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The mountainous region of northwest Greece has often been cited as a possible area for the existence of temperate tree taxa during the last glacial. This series of papers examines the vegetational history and sedimentary history of two small basins in the Pindus mountain range of northwest Greece. The two basins are 18 km apart but at contrasting heights of 285 and 1800 m. The present paper describes results from the lowland basin of Gramousti lake. Techniques of pollen analysis, plant macrofossil analysis, sediment chemistry, mineral magnetics and radiocarbon dating are employed to reconstruct both the vegetational and sedimentary history of the basin. The sequence extends c. 14000 BP to c. 1000 BP. Palaeobotanical studies suggest that, during the lateglacial, vegetation in this lowland region was dominated by herbaceous taxa indicative of an open environment. Of the trees, only Quercus and Pinus were present, in low numbers. The lateglacial/postglacial transition was represented by an expansion of oak woodland and a reduction in steppe vegetation. Quercus dominated woodland persisted throughout much of the postglacial and became more diverse at c. 7500 BP with the arrival and expansion of Carpinus orientalis/Ostrya carpinifolia. Anthropogenic intervention at c. 4500 BP was probably responsible for a reduction in the oak woodland and the formation of a vegetation type similar to present day which is dominated by herbaceous taxa and chew-resistant shrubs such as Quercus coccifera and Paliurus spina-christi. [ABSTRACT FROM AUTHOR]

This paper presents macrofossil data and additional pollen analyses from the Quaternary sites previously described in Oldfield (1967). Pollen evidence presented in that paper from Bidart Plage Series B (Bidartian) and Senix Series 1 (Moulignan and Senixian) is amplified and extended by more detailed and comprehensive diagrams. The additional pollen-analytical evidence from the Bidart section confirms the importance of a Castanea-dominated pollen assemblage zone within the Bidartian Interglacial. The new diagram from Senix shows that the Moulignan major biostratigraphic subdivision is likewise interglacial in character. The late-temperate and post-temperate stages of this interglacial are well represented by the Senix and Mouligna Cliff pollen sequences now published. The macrofossil evidence from Bidart Series B(Bidartian), Mouligna Cliff MC3 (Ilbarritzian) and Marbella (Marbellan) is represented on a quantitative basis using large and volumetrically equivalent samples from each level. The main additions to the flora from these macrofossil diagrams are a wide variety aquatic and semi-aquatic species including, for the Bidartian, Ludwigia palustris and for the Marbellan, Aldrovandra vesiculosa and Proserpinaca cf. palustris a North American species not previously recorded in Post-Tiglian deposits from Europe. From Bidart, there are also interesting macrofossil records of woody warm temperate taxa, for example Chamaecyparis thyoides, Cotoneaster acuticarpa and Ostrya cf. carpinifolia. The non-aquatic macroflora from Marbella is dominated by Erica species the seeds of which have been identified largely on the basis of the fine detail of their seed coats revealed by Scanning Electron Microscopy (Huckerby, Marchant and Oldfield, 1972). [ABSTRACT FROM AUTHOR]

Pollen grains are microscopic so their identification and quantification has, for decades, depended upon human observers using light microscopes: a labour-intensive approach. Modern improvements in computing and imaging hardware and software now bring automation of pollen analyses within reach. In this paper, we provide the first review in over 15 yr of progress towards automation of the part of palynology concerned with counting and classifying pollen, bringing together literature published from a wide spectrum of sources. We consider which attempts offer the most potential for an automated palynology system for universal application across all fields of research concerned with pollen classification and counting. We discuss what is required to make the datasets of these automated systems as acceptable as those produced by human palynologists, and present suggestions for how automation will generate novel approaches to counting and classifying pollen that have hitherto been unthinkable. [ABSTRACT FROM AUTHOR]

Few studies have examined patterns of pollen deposition or the relationship between vegetation and pollen assemblages at the small scale. This paper examines the representation of both individual taxa and whole plant communities in modern pollen spectra. Micro-scale variations in modern pollen deposition were studied in three alpine plant communities on Storbreen glacier foreland, southern Norway; a pioneer community; a Salix-shrub community; and an ericaceous heath community. The relationships between vegetation and modern pollen deposition and the variability of these relationships at the local scale were investigated within 16 × 1 m²-quadrats. The data were classified using two-way indicator-species analysis (TWINSPAN) and ordinated using detrended-correspondence analysis (DCA). In addition, the pollen and vegetation data were ordinated simultaneously, using canonical correspondence analysis (CCA). The effect of removing arboreal pollen from the pollen sum was examined. The three plant communities were distinguished successfully by multivariate statistical techniques, using both pollen data and vegetation data. However, within the communities there was high variability in pollen deposition, which was most pronounced in the Salix-shrub community. The abundance of individual taxa in the vegetation was compared with their representation in the pollen spectra. The strongest relationships were shown by Salix, Ericales, Empetrum and Lycopodium. Certain taxa showed consistent, reproducible patterns of behaviour. These patterns provided valuable evidence for separating contrasting plant communities. Comparison of modern pollen-vegetation relationships of this kind with pollen data from Holocene and Pleistocene sites is important to improve the reconstruction of past plant communities. [ABSTRACT FROM AUTHOR]

This paper describes palaeoecological studies at Abernethy Forest by means of pollen and macrofossil analysis and radiocarbon dating. It also illustrates the value of stratigraphic macrofossil analysis in conjunction with pollen analysis in increasing the range and detail of palaeoecological reconstructions of past vegetation and environment. A new, large diameter core from Abernethy Forest was radiocarbon dated, and the presence of Late Devensian sediments was confirmed. Clear vegetational changes were recorded. A pioneer grass-sedge vegetation colonized the bare moraine. It developed into a shrub tundra, dominated by Empetrum and Betula nana as a result of the climatic warming during Allerød time. The Younger Dryas climatic deterioration led to the formation of species-rich open vegetation, in which Artemisia was very abundant. At the opening of the Flandrian, at about 9700 B.P., Juniperus and. Betula nana scrub developed, which was later colonized by tree Betula and then Corylus. From about 7225 B.P. Pinus dominated the forest. Throughout, the specific determinations and local derivation of macrofossils enhanced the reconstruction of the upland vegetation. In addition, macrofossils provided the majority of the evidence for the progression of the hydrosere through lake to bog communities. The complementary nature of pollen and macrofossil analyses from the same core is emphasized by a direct comparison of seed and pollen influxes. [ABSTRACT FROM AUTHOR]

A method is described for studying simultaneously the intact and the sectional view of pollen walls. Scanning electron micrographs of such fractured pollen grains of Tilia platyphyllos Scop., T. cordata Mill. and the putative hybrid T. × vulgaris Hayne assist in the interpretation of a number of observations made by light microscopy on the differences between these taxa and confirm and amplify our interpretation of T. platyphyllos made from early transmission electron microscopy of embedded and sectioned grains. The new information makes imperative the distinction between two types of exine reticulation, one bacula-bordered and the other bacula-centric (the Tilia type). [ABSTRACT FROM AUTHOR]

Summary: Pollen identification and quantification are crucial but challenging tasks in addressing a variety of evolutionary and ecological questions (pollination, paleobotany), but also for other fields of research (e.g. allergology, honey analysis or forensics). Researchers are exploring alternative methods to automate these tasks but, for several reasons, manual microscopy is still the gold standard.In this study, we present a new method for pollen analysis using multispectral imaging flow cytometry in combination with deep learning. We demonstrate that our method allows fast measurement while delivering high accuracy pollen identification.A dataset of 426 876 images depicting pollen from 35 plant species was used to train a convolutional neural network classifier. We found the best‐performing classifier to yield a species‐averaged accuracy of 96%. Even species that are difficult to differentiate using microscopy could be clearly separated.Our approach also allows a detailed determination of morphological pollen traits, such as size, symmetry or structure. Our phylogenetic analyses suggest phylogenetic conservatism in some of these traits. Given a comprehensive pollen reference database, we provide a powerful tool to be used in any pollen study with a need for rapid and accurate species identification, pollen grain quantification and trait extraction of recent pollen. [ABSTRACT FROM AUTHOR]

Summary: Despite numerous attempts to elucidate the developmental mechanisms responsible for the observed diversity of pollen and spore walls, the processes involved remained obscure until the structures observed during exine development were recognized as a sequence of self‐assembling micellar mesophases. To confirm this, a series of in vitro experiments was undertaken in which exine‐like patterns were generated in colloidal mixtures by self‐assembly, without any genomic participation. The intention was to test whether all the main types of exine structure could be simulated experimentally.Mixtures of substances, analogous to those involved in microspore development, were left undisturbed while water evaporated and self‐assembly occurred. We varied the substances, their combinations and concentrations, and the physical constraints to make the experiments closer to the situation in nature. The resulting dry films were then examined using transmission electron microscopy.A variety of microstructures, simulating the full range of exine types, was obtained by micellar self‐assembly. Moreover, the signs of related physicochemical process (i.e. phase separation) were also observed.Simple, energy‐efficient, physical–chemical interactions, phase separation and self‐assembly, are capable of generating exine‐like patterns, providing evidence that these processes share control of exine formation with the well‐documented program of gene expression. [ABSTRACT FROM AUTHOR]

Summary: We investigated the molecular basis and physiological implications of anion transport during pollen tube (PT) growth in Arabidopsis thaliana (Col‐0).Patch‐clamp whole‐cell configuration analysis of pollen grain protoplasts revealed three subpopulations of anionic currents differentially regulated by cytoplasmic calcium ([Ca2+]cyt). We investigated the pollen‐expressed proteins AtSLAH3, AtALMT12, AtTMEM16 and AtCCC as the putative anion transporters responsible for these currents.AtCCC‐GFP was observed at the shank and AtSLAH3‐GFP at the tip and shank of the PT plasma membrane. Both are likely to carry the majority of anion current at negative potentials, as extracellular anionic fluxes measured at the tip of PTs with an anion vibrating probe were significantly lower in slah3−/− and ccc−/− mutants, but unaffected in almt12−/− and tmem16−/−. We further characterised the effect of pH and GABA by patch clamp. Strong regulation by extracellular pH was observed in the wild‐type, but not in tmem16−/−. Our results are compatible with AtTMEM16 functioning as an anion/H+ cotransporter and therefore, as a putative pH sensor. GABA presence: (1) inhibited the overall currents, an effect that is abrogated in the almt12−/− and (2) reduced the current in AtALMT12 transfected COS‐7 cells, strongly suggesting the direct interaction of GABA with AtALMT12.Our data show that AtSLAH3 and AtCCC activity is sufficient to explain the major component of extracellular anion fluxes, and unveils a possible regulatory system linking PT growth modulation by pH, GABA, and [Ca2+]cyt through anionic transporters. [ABSTRACT FROM AUTHOR]

Summary: The timing of the origin of angiosperms is a hotly debated topic in plant evolution. Molecular dating analyses that consistently retrieve pre‐Cretaceous ages for crown‐group angiosperms have eroded confidence in the fossil record, which indicates a radiation and possibly also origin in the Early Cretaceous. Here, we evaluate paleobotanical evidence on the age of the angiosperms, showing how fossils provide crucial data for clarifying the situation. Pollen floras document a Northern Gondwanan appearance of monosulcate angiosperms in the Valanginian and subsequent poleward spread of monosulcates and tricolpate eudicots, accelerating in the Albian. The sequence of pollen types agrees with molecular phylogenetic inferences on the course of pollen evolution, but it conflicts strongly with Triassic and early Jurassic molecular ages, and the discrepancy is difficult to explain by geographic or taphonomic biases. Critical scrutiny shows that supposed pre‐Cretaceous angiosperms either represent other plant groups or lack features that might confidently assign them to the angiosperms. However, the record may allow the Late Jurassic existence of ecologically restricted angiosperms, like those seen in the basal ANITA grade. Finally, we examine recently recognized biases in molecular dating and argue that a thoughtful integration of fossil and molecular evidence could help resolve these conflicts. [ABSTRACT FROM AUTHOR]

Paternal biocontainment methods ( PBMs) act by preventing pollen-mediated transgene flow. They are compromised by transgene escape via the crop-maternal line. We therefore assess the efficacy of PBMs for transgenic rapeseed ( Brassica napus) biocontainment across the United Kingdom by estimating crop-maternal hybridization with its two progenitor species., We used remote sensing, field surveys, agricultural statistics, and meta-analysis to determine the extent of sympatry between the crop and populations of riparian and weedy B. rapa and B. oleracea. We then estimated the incidence of crop-maternal hybridization across all settings to predict the efficacy of PBMs., Evidence of crop chloroplast capture by the progenitors was expanded to a national scale, revealing that crop-maternal gene flow occurs at widely variable rates and is dependent on both the recipient and setting., We use these data to explore the value that this kind of biocontainment can bring to genetic modification ( GM) risk management in terms of reducing the impact that hybrids have on the environment rather than preventing or reducing hybrid abundance per se. [ABSTRACT FROM AUTHOR]

Contents Summary 483 I. Introduction 483 II. Progress of research on pollen wall development 485 III. The developmental role of the special cell wall 487 IV. Meiosis and the establishment of microspore symmetry 489 V. The origins of the exine during the tetrad stage 490 VI. The free microspore stage to pollen maturation 495 VII. Conclusions 495 Acknowledgements 496 References 496 The outer pollen wall, or exine, is more structurally complex than any other plant cell wall, comprising several distinct layers, each with its own organizational pattern. Since elucidation of the basic events of pollen wall ontogeny using electron microscopy in the 1970s, knowledge of their developmental genetics has increased enormously. However, self-assembly processes that are not under direct genetic control also play an important role in pollen wall patterning. This review integrates ultrastructural and developmental findings with recent models for self-assembly in an attempt to understand the origins of the morphological complexity and diversity that underpin the science of palynology. [ABSTRACT FROM AUTHOR]

• Stigma presentation has received much less attention than pollen presentation. Investigation of the various forms of stigma presentation may reveal previously undescribed reproductive mechanisms in plants. • Here we investigated stigma presentation in the spring-flowering herb Aquilegia yabeana, whose linear stigma gradually develops over the lifetime of the flower. The degree of stigma development and recurvature are influenced by the timing of pollen deposition, apparently to favor cross-pollination. • In this species, autogamous self-pollination was found to occur in the middle of the receptive period of the stigma if prior cross-pollination did not occur. However, because later-arriving cross-pollen was deposited closer to the ovary, it reached the base of the style before self-pollen which had been deposited earlier. • Flexible stigma presentation helps the flower to maximize pollen resources under unreliable pollination conditions, taking advantage of both selfing and outcrossing. This is the first description of stigma development regulated by pollen deposition in a wild plant. [ABSTRACT FROM AUTHOR]

Pollen counting is an important element of research in pollination, and the majority of current methods involve manual counting. An image-processing technique has been developed for accurate counting and sizing of small particles, and this was tested on almond pollen grains. Our automatic process was found to be several times faster than manual counting and more accurate, with an average error of only 3 %. Because of its simplicity, it is an attractive tool for research on such topics as pollen viability or germination. It was found that in the methods using vials there were `residues' of c. 17% on the vial walls and on the handling tools. In addition, the first drop from each vial contained, on average, 1.65 times more grains than the average number of grains in all drops, whereas the last drop from each vial contained fewer grains than the average. This phenomenon was correlated with the non-uniform pollen distribution in the suspension. An automatic counting system is therefore, recommended, to avoid the problem, otherwise a calibration procedure should be used that accounts for both the residues on the tools and the non-uniformity of contents of sample drops. [ABSTRACT FROM AUTHOR]

Percentage and concentration pollen diagrams are presented for two cores (taken 5 m apart) at an upper Pleistocene and Holocene site at Navarres (Valencia, eastern Spain). Chronological information is provided by an internally consistent radiocarbon dating series that extends from c. 20700 to 3075 yr BP. The results highlight the dangers of relying on a single core in interpreting the patterns of variation of particular taxa. Significant palynological differences, seemingly locational, are described between the two cores. The upper Pleistocene records accords well with the widely recognized European sequence of (a) upper Pleniglacial (b) Bölling-Allerod warm period, and (c) Younger Dryas crisis. However, the sequence does not show disruption of vegetation patterns following the commencement of the Holocene, and Pinus continues to be dominant up to c. 5500 6000 yr BP. Later, there is evidence for Quercus forest, mesophilous trees, and xerosclerophyllous Mediterranean vegetation, which is coincident with eutrophication of the study site. These vegetation changes are discussed in the context of anthropogenic disturbance by Neolithic people, competitive exclusion, and climatic change. [ABSTRACT FROM AUTHOR]

Current methods for numerical zonation of biostratigraphic sequences neither assess the reliability of zones identified nor provide any means of determining the number of zones that are 'significant' (based on structure in the data set, rather than the stochastic element). These problems can be overcome by using the broken-stick model to assess the significance of zones against a model of random distribution of zones within a sequence. The broken-stick model is described and its application demonstrated on actual data sets. Additionally, simulation modelling is used to assess the uncertainty of the location of individual zone markers, given the errors of the original data. These widely-applicable methods make it possible to identify zones rigorously and consistently. The potential in biostratigraphy and correlation includes the recognition, correlation and subdivision of chronostratigraphic units in long Quaternary sequences. [ABSTRACT FROM AUTHOR]

The results of 14C- and 210Pb-dated pollen profiles from the Forest of Bowland, Lancashire are presented, covering the period from the late Iron Age up to the present day. Two notable features of the pollen profile are the apparent lack of a period of large-scale forest destruction during the time of the Norse invasions and the substantial phase of tree clearance towards the end of the Iron Age period. The evidence suggests that the Viking invasions into Lancashire may not have been as destructive as once believed. The invasions were probably gradual, possibly localized (certainly as regards the Bowland area) and seem to have occurred alongside existing populations. Previous pollen-analytical evidence regarding the Iron Age peoples of north-west England has supposed them to have had little effect on their surrounding vegetation. It is now suggested that forest clearance previously assigned to the Romans in north-west England is of Iron Age origin. The pollen profiles presented also reflect several changes of socio-economic conditions that have affected rural populations in Lancashire during the last millennium. An important example is the decimation of populations during the fourteenth and seventeenth centuries. It is suggested that these were caused by the development of subsistence economies, leading each time to a Malthusian crisis. These population declines may also have been exacerbated by outbreaks of plague. The fall in population at both times, is clearly reflected by rising arboreal pollen values, indicative of slackening rates of forest clearance. [ABSTRACT FROM AUTHOR]

Soil profile, macrofossil and pollen analysis investigations were carried out at two sites within paludifying pine forest to determine the vegetation succession and paludification history of the area, Isostatic uplift raised the area above sea level less than 500 y ago. Before the land emerged from the sea, Phragmites and Schoenoplectus beds grew in shallow water close to the shore. As the area emerged, shore meadows dominated by grasses, sedges and forbs became established and were in turn replaced by alder woods. Mixed birch and alder woods then developed and the formation of an organic layer started with the accumulation of humus. Birch then largely replaced alder but both were superseded by pine forest about 50 y before the start of the investigation. After pine forest establishment, Sphagnum invaded, peat accumulation started and paludification was under way. Soil waterlogging necessary for paludification to proceed was a result of a low hydraulic head and shallow hydraulic gradient between the study area and the sea. The vegetation succession is comparable with contemporary succession around the present coastline of Hailuoto and on other Finnish islands. Paludification of the area was an autogenic process; no anthropogenic influences were detected. The relevance of this to the origin of blanket mire in Britain during prehistoric times is discussed. It is suggested that more evidence is required to clarify the roles of forest clearance and climate in the inception of blanket mire in Britain. [ABSTRACT FROM AUTHOR]

Results from two years of pollen trapping experiments in New York State show that pollen spectra inside the three caves studied are highly similar to the pollen rain outside the caves. Statistical comparisons of modern pollen spectra derived from Tauber traps, speleothems, moss polsters, and nearby pond sediments suggest that pollen deposition inside caves can provide a reliable index of the regional and local vegetation, directly comparable to the more conventional spectra derived from lake sediments and moss polsters. Because of the relatively low pollen influx inside caves, however, stochastic and episodic forms of particle transport may influence pollen deposition inside caves in proportions that are unique to each site. With careful attention to site parameters such as entrance size, pollen preservation, and modes of sedimentation, investigators could make greater use of caves in palynological studies. [ABSTRACT FROM AUTHOR]

Rezina marsh, a small basin at a height of 1800 m, in the Pindus mountain range, is both the smallest and highest site yet to be studied in Greece. Techniques of pollen and plant macrofossil analysis, sediment chemistry, mineral magnetics and radiocarbon dating have been employed to reconstruct both vegetational and sedimentary history of the basin. The sequence extending back to c. 10000 BP, provides the first evidence for the possible location of full glacial refugia for temperate tree taxa in Greece. In the early postglacial a dense mixed woodland containing at least sixteen different tree taxa was present around the Rezina basin. This woodland persisted throughout the early postglacial although dominance of tree types in the woodlands changed several times. These changes are thought to be closely related to climatic changes during the early postglacial. At c. 6000 BP both the density and diversity of the woodland became greatly reduced. Although there was some recovery of the woodland at c. 5000 BP, anthropogenic intervention at c. 4000 BP led to total destruction of this montane forest and the development of open grassland similar to the present day situation. [ABSTRACT FROM AUTHOR]

Wheat pollen gave up to 81·7% germination when cultured on a 0·7% agar medium containing 100mg l-1 H3BO3, 300 mg l-1 CaCl2 . 2H2O and 0·75 M raffinose. On this medium at 25 °C, germination started within 5 min and tubes reached a mean maximum length of 200 μm after 1 h. Maltose supported 27·9 % germination, while sucrose gave at most 6·8 %. Pollen on media with fructose, galactose, dextrose or lactose failed to germinate. [ABSTRACT FROM AUTHOR]

The Inner Hebridean island of Rhum lies between the once wooded mainland of north-west Scotland and the now largely treeless islands of the Outer Hebrides. Rhum is more exposed than the nearby larger islands and is of particular interest since it has been occupied by humans for at least 8500 years. Pollen, charcoal and radiocarbon studies were carried out on a peat profile from Kinloch in the most sheltered eastern part of the island, some 300 m from the site of the earliest known Mesolithic occupation site in Scotland. From an estimated 7800 BP, the local mire surface was open with some hazel and willow scrub. Alder replaced willow at c. 6500 BP and with hazel, remained the dominant woody vegetation until c. 4000 BP when both were reduced and by which time evidence for agriculture is discernible. A period of reduced Alnus and Corylus between 5950 and 5700 BP, with high concentrations of charcoal, may result from human influence. An Alnus reduction dated to between 5250 and 4950 BP may have been caused by changes in mire hydrology. The woodland was more open than that at nearby mainland sites but it was comparable to well-wooded sites on Skye and Mull. Birch was notably less significant at the Rhum site and the preponderance of Alnus along with persistently high Osmunda values may indicate that adaptation to exposure and salt tolerance were important factors in determining the character of the early postglacial vegetation. [ABSTRACT FROM AUTHOR]

In order to gain an insight into the cellular activities which lead to the inhibition of pollen tube growth following a self-incompatible response, we have been studying the effects of various metabolic inhibitors on pollen - stigmatic extract interactions in vitro. The results indicate that both transcription and glycosylation are required for the full inhibition of pollen tube growth during an incompatible response in Papaver rhoeas. The ability of actinomycin D to partially alleviate an incompatible reaction suggests that during the response, pollen gene expression is induced; we have found that this is indeed the case and have identified novel proteins produced in the pollen which are associated with the incompatibility response. These findings give a clear indication that de novo transcription of pollen genes which are specific to this response, play an important role in the inhibition of pollen tube growth in this species. This provides a significant step towards the elucidation of the mechanism whereby pollen tube growth is arrested following an incompatible reaction in this species. [ABSTRACT FROM AUTHOR]

Transcribing pollen counts from count sheets or mechanical counters into a micro- or mainframe computer is tedious, time-consuming and liable to error. The use of a pocket computer to handle these tasks is described. Similar systems have been available on microcomputers for several years hut the unit cost of microcomputers is too great to allow one on the desk of each pollen analyst in a laboratory. Pocket computers can now be purchased and run for less than the cost of mechanical counters and with considerable advantages for the ease and efficiency of Collecting and handling of palynological data. A program called POLLTAX, running on a Psion Organiser II, designed to collect and handle pollen counts and point count estimates of charcoal, is described. [ABSTRACT FROM AUTHOR]

Pollen-tree correction factors are presented using regression analysis of pre-settlement tree and pollen frequency data from 32 lakes in Wisconsin. Regression results using vegetation samples from various sized areas around each lake for Fagus grandifolia and Tasuga canadensis, are consistent with initial design of using vegetation data for the single township in which a lake was found to compute the regression results. Pollen-tree correction factors from pre-settlement and modern data were compared for all major pollen types. The reconstruction of pre-settlement vegetation was incongruous with measurements of pre-settlement tree frequencies.

Pollen analysis and 14C dating of 5.5 m of organic-rich soil and fluviatile deposits from Newall Creek (altitude 140 m) indicate that temperate rainforest (0-11 K yr B.P.) was preceded by grassland-herbland (11 to 21 K yr B.P.), and then by open grassy Eucalyptus woodland. Comparison with a lake-swamp site at Tullabardine Dam showed that the main vegetation changes were comparable making allowance for some spatial variations in the taxa represented and the lower quantity of pollen in the fluviatile deposits. The inferred sequence of climatic change was from a cool moist interstadial through a cold last glacial maximum to a warm moist Holocene environment, a sequence also indicated at Tullabardine. [ABSTRACT FROM AUTHOR]

Small pollen grains and fine particles of the organic matrix in samples of a coarse detritus mud and a blanket peat deposit were removed by sieving through 30 μm polyester mesh after digestion with KOH and acetolysis during standard pollen pre-treatment. The technique enhanced the number of large pollen grains in the sample. There was also an increase in the range of taxa which produce large grains. The method provided a means of estimating the ratio of any scarce large pollen grain to the total grain sum in samples prepared by standard methods of pre-treatment. [ABSTRACT FROM AUTHOR]

A palynological study of contiguous samples of the upper 128 cm of Carbury Bog, Co. Kildare, Ireland, showed details of the fluctuating human impact on the vegetation during the last c. 850 years. During the period of c. 1130-1440 A.D. the landscape around Carbury Bog was still dominated by forest. During the second half of the 15th century there was a considerable reduction of the forested area, reflected in the Pollen diagram. The commercial exploitation of the forest during the 17th century resulted in almost complete deforestation. The pollen records for the 18th century vegetation show a rise in the curves of Pinus, Fraxinus and Fagus as a consequence of planting of these trees. Apart from pollen many other palynomorphs ('Types' a.o. fungal spores and rhizopods) were recorded. The spectrum of Types appeared to be comparable with the Type spectrum of continental raised bogs. The results of the macrofossil analysis in combination with the indicator values of some Types were used in a detailed reconstruction of the local vegetation succession and the changes in hydrological and trophic conditions. The disappearance of Sphagnum imbricatum during the late medieval period possibly was caused by the increased influx of dust, as a consequence of man's impact on the environment around the bog. The recent importance of S. magellanicum as a peat forming species is possibly the effect of an increased atmospheric deposition of nitrate. Parallel to the analysis of micro- and macrofossils a sample series from the same monolith was analysed for the ratio of the stable isotopes ²H and ¹H. Theoretically the ²/¹H ratio in cellulose of peat-forming plants should be indicative for palaeotemperatures, but, apart from a temperature dependent signal, this ratio is also strongly related to specific characteristics in the isotopic behaviour of different peat forming species. [ABSTRACT FROM AUTHOR]

Percentage and concentration pollen diagrams from the sediments of two adjacent inter-drumlin hollow lakes near Dungannon, and in two cores from Lough Catherine, suggest that only small reductions in the pollen frequencies of trees such as pine and, at some sites, birch and oak, accompanied reduced Ulmus at the elm decline in these parts of Co. Tyrone. They also confirm that Pteridium aquilinum could sporulate and many herbs were able to flower more freely owing to an opening of the tree canopy. Seventeen radiocarbon dates provide chronologies for the sites and date the elm decline to between 5050 and 5375 B.P., the subsequent start of increased elm pollen percentages to between 5010 and 4850 B.P., and the beginning of a second decline in elm pollen to between 4330 and 4260 B.P. The initial decline in elm pollen values may have been caused by disease and this reduction was superimposed upon a background of small-scale clearances which continued after a general elm regeneration. The question of a general similarity and causation of the second elm decline in Ireland and elsewhere is considered. Chemical, magnetic and pollen preservation data from the Co. Tyrone sites suggest episodes of erosion occurring at the first elm decline and others at the second elm decline. [ABSTRACT FROM AUTHOR]

The establishment and expansion of alder [Alnus glutinosa (L.) Gaertner] in Britain between approx. 8000 and 5000 years ago is discussed in relation to changes of climate and sea-level, and to human influences. Detailed pollen analyses of Mesolithic layers at Newferry, Co. Antrim are presented. Evidence from this and other sites suggest widespread disturbance of forest cover which, by locally reducing competition, (cf. McVean, 1956) appears to have been one of the factors in the establishment of alder. Estuarine habitats are suggested as having importance in the spread of alder but the onset of climatic wetness was probably not a key factor (as has often hitherto been supposed) other than in the sense of being permissive. [ABSTRACT FROM AUTHOR]

Pollen analysis of organic sediments in a small hollow at Tarraleah in central Southern Tasmania allows identification of some small-scale patterns and processes within Eucalyptus wet sclerophyll forest during the early to middle Holocene. These events are related to a time scale of inferred ages (i.a.), based on three radiocarbon dates and stratigraphic constraints. Although relatively few tree and tall shrub taxa are involved, changes in relative abundance show that at least five floristically distinctive communities of understorey mesophytes have surrounded the hollow. Prior to i.a. 9125 B.P., subalpine Eucalyptus open forest or woodland formed the local vegetation: (1) Pomaderris apetala - Compositae i.a, 8900 to 8325 B.P. (2) Atherosperma moschatum - Dicksonia antarctica i.a. 8175 to 7775 B.P. (3) Phyllocladus aspleniifolius - (?)Nothofagus cunninghamii i.a. 7625 to 7350 B.P, (4) Pomaderris apetala - sclerophyll shrubs i.a. 7200 to 6925 B.P. (5) Dicksonia antarctica after i.a. 6925 B.P. In most general terms the forest and mire species have behaved consistently with their modern ecological preferences and established trends in Holocene climate. With more detailed resolution, the influence of climate is less apparent and the shifts in community composition more likely to be due to fire frequency and edaphic effects. The results confirm the modern observation that canopy eucalypts and understorey species are only weakly correlated in the presence of fire. Fire has resulted in the separation of Pomaderris apetala communities into two ecological entities but in the absence of fire -- and fire-promoting climates -- during the early Holocene, P. apetala and associated mesophytic small trees may have been able to exclude competitively the canopy eucalypts. Similarly the data indicate early Holocene rainforests may have been enriched with A. moschatum. [ABSTRACT FROM AUTHOR]

Preserved pollen records with small intersample time intervals contain information about many processes in plant population and community ecology. A general approach to the ecological interpretation of these records includes the use of time series statistics, indices that reflect population or community dynamics and models of relevant ecological and sedimentological processes. While the problems inherent in traditional pollen analysis remain, the larger data sets generated by close-interval sampling make it possible to filter out more sampling 'noise' and to obtain a stronger ecological 'signal'. [ABSTRACT FROM AUTHOR]

The modern vegetation of the mountainous Doll Creek region consists of tundra on surfaces above roughly 700 m elevation and spruce woodlands on lower slopes and valleys. Ordination of quadrat cover data by &trended correspondence analysis displays the characteristics and relationships of the vegetation. Tundra on non-calcareous parent materials is distinctive, dominated by Betula glandulosa, Arctostaphylos alpina, Ledum decumbens and Salix arctica. Limestone ridge surfaces, by contrast, support a tundra dominated by Dryas integrifolia, Carex scirpoidea and Cetraria species; lower slopes on limestone are dominated by a Dryas-Cassiope Tomenthypnum cover which also characterizes the ground vegetation of Picea glauca woodlands on lower surfaces. Bottomland mires are dominated by Picea mariana-Sphagnum woodlands and moraines support a Picea mariana-Betula glandulosa-ericad community. Larix laricina shares dominance with Picea glauca at treeline on northwest-facing gulley surfaces where deep and persistent snow appears to be important. A detailed pollen analysis of one site, using percentage and influx diagrams, running means of influx of the main taxa, and a pollen influx-vegetation representation calibration method, reveals that immediately following the maximum of the latest glacial cycle (18000 B.P.) the area supported a sparse, unproductive herb tundra on the lower montane slopes and a sedge-grass marsh complex in poorly drained sites. Between 16000 and 12500 14C years rapid changes in the plant populations occurred, particularly involving species of willow, grass, sedge and herbs. By 12 500 the entire area was occupied by a mosaic of treeless communities in response to a slow amelioration of the climate. [ABSTRACT FROM AUTHOR]

Vegetation history held and to a degree still holds, a central position for a number of strong and persistent reasons. The first reason was that, for a long time, pollen analysis was the best technique available with which to make some kind of quantitative measurement of past events, nothing of a comparable nature was or could be, done with any other kind of fossil or with the materials of geology or archaeology. Another reason was that vegetation cover reflects, to some extent at least, aspects of the physical environment of a place or the stresses put upon it by human activities.

Pollen analyses of post-glacial sediments from the marine Lough Ine and freshwater Ballyally Lough are described. Lough Ine was found to have been formerly a freshwater basin. The oldest sediments, banded clays with no microfossils, were probably glacial outwash deposits. These were overlain by post-glacial sediments; late-glacial deposits were missing. By comparison with radio-carbon-dated diagrams from other sites the marine transgression is tentatively dated at c. 4000 B.P. The lowest sediments from Ballyally Lough can be assigned to Mitchell's zone VI, the Boreal period. The post-glacial vegetational development of both loughs and the surrounding area is discussed. [ABSTRACT FROM AUTHOR]

The vegetational history of Crose Mere, north Shropshire, is reconstructed by means of pollen analysis, lithostratigraphy and radiocarbon dating. Pollen diagrams from a core representing the Flandrian and Late Devensian are presented. Eleven radiocarbon dates were obtained from the Flandrian and these allowed the estimation of pollen deposition rates from pollen concentrations. The pattern of vegetational changes shows close similarities with those from the lowlands of north-west England notably the appearance of Pinus sylvestris after Corylus avellana, Ulmus and Quercus in the forest succession. The effects of man on the environment are traced and four main agricultural episodes are distinguished after the 'elm decline' at about 5300 B.P. Comparison of pollen percentage and absolute data highlights the problem of interpreting pollen deposition rates from a basin with uneven sedimentation and the possibility of resuspension of freshly deposited sediments. [ABSTRACT FROM AUTHOR]

Pollen originating from small populations of Tilia cordata is largely deposited within a few hundred metres of the trees, so that their presence can only be detected by pollen analysis at sites within distances of this order. Pollen diagrams from such sites show a continuous curve for Tilia pollen extending to the present surface, although the values may be only about 1% of arboreal pollen. Pollen analysis shows that T. cordata was present in the Lake District by about 5000 to 4800 B.C.; it then became plentiful in the southern valleys and extended to reach its present north-western limit, or just beyond, by 3100 B.C., when migration ceased. While the tree was extending its range, it must have been able to produce frequent large crops of fertile seed but subsequently regeneration from seed ceased. After 3100 B.C., the proportion of its pollen initially may increase but then generally decreases. Although there are small recoveries at several horizons, these are not certain evidence of reproduction by seed. Failure to produce fertile seed renders the species particularly sensitive to woodland clearance and has resulted in a decrease in abundance within the Lake District and its virtual extinction in west Yorkshire and south Lancashire. [ABSTRACT FROM AUTHOR]

Pollen analysis of sediment at a site on the eastern side of Wilsons Promontory (southern Australia) privides a record of the vegetation from about 13000 B.P. to the present. A Eucalyptus forest was present on the site at first, but was replaced by a Melaleuca scrub or thicket about 11000 B.P., probably reflecting a rise in the watertable. As the sea was at least 6 km distant, this event may mark increasing rainfall near the start of the Holocene. The arrival of the sea close to the site about 7000 years ago is demonstrated by changes from a freshwater swamp to saline salt marsh, followed by succession to the low scrub swamp of the present. Regionally, the Nothofagus rainforest, which is now restricted to small isolated stands on high parts of the promontory, expanded between 11 000 and 7000 B.P. This forest is now more extensive than at 11000 B.P. but has contracted relative to the mid-Holocene extent. From this it appears that the climate of this region during the mid-Holocene was slightly wetter than that of the early or late Holocene. The later half of the record is in agreement with other work from the western side of Wilsons Promontory. [ABSTRACT FROM AUTHOR]

Stratigraphic and pollen evidence is presented from a mire site on the eastern side of the main Cambrian watershed of central Wales. A complex basin contains Late Devensian lake sediments overlain by Flandrian organic detritus muds. Organic lake muds were replaced by swamp and can vegetation on the north and west of the site, but the south-east basin continued as a lake until relatively recent tunes (the last 200 years). Final colonization of the lake was by a floating raft of Carex rostrata, Menyanthes trifoliata and Sphagnum cuspidatum, on which the present Sphagnum-dominated vegetation has developed. Such schwingmoor mire types are uncommon in Britain and this is a particularly good example. Pollen analysis of the Flandrian lake sediments provides information concerning vegetational history. Interesting early Flandrian records are of Hippophäe rhamnoides, Linum bienne and Fumaria. Pinus sylvestris has low pollen levels in the early Flandrian, unlike many western sites. It is suggested that sites having high values may have Pinus as a local mire colonist. The Ulmus decline is very marked and is accompanied by evidence of cultivation. This is the first evidence of cereal growing in early Neolithic times in Central Wales. Higher in the profile Cannabis sativa assumes importance, possibly as a result of Iron Age/ Roman cultivation. [ABSTRACT FROM AUTHOR]

Laboratory tests were made on three absolute pollen preparation techniques previously published by Davis (1965, 1966), Matthews (1969) and Jorgensen (1967), and on an additional weighing method (Modified Jorgensen) using both standard pollen suspensions and fossil minerogenic samples. Laboratory procedure is described and the following results include an investigation of grain distribution within slides prepared by the Jorgensen and Matthews methods, a discussion of the statistical reliability of the Jorgensen method, and a test of the vane ability attributable to preparation methods, using the coefficient of variation (C.V) as the basis of comparison. The relation between grain loss (bias) during the preparation procedure, the methods employed, and the sediment type used is explored, and some practical aspects of the various techniques are considered, It is concluded that for detailed palynological work, particularly in conjunction with 14C dating, the extra time needed in the preparation of the Davis or the Modified Jorgensen methods is balanced by a greater reliability of result The Matthews and Jorgensen techniques are shown to he adequate for determination of large scale changes in pollen concentration, though all methods would benefit through the addition of an 'exotic' pollen type in order to detect losses during preparation. [ABSTRACT FROM AUTHOR]

Comparison of pollen diagrams is an important stage in pollen analytical Investigations as it is the basis for the recognition of regional pollen assemblage zones. Three numerical approaches to the problem of comparing stratigraphical sequences are presented. Their use is illustrated by two contrasting sets of data, one from two sites of Late-Wisconsin age in central Minnesota, the other from a transect of sites in north-west Minnesota extending from Late-Wisconsin to present times. The first approach compares pollen zones at the different sites on two numerical criteria, information radius and concordance. The other two approaches compare sequences on a level-by-level basis; the second method by means of non-metric multidimensional scaling and the third by a slotting procedure by which levels at one site are slotted between levels at another site on the basis of similarities in pollen composition. The advantages and disadvantages of the three approaches are discussed. [ABSTRACT FROM AUTHOR]

Investigations into former lake basins in the region to the north of Capel Curig (SH 721581) in Caernarvonshire have revealed deposits of Late-glacial age. Pollen analysis of the deposits permits subdivision of the sequence into the standard Late-glacial zones I, II and III together with some sub-zones based upon recurring pollen assemblages. Some of the ecological implications of these assemblages are discussed, in terms of vegetation, climate and soils. High Rumex pollen values characterize pollen zone I. A wide range of herbs and Betula pollen dominate in zone II. Zone III is characterized by high Artemisia pollen values. A transition zone III-IV is included to cover the Empetrum and Juniperus pollen peaks, prior to the rapid rise in Betula pollen values in zone IV. [ABSTRACT FROM AUTHOR]

The concept of the pollen zone as a fossil assemblage zone is discussed, and the advantages of numerical approaches to the recognition and delimitation of such zones are considered. Existing procedures are reviewed, and original constrained agglomerative and divisive procedures are advanced. The results of these procedures are discussed in relation to existing zonation schemes for three sets of data, and the limitations and potentialities of the procedures are considered. The initial zonations suggested by visual inspection are, in general, confirmed by the numerical procedures. The application of these procedures to the subdivision of both pollen and macro-fossil data in the same stratigraphical sequence is also discussed. Details are given of the computer time and storage required for the analyses. [ABSTRACT FROM AUTHOR]

Pollen analysis has been conducted upon a mire site at an altitude of 312 m on the Mynydd Bach region of western Cardiganshire. The sediments subjected to analysis began forming at the close of the post-Allerød cold phase (zone III sensu Godwin) and document vegetational history in the area up to the time of the elm decline, after which deposits appear to have suffered interference by peat cutting. A number of the features present at this westerly site are of particular interest, especially the early rise of Corylus in the Flandrian. Corylus pollen (expressed as % arboreal pollen) began to rise at this site before the zone III/IV Juniperus peak. As one moves progressively north in western Britain, so the Corylus rise is delayed until well after the juniper peak. This time lag is considered to reflect the migration rate of Corylus as well as offering an opportunity to trace its route up the western edge of Britain, gradually extending eastwards and into regions of higher altitude. Pine values are low at Gwarllyn throughout the early Flandrian, in contrast to the upland areas of Cardiganshire, where pine increases to a maximum an zone Vic. It is postulated that Pinus was less successful in the western lowlands as a consequence of the greater competitive ability of Quercus under the prevailing climatic and edaphic conditions in those regions. [ABSTRACT FROM AUTHOR]

The fluorescence of fossil pollen and spores changes in colour and intensity with increasing age. By a study of Ipswichian Interglacial and Lower Pleistocene samples, it is shown that it is possible to distinguish Pleistocene from earlier pollen and spores by their different fluorescence colour and to a lesser extent by their different fluorescence intensity. The method can be employed in solving various problems of derivation in Pleistocene palynology. [ABSTRACT FROM AUTHOR]

The constituents of a normal monoecious fig, namely the male and female flowers, the short- and long-styled female flowers and the male and female wasp galls, are arranged in definite spatial and numerical relations. The normal development of the syconium depends on a balance of these different elements. Occasionally various types of aberrant figs are found in nature, differing from normal figs in development and in final structure. These are purely gall figs, seed figs and male wasp or female wasp figs. Such abnormal figs were obtained experimentally by introducing specially treated female wasps into receptive young syconia at the receptive B phase. Treatments of the wasps involved one of the following: shortening of their ovipositor, preventing contact of wasps with pollen, preventing wasp fertilization or their sterilization by irradiation with gamma rays at various doses. In some of the already inhabited figs, the wasp larvae were killed by insecticidal sprays. Analysis of the development and structure of naturally-found aberrant syconia, taking into account also the conditions under which they may be produced experimentally, provides data for elucidating various aspects of the mutualistic symbiosis in figs. [ABSTRACT FROM AUTHOR]

Analysis of a large number of fossil pollen grains of Tilia from the East Anglian Fenland, led to examination of the characters that might be employed to separate T. platyphyllos from T. cordata. Certain characters were discarded but mesh structure and size in surface reticulation, characters since accepted by other authors, were regarded as satisfactory and made the basis for classifying fossil grains. The results indicated native British status for both species of lime from pollen-zone VIIa onwards, with T. cordata much the commoner, and very high relative frequencies of Tilia pollen in zone VIIa and diminution zone by zone thereafter to levels below 0.5% of total tree pollen. [ABSTRACT FROM AUTHOR]

Comparisons of pyrene set were made between raspberry flowers pollinated with undiluted pollen and others pollinated with pollen diluted with talc, or killed pollen. Pollen dilution reduced set but the reduction was not the same for all maternal parents. It also reduced the rate of fruit ripening, increased the proportion of pyrenes without seed content and reduced the tendency for abortive carpels to develop into small empty pyrenes. Observations of numbers of pollen grains germinating in the styles revealed differences attributable to the maternal parents, the pollen germinating poorest on the parent whose pyrene set was reduced most by pollen dilution. There were also maternal × paternal interaction effects on pollen germination. It is concluded that pollen germination was conditioned by growth substances provided partly by the grains themselves and partly by the styles of the seed parent, and that there were interactions between the two sources. Reduction in pollen concentration affected several aspects of early fruit development, but quantitative differences in the amount of pollen applied did not reduce the adverse effects of using diploid pollen. This suggests that such effects do not arise through direct action of the pollen on the maternal tissues. [ABSTRACT FROM AUTHOR]

The article presents a discussion on zonation of pollen diagrams in relation to the necessity for correct biostratigraphical subdivision. It also presents an outline of a process of correlation of pollen diagrams to a chronostratigraphical framework. Pollen diagrams have been constructed from Pleistocene deposits in many parts of the world. A pollen diagram is a biostratigraphical record related to a period of time. The zones are ascribed to particular times and then their pollen characteristics were described.