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Wheatfen Pollen Survey 2001 Heather Binney

Modern Pollen/Vegetation Investigation at Wheatfen - Part 1

Some of you may have noticed the wooden pegs and plastic flagging in the woodland at Wheatfen this year. These are a part of a research project being undertaken by a team from Kingston and Hull Universities (Dr Martyn Waller, Dr Jane Bunting and Dr Heather Binney). We are palynologists, that is, we are interested in pollen and in particular fossil pollen which can provide a record of how vegetation has changed over time (over several thousand years in some cases). A good source of fossil pollen is peat and in Norfolk peat has accumulated on some of the flood plains such as at Wheatfen. However, in order to make more accurate reconstructions of the past vegetation using fossil pollen, it is necessary to gain a better understanding of the present relationship between the plants that grow in the area (including both the wet and dry land vegetation) and the resulting pollen signal or 'pollen rain'. The modern pollen rain can be measured by sampling small moss mounds (known as polsters) which trap and preserve a record of the pollen over several years. We are investigating two sites in Norfolk - Wheatfen Broad and Calthorpe Broad near Hickling (this provides a good comparison as it has an alder dominated carr and does not have the tidal influence found at Wheatfen). In June and July this year we selected approximately 100 moss polsters at Wheatfen located both in the wet willow carr and the drier Surlingham Wood. At each site we recorded in detail the ground flora and the tree canopy composition within a 4m-diameter circle centred on the moss polster. A hand-held GPS receiver helped us to locate the sites for mapping purposes - however the accuracy of the grid references was often limited by the dense tree canopy cover which interfered with the signals from the tracking satellites. In September, towards the end of the flowering season, we returned to all the sites to collect the moss samples. This was a relatively easy task and involved locating the moss polsters and giving them a haircut! The "haircut" represents about 2-3 years and therefore provides an average record of the pollen rain for that period. The autumn was spent preparing the moss samples in the laboratory to extract the pollen; we spent many hours looking down a microscope counting the different types of pollen grains (usually identifiable to generic and sometimes species level). In February we will return to Wheatfen with a more sophisticated GPS receiver which, together with the reduced tree canopy, will help us to obtain more accurate locations for the sampling sites. One particularly novel aspect of this research is that it provides a method for analysing the spatial nature of the vegetation and pollen data using a computer-based Geographic Information System (GIS). The results should be complete by May 2002.

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