Epsilon Open Archive

Abstract

Heart rot causes great decrease in timber quality throughout the world. In the conifer forests of Northern Hemisphere the most significant losses are caused by fungi from the Heterobasidion annosum species complex. The spread of the disease is favored by forest management, as the fungus can use freshly cut stumps as an infection court, and so extend through root contacts to infect neighboring trees.

The country-scale inventory revealed that about 22% of Latvian spruce trees contained heart rot, which extended on average 6.6 m within the tree stem; the most commonly associated fungus being H. parviporum. These facts highlight the need to take actions to reduce the level of inoculum in already infested stands. Stump removal and the planting of resistant tree species are two options for that.

Long-term trials carried out in Scandinavia showed that stump removal could significantly decrease the proportion of infected trees in regenerated stands, although the effectiveness of this procedure may eventually decrease with time. In addition, this method is quite drastic and the adverse influence of continuous stump removal on stand biodiversity and productivity should be taken into consideration. The trail conducted in Finland showed that stump removal had a positive impact on seedlings growth, but influenced negatively mycorrhization and species richness.

The other management method which could be employed is the planting of resistant tree species, especially broadleaved trees. In the work undertaken for this thesis heart rot incidence, associated fungi and decay caused yield losses were studied in Latvian grey (Alnus incana) and black alder (A. glutinosa) stands. Despite the high decay incidence and the number of associated fungal species, no single H. annosum s.l. was found. Also, our data showed that the proportion and size of the heart rot column increased with tree age. These data suggest that a short rotation of fast growing broadleaved trees (not only Alnus, but also species of Populus, Betula, and Salix) could be used for clearing up the Heterobasidion inoculum.