Abstract for presentation at XVII INQUA Congress 2007

Exploring Holocene European vegetation history with the vegetation model LPJ-GUESS forced with GCM climate scenarios

  • Thomas Giesecke, Geological Survey of Denmark and Greenland (GEUS), 1350 Copenhagen K, Denmark, Denmark
  • Paul Miller, Geobiosphere Science Centre, Department of Physical Geography and Ecosystems Analysis, Lund University, 223 62 Lund, Sweden, Sweden
  • Thomas Hickler, Geobiosphere Science Centre, Department of Physical Geography and Ecosystems Analysis, Lund University, 223 62 Lund, Sweden, Sweden
  • Martin Sykes, Geobiosphere Science Centre, Department of Physical Geography and Ecosystems Analysis, Lund University, 223 62 Lund, Sweden, Sweden
  • Richard Bradshaw, Department of Geography, University of Liverpool, Liverpool L69 7ZT, UK, United Kingdom

    • Holocene vegetation records hold valuable information about past climate conditions. However, the interplay of different climate parameters, disturbance and species interactions make it difficult to separate out the climatic influence on vegetation dynamics. Dynamic vegetation models help disentangle the drivers of Holocene vegetation dynamics and provide an important link in the evaluation of past climate scenarios from global circulation models using pollen-based vegetation reconstructions. We evaluated the output of the dynamic vegetation model LPG-GUESS with vegetation reconstructions based on pollen profiles from selected sites in Europe to gain a better understanding of climate-vegetation interactions and to improve the vegetation model. The model was run for the last 10 000 years and forced with climate output from an atmospheric general circulation model. Outputs were compared to well-dated, high resolution pollen stratigraphies.
    Model output for sites near the limits of present-day species distributions showed similar trends to the pollen data from those sites. Sensitivity studies indicated that the observed changes were due to a combination of Holocene climate change and modelled species interaction and disturbance. These results also demonstrate that the trends in the climate forcing data present a plausible scenario for key aspects of Holocene climate change in Europe. However the mid- to late Holocene spreading of species such as Picea abies and Fagus sylvatica could hitherto not be adequately modelled as a consequence of climate forcing, even though no other explanatory factor can account for all features of their Holocene spread. Model experiments designed to test various hypotheses for controls on the population dynamics of these species help understand their Holocene history and will improve evaluations of global change scenarios.
    Evaluations of past climate scenarios with Holocene vegetation reconstructions yield good data-model matches near present-day ecotones, where the climatic control is relatively simple. However, finding the more subtle climatic triggers for mid to late Holocene species spreading may enable us to unfold another dimension of Holocene climate history.

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