Disentangling the pollen signal from fen systems : Modern and Holocene studies from southern and eastern England

Waller, Martyn P. and Carvalho, Fabio and Grant, Michael J. and Bunting, M. Jane and Brown, Kerry A. (2017) Disentangling the pollen signal from fen systems : Modern and Holocene studies from southern and eastern England. Review of Palaeobotany and Palynology, 238. pp. 15-33.

Abstract

Thick deposits of peat derived from fen environments accumulated in the coastal lowland areas adjacent to theNorth Sea during the middle and late Holocene. These sediments are frequently used in pollen-based reconstruc-tions ofin situand more distant vegetation. However, discriminating between wetland and dry land originatingpollen signals, and between the potential fen communities present in the wetland, is complex. In this study, asuite of analytical approaches are used to explore the pollen signal of modern fen communities and comparethem against Holocene pollen assemblages. At two sites in eastern England, Woodwalton Fen and UptonBroad, vegetation composition was recorded around a series of moss polster sampling points. The communitiesinvestigated included herbaceous fen communities under different cutting regimes, a grazed area, glades, andwoodland with canopies dominated byAlnus glutinosaandBetula. Cluster analysis is used to provide an overviewof, and compare the structure within, the datasets consisting of the vegetation, the vegetation converted to pal-ynologicalequivalents, and thepollen data.Itis demonstratedthat any loss of taxonomic precision in pollen iden-tifications does not pose particular problems when attempting to identify fen communities, including tall-herbaceous vegetation, in the pollen record. Indices of Association imply pollen presence can be interpreted asindicating the local presence for some taxa, though few of these are confined to a particular community. Herba-ceous fen vegetation subject to different management regimes are, however, shown to produce distinctive pollensignatures. Middle and late Holocene pollen assemblages from eastern (Fenland) and southern (Romney Marsh)England, interpreted as derived from fen vegetation, are compared against the modern pollen dataset using or-dination.Mostof the fossilsamples plot out within or adjacent to the groupings produced by the modernsamplesin the ordinations. While these investigations demonstrate that modern pollen work can help improve the inter-pretation of Holocene assemblages they also call attention to a number of limitations including the restrictedrange of communities from which modern samples are currently available and the potential for non-analogousmodern vegetation. The paper concludes with ideas to aid the interpretation of pollen data collected from fenpeats and suggestions for future work.