摘要:

The patterns of pollen deposition in the upper layers of the soil and in biological traps (mosses and lichens) in relation to the widespread and well known vegetational types of the Alps is investigated. The communities studied are beach woods, pine woods (Pinus cembra, P. sylveslris) and alpine pastures. Quantitative correlations between the pollen spectra and the vegetation have been calculated and over, under and equi-represented species delimited. Since representativity differs, in some cases, from that recorded in the literature it is suggested that it would be useful to continue the study in order to improve our understanding of actual pollen deposition and, as a consequence, of the interpretation of fossil pollen data.

ISSN:0017-3134    

DOI:10.1080/00173139109431983

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Modern pollen-vegetation relationships have been explored in recent years through analysis of either pollen trap (= absolute results) or moss polster contents (= relative results). In the past few attempts were made to compare data from these two sources. It was the aim of the present study to achieve this comparison through more exact sampling of moss polsters. A pilot study was carried at Morton Lochs, Fife, Scotland where pollen traps have been sampled continuously for ten years. Moss samples were collected from cushions adjacent to two of the pollen traps during May 1985, 1986 and 1987. Moss polsters were sampled usingan equivalent surface cross-section area to that of the traps. In comparing the pollen results from the two sources some similarities can be identified, but in general there are more inconsistencies. These may be traced to difficulties in the precision of moss sampling, variable rates of moss growth and local deposition factors. It is considered that further study, in which these difficulties are minimised, would be justified. Ultimately it is hoped that precise sampling of mosses will produce sufficiently reliable modern pollen rain results to enable pollen-vegetation studies to move away from relative (percentage) values without requiring long-term artificial pollen trapping techniques.

ISSN:0017-3134    

DOI:10.1080/00173139109431984

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The annual sums of daily airborne pollen concentrations fluctuate from year to year. It has been suggested that for some taxa there is a regular or alternating pattern in these fluctuations. On the other hand, environmental changes may lead to decreasing or increasing trends in airborne pollen concentrations. These two phenomena can only be studied reliably on the basis of long-term volumetric observations of abundantly occurring pollen types. For this study two arboreal (BetulaandQuercus) and two herbaceous (Poaceae andUrtica) types were chosen.

ISSN:0017-3134    

DOI:10.1080/00173139109431985

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A brief account is given documenting the development of aerobiological research in the Antarctic. The results of the British Antarctic Survey's contribution to an international programme on long-distance dispersal of aeroplankton over the Southern Ocean are presented. This was achieved by collecting airspora deposited in Tauber traps and in surface snow at sites on South Georgia (sub-Antarctic) and Signy Island (maritime Antarctic). Although only a small number of the samples were analysed, the results provided ample evidence of a continuous immigration of exotic sporomorpha of southern South American provenance. The cause of this rain of biological material is attributed to the not infrequent easterly tracking storm events generated over the south-east Pacific Ocean. As they gain momentum over southern South America they become seeded with pollen and spores, and possibly by larger organelles such as invertebrates and seeds. These high winds may be deflected southwards by a blocking anticyclone over the South Atlantic Ocean, allowing a proportion of the sporomorpha to be deposited over land far to the south. The occurrence of such exotic sporomorpha in these remote and environmentally hostile regions is used here as evidence to support the hypothesis that there is a continuous input into the Antarctic biome of viable propagules from more northerly landmasses. While no exotic bryophyte or lichen spores have yet been detected in trapping experiments, the extremely rare occurrence of certain bryophytes associated only with geothermal sites in the Antarctic and in laboratory-cultured soils from barren ice-free terrain indicates that a pool of viable but dormant propagules is probably widespread in Antarctic soils and ice. However, germination and developmentin situare possible only under exceptional environmental circumstances. An international programme is being planned to detect the main trajectories of long-distance transport of propagules into the Antarctic and to test their viability.

ISSN:0017-3134    

DOI:10.1080/00173139109431986

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The fynbos biome of southern Africa is floristically diverse and explanations of this diversity have frequently invoked historical processes, in particular environmental change. Few sites exist within the region which facilitate palaeoecological reconstructions, but a relatively deep sequence of organic sediments in the Cederberg mountains in the south-western Cape Province of South Africa has been analysed for fossil pollen content. Conventional zonation of the resultant absolute pollen diagram reveals an apparent absence of marked vegetation change during the last 14500 years. Pollen analysis has its limitations under circumstances where the high plant diversity and incompleteness of reference material entails that pollen identifications may usually be made only down to family level. In order to assess whether the presumed stability of vegetation communities during the late Pleistocene and Holocene is an artefact of these taxonomic limitations, a comprehensive contemporary pollen sampling programme was conducted. Multiple discriminant analysis was applied to the contemporary data and suggests that contemporary pollen spectra are accurate reflections of the surrounding vegetation. Discriminant analysis is further able to identify analogue communities prevailing at various times during the sedimentation period. Rather than being truly stable, the vegetation of these mountains is shown to have been dynamic in response to changes in precipitation inputs, fire regime and human activity. Nevertheless, the vegetation history is characterised by relatively subtle changes in plant community patterns, a fact which may have played an important role in the evolution of prolific species diversity. It is concluded that contemporary pollen rain studies, combined with multiple discriminant analysis, may be especially valuable interpretive tools in situations of high plant species richness.

ISSN:0017-3134    

DOI:10.1080/00173139109431987

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:0017-3134    

DOI:10.1080/00173139109431988

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The results of palynological analyses from the Mérida Andes, Venezuela, from seven stratigraphic sections covering the last 13,000 years are discussed. An interpretation of the climate and vegetation for this time interval shows that the composition of the high montane vegetation and its altitudinal position was not constant during the Late Quaternary, the climate changed at the end of the Pleistocene and there were small oscillations during the Holocene.

ISSN:0017-3134    

DOI:10.1080/00173139109431989

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Within the Southeast Caucasus mountain forest 79 moss samples were collected along three unbroken transects and compared to the forest composition within these transects. Forest estimates were obtained for 79 groups of nested sections of the transects, each group centered on a moss sample. The forest plot bearing the maximum pollen-vegetation correlation (MPVC) for all taxa was found to be 60–100 m long. The MPVC plots for 10 individual taxa differed predictably according to pollen transportability, which shows the significance of wind dispersion even under the dense canopy. Big and/or poorly dispersed pollen types (Parrotia, Zelkova, Diospyros, Acer) had a MPVC plot about 20 m long while, for the better dispersed pollen ofAlnus, Quercus, Fraxinus, CarpinusMPVC plot size ranged between 100 and 220 m long. The spatial pattern of tree population as well as the pollination strategy also affects the MPVC area.Alnusgrows patchily along the streams and its pollen appears to be less transportable when compared with the more smoothly distributedCarpinus. InsectpollinatedAcerhas relatively small but poorly dispersed pollen. The montane relief may, presumably, also control pollen dispersion and representation.

ISSN:0017-3134    

DOI:10.1080/00173139109431990

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

In earlier works we have investigated the correlation between aerobiological and phytogcographical data, assessing the presence and number of the most important allergenic taxa in our area. More recently we have enquired into the relationship between phenological and aerobiological phenomena, checking the flowering period of the allergenic species growing in different ecological stations.

ISSN:0017-3134    

DOI:10.1080/00173139109431991

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

In the Iberian Peninsula and Balearic Islands there are several bioclimatic regions which result in many different and fragmentary landscapes. Results obtained from monitoring 18 localities in Spain allow an outline of the aeropollen dynamics of some of these environments. The major pollen types are: I. trees:Pinus, Qvercus, Olea, Cupressaceae, 2. shrubs:Corylus, Pislaciaand 3. herbs: Poaccae, Urticaceae, Chenopodiaceae-Amaranthaceae,Plantagoand Asteraceae. In some locationsAlnus, Artemisia, Buxus, Betula, Castanea, Eucalyptus, Populus, Ulmus, andEphedraalso have to be considered. Quantitatively, pollen from trees predominates over that from herbs and shrubs, although at some localities this trend varies. The first pollen grains found in the weekly atmospheric analyses are from trees (winter). In spring tree pollen grains share the atmosphere with herb pollen. For this reason it is usual to find peak values of pollen content in the atmosphere during this part of the year, while winter and autumn are characterized by low pollen counts.

ISSN:0017-3134    

DOI:10.1080/00173139109431992

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor