Through characterisation of fossil pollen grain assemblages down a sediment profile, changes through time in the local vegetation to a site can be reliably reconstructed. In this way, pollen provides an excellent record of the response of vegetation to changing palaeoenvironment.
The technique was first applied to the Lake Suigetsu sediments by our 'ancestor' project (led by Prof. Y. Yasuda, using a long sediment core, "SG93", that they retrieved in 1993). This previous project demonstrated the technique's ability to reconstruct high resolution climate changes from the site over the Late Glacial to early Holocene time period (Nakagawa et al. 2003, 2005, 2006). Quantified climate indices were inferred using fossil pollen data and the established modern analogue method (Nakagawa et al. 2002). A notable strength of this approach is that it allows reconstruction of seasonal (summer and winter) temperature and precipitation separately. This is particularly important for the Japanese archipelago, since the respective Pacific and Siberian air masses control the summer and winter climate of Japan, with monsoon circulation driven by the contrast between these air masses (see "Location").
In the "Suigetsu Varves 2006" project, pollen analysis is being undertaken at the School of Geography, Politics and Sociology, Newcastle University and at the Department of Earth Sciences, Freie Universität Berlin. We are presently aiming for high resolution analysis (15 to 50 years) of the entire laminated part of the SG06 sediment core (spanning approximately the last 60,000 years) and lower resolution analysis (< 500 years) of the remainder of the core. Major scientific targets include better understanding of the mechanisms of abrupt climate changes and millennial-scale climatic oscillations, as well as of the monsoon response to orbital forcing.
The first pollen-based article stemming from the "Suigetsu Varves 2006" project was published by Tarasov et al. (2011), which is entitled, "Progress in the reconstruction of Quaternary climate dynamics in the Northwest Pacific: a new modern analogue reference dataset and its application to the 430-kyr pollen record from Lake Biwa". This paper, although discussing another Japanese lake site (Biwa), describes the reference dataset to be implemented for pollen-based climate reconstruction from the Lake Suigetsu sediment core.
A second pollen methodology paper has been recently published by Nakagawa et al. (2013) entitled, "A standard sample method for controlling microfossil data precision: a proposal for higher data quality and greater opportunities for collaboration". Although applied specifically to the Lake Suigetsu (SG06) sediment core, the methods described are more widely applicable to pollen-based environmental reconstruction from such archives.
Visual catalogue of fossil pollen in Lake Suigetsu
Recently, Demske et al. (2013) have published a visual reference set of fossil pollen recorded within the Lake Suigetsu (SG06) sediment core. Figures from their "Atlas of pollen, spores and further non-pollen palynomorphs recorded in the glacial-interglacial late Quaternary sediments of Lake Suigetsu, central Japan" are provided below:
Part A: Lake Suigetsu Spore Flora
Part B: Lake Suigetsu Pollen Flora