FUNGAL POPULATION AND COMMUNITY DEVELOPMENT IN CUT BEECH LOGS: I. ESTABLISHMENT VIA THE AERIAL CUT SURFACE

More than 450 beech (Fagus sylvatica L.) logs, 10 to 20 cm in diameter and 30 to 40 cm long, were cut from freshly felled trees and placed upright 1 m apart with their bases buried up to 10 cm deep in the ground in a plot of about 600 m² in a mixed deciduous woodland in the Forest of Dean, Gloucestershire, UK. Fungal colonization via the aerial and buried cut surfaces was studied - in some cases following inoculation of basidiospores - using a combination of direct and indirect techniques. A wide variety of ascomycetes, basidiomycetes and fungi imperfecti were identified, by direct observation or following direct incubation of wood samples, from the vicinity of the aerial cut surface within the first six months after cutting. Some such as Coriolus versicolor (L. ex Fr.) Quél. subsequently increased in occurrence, whereas others, including Chondrostereum purpureum (Fr.) Pouz. declined. Isolation onto malt agar from thin sections of wood revealed the presence of some fungi, notably a Fusarium sp., not detected by direct means. In addition, homokaryons of the basidiomycetes Bjerkandera adusta (Willd, ex Fr.) Karst. and C. versicolor were isolated from near the aerial cut surface up to two years after cutting, and, lower down, mostly up until six months after cutting (thereafter heterokaryons predominated). Moreover, evidence was obtained that small volumes of discoloured, but not strongly decayed wood, sometimes contained large numbers of mutually antagonistic individuals (up to 30 per cm³ ) of the decay species B. adusta, C. versicolor and Stereum hirsutum (Willd. ex Fr.) S. F. Gray. Vertical penetration from the aerial cut surface showed a marked lag phase, such that for the first six weeks after cutting, overt colonization was restricted to about 3 mm depth. Thereafter the depth occupied increased rapidly.