POPULATION ECOLOGY OF SUILLUS-VARIEGATUS IN OLD SWEDISH SCOTS PINE FORESTS

Spatial characteristics of Suillus variegatus populations, including t he size, distribution and number of genets, were measured in four natu rally regenerated stands of Scots pine, Pinus sylvestris in Sweden tha t were more than 100 years old. In the oldest forest, a continuous tre e-layer had been present at least since the last forest fire in 1647. Genets were identified based on somatic incompatibility reactions perf ormed on mycelial cultures from sporocarps. In total, 38 genets were i dentified from 120 tested sporocarps. The maximal extension of a genet , as reflected by its outermost sporocarps, was 27 m in the oldest sta nd and ranged between 10 and 17 m in the other stands. On average, gen et size was 20 m in the oldest stand and 10 m in the other stands. Oth er genets were not found within the domains of established genets. The closest detected distance between genets was 1.5 m, and the average d istance 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 resembla nce in characteristics in old forests between S. variegatus, the domin ant bolete in mature forests, and S. bovinus when present, more a char acteristic for younger forests and only scarcely occurring in older fo rests, are discussed.