贵州白鹇湖沉积物中孢粉记录的5.5kaB.P.以来的气候变化

通过对白鹇湖沉积物柱芯孢粉组合的剖面变化分析,在有机质14C定年基础上,探讨了白鹇湖地区过去5.5 ka calB.P.以来的植被演替和气候变化过程.研究结果表明,5500-4500 aB.P.期间,各类植被比较丰富,气候温暖湿润;4500-2750 aB.P.期间,干旱草本和蕨类植物开始出现,是气候转变过渡期;2750-1500 aB.P.期间,木本植物组合类型发生明显变化,喜湿草本减少,耐旱草本增加,气候向温凉干旱化发展;1500 aB.P.至今,木本植被和喜湿草本继续减少,中生耐旱草本和蕨类植物数量继续大幅增加,干旱化趋势明显,植被组合向典型石漠化植被组合类型发展.白鹇湖沉积物剖面孢粉组合变化表明,该地区近5000a来气候变化以温度下降、降水减少为主要趋势,并存在明显的陆地植被退化现象.研究还揭示了自然气候变化事件(如气候持续干旱)可导致喀斯特地区发生石漠化,证实了喀斯特地区生态环境具先天脆弱性.科学评估白鹇湖地区气候干旱化趋势及其生态环境影响对指导该地区科学应对气候变化具重要意义,亟待加强.     

Late Holocene land-use and vegetation dynamics in an upland karst region based on pollen and coprophilous fungal spore analyses: an example from the Burren, western Ireland

The late Holocene environmental history of two karstic uplands in the Burren, western Ireland is reconstructed. The palaeoecological investigations focus on species-rich, upland plant communities of high biogeographic interest that include Sesleria-dominated grasslands and heath communities with Dryas octopetala, Arctostaphylos uva-ursi and Empetrum nigrum. Short monoliths taken from shallow peats were pollen analytically investigated. Particular attention was paid to non-pollen palynomorphs, and especially coprophilous fungal spores as indicators of environmental change and pastoral activity at local level. The exposed north-west Burren uplands carried Pinus sylvestris-dominated woodland during the mid and late Bronze Age. The demise of pine on these uplands at ca. 600 B.C. is ascribed to human impact. Evidence is presented for increased pastoral activity in the uplands from early medieval times (ca. sixth century A.D.) onwards. Farming, involving intensive grazing of the uplands, attained greatest intensity during the late 18th and early 19th century, and resulted in more or less total clearance of Corylus scrub which, prior to that, was common in both the upland and lowland Burren. The potential of non-pollen palynomorphs and especially the coprophilous fungal spore record for elucidating traditional Burren farming practices, including winterage (a type of transhumance), is highlighted.     

Characterization of pollen profile of Apis mellifera L. in arid region of Pakistan

Honeybees rely exclusively on pollen and nectar-producing plants for strengthening their colonies and manufacturing honey. Little is known about the indigenous melliferous flora of arid zones of Khyber Pakhtunkhwa (KPK) which is crucial for honey production and how different pollen assessment techniques effect the identification of indigenous melliferous pollen flora. Visual survey and loads ensnaring through pollen traps were used to identify the botanical profile of melliferous pollen flora of Dera Ismail Khan (DIKhan), Khyber Pakhtunkhwa. The test time extended for two consecutive years 2018 and 2019. The study revealed 56 plant species as pollen flora with 18 significant pollen producing species in visual survey technique while 8 species as predominant flora in pollen trapping technique. The major pollen species found common in both the techniques were Brassica napus L., Brassica campestris L., Trifolium alaxandrinum L., Zea mays L., Acacia modesta L., Citrus aurantium L., Euclyptus spp., and Morus alba L. Pollen interception and palynological analysis of pollen were found to be more reliable techniques as compared to focal observations. More than fifty % differences were found by comparing the results of the visual survey and pollen trapping technique in major flora of DIKhan. Based on the availability, utility status and flowering duration of apiphilic flora, mid-February to mid-May was found to be a significant pollen flow period in the study area. Maximum benefit can be taken in this period through trapping ample amount of pollen and stored for using in artificial diets, selling and feeding bees during dearth period.     

Biostratigraphy and <Superscript>14</Superscript>C dating of a lake sediment sequence on the north-west Estonian carbonaceous plateau,interpreted in terms of human impact in the surroundings

The sediment stratigraphy of a medium-sized mixotrophic lake (Ruila) situated below the highest shoreline of the Baltic Ice Lake in the West-Estonian Lowland is described. The lake is without natural inlets our outlets. The reconstruction of vegetation and land-use history based on pollen data, combined with available archaeological data and detailed ¹⁴C dating allows us to give a provisional reconstruction of the temporal and spatial pattern of natural and human induced environmental changes in north-west Estonia during the Holocene. Both radiocarbon dates derived from terrestrial macrofossil dating by accelerator mass spectrometry (AMS) and conventional dating of bulk lake sediment are discussed. The isolation of the lake basin from the Yoldia Sea took place ca. 9700 cal B. C. The Ancylus Lake transgression at ca. 8400 cal B. C. did not reach the basin, but caused a ground water rise, seen in the sediment stratigraphy of the lake. The first signs of human impact on the pollen record appear ca. 5400 cal B. C. (Late Mesolithic). The history of arable farming has been divided into three periods: 1) introduction of crop cultivation and animal husbandry (1500 cal B. C. – A. D. 500); 2) establishment of animal husbandry A. D. 500–1000) and 3) establishment of crop cultivation and intensive cattle breeding (A. D. 1000–today). Due to unfavourable eda-phic conditions the introduction of arable farming was delayed for more than 1000 years compared with elsewhere on the north coast of Esotnia, and intensity of land-use never reached the same proportion as in these areas. Received August 15, 2001 / Accepted August 5, 2002 Correspondence to: Leili Saarse     

From forest to open pastures and fields: cultural landscape development in western Norway inferred from two pollen records representing different spatial scales of vegetation

The cultural landscape development of a farming community in western Norway was investigated through pollen analyses from a lake and a peat/soil profile. The pollen record from the lake indicates that there was a decrease in arboreal pollen (AP) by the end of the Mesolithic period (ca. 4200 cal b.c.), and that a substantial forest clearance occurred during the Bronze Age (ca. 1500 cal b.c.). The latter, together with grazing indicators and cereals, suggests a widespread establishment of farming. At the beginning of the Roman Iron Age there is an increase in heath communities. The pollen diagram from the peat/soil profile shows the forest clearance in the Bronze Age more clearly than the lake profile. This local pollen diagram is compared with modern pollen samples from mown and grazed localities in western Norway. Both analogue matching and ordination (PCA) indicate that the site was characterised by pastures and cereal fields from the Late Bronze Age to the Late Iron Age. An expansion of cereal cultivation took place during the Pre-Roman Iron Age, and an arable field was established at the site after ca. a.d. 800. This investigation illustrates the potential of selecting pollen sites reflecting different spatial scales, and complements the cultural history of the area as inferred from archaeological and historical records.     

The 'oriental' component of the Balkan flora: evidence of presence on the Thracian Plain during the Weichselian late-glacial

Aim To obtain palaeobotanical evidence enabling evaluation of the viability of the hypothesis that the ‘oriental’ element of the Balkan flora reached south‐east Europe from Turkey prior to the Holocene, probably via the Thracian Plain during a late Quaternary glacial stage but no later than the late Weichselian. Location Ezero wetland, northern Thracian Plain, Bulgaria. Methods We undertook analyses of pollen and microspores, plant macrofossils, wood fragments and molluscs recovered from sediments deposited in the Ezero wetland during the late Weichselian and Weichselian late‐glacial. Sediment chronology was determined using radiocarbon age estimates. Results Six metres of sediments were recovered from the basin, of which the lower 3 m, extending from c. 15,450 cal yr bp to the early Allerød, was analysed. A major hiatus occurred after c. 13,900 cal yr bp , the overlying sediments being of late Holocene age. Palaeobotanical evidence indicates predominantly open vegetation during the Weichselian late‐glacial, although macrofossil remains of woody taxa demonstrate the local presence of patches of wooded steppe and gallery forest. Changes in the composition of the steppe vegetation, and in the nature of the sediments deposited in the basin, indicate changes in climatic conditions, especially in the hydrological regime and in the moisture available to vegetation. After an initially relatively moister phase, the final centuries of the late Weichselian were drier, as was a short interval that may correlate with the Older Dryas. Moister conditions characterize intervals corresponding to the Bølling and Allerød sub‐units of the Weichselian late‐glacial interstadial. Although the pollen evidence is thus consistent with that from previous studies of this period in south‐east Europe and south‐west Asia, indicating predominantly open steppe vegetation, the macrofossil evidence indicates the persistent local presence of woody taxa. The woody taxa recorded include Celtis tournefortii‐type and Juniperus cf. J. excelsa, two taxa today characteristic of the wooded steppes of Anatolia and members of the ‘oriental’ element of the southern Balkan flora, as well as Rosaceae Subfams. Maloideae and Prunoideae, Alnus and Fraxinus. Main conclusions The late Weichselian vegetation of the northern Thracian Plain included patches of wooded steppe that supported members of the ‘oriental’ element of the modern Balkan flora. The presence of such taxa renders viable the hypothesis that they could have reached south‐east Europe from Turkey via the Thracian Plain during glacial times. Such hypotheses in historical biogeography can be evaluated critically using the evidence obtained from plant macrofossil analyses in combination with that from pollen analysis.     

Vegetation, landscape and human activity in Midland Ireland: mire and lake records from the Lough Kinale-Derragh Lough area, Central Ireland

A high-resolution pollen record for the Holocene has been obtained from Derragh Bog, a small raised mire located on a peninsula in Lough Kinale-Derragh Lough, in Central Ireland as part of the Discovery Programme (Ireland) Lake Settlements Project. The data are compared with two lower resolution diagrams, one obtained from Derragh Lough and one from adjacent to a crannog in Lough Kinale. The general trends of vegetation change are similar and indicate that landscape-scale clearance did not occur until the Medieval period (ca. a.d. 800–900). There are, however, significant differences between the diagrams due primarily to core location and taphonomy, including pollen source area. Only the pollen profile from Derragh Bog reveals an unusually well represented multi-phase primary decline in Ulmus ca. 3500–3100 b.c. (4800–4750¹⁴C b.p.) which is associated with the first arable farming in the area. The pollen diagram indicates a rapid, and almost complete, clearance of a stand of Ulmus with some Quercus on the Derragh peninsula, arable cultivation in the clearing and then abandonment by mobile/shifting late Neolithic farmers. Subsequently there are a number of clearance phases which allow the colonisation of the area by Fraxinus and are probably associated with pastoral activity. The pollen sequence from adjacent to a crannog in Lough Kinale shows clear evidence of the construction and use of the crannog for the storage of crops (Hordeum and Avena) whereas the Derragh Bog diagram and the diagram from Derragh Lough reflect the growth of the mire. This study reveals that in this landscape the record from a small mire shows changes in prehistoric vegetation caused by human agriculture that are not detectable in the lake sequences. Although in part this is due to the higher temporal resolution and more consistent and complete chronology for the mire, the most important factor is the closer proximity of the raised mire sequence to the dry land. However, the pollen sequence from adjacent to a crannog does provide detailed evidence of the construction and function of the site. It is concluded that in order to ascertain a complete picture of vegetation changes in a lowland shallow lake-dominated landscape, cores from both the lake and surrounding small mires should be analysed.     

Land-use history of the Axlarp area in the Småland uplands,southern Sweden: palaeoecological and archaeological investigations

The results of pollen analysis, magnetic measurements (SIRM), and archaeological and historical investigations, in the Axlarp area are presented. With respect to natural conditions and the distribution of prehistoric features, this area is typical of the higher parts of the Småland uplands, which, agriculturally, is a marginal region of southern Sweden. The study shows that farming in the Axlarp area began at ca. 700 B.C. (dates in calibrated/calendar years). The period 700 B.C.-A.D. 500 was characterized by shifting cultivation of Hordeum and Triticum and much pasture. Between A.D. 500 and A.D. 1200 farming declined but some pasturage was still practised, possibly on a seasonal basis. Two farms were established in the Middle Ages, probably between A.D. 1200–1300. Cereals were sown in stone-cleared fields and pastoral farming and hay making was carried out. One farm was deserted during the 15th or early 16th century and the other developed into the hamlet Axlarp whose farmers practised a three-course cropping system. Land-use history as recorded in the pollen diagram can be related to activities associated with these farms. Cereals grown after A.D. 1200 included Hordeum and Avena, and possibly Triticum and Secale. There are no indications of slash-and-burn cultivation in the area.     

Prehistoric agriculture revealed by pollen analysis,plough-marks and sediment studies at Sola,south-western Norway

In 1985 archaeological excavations at Stavanger Airport, Sola, south-western Norway, revealed evidence for five phases of human activity ranging in age from the Mesolithic to the Late Bronze Age. The two youngest phases, namely 4 and 5 which reflect agrarian activity, are considered in detail in this paper. The fourth phase, which dates to ca. 3500 B.P., contains the first evidence of animal husbandry at the site and, in the fifth phase, there is evidence for a mixed farming economy. Physical evidence of cultivation includes intersecting patterns of plough-marks and, at seven sites, pollen assemblages indicative of arable farming have been recorded. The arable fields, in which weed-rich crops of Hordeum and Triticum were grown, date to ca. 2550-2200 B.P. The fields were subsequently covered by a thick layer of aeolian sand.     

Abandonment of farmland and vegetation succession following the Eurasian plague pandemic of ad 1347–52

Aim This paper reviews the available documentary, archaeological and palaeoecological evidence for the abandonment of agricultural land and consequent regeneration of the forest in Europe after the Black Death. Location Western and northern Europe. Methods This review is the result of an exhaustive search of the historical, archaeological and palaeoecological literature for evidence indicating agricultural decline and forest regeneration in Eurasia during the 14th century. The available evidence for landscape change can be divided into two categories: (1) documentary and archaeological sources, and (2) palaeoecological reconstructions of past vegetation. In the past few years, several pollen diagrams from north‐west Europe have been reported with precise chronologies (decadal and even annual scale) showing the abandonment of farmland and consequent ecological change in the late medieval period. Results and main conclusions There is strong evidence of agricultural continuity at several sites in Western Europe at the time of the Black Death. The effects of the Black Death on the European rural landscape varied geographically, with major factors probably including the impact of the plague on the local population, and soil quality. At two sites in western and northern Ireland, the late medieval decline in cereal agriculture was probably a direct result of population reduction following the Black Death. In contrast, the decline in cereal production began at sites in Britain and France before the Black Death pandemic of ad 1347–52, and was probably due to the crisis in the agricultural economy, exacerbated by political instability and climate deterioration. Much of the abandoned arable land was probably exploited for grazing during the period between the decline in cereal farming and the Black Death. In the aftermath of the Black Death, grazing pressure was greatly reduced owing to reductions in the grazing animal population and a shortage of farmers. Vegetation succession on the abandoned grazing land resulted in increased cover of woody tree species, particularly Betula and Corylus, by the late 14th century. The cover of woodland was greatest at c.ad 1400, before forest clearance and agriculture increased in intensity.     

Survey of the bryophytes of arable land in Britain and Ireland 1: a classification of arable field assemblages

Abstract

Knowledge of the distribution of arable bryophytes lags behind that of bryophytes of many other habitats, and we have almost no information on their occurrence in relation to crop type and agricultural management regime. A survey of arable fields in Britain and Ireland carried out by members of the British Bryological Society in 2001–05 was designed to provide such baseline data. We surveyed a stratified random sample of 200 fields in the main areas of arable agriculture and a further 620 fields in these areas and in areas where arable fields are less frequent. The species present in each field were listed and their frequency within the field assessed. Data on the crop, the cover of vascular plants, bryophytes, trash and bare soil, and the pH and texture of the soil were recorded for each field. Six species assemblages are described on the basis of a classification of the species recorded in each field and their frequency values. The Tortula truncata–Anthoceros and Dicranella staphylina–Riccia glauca assemblages are the most species-rich and are concentrated on acidic soils in northern and western Britain and in Ireland. By contrast, the Barbula unguiculata–Bryum klinggraeffii and Phascum cuspidatum–Microbryum davallianum assemblages are mainly found on calcareous soils in southern and eastern England. The Bryum dichotomum–Marchantia polymorpha assemblage is characterised by widespread, weedy generalist species and is concentrated in East Anglia. The final assemblage, Brachythecium rutabulum–Fissidens taxifolius, characteristically occurs in late-successional fields and was scattered throughout the area sampled. A comparison of the results from Kent with those of a survey of Kentish fields (using a different methodology) by A.G. Side in 1973–74 suggests that the Bryum dichotomum–Marchantia polymorpha assemblage may possibly have replaced the Dicranella staphylina–Riccia glauca assemblage on acidic soils in the last 30 years. The considerable geographical variation within the arable flora of Britain and Ireland revealed by the survey should be taken into account when assessing the meagre evidence for historic changes in the arable bryophyte flora.     

History of sedentary farming in Ångermanland, northern Sweden, during the Iron Age and Medieval period based on pollen analytical investigations

Compared with most parts of Europe, northern Sweden is essentially a sparsely populated wilderness. There is, however, an ever increasing body of archaeological and palaeoecological information that shows that the region has a long cultural history. In this paper, results of pollen analytical investigations from four lakes with varved lake sediments, in the province of Ångermanland, are presented. These investigations have yielded evidence of continuous and sedentary agriculture from the 6th century in the region close to the Bothnian coast and near the mouth of the large river Ångermanälven. This early agriculture appears to have been based on animal husbandry and cereal, mainly barley, cultivation. During a second farming expansion phase at ca. A.D. 1200, rye cultivation became more important. The increased farming activity during this period was most pronounced at the coast and in the river valley, but more peripheral regions away from the river valley were also exploited. During the period A.D. 1600–1800, arable farming assumed greater importance. In the first decades of the 20th century, the area under cultivation declined, cereal cultivation mostly ceased and the fields were used for pasture.     

Logné, a peat bog of European ecological interest in the Massif Armorican, Western France: Bog development, vegetation and land-use history

Logné, one of three raised bogs (Hochmoor) in the Massif Armorican, was officially designated as a nature reserve in 1987 and is of considerable ecological interest from botanical, ornithological and herpetological aspects. Palynological investigations reveal the history of local and regional vegetation during the last ca. 4000 years. From the end of the Neolithic Age to the present day, changes in the bog appear to have been considerably influenced by variations in local watertable level that may be of natural origin or caused by human activity. Alder carr withOsmunda regalis, which was the dominant vegetation around the periphery of the bog at ca. 4200 B.P., underwent many changes. Its final demise occurred in Gallo-Roman times when the local landscape took on a distinctly open appearance. The first clear evidence for cereal cultivation relates to the Bronze Age. After a decline in farming at the beginning of the Iron Age, there was a strong renewal of farming in the La Tène period, which included a distinct arable component and also records forJuglans andCastanea pollen. The timing of the introduction of walnut and chestnut to the Massif Armorican is discussed.     

Pollen and phytolith evidence for rice cultivation during the Neolithic at Longqiuzhuang, eastern Jianghuai, China

Phytolith and pollen analyses were carried out at the archaeological site at Longqiuzhuang in Gaoyou, Jiangsu, southern China. The results indicate that the key morphological phytolith types associated with cultivated rice (Oryza) are common in the Neolithic cultural layers at this site. The evidence strongly suggests that cultivated rice (mainlyO. japonica) was grown locally during the Neolithic. The archaeopalynological record provides information about the impact of human activity and, in particular, farming on the natural vegetation. The evergreen and deciduous broad-leaved forest was substantially altered, and herbaceous taxa, including ruderals, expanded. Based on the results from the phytolith and pollen analyses, two distinct phases of human activity have been recognized, namely (1) phase A (7000-6300 B.P., i.e. early Neolithic) a warm and humid period when arable farming, including rice cultivation, was pursued but the variation in the size of the carbonized rice grains was low, and (2) phase B (6300-5500 B.P., late Neolithic age), a period of relatively cold and/or arid climate when cultivated rice was of major importance and was morphologically similar to present-day rice. Environment, and in particular climate change in the late Neolithic, were important factors affecting the development of rice as a cultivated crop. It was mainly during this period that artificial selection favoured the emergence of forms similar to those of today.     

New evidence of possible crop introduction to north-eastern Europe during the Stone Age

Long term (from the Mesolithic to the Bronze Age) habitation of the Akali settlement on a clearly defined bog-island in East Estonia is used as an example of transitional development from a prosperous foragers’ habitation centre to a hinterland of established farming cultures, taking place through availability, substitution and consolidation phases of crop farming in the boreal forest zone. The pre-Neolithic finds of Triticum and Cannabis t. pollen at c. 5600 b.c. are interpreted as possible indications of the acquaintance of foragers with farming products, through contacts with central European agrarian tribes during the availability phase. The substitution phase is marked by more or less scattered pollen finds of various cereals and hemp and, at Akali, is connected with Neolithic period 4900–1800 b.c. An increasing importance of crop farming in the economy is characteristic of the consolidation phase, but because natural conditions are unfavourable for arable land-use, a regression of human presence is recorded during the second part of the Neolithic. The settlement was abandoned during the Bronze Age at the time when crop farming become the basis of the economy in Estonia. The re-colonisation of the area, traced to ca. a.d. 1200, took place for political reasons rather than through increasing suitability of the landscape.Editorial responsibility: Felix Bittmann     

Ectomycorrhizas associated with a relict population of Dryas octopetala in the Burren, western Ireland II. Composition, structure and temporal variation in the ectomycorrhizal community

The composition, structure and temporal variation of ectomycorrhizal (EM) communities associated with mountain avens (Dryas octopetala) in grass heaths of the Burren, western Ireland were assessed by using soil core sampling in two permanent plots and 30 other sites (196 cores in total). Of the 34 different EM types observed, 11 were common and constituted over 80% of the EM biomass. Four EM types, Craterellus lutescens, Tomentella sp., Dryadirhiza fulgens and Cenococcum geophilum were the most abundant as measured by EM length and frequency of occurrence in cores. The species profile and relative abundances were very similar in cores from the permanent plots and different sites in the Burren, indicating that they were all representative of the same EM community. The below-ground EM community in both plots was compared with production of basidiomes, and the latter was found to be an unreliable indicator of EM community structure. Temporal variation in the EM community was assessed by repeated core sampling of the two permanent plots over a 14-month period (between March 1998 and May 1999). No statistically significant shifts in EM abundance were found between sampling dates, probably as a consequence of the large variation in EM abundance between core samples over the sampling period. No significant relationship was found between rainfall, soil moisture or soil temperature and fluctuations in EM abundance. Patterns of total EM abundance and fluctuations in EM diversity were strongly correlated between the two permanent plots over the sampling period. Temporal fluctuations in the dominant EM type, Craterellus lutescens, were similar in both plots with respect to mycorrhizal length, biomass and relative abundance, and the patterns between both plots were positively correlated. EM diversity was negatively correlated with biomass of ectomycorrhizas of Craterellus lutescens in both plots, but it was significant only in plot 1.     

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.     

Identification of cultivated Pandanus and Colocasia in pollen records and the implications for the study of early agriculture in New Guinea

Pollen records from the island of New Guinea, spanning the last 60 000 years, show a vegetation system sensitive to global climate change and strongly influenced by anthropogenic activity. The evidence for anthropogenic activity in pollen diagrams has focused on indirect indicators such as forest clearance, burning and increases in arable weeds. Tracing individual cultivars has proven to be very difficult as the major cultivated plants, in this case dominated by root crops, have low pollen production, are insect-pollinated or are harvested before flowering occurs. The identification of some cultivars is further restricted by limited information on pollen morphology. The pollen morphology of selected species from two genera (Pandanus and Colocasia), known to include important cultivated species, have been studied. Five pollen taxa are recognised after examination by light microscopy and scanning electron microscopy. It is shown that these can be easily distinguished on the broad criteria of pollen class, grain size and size of echini. The taxonomic and dispersal characteristics of the pollen morphology of these taxa are discussed and the implications of improved identification of cultivated species in late Quaternary pollen records are considered.     

Classification,composition, richness and diversity of British hedgerows

Abstract. A floristic classification of British hedgerows is constructed. Hedges (the woody, structural element) and hedge‐bottoms (the mainly herbaceous ground flora) were analysed separately because different natural and management processes were expected to affect them. The 11 hedge classes varied in size from five to over 500 plots. Over two‐thirds of all hedges were dominated by Crataegus spp. or Primus spinosa. Hedge‐bottoms were more evenly grouped into four classes whose species composition could be related to broad land use/habitat types: intensive arable, rotational/mixed farming, managed grasslands, and woodland. The woodland class was only 12% of the total, and species characteristic of true woodland habitats were uncommon even within that class, so our data do not support the hypothesis of hedgerows acting as‘woodland corridors’for plants. Richness/diversity scores differed markedly between different hedge and hedge‐bottom classes. The richest hedgerows, both in species and inferred habitats, were among the rarer types, while the most common classes (both hedge and hedge‐bottom) were consistently the poorest. Comparison of species composition and diversity in hedges and hedge‐bottoms, and associations between them, all supported the hypothesis that the relative importance of historical, management and ecological effects differed between the two parts of the hedgerow; hedges and hedge‐bottoms should be treated ecologically as largely independent units. The classifications and richness/diversity scores enable easy preliminary assessment of the conservation value of a hedgerow. They also enable individual hedgerows to be placed in a wider (national) context.