THE ROLE OF ANT NEST-MOUNDS IN MAINTAINING SMALL-SCALE PATCHINESS IN DRY GRASSLANDS IN CENTRAL GERMANY

Nest-mounds of Lasius flavus. Lasius alienus and Formica rufibarbis ar e mainly on north-facing slopes with a markedly patchy distribution at Gimritz, northwest of Halle (Saale). Nest-mound soils had higher sodi um and potassium levels but lower phosphorus and nitrogen levels than soils away from mounds. Moisture content was lower but soil pH was sig nificantly higher in nest-mound soils. However, there was no differenc e in the relative abundance of plants of alkaline or acid soils growin g on mounds compared to plants off mounds and no significant differenc e between the numbers of nitrophilous plants on and off mounds. Fewer plant species (35 spp.) in total occurred on mounds than off mounds (4 2 spp.). Plant species richness and total plant cover was significantl y less on the nest-mounds than off the mounds. Similarly, the mean num ber of grass (1.39 spp dm(-2)) and forb species (1.13 spp dm(-2)) on m ounds was lower than the mean number of grass (1.99 spp dm(-2)) and fo rb species (1.91 spp dm(-2)) off mounds. Some shrubs and forbs had hig her occurrence and cover on the mounds, although only in Calluna vulga ris, Thymus serpyllum and Cerastium arvense was this difference partic ularly marked. Ant nest-mounds may favour plant species that cannot co mpete with tall grasses on unmanaged, set-aside meadows.