Leaf epidermis morphological differentiation between Tamarix africana Poir. and Tamarix gallica L. (Tamaricaceae) with ecological remarks

Abstract

Recent work, based on morphological and cytotaxonomical information, claimed the independence of Plantago brutia Ten., a narrow endemic of South Italy, with respect to Plantago media L. Here, we present a further evaluation of the systematic relationships occurring between these two taxa as revealed by molecular studies. We sampled P. brutia in most of the known populations and P. media in several European stands, from Sweden to the Iberian Peninsula and Balkans. We then investigated the relationships among the sampled populations by using as molecular markers the internal transcribed spacer regions ITS1 and ITS2. Furthermore, we considered cpDNA to gain further insight into the relationships among P. brutia/P. media populations. Based on nrDNA data, P. brutia appeared to be nested within the P. media complex, but as a well distinct subunit. This is congruent with a subspecific rank for this taxon within P. media. The cpDNA revealed the occurrence of several haplotypes in the studied material. Most of the assessed haplotypes were exclusive for single populations and thus phylogenetically uninformative. Nonetheless, we have found some haplotypes that are shared by different cytotypes or populations throughout the species range, suggesting possible explanations for the phylogenetic relationships occurring between P. brutia and the autopolyploid complex P. media.     

Nitrate production in the rhizosphere of Plantago species

Summary The production of nitrate in an old established dune grassland soil and its uptake by plants was studied by comparing amounts of mineral nitrogen and numbers of nitrifying bacteria in the rhizosphere on the one hand, and on the other accumulated nitrate and levels of nitrate reductase (NaR) of individual plants of three Plantago species,i. e., P. major, P. lanceolata andP. coronopus. For these three Plantago species andP. media basal levels of NaR in the absence of nitrate were determined in plants grown in culture solutions. The basal NaR levels ofP. major andP. media (species occurring on nutrient-rich soils) were significantly higher than those ofP. lanceolata andP. coronopus (species found on nutrient-poor soils). NaR activity increased in the presence of nitrate and was suppressed by ammonium.From the numbers of nitrifying bacteria in the rhizosphere and NaR activity in the leaves it was concluded that nitrate was produced in the root environments of the three Plantago species and that the compound was taken up by the plants. NaR activities and numbers of nitrifying bacteria were higher for individuals ofP. major than for those ofP. lanceolata andP. coronopus. No correlation was found between the ammonium levels and the numbers of nitrifying bacteria in the soil, and no indications of inhibition of nitrifying bacteria in the rhizosphere were obtained. For individuals ofP. lanceolata a correlation was found between the numbers of nitrifying bacteria in the soil and NaR activity in the leaves. The results are discussed in relation to the ecological habitats of the three species.Grassland Species Research Group Publication No.38.     

Regulation of root respiration in two species of Plantago that differ in relative growth rate: the effect of short- and long-term changes in temperature

This study investigates the effect of short‐ and long‐term changesin temperature on the regulation of root respiratory O₂ uptakeby substrate supply, adenylate restriction and/or the capacityof the respiratory system. The species investigated were the lowland Plantagolanceolata L. and alpine Plantago euryphylla Briggs, Carolin& Pulley, which are inherently fast‐ and slow‐growing, respectively. Theplants were grown hydroponically in a controlled environment (constant23 °C). The effect of long‐term exposure to lowtemperature on regulation of respiration was also assessed in P.lanceolata using plants transferred to 15/10 °C(day/night) for 7 d. Exogenous glucose and uncoupler (CCCP)were used to assess the extent to which respiration rates were limitedby substrate supply and adenylates. The results suggest that adenylatesand/or substrate supply exert the greatest control overrespiration at moderate temperatures (e.g. 15–30 °C)in both species. At low temperatures (5–15 °C),CCCP and glucose had little effect on respiration, suggesting thatrespiration was limited by enzyme capacity alone. The Q₁₀ (proportionalincrease of respiration per 10 °C) of respirationwas increased following the addition of CCCP and/or exogenousglucose. The degree of stimulation by CCCP was considerably lowerin P. euryphylla than P. lanceolata. This suggeststhat respiration rates operate much closer to the maximum capacity in P.euryphylla than P. lanceolata. When P. lanceolata wastransferred to 15 °C for 7 d, respirationacclimated to the lower growth temperature (as demonstrated by an increasein respiration rates measured at 25 °C). In addition,the Q₁₀ was higher, and the stimulatory effectof exogenous glucose and CCCP lower, in the cold‐acclimated rootsin comparison with their warm‐grown counterparts. Acclimation of P.lanceolata to different day/night‐time temperatureregimes was also investigated. The low night‐time temperature wasfound to be the most important factor influencing acclimation. The Q₁₀ valueswere also higher in plants exposed to the lowest night‐time temperature.The results demonstrate that short‐ and long‐term changes in temperaturealter the importance of substrate supply, adenylates and capacityof respiratory enzymes in regulating respiratory flux.     

Anti-mitotic and anti-genotoxic effects of Plantago lanceolata aqueous extract on Allium cepa root tip meristem cells

Plantago is the most important genus of Plantaginaceae family and is used in traditional medicine around the world for different purposes. Plantago coronopus L., Plantago major L., Plantago media L. and Plantago lanceolata L. are most commonly used species of Plantago in traditional medicine in Turkey. The main goal of this study was to investigate the eventual anti-mitotic and anti-genotoxic effects of P. lanceolata L. leaf aqueous extracts (15 g/L and 30 g/L) on Allium cepa L. root tip meristem cells which were treated with 0.7% hydrogen peroxide. For this purpose, two different experiments were performed under the same conditions. In the first experiment, Allium cepa onion bulbs were treated with 0.7% H₂O₂ for 1 h. After the H₂O₂ treatment, the onion bulbs were treated with two different concentrations (15 g/L and 30 g/L) of P. lanceolata extracts for 24 h. In the second experiment, A. cepa onion bulbs were treated with two different extract concentrations (15 g/L and 30 g/L) for 24 h and then with 0.7% H₂O₂ for 1 h. The test concentrations were determined according to doses which are recommended in alternative medicinal usage by people. As positive and negative control 0.7% H₂O₂ and tap water was used, respectively. As a result, it was determined that aqueous extracts reduced mitotic index and chromosome aberrations in treatment groups in comparison with controls. These results showed that P. lanceolata aqueous extracts have anti-mitotic and anti-genotoxic effects.     

The effect of nitrate concentration in a flowing solution system on growth and nitrate uptake of twoPlantago species

Summary Juvenile plants ofPlantago lanceolata andP. major ssp.major were grown in a flowing solution system at 7.5 mM or 9.5 M NO₃. The parameters investigated were: RGR, shoot weight percentage, leaf length, length of main root axis, shoot concentrations of major ions and organic N, and the specific uptake rate for NO₃. At 9.5 M NO₃ growth ofP. major was not hampered, whereas shoot growth and leaf length ofP. lanceolata were reduced. The NO₃ concentration ofP. lanceolata decreased more than that ofP. major. The different performances of the species at 9.5 M NO₃ were associated with different specific uptake rates. In both treatments the root system ofP. major was shorter than that ofP. lanceolata. P. lanceolata accumulated more NO₃ in the leaves. The performance of thePlantago species is discussed in relation to the availability of nutrients in their habitats.Grassland Species Research Group. Publication no. 37.     

Ca2+ and Mg2+-Stimulated ATPases from Roots of Plantago lanceolata, Plantago media and Plantago coronopus: Response to Alterations of the Level of Mineral Nutrition and Ecological Significance

Growth of Plantago lanceolata L., P. media L. and P. coronopus L. was followed at two levels of mineral nutrition (low-salt and high-salt). In addition the response of transfer of plants from low-salt conditions to high-salt conditions and vice versa was studied. Growth of these Plantago species was not much affected by the nutritional level. P. coronopus showed the least dependence on the level of mineral nutrition. The Ca²⁺- and Mg²⁺-stimulated ATPase activity of microsomal preparations of the roots of Plantago was also studied. A pH optimum at pH 6.5 was observed in all species, together with a relatively high ATPase activation by Mg²⁺ in P. lanceolata, by Ca²⁺ in P. media, and by both ions in P. coronopus. The specific activity of the ATPases was highest in preparations from low-salt roots. The three species all occur in relatively nutrient-poor habitats, but they are at the same time particularly adapted to circumneutral soils (P. lanceolata), to Ca²⁺-rich soils (P. media) and to alternating levels of mineral nutrition (P. coronopus). The properties of the ATPases (K_m, V_max, protein content) and the growth are discussed in relation to these ecological properties of the species.     

On the Holocene vegetation history of the Argive Plain (Peloponnese,southern Greece)

Palynological investigations have been carried out on a sediment core from ancient Lake Lerna, a former fresh water lagoon in the western part of the Argive plain, Peloponnese, southern Greece. The sequence starts at 6800 B.P. (5700 cal B.C.). The lowest part of the pollen diagram shows a period of open deciduous oak woods, which may have been influenced by human impact already (Zone I). It is followed by a period of dense deciduous oak woods (Zone II), which lasted until the beginning of the Bronze Age ca. 4800 B.P. (3500 cal B.C.). Later, the diagram indicates strong human influence such as woodland clearance, the spread of maquis, phrygana and pine in Zones IIIa-IV. During the Archaic, Geometric and Classical periods after ca. 2700 B.P. (800 cal B.C.) there is evidence of a phase of extensive olive farming (Zone IIIb). In the same zone, after a period of scattered finds, there is an almost continuous Juglans curve. Zone IV is characterised by high pine values. In Zones I-II the evidence of evergreen Mediterranean plants is surprisingly small. In times with no discernible human influence (Zone II), deciduous oaks dominate, with no evidence for a climax vegetation of the Oleo-Ceratonion alliance. Olea europaea is the only species of that alliance traceable by its pollen in the diagram, while Ceratonia pollen is totally absent.     

Polymorphic microsatellite loci in Plantago lanceolata

The genus Plantago is particularly interesting for evolutionary studies because of its wide range of mating systems. We have developed primers for five highly polymorphic microsatellite loci isolated from P. lanceolata. All five loci amplified and were polymorphic in the two populations examined, Lowsteads Beach in the United Kingdom and Duke in the United States. These new markers will allow a comparison of population structure between the outcrossing species P. lanceolata, and the highly selfing species P. major.     

Herb pollen representation in surface moss samples from mown meadows and pastures in western Norway

Grazed and mown vegetation types in western Norway were investigated with the aim of describing their modern pollen/vegetation relationships as an aid to the interpretation of fossil pollen diagrams. Pollen surface samples and vegetation data were obtained from 186 square metre plots within 39 different sites of 10×10 m. Scatter plots that show the relationship between pollen percentages and vegetation percentages are presented forTrifolium pratense-type,Trifolium rcpens-type,Lotus, Campanula-type,Succisa, Ranunculus acris-type,Cirsium-type, Asteraceae Cichorioideae,Achillea-type,Potentilla-type, Apiaceae,Rumex sect.Acetosa, Galium-type, Cyperaceae,Calluna, Plantago lanceolata and Poaceae. Pollen representation factors relative to Poaceae (R_rel) are calculated for 54 pollen taxa. Differences in the values from different geographical areas were found in the case of some taxa, due to either different genera or species being included in the pollen taxa and/or to the different representation of high pollen producers in the different regional vegetation types. Background pollen influences the estimates for taxa such asR. sect.Acetosa, P. lanceolata, Poaceae, Cyperaceae, andCalluna, and an extended R-value (ERV) model was used to investigate the magnitude of this pollen component. Groups of roughly similar pollen representation were identified and factors to convert pollen percentages to vegetation abundances are suggested.     

Long-term human impact as registered in an upland pollen profile from the southern Black Forest, south-western Germany

A detailed,¹⁴C-dated, pollen profile from Steerenmoos, a raised bog in the uplands of the southern Black Forest (Schwarzwald) is presented. The Late-glacial and early Holocene vegetation history conforms to the known pattern of forest dynamics for that region. At ca. 6100 cal. B.P.,Abies replaced the mixed oak forest, which is in contrast to adjacent regions whereFagus spread beforeAbies. From the Subboreal onwards,Fagus expanded and slowly largely replacedAbies. The mire developed from a fen to a raised bog. The mountain pine (Pinus mugo ssp.rotundata) on the present-day bog surface is a result of medieval burning. Cereal pollen are first recorded in the Neolithic (7600 cal. B.P.) and there is a closed curve forPlantago Lanceolata — a good indicator of human impact — since the Bronze Age (4000 cal. B.P.). On the basis of the cereal pollen record nine human impact phases (HIP) are described. HIP 1 and 2, which are short, date to ca. 7600 and 6700 cal. B.P., respectively, in a mixed oak forest context and are characterized by declines inCorylus, Tilia, Ulmus and bySalix (but no major deforestation) and peaks in charcoal and loss-on-ignition curves. HIP 3 and 4, which are short and weak, date to ca. 6000 and 5300 cal. B.P., respectively, and occur in the context of anAbies alba forest. The Bronze Age and Iron Age HIPs 5-7 are more intense and of longer duration than the Neolithic phases and result in a decline inAbies and an increase inFagus. The early medieval HIP 8, although rather weak, probably finds expression also in an archaeological artefact, namely a dug-out boat from the near-by Schluchsee. Finally, the late Medieval HIP 9 resulted in a major transformation in the landscape. It is argued that the earlier HIPs are not a reflection of distant events in the lowland valleys of the Rhine, Danube or Neckar but reflect more or less local developments.     

Archaeobotanical evidence for early agriculture at Ljubjansko barje (Ljubljana Moor), central Slovenia

Archaeobotanical evidence is presented for early agriculture at southwestern Ljubljansko barje (Ljubljana Moor), Slovenia. Archaeobotanical finds from the Eneolithic site at Hočevarica, and pollen records from an archaeological profile and from a nearby core were analysed. Numerous charred grains of cultivated cereals together with fossil seeds of Chenopodium sp. demonstrate that during the occupation of the settlement at Hočevarica, agriculture was well established. The majority of identified grains were of Hordeum vulgare (cultivated barley) and the rest were Triticum monococcum and T. turgidum ssp. dicoccum (cultivated wheats). Large amounts of cereal pollen and pollen of Chenopodiaceae also suggest strong human impact on the surrounding vegetation and landscape. Pollen and archaeobotanical data from Hočevarica show a large consistency in timing of the appearance of agriculture. In the pollen record from the core at Hočevarica a significant increase (up to 40%) in cereal pollen was detected at 4881 ± 50 B.P. (3770-3630 cal B.C.). Charred cereal grains were dated to 4800 ± 40 B.P. (3650-3520 cal B.C.). The grains of cultivated cereals from Hočevarica represent the oldest archaeobotanical evidence for agriculture in central Slovenia. Received February 18, 2002 / Accepted October 21, 2002     

The effect of salinity on lipid composition and on activity of Ca2+- and Mg2+-stimulated ATPases in salt-sensitive and salt-tolerant Plantago species

Lipid composition of the roots and the shoot of the salt-sensitive Plantago media L., the salt-tolerant P. maritima L. and the less salt-tolerant P. coronopus L. was followed under saline conditions. In the roots of P. media the level of phospho-, galacto- and sulpholipids decreased strongly with increased NaCl concentration, indicating decreased control of permeability of the root cell membranes. In the roots of the two salt-tolerant species the level of most lipid classes was maintained or even raised up to 75 mM NaCl, and a decrease was noted only at higher NaCl concentrations. In P. maritima, a species from relatively nutrient-rich habitats, decreased lipid levels in the roots and shoot were observed with increasing salinity in combination with a low nutrient availability. The Ca²⁺- and Mg²⁺-stimulated ATPase activities of the microsomal fraction of the roots of P. maritima was decreased at a salinity level in excess of 150 mM, while in P. coronopus they were decreased at all NaCl levels tested. The obtained results are discussed as part of the adaptation of the species to salinity.     

Reconstruction of environment and history of plant use during the late Mesolithic (Ertebølle culture) at the inland settlement of Bökeberg III,southern Sweden

Pollen, plant macrofossils and charcoal were analysed from a lake-sediment sequence, including a refuse layer, from the Late Mesolithic settlement at Bökeberg III, southern Sweden. The chronology was established by means of AMS-dated plant macroremains. The results of the biostratigraphical studies indicate two settlement phases (A and B), at ca. 6650-6400 B.P. (5560-5320 cal. B.C.) and ca. 6150-5800 B.P. (5200-4680 cal. B.C.), respectively. The two settlement phases are associated with periods of low lake-level contemporaneous with the second major period of low lake levels during the Holocene in southern Sweden, and thus with a period of generally drier climate. The pollen analytical data suggest only minor human impact on the local vegetation during the two settlement phases. Three elm declines at ca. (1) 6200 B.P. (5200-5100 cal. B.C.), (2) 5450 B.P. (4340 cal. B.C.), and (3) 5150 B.P. (3980 cal. B.C.) are discussed. Elm decline 3 is synchronous with the classical north-west European elm decline. Elm declines 2 and 3 may be due to outbreaks of elm disease rather than to strong human impact or climate change. The charcoal analyses show that wood of a wide range of species was collected for fuel or other purposes. During phase A, plants used included acorns, hazelnuts and, possibly, Cornus sanguinea, and also Prunus spinosa, Sorbus aucuparia and Rubus idaeus. There is convincing evidence that Cladium mariscus was used for thatching. The second occupation phase, B, is characterised by the use of hazelnuts for food. The possible use of several other identified species is discussed.     

The role of human disturbance in Late Holocene vegetation changes on Kullaberg, southern Sweden

A pollen record from a small peatland located on Kullaberg in northwestern Sk?ne, southern Sweden, revealed that grazing pressure might have been the major disturbance agent controlling the vegetation, at least from ca. 1500 B. C. until the latter part of the nineteenth century. The pollen data also indicate a step-by-step increase in grazing pressure, expressed as a marked increase in non-arboreal pollen representation at ca. 1500 B. C., A. D. 650 and A. D. 1650. The increase at A. D. 650 probably indicates a more regular and intensive use of the area, resulting in a forest structure that was much more open than earlier, together with an expansion of Fagus, which rapidly replaced Quercus as the local forest dominant. At about this time the first patches of heath vegetation originated, but they probably only covered a small part of Kullaberg. Larger areas with an intensively grazed Calluna heath, as shown by eighteenth century maps, probably evolved around ca. A. D. 1650, when much of Kullaberg seems to have been deliberately deforested. Received February 20, 2001 / Accepted September 12, 2001     

Genetic variability in Plantago species in relation to their ecology

Summary Populations of the three Plantago species P. major, P. lanceolata and P. coronopus were scored for allozyme variability. They showed normal variability levels compared with other, similar plant species. Differentiation among populations appeared to be rather low in comparison with other species, probably due to a considerable amount of long distance seed transport. In order to be able to make an analysis of small-scale gene flow, all (sub)populations were critically checked for the existence of population structure equilibrium. The allozyme variation was tested for neutrality by testing homogeneity of F values among loci: between populations (Lewontin-Krakauer test) and within populations. No systematic deviations from the prediction of the neutral theory could be established. From the population structure analyses, little gene flow in the species P. major (with high selfing levels) and P. coronopus could be concluded, whereas P. lanceolata showed relatively high levels of gene flow. The degree of homozygosity in the latter species was too high to explain with the available data. In P. coronopus, on the other hand, an unusually high number of heterozygotes were observed.Grassland Species Research Group Publication No. 73     

Airborne pollen data of Platanaceae in Santiago de Compostela (Iberian Peninsula)

The pollen count of the Platanus genus in the atmosphere of Santiago de Compostela (Galicia, Spain) was carried out from 1993 to 1998, with the pollen of this taxon representing 6% of total identified pollen. The principal pollination period (P.P.P.) was centred on the months of March and April, with an average duration of 23 days.During the study period we obtained negative correlations with precipitation and humidity and positive ones with temperature and hours of sunshine, with a confidence index of more than 90%. On the basis of the six-year study period, we also calculated the average accumulated temperature required to trigger the onset of flowering, which oscillated between 330 and 456 °C, with this result being confirmed for 1999 (437 °C). We also observed that the values of maximum pollen concentration of this taxon in the last 7 years (1993–1999), were obtained on days during the P.P.P. with maximum temperatures above 18 °C. The model of intradiurnal variation reflects, for the majority of years, a greater representation during the central hours of the day.     

Holocene vegetation and land-use history in the environs of Lake Kahala, northern Estonia

Pollen profiles, based cores taken in Lake Kahala and from the adjoining mire, were used to establish general vegetation history and to reconstruct the extent and types of land-use over most of the Holocene. Modern pollen deposition was studied using moss polsters and the results were used in the interpretation of the fossil pollen data in terms of former land-use practices. The modern-day samples are from settlements, hay meadow and pasture, and overgrown pasture. Indications of human activity can be traced back to the Stone Age. At ca. 6400 cal. B.C., the first indications of possible woodland utilisation by humans are recorded. This may have involved grazing within the forests. From 4200 cal. B.C. onwards, animal husbandry with changing intensity was practised. Arable farming, involving cereals, was introduced to the area at ca. 1800 cal. B.C., but it was only at ca. 500 cal. B.C. that it assumed an important role in the farming economy.Secale cereale (rye) was introduced during the Roman Iron Age, intensive rye cultivation started at the end of the Iron Age, at ca. cal. A.D. 800. Ever increasing farming pressures triggered the formation of openalvars. Open landscape similar to that of today has persisted, with minor forest regeneration phases, since at least 500 cal. B.C.     

POLLINATION ADAPTATION IN PEDICULARIS LANCEOLATA

Cinematographic, stereophotographic, and visual observations have revealed that the zygomorphic, nectarless flower of Pedicularis lanceolata Michx. is pollinated in northeastern Ohio by pollen-foraging workers of three Bombus species. Foragers hang inverted from the asymmetrical corolla and remove pollen with their front and middle legs from anthers concealed by the galea. The stigma contacts pollen deposited especially on the median portion of the forager's first abdominal sterilite. Insect exclosures and pollinator collections demonstrated the obligate pollination dependence of the flower on Bombus workers. Of 152 corbicular pollen loads from workers foraging on P. lanceolata, Gentiana andrewsii, Prunella vulgaris and five composite species in the same habitat, 84.2% contained P. lanceolata pollen; 75.8% of the latter contained P. lanceolata pollen exclusively. Possible coadaptive relationships of Pedicularis flowers and pollinators are discussed.     

Modern pollen–vegetation relationships along transects on the Whangapoua Estuary, Great Barrier Island, northern New Zealand

Aims To quantify pollen–vegetation relationships from saline to freshwater in an estuarine gradient from surface samples of the modern pollen rain, to allow more accurate interpretations of the stratigraphic palynological record. Location Whangapoua Estuary, Great Barrier Island, northern New Zealand. Methods Six transects were laid out along a vegetation sequence running from estuarine mud to freshwater swamp. Along these transect lines, 108 plots were sampled for vegetation and surface sediments from wet sand, mud, plant litter or moss (sand and mud sites are inundated by most tides, other sites less frequently). All sediment samples were analysed for pollen. The relationships between plant species frequency and pollen representation were examined at a community scale using twinspan and ordination analyses, and for individual species using fidelity and dispersibility indices, regression and box‐plot analyses. Results The quantitative relationships between source taxon vegetation frequency and its pollen representation varied between species due to differential pollen production and dispersal. twinspan of the surface pollen samples suggests five vegetation types: (A) mangrove (Avicennia marina); (C) Leptocarpus similis salt meadow; (D) Baumea sedges; (E) Leptospermum shrubland; and (F) Typha/Cordyline swamp forest. The (B) Juncus kraussii community is not represented palynologically owing to the destruction of its delicate pollen grains during acetolysis of samples. Detrended correspondence analysis places these communities on an estuarine‐to‐freshwater gradient. However, pollen assemblages at the seaward end of the salinity gradient are less clearly representative of the associated vegetation than those at the landward end, probably because the open vegetation at the former allows the influx of wind‐ and water‐dispersed pollen from surrounding vegetation. Main conclusions The vegetation pattern (zonation) at Whangapoua is reflected in the pollen rain. When the long‐distance and over‐represented pollen types are excluded, five out of six of the broad vegetation communities can be identified by their pollen spectra. Species with high fidelity and low‐to‐moderate dispersibility indices can be used to identify the vegetation types in the sedimentary sequences. The more open vegetation types at the ‘marine end’ of the sequence tend to be ‘overwhelmed’ by regional pollen, but the nature of the sediments and the presence of discriminatory species (e.g. A. marina, Plagianthus divaricatus, Cordyline australis), even in small amounts, will allow correct identification of the local vegetation represented in sedimentary palynological sequences. A box‐plot analysis indicates that the pollen and spore types A. marina (mangroves), Sarcocornia quinqueflora (salt meadow), P. divaricatus (sedges), Gleichenia (shrubland) and C. australis (swamp forest) are highly discriminatory in relation to vegetation type. These discriminatory palynomorphs help with the interpretation of stratigraphic pollen studies. However, salt marsh vegetation communities in the sediments must be interpreted with caution as the marine sediments are easily affected by erosion, bioturbation and tidal inundation effects.     

History of vegetation and land use from 3200 B.P. to the present in the north-west Burren,a karstic region of western Ireland

A radiocarbon-dated pollen profile provides the first evidence for the vegetation history of the north-west Burren, a karstic region in Co. Clare, western Ireland. The profile, which spans the period ca. 3200-0 B.P., shows that Corylus was the main woody species and that, apart from the later eighteenth and nineteenth centuries, when woody species were almost totally cleared, it constituted a more important element in the landscape than at present. The data indicate that small populations of Quercus, Fraxinus, Betula, Alnus and possibly Ulmus were also present until at least the mid seventeenth century. Exceptionally high values of Plantago lanceolata (mostly in excess of 20% total terrestrial pollen) suggest intensive pastoral farming over most of the period. Between A.D. 200–580, a lull in activity is recorded during which woody species and, in particular, hazel scrub regenerated. The separation of pollen of cereal origin from large cereal-type pollen produced by non-cultivated grasses proved particularly problematic. Reliance has therefore been placed on the weed pollen flora as a guide to arable activity. This flora indicates that arable farming was of some importance in the Burren from A.D. 1000 onwards. The implications of the various findings for the longer term history of the rarer elements of the Burren flora and the relationship between the pollen record and the archaeological and historical evidence for settlement and land use are discussed.