Principles and methods for automated palynology

Pollen grains are microscopic so their identification and quantification has, for decades, depended upon human observers using light microscopes: a labour-intensive approach. Modern improvements in computing and imaging hardware and software now bring automation of pollen analyses within reach. In this paper, we provide the first review in over 15 yr of progress towards automation of the part of palynology concerned with counting and classifying pollen, bringing together literature published from a wide spectrum of sources. We
consider which attempts offer the most potential for an automated palynology system for universal application across all fields of research concerned with pollen classification and counting. We discuss what is required to make the datasets of these automated systems as acceptable as those produced by human palynologists, and present suggestions for how automation will generate novel approaches to counting and classifying pollen that have hitherto been unthinkable.

Quaternary pollen analysis: recent progress in palaeoecology and palaeoclimatology

During the last decade Quaternary pollen analysis has developed towards improved pollen-taxonomical precision, automated pollen identification and more rigorous definition of pollen assemblage zones. There have been significant efforts to model the spatial representation of pollen records in lake sediments which is important for more precise interpretation of the pollen records in terms of past vegetation patterns. We review the difficulties in matching modelled post-glacial plant migration patterns with pollen-based palaeorecords and discuss the potential of DNA analysis of pollen to investigate the ancestry and past migration pathways of the plants. In population ecology there has been an acceleration of the widely advocated conceptual advance of pollen-analytical research from vaguely defined ‘environmental reconstructions’ towards investigating more precisely defined ecological problems aligned with the current ecological theories. Examples of such research have included an increasing number of investigations about the ecological impacts of past disturbances, often integrating pollen records with other palaeoecological data. Such an approach has also been applied to incorporate a time perspective to the questions of ecosystem restoration, nature conservation and forest management. New lines of research are the use of pollen analysis to study long-term patterns of vegetation diversity, such as the role of glacial-age vegetation fragmentation as a cause of Amazonian rain forest diversity, and to investigate links between pollen richness and past plant diversity. Palaeoclimatological use of pollen records has become more quantitative and has included more precise and rigorous testing of pollen-climate calibration models with modern climate data. These tests show the approximate nature of the models and warn against a too straightforward climatic interpretation of the small-scale variation in reconstructions. Pollenbased climate reconstructions over the Late Glacial–early Holocene boundary have indicated that pollen-stratigraphical changes have been rapid with no evidence for response lags. This does not rule out the possibility of migrational disequilibrium, however, as the rapid changes may be mostly due to nonmigrational responses of existing vegetation. It is therefore difficult to assess whether the amplitude of reconstructed climate change reflects real climate change. Other outstanding problems remain the obscure relationship of pollen production and climate, the role of human impact and other nonclimatic factors, and nonanalogue situations.

Replicability of data collected for empirical estimation of relative pollen productivity

The effects of repeated survey and fieldwork timing on data derived from a recently proposed standard field methodology for empirical estimation of Relative Pollen Productivity have been tested. Seasonal variations in vegetation and associated pollen assemblages were studied in three contrasting cultural habitat types; semi-natural ancient woodlands, lowland heaths, and unimproved, traditionally managed hay meadows. Results show that in woodlands and heathlands the standard method generates vegetation data with a reasonable degree of similarity throughout the field season, though in some instances additional recording of woodland canopy cover should be undertaken, and differences were greater for woodland understorey taxa than for arboreal taxa. Large differences in vegetation cover were observed over the field season in the grassland community, and matching the phenological timing of surveys within and between studies is clearly important if RPP estimates from these sites are to be comparable. Pollen assemblages from closely co-located moss polsters collected on different visits are shown to be variable in all communities, to a greater degree than can be explained by the sampling error associated with pollen counting, and further study of moss polsters as pollen traps is recommended.