254 research outputs found

    Annual pollen traps reveal the complexity of climatic control on pollen productivity in Europe and the Caucasus

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    Annual PAR (pollen accumulation rates; grains cm−2year−1) were studied with modified Tauber traps situated in ten regions, in Poland (Roztocze), the Czech Republic (two regions in Krkonoše, two in Šumava), Switzerland (4 regions in the Alps), and Georgia (Lagodekhi). The time-series are 10-16years long, all ending in 2007. We calculated correlations between pollen data and climate. Pollen data are PAR summarized per region (4-7 traps selected per region) for each pollen type (9-14 per region) using log-transformed, detrended medians. Climate data are monthly temperature and precipitation measured at nearby stations, and their averages over all possible 2- to 6-month windows falling within the 20-month window ending with August, just prior to the yearly pollen-trap collection. Most PAR/climate relationships were found to differ both among pollen types and among regions, the latter probably due to differences among the study regions in the habitats of plant populations. Results shared by a number of regions can be summarized as follows. Summer warmth was found to enhance the following year's PAR of Picea, Pinus non-cembra, Larix and Fagus. Cool summers, in contrast, increase the PAR of Abies, Alnus viridis and Gramineae in the following year, while wet summers promote PAR of Quercus and Gramineae. Wetness and warmth in general were found to enhance PAR of Salix. Precipitation was found to be more important for PAR of Alnus glutinosa-type than temperature. Weather did not have an impact on the PAR of Gramineae, and possibly of Cyperaceae in the same year. Care is advised when extrapolating our results to PAR in pollen sequences, because there are large errors associated with PAR from sediments, due to the effects of taphonomy and sedimentation and high uncertainty in dating. In addition, in pollen sequences that have decadal to centennial rather than near-annual resolution, plant-interaction effects may easily out-weigh the weather signa

    Modern pollen rain–vegetation relationships along a forest–steppe transect in the Golestan National Park, NE Iran

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    Pollen rain-vegetation relationships were studied over a forest-steppe transect in Golestan National Park, NE Iran. The surface pollen percentages were compared to the vegetation composition of the respective vegetation types in 18 sampling points using both descriptive and numerical approaches. Hyrcanian lowland forests are characterized by pollen assemblages dominated by Quercus, Carpinus betulus and low frequencies of Zelkova carpinifolia. Both Parrotia persica and Zelkova carpinifolia show a very low pollen representation in modern surface samples, an under-representation that should be taken into account in the interpretation of past vegetation records. Transitional communities between the forest and steppe including Acer monspessulanum subsp. turcomanicum, Crataegus and Paliurus scrubs, Juniperus excelsa woodlands and shrub-steppe patches are more difficult to distinguish in pollen assemblages, however, they are characterized by higher values of the dominant shrub species. The transitional vegetation communities at the immediate vicinity of the forest show also a substantial amount of grass pollen. Many insect-pollinated taxa are strongly under-represented in the pollen rain including most of the rosaceous trees and shrubs, Rhamnus, Paliurus, Acer and Berberis. Artemisia steppes are characterized by very high values of Artemisia pollen and the near absence of tree pollen
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