Metla Project 3234

The effects of root rot fungi in forest regeneration

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Duration: 1998-2002   Keywords: Armillaria, Heterobasidion annosum, Norway spruce, aspen, birch, coppice, root rot fungi, rotation, tree generation, understory
Research Programme: Forest Regeneration in Southern Finland

Objectives

The aim of the project is to clarify the effect of regeneration method on the transfer of Heterobasidion root rot from the previous to the next spruce generation. Furthermore, the role of admixed tree species in disease spread is investigated.

Results

Occurrence of root rot in planted and advance-growth regenerations of Norway spruce was studied on sites where the previous spruce rotation had been infected by Heterobasidion. The frequency of Heterobasidion infection was higher in advance spruce regenerations compared to planted stands of the same tree size. The average number of regeneration trees infected by Heterobasidion per decayed stump of the previous rotation was 4.5 in the advance regenerations and 1.2 in the planted stands. Among the planted spruces infected by Heterobasidion, at least 71 % were infected through root contacts from the previous spruce generation. The corresponding figure in the advance regenerations was 53 %. Hence, it appears that advance-growth spruces are more susceptible to primary spore infection than planted spruces. The proportion of broadleaf wildings - when occurring scattered in the regeneration - did not affect the disease frequency of young spruces.

Our results suggest that clear cutting followed by planting is better method to regenerate Norway spruce stands infected by Heterobasidion than utilization of advance regeneration established naturally under a spruce overstorey. Because the great majority of planted spruces were infected from old stumps through root contacts, favouring groups of broadleaf trees close to decayed stumps will obviously diminish the losses caused by Heterobasidion in spruce plantations.

Project leader: Piri, Tuula
The Finnish Forest Research Institute, Vantaa Unit, PL 18, FI-01301 VANTAA, FINLAND
Phone: +358 29 532 2453
E-mail: tuula.piri@metla.fi

Other researchers: Hallaksela, Anna-Maija, VA (1998-99), Korhonen, Kari, VA (1998,2001-2002), Lipponen, Katriina, VA (2000)


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Updated 12.06.2012
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