Reijo Penttilä, Paula Siitonen, Kari Korhonen, Sanna Kannelsuo
Dispersal of a wood-rotting fungus (Phlebia centrifuga), which specialises on old-growth forests and thick spruce logs was studied to develop a model to predict dispersal of species in fragmented forest landscapes. Dispersal and deposition of viable spores was studied in the field in Kuhmo research area and in the wind tunnel of VTT and in the testing laboratory of IVO group.
In the field, wind disseminated spores were captured by agar plates containing haploid mycelia of P. centrifuga. Agar plates were placed at four cardinal points and at different distances (0-256 m) from one fruiting body of the species. In autumn 1997 five separate experiments were conducted, in which the agar plates were kept open for different times (1/2-3 hours). Later on the plates were analysed for an occurrence of diploid mycelia, which indicates that a spore(s) of the studied species had landed and germinated on the plate.
Results from the field experiments indicate that inside an old forest the dispersal of P. centrifuga is strongly concentrated in the neighbourhood of the fungal fruiting bodies. Only in one experiment spores were caught from a longer distance than 100 m from the site of the species and in all other experiments the farthest distance of caught spores was 32 m. According to the preliminary results in IVO laboratory, it seems like dispersal and falling speed of the spores are very sensitive to air temperature and humidity differences. Spores are captured by the wind movement almost like smoke particles.
In 1998 more field experiment will be made to study the dispersal and spore production of P. centrifuga more thoroughly. Emphasis will be put on studies of long-distance dispersal and effect of wind on dispersal. Also the spore production of P. centrifuga will be followed to get information for dispersal modelling, which will be made in co-operation with researchers of the Finnish Meteorological Institute.
|Fig.1. Close distance dispersal of P. centrifuga spores from an isolated site of the species. Filled circles indicate that a viable spore had landed on an agar plate. The experiment was made inside an old forest in 25.9. 1997 and the agar plates were kept open for 1 hour.|
|Fig.2. Large distance dispersal of P. centrifuga spores from an isolated site of the species. Filled circles indicate that a viable spore had landed on an agar plate. The experiment was made inside an old forest in 25.9. 1997 and the agar plates were kept open for 1 hour. A separate occurrence of spore(s) in the east at 256 m can be explained by a tiny unnoticed fruitbody of P. centrifuga in close vicinity to the agar plate.|