Non-arboreal Pollen Research Articles

Pollen record of the past 60 ka BP in the Middle Okinawa Trough: Terrestrial provenance and reconstruction of the paleoenvironment

Core DGKS9602 (931 cm in length) was retrieved from the Middle Okinawa Trough. The age model was correlated with the adjacent core, DGKS9603 (Li et al., 2001), for the upper part and to the standard SPECMAP chronology down to ~ 60 ka BP using marine oxygen isotope control points. Pollen analysis was carried out, and seven pollen zones were identified. The results showed that the pollen spectra in MIS 3 were very different to MIS 2 but comparable with the Holocene. The saccate pollen, principally Pinus, predominated in most parts of the core, except for the interval of the Last Glacial Maximum (LGM) and the late MIS 3 when Artemisia and other herbs increased prominently. The ratios of P/A ( Pinus/ Artemisia) and of PB/NAP (pollen with bladders versus non-arboreal pollen) were used as a proxy for sea-level change and for estimating distances from the coastline to the study site. The provenance study, using a modern analog technique based on the East Asian Modern Pollen Database and fossil pollen assemblages, revealed that the pollen were derived from diverse source areas during different stages since ~ 60 ka BP. The pollen zones equivalent to MIS 1 and 3 were characterized by uncertain and disparate areas of provenance, and the surrounding continents, including Eastern Mainland China, Korea and Southern Japan, possibly made equivalent contributions, which may be the result of enhanced pollen transport by the northwesterly wind. However, the LGM represented in core DGKS9602 was distinguished by restricted sources from the exposed East China shelf, where the vegetation was quite similar with the herb coverage in the present-day North China Plain. The pollen assemblages sensitively reflected the coastline changes, marked by transport patterns between fluvial runoff and northwesterly winds plus ocean currents. Some pollen changes and limits of pollen zones coincided with the timing of Heinrich events, implying that the rapid climate fluctuations during MIS 3 and MIS 2 may have partially resulted in the forest changes in Eastern Asia. The pattern of relative abundance of subtropical and total arboreal taxa is consistent with that of δ 18O from Hulu Cave, implying monsoonal climatic control over vegetation change. The estimated temperature (MAT) by the means of pollen ratios for the LGM was 5–8 °C lower than that in the Changjiang River mouth today.

Resting cysts of freshwater dinoflagellates in southeastern Georgian Bay (Lake Huron) as proxies of cultural eutrophication

Resting cysts attributed to the freshwater dinoflagellate genus Peridinium were found in surface sediments from Severn Sound, southeastern Georgian Bay (Lake Huron, Laurentian Great Lakes of North America). Two distinct cyst morphotypes were present and they were assigned to Peridinium wisconsinense Eddy, 1930 and Peridinium willei Huitfeldt-Kaas, 1900 by establishing cyst–theca relationships through germinations and single-cell LSU rDNA analysis on an excysted cell of Peridinium willei. Sediments recovered from deep, sheltered portions of Severn Sound and restricted basins like Honey Harbour contained between ~ 750 and 8500 cysts/cm 3. However, winnowing by bottom currents and high concentrations of dissolved oxygen adversely impact the dinoflagellate cyst record on the lakebed, and cyst concentrations in easily remobilized muds on bathymetric highs were < 100 cysts/cm 3. Down-core changes in the relative abundances of these two cyst morphotypes were attributed primarily to cultural eutrophication related to land-use changes around Severn Sound over the last six centuries. Cysts of Peridinium willei, a cosmopolitan dinoflagellate species that occurs in a broad range of temperature, pH and nutrient conditions, comprise 60–74% of the cysts identified in Ambrosia (ragweed)-rich sediments in the upper 20 cm of a gravity core taken from Honey Harbour. Euro-Canadian settlement and land-clearing that began in the Midland-Penetanguishene region around A.D. 1840 are evident in the increase in Ambrosia (ragweed), Gramineae (grasses) and other herbs (non-arboreal pollen) that mark the base of the Ambrosia zone (pollen zone 4) as well as an overall increase in terrigenous flux. In addition to siltation, this terrigenous flux increased the availability of limiting nutrients to the previously oligotrophic waters of Severn Sound, leading to increased cyst flux in Honey Harbour peaking at nearly 3000 cysts/cm 2/y in A.D. 1966, an order of magnitude higher than cyst fluxes prior to the Euro-Canadian Ambrosia zone. Peridinium wisconsinense was the more common dinoflagellate cyst species in Honey Harbour prior to Euro-Canadian settlement, when cyst flux was an order of magnitude lower. This is consistent with the restriction of this species to relatively warm, oligotrophic to mesotrophic lakes in North America. An earlier increase in P. willei at the expense of P. wisconsinense in the core from Honey Harbour within pollen zone 3 d (~ 700 to ~ 150 yBP) is attributed to earlier land-clearing by the Wendat (“Huron”), who practiced agriculture in the Penetanguishene peninsula between ~ A.D. 1450–1650. The cysts of these freshwater dinoflagellates thus appear to be sensitive to cultural eutrophication.

Evaluating the palaeoecological potential of pollen recovered from ice in caves: A case study from Scărişoara Ice Cave, Romania

Scărişoara Ice Cave (NW Romania) contains the world's largest underground perennial ice deposit. In this paper we present the results from pollen, micro- and macro-charcoal, and plant macrofossil investigations of a vertical ice exposure spanning the past ca. 1000 years in the Little Reservation from this cave. These results are then compared with three peat sequences close to the study area in order to evaluate the potential of using biotic remains preserved in the ice block for past vegetation, environment and climatic reconstructions. Pollen data from Scărişoara Ice Cave suggest that each impurity-poor layer is likely to include a smaller number of years, compared to organic-rich layers in which repeated, multi-annual melting events may have concentrated a higher amount of organic matter. However, layers with abundant presence of organic matter and also containing plant macro-remains, micro- and macro-charcoal particles appear to indicate a rapid wash-in of surface material into the cave. Evidence from the pollen record suggests the prevalence of close forest dominated by Fagus sylvatica between ca. AD 1200 and 1500 and by Picea abies between ca. AD 1000 and 1500 and from AD 1550 onwards. Contrary to the pollen records from the surface, the pollen assemblages from Scărişoara Ice Cave are characterized by low frequencies and diversity of pollen of herbaceous plants (non-arboreal pollen, NAP) and coprophilous spores. However, there are fluctuating frequencies in these taxa, which appear to track changes in climate conditions (higher during the Medieval Warm Period and lower during the Little Ice Age), which suggest that land-use changes were likely modulated by the climate. High amounts of micro- and macro-charcoal particles between AD 1600 and 1850, when climate conditions were cool and wet, suggests that the charcoal was washed into the cave during times of extreme rainfall events, rather than associated with increased burning regime. A comparison with pollen records from the surface shows analogous forest development and fluctuations in the NAP, therefore supporting the hypothesis that the cave ice can be a valuable paleoecological archive.

Modern pollen rain in heathlands and adjacent forest phytocoenoses in Northern and Central Poland

Differences between modern pollen rains in three types of phytocoenoses were studied in two regions, i.e. Tuchola Forest and Toruń Basin. The phytocoenoses in question were heaths, young pine-birch growths and mature pine tree stands, which form a temporal sequence and spatial mosaic in the landscape. In order to compare the structure of pollen samples, phytocoenoses and the landscape, the methods of numerical taxonomy were applied. An increase in the average number of sporomorphs was recorded, as well as in the taxonomic diversity of the pollen spectrum in this temporal sequence arranged from non-forest communities through young growths to mature forests. In the subsequent developmental stages, also the percentage contribution of Pinus pollen increased, as well as the total contribution of arboreal pollen (AP). The increase in the percentage contribution of arboreal pollen is accompanied by the decrease in the contribution of non-arboreal pollen (NAP), including Calluna and Ericaceae. Also a small increase in the number of species was observed. With the increased pine domination, however, the diversity of pollen types (expressed by rarefaction and Shannon-Wiener indices) decreases. As a result of the performed analyses, it was also found that the species composition of phytocoenoses and a pollen spectrum differs considerably, because the import of pollen from further areas exerts a significant influence on the structure of a palynological sample. The genus Calluna is the only type of plants characterized by a strong relationship between the occurrence in a phytocoenosis and in a surface pollen sample. Similarity between the taxa composition of a pollen spectrum and the landscape structure, consisting of a mosaic of phytocoenoses, seems to be higher than between a pollen sample and a phytocoenosis from which that sample was collected. The latter thesis, however, needs to be confirmed by further researches.

Airborne pollen calendar of Salamanca, Spain, 2000–2007

Background The determination of pollen types and their proportions in the atmosphere of relevant urban areas have increasingly been evaluated in different regions. The final goal has been to elaborate a pollen calendar, providing data about the occurrence of pollen grains in the air, thus permitting medical treatment and prophylaxis. Methods An aerobiological study was carried out in the atmosphere of the city of Salamanca, Spain, during eight years (2000–2007) by means of a Hirst type volumetric spore trap. A pollen calendar was elaborated following exponential classes obtained from 10-day average concentrations of the main pollen types. Results Mean annual pollen index was 16,916, coming from 72 different types of pollen. During the studied period, an increase of annual pollen levels was registered by means of regression analysis index. The most important types of pollen were Quercus, Poaceae, Cupressaceae, Olea, and Plantago. Arboreal pollen grains (62.7%) were more represented in airborne pollen spectrum than non-arboreal pollen (37.3%). Airborne pollen levels were particularly high between April and July, showing the highest values in May and June. Conclusions In aerobiological terms Poaceae pollen seems to be a major risk for potential sensitised individuals due to its known allergenicity and its high atmospheric concentrations between late spring and early summer, followed by Cupressaceae, Olea and Platanus pollen grains, and taking into account the possible role of Fraxinus and Quercus in earl spring allergenic courses and in processes of cross-sensitivity, respectively.

Environmental reconstruction of a later prehistoric palaeochannel record from Burrs Countryside Park, Bury, Greater Manchester

The results from an analysis of pollen, insect and plant macrofossil remains from the shallow wood peat fill of a palaeochannel associated with hummocky (deglacial) sediments infilling the valley of the River Irwell at Walmersley known locally as Burrs Countryside Park, Bury, Greater Manchester (NGR SD 796 127) are presented. Radiocarbon dates from the deposit provide an age range from 1310 to 1040 cal. BC to 920 to 800 cal. BC. The environmental record indicates that during the Middle and Late Bronze Age the valley floor was covered by carr woodland consisting mainly of alder and hazel, including areas of open water. Insect and pollen remains indicate that mixed deciduous woodland (birch, elm, beech and ash) was present on the surrounding slopes. Although non-arboreal pollen remains low and may merely indicate woodland edge grassland communities, increases in the percentage of oak and birch pollen over time may reflect small-scale clearance of the alder carr in the valley bottom. Alternatively, if the pollen diagram is merely recording a decline in alder pollen at the top of the profile, this could also explain the increase in the relative proportion of other arboreal taxa. There are no taxa present directly indicative of human activities associated with the nearby Castle Steads hillfort. The palaoenvironmental results from this site appear to match those for the Greater Manchester area and wider north-west region in general, suggesting that there was a mosaic of environments present in the Bronze Age, with some areas cleared of woodland earlier than others.

Climate-driven environmental change in the Zhada basin, southwestern Tibetan Plateau

The Zhada basin is a large Neogene extensional sag basin in the Tethyan Himalaya of southwestern Tibet. In this paper we examine environmental changes in the Zhada basin using sequence stratigraphy, isotope stratigraphy, and lithostratigraphy. Sequence stratigraphy reveals a long-term tectonic signal in the formation and filling of the Zhada basin, as well as higher-frequency cycles, which we attribute to Milankovitch forcing. The record of Milankovitch cycles in the Zhada basin implies that global climate drove lake and wetland expansion and contraction in the southern Tibetan Plateau from the Late Miocene to the Pleistocene. Sequence stratigraphy shows that the Zhada basin evolved from an overfilled to underfilled basin, but continued evolution was truncated by an abrupt return to fluvial conditions. Isotope stratigraphy shows distinct drying cycles, particularly during times when the basin was underfilled. A long-term environmental change observed in the Zhada basin involves a decrease in abundance of arboreal pollen in favor of nonarboreal pollen. The similarity between the long-term environmental changes in the Zhada basin and those observed elsewhere on and around the Tibetan Plateau suggests that those changes are due to global or regional climate change rather than solely the result of uplift of the Tibetan Plateau.

An evaluation of the airborne pollen–precipitation relationship with the superposed epoch method

A statistical analysis was performed on a sample of 4 days sequences in which rainfall occurred during the second day, in order to establish airborne pollen–precipitation relationships. Drizzle (precipitation ≤ 1 mm) and rain (precipitation > 1 mm) events were considered as well as arboreal or non-arboreal pollen. Results showed that arboreal pollen decreases synchronically with the occurrence of a drizzle, registering the minimum value the following day of the precipitation occurrence. The high frequencies of fog and wet soil associated with the following day of drizzle occurrence support the hypothesis that besides the wash out, airborne pollen concentration could decrease by nucleation and impaction processes. As well, diurnal variation suggests that high humidity conditions could also affect pollen emission as already demonstrated by other authors.

Airborne pollen patterns in Mar del Plata atmosphere (Argentina) and its relationship with meteorological conditions

This work is part of a series of aerobiological researches conducted in the city of Mar del Plata, Argentina. The annual, seasonal and daily features of the pollen cloud were analyzed over 2 years, together with the effects of the meteorological variables. Cupressaceae amounted to 75 and 54% of the annual total in each year, and it was analyzed separately due to its proven overrepresentation. Eighty-five pollen types were registered during the 2 years, bearing a similar annual pattern (more than 50% from August to November, December also being an important month). Arboreal pollen predominated between late winter and spring (61 and 49% of the annual total), while non-arboreal pollen did so from late spring to summer. The observed seasonality was significantly correlated with the monthly mean temperatures and associated with its effect on phenology. No significant differences along the day were detected between years and 50% of the daily total was recorded between 1000 and 1600 hours. The maximum concentration was registered at 1000 hours in spring and summer, but later in autumn and winter. Regarding the hourly scale, the significant correlation of total pollen with temperature and wind speed was positive, albeit negative with relative humidity. These effects are linked to airborne pollen release and transport. The role rainfall plays on airborne pollen is discussed. To interpret the results, it is important to consider the time scale at which the aerobiological phenomenon is analyzed.

Seasonal sedimentation in the Pliocene Villarroya Lake (N Spain) inferred from pollen analysis

High-resolution pollen analysis was performed on a short (8.7 cm thick) section with 94 varve couplets (made up of dark and light laminae) from a lacustrine facies of the Pliocene Villarroya Basin, Spain. The aim of the present study was (i) to verify the seasonality of the sedimentation and (ii) to determine if pollen data record the short-term climatic fluctuations related to variations in laminae thickness and colour. The samples displayed high pollen concentrations and very good taxonomic diversity. The composition of the pollen spectra indicated that the vegetation structure was closely linked to relief: (i) a regional open herbaceous vegetation, (ii) a local marshy and riparian environment, (iii) deciduous mixed forest at mid-altitudes, and (iv) coniferous mixed forest in the surrounding mountains at higher altitudes. In the 48 distinct couplets where the dark and light laminae have been separately sampled, the pollen content showed higher concentrations of early flowering trees in the dark ones, whereas late-flowering plants were more abundant in the light ones. Total pollen concentrations in the 48 couplets were higher in most of their dark layers. These results point to a seasonal layering. According to present-day flowering times, the dark laminae represent sedimentation in winter/spring and the light laminae sedimentation in late summer/autumn. The correlation between the AP (Arboreal Pollen)–NAP (Non-Arboreal Pollen) percentages and lamina thickness linked lamina thickness with the highest values of AP, indicating warmer periods. Variations in the ecological groups enabled us to differentiate eight pollen cycles related to short-term climatic fluctuations. These alternations seem to be more associated with seasonality in precipitation than with temperature oscillations and could be correlated with the NAO/ENSO-like and sunspot-like cycles.

Associations among modern pollen, vegetation, and climate in western North America

A compilation of 1884 modern pollen surface samples was analyzed to explore the relationships between spatial distributions of pollen percentage data vs. climate and vegetation in western North America. Modern pollen spectra capture many of the unique traits of regional vegetation patterns and reflect regional patterns of climate diversity. Large-scale vegetation differences were identifiable by their pollen signatures. At the coarsest scale, forested regions were dominated by arboreal pollen and Pinus pollen abundances were typically >30%. In contrast, non-forested regions were dominated by shrub and herbaceous pollen types with Pinus percentages typically <30%. At finer scales, indicator taxa were useful for identifying vegetation types. For example, Picea was a good first-order indicator of boreal spruce forest vegetation with relatively high median percentages (22%), whereas Quercus was a good first-order indicator of desert vegetation with low median percentages (1%). Pollen abundance also provided climatic information. High Betula percentages occurred over a relatively narrow climatic range corresponding with their high latitudinal distribution, high Artemisia percentages were registered in winter-cold and dry climates of the interior basins. Arboreal pollen types were abundant in cool and wet climates, while non-arboreal pollen types dominate in climates that are warm and dry. Using pollen assemblages to predict local climate conditions shows that climate conditions are well predicted given knowledge of pollen spectra and climate conditions of the nearest analogues. Low accuracy was evident with pollen-based climate predictions in desert regions and temperate rainforests because of either poor sample density (in the case of the former) or extremes in temperature and/or precipitation (in the case of both). In other regions, vegetation and climate space were accurately predicted even when proximal samples, within 100 km, are excluded as the possible analogues. These results show that, within the vegetation and climate space of this region, the modern-analogue technique is useful for quantifying broad-scale vegetation and climate changes.

A palynological study of the Acheulian site of Gesher Benot Ya’aqov, Israel

The results are discussed of the palynological (pollen-analytical) examination of a sediment section in the Hula Valley of northern Israel, with evidence of Acheulian occupation dated to 700,000–800,000 b.p. In general there is a fair agreement between the palynological data and the wood remains identified from the site, but there are also discrepancies, some of which can be explained and others not. Although relatively well represented in the pollen record, Pinus (pine) most probably did not occur in the Hula area. Some pollen types are thought to have been carried in from hundreds of kilometres away (long-distance transport). Together the pollen and wood evidence suggests that Quercus ithaburensis–Pistacia atlantica (Tabor oak–Atlantic terebinth) woodland (open forest) was found in the Hula Valley (other than the lake and marshes) and on the lower reaches of the mountains flanking the valley on both sides. In addition to deciduous Tabor oak, evergreen Kermes oak (Quercus calliprinos) must have been an important component of this woodland. Wild olive (Olea europaea var. oleaster) may also have been quite common here. The suggestion of open forest, with fairly widely spaced trees, is based upon the high non-arboreal pollen frequencies and indicates fairly dry climatic conditions. Various stream-bank trees and shrubs are represented in the pollen and/or wood records, such as Fraxinus (ash), Ulmus (elm), Salix (willow) and Platanus (plane tree). During the period represented by the upper section of the pollen diagram, Cedrus (cedar) must have reached the Hula area, indicating increased humidity. In the steppe-like field layer (undergrowth of the woodland) grasses (Gramineae) must have played a prominent role in addition to a great number of other species. In particular Compositae and Umbelliferae include a large variety of species (many different pollen types). Two Chenopodiaceae maxima, coinciding with Gramineae minima, are thought to be indicative of periods of increased climatic dryness. The local lake and marsh vegetation is fairly well represented in the pollen record, but interpretation in terms of vegetation succession is only possible to some degree. Mention is made here of Trapa natans (water chestnut), the nuts of which were consumed by the Acheulian inhabitants.

Modern pollen rain in savanna and forest ecosystems of Gabon and Cameroon, Central Atlantic Africa

Eighty modern soil surface and litter samples from southern Cameroon and Gabon, Central Atlantic Africa (5°N–4°S, 10°–15°W), were analysed for pollen content. The samples are distributed among two main vegetation types: savanna (8 samples) and forest (71 samples). The aim of this study is to provide new data on the modern pollen rain in the Guineo-Congolian phytogeographical region, mainly in forest communities (secondary and mature forests on well drained soils, and hygrophilous forests) and to interpret these data using diagrams of pollen percentages and numerical analyses. The savannas are well identified by high frequencies of non-arboreal pollen with as pollen marker the Poaceae, and the forests by high frequencies of arboreal pollen with as important families the Burseraceae, Caesalpiniaceae, Mimosaceae, Euphorbiaceae and Sapindaceae. Within the forest ecosystem, secondary and mature forests on well drained soils can be differentiated on the basis of distinct assemblages of tree pollen taxa such as Zanthoxylum, Phyllanthus, Tetrorchidium, Margaritaria discoidea in secondary forest spectra and abundance of Burseraceae, Caesalpiniaceae, Sapindaceae in mature forest ones. In addition, hygrophilous forests are well identified by the presence of high pollen contributors such as Uapaca, Nauclea, Macaranga and Raphia. This work shows that the major vegetation communities occurring today in Cameroon and Gabon can be well differentiated by their pollen assemblages.

Late Holocene paleoenvironmental changes in subtropical Taiwan inferred from pollen and diatoms in lake sediments

We analyzed pollen, spores, diatoms, organic carbon, nitrogen, and δ13C of organic matter in lake sediments to infer climate changes and reconstruct the paleo-environment of subtropical Taiwan over the past ∼1300 years. A 31.5-cm sediment core that represents deposition from 650 AD to present was taken from a mountain lake, Duck Pond, located 760 m a.s.l. We differentiated five zones using cluster analysis on pollen and spore assemblages. Fluctuations in the relative abundances of arboreal taxa, herbaceous plants, and ferns reflect changes in the relative amounts of woody versus grassland vegetation. Such shifts are associated with changes in temperature and humidity and are consistent with climatic periods reported for the temperate region of central China. Climate changes inferred from the pollen assemblages are also correlated well with changes in the ratios of fern spores to pollen, with organic carbon to nitrogen, and with the δ13C values in the sediments. Fluctuations in these data throughout the entire core were in good agreement with the changes in pH inferred from diatom assemblages. This study provides evidence of climate change in northern Taiwan over the past 1.3 millennia, assuming that climate can be inferred from the ratio of arboreal to non-arboreal pollen and from the pH of the aquatic environment.

Late Holocene Pollen Stratigraphy in Four Northeastern United States Lakes

Four pollen diagrams from Maine, New York, and Pennsylvania provide fine resolution (40 or 80 years) records of vegetation change in northeastern United States during the past 2000 years. A long term increase in pollen accumulation rates (PAR) of Picea occurred at the three sites in Maine and New York. Around 1100 years ago, Tsuga and Fagus decreased and Quercus and Castanea increased at Ely Lake in northeastern Pennsylvania. Around 500 years ago, Tsuga and Fagus greatly decreased in Maine and northern New York, while in northeastern Pennsylvania there was an increase in Tsuga and Fagus and a decrease in Quercus and Castanea pollen. Non-arboreal PAR were negligible prior to the European settlement of the area, after which there was an abrupt increase in non-arboreal pollen types.

Detecting open vegetation in a forested landscape: pollen and remote sensing data from New England, USA

The proportional cover of forest and grassland vegetation, known as landscape openness, has been particularly difficult to reconstruct because of differences in pollen productivity and transport between the two vegetation types. To begin to calibrate landscape openness in eastern North America, we collected 21 samples of surface sediments from small ponds (less than 60 ha) in the Upper Connecticut River Valley of New England, USA. Pollen assemblages from these surface samples were compared with vegetation composition around each pond assessed with three different remote sensing methods: land cover digitized from aerial photographs, the National Land Cover Database and a spectral mixture analysis of vegetation structure using LANDSAT data. A principal component analysis indicates that most of the variation in land cover among sites is captured by pollen data and each of the three vegetation methods. Because spectral mixture analysis contains at least as much vegetation information as the other two techniques, while avoiding the problem of classifying vegetation into categories, it is better for comparison with pollen data and detection of landscape openness. Even though there is a relationship between non-arboreal pollen percentages and a metric of landscape openness, it is inadvisable to use pollen percentages alone to infer landscape openness across regions either in modern or ancient times. Quantitative assessments and reconstructions of plant abundance at a higher taxonomic resolution will require detailed vegetation surveys to correlate with pollen data from surface samples and possibly simulations of modern and ancient landscapes. Open areas in a landscape that is over 75% forested can be detected, allowing for future quantitative reconstructions of landscape openness.

Late Glacial Sedimentation and History of the Lake Nipigon Basin, Ontario

The Lake Nipigon basin lies north of the Lake Superior basin and was the hydrological link between glacial Lake Agassiz and the Great Lakes during part of the last deglaciation. A sequence of glaciolacustrine sediments, composed mainly of silt-clay rhythmites and sand, was deposited in the offshore waters of glacial Lake Nipigon by overflow from Lake Agassiz and meltwater from the retreating glacier margin. Sections from six long sediment cores and four lake bluff exposures reveal a sandy (early deglacial) lower section that is overlain by 300 to 850 silt-clay rhythmites (varves). Deposition of these varves, as well as coarser sediment along the western shore, began after 9200 BP, as the glacial margin retreated northward along the continental divide that separated the Nipigon basin from the higher Lake Agassiz basin to the west. The absence of ice rafted clasts in the rhythmites suggests that the ice had retreated from the lake by the time they were deposited. On the basis of their elevation in relation to the lowest raised beach at West Bay, which formed about 9000 BP, most rhythmites probably were deposited between 9000 and 8000 BP. Species of arboreal pollen are present in early postglacial sediments of the Nipigon-Superior lowlands, suggesting that the Lake Nipigon region became colonized by coniferous and deciduous forests soon after déglaciation. The presence of non-arboreal pollen species suggest that these forests were interspersed with open meadows and grasslands, similar to today's floral assemblages. Fossil molluscs recovered from glaciolacustrine sand exposed along the eastern side of the basin suggest that the limnological characteristics of late glacial Lake Nipigon were similar to those of today.

16 000 years of vegetation and settlement history from Egelsee (Menzingen, central Switzerland)

Past vegetation dynamics and human impact from the Lateglacial to the present are reconstructed by pollen analysis of a core 12 m long from the raised bog Egelsee, central Switzerland (770 m a.s.l.). The depth—age model of the core is based on 29 AMS 14C dates. The oldest dated macrofossil has an age of 13 080 ± 105 radiocarbon yr BP (15 370 cal. yr BP); extrapolation leads to a basal age of the core of 16 200 cal. yr BP. The biostratigraphy shows a typical vegetation development for Central Europe from open pioneer vegetation to Betula- Pinus forests in the Lateglacial, thermophilous mixed deciduous forests in the early Holocene, then mesophilous Abies-Fagus forests, and finally to the present cultural landscape. The initial population expansion of Abies alba may have coincided with climatic change at c. 8500 cal. yr BP. The mass expansion of Abies alba at 8100 cal. yr BP may have been triggered by the 8.2-ka event and coincided with the empirical limit of Fagus silvatica, indicating initial population expansions. The succession of ecosystems with different plant composition is confirmed by detrended correspondence analysis (DCA): the main changes in the DCA axis 1 and 2 correspond to the transition phases between the different ecosystems. DCA axis 1 has an eigenvalue of λ1 = 0.46 and is significantly correlated ( r = 0.82) to the non-arboreal pollen percentage curve. Rarefaction analysis shows a high pollen diversity in the Lateglacial, lower pollen diversity in the Holocene before human impact, and increasing pollen diversity correlated with increasing human impact. Very little is known about the archaeology of the montane belt in central Switzerland. This study provides new data concerning human impact and settlement history in this area. Human activities are indicated by cereal pollen (earliest Hordeum/Triticum type at 4700 cal. yr BP). Distinct pulses of anthropogenic forest clearances can be observed from the Neolithic period onwards.

A contribution to deciphering the meaning of AP/NAP with respect to vegetation cover

This study reopens the discussion on the AP/NAP ratio that contrasts the total number of Arboreal Pollen grains (AP) to that of the Non-Arboreal Pollen grains (NAP), and its meaning in terms of vegetation land-cover. Based on a set of 52 present-day pollen assemblages (mostly moss polsters) from continental France and black- and-white aerial photographs of these localities, we perform statistical analyses to clarify the meaning of the AP/NAP ratio. Short- and long-distance transported pollen grains, possible over-representation of Pinus, and distortion of cultivated plants are among the biases explored here and for which answers are given. Grey level analysis of the aerial photographs provides direct estimates of the Tree Surface/Herb Surface (TS/HS) ratio for a radius of 1000 m around the sampling point. Statistical estimates of the AP/NAP and TS/HS cut-off values separating tree- and herb-prevalent landscapes are computed. Such results obtained from modern pollen records have been applied to a Late Pliocene small maar locality from southern France characterized by a very weak pollen transport and provide the basis to further distinguish tree- and herb-prevalent landscapes in past pollen records.

한반도 중서부 지역의 후빙기 식생 변천사

A sediment core from the Cheollipo arboretum ( 47' 57'N, 09' 04') was studied for pollen analysis in order to reconstruct postglacial vegetational change and environmental changes around the central western region of the Korean Peninsula. The record shows four pollen assemblage zones: Zone CHL-I, Quercus stage (ca. 9,3006,200 yr BP): zone CHL-II, Quercus-Pinus stage (ca. 6,2004,600 yr BP); zone CHL- III, Pinus-Quercus stage (ca. 4,6001,160 yr BP): zone CHL-IV and Pinus stage (ca. 1,160 yr BP-present). During the 9,3008,500 yr BP, the early Holocene, researchers have guessed a piece of cool-temperate norihern/altimontane mixed coniferous and deciduous broad-leaved forest. Between 8,5004,600 yr BP the Quercus dominated the landscape of study area and the established dates of this typical cool-temperate central/montane deciduous broad-leaved forest vegetation might be ca. 6500 yr BP, and then the Pinus developed around the site at ca. 5,700 yr BP. The abrupt increase of Pinus and NAP (non-arboreal pollen) after ca. 1,100 yr BP indicates the vegetation changes due to human activities. From the dynamics of the Chenopodiaceae pollen indicating salt marsh and freshwater pollen flora such as Typha, Trapa, Nymphoides and so forth, we suggest that the tidal flat was altered into freshwater lake around 6,500 yr BP.