Population ecology of Suillus variegatus in old Swedish Scots pine forests

Spatial characteristics of Suillus variegatus populations, including the size, distribution and number of genets, were measured in four naturally regenerated stands of Scots pine, Pinus sylvestris in Sweden that were more than 100 years old. In the oldest forest, a continuous tree-layer had been present at least since the last forest fire in 1647. Genets were identified based on somatic incompatibility reactions performed on mycelial cultures from sporocarps. In total, 38 genets were identified from 120 tested sporocarps. The maximal extension of a genet, as reflected by its outermost sporocarps, was 27 m in the oldest stand and ranged between 10 and 17 m in the other stands. On average, genet size was 20 m in the oldest stand and 10 m in the other stands. Other genets were not found within the domains of established genets. The closest detected distance between genets was 1.5 m, and the average distance was 4 m. The number of genets ranged between 56 and 74 ha(-1) at the studied sites. Possible reasons for the high degree of resemblance in characteristics in old forests between S. variegatus, the dominant bolete in mature forests, and S. bovinus when present, more a characteristic for younger forests and only scarcely occurring in older forests, are discussed.