In the wake of topical research issues such as global change and energy resources, one can recognize two priority targets for the study of fossil plant remains: - insight into the role of land plants and phytoplankton as monitors, recorders, motors and moderators of climatic and environmental change; -insight into the predictive value of organic remains with respect to genesis, composition, occurrence, quality and quantity of fossil fuel reserves. In harmony with these targets, current research at the Laboratory of Palaeobotany and Palynology (LPP) is aimed to provide for basic contributions to the palaeoecological study and interpretation of Palaeozoic, Mesozoic and Cenozoic plant life. Four interconnected areas of scientific emphasis are currently distinguished: - biotic change: documentation and causal analysis of changes of past plant biota in terrestrial and marine environments, both at short and long time-scales; - selective preservation: identification of the biological, physical and chemical factors that determine selective preservation of organic matter during transport, sedimentation and burial; - methodology: development and introduction of new analytical methodology relevant to the study and interpretation of fossil plant remains; - systematics: generation and compilation of systematic data aimed at the accurate identification and classification of fossil plant remains. Overview of results LPP strives after a balance between the study of land plant remains and organic-walled marine phytoplankton (mainly dinoflagellates). Research objectives are related to both short (latest Pleistocene-Holocene) and long time-scales (late Palaeozoic-Cenozoic). Short time-scales Modern land plant communities can be understood only in the light of their history since the onset of the last deglaciation (15,000 yr BP). In western and southern Europe this history is governed by the climatically induced spread of forest communities and their subsequent recession as man's influence expanded. Through fine-scale analysis (temporal and spatial, as well as systematic), of assemblages of microscopic and macroscopic plant remains, research concentrates on the accurate discrimination between autogenic, climatically induced, and anthropogenic vegetational change in contrasting physiographic entities: (1) crystalline mountains in France and the Iberian peninsula; (2) landscapes characterized by Pleistocene-Holocene eolian (sand, loess) deposition in the Netherlands and Germany; (3) fluvial plains in the Netherlands; (4) littoral landscapes in Portugal, and (5) Arctic landscapes of Spitsbergen, Jan Mayen and Greenland. Following earrlier research experiences with respect to the palaeoecological analysis of pollen assemblages from the Vosges (France), in the research period special attention was given to deciphering the complex, altitude related, late Pleistocene-Holocene pollen signals from other low mountain ranges. Results have demonstrated that the spatial distribution of vegetation patterns can be followed through time by recognizing: (1) common time-proportionate trends in pollen values, and (2) local pollen components characteristic for altitudinal vegetation zones and lake/mire development. Long time-scales For the recognition and evaluation of biotic change on long time-scales, LPP concentrates on the study of land plant and phytoplankton records from sedimentary successions that contrast with respect to: (1) time of formation (selected late Palaeozoic, Mesozoic and Cenozoic intervals); (2) paleotectonic and palaeogeographic history (intracratonic; passive and active plate margins); (3) depositional environment (terrestrial to deep-marine); and (4) biogeographic provinciality. Temporal and spatial distribution patterns of plant remains are explored for proxy variables indicative of terrestrial and marine environmental change. Investigated variables include land temperature, humidity, precipitation, runoff, sea-level, sea surface temperature, salinity, nutrient supply, productivity, organic burial rate and CO2 level. In the review period particular attention has been given to the development of palaeoecological models of dinoflagellate cyst distribution in marine sediments. It has been shown that: (1) the potential of dinoflagellates in Mesozoic and Cenozoic time-resolution may frequently exceed that of planktonic foraminifera and calcareous nannoplankton, and (2) dinoflagellates can be applied in novel ways to further the environmental understanding of depositional sequences and sedimentary cycles defined by physical (seismic, sedimentological) analysis. Although research related to global change programmes is generally restricted to the Late Tertiary-Quaternary, there is one notable exception. It is recognized that a better understanding of the patterns and processes of past mass extinctions can contribute to an understanding of present and future man-induced extinction processes. Work by LPP concentrates on the profound biotic crises at the Permian/Triassic (P/Tr) and Cretaceous/Tertiary (K/T) junctions. Study of the P/Tr land plant record has now revealed ecosystem collapse in the terrestrial biosphere. At the K/T junction, it has been demon-strated that dinoflagellates have remained immune to extinction. Independent of configurations predicted by meteorite-impact or massive volcanism, therefore, palynological studies enable high-resolution reconstruction of environmental change, both during pre-crisis times and the phases of K/T ecosystem decline and recovery.
organic petrology, quantitative cuticle analysis, spectral analysis, archive intercalibration,
Development and introduction of new methodology relevant to the study and interpretation of fossil plant remains has always played an important role in the research philosophy of LPP. The following methodological aspects are emphasized: Organic petrology Organic petrology comprises a number of methods aimed at analysing physical properties of organic matter that change irreversibly during transport and burial. Data acquisition requires the use of sophisticated analytical (microscopic, photometric, computational) equipment, for which LPP could appeal to the Geological Survey of The Netherlands (RGD). In order to stimulate full integration of organic petrological methodology in academic research, NWO and the Faculty of Biology have recently allocated investment subsidies for purchasing relevant equipment. Quantitative cuticle analysis Physiological responses of plants to changes in the supply of basic resources (solar radiation, C02, water, nutrients) require morphological, anatomical and/or biochemical adjustments. If physiologically determined adjustments can still be discriminated in fossil plant remains, their temporal analysis may provide a palaeophysiological methodology for quantifying past environmental change. Considering a direct correlation between atmospheric C02 concentration and stomatal frequency, LPP has carried out succesfully research aimed at exploring the potential of quantitative cuticle analysis for estimating changes in CO2 levels during contrasting climatic intervals within the last 10 Ma. Spectral analysis Spectral analysis provides an objective method for the detection of regular cyclicity in high-resolution temporal data sets (time series), recording some oscillating parameter. Band-pass filtering of time series can be used to extract and illustrate individual cycles with contrasting periods that have been identified on a power spectrum. Time series of palaeontological, geochemical and sedimentological proxies are increasingly investigated for environmental and climatic effects of the variation in insolation caused by cyclic changes in the orbit and axis of rotation of the Earth. LPP has adopted this methodology to test its potential with respect to the interpretation of high-resolution palynomorph records from Mesozoic and Cenozoic marine sediments. The method has already become an integral aspect of palynological research in the Pliocene. Extensive Middle Triassic data sets are now being standardized for computation. Archive intercalibration Historical archives constitute a source of primary information on nature and magnitude of human impact on local and regional environments. Filed documents provide well-dated descriptive and quantitative records of a variety of anthropogenic variables, such as land-use, landscape and water-balance management, population density and industrial activities. In addition, historical archives can be consulted for continuous weather observations. LPP regards intercalibration of historical and sedimentary records as a methodology of fundamental importance to the accurate registration and understanding of man-induced ecosystem change. At present, development of such methodology is promoted through integrated historical/palaeoecological studies covering the past few centuries, a period with significant changes in both climate (ending of Little Ice Age, commencement of recent global warming) and human socio-economics (agrarian and industrial revolutions). Systematics' - Northwest European Pollen Flora As a comprehensive systematic background for palynological research in NW Europe, LPP initiated in 1974 the Northwest European Pollen Flora (NEPF). Through detailed pollen morphological analysis, this long-term project provides for standardized description and high-quality SEM- and photomicrography of pollen grains of all extant NW European vascular plant species. DinoSys In order to provide for computerized documentation of approximately 4000 dinoflagellate cyst species, LPP introduced in 1990 DinoSys. This project includes (1) development of a data base management program, customized to applied dinoflagellate cyst research, for handling multiple related descriptive files and digitized images, and (2) data base storage per species, of pre-evaluated (taxonomic, stratigraphic, geographic) information together with high-quality video-generated colour images.