Welsh Journals

THE VEGETATION OF ANTHILLS IN WEST GLAMORGAN SALTMARSHES Q. O. N. KAY and S. R. J. WOODELL INTRODUCTION Although anthills frequently carry well-defined and distinctive plant communities, few studies apart from that of King (1972, 1976) have been made of their plant ecology. King investigated the vegetation of the anthills of Lasius flavus, the common yellow ant of a variety of grassland habitats in Britain and discussed the adaptations of the typical plants of L. flavus mounds in acidic and calcareous grassland. Mounds occupied by L. flavus and the related L. niger also occur, rather surprisingly, in the upper zones of saltmarshes in sites which are regularly submerged by high spring tides and the vegetation of L. flavus mounds in the saltmarsh at Scolt Head in Norfolk has been discussed by Woodell (1974). These anthills were found in the transition zone between saltmarsh and sand-dunes and carried a distinctive vegetation including the Mediterranean dwarf shrub Sea Heath (Frankenia laevis) which was most abundant on the southern and south- eastern faces of the mounds. a Well-developed anthills occur in several saltmarshes in West (^morgan. The results of a survey of the vegetation of these anthills during the summer of 1975 are described below and discussed in relation to the observations of King and Woodell. METHODS Most of the larger anthills were examined at each site. The percentage cover of each plant species was subjectively estimated on each mound and also in a 30 x 30 cm quadrat placed in the surrounding vegetation 1m from the centre of the mound in a direction selected using a table of random numbers (King & Woodell 1975). Soil samples were taken from the top 5cm of soil in each mound and adjacent quadrat. The vegetational data were analysed using two-tailed Wilcoxon signed-ranks tests for matched pairs (Sokal & Rohlf 1969) to determine significant positive or negative associations of plant species with the anthills. The pH, conductivity, and particle size composition of the soil samples were determined by conventional techniques. RESULTS 1. Vegetation The species composition of 38 anthills at five saltmarsh sites in West Glamorgan is summarized and compared with the vegetation of Scolt Head anthills in Table 1. The Whiteford, Pennard and Jersey Marine sites were on sandy saltmarshes near the transition zone to sand dune; the Whiteford and Pennard localities were grazed by ponies but the Jersey Marine area was almost ungrazed. The Llanrhidian and Llwchwr anthills were on silty estuarine saltmarshes several hundred metres from extreme high water mark; the Llanrhidian site was heavily and continuously grazed by sheep and ponies but the Llwchwr area was only lightly and intermittently grazed. The results show that differences between anthill and surrounding