INTRODUCTION TO SALT-MARSH COMMUNITIES

Summary

The sampling and analysis of salt-marsh vegetation

The herbaceous vascular vegetation on the intertidal silts and sands of salt-marshes is one of the most frequently used illustrations of ecological pattern but there are considerable difficulties in producing an adequate national classification of the plant communities of this distinctive habitat.

First, much salt-marsh vegetation is species-poor. There is little problem in sampling and sorting monospecific stands but, in many cases, a small number of species occur with varying abundance in a wide variety of combinations on salt-marshes. Early accounts of this vegetation (e.g. Tansley 1911, 1939) relied heavily on dominance in an attempt to make sense of such variation, but, as Dalby (1970) noted, this may obscure patterning among less conspicuous species that it is sensible to try and interpret. Furthermore, there has been a tendency in Britain to lump more complex vegetation, less susceptible to analysis, into a ‘general salt-marsh’ community. This term has sometimes been applied in its original, broad sense (Tansley 1911) to vegetation ‘not dominated by any single species, except locally’ and varying ‘from place to place according to local conditions and to the accidents of colonisation by different species’; on other occasions (e.g. Chapman 1934), it has been used to denote a more clearly-defined community.

Second, on many salt-marshes there is a site-related element in the floristic variation among the communities which reflects particular local histories of marsh use or unique combinations of environmental conditions.