Observations on the Lichen Ecology of South Haven Peninsula, Studland Heath, Dorset

Abstract

The greater part of that area of the Isle of Purbeck known as South Haven Peninsula is occupied by a system of sand dunes. The peninsula has been the subject of a physiographical survey by Diver (1933) who, by reference to early maps and charts, was able to trace the development of the dunes since their origin at the beginning of the seventeenth century. The system consists basically of three main ridges running parallel to the eastern shore (Studland Bay). In the northern part the whole system is some 900 yd (825 m) in breadth, and the well-defined ridges are separated by marshy slacks; towards the southern end, however, where the system narrows to about 350 yd (320 m), the pattern becomes less well marked. Each ridge represents approximately 100 years' accretion. The main vascular plant associations have been described by Good (1935). The general succession on the dunes is from dune-grass dominated by Ammophila arenaria to dry Calluina-heath. The succession appears to go hand in hand with increases in acidity and organic content of the soil. The soil changes are described and discussed by Wilson (1960). Except for the work of Brown (1958) on soil fungi, the lower plant vegetation of the area has been neglected. At present attention is confined to the lichens, but it is hoped that the bryophytes may provide the subject of a future paper. One of the most striking features of the lichen vegetation of the dunes, apart from the general richness of its development, is the practically complete change which occurs in its composition from the younger stabilized or semi-stabilized surfaces dominated by Ammophila to the older heath-covered surfaces. The transition closely corresponds positionally to the replacement of Ammophila by Calluina which occurs in general on the landward side of First Ridge (i.e. in the terminology of Diver and Good, the most seaward and recently formed of the three main ridges). An attempt has been made to express the lichen zonation quantitatively by means of quadrat data which have been collected during three visits to the area made at intervals of one year. Quadrats were thrown at random in each of six zones lying on a transect about 50 yd (45 m) wide across the middle and least trampled part of the dune system. Four zones were on First Ridge; the' other two corresponded to the whole breadths of each of Second and Third Ridges. The middle line of the transect across First Ridge is shown in profile in Fig. 1. (The line of section runs approximately along the 'I' in 'FIRST' immediately east of Eastern Lake in th-e map published by both