Modern Pollen Spectra Research Articles

Comparison of pollen and conifer stomates as indicators of alpine treeline in northwestern Canadian lake sediments

We compare fossil pollen and stomate assemblages in 29 lake sediment surface samples from mountainous regions in northwestern Canada to characterize the relationship between modern vegetation, and pollen and stomate deposition. Modern pollen spectra were dominated by arboreal taxa originating from lower elevation sites. Pinus pollen frequently reached 30% of the pollen sum, regardless of elevation. Alpine-tundra vegetation has lower pollen abundance, even in the alpine-tundra zone, where it dominates the sparse vegetation cover. Fossil stomates were observed in all but one site where trees currently exist in the vicinity of the lake, while no stomates were found in the sediments from alpine-tundra sites. The highest concentration of stomates occurred in lake sediments from closed-canopy forested areas. Our data suggest that different boreal forest types may be differentiated based on pollen assemblages and that the presence of stomates clearly distinguishes vegetation zones dominated by arboreal vegetation from alpine-tundra zones where trees are not present.Key words: pollen, conifer stomates, treeline, Pacific Northwest.

A comparison between modern pollen spectra of moss cushions and Cundill pollen traps

Pollen spectra of 23 Cundill pollen traps from 23 different sampling sites in Southwest Turkey are compared with the corresponding pollen spectra of moss cushions from the same sites. The Cundill pollen traps represent the modern pollen rain data from one year whereas the moss cushions represent the pollen rain of several years. The comparative study reveals some main differences between the two pollen entrapment media. The one-year entrapment medium (pollen trap) appears to be more sensitive for local (releve area 10x10 m) and regional (100-500 m, or a few kilometres for Olea europaea) vegetation. Pollen spectra of moss cushions are dominated by high pine pollen percentage values and hardly sense fine vegetation structures. The conclusion of this comparative modern pollen study allows to interpret fossil sediment spectra from the Near East in a more critical way. It is concluded that one should preferably sample rapidly deposited sediments for palynological analyses, as the resulting highresolution pollen diagrams will be most informative about the former vegetation patterns.

Modern pollen spectra from tropical South India and Sri Lanka: altitudinal distribution

SummaryWe analysed the pollen content of 106 surface soil samples from evergreen and deciduous tropical forests distributed between 6° and 13° of latitude north in South India and Sri Lanka. The samples were collected along altitudinal gradients, ranging from 50 to 2420 m, in five regions that experience different rainfall regimes. Original pollen data from tropical vegetation subjected to seasonal monsoon rains are presented along altitude/temperature gradients. This paper includes a summarized description of the vegetation types mapped in the area.The pollen results are presented in the form of quantitative pollen diagrams and correspondence analyses. They show clear distinct pollen assemblages and markers for all types of vegetation in deciduous and evergreen vegetation. Forests are well identified by percentages of Arboreal Pollen greater than 50%, despite the fact that Dipterocarpaceae and Lauraceae are hardly recorded by pollen.The pollen distinction between low, medium and high elevation evergreen forests matches that established by ecologists. The botanical limits, respectively, placed at 900 m and 1500 m limits, correspond to the 20 °C and 15 °C‐values of mean temperature of the coldest month. They appear clearly identified in the modern pollen record. This justifies further use of pollen data in Biome modelling.

A method to determine warm and cool steppe biomes from pollen data; application to the Mediterranean and Kazakhstan regions

An objective method for the assignment of pollen spectra to appropriate biomes has been published recently. The aim of this paper is to improve the distinction between warm and cool steppes, thus refining vegetation and climate reconstruction, particularly during the Last Glacial Maximum. A set of modern pollen spectra from the Mediterranean and Kazakhstan regions, dominated today by open vegetation types, has been analysed statistically in order to relate pollen taxa abundances to warm acid cool grass/shrub plant functional types (PFTs). A statistical test using modern pollen data shows that the method is able to distinguish between cool and warm steppe biomes with a high degree of confidence. The method has been applied to two fossil pollen records. The results of this exercise showed that cool steppe dominated in central Greece between 18 000 and 13 000 yr BP, while in western Iran the vegetation was at the boundary between cool and warm steppes. These vegetation types were replaced by warm mixed forest in Greece and warm steppe in Iran after that time span. (C) 1998 John Wiley & Sons, Ltd.

The Holocene vegetational history of the Nigerian Sahel based on multiple pollen profiles

Four Holocene pollen diagrams are presented from interdune depressions in the Manga Grasslands (northeastern Nigeria near 13°N). These sequences are interpreted using modern pollen spectra, statistical analyses and groupings based on phytogeographical affinity (Long Distance, Sahelian, Sudanian, Guinean). The roles of climate change and anthropogenic activity in the vegetational history of the central part of Sahel are evaluated. Particular attention is given to the separation of regional (Manga Grasslands) from local (individual depressions) vegetation trends. Humid conditions in the early and mid-Holocene (from 10,000 to ca. 3300 yr B.P.) enabled the establishment of, and sustained, swamp forest vegetation in the interdune depressions. The main taxa ( Alchornea, Syzygium and Uapaca) have Guinean affinities. The surrounding dunefields consisted of open savanna with Sahelian and Sudanian (e.g., Combretaceae, Detarium) elements present. Drier conditions ca. 3300 yr B.P. produced abrupt changes in pollen stratigraphy and led to the establishment of the modern vegetation of the Manga Grasslands. Although occupied since at least 3700 yr B.P., there is little evidence of human activity in the pollen diagrams. The nomadic pastoralism practiced by the human occupants of the Manga Grasslands may be palynologically undetectable. Although the Holocene vegetational history of the Manga Grasslands appears to have been primarily controlled by climate, caution should be exercised before drawing climatic inferences from these pollen sequences. For the early and mid-Holocene differences of ca. 1000 years exist in the timing of vegetation changes between the individual depressions. While water levels in the depressions are likely to be coupled to climate, the vegetation response appears to be strongly influenced by local conditions (in particular variations in the depth of depressions and so the relative height of water table). In addition, the Guinean swamp forest vegetation of the early and mid-Holocene is unlikely to be representative of vegetation trends at this latitude, but rather developed extrazonally as a result of the particular topographic/hydrological conditions prevailing in the Manga Grasslands. The problems of lags between climate and vegetation change and the presence of extrazonal vegetation, experienced in the Manga Grasslands, are likely to be common to other Sahelian pollen sites. The palynological information presently available for this zone is deemed insufficient for detailed subcontinental scale reconstructions of vegetation and climate to be attempted.

Signification bioclimatiquede taxons-guides du Pliocène méditerranéen

The climatic reconstruction of the Pliocene, based on pollen data, requires a new method of quantification011 because of the presence in pollen spectra, of temperate, warm-temperate but also subtropical plants. As no modern pollen spectra contain all these taxa, the best analogues method is inappropriate for this period. So, a new method is proposed: it corresponds to a climatic amplitude method modified to partially take into account some taxa abundances. The first step in this new method is to determine the present-day distribution of a few subtropical plants and some taxa still existing in the Mediterranean region with a good climatic signal. Then the climatic parameters of the corresponding areas are defined, either by a climatic atlas or by personal knowledge. A test on a few pollen spectra, corresponding to different localities but of almost the same age (about 3.4 Ma) is realised. The first results of climatic estimation confirm an increasing latitudinal gradient for annual temperatures from North to South, which is estimated as today, even if the temperatures were higher (about 2 to 6° C more). We may confirm the same for the precipitations which were more important to the North than to the South of the Mediterranean. These latitudinal gradients are quantified.

Fire history and composition of the subalpine forest of western Colorado during the Holocene

Pollen and plant macrofossils from the Keystone Ironbog are used to document changes in species composition and the dynamics of the subalpine forest in western Colorado over the past 8000 years. Modern pollen spectra (particularly pollen influx), plant macrofossils, observations on modern species composition, and quantified densities and mean basal areas of forest trees are used to interpret the paleoecology of the forest. From 8000 to 2600 years ago the fen was surrounded by a subalpine forest. However, unlike the modern subalpine forest where Abies lasiocarpa (Hooker) Nuttall is slighlty more abundant than Picea engelmannii (Parry) Engelmann, these Holocene forests had a greater dominance of P. engelmannii, perhaps reflecting a summer wet climate like that of the modern southern Rocky Mountains and Colorado Plateau. Mesic conditions promoted a dense understory of Sphagnum moss, forbs, grasses, and shrubs which periodically burned with long (centennial) return‐interval and stand‐replacing fires. Populus tremuloides Michaux was the dominant successional forest tree 8000–6400 and 4400–2600 years ago, with Picea engelmannii and Abies lasiocarpa becoming reestablished within a couple hundred years. A subalpine meadow or grassland covered the fen for about 2000 years between 6400 and 4400 years ago. Over the past 2600 years a stable, non‐successional Pinus contorta (Douglas) spp latifolia (Engelmann) Critchfield forest grew around the fen. This forest stand had a relatively sparse understory. The persistence of Pinus contorta at this elevation (2920 m) probably reflects a shift to drier climatic conditions, perhaps coupled with a change in fire regime to relatively frequent (decadal) surface fires. Following fire Pinus contorta became reestablished at least within 200 years, but the subalpine Picea engelmannii‐Abies lasiocarpa forest never regenerated at this elevation

Modern pollen spectra from Costa Rica

Abstract We analyzed pollen spectra preserved in surface lake and mire sediments and soils to provide information on modern pollen rain across a range of vegetation types in Costa Rica. We collected samples at 29 sites located within ten principal vegetation types: mangrove, tropical dry forest, derived savanna, tropical moist forest, tropical wet forest, lowland freshwater swamp, premontane rain forest, montane rain forest, montane bog, and paramo. Samples from sites with similar vegetation generally had similar pollen assemblages and clustered together in detrended correspondence analysis. Results indicate that major vegetation types in Costa Rica have distinct pollen spectra.

Micro‐scale patterns of modern pollen deposition within three alpine plant communities*

summaryFew studies have examined patterns of pollen deposition or the relationship between vegetation and pollen assemblages at the small scale. This paper examines the representation of both individual taxa and whole plant communities in modern pollen spectra. Micro‐scale variations in modern pollen deposition were studied in three alpine plant communities on Storbreen glacier foreland, southern Norway: a pioneer community; a Salix‐shrub community; and an ericaceous heath community. The relationships between vegetation and modern pollen deposition and the variability of these relationships at the local scale were investigated within 16 × 1 m2‐quadrats. The data were classified using two‐way indicator‐species analysis (TWINSPAN) and ordinated using detrended‐correspondence analysis (DCA). In addition, the pollen and vegetation data were ordinated simultaneously, using canonical correspondence analysis (CCA). The effect of removing arboreal pollen from the pollen sum was examined. The three plant communities were distinguished successfully by multivariate statistical techniques, using; both pollen data and vegetation data. However, within the communities there was high variability in pollen deposition, which was most pronounced in the Salix‐shrub community. The abundance of individual taxa in the vegetation was compared with their representation in the pollen spectra. The strongest relationships were shown by Salix Ericales, Empetrum and Lycopodium. Certain taxa showed consistent, reproducible patterns of behaviour. These patterns provided valuable evidence for separating contrasting plant communities. Comparison of modern pollen‐vegetation relationships of this kind with pollen data from Holocene and Pleistocene sites is important to improve the reconstruction of past plant communities. Statistical analyses showed that for the majority of taxa a moss polster consisting of 20 subsamples was necessary to reduce the effect of microscale variability in this environment to acceptable levels.

Modern Pollen Spectra and Vegetation of Mt Hauhungatahi, Central North Island, New Zealand

Moss samples from a range of plant communities on an altitudinal gradient from montane forest to subalpine tussockland and a transect along the tree-line on Mt Hauhungatahi were analysed for pollen content to quantify modern pollen/vegetation relationships. Cluster analysis of pollen percentages from the sites indicated five distinctive vegetation types: (1) montane forest, (2) subalpine forest, (3) subalpine scrub, (4) subalpine fernland and (5) subalpine tussockland. Ordination arranged sites along an open to densely structured vegetation gradient, i.e. from fernland and tussockland to forest and dense scrub. Stepwise discriminant analysis selected the pollen proportion of Myrsine (subalpine scrub), GGleichenia (subalpine fernland), Libocedrus (subalpine forest) and Restionaceae (subalpine tussockland) as highly discriminatory variables in relation to vegetation type. High Weinmannia, Nestegis and Cyathea smithii-type pollen values characterized the montane forest. Comparison of basal area and pollen data for sites in forest indicated Phyllocladus, Weinmannia, Nestegis, Coprosma and Cyathea smithii-type were overrepresented. Dacrydium, Podocarpus, Halocarpus and Libocedrus were under-represented. Comparing pollen with basal area within forest sites, two out of five sites showed a significant positive correlation between species ranked by basal area and pollen. Across forest sites, Phyllocladus, Nestegis, Dacrydium and Coprosma pollen counts showed a significant positive correlation with basal area

Modern Pollen Spectra and Vegetation in the Wind River Range, Wyoming, U.S.A.

Modem pollen spectra provide a picture of vegetation communities in the Wind River Range. The broad valleys of western Wyoming, which are covered by big sagebrush steppe, are dominated by Artemisia pollen (averaging 75%) with lesser amounts of Pinus, Tubuliflorae, Gramineae, Chenopodiaceae-Amaranthus, and Ambrosia pollen. The majority of the pollen deposited in the Artemisia steppe comes from local plants. Although all the forests in the Wind River Range are dominated by Pinus contorta-type pollen, each forest type has a unique palynological signature. Populus tremuloides forest stands produce up to 5% Populus pollen. Pseudotsuga menziesii is not widespread in the southern part of the range, and its pollen is most abundant (1%) near where the trees grow. Pinus contortatype pollen (over 80%) dominates Pinus contorta forest stands. Picea and Abies trees in the mixed conifer forest are represented by low, but significant pollen percentages, 3 and 0.5%, respectively. The Pinus albicaulis parkland represents a transitional forest community between the mixed conifer forest and alpine tundra. Palynologically it is indistinct from alpine tundra. While over 50% of the pollen deposited in alpine tundra comes from lower elevations, tundra can be characterized by its relatively high frequency of herbaceous pollen (17%) and significant amounts of Cyperaceae, Gramineae, Tubuliflorae, Salix, and Bistorta pollen from local plants.

Modern pollen spectra and contemporary vegetation in the Paramera mountain range (Avila, Spain)

Modern pollen data of four transects across the Sierra de la Paramera (Avila) are presented. A comparison between these data and the contemporary vegetation shows that the pollen spectra faithfully reflect the taxa present in the study area, their low percentages being explained by the sparse vegetation cover. The study concentrates on the main taxa and attempts to determine the effects of topography and wind direction on the transportation and sedimentation of pollen grains.

Modern pollen spectra and vegetation in southern Ontario, Canada

A weekly census of air borne pollen grains was conducted for three years (1983–1985) at four sampling stations (from north to south: Sudbury, Peterborough, Toronto and London) in the Great Lakes region, southern Ontario, Canada.A Cour volumetric vane sampler was used at each site, located at the respective meteorological station, providing pollen spectra from an area of surrounding vegetation with an estimated radius of 40 km. Filter samples were processed by a standard, established procedure.The study area forms part of the Upper Canada Peninsula vegetation region. Two sites, Sudbury and Peterborough, occur in one of the two major vegetation zones, the Mixed-Hardwood; the others, Toronto and London, are located in the second zone, the Deciduous Forest.Previous studies of pollen-vegetation relations in this region were based on analysis of moss polsters. The pollen trap method used here provides a more sensitive registration of regional pollen and while the seven most important taxa quantitatively are found in the both data sets, such important taxa as Cupressaceae and Populus are under-represented or absent in polster data because of poor preservation, but well represented in the trap analyses (Cupressaceae at 9% and Populus at nearly 3%). Similarly, some spore taxa that are absent from previously published results occur in the present data in significant frequencies (Lycopodium at 4% from Sudbury and Sphagnaceae from all stations).The results of statistical analyses show the predictable major change in the regional pollen spectra between Sudbury and Peterborough.

Comparison of modern pollen spectra with fossil pollen data on the island Stora Karlsö, western Baltic Sea, Sweden

Comparison of modern pollen spectra with fossil pollen data on the island Stora Karlsö, western Baltic Sea, Sweden

Numerical interpretation of a high resolution Holocene pollen record from Burundi

The Holocene history of the tropical montane forest is reconstructed using a high resolution pollen record from a valley swamp (3°35′S, 29°41′E), at 2000 m elevation. The post-glacial establishment of the montane rain forest is evidenced at ca. 10,600 yr B.P. Numerical analysis combines the Correspondence Analysis with the Cluster Analysis of both 38 modern and 101 fossil pollen spectra including 125 identified pollen taxa. Four distinct successionnal stages of forest development have been identified. The past vegetation recorded during the early Holocene period (10,600–3800 yr B.P.) was more closely related to modern pollen spectra from secondary forest rather than to primary forest samples from Burundi. At 3800 yr B.P., a sharp decrease of arboreal pollen percentages and a noticeable increase of Celtis, a semi-decidous tree indicate the opening of montane forest due to a drier climatic event. The beginning of the anthropogenic impact evidenced after at 3500 yr B.P., contemporaneously with the Early Iron Age in Burundi, follows the late Holocene climatic shift.

Deposition of modern pollen and plant macroremains in a hypersaline prairie lake basin

Comparisons between current vegetation patterns and deposition of modern pollen and plant macroremains in a saline lake basin on the northern Great Plains are used to assess the value of plant remains as indicators of past local vegetation dynamics and lake-level changes. Results indicate that both modern pollen spectra and assemblages of plant macroremains reflect clearly the composition of the local vegetation, whereas plant macroremains best reflect lake size. Cactaceae pollen and seeds are confined to upland prairie deposits. Liguliflorae (Compositae) and Leguminosae pollen, Selaginella densa microspores, and Euphorbia and Cruciferae seeds are more abundant in prairie upland deposits than in shoreline or lacustrine environments. An abundance (> 50%) of Ruppia pollen distinguishes near-shore lake sediments, indicating that this taxon is a useful marker of shallow shoreline environments in saline lakes. Seeds of Chenopodiaceae, Erigeron, Cruciferae, and Cyperaceae, as well as Chara oogonia, are more abundant in near-shore lacustrine sediments than in the central lake area, suggesting that they too are indicators of shoreline proximity. These data are useful for paleobotanical reconstructions of past lake-level dynamics. Key words: saline lakes, Great Plains, pollen, paleobotany, paleohydrology, environmental reconstruction.

Modern pollen deposition in cave sites: experimental results from New York State

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

Remote sensing and modern pollen dispersal in Southern Patagonia and Tierra Del Fuego (Argentina): Models for palaeoecology

Abstract A method is proposed for calibrating modern pollen data in terms of remote sensing data. It includes numerical techniques familiar to the pollen analyst, remote sensing data and a simple although robust technique of model testing. The method allows the calibration of equations to predict radiometric data in regions (such as Southern Patagonia) where the paucity of modern climate data is a major obstacle for research in palaeoclimatology. Remote sensing data from the National Oceanic and Atmospheric Administration (NOAA-9) Advanced Very High Resolution Radiometer (AVHRR) [Channels 1 (.58 to .68 μm) and 2 (.725 to 1.1 μm)], were used to calculate albedo values. These values were used to (1) calculate simple ratio (SR) and Normalized Difference Vegetation Index (NDVI), and (2) to calibrate them in terms of the modern pollen spectra of 74 sites of Southern Chubut, Santa Cruz and Tierra del Fuego, to produce predictive models. The data sets were then split so that one half of the data predicted the ra...

Représentation pollinique actuelle à la limite des arbres au Nouveau-Québec

Modern pollen spectra from a series of lakes in northwestern Quebec reflect the major vegetation zones of the forest–tundra transition from latitude 55°N to 59°N. Shrub tundra samples are dominated by Betula and herb pollen, whereas Picea percentages are between 10 and 20%. Lichen woodland samples can contain over 60% Picea, with Betula and Alnus crispa each less than 20%. Pollen assemblages from the shrub subzone of the forest–tundra resemble those of the shrub tundra, while those from the forest subzone resemble lichen woodland samples. Maximum percentages of Alnus crispa are found in the forest–tundra. Classification of the samples using cluster analysis and an ordination by principal coordinates analysis suggest that densely and sparsely forested regions can be discriminated.

Modern pollen deposition in West African Sudanian environments

A set of modern pollen spectra from Senegal and from Togo (79 soil surface and river mud samples studied; 200 pollen taxa recorded) fills a gap in the record for the Sudanian zone of North Tropical Africa. The pollen spectra primarily record the local and regional vegetation: taxa from tropical trees are numerous but their relative values are low, often less than 1%. Herbaceous taxa such as Gramineae and Cyperaceae reach the highest percentages (maximum = 94 and 37% respectively). Long-distance transported pollen from extra-regional vegetation are almost absent. Palynological characterization is attempted of such specific vegetation associations as dry and wet Combretaceae woodlands and the Isoberlina association. Human impact and recent (climatologically induced) deterioration of vegetation is recorded, reflecting the present-day sensitivity of the Sudanian zone.