Short-term effects of mechanical and biological treatments on Sorbus aucuparia L. sprouting in mesic forests in Finland

Abstract

In reforestation areas in Finland, rowan (Sorbus aucuparia L.) can form dense thickets restricting the growth of commercially more valuable conifers. In this study we compared three different management methods to control excessive growth of rowan. These methods were traditional (mechanical cutting 10–15 cm above ground level), 1 m cut height treatment (saplings were cut 1 m above ground level), and biological control (as traditional method, but freshly cut stumps were squirted with mycelium of a fungus, Chondrostereum purpureum [Pers. ex Fr.] Pouzar). The short-term results one year after the treatments revealed that biological control was the best way to restrict rowan sprouting as the proportion of dead stumps was highest. Furthermore, the number and height of stump sprouts were even two times lower in the biological control than in the mechanical treatments. Although the biological control had the highest number of root suckers, the total number of stump sprouts and root suckers together was indicatively lower than in the other methods (p < 0.10). Based on our results C. purpureum treatment seems promising. Yet, more efficient fungus strains and better methods to spread the fungus on stumps are needed before this method is applicable at commercial scale.

Keywords:

• Chondrostereum purpureum
• reforestation areas
• saplings
• sprout control

Acknowledgements

We thank the forest owners in the municipality of Sipoo, Finnish Forest Research Institute (sites in Lapinjärvi), and the city of Helsinki for permission to use their forests for the study. Jere Eronen, Nea Kuusinen, Asko Harju, Olavi Palosaari, Markku Rantala, and Erkki Piiroinen from Finnish Forest Research Institute helped in treating the study sites. Hannu Rantanen and Juhani Mäkinen helped in measuring sprouts, Juha Heikkinen gave valuable statistical advice and Sisko Salminen modified the figures. The study was funded by the Metsämiesten Säätiö Foundation and Finnish Forest Research Institute.