Primary resource capture in two sympatric Armillaria species in managed Norway spruce forests

The ability of the preferentially saprotrophic fungus Armillaria cepistipes and the pathogenic A. ostoyae to capture fresh stump resources was investigated in managed Alpine Norway spruce (Picea abies) forests where both species occur sympatrically. The incidence of Armillaria species and genets as rhizomorphs in the soil as well as external and internal (heart rot) stump colonisation were determined in three comparable 1 ha plots. The results indicate that A. cepistipes and A. ostoyae have a very similar strategy to capture fresh stump resources. Both species produce dense networks of rhizomorphs in the soil enveloping living trees. After the felling of the trees, the stumps are rapidly captured through spread of mycelial fans in the cambial zone. Our study suggests that A. ostoyae is slightly more competitive than A. cepistipes in primary resource capture.