pollen spectra which would correspond to major vegetation units. For some selected periods maps showing the distribution of these vegetation units are presented. The greatest range of vegetation units, and the most complex patterns, occurred in the early Holocene, between 10,000 and 7000 B.P. The author argues against the view that human activity would account for the expansion of Picea, Fagus and Carpinus into parts of Europe and for the development of sclerophyllous woodland and scrub in the Mediterranean lowland. The vegetation history of Eastern North America is reconstructed by Thompson Webb III on the basis of isopoll maps for 18 pollen types. The fact that the abundances of these pollen types at 500 B.P. (prior to European contact) parallel the current patterns of the major plant formations (tundra, boreal forest, etc.) justifies

the assumption that isopoll maps record former vegetation patterns. The full-glacial vegetation (with Picea woodland in the north and Pinus forest or woodland in the south) has no modern analogues. After 10,000 B.P. modern distribution and composition of the vegetation on a subcontinental scale developed. The individual taxa within the plant formations have diverse histories and the distribution areas of the plant formations themselves have changed to some extent, e.g. east west movements of the prairie-forest ecotone. It is to be regretted that the isopoll maps have been printed on too small a scale. In his essay on vegetation development in Western North America over the last 20,000 years, Robert S. Thompson focusses upon the mechanisms that plants have employed to survive continual environmental changes (asexual reproduction, elevational and geographic shifts in distributions, trade-offs in varieties and races). In addition to pollen data (from wet as well as dry sediments), in arid regions, plant macrofossils from ancient packrat middens are an important source of information on past vegetation. The Southwest of the United States experienced a relatively humid climate at approximately 18,000 B.P.. with pine-juniper-oak woodland in the area of the present Sonoran desert. As plant formation the Sonoran desert was already in existence before 8000 B.P., but it was not until 4000 B.P. that it obtained its modern floristic composition. For readers not very familiar with the western United States a locational map would have been most useful. Matsuo Tsukada presents a synthesis of Late Quaternary palynological research in the Japanese Archipelago. The interpretation of the fossil pollen record in terms of past vegetation is based upon the modern mean frequencies of eight major pollen types in the various vegetation belts. Modern and past pollen frequencies are plotted in so-called latitude-altitude diagrams, visualizing the representation of the species concerned along a southeast northwest axis through the country. During the full glacial, approximately 20,000

351

B.P., coniferous forests prevailed. The lateglacial and early postglacial periods (15,0007000 B.P.) witnessed the expansion of temperate broad-leaved forests. Tsukada's contribution certainly is a very elaborate one, but the wealth of data presented adversely affects the readableness. Research in the Arctic is reviewed by Henry F. Lamb and Mary E. Edwards. A structural problem in arctic palaeoecological studies is formed by the low diversity of the flora, taxa tending to occur in a variety of habitats. The numbers of pollen sites in arctic regions are still small, but, supported by data from surfacesample studies, tentative reconstructions of broad-scale vegetational changes can be made. During the full glacial, under colder and more arid climatic conditions than present, the icefree parts of Beringia must have supported several kinds of vegetation. Much work has focussed upon tree-line shifts, taken to reflect climatic changes. In the early Holocene, in various areas trees extended considerably far north of the present tree limit. A few examples of local-scale reconstructions of vegetational development are discussed. The study of the vegetational history of New Zealand, reviewed by Matthew S. McGlone, is hampered by the fact that most of the trees and shrubs have a poor pollen dispersal (being animal-pollinated), in consequence of which conifers and a few anemophilous broad-leaved trees, e.g. Nothofagus, are clearly dominant in the modern pollen rain, During the glacial maximum (22,000-14,000 B.P.), arboreal vegetation was scarce, due to fires, strong winds and incursions of polar air masses, in addition to lower temperatures and less precipitation. The Late-glacial witnessed a rapid re-afforestation of North Island, suggesting t h a t forest species survived the glacial maximum in numerous, scattered, small areas. It was not until the beginning of the Holocene t h a t forest spread in South Island. Early Holocene (95007500 B.P.) forests and shrublands differed from those at present and would point to a milder climate with only weak seasonality. In the fourth section six chapters dealing

with special topics are assembled. William A. Patterson III and Andrew E. Backman treat studies on fire and disease history. Levels of abundant charcoal particles in sediments testify to the occurrence of past fires, the effects of which on the vegetation are revealed by the pollen record. Frequent fires would have been responsible for maintaining stable plant communities, even under changing climatic conditions, whereas infrequent fires initiated new successional sequences. In contrast to fires, pathogens are host-specific and affect only one species directly, but the decimation of one particular species may have brought about a series of changes in the forest composition. As an example of a possible prehistoric disease outbreak the hemlock (Tsuga) decline throughout eastern North America c. 4800 B.P. is discussed. The role of man in European vegetation history is reviewed by Karl-Ernst Behre. Although Mesolithic hunter-gatherers will have occasioned local woodland disturbances, the active encroachment of man upon the environment started with the arrival of Neolithic farmers. The human impact is well documented in the pollen record, supplemented by plant macrofossil remains. The effects of various forms of farming economy on the vegetation are discussed. Behre sketches the development of a landscape in which finally hardly any natural vegetation has been left. In contrast to Europe, pollen evidence from Central and North America reflects at most small-scale disturbances brought about by prehistoric agriculturists (John H. McAndrews: Human disturbance of North American forests and grasslands). Indian populations were smaller and more localized than those of prehistoric farmers in Europe and, moreover, no domestic grazing animals were kept. Forest destruction and farming by Europeans in North America are expressed in the pollen record by a distinct rise in the percentages for Ambrosia and various other weeds, both native and introduced. K.D. Bennett (Postglacial vegetation history: Ecological considerations) defines the pur-

352 pose of his essay as that of describing the phenomena of changing species distributions and abundances, as seen in the fossil record, in terms of the behaviour of plant species in response to environmental change and of the interactions between plant species (p.700). Distribution changes were most dramatic during periods of relative climatic instability (glacial/interglacial transitions), but also during periods of relative climatic stability major changes in the composition of the vegetation have occurred, e.g. as the result of the migration of slowly spreading species or of gradual soil changes. The author discusses at some length factors which may have determined rates of migration and expansion. The last two contributions of section IV concern the potential of improving temporal and spatial resolution of pollen data, thus bridging the conceptual gap with regard to time- and space-scales between plant ecologists and palynologists. Spatially-precise studies of forest dynamics (Richard H.W. Bradshaw) are permitted by the palynological examination of small-hollow sites and mor-humus deposits. "Closed-canopy" sites recruit their pollen from small source areas, thus providing highly localized vegetation reconstructions. In these sites, small-scale vegetation dynamics not resolved by regional sites are recorded. A selection of small-hollow and mor-humus studies from Sweden, Denmark, Ireland and the U.S.A. are presented. Pre-eminently suited for fine-resolution pollen analysis (Judith Turner and Sylvia M. Peglar: Temporally-precise studies of vegetation history) are annually-laminated sediments, which seem to be more widespread than was previously recognized. Peat deposits can equally be used for temporally-precise studies. Here radiocarbon dates, in combination with relative peat accumulation rates calculated from pollen concentrations, should provide a precise timescale. Fine-resolution pollen diagrams from three peat deposits in England appear to indicate that the well-known elm decline of approximately 5000 B.P. has to be attributed to different factors depending upon the site.

In their concluding observations the editors remark that perhaps the fundamental conclusion which emerges from palaeoecological studies is that change is the rule. Plant communities did not act as units in the past, but taxa responded individually to environmental forcing. As a consequence, plant communities do not constitute stable units, but they are continuously changing assemblages of species. W. VAN ZEIST (Groningen)

Concepts, Limits and Extension of the Indian Gondwana. Editors: B.S. Venkatachala and H.K. Maheshwari. The Palaeobotanist. 1987, Vol. 36, 377 p. (ISSN 0031-0174). US$ 150.00, available at Birbal Sahni Institute of Palaeobotany, 53 University Road, Lucknow 226007, India. The proceedings of the Symposium Concepts, limits and extension of the Indian Gondwana organized by the Birbal Sahni Institute of Palaeobotany from 14th to 18th November 1987 in Lucknow, has been published in the 36th volume (1987) of the Indian Scientific journal The Palaeobotanist. The work is voluminous and contains 377 pages. It is well presented and the illustrations are of good quality. The photographic plates, including one in colour, are so welcome that it is regrettable that there are not many more of them. The 42 articles in this volume are varied in their content and range of themes, which mainly refer to three aspects: ~'sequence"~ "land" and ~'floras". The Gondwana "sequence" deals mostly with the flora and fauna of the different formations. It also contains a few thematic analysis of siliciclastic, organic and volcanic series. The Gondwana "land" is approached from both the paleobiogeographic and paleoclimatic points of view, again with the help of megaand microfloras. However, we note some new