Mycobionta of birch and birch stump roots and its possible effect on the infection by Armillaria spp. II.

This paper presents the differences in size and structure of mycobionta communities occurring in soil and on/i n roots of a 30 year-old birch and its stumps 2 years after cutting of the trees. Special attention was paid to the occurrence of Zygorhynchus moelleri and Trichoderma viride. The first species due to the metabolites produced may presumably stimulate the infection by Armlllaria. The second species is a well-known antagonist of Armillaria, Z. moelleri accounted only for 2.6, l.3 and 9.l % of the total number of isolates in rhizoplane as well as in the fine and thick roots of stumps, respectively. Trlchodcrma viride and T. virens were present in roots of Hve birch and its stumps only occasionally. The relatively big population of Mycelium radicis atrovirens- particularly in the fine roots of stumps is attributed to their high vitality and relatively lower level of root decomposition. It seems that the rate of stump root decomposilion does not favour their colonization by Z. moelleri and its supposed contribution in enhancing the infection by Armillaria might not be so distinct as on stumps of 49-year-old birches