Preliminary results from a survey of past vegetation communities in a transect across Romney Marsh
The Soil Survey by Green in 1968 and a stratigraphic survey funded by the Trust by Dr Antony Long in 1993 revealed the presence of a more or less continuous peat layer extending across Romney and Walland Marsh, buried for the most part by silty clays. This layer of peat contains a record of vegetation change in the form of fossilized pollen and seeds, which is being studied at Kingston University, with funding from the Trust, to identify the vegetation history of the marsh and its relation to the development of a shingle bank extending across the bay from Fairlight towards Dungeness.
The locations of the sampled sediment cores are illustrated in Figure I, together with the location of sites previously sampled by Professor Michael Tooley, Dr Antony Long and Dr Martyn Waller. Skeletal pollen diagrams have been completed on samples from The Dowels, Hope Farm and Little Cheyne Court, and current research is concentrating on detailed identification of the vegetation sequences at these sites.
Table I summarises vegetation changes at each sampling site. Results appear to show a development from marine conditions in the clay underlying the peat bed to freshwater conditions, with the development of alder fen at all three sites. At Little Cheyne Court an acidic vegetation community developed, characterised by heather and Sphagnum mosses.
Table 1. Vegetation sequences from sites along a north-south transect across Romney Marsh
Evidence at Hope Fann showed an intennittent phase of birch catT, preceding the establishment of what appears to be an acidic vegetation community. The site further north, in The Dowels, showed little or no evidence of development to acidic vegetation types. Following these successional changes, either from alder carr or from acidic communities, all sites indicated a change to communities dominated by grasses and sedges, often with evidence of reedswamp and freshwater plants.
From the data collected so far, the change from marine to freshwater conditions at the start of the sequences may relate to the fonnation of a shingle barrier growing towards Dungeness. Acidic c01mnunities then developed along the southern part of the transect, while sites nearer the upland and the degraded cliffs at the rear of the marsh appear to have maintained alder fen communities.
As the work continues, detailed investigation of pollen and seeds in sediment cores will aim to identify the composition, evolution and distribution of the acidic communities across the marsh. the vegetation These communities had not previously been identified on Marsh, so this is an important contribution to its history and evolution. Information from these investigations can then be used as a model for vegetation change in other areas.
The identification of fossilized seeds in the sediment cores at each site will be used to distinguish more clearly between the local plants g rowing on the marsh and the more regional presence of plant communities along the upland edge. The seed assemblages will be particularly useful in identifying the species of sedges present at each site. Sedges constitute an important part of a wide variety of vegetation communities and may indicate widely varying conditions. They are particularly important in the distinction between herbaceous fen and acidic vegetation community types, which is a very important distinction in the history of Romney Marsh. Fossilised algae (diatoms) in the mineral sediments above and below the peat layer will be used to identify past changes between marine and freshwater conditions.
The National Environmental Research Council has awarded us the opportunity of obtaining radiocarbon dates. By means of these, important changes in the vegetation sequence will be dated, together with the rate of the changes at each site. It will then be possible to construct a time sequence for vegetation change and assess its relationship to the development of the shingle barrier.
Deborah J. Long
